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MKB

Permanent Link: http://ufdc.ufl.edu/UFE0021437/00001

Material Information

Title: MKB A New Anesthetic Approach to Feral Cat Sterilization Surgery
Physical Description: 1 online resource (96 p.)
Language: english
Creator: Meyer, Kelly Ann
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: buprenorphine, cat, feral, injectable, ketamine, medetomidine
Veterinary Medicine -- Dissertations, Academic -- UF
Genre: Veterinary Medical Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: A combination of medetomidine (M), ketamine (K), and buprenorphine (B) (MKB) was evaluated as an injectable anesthetic in 240 feral cats undergoing ovariohysterectomy or castration surgery at a high-volume sterilization clinic. A selected dose of MKB (100 micrograms/kg M, 10 mg/kg K, 10 micrograms/kg B) was evaluated for efficacy in a weight-specific manner and was then extrapolated to a fixed dose to be used in all cats, regardless of true weight. The selected dose of MKB provided adequate duration of action, acceptable physiological parameters, and acceptable duration and quality of recovery; however, the fixed dose of MKB was ineffective and unreliable. Cats were not intubated and breathed room air. Hemoglobin oxygen saturatio(SpO2), systolic blood pressure (BP), heart rate (HR), respiratory rate (RR), and rectal temperature were measured and recorded. Atipamezole (A) (5 mg/mL) was administered following the completion of surgery to reverse the effects of medetomidine. The selected dose of MKB (100 micrograms/kg M, 10 mg/kg K, 10 micrograms/kg B) produced rapid onset of lateral recumbency (4.3 ? 4 minutes in males and 5.2 ? 5.6 minutes in females) and adequate duration of surgical anesthesia in both males and females. SpO2 significantly increased over time in both males (R: 36-99 %)(R = range) and females (R: 73-100 %). SpO2 fell below 90% at least once in most cats. Blood pressure (R: 91-195 mm Hg) and heart rate (R: 77-176 beats/minute) in males did not change significantly as a factor of time, however, blood pressure (R: 38-190 mm Hg) and heart rate (R: 57-172 bpm) significantly decreased over time in females. There was no significant change in respiratory rate over time in males (R: 4-76 breaths/minute) or females (R: 4-56 breaths/minute). Rectal temperature significantly decreased throughout the duration of anesthesia in both males and females. Time from medetomidine reversal until sternal recumbency was 38.6 ? 38 minutes in males and 40.6 ? 78.2 minutes in females. Eleven cats (11%) required a second dose of the selected combination of MKB to maintain an adequate plane of surgical anesthesia and this was associated with significantly longer recovery times (62 ? 20.7 minutes in males and 103.8 ? 28.4 minutes in females). The selected dose of MKB was used to calculate a fixed volume to be used in all cats, regardless of true weight. Injection volumes of 0.7 mL and 0.8 mL of MKB were studied and proved to be ineffective at providing adequate anesthesia. There were no perioperative deaths associated with this study. The selected dose of MKB fulfilled many of the demanding requirements associated with feral cat sterilization clinics, however, it was not possible to use a fixed volume, acceptable for use in all cats, regardless of true weight. The selected dose of MKB may be used more effectively in smaller clinics or settings in which it can be dosed in a weight-specific manner.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Kelly Ann Meyer.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Robertson, Sheilah A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021437:00001

Permanent Link: http://ufdc.ufl.edu/UFE0021437/00001

Material Information

Title: MKB A New Anesthetic Approach to Feral Cat Sterilization Surgery
Physical Description: 1 online resource (96 p.)
Language: english
Creator: Meyer, Kelly Ann
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2007

Subjects

Subjects / Keywords: buprenorphine, cat, feral, injectable, ketamine, medetomidine
Veterinary Medicine -- Dissertations, Academic -- UF
Genre: Veterinary Medical Sciences thesis, M.S.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: A combination of medetomidine (M), ketamine (K), and buprenorphine (B) (MKB) was evaluated as an injectable anesthetic in 240 feral cats undergoing ovariohysterectomy or castration surgery at a high-volume sterilization clinic. A selected dose of MKB (100 micrograms/kg M, 10 mg/kg K, 10 micrograms/kg B) was evaluated for efficacy in a weight-specific manner and was then extrapolated to a fixed dose to be used in all cats, regardless of true weight. The selected dose of MKB provided adequate duration of action, acceptable physiological parameters, and acceptable duration and quality of recovery; however, the fixed dose of MKB was ineffective and unreliable. Cats were not intubated and breathed room air. Hemoglobin oxygen saturatio(SpO2), systolic blood pressure (BP), heart rate (HR), respiratory rate (RR), and rectal temperature were measured and recorded. Atipamezole (A) (5 mg/mL) was administered following the completion of surgery to reverse the effects of medetomidine. The selected dose of MKB (100 micrograms/kg M, 10 mg/kg K, 10 micrograms/kg B) produced rapid onset of lateral recumbency (4.3 ? 4 minutes in males and 5.2 ? 5.6 minutes in females) and adequate duration of surgical anesthesia in both males and females. SpO2 significantly increased over time in both males (R: 36-99 %)(R = range) and females (R: 73-100 %). SpO2 fell below 90% at least once in most cats. Blood pressure (R: 91-195 mm Hg) and heart rate (R: 77-176 beats/minute) in males did not change significantly as a factor of time, however, blood pressure (R: 38-190 mm Hg) and heart rate (R: 57-172 bpm) significantly decreased over time in females. There was no significant change in respiratory rate over time in males (R: 4-76 breaths/minute) or females (R: 4-56 breaths/minute). Rectal temperature significantly decreased throughout the duration of anesthesia in both males and females. Time from medetomidine reversal until sternal recumbency was 38.6 ? 38 minutes in males and 40.6 ? 78.2 minutes in females. Eleven cats (11%) required a second dose of the selected combination of MKB to maintain an adequate plane of surgical anesthesia and this was associated with significantly longer recovery times (62 ? 20.7 minutes in males and 103.8 ? 28.4 minutes in females). The selected dose of MKB was used to calculate a fixed volume to be used in all cats, regardless of true weight. Injection volumes of 0.7 mL and 0.8 mL of MKB were studied and proved to be ineffective at providing adequate anesthesia. There were no perioperative deaths associated with this study. The selected dose of MKB fulfilled many of the demanding requirements associated with feral cat sterilization clinics, however, it was not possible to use a fixed volume, acceptable for use in all cats, regardless of true weight. The selected dose of MKB may be used more effectively in smaller clinics or settings in which it can be dosed in a weight-specific manner.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Kelly Ann Meyer.
Thesis: Thesis (M.S.)--University of Florida, 2007.
Local: Adviser: Robertson, Sheilah A.

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2007
System ID: UFE0021437:00001


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MKB: A NEW ANESTHETIC APPROACH TO FERAL CAT STERILIZATION SURGERY


By

KELLY ANN MEYER
















A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE

UNIVERSITY OF FLORIDA


2007

































O 2007 Kelly Ann Meyer









ACKNOWLEDGMENTS

I would like to thank Dr. Sheilah Robertson, Dr. Natalie Isaza, and Dr. Julie Levy for their

unconditional support, their mentoring, and the tremendous opportunities they have offered me

over the course of this study. I would also like to thank my parents for their patience, sincerity,

and motivation in helping me to achieve a finished product. Finally, I would like to thank Justin

for helping me to stay focused and Dr. Joe Hauptman for his instruction and guidance in the

statistical analysis portion of this study.












TABLE OF CONTENTS


page

ACKNOWLEDGMENTS .............. ...............3.....


LIST OF TABLES ............ ....._.. ...............6.....


LIST OF FIGURES .............. ...............7.....


AB S TRAC T ......_ ................. ............_........8


CHAPTER


1 INTRODUCTION ................. ...............10.......... ......


Feral Cat Populations ................. ...............10........... ....
The Problem .............. ... ........... ...............11.......
Public Health Considerations .............. ...............12....
W wildlife Vulnerability .............. ...............13....
Animal W welfare .............. ...............15....
Current Methods of Control ................. ...............15................
Removal Method s............... ............... 16

Trap-Neuter-Return ................. ...............18.......... .....
Non surgical Contraception ................. ............ ...............22.......
Operation Catnip": A Trap-Neuter-Return Program ................. .............. ......... .....23
Challenges of Working with Feral Cats ................. ...............24......__._...
Alpha2-Adrenoceptors .............. ...............28....
M edetomidine ................. ......._._ ... .... ..................2
Medetomidine: Cardiovascular and Respiratory Effects ........._..._... ....._._. ............30
Medetomidine: Side Effects .............. ...............32....

Ati mp amezol e.........___ _........ ._ ._ ...............32...
Atipamezole: Side Effects .............. ...............33....
Dissociative Anesthesia .......................... ......._._. .........3
Ketamine ........._..._...... ...._. .. .... ._.. .......... .......3
Ketamine: Cardiovascular and Respiratory Effects .............. ...............35....
Ketamine: Side Effects .........._.... ......__. ...............36....
Medetomidine and Ketamine Combination.................. ... .. ... .........3
Medetomidine and Ketamine Combination: Cardiovascular and Respiratory Effects ...38
Medetomidine and Ketamine Combination: Side Effects .........._..._. ........_._ .........38
A nal gesia .............. ...............3 8....
NS AID S............... ...............3 8

O pioids .............. ...............39....
Buprenorphine ................... ...............40..
Buprenorphine: Side Effects............... ...............41
Opioid and Alpha2 Agonists ............. ......___ ...............42..
Sum mary ............. ...... ._ ...............42....











2 MATERIALS AND METHODS .............. ...............44....


Animals............... ...............44
Overview ................. ...............44.................
Cat Selection ................. ...............44.................
Anesthetic Drugs .............. ...............45....
Experimental Design .............. ...............45....
Pre-operative Preparation .............. ...............46....
Induction of Anesthesia .............. ... .......__ ........__ ............4

Drug Administration Phase 1: Dose Finding Study .............. ...............47....
Drug Administration Phase 2: Selected Dose Study .............. ...............47....
Drug Administration Phase 3: Fixed Dose Study ......____ ..... ... ._ ..........._....48
Clinical Procedures: Evaluation of Anesthetic Effects ......____ ..... ... ._ ............. ..49
Clinical Procedures: Hemoglobin Oxygen Saturation............... ...............4
Clinical Procedures: Evaluation of Cardiovascular Function ......____ ..... ... .._............49
Clinical Procedures: Evaluation of Respiratory Function .........__ ....... ___ .................50
Clinical Procedures: Temperature .............. ...............50....
Clinical Procedures: Pre-surgical .............. ...............50....
Clinical Procedures: Post-operative ............_ ..... ..__ ...............51...
Quality of Recovery............... ...............5
Data................. ...............51
Statistical Analysis............... ...............51

3 RE SULT S .............. ...............56....


Phase 1-Dose-Finding Study ................... ...............56..
Phase 1-Dose-Finding Study: Side Effects............... ...............57
Phase 2-Selected Dose Study: Animals ........._....._ ...._.._......_. ...... .....5
Phase 2-Selected Dose Study: Time Intervals ....__. ...._.._.._ ......._.... ..........5
Phase 2-Selected Dose Study: Physiological Variables .............. .. ......... ..... ........... 5
Phase 2-Selected Dose Study: Physiological Variables before and after Reversal ................61
Phase 2-Selected Dose Study: Rescue Anesthesia (Isoflurane) .............. ....................6
Phase 2-Selected Dose Study: Quality of Recovery Scores ........._..._.._ ................. ......62
Phase 2-Selected Dose Study: Side Effects ................ ...............63........... ..
Phase 3-Fixed Dose Study (0.7 mL): Animals .............. ...............63....
Phase 3-Fixed Dose Study (0.7 mL): Time Intervals .............. ...............64....
Phase 3-Fixed Dose Study (0.7 mL): Side Effects .............. ...............64....
Phase 3-Fixed Dose Study (0.7 mL): Rescue Anesthesia............... ...............6
Phase 3-Fixed Dose Study (0.8 mL):. ...65...............
Sum m ary ................. ...............66.......... ......

4 DI SCUS SSION ................. ...............75................


LIST OF REFERENCES ................. ...............87........... ....


BIOGRAPHICAL SKETCH .............. ...............96....











LIST OF TABLES

Table page


2-1 Dose-finding study............... ...............54.

2-2 Selected dosing regime .............. ...............54....

2-3 Quality of recovery scores .............. ...............54....

2-4 Fixed dose calculation............... ..............5

2-5 IVKB mixture calculation (20 cats)............... ...............54.

2-6 Atipamezole fixed dose calculation ..........._.__....._.. ....__.. ...........5

3-1 Dose-finding study groups ........._...... ...............67._.._. .....

3-2 Quality of recovery scores .............. ...............67....











LIST OF FIGURES


Figure page

3-1 Blood pressure in male cats over time ................ ...............68..............

3-2 Blood pressure in female cats over time ................ ...............68..............

3-3 Heart rate in male cats over time .............. ...............69....

3-4 Heart rate in female cats over time .............. ...............69....


3-5 SpO2 (%) in male cats over time ................. ...............70..............

3-6 SpO2 (%) in female cats over time ................. ...............70..............

3-7 Respiratory rate in male cats over time ................. ...............71..............

3-8 Respiratory rate in female cats over time .............. ...............71....

3-9 Temperature over time ................. ...............72................

3-10 Blood pressure before and after reversal .............. ...............72....

3-11 Heart rate before and after reversal ................. ...............73........... ..


3-12 SpO2 (%) before and after reversal .............. ...............73....

3-13 Temperature before and after reversal .............. ...............74....









Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science

MKB: A NEW ANESTHETIC APPROACH TO FERAL CAT STERILIZATION SURGERY

By

Kelly Ann Meyer

December 2007

Chair: Sheilah Robertson
Major: Veterinary Medical Sciences

A combination of medetomidine (M), ketamine (K), and buprenorphine (B) (MKB) was

evaluated as an inj ectable anesthetic in 240 feral cats undergoing ovariohysterectomy or

castration surgery at a high-volume sterilization clinic. A selected dose of MKB (100 Cpg/kg M,

10 mg/kg K, 10 Cpg/kg B) was evaluated for efficacy in a weight-specific manner and was then

extrapolated to a fixed dose to be used in all cats, regardless of true weight. The selected dose of

MKB provided adequate duration of action, acceptable physiological parameters, and acceptable

duration and quality of recovery; however, the Eixed dose of MKB was ineffective and

unreliable.

Cats were not intubated and breathed room air. Hemoglobin oxygen saturation (SpO2),

systolic blood pressure (BP), heart rate (HR), respiratory rate (RR), and rectal temperature were

measured and recorded. Atipamezole (A) (5 mg/mL) was administered following the completion

of surgery to reverse the effects of medetomidine. The selected dose of MKB (100 Cpg/kg M, 10

mg/kg K, 10 Cpg/kg B) produced rapid onset of lateral recumbency (4.3 & 4 minutes in males and

5.2 & 5.6 minutes in females) and adequate duration of surgical anesthesia in both males and

females.









SpO2 Signifieantly increased over time in both males (R: 36-99 %) (R = range) and females

(R: 73-100 %). SpO2 fell below 90% at least once in most cats. Blood pressure (R: 91-195 mm

Hg) and heart rate (R: 77-176 beats/minute) in males did not change significantly as a factor of

time, however, blood pressure (R: 38-190 mm Hg) and heart rate (R: 57-172 bpm) significantly

decreased over time in females. There was no significant change in respiratory rate over time in

males (R: 4-76 breaths/minute) or females (R: 4-56 breaths/minute). Rectal temperature

significantly decreased throughout the duration of anesthesia in both males and females. Time

from medetomidine reversal until sternal recumbency was 38.6 & 38 minutes in males and 40.6 &

78.2 minutes in females. Eleven cats (1 1%) required a second dose of the selected combination

of MKB to maintain an adequate plane of surgical anesthesia and this was associated with

significantly longer recovery times (62 & 20.7 minutes in males and 103.8 & 28.4 minutes in

females). The selected dose of MKB was used to calculate a Eixed volume to be used in all cats,

regardless of true weight. Inj section volumes of 0.7 mL and 0.8 mL of MKB were studied and

proved to be ineffective at providing adequate anesthesia. There were no perioperative deaths

associated with this study.

The selected dose of MKB fulfilled many of the demanding requirements associated with

feral cat sterilization clinics, however, it was not possible to use a Eixed volume, acceptable for

use in all cats, regardless of true weight. The selected dose of MKB may be used more

effectively in smaller clinics or settings in which it can be dosed in a weight-specific manner.









CHAPTER 1
INTTRODUCTION

Feral Cat Populations

Feral cats are considered the "wild" offspring of domesticated cats; although a variety of

alternate definitions exist. The classification of these animals is loosely defined and is often

based upon opinion, rather than a universally accepted definition. Socialization status,

recognition of ownership, and overall way life-style are often considered when defining a feral

cat. The lines between loosely owned outdoor cats, tame strays, and feral cats are often blurred

(Levy & Crawford 2004). Lack of consistency in terms of definition is further complicated by

the idea that cats may change classification over time. Owned outdoor cats that wander or

become lost may be considered stray. Stray cats that have lived an extensive amount of time in

the wild may become untrusting of humans and be considered feral. Alternatively, a cat born in

the wild, and deemed feral, may be adopted and over time become an acceptable companion

animal. While the exact definition is undefined, for the purpose of this study, a feral cat is

considered any free roaming cat that does not have a rightful owner, regardless of socialization

status.

While it is impossible to say with certainty, it is estimated that there are between 60 and

100 million feral and abandoned cats in the United States today (Jessup 2004). Cats are often

depicted as independent or anti-social animals; however, feral cats are known to congregate

around a stable food source, forming a colony (Mahlow & Slater 1996; Centonze & Levy 2002).

Feral cat colonies vary in size, but are often dependant upon the availability of food (Mahlow &

Slater 1996). Colonies are generally closed societies with members remaining their entire life;

with replacement coming from births, immigration, and illegal abandonment (Wolski 1982; Levy










et al. 2003). Human caretakers may provide food, a source of shelter, and some veterinary care

(Centonze & Levy 2002).

In one study (Centonze & Levy 2002), 101 caretakers in north central Florida were

surveyed in an effort to characterize 920 feral cats and the people who cared for them. Most

colonies were located on the caretaker' s property and contained less than 10 cats. Most (91%)

caretakers reported caring for their colonies out of sympathy, affection, or a sense of

responsibility for hungry or injured animals. Nearly all caretakers provided a consistent source

of food, while 75% provided shelter and 37% provided or were willing to provide veterinary

care. Most of the caretakers surveyed believed the cats they cared for had an excellent or good

quality of life, and while many were too wild to be handled, they were still considered "like

pets."

The Problem

Feral cat colonies are often a source of controversy as their right to exist is widely debated.

Overpopulation of cats contributes to a variety of problems, resulting in heated arguments

between people in favor of their survival, and those opposing it. While some feel these animals

should be a focus of community efforts to sterilize, vaccinate, and return them to the wild, others

simply feel that eradication is a more definitive solution. This issue is further complicated by the

lack of scientific data demonstrating the most effective control strategy. Discussions about feral

cats are often emotionally charged and perceptions based on personal experiences often

substitute for missing obj ective scientific data (Stoskopf & Nutter 2004).

Although public opinion, attitude, and actions play a predominant role in the number of

unwanted and abandoned animals, a domestic cat's high reproductive capacity creates additional

problems. Free-roaming cats produce an average of 1.4 litters per year and have the potential to

produce up to 3 litters per year (Stoskopf & Nutter 2004). Mean litter size of free-roaming cats










reported in one study was 4. 1 + 1.3 (Stoskopf & Nutter 2004). The overpopulation and prolific

breeding ability of feral cats is of concern regarding public health, impact on wildlife, and animal

welfare.

Public Health Considerations

Although disease carried by feral cats is a concern for public health officials, its zoonotic

impact is unknown. Several unanswered questions include the degree to which infections

circulate within a population; whether or not cats maintain or amplify infection after introduction

from other reservoirs; and whether or not the existence of feral cat populations impact the

likelihood of human exposure to pathogens (Case et al. 2006).

Feral cats may be carriers of infectious diseases transmissible to humans and other

animals. Toxopla~sma gondii, Salmonella tyiphimurium, Escherichia coli, and bacteria from the

genera Rickettsia, Bartonella, and Coxiella; among others, are the causative agents responsible

for numerous infectious diseases found in humans and domestic animals (Patronek 1998; Case et

al. 2006; Dabritz et al. 2006). While the harboring and transmission of these infections by feral

cats is of concern, public health officials are primarily concerned with the potential implications

surrounding rabies.

Rabies is a fatal infectious disease that is transmitted to humans by the bites of infected

animals. Non-bite exposures also exist by means of scratches, abrasions, open wounds, or

mucous membranes exposed to virus-containing saliva or other forms of infected tissue

(Fearneyhough 2001). In the United States, rabies is primarily a disease that affects and is

maintained by wildlife populations (Krebs et al. 2005). Feral cats are of concern because they are

generally unvaccinated and may become infected from contact with wild animals. The fact that

feral cats are commonly regarded as domestic animals may, in itself, pose a serious threat. The

Texas Department of Health reported that rabid domestic animals expose 5 times as many









people to rabies as the average infected wild animal (Clark 1988). Since the middle of the

century, an average of one or two human rabies cases have been reported annually in the United

States (Fearneyhough 2001). Transmission of rabies by wild animals, primarily bats, has

accounted for more than 85% of reported cases in the United States since 1976 (Krebs et al.

1997). In most other countries, dogs remain the maj or species with rabies and the most common

source of rabies transmission to humans (2003). An estimated 40,000 to 100,000 human deaths

result worldwide from rabies (Rupprecht et al. 1995). While the incidence of rabies in free-

roaming cats is not known, an increase in feline rabies cases in the United States, from 183 to

288, was reported in 1988 and 1995, respectively (Eng & Fishbein 1990; Krebs et al. 1996).

During 2005, 49 states and Puerto Rico reported 6,417 cases of rabies in nonhuman animals and

1 case in a human being, representing a 6.2% decrease from the 6,836 cases in nonhuman

animals and 8 cases in human beings reported in 2004 (Blanton et al. 2006).

Wildlife Vulnerability

Whether or not feral cats pose a threat to native wildlife species is an undefined and

controversial issue. The notion that free-roaming cats are detrimental to wildlife populations is

often accepted at face value due to limited studies and lack of definitive scientific proof. The

debate surrounding feral cats and wildlife generally centers on three maj or issues: predatory

behavior of feral cats on native wildlife species, the notion that cats are an introduced species

that should not be allowed to remain in the wild, and the concept that cats are viewed as a

domestic species and it is society's responsibility to keep them confined for their protection, as

well as the protection of other species (Slater 2004).

Much of the evidence that implicates feral cats as the source for extinction or

endangerment of wildlife species come from studies conducted on islands (Girardet et al. 2001;

Veitch 2001; Bester et al. 2002; Nogales et al. 2004; Tantillo 2006). Cats have been introduced









to remote islands off the coasts of New Zealand, Australia, and South Africa where native

wildlife evolved in the absence of predators (Patronek 1998). On many of these islands, cats

were reported to have devastating effects on local species and were even responsible for their

extinction (Veitch 2001). Results from these studies, however, have been inappropriately

extrapolated to the United States, where the impact of feral cats on native wildlife species is not

well documented or understood (Patronek 1998).

Whether or not feline predation is detrimental to wildlife populations remains unclear in

many parts of the world. Few studies accurately report feral cat predation and concisely relate it

to detrimental effects on wildlife (Tantillo 2006). Although studies documenting the negative

impact of feral cats on island ecosystems and their subsequent recovery following the removal of

cat populations exist, many references of cat predation are unsupported by factual data (Coman

& Brunner 1972; Girardet et al. 2001; Veitch 2001; Bester et al. 2002; Nogales et al. 2004;

Tantillo 2006). In one study (Coleman et al. 1997), a previously published "best guess" of the

amount of birds killed by feral cats per year in Wisconsin was later self-cited in another

publication and reported as "research" (Tantillo 2006). Examples such as these often go

unnoticed, are cited by other authors, and are rarely critically evaluated (Tantillo 2006).

The predatory behavior of feral cats has been reported largely based upon casual

observations, perpetuated rumor, and speculation (Bradt 1949). Even if carefully designed to be

representative of the feline population, predation studies that rely on human observation and

reporting are subj ect to a variety of bias (Patronek 1998). Tantillo points out several biases

common to predation studies (Tantillo 2006). Fecal analyses may only highlight the dietary

habits of animals whose excrements are easiest to find. Similarly, stomach contents of deceased

cats may correlate with the manner and/or location of death. For example, cats killed by cars










along roadsides may prey upon roadside species more than a normally distributed population of

cats. Furthermore, few studies address whether or not predatory behavior by feral cats is

considered "additive," adding to a base level of predation and contributing to an increase in

overall mortality; or "compensatory," where cat predation replaces other forms of mortality and

merely compensates for mortality that would happen anyway (Tantillo 2006).

The uncertainty surrounding the impact or lack thereof, of feral cat populations on native

wildlife species is cause for concern for wildlife conservationists, ecologists, researchers, and

feral cat activists. Although further evidence is needed to more clearly define the ambiguity and

bias surrounding wildlife vulnerability, the topic remains an unresolved issue.

Animal Welfare

Feral cats are frequently considered a nuisance to society as they often exhibit noisy

courting and territorial behavior, fecundity, and urine spraying by males. Despite these

misgivings, a general concern for their welfare and way of life is recognized (Zaunbrecher &

Smith 1993). High neonatal and juvenile mortality rates are reported for feral cats (Nutter et al.

2004). In one study, colony-based observations found a kitten mortality rate of 48% three months

following the initiation of the study, which contributed to a 75% cumulative kitten mortality rate

at 6 months (Stoskopf & Nutter 2004). Kitten death was highly dependent upon environmental

factors, but trauma accounted for most deaths in which cause could be confirmed (Nutter et al.

2004). In addition, feral cats, like wildlife, are susceptible to every day threats including dogs,

cars, humans, disease, starvation, and climate. The potential for suffering is a cause for concern

and warrants a solution to end overpopulation and its negative effects on the welfare of feral cats.

Current Methods of Control

A variety of population control methods have been tried and are ongoing, however, none

have proved to be the most obvious choice. Two management schemes, removal and trap-neuter-









return (TNR), are strategies recognized in the attempt to control feral cat populations. Traditional

animal control, or capture and removal, is often limited by resources and is rarely successful in

extensive cat populations (Andersen et al. 2004). The population management technique of trap-

neuter-return focuses on decreasing feral cat populations through sterilization as an alternative to

conventional removal methods.

Removal Methods

Eradication in situ, removal for culling off-site, transferring to sanctuaries, and adoption

are all examples of removal strategies employed in the quest to eliminate feral cat populations.

Due to the magnitude of feral cat overpopulation, an effective control program must integrate

environmental safety, affordability, sustainability, and public aesthetics (Levy & Crawford 2004)

Lethal eradication methods can be effective; however, they often present logistical barriers

that compromise environmental safety and put non-target animals at risk (Veitch 2001; Bester et

al. 2002). In addition, opposition is common as such removal techniques are often found

unacceptable by the general public (Levy & Crawford 2004). Introduction of disease, poison, and

hunting are examples of lethal eradication strategies. A combination of such tactics has been

employed on at least 48 islands with the first successful campaign taking place on Stephens

Island, New Zealand, in 1925 (Nogales et al. 2004). The maj ority of islands (75%, n=36) where

eradication has been successful are less than 5 km2 (NOgales et al. 2004). Therefore, these results

cannot be appropriately extrapolated to larger islands and other mainland parts of the world

where lethal eradication strategies may be considered.

Trapping efforts are generally orchestrated near or at colony sites where cats are humanely

captured. Cats considered feral, sick, or injured may be culled, whereas socialized cats and

kittens may be put up for adoption. While this appears to be the ideal solution, two problems

exist within this strategy. Feral cats are naturally wary of unusual conditions in their environment









and may be reluctant to enter traps even if they are baited (Nutter et al. 2004). Therefore, total

elimination is usually unsuccessful as several colony inhabitants will likely evade capture and

ultimately repopulate the area (Mahlow & Slater 1996). Feral cats are territorial animals and

their highest potential for population increase occurs when populations are low (Foley et al.

2005). This repopulation will likely attract immigrant cats and together they will breed to fulfill

whatever the environmental niche can support. Cat population size tends to increase until a

carrying capacity is reached (Foley et al. 2005).

While adoption is often considered the ideal outcome, an additional problem arises because

there are simply not enough homes for the number of cats that need them. A proposed alternative

to adoption is the creation of cat sanctuaries. Sanctuaries are refuges for homeless cats that serve

as permanent homes where they are provided for, however, many of these facilities fill to

maximum capacity almost immediately after opening (Levy & Crawford 2004). Additionally,

sanctuary cats are not guaranteed proper care nor are they ensured a good quality of life (Slater

2004).

The effectiveness of removal methods rely on a variety of factors that often limit the

success of a particular strategy. Public opposition and environmental safety concerns prevent

eradication from becoming a feasible option in regard to population disposal. Similarly, removal

by culling and adoption alone has proven to be ineffective and inadequate (Neville & Remfry

1984; Mahlow & Slater 1996; Levy & Crawford 2004). It has been shown that partially

successful removal of feral cats produces a vacuum phenomenon in which population dynamics

and territorial behavior encourage new animals to move into an unoccupied area (Zaunbrecher &

Smith 1993; Patronek 1998; Gibson et al. 2002). Alternative strategies continue to be explored

with the goal of reducing the problem of feral cat overpopulation.










Trap-Neuter-Return

The newest approach in feral cat population management is trap-neuter-return (TNR). The

concept of TNR was introduced in Denmark and England in the 1970's and has spread in recent

decades to the United States. Trap-neuter-return programs generally focus on unowned cats,

being fed by caretakers, and are often considered more acceptable to the public than trap and

destroy methods (Mahlow & Slater 1996). TNR involves trapping, sterilizing, and then returning

feral cats to their initial capture site. Some TNR programs offer additional amenities including

vaccination, parasite control, retroviral testing, and treatment of injury or illness. The primary

goal of TNR programs is to reduce populations of feral cats, and therefore, their impact on

society.

The long term goal of TNR is often extinction of a colony through natural attrition. The

deaths of sterilized animals will ultimately result in a slow total population decline. A three-

tiered approach of incorporating euthanasia of sick or injured animals, adoption of socialized

cats, and TNR is considered to be most effective (Levy & Crawford 2004). TNR programs serve

to prevent the birth of new litters, reduce the threat of feline and zoonotic diseases through

vaccination, and improve the quality of life for homeless cats (Foley et al. 2005). Most feral

populations are at a capacity for available resources (Gibson et al. 2002). Reducing the birth rate

decreases the competition for food and shelter, therefore increasing survivability. In addition,

animal stress is reduced with less fighting and competition for mates (Gibson et al. 2002).

There is a disagreement among veterinarians and members of animal protection groups

about whether TNR programs should be discouraged, tolerated, or encouraged (Patronek 1998).

While most advocates of TNR recognize its limitations, opposition arguments include mainstay

topics such as concerns over zoonotic diseases, wildlife vulnerability, hidden costs of performing

surgery, and the questionable quality of life following release. Additionally, the question arises









that if these animals are indeed considered wild, why should they be treated any differently than

other wild animals (Mahlow & Slater 1996)? Evidence that TNR is an effective method for

controlling cat populations is scarce (Zaunbrecher & Smith 1993; Levy et al. 2003). The concept

of TNR has contributed to a decline in population over time when compared to control colonies

in which cats are not neutered (Stoskopf & Nutter 2004). Several studies deliver varying results,

illustrating both the potential benefits and limitations associated with TNR (Levy et al. 2003;

Stoskopf & Nutter 2004; Natoli et al. 2006).

One limitation associated with TNR is the time necessary for results to become evident. In

Rome, Italy, 8000 cats were neutered over the span of 10 years and reintroduced into their

colonies (Natoli et al. 2006). While a significant decrease in overall population was observed

(16-32%), it was not noted until at least 3 years from the time of neutering. While a decrease was

observed, it was indicated that the results were not as great as originally hoped for. Immigration

due to abandonment and spontaneous arrivals were found to be 21% in this study, offsetting the

decrease from sterilization, and it was concluded that without proper education on

overpopulation and abandonment.

Similar to the findings of Natoli and Maragliano, new arrivals as a result of illegal

abandonment may hinder the success of a TNR program. One study revealed that the presence of

highly visible, well-fed, established feral colonies encouraged illegal desertion of pet cats

(Castillo & Clarke 2003). While TNR was shown to decrease the original population, the

population at the end of the study was observed to increase as a result of illegal abandonment.

This phenomenon is thought to be the result of cat owners' desperate attempts to "give the cat a

chance," as opposed to relinquishment to an animal shelter, where high rates of euthanasia exist

(Levy & Crawford 2004).









Conversely, the effects of TNR have also been shown to substantially reduce populations

of feral cats. In Randolph County, North Carolina, USA, a study used 9 managed colonies to

assess reproductive parameters in feral cats (Stoskopf & Nutter 2004). Of the 9 colonies, 6

participated in a TNR program. The remaining 3 colonies did not participate in a TNR program

and were used as control groups. Of the surgically sterilized colonies, all 6 decreased in

population (mean decrease of 36%) and continued to decline within the first 2 years. In the same

2 years, the remaining 3 control colonies, which were not sterilized, were found to increase in

number by 47%. The study concluded that TNR may bring feral colonies to extinction, but is not

a rapid solution.

Similarly, an 11i-year study at the University of Central Florida (USA) found TNR to be

highly successful at reducing the number of feral cats amongst several populations (Levy et al.

2003). Between 1991 and 1995 an original group of 155 study cats were sterilized, with the

exception of 1 male cat. While records were not kept prior to 1991, observers estimated the cat

population on campus may have reached 120 cats. Sterilization and adoption of socialized cats

reduced the population to 68 by 1996 and only 23 cats remained on campus at the end of the

study in 2003, representing a 66% reduction. Additionally, no known kittens were observed to be

born on campus after 1995. The study concluded that long-term reduction of feral cat

populations is feasible by TNR.

A separate study in north central Florida (USA) distributed a written survey to feral colony

caretakers who participated in a local TNR Program (Centonze & Levy 2002). The survey

reported 132 colonies being cared for with a total of 920 cats. At the time of the completed

survey, caretakers had participated in monthly sterilization clinics for 1 to 9 months. Most

colonies contained less than 10 cats with the largest colony containing 89 cats. The mean colony









size before participation in monthly sterilization clinics was 7 cats. The mean colony size

following participation in a TNR program was 5.1 cats. Within less than one year of TNR

participation, average colony size decreased by 27%, while the largest colony was observed to

decrease in numbers from 89 to 24 cats. In conclusion, implementation of TNR was determined

to decrease colony size and the number of cats overall, from 920 to 678, as a result of death,

disappearance, adoption, and the prevention of new births.

In addition to halting reproduction, TNR has also been reported to offer additional benefits.

One study reported improved body condition of feral cats 1 year after sterilization surgery (Scott

et al. 2002). Body weight, body condition scoring (BCS), and falciform fat pad measurements

were used to determine changes in feral cat body conditions before and after sterilization.

Reported scores indicated more than half of feral cats were less than the ideal weight prior to

surgery. Cats were found to increase in mean body weight by 40% and scored 1 point higher on

the BCS scale (1-9) 1 year following participation in a TNR program. In addition, caretakers

reported a decreased tendency to roam following neutering. Fighting amongst cats was also

observed to decrease following sterilization.

The Gillis W. Long Hansen's Disease Center, a federal research facility and hospital

located in Carville, Louisiana, USA, was the site of a well-established feral colony (Zaunbrecher

& Smith 1993). In response to noise and odor complaints by hospital residents and staff, trap and

removal methods were employed without success. A TNR study was designed and initiated. The

colony was regarded as a nuisance prior to the study and implementation of TNR. After the

initiation of the TNR program, not only was the population found to stabilize, but overall health

and body condition was found to improve and complaints about territorial behavior and noise

decreased. The overall attitude toward the feral cats had also changed. After participation in the










TNR program, cats attained a certain amount of status evoking a protective and possessive

behavior from both patients and staff. The TNR program also incorporated the participation of

several hospital patients that hand-delivered 18 cats to partake in the study, indicating support

and endorsement for the proj ect. Patients and staff soon regarded the feral cats as pets. TNR was

determined to be effective, economically feasible, and a humane solution to the once negative

attitude towards the colony. In this particular example, not only did colony health improve, but

the overall attitude and approach to the colony was increasingly positive.

While it may not embody the gold standard for pet cats, TNR offers an alternative way of

life for feral cats. TNR programs offer the opportunity for feral cats to live a good quality of life

for an extended period of time as their population is diminished by way of adoption, natural

attrition, and the prevention of new births.

Nonsurgical Contraception

Alternatives to surgical sterilization programs, using pharmacaceutical or immunological

methods, are currently under investigation for use in feral cats. One example of non-surgical

contraception is chemical castration, in which intratesticular or intraepididymal inj sections of a

chemical agent (4.5 % solution of chlorhexidine digluconate) are used to cause infertility in

males (Kutzler & Wood 2006). Similarly in females, mechanical barriers, such as intravaginal

and intrauterine devices, can be implanted to disrupt fertility. (Kutzler & Wood 2006).

Additionally, hormonal treatments, including progestins, androgens, or analogs of gonadotropin

releasing hormone (GnRH) act either directly or indirectly to block reproductive hormone-

mediated events and conception (Kutzler & Wood 2006).

Recently, the concept of immunocontraception has been investigated for a nonlethal and

nonsurgical approach to controlling feral cat populations (Levy et al. 2004; Kutzler & Wood

2006; Purswell & Kolster 2006). Immunocontraception, via vaccination against GnRH, uses the









immune system to block fertility (Purswell & Kolster 2006). While immunocontraception is

promising, there are also some drawbacks. In addition to finding the most appropriate antigen for

a vaccine, appropriate delivery systems have proven to be a challenge. Oral vaccine baits raise

the concern for non-target species and the implications of introducing a widely distributed oral

contraceptive vaccine into the environment (Purswell & Kolster 2006). Additionally, animals

generally require a series of immunizations for adequate immunity, some of which fail to

respond and remain fertile (Levy et al. 2004). In order to be considered effective,

immunocontraception vaccines for feral cats require long-term immunity for a large population,

achieved with a single treatment, eliminating the need for repeat vaccines (Purswell & Kolster

2006).

While progress continues to be made, the development of non-surgical contraceptive

strategies are complex and slow. Therefore, the use of surgical sterilization and TNR programs

must be retained, at least for the present time, to control feral cat populations.

Operation Catnipo: A Trap-Neuter-Return Program

Operation Catnip" is a non-profit organization that holds monthly feral cat sterilization

clinics at the University of Florida' s College of Veterinary Medicine. Cats are presented the

morning of each clinic confined in humane, wire mesh traps. Upon arrival, cats are assigned an

identification number. After being anesthetized, cats encounter a series of stations in preparation

for surgery. Eyes are lubricated, bladders are expressed, inj ectable antibiotics are administered,

and appropriate surgery site preparation is performed. After sterilization is complete, all cats are

vaccinated against feline rabies, feline leukemia virus, feline panleukopenia virus, herpes virus,

and calicivirus. In addition, they receive topical treatment with selamectin for parasite control.

The tip of the left ear is removed to permanently identify sterilized cats.









Operation Catnip" is considered a high-volume sterilization clinic, averaging between 100

and 200 surgeries at each monthly clinic. The largest clinic to date sterilized 230 feline

participants. Each clinic is completed in a matter of hours and is comprised solely of volunteers,

students, clinicians, and surgeons. In 2006, Operation Catnip sterilized 3,725 feral cats (Scott

2007).

Challenges of Working with Feral Cats

The challenges associated with feral cats include a variety of obstacles in regards to their

capture and sterilization. Trapping is relatively easy and requires little to no training in order to

safely transport and present feral cats for sterilization; however, some feral cats may evade

trapping attempts. Providing an acclimation period to traps prior to capture may prove beneficial

to colonies not used to human contact or particularly "trap-shy" cats. Additional methods are

available, but are not practical as they require experience or the participation of a veterinarian; an

example being net capture or sedative-laced food (Nutter et al. 2004).

Once trapped, feral cats present a unique problem because these animals, similar to

wildlife, cannot be safely handled while conscious. Therefore, feral cats must be anesthetized

within their traps. Anesthesia presents additional challenges in regard to administration. Feral

cats are usually of unknown weight, age, and health status, which are influential in choosing any

anesthetic regime. Similarly, unknown factors such as injury or illness may influence or even

compromise the safety of anesthesia. An anesthetic protocol to be used in feral cats must

consider the safety of both the handlers and the animals.

Properties of an Ideal Anesthetic

Inj ectable anesthetics permit immobilization while cats are confined within their traps,

eliminating the potential for escape or contact with conscious animals that may prove to be

dangerous. Intramuscular inj sections are the most efficient route of administration when









anesthetizing feral cats. An ideal anesthetic regime to be used in feral cats would be predictable,

reliable, and offer a wide margin of safety. It would be suitable for both males and females of

any age and physical condition. In addition, it would provide rapid onset, sufficient duration of

surgical anesthesia, rapid return to normal function, and adequate post-operative analgesia.

Inj ectable anesthesia for use in feral cats also requires consideration of the inj section

volume. Ensuring a complete and accurate inj section for feral cats restrained within their traps is

difficult because restraining options are limited and often inefficient. Large drug volumes pose

the risk of incomplete administration because cats may move upon inj section. A small volume

increases the likelihood for complete administration.

Feral Cat Anesthesia: Shortcomings of Current Methods

The current anesthetic protocol used in Operation Catnip" is an inj ectable combination of

tiletamine, zolazepam, ketamine, and xylazine (TKX) given intramuscularly. TKX is considered

an acceptable inj ectable anesthetic for use in feral cat sterilization and importantly, is associated

with a low (0.35%) perioperative mortality rate (Williams et al. 2002). However, TKX possesses

several limitations that have prompted the search for an alternative inj ectable anesthetic.

Shortcomings include oxygen saturation levels that are below accepted values, prolonged

recovery times, postoperative hypothermia, and likely inadequate post-operative analgesia

(Cistola et al. 2004).

Tiletamine is a dissociative anesthetic, chemically related to ketamine. It provides

analgesia and immobilization in a dose-dependent manner (Lin et al. 1993). Zolazepam is a

benzodiazepine and provides muscle relaxation (Lin et al. 1993). Tiletamine and zolazepam are

combined in a 1:1 ratio by mass and marketed under the trade name, Telazol" (Fort Dodge

Animal Health, Fort Dodge, IO, USA) (Lin et al. 1993). Telazol" 'is not considered a good









combination for maintenance of anesthesia beyond its initial dose, as recoveries may be

prolonged and the actions of zolazepam may outlast those of tiletamine (Pascoe 1992). This is a

problem because the animal experiences a greater degree of tranquilization than anesthesia

during recovery (Plumb 2005). Xylazine is used as a sedative analgesic and also provides good

muscle relaxation and is approved for use in the dog and cat in the United States. Xylazine may

cause significant cardiovascular depressant effects (Paddleford & Harvey 1999).

At the same inspired oxygen concentration, there is a tendency for arterial oxygen tensions

to be less during general anesthesia than observed while conscious (McDonell 1996).

Hemoglobin oxygen saturation (SpO2) > 95% is considered normal and SpO2 < 90% (defined as

a PaO2 Of < 60 mmHg) equates to serious hypoxemia (Thurmon et al. 1996). In cats anesthetized

with TKX, SpO2 leVOIS averaged 92 & 3% in males and 90 & 4% in females (Cistola et al. 2004).

SpO2 leVOIS were also found to drop below 90% at least once in most cats (Cistola et al. 2004).

TKX does not require animals to be intubated and room air (Fi = 0.21) is inspired. This is likely

a contributing factor to low oxygen saturation levels seen in cats anesthetized with TKX. While

low oxygen saturation is easily preventable and treatable, it is not feasible to administer

supplemental oxygen to all cats participating in Operation Catnip" because equipment is limited

and up to 50 cats may be anesthetized at one time. The exact repercussions of low SpO2 leVOIS in

cats anesthetized with TKX are unknown, but prompt the search for alternative methods of

anesthesia.

Prolonged recoveries are often seen with the use of TKX in cats. The sedative effects of

xylazine last 1-2 hours, but complete recovery may take 2-4 hours (Paddleford & Harvey 1999).

After surgery is complete, the effects of xylazine may be reversed using one of its antagonists,

yohimbine. However, the time from reversal to sternal recumbency has been reported to be










prolonged (72 & 42 minutes) in cats anesthetized with TKX (Cistola et al. 2004). The low

specificity of yohimbine as an antagonist to xylazine may contribute to prolonged recovery times

(Virtanen et al. 1989).

One side effect of Telazol is hypothermia (Plumb 2005). Normal body temperature for cats

ranges from 37.8-39.5oC (100-103.1oF) (Plumb 2005). Cats administered TKX were reported to

be hypothermic with temperatures dropping as low as 36.6 & 0.80C (97.8 & 1.4oF) post-

operatively (Cistola et al. 2004). Clinical hypothermia is associated with decreased liver and

renal blood flow, resulting in reduced liver metabolism and renal excretion (Posner 2007).

Subsequently, hypothermia-induced slowed metabolism of anesthetic drugs may account for

prolonged recovery times seen in cats anesthetized with TKX. Another complication resulting

from hypothermia is CNS depression, which may potentiate the effects of anesthetics and muscle

relaxants (Short 1987). Additionally, hypothermic animals often shiver during recovery,

increasing their metabolic requirements for oxygen. In humans, shivering in recovery is reported

to be unpleasant (Kumar et al. 2005).

Feline post-operative pain has been under treated largely as a result of fear of side effects

and lack of suitable pharmaceutical products (Robertson & Taylor 2004). It has been reported

that cats undergoing ovariohysterectomy that are not provided with analgesics have more post-

operative pain than cats that receive analgesics (Slingsby et al. 1998). While xylazine and

ketamine may offer analgesic properties, TKX does not contain a recognized analgesic and

therefore, post-operative pain control is likely inadequate. Due to the inadequacies surrounding

TKX, alternative anesthetic regimes are desired.










Proposed Drug Combination

A combination of medetomidine, ketamine, and buprenorphine (MKB) has been proposed

for use in feral cat sterilization surgery. Similar to TKX, this combination of drugs is combined

and administered intramuscularly as a single injection. Medetomidine and its specific antagonist,

atipamezole, are highly specific for alpha adrenoceptors. Ketamine is classified as a dissociative

anesthetic, offering a state of unconsciousness and somatic analgesia. Buprenorphine is an opioid

analgesic used in pain management. It is hypothesized that the MKB combination may eliminate

some of the inadequacies associated with TKX.

Alpha2-Adrenoceptors

Adrenergic drugs affect receptors stimulated by norepinephrine or epinephrine. These

drugs can act directly on the receptor (adrenoceptor or adrenoreceptor) by activating it, blocking

neurotransmitter actions, or interrupting the release of norepinephrine. Norepinephrine releasing

neurons are found in the central and sympathetic nervous system where they serve as links

between ganglia and effector organs (Howland & Mycek 2000).

Adrenoceptors can be distinguished pharmacologically and are divided into two families,

alpha (a) and beta (P). Alpha adrenoceptors are further subdivided into several classes, including

alpha and alpha, based on relative affinities for agonists, independent of their anatomical

location (Berthelsen & Pettinger 1977; Wickberg 1978; Wikberg 1978). Alpha2-adrenoceptors

have been isolated in the central nervous system, gastrointestinal tract, uterus, kidney, and

platelets and produce a variety of effects (Paddleford & Harvey 1999). Pharmacologic studies

have revealed alpha2-adrenoceptors to be located in either pre-synaptic or post-synaptic positions

(Cullen 1996). Alpha2-adrenoceptors located in the central nervous system regulate the neuronal

release of norepinephrine and several other neurotransmitters that are intimately involved in the

modulation of sympathetic outflow, cardiovascular and endocrine function, vigilance, emotion,










cognition, and nociception (Scheinin & MacDonald 1989). In most cell types, but not all,

alpha2-adrenoceptors regulate adenylate cyclase activity. Specifically, they are linked to a

guanine nucleotide regulatory protein (G-protein), whereby receptor activation results in

inhibition of adenylate cyclase activity and cAMP formation in target cells (Fain & Garcia-Sainz

1980). This leads to the inhibition of further release of norepinephrine from the neuron. When a

sympathetic adrenergic nerve is stimulated, released norepinephrine crosses the synaptic cleft,

interacting with alpha receptors. A portion of the released norepinephrine "circles back" and

reacts with alpha receptors on the neuronal membrane. The stimulation of the alpha receptor

results in feedback inhibition for continued norepinephrine release from the stimulated

adrenergic neuron. This inhibitory action decreases further output of the neuron and serves to

reduce sympathetic output when sympathetic activity is high (Howland & Mycek 2000).

Adrenoceptors are a natural target for the development of sedatives and anesthetics because their

activation leads to reduced norepinephrine release and locus coeruleus activity, a site in the brain

containing many norepinephrine releasing neurons (Stenberg et al. 1993). Norepinephrine is a

neurotransmitter required for a variety of physiological effects and is necessary for the mediation

of arousal and pain (Paddleford & Harvey 1999). If norepinephrine is blocked, the result is

sedation and analgesia (Paddleford & Harvey 1999). Activation of alpha2-adrenoceptors by

specific agonists offer profound sedative-anesthetic effects in a variety of species (Scheinin et al.

1987).

Medetomidine

Medetomidine is one of the newer sedative drugs approved for veterinary use. It is

classified as an adrenergic alpha2-agOnist (Cullen 1996). Intended for use in dogs and cats, it

provides predictable and dose-dependant sedation and analgesia, mediated by receptor

stimulation in the spinal cord and brain (Cullen 1996). Medetomidine is lipophilic and rapidly









eliminated (Paddleford & Harvey 1999). Its alpha to alpha receptor selectivity binding ratio is

1620, compared to 160 for xylazine (Virtanen 1989). Alpha2 agOnist drugs bind to alpha2-

adrenoceptors, altering their natural membranes and preventing the release of neurotransmitters

(Paddleford & Harvey 1999). Medetomidine induces sedation and analgesia, and in high doses,

has anesthetic properties (Savola et al. 1986; Virtanen et al. 1988). It has been shown to induce

change in metabolites of various transmitters resulting in their decreased release, metabolism,

and turnover (Virtanen et al. 1988).

A clinical evaluation by seven veterinary clinics in Finland determined the recommended

dose of medetomidine to be between 50-150 Clg/kg for various clinical procedures in cats in

which sedation was needed (Vaha-Vahe 1989a). Doses ranging between 80 and 110 Clg/kg were

used for examinations, clinical procedures, and minor surgical operations in cats (Vaha-Vahe

1989a). The preferred route of administration was intramuscular inj section (Vaha-Vahe 1989b;

Vaha-Vahe 1989a). Cats administered 10 Clg/kg of medetomidine show stupor-like sedation with

loss of reflexes (Stenberg et al. 1993). Sedation for up to 90 minutes and analgesia for 20-50

minutes is reported with 80 Clg/kg (Vaha-Vahe 1990). Medetomidine has been shown to reduce

dose requirements for other anesthetics in animals when used concomitantly (Segal et al. 1988).

An advantage of medetomidine is that the sedative and depressant effects associated with it can

be fully and rapidly reversed with its specific antagonist, atipamezole.

Medetomidine: Cardiovascular and Respiratory Effects

Medetomidine produces marked changes in the cardiovascular system, mostly through

stimulation of central receptors, increasing vagal tone and decreasing sympathetic activity,

resulting in bradycardia and hypotension (Cullen 1996). The autonomic nervous system, under

control by the central nervous system, is the principal means by which heart rate is controlled

(Berne et al. 2004). Drug lipophilicity is a maj or determinant of the rate of diffusion across









biological membranes (Gaynor & Muir 2002). Medetomidine is highly lipophilic and therefore,

its ease of penetration into the central nervous system is reflected by its rapid onset of

cardiovascular effects (Savola 1989). After medetomidine administration, peripheral vascular

resistance increases due to alpha adrenoceptor-mediated events (Paddleford & Harvey 1999).

Stimulation of postsynaptic receptors located in venous and arterial walls results in

vasoconstriction, whereas stimulation of presynaptic receptors inhibits norepinephrine release,

reducing sympathetic tone, and contributing to bradycardia (Ruffolo 1985). In cats,

medetomidine induces a biphasic effect on blood pressure by increasing it transiently before a

decrease to pre-inj section control values or less is seen. Heart rate decreases immediately

following inj section (Savola et al. 1986; Savola 1989). Prior administration of atropine did not

eliminate the hypotensive or bradycardic actions associated with medetomidine, nor was it found

to modify the initial hypertensive phase (Savola 1989). Medetomidine consistently produces

marked bradycardia in cats and heart rate may decrease by as much as 50% of pre-injection

values (Vaha-Vahe 1989b; Vaha-Vahe 1989a; Cullen 1996). Cats administered 20 Clg/kg of

medetomidine IM showed a 58% decrease in heart rate from baseline values 15 minutes

following administration (Lamont et al. 2001). Medetomidine-induced changes in heart rate are

primarily due to centrally mediated effects and peripheral receptor stimulation; there is no

evidence for a direct action of alpha agOnists on heart muscle (Day & Muir 1993).

Medetomidine has been reported to cause a decrease in arterial PaO2 in cats (Duke et al.

1994). Venous desaturation also occurs and is likely the result of increased tissue oxygen

extraction associated with decreased cardiac output (Gaynor & Muir 2002). Medetomidine

depresses the respiratory center, decreasing sensitivity to increases in PaCO2 (Muir et al. 2000).









When large doses of medetomidine are administered, the respiratory threshold for PaCO2 ValUeS

increase, resulting in marked respiratory depression (Muir et al. 2000).

Medetomidine: Side Effects

The other most common adverse effects observed clinically with the use of medetomidine

are vomiting, muscle twitching, and hypothermia (Cullen 1996). In one study of 678 cats, 65%

vomited after IM administration of medetomidine, using doses ranging between 80-100 Clg/kg

(Vaha-Vahe 1989b). In addition, pale mucous membranes are often witnessed as a result of

medetomidine's profound vasoconstrictive effects (Muir et al. 2000). Inhibition of gastric

secretions have also been reported with the use of medetomidine (Cullen 1996).

Atimpamezole

A major advantage of the use of alpha agOnists, like medetomidine, is that specific

antagonists have been developed to fully reverse their physiological effects. Atipamezole is a

potent alpha antagonist and is the most selective drug currently available for clinical use in

veterinary anesthesia (Paddleford & Harvey 1999). Its alpha to alpha receptor specificity is

8526, compared to 40 for yohimbine, and it has virtually no effect on other receptors (Virtanen et

al. 1989). Atimpamezole has been shown to effectively antagonize the cardiovascular,

respiratory, gastrointestinal, and hypothermic effects of medetomidine (Savola 1989; Cullen

1996). In one study, mean arterial pressure and heart rate values were completely restored

following administration of atipamezole during maximal hypotensive and bradycardic phases

induced by medetomidine (Savola 1989). In dogs, a transient decrease in mean arterial pressure

of between 8% and 20% was found after intramuscular inj section of atipamezole (Vainio 1990).

In cats, the most effective dose of atipamezole was found to be 2-4 times (on a mg basis)

the medetomidine dose administered IM (Cullen 1996). Atipamezole can be administered

intravenously, intramuscularly, or subcutaneously and its half-life is twice that of medetomidine,









minimizing the risk for sedation relapse after atipamezole administration (Paddleford & Harvey

1999; Bollen & Saxtorph 2006). Atipamezole reverses the undesirable depressant effects of

medetomidine and is useful for rapidly returning animals to normal function.

Atipamezole: Side Effects

Adverse effects accompanying atipamezole reversal of medetomidine include urination,

salivation, and muscle tremors (Vaha-Vahe 1990). Extremely high doses may induce signs of

CNS stimulation, extreme excitement, panting, and vomiting (Paddleford & Harvey 1999).

Following IV administration, tachycardia and hypotension have occurred and therefore slow IV

or IM administration is recommended (Paddleford & Harvey 1999).

Dissociative Anesthesia

Dissociative anesthesia derives its name from its unique ability to simultaneously depress

one area of the central nervous system, while stimulating another (Evans et al. 1972).

Dissociative anesthetics produce unique effects in which animals are assumed to feel dissociated,

or apart, from their body (Bill 2006). It is this effect that allows dissociative drugs to provide

analgesia and anesthesia without disrupting vital physiological functions (Evans et al. 1972). One

advantage to using dissociative anesthesia in cats is that their airway remains patent, eliminating

the need for endotracheal intubation (Beck et al. 1971). Dissociative anesthesia differs further

from other anesthetics in that its use often results in emergence reactions and hallucinatory

behavior, unlike sluggish recoveries characteristic of most other agents (Wright 1982). These

reactions are thought to be the result of CNS over stimulation. The consequences of feline

hallucinations are not known, but post-anesthetic personality changes have been reported

(Haskins et al. 1975).









Ketamine

Ketamine hydrochloride is classified as a short-acting dissociative anesthetic that is used

for chemical restraint, anesthesia induction, and surgical anesthesia in cats (Saywer et al. 1993).

It is a rapid-acting general anesthetic that has significant analgesic activity and lacks

cardiopulmonary depressant effects (Plumb 2005). In the past, ketamine has been recommended

for most surgical procedures in cats, including abdominal surgery (Evans et al. 1972).

The functional disorganization associated with ketamine is the reason for its classification

as a dissociative (Hanna et al. 1988). Ketamine is a non-competitive N-methyl-D-aspartate

(NMDA) receptor antagonist (Thurmon et al. 1996). By inhibiting NMDA receptors, it is thought

that ketamine may prevent nociceptive stimulation (Woolf & Thompson 1991). While its exact

mechanism remains unclear, ketamine induces anesthesia by selectively interrupting CNS

reactivity to various sensory impulses, without blocking sensory input at spinal or brain stem

levels (Wright 1982). This mechanism is unique as most anesthetic properties cause complete

CNS depression.

After inj section, patients enter a cataleptic state, similar to a trance, in which loss of

voluntary motion and muscle rigidity are often seen (Evans et al. 1972). Lack of complete

muscular relaxation makes ketamine unsuitable as a sole anesthetic agent (Bill 2006). In cats,

ketamine only provides loss of clinical reaction to pain during its maximal effect (Haskins et al.

1975). Additional doses of ketamine do not enhance muscle-relaxing effects, but do prolong

recovery (Arnbjerg 1979).

Recommended doses vary depending on desired depth of anesthesia, route of

administration, and the use of other anesthetics concomitantly. In cats, ketamine can be given in

doses ranging from 2-33 mg/kg, although doses of 50 mg/kg have been used without fatalities

(Arnbjerg 1979; Wright 1982). Ketamine produces dose-related unconsciousness and analgesia









with a rapid onset of action (Thurmon et al. 1996). Following intramuscular inj section, cats

become recumbent in 1 to 8 minutes (Lumb & Jones 1973). After intramuscular injection, peak

drug levels occur within approximately 10 minutes with the highest concentrations found in the

brain, liver, lung and fat (Plumb 2005). Duration of anesthesia is approximately 30 to 45 minutes

(Lumb & Jones 1973). In one study, small doses (4 and 8 mg/kg) of ketamine caused slow

induction times and produced circulatory stimulation, catatonia, and bizarre behavior. Larger

doses (32 and 64 mg/kg) caused circulatory depression, respiratory depression, and prolonged

recovery times (Child et al. 1972).

Ketamine is excreted in the urine and a cat' s reduced ability to excrete the drug due to

compromised renal function may prolong recovery (Haskins et al. 1975). Ketamine is rapidly

biotransformed to its only known metabolite, norketamine, in the cat (Chang & Glazko 1974;

Heavner & Bloedow 1979). The elimination half-life of ketamine in the cat is approximately 1

hour (Plumb 2005). Recovery from symptoms associated with ketamine may not be complete

within 10 hours, but most cats can stand unassisted within 2 hours (Evans et al. 1972)

Ketamine offers many advantages. The route of administration is versatile as it can be

administered subcutaneously, intravenously, intramuscularly, orally, and rectally (Wright 1982;

Hanna et al. 1988; Wetzel & Ramsay 1998). Additionally, ketamine may aid in the prevention of

post-operative pain as it has shown to exhibit weak visceral analgesic properties (Saywer et al.

1993). Finally, ketamine has gained favor for use in animal surgical procedures because of its

apparent lack of depressant effects on the cardiovascular and respiration systems when used in

small doses (Child et al. 1972; Haskins et al. 1975)

Ketamine: Cardiovascular and Respiratory Effects

Ketamine stimulates the heart and lacks the depressant effects prevalent in other

anesthetics (Wright 1982). The effects of ketamine on the cardiovascular system include









increased cardiac output, heart rate, mean aortic pressure, pulmonary artery pressure, systemic

arterial blood pressure, and central venous pressure (Wong & Jenkins 1975; Plumb 2005). An

increase in heart rate and blood pressure has been reported in a clinical setting, but the increase

in heart rate is not proportional to the dose of ketamine given (Arnbj erg 1979).

Ketamine causes dose-dependent respiratory depression (Wright 1982). Apneustic

breathing is defined as sustained tonic contraction of the respiratory muscles, resulting in

prolonged inspiration. Ketamine is capable of inducing an apneustic respiratory pattern, and may

be the result of its ability to alter the functional organization of the respiratory controller

(Pokorski et al. 1987). Respiratory rates and/or tidal volumes were decreased by ketamine in cats

and occasionally transient apnea has been reported (Wright 1982).

Ketamine: Side Effects

Ketamine has a pH of 3.5 and tissue irritation may occur during intramuscular inj section as

a result of its acidic properties (Wright 1982). Pedal reflexes remain intact and purposeless

movements, of varying degree, are often seen unrelated to specific noxious stimuli (Evans et al.

1972). Cat' s eyes remain open after ketamine administration and need to be protected with an

ophthalmic lubricant (Plumb 2005). Reduced body temperature may be seen with high doses of

ketamine (Arnbj erg 1979). Body temperatures decrease on average 1.6oC after therapeutic doses

(Plumb 2005). Due to its dissociative effects, hallucinatory behavior may be observed during

emergence from ketamine anesthesia (Thurmon et al. 1996). Cats should be placed in areas with

little visual or auditory stimulation to aid in a smoother recovery. Additional emergence

reactions include ataxia, increased motor activity, sensitivity to touch, avoidance behavior of an

invisible object, and violent recovery (Plumb 2005). Sialorrhea, or excessive salivation, is also

commonly seen with ketamine use (Evans et al. 1972). Most cats recover from these symptoms

within several hours without further reoccurrence (Wright 1982).









Medetomidine and Ketamine Combination

There are a number of reports using a combination of medetomidine and ketamine in cats

for anesthetic purposes (Verstegen et al. 1989; Verstegen et al. 1990; Verstegen et al. 1991a;

Dobromylskyj 1996; Wiese & Muir 2006). Used in combination, the centrally stimulating effects

of ketamine have been reported to balance the depressive effects of alpha2-agOnists (Verstegen et

al. 1991a). The tendency for ketamine to increase heart rate may assist in counteracting negative

cardiovascular effects associated with medetomidine (Verstegen et al. 1991a).

In cats, the use of medetomidine (80-100 Clg/kg) with a low dose of ketamine (7 mg/kg)

proved to be sufficient for short acting (20-40 minutes) surgical anesthesia (Vaha-Vahe 1989b).

Verstegen et al (1991) found that medetomidine (80 Clg/kg) greatly potentiated the effects of low

doses (5-7.5 mg/kg) of ketamine, providing suitable surgical anesthesia for 59 minutes.

Intramuscular administration of medetomidine (80 Clg/kg) combined with ketamine at doses of

2.5, 5, 7, 7.5 and 10 mg/kg produced anesthesia in less than 4 minutes and the duration ranged

between 36 and 99 minutes, dependent upon the dose of ketamine (Verstegen et al. 1990;

Verstegen et al. 1991a). When increasing the dose of ketamine from 2.5 to 10 mg/kg, the

duration of anesthesia was significantly extended (Verstegen et al. 1991a). Although the duration

of action was found to be closely related to the dose of ketamine, the quality of anesthesia was

similar in all groups. Verstegen and others reported the advantages of the

medetomidine/ketamine combination over that of the xylazine/ketamine combination to be the

need for a lower dose of ketamine, a longer duration of action, and better analgesia (Verstegen et

al. 1990). It was concluded that medetomidine combined with low doses of ketamine forms a

suitable combination for anesthesia in cats.









Medetomidine and Ketamine Combination: Cardiovascular and Respiratory Effects

Bradycardia in cats is evident with medetomidine/ketamine combinations. In one study,

varying doses of ketamine were combined with 80 Clg/kg of medetomidine and evaluated. When

the dose of ketamine was increased from 2.5 to 10 mg/kg a change from bradycardia to mild

tachycardia was observed (Verstegen et al. 1991a).

In the same study, additional anesthetic drug combinations were evaluated, including

combining ketamine with acepromazine or xylazine. Bradypnoea was seen in all groups

receiving ketamine, regardless of its anesthetic pairing (Verstegen et al. 1991a). Verstegen et al

(1990) observed no respiratory depression in cats anesthetized with 80 Clg/kg of medetomidine

and 5 mg/kg of ketamine (Verstegen et al. 1990). However, periods of apnea were observed in

cats anesthetized with 80 Clg/kg of medetomidine and 10 mg/kg of ketamine (Verstegen et al.

1991a).

Medetomidine and Ketamine Combination: Side Effects

The most common side effects seen with the concomitant use of medetomidine and

ketamine are vomiting, excitability, and apnea (Verstegen et al. 1990; Verstegen et al. 1991a).

Analgesia

NSAIDS

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in pain management in

both humans and animals as they are easy to administer, inexpensive, offer a long duration of

action, and are not controlled substances (Papich 2000). NSAIDs, however, are not widely used

in cats due to potential toxic effects. Due to their deficiency of certain metabolic pathways,

particularly hepatic glucoronidation, cats are prone to decreased NSAID metabolism (Lascelles

et al. 2007). This prolongs the duration of effect and may ultimately result in drug accumulation.

Slow clearance may result in hyperthermia, metabolic acidosis, and kidney or liver injury (Davis









& Donnelly 1968). Severe adverse effects associated with NSAIDs also include gastrointestinal

ulceration, perforation, and bleeding or renal ischemia (Papich 2000). NSAID use should be

based on confirming normal renal function prior to use; and doing so in feral cats is not feasible.

Hypotension during anesthesia can contribute to the renal toxicity of NSAIDs and blood pressure

is rarely measured during feral cat procedures. Additionally, dehydration due to trapping may

make some cats more susceptible to NS AID toxicity. Because feral cats do not participate in

follow up examinations post-operatively, NSAID use is inappropriate. Alternative methods of

pharmacologic analgesia should be sought for use in feral cats.

Opioids

Opioids are defined as any natural or synthetic drug that produces analgesia without loss of

proprioception or consciousness (Gaynor & Muir 2002). An important advantage for opioid

analgesics is that they can be administered without fear of the potential side effects associated

with NSAIDS (Papich 2000). Opioid drugs are highly effective and remarkably safe (Papich

2000). They are generally characterized by rapid and extensive distribution as they are highly

lipophilic drugs (Papich 2000). Opioids exert their effects by interaction with opioid receptors

located on cell membranes and are currently one the most effective systemic means of

controlling post-operative pain (Gaynor & Muir 2002)There are three known opioid receptor

classifications: mu, kappa, and delta; however, more types likely exist (Gaynor & Muir 2002;

Evers & Maze 2004). Receptors are located throughout the body and drugs acting on them

produce a variety of effects on tissue and organ systems (Pascoe 2000). Opioid drugs are

classified as agonist, partial agonist, antagonist, or agonist-antagonist based on their affinity for

specific opioid receptors (Gaynor & Muir 2002).










Buprenorphine

Effective pain control is important in regards to the development of an anesthetic regime.

The concomitant use of medetomidine and ketamine has been reported to offer analgesic

properties. In one study, cats administered a combination of medetomidine and ketamine were

shown to have less post-operative pain after ovariohysterectomy when compared to other

anesthetic regimes (Slingsby et al. 1998). However, the short duration of action associated with

these drugs likely limits their use as sole analgesics (Paddleford & Harvey 1999). In addition,

any potential analgesic effects of medetomidine are reversed.

In the proposed combination, MKB includes a drug specifically for pain control,

buprenorphine. Buprenorphine is the most popular opioid analgesic used in small animal species

in the UK and is widely used in other parts of Europe, Australia, and South Africa (Watson et al.

1996; Capner et al. 1999; Joubert 2001). In clinical studies, it has provided better analgesia than

other opioids and is considered highly suitable for perioperative pain management in cats

(Dobbins et al. 2002; Robertson & Taylor 2004).

Buprenorphine is classified as a partial mu-opioid agonist (Howland & Mycek 2000). Mu-

receptors are responsible for euphoria, sedation, analgesia, and respiratory depression (Papich

2000). Partial mu-opioid agonist implies that buprenorphine does not produce the same effects as

a full agonist, such a morphine (Pascoe 2000). However, buprenorphine has produced better

analgesia in clinical studies in cats when compared with morphine (Stanway et al. 2002).

Agonists acting on receptor sites inhibit pain transmission or modulate pain sensation by

inhibiting neurotransmitters associated with pain production (Papich 2000). Use of

buprenorphine in cats is associated with euphoria, and often purring combined with rolling and

kneading of the front paws (Robertson et al. 2005). The euphoric effects associated with mu-

opiate receptors help to relieve anxiety and stress for cats in an unfamiliar environment (Papich









2000). Another advantage to using buprenorphine is its long acting effects, which may exceed 6

hours in cats (Pascoe 2000; Robertson et al. 2005). The recommended dose for buprenorphine

ranges from 5-20 Clg/kg in cats and can be administered intramuscularly, intravenously,

subcutaneously, transmucosally, and orally (Pascoe 2000; Robertson et al. 2005). Thermal

threshold responses have been used to evaluate the efficacy of buprenorphine. Cats that received

10 Clg/kg of buprenorphine intramuscularly increased thermal threshold from 4 to 12 hours

following administration (Robertson et al. 2003). Another study concluded that thermal threshold

only increased 45 minutes after a subcutaneous inj section of buprenorphine (20 Clg/kg) (Steagall

et al. 2006). This suggests that the route of administration of buprenorphine may impact its

effectiveness. Routes that lead to slow uptake may not achieve sufficient concentration gradients

to drive the drug into the biophase (Steagall et al. 2007). No difference was seen in pain scores

between control groups, who did not receive any analgesics, and cats administered 6 Clg/kg of

buprenorphine intramuscularly after ovariohysterectomy (Slingsby & Waterman-Pearson 1998).

Buprenorphine: Side Effects

In animals, well documented effects of excitement and dysphoria exist in conjunction with

opioid use (Papich 2000). Cats are ordinarily the species considered to be more prone to

excitatory effects associated with opioid administration (Papich 2000). However, many of the

studies concluding these reactions were used in healthy, alert animals in which doses of opioids

in excess of those required for analgesia were administered. These effects seem to be less

apparent when opioids are administered to animals in pain (Papich 2000). Buprenorphine, on the

other hand, is rarely seen to cause dysphoria in cats (Robertson & Taylor 2004).

The use of opioid analgesics often raises concerns regarding clinical hyperthermia, or the

elevation of body temperature above normal range. In cats, hyperthermia is considered to be >

39.3oC (103oF) (Tilley & Smith 2004). The effects of severe hyperthermia are primarily related









to an increase in metabolic activity and cellular oxygen consumption and generalized cellular

necrosis associated with the denaturation of proteins, enzymes, and cell membranes (Niedfeldt &

Robertson 2006). Doses of buprenorphine ranging between 10-20 Clg/kg were not found to cause

hyperthermia in cats when compared with other opioid analgesics (Niedfeldt & Robertson 2006;

Posner 2007).

An additional side effect associated with buprenorphine use in cats is excessive mydriasis,

or pupil dilation (Robertson & Taylor 2004). Precautions need to be taken when approaching the

animal as they may not see clearly. In addition, they should be kept away from bright lights

while their pupils are excessively dilated. Buprenorphine rarely causes dysphoria or vomiting in

cats (Robertson & Taylor 2004). Buprenorphine is highly effective, easily administered, long-

acting and considered highly suitable for pain management in cats (Robertson & Taylor 2004).

Opioid and Alpha2 Agonists

Interestingly, a close association between opioid and alpha2-adenoceptors has been

identified (Unnerstall et al. 1984). Enhanced antinociception occurs following simultaneous

administration of agonists at specific sites in the spinal cord (Ossipov et al. 1989; Ossipov et al.

1990; Omote et al. 1991). Alpha2 agOnists and mu-opioid agonists produce similar

pharmacological effects in the CNS because their receptors are located in the same area of the

brain, are connected to the same signal transducer, and the same effector mechanism is used by

both agonists (Paddleford & Harvey 1999). Heightened effects of opioid and alpha agOnist

combinations may prove to be useful in potentiating their anesthetic and analgesic properties for

use in feral cat sterilization surgery.

Summary

The overpopulation of feral cats has contributed to a variety of problems including animal

welfare concerns, detriment to wildlife, and public health considerations. These issues have










sharply divided veterinarians, ecologists and conservationists, as well as the general public. In

the quest for a solution, some control methods have proven to be ineffective, while others offer

considerable promise. Currently, there is no obvious answer as to what the most effective

management strategy is. Trap-neuter-return programs offer an alternative to lethal eradication

methods and are bridging the gap until other solutions become available. Due to the unique

situation feral cats present, successful anesthesia in high-volume clinics is challenging. The

currently used anesthetic protocol, TKX, possesses limitations that have prompted the search for

a superior alternative. The purpose of this study was to evaluate a combination of medetomidine,

ketamine, and buprenorphine (MKB) for use in large-scale feral cat sterilization clinics.









CHAPTER 2
MATERIALS AND METHODS

Animals

Feral cats admitted to trap-neuter-return programs in Alachua County (Operation Catnip"

and Maddie's Outdoor Cat Program ) were used in this study. Cats were captured from their

colonies using humane traps and were transported to the University of Florida' s College of

Veterinary Medicine by colony caregivers for sterilization. Over a 2-year study period, a total of

240 cats and kittens were anesthetized using a combination of medetomidine, ketamine, and

buprenorphine (MKB). Cats selected for the study were of unknown health status and because of

this; all researchers were required to wear gloves and be vaccinated for rabies.

Overview

All anesthetic and surgical procedures were approved by the University of Florida

Institutional Animal Care and Use Committee. Cats arrived on the morning of surgery in wire

traps or plastic crates. Upon arrival, cats were assigned an identification number and a medical

record to document anesthetic and surgical details. Cats were sterilized, vaccinated, and had the

tip of their left ear removed for identification purposes. Cats were sent home later the same day.

Caretakers were instructed to release the cats to their colonies the following day.

Cat Selection

Every attempt was made to choose apparently healthy cats free from obvious signs of

upper respiratory infection or other advanced disease. Cats with evidence of trauma, fecal

staining from diarrhea or signs of dehydration were avoided. Most cats were judged to be adults

(> 1 year of age) (n = 23 8), although kittens under 6 months of age (n = 2) were included in the

study .









Anesthetic Drugs

Medetomidine HCI (M) 1 mg/ml (Domitor", Orion Corporation, Espoo, Finland),

ketamine HCI (K) 100 mg/ml (Ketaject", Phoenix Pharmaceuticals Inc, St. Joseph, MO, USA),

and buprenorphine HCI (B) 0.3 mg/ml (Buprenex", Reckitt Benckiser Healthcare, Hull, England,

UJK) were used in this study. Atipamezole HCI (A) 5 mg/ml (Antisedan Orion Corporation,

Espoo, Finland) was used to reverse the effects of medetomidine following the completion of

surgery .

Experimental Design

This study was divided into three separate phases. Phase I was a dose-finding study to

determine the optimal combination of medetomidine, ketamine, and buprenorphine to be used in

feral cat ovariohysterectomy and castration surgeries. The route of administration and dose of

atipamezole was modified based upon clinical observations and length of recovery. Each cat was

instrumented non-invasively with monitoring equipment for measurement of the following

physiological parameters: heart rate (HR), respiratory rate (RR), blood pressure (BP), and

hemoglobin oxygen saturation (SpO2). Time intervals including time to lateral recumbency,

surgical duration, and time from reversal to sternal recumbency were recorded. The preliminary

trials (Phase 1) continued until a satisfactory combination of MKB was achieved. The criteria

required for the selected dose of MKB included adequate duration of action, acceptable

physiological parameters, and rapid return to normal function.

Phase 2 of this study evaluated the physiological parameters of the selected combination

acquired in Phase 1. A total of 100 cats were to be anesthetized using the selected MKB

combination. Each cat was instrumented with non-invasive monitoring equipment that allowed

HR, RR, BP, and SpO2 to be recorded. Time to lateral recumbency, surgical duration, and time

from reversal to sternal recumbency were also recorded.










In Phase 3 of this study, a fixed dose was created using an average estimated body weight

of 3 kg/cat. A mixture of MKB was generated using the selected dosing regime evaluated in

Phase 2. From this mixture, a fixed volume was calculated to be used in each cat, regardless of

true weight. Physiological parameters were not monitored during Phase 3; although time to

lateral recumbency, surgical duration, and time from reversal to sternal recumbency intervals

were recorded. Adjustments to the calculated MKB fixed volume were made based upon

anesthetic requirements and overall assessment. If anesthesia was found to be inadequate, the

fixed volume was increased in 0. 1 mL increments. A fixed volume of atipamezole was calculated

based on the volume of medetomidine in the fixed anesthetic combination. Adjustments to

atipamezole were made based upon the volume of MKB, clinical observations, and the total time

of recovery.

Pre-operative Preparation

Cats were weighed in their traps on a pediatric scale. Ten empty traps were weighed and

determined to have an average weight of 2.4 + 0.1 kg. The estimated trap weight of 2.4 kg was

used consistently throughout this study, although actual trap weight was found to vary slightly.

An approximate body weight was calculated by subtracting the average trap weight (2.4 kg) from

the total weight of the cat plus the trap. This weight was used for MKB dose calculations.

Induction of Anesthesia

Cats were restrained at one end of the trap by passing a wire comb through the wire

meshing of the trap. A 22-gauge, 1-inch needle was used to administer an intramuscular inj section

of MKB. The target injection site was into the paralumbar muscles, although this route of

administration could not be confirmed.










Drug Administration Phase 1: Dose Finding Study

In Phase 1, several different anesthetic combinations were performed, varying the dose of

each drug and route of administration of the reversal agent. Previous evaluations of MKB

(Verstegen et al. 1991a) were the basis of the preliminary dosing regimes for the initial trials in

this study. Based upon duration of action and the physiological parameters, adjustments were

made in order to achieve optimum results. The drug combinations performed in Phase 1 are

shown in Table 2-1.

Each of the three drugs (M, K, and B) were measured separately and then combined into a

single syringe immediately prior to inj section. Each cat was administered a single intramuscular

inj section of MKB. If the initial dose of MKB was found to be insufficient, an additional dose of

10 Clg/kg of medetomidine was inj ected intramuscularly and recorded. Insufficient effect was

defined as: the cat was still responsive to toe pinch through the trap 10 minutes post-inj section. If

the depth of anesthesia was still found to be insufficient (at t = 15 minutes), an additional dose of

2.5 mg/kg of ketamine was inj ected intramuscularly. If anesthesia remained inadequate, a face

mask was placed on the cat and isoflurane vaporized in oxygen was administered, via a non-

rebreathing Bain anesthetic circuit, for the duration of surgery.

Dependent upon the conditions of the trial, atipamezole was given intramuscularly or

subcutaneously at a volume of 0. 125 or 0.25 times the initial volume of medetomidine. If cats

were not sternal 1 hour post-injection, a second dose of atipamezole was administered. This dose

was of equal volume and delivered intramuscularly, regardless of the initial route of atipamezole

admini strati on.

Drug Administration Phase 2: Selected Dose Study

Physiological parameters in cats given the selected drug combination from Phase I were

evaluated in Phase 2. Each of the three drugs (M, K, and B) were calculated based upon each









cat' s estimated weight (cat plus trap weight average trap weight) and combined in a single

syringe prior to inj section. The selected dosing regime is shown in Table 2-2.

If the initial dose of MKB was found to be insufficient (at t =10 minutes), an additional

dose of 20 Clg/kg of medetomidine was inj ected intramuscularly. If anesthesia remained

inadequate (at t=-15 minutes) an additional dose of 2.5 mg/kg of ketamine was inj ected

intramuscularly. If anesthesia continued to be insufficient, a face mask was placed on the cat and

isoflurane gas vaporized in oxygen was administered via a non-rebreathing Bain anesthetic

circuit, for the duration of surgery. At the completion of surgery, each cat received a

subcutaneous (intrascapular) dose of atipamezole to reverse the effects of medetomidine.

Drug Administration Phase 3: Fixed Dose Study

In Phase 3, the selected dosing regime (100 Clg/kg M, 10 mg/kg K, 10 Clg/kg B) was

calculated for a 3 kg cat (Table 2-4). A mixture of MKB was calculated to accommodate 20 cats

(Table 2-5). In a sterile 30 mL vial, 6.0 mL medetomidine, 6.0 mL ketamine, and 2.0 mL of

buprenorphine were mixed together. From this vial, an inj section volume of 0.7 mL was

withdrawn (Table 2-4). If anesthesia was found to be inadequate, the Eixed volume was increased

by 0. 1 mL (0.8 mL). The Eixed volume was administered to all cats, regardless of true weight.

The MKB inj section was administered intramuscularly. The target site was the paralumbar

muscles, although this could not be confirmed.

Subcutaneous atipamezole was administered post-operatively to reverse the effects of

medetomidine. The injection volume of atipamezole was 0.08 mL (0.4 mg) as calculated by the

initial volume of medetomidine (Table 2-6). If cats did not achieve sternal recumbency by 1-

hour following the inj section of atipamezole, an additional 0.4 mg (0.08 mL) of atipamezole was

given into the paralumbar muscle intramuscularly.









Cats that received the 0.8 mL (0.344 mg M, 34.4 mg K, 0.034 mg B) dose of MKB

participated in the high-volume clinic (Operation Catnip@) without time interval, physiological

measurement, or monitoring. Additionally, weights were not recorded. This was the first

simulation of what would normally take place in a high volume clinic using the MKB protocol in

mass. Due to the volume of cats anesthetized simultaneously, every effort was made to note the

need for supplemental anesthesia, although actual numbers may be higher.

Clinical Procedures: Evaluation of Anesthetic Effects

Following inj section, loss of reaction to toe pinch was tested from outside the trap. Once

determined to be unresponsive, each cat was carefully removed from its trap and its sex was

determined. Palprebral reflex, jaw tone, and overall muscle relaxation were evaluated and

recorded. These criteria were used to determine adequacy of anesthesia before, during, and after

surgical procedures.

Clinical Procedures: Hemoglobin Oxygen Saturation

A pulse oximeter sensor (Nellcor Puritan Bennett NPB-40, Nellcor Puritan Bennett Inc,

Pleasanton, CA, USA) was placed on the cat' s tongue for the purpose of monitoring oxygen

hemoglobin saturation (SpO2) lCVOIS and pulse rate. If readings could not be obtained from the

tongue, digits or an ear were used in an attempt to obtain additional readings.

Clinical Procedures: Evaluation of Cardiovascular Function

Blood pressure was measured using a Doppler probe (Ultrasonic Doppler Flow Detector,

Model 811-B and 811-L, Parks Medical Electronics Inc, Aloha, OR, USA). The hair over the

caudal carpus was shaved. Ultrasound gel was applied to the doppler probe, placed directly over

the digital arteries, and secured with zinc oxide tape. A small (size 3) blood pressure cuff

(Critikon Inc, Southington, CT, USA) was applied proximally and attached to a

sphygmomanometer (Welch Allyn, Beaverton, OR, USA) from which systolic blood pressure









values were obtained. The size of each cuff was determined by cuff width encompassing 48-50%

of the circumference of the forelimb where it was applied.

Heart rate and systolic blood pressure were measured and recorded at 5 minute intervals

throughout the duration of anesthesia. Pulse oximetry readings were only accepted if consistent

with the pulse rate counted from the Doppler probe and the heart rate obtained by palpation.

Clinical Procedures: Evaluation of Respiratory Function

Respiratory rate was determined visually (counted for 30 seconds). Clear surgical drapes

facilitated observation of chest movements during ovariohysterectomy surgeries. If clear surgical

drapes were not used, respiratory rate was determined by palpation. Respiratory rate was

conducted at 5 minute intervals throughout the duration of anesthesia.

Clinical Procedures: Temperature

Rectal temperature was measured using a standard electronic digital thermometer (MABIS

Healthcare, Inc., Waukegan, IL, USA). Temperature was determined at the time of induction, at

the completion of surgery, and 5 minutes following the reversal of medetomidine.

Clinical Procedures: Pre-surgical

A sterile petroleum-based ophthalmic lubricant (Akorn, Inc., Buffalo Grove, IL, USA) was

applied to both eyes and each cat was administered a long-acting penicillin inj section (Extended

Action Penicillin G Benzathine and Penicillin G Procaine, G.C. Hanford Manufacturing

Company, Syracuse, NY, USA) subcutaneously. Prior to surgery, approximately 1 cm of the

distal tip of the left ear was removed using a sterile hemostat and surgical scissors. This step was

used as the first indicator of anesthesia efficacy in our study. Finally, the hair was clipped from

the surgery site and the skin was prepared using alternating providing iodine and alcohol scrubs.









Clinical Procedures: Post-operative

After surgery was complete, each cat was vaccinated against rabies, feline leukemia virus,

feline panleukopenia virus, herpes virus, and calicivirus (FVRCP) (Rabvac@ 3TF Fort Dodge

Laboratories, Fort Dodge, IO, USA; Fel-O-GuardTM Plus 3 + Ly-K, Fort Dodge Laboratories,

Fort Dodge, IO, USA). The rabies vaccine was administered subcutaneously in the right hind leg.

The feline leukemia/FVRCP combination vaccine was administered subcutaneously in the left

hind leg. In addition, each cat received a single dose of selamectin (Revolution ) (Pfizer Animal

Health, Exton, PA, USA) administered topically for parasite control.

Quality of Recovery

Following the completion of surgery and the subsequent reversal of medetomidine, a

Quality of Recovery Score (QRS) was assigned and recorded according to predetermined

guidelines (Table 2-3).

Data

Least square mean (LSM) and true mean for physiological data were reported. The least

LSM is identical to the true mean assuming no missing data and the number of replications is the

same in each group. Because our data did not meet these criteria, both were reported for

comparison.

Statistical Analysis

SAS PROC MIXED (SAS Institute Inc., Cary, NC, 27513-2414, USA) was used to

evaluate physiological parameters in support of missing data. SAS PROC MIXED assumes data

are missing at random, which is suspected for the maj ority of absent records in this study,

although cannot be confirmed. Missing data was the result of equipment error, human error, or

the result of other unforeseen complications.









Individual anesthetic records were kept for each cat. Male and female data were compared.

Physiological variables (BP, RR, SPO2, HR, and rectal temperature), the time from MKB

inj section until lateral recumbency, the time from MKB inj section until the start of surgery,

surgical duration, the time from atipamezole administration to sternal recumbency, and the total

time recumbent were compared between males and females. Body weight, the need for

additional MKB, and the need for additional atipamezole were also compared between males and

females. In cats requiring additional MKB, time from reversal to sternal recumbency, total time

recumbent, and additional atipamezole requirements were compared and analyzed amongst

males and females, as well.

Weight, MKB inj section to time of lateral recumbency, MKB inj section to start of surgery,

surgical duration, time of reversal to sternal recumbency, and total time recumbent were

compared by means of an unpaired t-test. Physiological variables (BP, RR, HR, SPO2) were

compared separately over time by means of a two-factor ANOVA (Time-fixed; Subj ect-random)

test. Temperatures were compared over time using split-plot repeated measures ANOVA with

post hoc time comparisons by means of Bonferroni's t-test. The effect of multiple doses of MKB

on the total time recumbent was evaluated using a two-way ANOVA test (SAS PROC MIXED,

SAS Institute Inc., Cary, NC, 27513-2414, USA). Reversal to sternal time was compared

between cats that did or did not require additional MKB by means of an unpaired t-test.

The significance in the difference between physiological parameters upon the completion

of surgery and 5 minutes following atipamezole administration were compared in all cats.

Changes in physiological variables (BP, RR, HR, SPO2) before and after the reversal of

medetomidine were analyzed using split-plot repeated measures ANOVA. The a-priori

significance level used throughout this study was P < 0.05.









Finally, the associations between sex and additional MKB, and sex and the need for

additional reversal were evaluated using a 2 x 2 contingency table and a chi-square test.

Similarly, the need for additional MKB and the need for additional reversal were evaluated using

a 2 x 2 contingency table and a chi-square test for males and females separately. If expected

values were < 5, then a minimum chi-square test was used instead of chi-square.





Table 2-1. Dose-finding study
n= M K


Route of
Administration
IM
IM
IM
IM
IM
IM
SC
SC


gLg/kg mg/kg aLg/kg (x M volume)


Trial 1
Trial 2
Trial 3
Trial 4
Trial 5
Trial 6
Trial 7
Trial 8


0.25
0.25
0.25
0.25
0.125
0.25
0.25
0.25


Table 2-2. Selected dosing regime
Drug
Medetomidine (M)
Ketamine (K)
Buprenorphine (B)
Ativamezole (A)


Dose
100 pLg/kg
10 mg/kg
10 pLg/kg
0.25 x M volume


Route of Administration
IM
IM
IM
SC


Table 2-3. Quality of recovery scores
QRS Scoring Guidelines
3 Good: Smooth Recovery, No Excitement, < 45 min Reversal to Sternal Time
2 Acceptable: Mild Excitement and/or <1hr Reversal to Sternal Time
1 Unacceptable: Severe Excitement, 2nd Reversal, and/or >1hr Reversal to Sternal Time


Table 2-4. Fixed dose calculation
Drug
Medetomidine (M)
Ketamine (K)
Buprenorphine (B)


Dose
100 ug/kg
10 mg/kg
10 ug/kg


Concentration
1 mg/ml
100 mg/ml
0.3 mg/ml


mL/kg_
0.1
0.1
0.033


mL/k
mt/
0.3
0.3
0.1


Table 2-5. MKB mixture calculation (20 Cats)
mL/3
kg
Medetomidine (M) 0.3
Ketamine (K) 0.3
Buprenorphine (B) 0.1


x # of Cats Total (mL)
20 6
20 6
20 2











Table 2-6. Atipamezole fixed dose calculation
Volume of (M) x 0.25
0.3 mL x 0.25 = 0.075 mL









CHAPTER 3
RESULTS

Phase 1-Dose-Finding Study

During Phase 1 of this study, 69 cats (41 males, 28 females) were anesthetized with MKB

in 8 separate trial experiments (Table 3-1). All cats were of acceptable body condition and

appeared healthy at the time of the procedure. Pregnancy (n = 3) and bilateral cryptorchidism (n

=1) were observed in a small number of cats. In addition, one male was found to be previously

castrated.

Drug combinations in groups 1, 2, and 3 provided good anesthesia, however, duration of

action was inadequate for surgery completion. Duration of action in groups 1, 2, and 3 were 35 A

16 minutes (M: 36 minutes; R: 14-62 minutes) (Median, Range), 41 + 14 minutes (M: 45

minutes, R: 19-67 minutes), and 38 & 25 minutes (M: 30 minutes; R: 15-105 minutes),

respectively. In group 4 duration of action was sufficient (62 & 26 minutes) (M: 75 minutes; R:

32-79 minutes) and physiological parameters were acceptable, but recoveries were violent and

considered unacceptable in every cat (n = 3). In groups 5, 6, and 7 depth of anesthesia was good,

but the duration of action was inconsistent and was not considered acceptable. The duration of

action in groups 5, 6, and 7 were 50 & 28 minutes (M: 46 minutes; R: 26-84 minutes), 30 & 6

minutes (M: 30 minutes; R: 21-40 minutes), 35 & 6 minutes (M: 35 minutes, R: 26-47 minutes),

respectively.

The dose of atipamezole and route of administration in groups 1, 2, 3, and 4 provided

acceptable recovery times (< 1 hour). In group 5, the reversal dose was decreased by one-half to

see if a smaller dose would be sufficient. This protocol was found to result in delayed recoveries

(> 1 hour) and all cats (n = 4) required an additional inj section of atipamezole. The reversal

volume and route of administration in groups 6 and 7 were satisfactory, with group 7 providing









an alternate option for atipamezole administration (subcutaneous inj section Cats that received

subcutaneous atipamezole in group 7 were observed to have longer (28 & 15 minutes; M: 31

minutes, R: 5-50 minutes), yet acceptable, recoveries compared to group 4 (17 & 13 minutes; M:

14, R: 5-36 minutes). Recoveries in group 7 had no incidence of excitement or violent behavior.

Group 4 was considered the best with respect to adequate depth of anesthesia and duration

of action, however, recoveries were unacceptable. The recovery process appeared to take place

undesirably fast, and was accompanied by excitement and violent behavior. Based on these

observations, group 8 combined the MKB doses from group 4 (100 Clg/kg M, 10 mg/kg K, 10

Clg/kg B) with the reversal dose and route of administration from group 7 (1.25 mg (0.25 mL) x

M; subcutaneously). This protocol was carried out in 10 cats and exhibited superior qualities

when compared to previous trials. Duration of action was sufficient (33 A 1 1 minutes; M: 30, R:

15-57) and time to sternal recumbency (34 & 24 minutes; M: 25; R: 5-74 minutes) was adequate,

uneventful, and within acceptable recovery parameters. The protocol executed in group 8 was

considered to have the best potential for our needs, and therefore, was chosen for further

investigation.

Phase 1-Dose-Finding Study: Side Effects

In Phase 1, 4 cats displayed severe respiratory depression. All 4 cats received the same

dose of MKB (110 Cpg/kg M, 7.5 mg/kg K, 10 Cpg/kg B).

Phase 2-Selected Dose Study: Animals

One hundred and one cats (53 males, 48 females) were anesthetized with the selected

dose ofMKB (100 Clg/kg M, 10 mg/kg K, 10 Clg/kg B). Ninety-nine cats were identified as adults

and 2 cats were approximately 6 weeks of age. Two cats were pregnant and 2 cats were lactating

at the time of surgery. Three cats were found to be previously sterilized (1 male, 2 females),

therefore, a total of 98 cats (52 males, 46 females) were sterilized using the selected dose of









MKB. With one exception, all cats were considered to be free from obvious signs of disease or

trauma. One cat displayed signs of marked dehydration, diarrhea, and intestinal parasites upon

examination following MKB administration. There was evidence of external parasites, such as

fleas, on most cats.

There was no significant difference in the weight of male cats (3.2 & 0.2 kg) compared

with female cats (2.9 & 0.1) (P = 0.15). Cat weights ranged between 0.93 kg and 6.31 kg and

therefore, the volume of the MKB combination was between 0.22 mL and 1.4 mL, respectively.

Phase 2-Selected Dose Study: Time Intervals

Lateral recumbency was achieved in 4.3 & 4 minutes and 5.2 & 5.6 minutes (mean & SD)

after the inj section of MKB in male and female cats, respectively. There was no significant

difference in lateral recumbency times between males and females (P = 0.35). Eight cats (2

males, 6 females) vomited following anesthetic injection, however, the transition to lateral

recumbency was free from signs of CNS excitement. The time from MKB inj section until the start

of surgery was significantly longer in females (23 & 6.2 minutes) than in males (16.1 & 5.2

minutes) (P < 0.0001) due to longer surgical preparation requirements. Similarly, the surgical

duration was significantly longer in female cats (29.6 & 18.7 minutes) compared to male cats (3.2

& 2.5 minutes) (P < 0.0001).

The time from the inj section of the reversal agent atipamezole until the onset of sternal

recumbency was not significantly (P = 0.9) different between males (38.6 & 38 minutes) and

females (40.6 & 78.2 minutes). There was also no difference (P = 0.6) in time to sternal

recumbency in cats that received a second dose of MKB (n =11i).

The total time recumbent (including preparation, surgery, and recovery) was significantly

longer in females (86.9 & 27.1 minutes) than in males (64.7 & 36.2 minutes) (P = 0.0009). The

total time recumbent was significantly different (P = 0.008) in males (62 & 20.7 minutes) and









females (103.8 + 28.4 minutes) who required a second dose of MKB (7 males, 4 females),

however, there was no interaction observed between the two (total time recumbent and the need

for additional MKB) (P = 0.34).

There was no difference (P = 0.4) in the frequency of additional MKB requirements in

male (n = 7) and female (n = 4) cats. Similarly, there was no difference (P = 0.4) in the frequency

of cats (6 males, 8 females) requiring a second dose of the reversal agent, atipamezole. There

was also no association (P = 0.3) between cats that required a second dose of MKB and cats that

required a second dose of reversal agent.

Phase 2-Selected Dose Study: Physiological Variables

Physiological variables (BP, HR, SpO2, and RR) were measured immediately after

removal from the trap, throughout the surgical procedure, and 5 minutes following the reversal of

medetomidine. The feral nature of the cats prohibited further monitoring beyond this point.

Physiological data are missing intermittingly as a result of equipment error, human error, or other

unforeseen complications. Absent data are believed to be missing at random, although this

cannot be confirmed.

Male and female data were assessed separately over time. The average range of data

collections were between 5 and 35 minutes in males and between 5 and 85 minutes in females.

Data were collected every 5 minutes using set time intervals. The start point and the length of

these intervals were determined by the time of lateral recumbency and the surgical duration.

Following the reversal of medetomidine, physiological parameters were collected for an

additional 5 minutes in all cats when possible. Some measurements were unable to be obtained in

cats with unusually short recovery times.

In males, a relationship between blood pressure (R: 91-195 mm Hg) and time could not

be made (P = 0.52) with > 95% confidence. Blood pressure (R: 38-190 mm Hg) decreased










significantly over time (P < 0.0001) in female cats. One female cat was hypotensive (< 60 mm

Hg) at least once throughout the duration of anesthesia. Twenty-two cats (7 females, 15 males)

were hypertensive (> 160 mm Hg) at least once throughout the duration of anesthesia.

Normotension was observed following the administration of medetomidine and throughout the

duration of surgery in most cats (Figure 3-1 and Figure 3-2).

In males, heart rate (R: 77-176 beats/minute) did not significantly (P = 0.32) change over

time (Figure 3-3). No observation of tachycardia (> 180 beats/minute) was observed in any cat.

Conversely, heart rate (R: 57-172 bpm) significantly decreased (P < 0.0001) as a factor of time in

female cats (Figure 3-4). One female was observed to be bradycardic (< 60 beats/minute)

throughout the duration of anesthesia.

Severe hemoglobin desaturation was observed in both males (R: 36-99 %) and females

(R: 73-100 %) 5 minutes following the administration of MKB. Hemoglobin saturation was 81.1

+ 1.9% and 86.3 A 1.1 % 5 minutes following MKB administration in males and females,

respectively. Hemoglobin oxygen saturation, however, significantly increased over time in both

males (P = 0.0003) and females (P < 0.0001) (Figure 3-5 and Figure 3-6). There was no change

in respiratory rate over time in males (R: 4-76 breaths/minute) (P = 0.13) or females (R: 4-56

breaths/minute) (P = 0.14) (Figure 3-7 and Figure 3-8). Apneustic breathing was observed in 3

cats and periods of apnea (longer than 1 minute) were observed in 1 cat.

Oral mucus membrane color was also evaluated. Most cats contained pink membranes

and were considered clinically acceptable. In addition, capillary refi11 time was evaluated in most

cats and noted to be less than 2 seconds.

Rectal body temperature was measured at three separate times throughout the procedure:

following MKB induction (start), at the completion of surgery (pre-reversal), and 5 minutes









following the reversal of medetomidine (post-reversal) (Figure 3-9). Rectal temperature was

lower in females (P < 0.0001) at all three points in time and temperature decreased over time in

both males and females (P < 0.0001). Start, pre-reversal, and post-reversal temperatures in males

were 38.9 & 0.6oC, 38.2 & 0.7oC, 37.9 & 0.7oC, respectively. Start, pre-reversal, and post-reversal

temperatures in females were 38.7 & 0.5oC, 36.8 & 1.1oC, 36.7 & 1.2oC, respectively. No male

temperatures were below 34oC (93.2oF). One female had a temperature of 33.1oC (91.4oF) and

was considered hypothermic.

Phase 2-Selected Dose Study: Physiological Variables before and after Reversal

Physiological parameters obtained following the completion of surgery (pre-reversal) and

5 minutes following the reversal of medetomidine (post-reversal) were compared. Male (P <

0.0001) and female (P < 0.0001) blood pressures changed significantly over the 5 minute

reversal period, but did not change differently over the 5 minute reversal period (P = 0.37).

Blood pressures in females (P < 0.0001) were less than blood pressures in males (P < 0.0001)

both prior to the reversal of medetomidine and following the reversal of medetomidine (Figure 3-

10). Blood pressure was significantly lower post-reversal (P = 0.0003) when compared to pre-

reversal values (P < 0.0001) in both males and females.

Heart rate increased following the reversal of medetomidine in males (P < 0.0001) and

females (P < 0.0001) when compared to immediate pre-reversal values (Figure 3-11). Pre-

reversal heart rates in males were greater than in females (P = 0.0006), however, there was no

difference between male and female heart rates following the reversal of medetomidine (P =

0.25).

Following the reversal of medetomidine, hemoglobin oxygen saturation significantly

increased in males (P = 0.0001) and females (P = 0.03). Oxygen saturation value pre-reversal (P

< 0.0001) and post-reversal (P = 0.002) were significantly lower in males when compared to









females at both time points (Figure 3-12). There were no differences in respiratory rates in males

or females over time (P = 0.7).

Temperatures immediately following treatment with MKB were 38.9 & 0.6oC (102oF &

1.1) in males and 38.7 & 0.5oC (101.7 & 0.90F) in females. Following the completion of surgery,

temperatures dropped to 38.1 & 0.7oC (100.8 & 1.3oF) and 36.7 & 1.1oC (98.4 & 1.90F) in males

and females, respectively. Temperature was significantly lower (P < 0.0001) in males (37.9 &

0.7oC) (100.2 & 1.2oF), but not in females (36.6 & 1.2oC) (98.2oF) (P = 0. 16) following reversal.

Females, however, had lower temperature values at both pre-reversal and post-reversal

recordings (P < 0.0001) compared to males (Figure 3-13).

Phase 2-Selected Dose Study: Rescue Anesthesia (Isoflurane)

A total of 11 cats (2 males, 9 females) required supplemental anesthesia which constitutes

approximately 11% of the study population. Females required supplemental anesthesia

significantly more often (P = 0.02) than males. Rescue anesthesia in the 2 males was required at

the time of induction, following a second dose of MKB that proved to be insufficient. Of the 9

females that required supplemental anesthesia (isoflurane) 5 of them required it after 45 minutes

of successful anesthesia (timed from the initial inj section .

Phase 2-Selected Dose Study: Quality of Recovery Scores

Quality of Recovery Scores (QRS) (Table 3-2) were assigned following the completion

of surgery and subsequent reversal of medetomidine. Recovery times in males and females were

38.6 & 38 minutes (M: 30 minutes; R: 5-207 minutes) and 40.6 & 78.2 minutes (M: 22 minutes,

R: 4-130 minutes) in males and females, respectively. Ninety-eight cats (51 males, 47 females)

were scored for quality of recovery (QRS). Fifty-nine cats (28 males, 3 1 females) received a

QRS of 3 (good) and 15 cats (12 males, 3 females) received a QRS of 2 (acceptable). The

remaining 24 cats received a QRS of 1 (unacceptable), mainly due to prolonged recovery times










(n = 20). Only 4 cats (2 males, 2 females) were considered to have an unacceptable QRS as a

result of overly excited or violent behavior. Approximately 75% of cats achieved an acceptable

or good QRS.

Phase 2-Selected Dose Study: Side Effects

Under MKB anesthesia, apneustic breathing (holding of breath upon inspiration) was

observed in male (n = 3), but not female cats. Additionally, rapid shallow breaths were observed

in 6 anesthetized male cats. Eight males responded to the stimulus of castration surgery (tension

on the spermatic cord) by hind limb movements, while spontaneous movement was observed in

3 females. Spontaneous movements were defined as movement that did not occur in response to

a noxious stimulus; when it was noted, cats were checked by squeezing their toe and no response

was elicited. Spontaneous movement included paw extension and ear flicking. Post-induction

apnea (n = 1), post-operative retching (n = 1), and pawing at the mouth post-reversal (n = 6)

were also observed.

Phase 3-Fixed Dose Study (0.7 mL): Animals

Based on an average calculated weight of 3 kg/cat and the selected dosing regime

achieved in Phase 1 and tested in Phase 2, a Eixed-dose of MKB was extrapolated and performed

in Phase 3.

Two Eixed volumes of MKB were evaluated in this study. Thirty-six cats (16 males, 20

females) were anesthetized using an MKB Eixed dose volume of 0.7 mL (0.3 mg M, 30 mg K,

0.03 mg B). Seven cats were pregnant and one female was previously spayed.

The average weight for both male and female cats was 2.8 & 0.6 kg. Based on the Eixed

dose, the average cat received an overdose of MKB (107 Clg/kg M, 10.7 mg/ kg K, 10.7 Clg/kg

B). This represented a 7% increase in the total amount of medetomidine, ketamine, and

buprenorphine given in excess. The average weight for cats < 3 kg (n = 25) was 2.4 & 0.3 kg.









Based on the fixed dose volume, cats weighing less than 3 kg were overdosed (125 Cg/kg M, 12.5

mg/kg K, 12.5 Clg/kg B) on average by 25% for MKB. The smallest cat weighed 1.8 kg. Based

on the fixed dose, this cat was overdosed (166 Clg/kg M, 16.6 mg/kg K, 16.6 Clg/kg B) as well.

This represents a 66% increase in the amount of MKB given in excess. Approximately 30% of

cats (n = 11) weighed over 3.0 kg. The average weight for cats weighing > 3 kg was 3.56 & 0.4

kg. Cats weighing over 3 kg were under dosed (84 Clg/kg M, 8.42 mg/kg K, 8.42 Clg/kg B) by -

16% .

Seven cats (2 males, 5 females) needed an additional injection (0.1 mL; 0.043 mg M, 4.3

mg K, 0.0042 mg B) of MKB. Four of the 7 cats that required an additional inj section of MKB

weighed > 3.0 kg. Similarly, 7 cats (2 males, 5 females) required an additional inj section of the

reversal agent atipamezole, including 3 cats (1 male, 2 females) that received a second dose of

MKB. One female cat required a third inj section of atipamezole approximately 2 hours following

the initial atipamezole injection. That cat achieved sternal recumbency approximately 10 minutes

following the third inj section of atipamezole.

Phase 3-Fixed Dose Study (0.7 mL): Time Intervals

Time to lateral recumbency was 7 & 5 minutes and 4 & 3 minutes in males and females,

respectively. Surgical duration was longer in females (43 A 18 minutes) than in males (7 & 4

minutes). Time from reversal to sternal recumbency was 31 & 20 minutes in males and 31 & 31

minutes in females. Total time recumbent was 64 & 20 minutes and 117 & 46 minutes in males

and females, respectively.

Phase 3-Fixed Dose Study (0.7 mL): Side Effects

Apnea or severe respiratory depression was observed in several cats (n = 6). The weight

of these cats (4 females, 2 males) was 2.9 & 0.5 kg (M: 2.9 kg, R: 2.34-3.9 kg). One cat vomited

following inj section of MKB.









Phase 3-Fixed Dose Study (0.7 mL): Rescue Anesthesia

Thirteen cats (2 males, 11 females) required supplemental anesthesia. Of the 13 cats, 7

weighed more than 3.0 kg. Cats were further divided into those requiring inhaled supplemental

anesthesia before (n = 7) 45 minutes of successful anesthesia and after (n = 6) 45 minutes of

successful anesthesia. Approximately 36% of the total population receiving the fixed dose

required supplemental anesthesia. In conclusion, this number was far greater than our initial goal

of less than 10% of the population requiring rescue anesthesia, and therefore the volume of MKB

was increased.

Phase 3-Fixed Dose Study (0.8 mL):

Thirty-four cats (9 males, 25 females) were anesthetized using a fixed MKB volume of

0.8 mL (0.344 mg M, 34.4 mg K, 0.034 mg B). Physiological parameters were not monitored

and time intervals were not recorded.

Excessive requirements for MKB (n =3) or the need for supplemental isoflurane

anesthesia (n = 9) were observed. Because cats were monitored as a whole, and not individually,

this number may be higher as a result of missed data. Three cats vomited following the initial

inj section of MKB.

The initial injection of MKB was performed by an anesthetist unfamiliar with MKB and

its volume in 28 cats. In 4 of the cats (14%), the anesthetist reported difficulty inj ecting a larger

drug volume compared to the usual TKX protocol (0.25 mL). Two of the 4 cats with difficult

injections required supplemental anesthesia.

Apnea or severe respiratory depression was observed in most cats and was more recurrent

in cats anesthetized with MKB (fixed volume) in Phase 3, compared to those anesthetized in

Phase 2 (weight-specific). Because individual medical records were not kept for each cat, an









exact number is not available, although it is believed that more than half of the cats anesthetized

with the 0.8 mL fixed volume of MKB displayed clinical signs of respiratory distress.

Summary

Based on preliminary findings in Phase 1, a selected dosing regime was chosen to be used

in 100 feral cats. In Phase 2, cats anesthetized with the selected protocol were closely monitored,

recording physiological parameters and time intervals of interest throughout the surgical

procedure. The selected dose in Phase 2 provided an anesthetic combination that offered

acceptable physiological parameters and the potential for a fixed-volume derivative. In Phase 3,

a calculated a fixed volume of MKB (0.7 mL) based upon an average calculated value for a feral

cat' s weight (3.0 kg) was found to provide inadequate anesthesia. Based on these observations,

the decision was made to increase (0.8 mL) the fixed volume of MKB. The 0.8 mL of MKB was

considered undesirable as a high percentage (30%) of cats required rescue anesthesia. In

addition, apnea or respiratory depression was observed in most cats. There was no perioperative

mortality for cats anesthetized with MKB.

In conclusion, the selected dose of MKB used is Phase 2 offered potential when used in a

weight-specific manner, although failed to meet the goals set out at the start of the study when

extrapolated to a fixed dose to be used in all cats, regardless of true weight. In addition, the

adverse physiological effects observed with the fixed-dose results were less than desirable,

making the studied fixed dose of MKB an unsuitable combination for use in feral cats of

unknown weight.











Table 3-1. Dose-finding study groups
n= M ]


A

Route of
Administration

IM
IM
IM
IM
IM
IM
SC
SC


pLg/kg mg/kg pLg/kg (x M volume)


Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 8


0.25
0.25
0.25
0.25
0.125
0.25
0.25
0.25


Table 3-2. Quality of recovery scores
QRS Scoring Guidelines
3 Good: Smooth Recovery, No Excitement, < 45 minutes Reversal to Sternal Time
2 Acceptable: Mild Excitement and/or <1hr Reversal to Sternal Time
1 Unacceptable: Severe Excitement, 2nd Reversal, and/or >1hr Reversal to Sternal Time





180

160


mmHg l40

120


100


80
5 10 15 20 25 30 35
Minutes



Figure 3-1. Blood pressure in male cats over time


200

180

160


tumHg 140


-A--LSM
-=--True M ean


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85

Minutes





Figure 3-2. Blood pressure in female cats over time


---LSM
-a-- rue Mean



















T~~0 I


EU I
5 10 15 20 25 30 35
Minute s



Figure 3-3. Heart rate in male cats over time


*^




I -
1 m


- --LSM
-c-True Mean


be at s/tinut e


140

130

120

beats/minute 110


-A- LSM
-5- True Mean


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85
Minutes




Figure 3-4. Heart rate in female cats over time





110

105

100



SpO2 (%) 9




75

70


5 10 15 20 25 30 35
Minute s



Figure 3-5. Sp 02 (%) in male cats over time


110

105

100



SpO2~ (%)



80

75

70


-A- LSM
-m- True Mean


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85
Minute s



Figure 3-6. Sp 02 (%) in female cats over time


-- True Mean





















bre aths/minut e


10





5 10 15 20 25 30 35

Minutes



Figure 3-7. Respiratory rate in male cats over time


25


20


breathsiminute 15


10




0


-A- LSM
-m- True Mean


5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80

Minutes


Figure 3-8. Respiratory rate in female cats over time


-e- Trub M ean














I


36.7


39.5



38.5

Degrees Celsius 38

37.5



363

36


Start~ ~


Pre-Reversalm ~


P o st Revrs al C


Figure 3-9. Temperature over time


160

150

140

130

120
m~mH g
110

100

90

80

70


Pre-Reversal ~mmHg) P ostrRevers al mmHg)


Figure 3-10. Blood pressure before and after reversal


-a-Males
-a- Female s


~---Male s
-n-- Females












140

135

130

125

beats/minute 120

115

110

105

100


Pre-Revers al bpm) P ost-Reversal bpm)


Figure 3-11. Heart rate before and after reversal


97


95


SpO2 (%) 94

93



91


Pre-Revers al (%) Post-Reversal (%


Figure 3-12. SpO2 (%) Before and after reversal


--cMales
-ei Females


--cMales
-ei Females

























~ 36.8


40
39.5

39
38.5


Degrees Celsius 37.5
37
36.5
36

35.

Pre-Revers al )


Figure 3-13. Temperature before and after reversal


P ost-Revers al ~


-cFMales









CHAPTER 4
DISCUSSION

Feral cat sterilization clinics are an integral component of Trap-Neuter-Return programs.

Such programs present a variety of challenges and rely heavily on the efficacy, predictability,

and safety of an anesthetic regime. Not only must anesthesia protocols be adequate to perform all

surgeries, they must also safely and effectively render cats unconscious while still in their traps.

An anesthetic protocol for use in large feral cat clinics must be inj ectable, provide adequate

duration of action, support acceptable physiological parameters, have a wide margin of safety,

and allow rapid return to normal function. In addition, postoperative analgesia must be adequate.

TKX, the current anesthetic regime used in Operation Catnip", accommodates many of the

demands associated with feral cat anesthesia, however, it also posses inadequacies. An attempt to

improve the TKX protocol through the study of MKB was the purpose of this study. While MKB

may compensate for some of the limitations associated with TKX, the doses of MKB used in this

study exhibited its own shortcomings.

The preliminary trials of this study led to a MKB combination of considerable promise. In

Phase 1 of this study, superior components from two trial groups (4 and 7) were combined. It

was hypothesized that if the duration of action achieved in group 4 could be maintained while the

recoveries could be slowed down and still provide acceptable recovery times, the overall product

would provide adequate anesthesia and smoother recoveries, as seen in group 7. The anesthetic

and physiological effects of the selected dose were considered acceptable and even resolved

some of the limitations associated with TKX. However, when tested in a high-volume setting,

the MKB fixed volume offered less than desirable anesthetic effects; these including the frequent

need for additional MKB inj sections, rescue anesthesia with isoflurane gas, and repeated reversal

inj sections. In addition, apnea and respiratory depression were more pronounced and occurred









with a higher incidence in cats that received the fixed volume dose of MKB compared to those

dosed in a weight specific manor in Phase 2.

One study reported anesthetic-related deaths to be 0.24% (0.21-0.27%) in cats (n = 79,

178) sedated or anesthetized for a variety of surgical procedures using a wide range of drug

combinations (Brodbelt 2006). None of the cats (n =240) in this study died prior to being

released back to their colonies. The absence of perioperative mortality is thought to contribute to

a wide margin of safety associated with the use of MKB. The MKB protocol used in this study

was considered relatively easy to administer, although the large inj section volume may have

compromised the ability to accurately deliver full doses in some cats. Approximately 11 % of

cats in Phase 2 and 13% of cats in Phase 3 required a supplemental inj section of MKB. This may

have been the result of a large inj section volume preventing a complete and accurate inj section or

perhaps, more simply, the administration of a dose insufficient at providing adequate anesthesia.

Both of these factors may have contributed to the need for supplemental anesthesia. Female cats

had a greater need for rescue anesthesia compared to males. This is likely the result of lengthier

preparation and surgical procedures when compared to males.

Hemoglobin desaturation, particularly in the first five minutes following MKB

administration, was common in both male and female cats; however, it was more apparent in

male cats. One male cat was observed to report an oxygen saturation value of 36 % following

MKB administration. Respiratory depression and periods of apnea (temporary suspension in

breathing for more than 1 minute) were consistent with previous studies of similar medetomidine

and ketamine combinations (80Clg/kg M; 10 mg/kg K), in which apnea was observed in 8 out of

10 cats (Verstegen et al. 1989; Verstegen et al. 1991a).









Low SpO2 ValUeS may be caused by anything that decreases the delivery of oxygen to the

tissues including hypoxemia, vasoconstriction, or low cardiac output (Thurmon et al. 1996).

Cardiac output (CO) is defined as the quantity of blood pumped by the heart each minute and

varies dependent upon heart rate (HR) and stroke volume (SV) (Berne et al. 2004). The

relationship between cardiac output and heart rate is linear (CO = HR x SV). Low SpO2 ValUeS

may be the result of patient factors or detection limitations. Because pulse oximetry relies on

peripheral blood flow, the accuracy of readings may be affected as a result of the

vasoconstriction or decreased heart rate observed following the administration of medetomidine

(Haskins 1996). The observed hemoglobin desaturation, especially as seen following the

inj section of MKB, may have been the result of equipment inaccuracies or simply, the known

depressant cardiovascular effects of medetomidine. Cats were not intubated in this study and

spontaneously breathed room air. This was likely a contributing factor to low oxygen saturation

levels seen in cats anesthetized with both TKX and MKB. A study assessing a combination of

MKB with a significantly lower dose of medetomidine (40 Clg/kg) observed an overall SpO2

value of 94 + 4% (Cistola et al 2002). A higher dose of medetomidine, such as the amount used

in this study, may have affected SpO2 ValUeS as a result of increased vasoconstriction. An

increase in vasoconstriction may have contributed to either (1) a decrease in oxygen delivery to

tissues or (2) a decrease in the accuracy of pulse oximetry readings. SpO2 ValUeS were observed

to increase over time in MKB treated cats. It is hypothesized that the increase in SpO2 ValUeS

over time was a result of the metabolism of medetomidine, lowering plasma concentration

values, and exhibiting less total effect (vasoconstriction). A steady decrease in vasoconstriction

may have contributed to increased oxygen delivery, resulting in higher SpO2 ValUeS over time.

Alternatively, decreased vasoconstriction may have provided more accurate pulse oximetry









readings in which earlier readings, when medetomidine plasma concentrations were higher,

would be considered less precise. The true cause for the observed increase in SpO2 ValUeS is

unknown. Once the amount of deoxygenated hemoglobin exceeds 5 g/100 mL, the blood

changes from a red color to a blue color (cyanosis) (Thurmon et al. 1996). Despite low pulse

oximetry readings, oral mucous membrane color remained pink and was clinically acceptable in

most cats. Pale mucous membranes were noted and hypothesized to be the result of drug-induced

vasoconstriction following the administration of medetomidine. While low oxygen saturation is

preventable and easily treated by providing supplemental oxygen, it is not feasible to administer

to all cats due to the number of cats needing simultaneous administration and equipment

limitations. Additionally, the challenge of identifying cats at risk of hypoxia and supplementing

them as needed, should not be underestimated when many cats are anesthetized simultaneously.

Hypoxia may result in abnormal organ function and/or cellular damage (Thurmon et al. 1996).

The exact repercussions of low SpO2 leVOIS in cats anesthetized with MKB are unknown and

may result in injury not apparent in the immediate post-operative period.

Normal heart rates in cats range between 145 and 200 beats per minute (Muir et al 2000).

Following the administration of MKB, heart rate was significantly lower compared to normal

values, although true baseline values of conscious animals could not be determined in this study.

Ninety-one percent of cats in this study were observed to have lower than normal heart rate

values. In one study, heart rate in cats administered solely medetomidine (80 Clg/kg-110 Clg/kg)

decreased to about 50% of starting values within 15-30 minutes (Vaha-Vahe 1989a). While

baseline values were not obtained in this study, it is believed that the measured values following

induction were more than 50% of their starting values as a result of the cardiovascular

stimulating effects of ketamine. In combination, it is thought that the centrally stimulating effects









of ketamine counteract the depressive effects of alpha agOnist compounds (Verstegen et al.

1989). In this study, heart rate was not observed to change in males over time, but was

considered below normal throughout the duration of anesthesia. Female heart rates, on the other

hand, were observed to continually decrease over time to below normal values under anesthesia.

Decreased heart rate is believed to be the result of the bradycardic effects of medetomidine;

however, one study concluded that medetomidine in cats did not conclusively demonstrate

specific bradycardic action as a lowered state of vigilance could, in itself, decrease heart rate

(Stenberg et al. 1987). The observed bradycardia was believed to be a direct result of

medetomidine as these effects were reversed following the administration of atipamezole. While

the results of this study exhibited below normal heart rate values in anesthetized cats, one study

conversely found a similar dose of medetomidine and ketamine (80 Clg/kg M; 10 mg/kg K),

without buprenorphine, to result in tachycardia between 10 and 30 minutes following inj section.

Buprenorphine has been shown to decrease both blood pressure and heart rate in cats, suggesting

buprenorphine may have had an affect on heart rate in this study (Benson & Tranquilli 1992). It

is hypothesized that the analgesic properties of burpenorphine may have prevented an increase in

heart rate and blood pressure by blocking nociceptive input in response to surgical stimulus.

Some clinicians prefer to preemptively use anticholinergic drugs, such as atropine, in patients

administered alpha2-adrenergic drugs, however, others disagree (Paddleford & Harvey 1999).

They argue that (1) the bradycardia is a normal physiological response to vasoconstriction and

increased blood pressure, (2) anticholinergic drugs may increase myocardial work and oxygen

consumption due to an increased heart rate, and (3) it may not be physiologically appropriate to

have an increased heart rate in the face of severe vasoconstriction (Paddleford & Harvey 1999).









Normal systolic blood pressures in cats range between 110 and 160 mm Hg (Muir et al

2000). Normotension was observed following the administration of MKB and throughout the

duration of anesthesia in most cats. However, twenty-three cats were observed to have systolic

blood pressures rise above 160 mm Hg at least once following treatment with MKB, while 7 cats

were observed to fall below 110 mm Hg at least once following treatment with MKB. Whether

or not blood pressure was related to physiological stress is unknown, however, blood pressure

was not observed to rise consistently in response to surgical stimulation. In males, a relationship

between blood pressure and time could not be made with > 95 % confidence. A Type II

statistical error is suspected as this observation may be the result of missing data points (at 5, 10,

and 15 minutes only 10%, 60%, and 64% of data were available, respectively). Actual blood

pressures may be higher than reported as the technique used in this study may underestimate

systolic blood pressure by approximately 15% in cats (Grandy et al. 1992). In addition, there are

no published reports assessing the accuracy of the Doppler technique when systolic blood

pressure is in excess of 200 mm Hg (Dobromylskyj 1996). Values did not exceed 200 mm Hg in

this study, but some values were close (195 mm Hg). Blood pressures significantly decreased in

both males and females following the reversal of medetomidine. It is hypothesized that reversing

the vasconstrictive effects of medetomidine resulted in a decrease in vascular resistance, and

therefore a decrease in blood pressure.

Neither blood pressure nor heart rate was observed to increase at any time during the

surgical procedure. Similarly, in another study, a comparable combination although using a

lesser dose of medetomidine (80 Clg/kg), with ketamine (10 mg/kg) reported no reflex responses

to traction of the ovarian pedicles (Verstegen et al. 1989). Based on these observations in Phase










2, it is assumed that anesthesia was adequate in the majority of cats because changes suggestive

of response to nociceptive stimuli, as measured by physiological variables, were not detected.

Some opioids have been associated with an increase in body temperature in cats

(Robertson & Taylor 2004). Alternatively, opioids have actually been found to lower the

threshold for shivering, a thermoregulatory event that is meant to increase heat production,

which can further contribute to heat loss (Posner 2006). Post-anesthetic rectal temperatures were

not observed to rise significantly following buprenorphine administration in cats in a previous

study (Niedfeldt & Robertson 2006). While temperatures were only collected during times of

lateral recumbency in this study, no indication of measured hyperthermia (temperatures > 103

oF) or clinical evidence (panting) was noted. In fact, hypothermia was observed. The effects of

anesthesia on thermoregulation are multifactorial and include the loss of normal behavioral

responses and an altering of normal thermoregulatory responses (Posner 2006). Temperatures in

TKX treated cats (3 8.0 + 0.80C (100 & 1.4oF) in males and 36.6 & 0.80C (97.8 & 1.4oF) in

females) and MKB treated cats (38.1 & 0.7oC (100.7 & 1.3oF) in males and 36.7 & 1.1oC (98.3 &

2oF) in females) were similar at the time of reversal (Cistola et al. 2004). Loss of core body

temperature occurs in three phases, the first of which is due to the redistribution of heat from the

core to the periphery, where it is then easily lost (Posner 2006). Higher body temperatures found

in MKB cats may be attributed to the vasoconstrictive properties of medetomidine as

arteriovenous vasculature present in the skin contribute to thermoregulation (Posner 2006). The

subsequent vasoconstriction of these shunts likely prevents heat loss from the core (Posner

2006). Core temperatures may actually have been lower than measured, as rectal temperature

tends to lag behind changes in core body temperature (Posner 2006). Nevertheless, even mild

hypothermia can substantially prolong recovery times by decreasing hepatic and renal blood










flow, therefore slowing the metabolism of anesthetic drugs (Posner 2006). Medetomidine

elimination appears to rely heavily on biotransformation and is likely regulated by hepatic blood

flow, thus, maintenance of these metabolic processes is essential (Salonen 1989). The application

of external heat sources during surgery and recovery may reduce the severity of prolonged

recoveries and decrease recovery times; however, a logistical barrier arises when high numbers

of cats are undergoing surgery and recovery, simultaneously. In addition, the ability to apply

external heat sources from outside the trap is limited which will likely compromise effectiveness.

No observations of licking or biting at incision sites were noted. In addition, body posture

and overall demeanor appeared to be comfortable and relaxed in most cats.

Immediate post-operative analgesia was assumed to be adequate as several studies have

noted the efficacy of buprenorphine up to 6 hours (Pascoe 2000; Robertson et al. 2005). There

are no validated methods for pain assessment in cats, which makes evaluation and treatment

difficult, however, pain can be managed on the basis of previous experience and intuition

(Cambridge et al. 2000).

Overall, the recovery times observed with MKB were shorter compared to TKX with

reversal to sternal recumbency times of 72 & 42 minutes in cats administered TKX and 34 & 33

minutes in cats administered MKB in Phase 2 of this study (Cistola et al. 2004). Atipamezole

administration appeared to completely reverse the effects of medetomidine, as evident by the

significant increase in heart rate and decrease in blood pressure following reversal. Fourteen cats

required a second inj section of the reversal agent. In dogs, the manufacturer recommends giving

the same volume of atipamezole as medetomidine (5 mg/ml A: 1 mg/ml M) to reverse its effects

(2007). In this study, a quarter of the volume of medetomidine was administered. This dose was

sufficient in most cats; however, approximately 14% of the cats required additional reversal










agent inj sections. Perhaps a larger volume of atipamezole would have prevented the need for a

second reversal, although the side effects associated with an increased volume of atipamezole are

unknown and should be considered. An unusually fast recovery, as observed in Phase 1 of this

study, is unfavorable and could result with a larger dose of atipamezole. Relapse to sedation is

not believed to be the cause for the need for second reversal inj sections, as the half-life of

atipamezole is twice that of medetomidine (Paddleford & Harvey 1999). Interestingly, there was

no relationship between cats that received supplemental doses of MKB and cats that required an

additi onal reversal agent inj ecti on. Thi s may suggest that the initi al atipamezol e-medetomi dine

ratio was inadequate at providing acceptable recoveries in some cats. An atipamezole-

medetomidine dose ratio (in mg) of 4:1 or 8:1 resulted in speedier return to normal vigilance

patterns than a 2: 1 ratio in cats receiving only medetomidine (Stenberg et al. 1993). However,

one study that combined ketamine with medetomidine recommended a dose ratio of 2.5:1 as it

prevents the undesirable tachycardia and CNS stimulation seen with higher doses of atipamezole

(Verstegen et al. 1991b).

The selected dose in Phase 2 provided adequate duration of action in most cats. The

number of cats requiring isoflurane supplementation was considered clinically acceptable.

Approximately 1 1% of our study population required supplemental anesthesia. This was close to

our initially set goal of less than 10% of the population

requiring rescue anesthesia and the decision was made to initiate a fixed volume.

Both fixed dose volumes (0.7 mL and 0.8 mL) oflVIKB were found to be inefficient at

providing acceptable surgical anesthesia. Additionally, apnea and severe respiratory depression

were observed in most cats. In Phase 3, twenty-one cats (30%) required inhaled supplemental

anesthesia at some point throughout the surgical procedure. It is hypothesized that some of these









cats may have weighed > 3.0 kg and that individual anesthetic requirements were simply unmet.

Furthermore, the 0.8 mL Eixed dose was the first time anesthetists, other than those directly

associated with this study, used the MKB protocol. In 14% of the inj sections, the anesthetist

reported difficulty inj ecting the larger drug volume compared to the usual TKX protocol (.25

mL). Half of the cats with noted difficult inj sections required supplemental anesthesia. It is

hypothesized that these cats did not receive the full dose of MKB as they required supplemental

anesthesia shortly after the initial MKB inj section.

For those weighing < 3.0 kg, it remains unclear as to the differences observed in the Eixed

dose of MKB compared to the selected dose studied in Phase 2. Data on the number of cats

anesthetized with TKX that require supplemental anesthesia are not available; but, this

information would be useful in future studies to compare the failure rates between the two

protocols. Regardless, the frequency of supplemental anesthesia and obvious physiological

depressant effects observed with the Eixed dose of MKB are considered unacceptable and this

protocol is not recommended. If the individual weight of a feral cat could be verified prior to an

anesthesia regime, it is believed that a higher rate of success and usefulness would be observed

with the current combination of MKB. However, this would require increased time and labor

considerations.

The studied combination of MKB appears to offer several advantages. Medetomidine

potentiates the effects of ketamine and the disadvantages associated with the two drugs may be

offset by one another. Medetomidine makes up for the poor muscle relaxing and analgesic

effects of ketamine, while the cardiovascular stimulating effects of ketamine compensate for the

bradycardic tendencies of medetomidine (Verstegen et al. 1989). The use of the medetomidine' s

specific antagonist, atipamezole, allows for the complete and rapid reversal of the depressant









effects exhibited by medetomidine. In addition, the combination of medetomidine and

atipamezole may limit undesirable effects of less selective or less specific agonist/antagonist

combinations.

In conclusion, MKB appears to fulfill many of the demanding requirements necessary for

feral cat anesthesia when true weight is considered. In Phase 2, MKB provided a completely

inj ectable regime that was predictable, offered an acceptable duration of action, and provided a

rapid return to normal function. The maj or shortcoming of MKB in this study was the inability to

determine an effective fixed dose volume to be used in all cats, regardless of true weight.

Additionally, based on the high incidence of severe respiratory depression observed in cats

administered the fixed volume, it cannot be recommended. Moreover, it was determined that

increasing the fixed dose volume further would be without regard for the safety of the animal.

Although this study failed to produce an effective MKB fixed dose to be used in high volume

sterilization clinics, it is believed that MKB offers considerable promise in feral cat anesthesia.

Slight changes in Operation Catnip@ may enhance the effectiveness of MKB and may be

of interest in further investigations. It is believed that the MKB combination in this study would

be more effective if given in a weight-specific manor. The addition of a weight station would

enable a dose to be calculated for each individual cat, eliminating the need for a universal fixed

volume. Several categories of fixed volumes designed to accommodate weight classes (0-1 kg, 1-

2 kg, 2-3 kg, and > 3 kg) may prove to be beneficial. The addition of a weight station would,

however, add additional labor and time constraints. If an MKB dosing regime does not take

weight into consideration, it is possible that MKB will never be considered appropriate for use in

high-volume clinics. However, the studied combination of MKB may be suitable for smaller

clinics with fewer surgeries performed and shorter duration of action requirements.










There are approximately 1,440 combinations of MKB (based on relative doses of each

drug used in cats). This study is believed to have narrowed the findings for an effective

combination of MKB, although an exact fixed dose was not accomplished. Further research is

required to determine whether or not a specific combination of MKB has the ability to produce a

fixed volume that fulfills the unique demands of feral cat anesthesia and subsequent sterilization

procedures.









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BIOGRAPHICAL SKETCH

Kelly Ann Meyer was born on October 30, 1981 in Chicago, Illinois, to Paula and Edward

Meyer. An only child, she moved to Florida shortly after being born. Kelly graduated from

Seminole High School in Seminole, Florida, in 2000. In April 2005, she earned her B.S. from the

University of Florida in animal sciences and began working toward her M. S. degree shortly

thereafter.

Kelly's passion has always been animals and their well-being. She continues to pursue her

goal of becoming a Doctor of Veterinary Medicine.





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MKB: A NEW ANESTHETIC APPROACH TO FERAL CAT STERILIZATION SURGERY By KELLY ANN MEYER A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2007

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2 2007 Kelly Ann Meyer

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3 ACKNOWLEDGMENTS I would like to thank Dr. Sheilah Robertson, Dr Natalie Isaza, and Dr. Julie Levy for their unconditional support, their mentoring, and the tremendous opportunities they have offered me over the course of this study. I would also like to thank my parents for their patience, sincerity, and motivation in helping me to achieve a finish ed product. Finally, I would like to thank Justin for helping me to stay focused and Dr. Joe Ha uptman for his instruction and guidance in the statistical analysis port ion of this study.

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4 TABLE OF CONTENTS page ACKNOWLEDGMENTS...............................................................................................................3 LIST OF TABLES................................................................................................................. ..........6 LIST OF FIGURES................................................................................................................ .........7 ABSTRACT....................................................................................................................... ..............8 CHAPTER 1 INTRODUCTION..................................................................................................................10 Feral Cat Populations.......................................................................................................... ....10 The Problem.................................................................................................................... ........11 Public Health Considerations..........................................................................................12 Wildlife Vulnerability.....................................................................................................13 Animal Welfare...............................................................................................................15 Current Methods of Control....................................................................................................15 Removal Methods............................................................................................................16 Trap-Neuter-Return.........................................................................................................18 Nonsurgical Contraception..............................................................................................22 Operation Catnip: A Trap-Neuter-Return Program..............................................................23 Challenges of Working with Feral Cats..................................................................................24 Alpha2-Adrenoceptors............................................................................................................28 Medetomidine................................................................................................................... ......29 Medetomidine: Cardiovascular and Respiratory Effects.................................................30 Medetomidine: Side Effects............................................................................................32 Atimpamezole................................................................................................................... ......32 Atipamezole: Side Effects......................................................................................................33 Dissociative Anesthesia........................................................................................................ ..33 Ketamine....................................................................................................................... ..........34 Ketamine: Cardiovascular and Respiratory Effects........................................................35 Ketamine: Side Effects....................................................................................................36 Medetomidine and Ketamine Combination............................................................................37 Medetomidine and Ketamine Combination: Cardiovascular and Re spiratory Effects...38 Medetomidine and Ketamine Co mbination: Side Effects...............................................38 Analgesia...................................................................................................................... ..........38 NSAIDS......................................................................................................................... ..38 Opioids........................................................................................................................ ....39 Buprenorphine.................................................................................................................. ......40 Buprenorphine: Side Effects...................................................................................................41 Opioid and Alpha2 Agonists...................................................................................................42 Summary........................................................................................................................ .........42

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5 2 MATERIALS AND METHODS...........................................................................................44 Animals........................................................................................................................ ...........44 Overview....................................................................................................................... ..........44 Cat Selection.................................................................................................................. .........44 Anesthetic Drugs............................................................................................................... .....45 Experimental Design............................................................................................................ ..45 Pre-operative Preparation...................................................................................................... .46 Induction of Anesthesia........................................................................................................ ..46 Drug Administration Phase 1: Dose Finding Study........................................................47 Drug Administration Phase 2: Selected Dose Study.......................................................47 Drug Administration Phase 3: Fixed Dose Study............................................................48 Clinical Procedures: Evaluati on of Anesthetic Effects...........................................................49 Clinical Procedures: Hemoglobin Oxygen Saturation............................................................49 Clinical Procedures: Evaluation of Cardiovascular Function.................................................49 Clinical Procedures: Evaluati on of Respiratory Function......................................................50 Clinical Procedures: Temperature..........................................................................................50 Clinical Procedures: Pre-surgical...........................................................................................50 Clinical Procedures: Post-operative........................................................................................51 Quality of Recovery............................................................................................................ ....51 Data........................................................................................................................... ..............51 Statistical Analysis........................................................................................................... .......51 3 RESULTS........................................................................................................................ .......56 Phase 1-Dose-Finding Study..................................................................................................56 Phase 1-Dose-Finding Study: Side Effects.............................................................................57 Phase 2-Selected Dose Study: Animals..................................................................................57 Phase 2-Selected Dose Study: Time Intervals........................................................................58 Phase 2-Selected Dose Study: Physiological Variables.........................................................59 Phase 2-Selected Dose Study: Physiologica l Variables before and after Reversal................61 Phase 2-Selected Dose Study: Re scue Anesthesia (Isoflurane).............................................62 Phase 2-Selected Dose Study: Quality of Recovery Scores...................................................62 Phase 2-Selected Dose Study: Side Effects............................................................................63 Phase 3-Fixed Dose Study (0.7 mL): Animals.......................................................................63 Phase 3-Fixed Dose Study (0.7 mL): Time Intervals.............................................................64 Phase 3-Fixed Dose Study (0.7 mL): Side Effects.................................................................64 Phase 3-Fixed Dose Study (0.7 mL): Rescue Anesthesia.......................................................65 Phase 3-Fixed Dose Study (0.8 mL):......................................................................................65 Summary........................................................................................................................ .........66 4 DISCUSSION..................................................................................................................... ....75 LIST OF REFERENCES............................................................................................................. ..87 BIOGRAPHICAL SKETCH.........................................................................................................96

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6 LIST OF TABLES Table page 2-1 Dose-finding study......................................................................................................... ....54 2-2 Selected dosing regime..................................................................................................... .54 2-3 Quality of recovery scores.................................................................................................54 2-4 Fixed dose calculation..................................................................................................... ...54 2-5 MKB mixture calculation (20 cats)....................................................................................54 2-6 Atipamezole fixed dose calculation...................................................................................55 3-1 Dose-finding study groups.................................................................................................67 3-2 Quality of recovery scores.................................................................................................67

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7 LIST OF FIGURES Figure page 3-1 Blood pressure in male cats over time...............................................................................68 3-2 Blood pressure in female cats over time............................................................................68 3-3 Heart rate in male cats over time.......................................................................................69 3-4 Heart rate in female cats over time....................................................................................69 3-5 SpO2 (%) in male cat s over time........................................................................................70 3-6 SpO2 (%) in female cats over time.....................................................................................70 3-7 Respiratory rate in male cats over time..............................................................................71 3-8 Respiratory rate in female cats over time..........................................................................71 3-9 Temperature over time...................................................................................................... .72 3-10 Blood pressure before and after reversal...........................................................................72 3-11 Heart rate before and after reversal....................................................................................73 3-12 SpO2 (%) before and after reversal....................................................................................73 3-13 Temperature before and after reversal...............................................................................74

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8 Abstract of Thesis Presen ted to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Master of Science MKB: A NEW ANESTHETIC APPROACH TO FERAL CAT STERILIZATION SURGERY By Kelly Ann Meyer December 2007 Chair: Sheilah Robertson Major: Veterinary Medical Sciences A combination of medetomidine (M), keta mine (K), and buprenorphine (B) (MKB) was evaluated as an injectable anesthetic in 240 feral cats unde rgoing ovariohysterectomy or castration surgery at a highvolume sterilization clinic. A selected dose of MKB (100 g/kg M, 10 mg/kg K, 10 g/kg B) was evaluated for efficacy in a weight-specific manner and was then extrapolated to a fixed dose to be used in all ca ts, regardless of true weig ht. The selected dose of MKB provided adequate duration of action, accept able physiological parameters, and acceptable duration and quality of recovery; however, the fixed dose of MKB was ineffective and unreliable. Cats were not intubated and breathed room air. Hemoglobin oxygen saturation (SpO2), systolic blood pressure (BP), heart rate (HR), re spiratory rate (RR), and rectal temperature were measured and recorded. Atipamezole (A) (5 mg/mL) was administered following the completion of surgery to reverse the effects of medetomidine. The selected dose of MKB (100 g/kg M, 10 mg/kg K, 10 g/kg B) produced rapid onset of lateral re cumbency (4.3 4 minutes in males and 5.2 5.6 minutes in females) and adequate durati on of surgical anesthes ia in both males and females.

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9 SpO2 significantly increased over time in both males (R: 36-99 %) (R = range) and females (R: 73-100 %). SpO2 fell below 90% at least once in mo st cats. Blood pressure (R: 91-195 mm Hg) and heart rate (R: 77-176 beats/minute) in male s did not change significantly as a factor of time, however, blood pressure (R: 38-190 mm Hg) and heart rate (R: 57-172 bpm) significantly decreased over time in females. There was no signi ficant change in respiratory rate over time in males (R: 4-76 breaths/minute) or females (R : 4-56 breaths/minute). Rectal temperature significantly decreased throughout th e duration of anesthesia in both males and females. Time from medetomidine reversal until sternal r ecumbency was 38.6 38 minutes in males and 40.6 78.2 minutes in females. Eleven cats (11%) requi red a second dose of the selected combination of MKB to maintain an adequate plane of surg ical anesthesia and this was associated with significantly longer recovery times (62 20.7 minutes in males and 103.8 28.4 minutes in females). The selected dose of MKB was used to calculate a fixed volume to be used in all cats, regardless of true weight. Injection volumes of 0.7 mL and 0.8 mL of MKB were studied and proved to be ineffective at prov iding adequate anesthesia. Ther e were no perioperative deaths associated with this study. The selected dose of MKB fulfilled many of the demanding requirements associated with feral cat sterilization clinics, however, it was not possible to use a fixed volume, acceptable for use in all cats, regardless of true weight. The selected dose of MKB may be used more effectively in smaller clinics or settings in wh ich it can be dosed in a weight-specific manner.

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10 CHAPTER 1 INTRODUCTION Feral Cat Populations Feral cats are considered the wild offspring of domesticated cats; although a variety of alternate definitions exist. The classification of these animals is loosely defined and is often based upon opinion, rather than a universally a ccepted definition. So cialization status, recognition of ownership, and overall way life-style are often considered when defining a feral cat. The lines between loosely owned outdoor cats, tame strays, and feral cats are often blurred (Levy & Crawford 2004). Lack of consistency in terms of definition is further complicated by the idea that cats may change classification over time. Owned outdoor cats that wander or become lost may be considered stray. Stray cats that have lived an extensive amount of time in the wild may become untrusting of humans and be considered feral. Alternatively, a cat born in the wild, and deemed feral, may be adopted and over time become an acceptable companion animal. While the exact definition is undefined, fo r the purpose of this study, a feral cat is considered any free roaming cat th at does not have a rightful owne r, regardless of socialization status. While it is impossible to say with certainty, it is estimated that there are between 60 and 100 million feral and abandoned cats in the United States today (Jessup 2004). Cats are often depicted as independent or anti-social animals; however, feral cats are known to congregate around a stable food source, forming a colony (Mahlow & Slater 1996; Centonze & Levy 2002). Feral cat colonies vary in size, but are often dependant upon the availability of food (Mahlow & Slater 1996). Colonies are generally closed soci eties with members remaining their entire life; with replacement coming from births, immigra tion, and illegal abandonment (Wolski 1982; Levy

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11 et al. 2003). Human caretakers ma y provide food, a source of shelte r, and some veterinary care (Centonze & Levy 2002). In one study (Centonze & Levy 2002), 101 car etakers in north central Florida were surveyed in an effort to characterize 920 fera l cats and the people who cared for them. Most colonies were located on the care takers property and contained less than 10 cats. Most (91%) caretakers reported caring for their colonies out of sympathy, affection, or a sense of responsibility for hungry or injured animals. Nearly all caretakers provided a consistent source of food, while 75% provided she lter and 37% provided or were willing to provide veterinary care. Most of the caretakers surveyed believed the cats they cared for had an excellent or good quality of life, and while many we re too wild to be handled, they were still considered like pets. The Problem Feral cat colonies are often a s ource of controversy as their ri ght to exist is widely debated. Overpopulation of cats contributes to a variety of problems, resulting in heated arguments between people in favor of their survival, and those opposing it. While some feel these animals should be a focus of community effo rts to sterilize, vaccinate, and return them to the wild, others simply feel that eradication is a more definitiv e solution. This issue is further complicated by the lack of scientific data demonstrating the most effective control strategy. Discussions about feral cats are often emotionally charged and per ceptions based on persona l experiences often substitute for missing objective scien tific data (Stos kopf & Nutter 2004). Although public opinion, attitude and actions play a predomin ant role in the number of unwanted and abandoned animals, a domestic cat s high reproductive capacity creates additional problems. Free-roaming cats produce an average of 1.4 litters per year and have the potential to produce up to 3 litters per year (Stoskopf & Nutter 2004). Mean litter size of free-roaming cats

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12 reported in one study was 4.1 1.3 (Stoskopf & Nutter 2004). The overpopul ation and prolific breeding ability of feral cats is of concern regarding public healt h, impact on wildlife, and animal welfare. Public Health Considerations Although disease carried by feral ca ts is a concern for public health officials, its zoonotic impact is unknown. Several unanswered questio ns include the degree to which infections circulate within a population; whether or not cats maintain or amplify in fection after introduction from other reservoirs; and whether or not the existence of feral cat populations impact the likelihood of human exposure to pathogens (Case et al. 2006). Feral cats may be carriers of infectious diseases transmissible to humans and other animals. Toxoplasma gondii, Salmonella typhimurium, Escherichia coli and bacteria from the genera Rickettsia, Bartonella, and Coxiella; am ong others, are the causative agents responsible for numerous infectious diseases found in human s and domestic animals (Patronek 1998; Case et al. 2006; Dabritz et al. 2006). While the harborin g and transmission of these infections by feral cats is of concern, public health officials are prim arily concerned with the potential implications surrounding rabies. Rabies is a fatal infectious disease that is transmitted to humans by the bites of infected animals. Non-bite exposures also exist by mean s of scratches, abrasions, open wounds, or mucous membranes exposed to virus-containi ng saliva or other form s of infected tissue (Fearneyhough 2001). In the United St ates, rabies is primarily a disease that affects and is maintained by wildlife populations (Krebs et al. 2005). Feral cats are of concern because they are generally unvaccinated and may beco me infected from contact with wild animals. The fact that feral cats are commonly regarded as domestic an imals may, in itself, pose a serious threat. The Texas Department of Health re ported that rabid domestic animals expose 5 times as many

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13 people to rabies as the averag e infected wild animal (Clark 1988). Since the middle of the century, an average of one or two human rabies cases have been reported annually in the United States (Fearneyhough 2001). Transmi ssion of rabies by wild animals, primarily bats, has accounted for more than 85% of reported cases in the United States since 1976 (Krebs et al. 1997). In most other countries, dogs remain the ma jor species with rabies and the most common source of rabies transmission to humans (2003). An estimated 40,000 to 100,000 human deaths result worldwide from rabies (Rupprecht et al. 1995). While the incidence of rabies in freeroaming cats is not known, an increase in feline rabies cases in the Unit ed States, from 183 to 288, was reported in 1988 and 1995, respectivel y (Eng & Fishbein 1990; Krebs et al. 1996). During 2005, 49 states and Puerto Rico reported 6,417 cases of rabies in nonhuman animals and 1 case in a human being, representing a 6.2% decrease from th e 6,836 cases in nonhuman animals and 8 cases in human beings reported in 2004 (Blanton et al. 2006). Wildlife Vulnerability Whether or not feral cats pose a threat to native wildlife species is an undefined and controversial issue. The notion th at free-roaming cats are detrimen tal to wildlife populations is often accepted at face value due to limited studies and lack of definitive scientific proof. The debate surrounding feral cats and wildlife generall y centers on three ma jor issues: predatory behavior of feral cats on nativ e wildlife species, the notion that cats are an introduced species that should not be allowed to remain in the wi ld, and the concept that cats are viewed as a domestic species and it is societ ys responsibility to keep them confined for their protection, as well as the protection of ot her species (Slater 2004). Much of the evidence that implicates fera l cats as the source for extinction or endangerment of wildlife species come from studies conducted on islands (Girardet et al. 2001; Veitch 2001; Bester et al. 2002; Nogales et al. 20 04; Tantillo 2006). Cats have been introduced

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14 to remote islands off the coasts of New Zeal and, Australia, and South Africa where native wildlife evolved in the absence of predators (Patronek 1998). On many of these islands, cats were reported to have devastati ng effects on local species and we re even responsible for their extinction (Veitch 2001). Results from these st udies, however, have been inappropriately extrapolated to the United States, where the impact of feral cats on native wildlife species is not well documented or understood (Patronek 1998). Whether or not feline predation is detrimenta l to wildlife populations remains unclear in many parts of the world. Few studies accurately repor t feral cat predation a nd concisely relate it to detrimental effects on w ildlife (Tantillo 2006). Although st udies documenting the negative impact of feral cats on island ecosystems and thei r subsequent recovery following the removal of cat populations exist, many references of cat pr edation are unsupported by factual data (Coman & Brunner 1972; Girardet et al. 2001; Veitch 2001; Bester et al. 2002; Nogales et al. 2004; Tantillo 2006). In one study (Coleman et al. 199 7), a previously published best guess of the amount of birds killed by feral cats per year in Wisconsin was later self-cited in another publication and reported as res earch (Tantillo 2006). Examples such as these often go unnoticed, are cited by other author s, and are rarely critically evaluated (Tantillo 2006). The predatory behavior of feral cats has been reported largely based upon casual observations, perpetuated rumor, and speculation (B radt 1949). Even if carefully designed to be representative of the feline population, predation studies that rely on human observation and reporting are subject to a variety of bias (Pat ronek 1998). Tantillo points out several biases common to predation studies (Tantillo 2006). Fe cal analyses may only highlight the dietary habits of animals whose excremen ts are easiest to find. Similarly, stomach contents of deceased cats may correlate with the manne r and/or location of death. For example, cats killed by cars

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15 along roadsides may prey upon roadside species mo re than a normally dist ributed population of cats. Furthermore, few studies address whether or not predatory behavior by feral cats is considered additive, adding to a base level of predation and contributing to an increase in overall mortality; or compensatory, where cat predation replaces other forms of mortality and merely compensates for mortality that would happen anyway (Tantillo 2006). The uncertainty surrounding the impact or lack thereof, of feral ca t populations on native wildlife species is cause for concern for wildlife conservationists, ecolog ists, researchers, and feral cat activists. Although furt her evidence is needed to more clearly define the ambiguity and bias surrounding wildlife vulnerability, the topic remains an unresolved issue. Animal Welfare Feral cats are frequently considered a nuisa nce to society as they often exhibit noisy courting and territorial behavi or, fecundity, and urine spra ying by males. Despite these misgivings, a general concern for their welfare and way of life is rec ognized (Zaunbrecher & Smith 1993). High neonatal and juvenile mortality ra tes are reported for feral cats (Nutter et al. 2004). In one study, colony-based obse rvations found a kitten mortalit y rate of 48% three months following the initiation of the study, which contributed to a 75% cumulative kitten mortality rate at 6 months (Stoskopf & Nutter 2004). Kitten death was highly dependent upon environmental factors, but trauma accounted for most deaths in which cause could be confirmed (Nutter et al. 2004). In addition, feral cats, like wildlife, are su sceptible to every day threats including dogs, cars, humans, disease, starvation, and climate. Th e potential for suffering is a cause for concern and warrants a solution to end overpopulation and its negative effects on the welfare of feral cats. Current Methods of Control A variety of population control methods have been tried and are ongoing, however, none have proved to be the most obvi ous choice. Two management schemes, removal and trap-neuter-

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16 return (TNR), are strategies recognized in the at tempt to control feral cat populations. Traditional animal control, or capture and removal, is often limited by resources and is rarely successful in extensive cat populations (Andersen et al. 2004). The population ma nagement technique of trapneuter-return focuses on decreasing feral cat populations through steriliza tion as an alternative to conventional removal methods. Removal Methods Eradication in situ, removal for culling off-s ite, transferring to sanctuaries, and adoption are all examples of removal strategies employed in the quest to eliminate feral cat populations. Due to the magnitude of feral cat overpopulation, an effective control program must integrate environmental safety, affordabi lity, sustainability, and public aes thetics (Levy & Crawford 2004) Lethal eradication methods can be effective; ho wever, they often present logistical barriers that compromise environmental safety and put nontarget animals at risk (Veitch 2001; Bester et al. 2002). In addition, opposition is common as such removal techniques are often found unacceptable by the general public (Levy & Crawfo rd 2004). Introduction of disease, poison, and hunting are examples of lethal er adication strategies. A combination of such tactics has been employed on at least 48 islands with the firs t successful campaign taking place on Stephens Island, New Zealand, in 1925 (Nogale s et al. 2004). The majority of islands (75%, n=36) where eradication has been suc cessful are less than 5 km2 (Nogales et al. 2004). Th erefore, these results cannot be appropriately extrapol ated to larger islands and ot her mainland parts of the world where lethal eradication stra tegies may be considered. Trapping efforts are generally orchestrated near or at colony sites where cats are humanely captured. Cats considered feral, sick, or inju red may be culled, whereas socialized cats and kittens may be put up for adoption. While this appears to be the ideal solution, two problems exist within this strategy. Feral cats are naturally wary of unusua l conditions in their environment

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17 and may be reluctant to enter trap s even if they are baited (Nutte r et al. 2004). Therefore, total elimination is usually unsuccessful as several colony inhabitants will lik ely evade capture and ultimately repopulate the area (Mahlow & Slater 1 996). Feral cats are te rritorial animals and their highest potential for popula tion increase occurs when populat ions are low (Foley et al. 2005). This repopulation will likely attract immigrant cats and toge ther they will breed to fulfill whatever the environmental niche can support. Cat population size tends to increase until a carrying capacity is reached (Foley et al. 2005). While adoption is often considered the ideal outcome, an additional problem arises because there are simply not enough homes for the number of cats that need them. A proposed alternative to adoption is the creation of cat sanctuaries. Sanctuaries are ref uges for homeless cats that serve as permanent homes where they are provided fo r, however, many of these facilities fill to maximum capacity almost immediately after opening (Levy & Crawford 2004). Additionally, sanctuary cats are not guaranteed proper care nor are they ensu red a good quality of life (Slater 2004). The effectiveness of removal methods rely on a variety of factors that often limit the success of a particular strategy. Public oppositio n and environmental safety concerns prevent eradication from becoming a feasib le option in regard to populati on disposal. Similarly, removal by culling and adoption alone has proven to be in effective and inadequate (Neville & Remfry 1984; Mahlow & Slater 1996; Le vy & Crawford 2004). It has been shown that partially successful removal of feral cats produces a vacuum phenomenon in which population dynamics and territorial behavior encour age new animals to move into an unoccupied area (Zaunbrecher & Smith 1993; Patronek 1998; Gibson et al. 2002). Alternativ e strategies continue to be explored with the goal of reducing the pr oblem of feral cat overpopulation.

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18 Trap-Neuter-Return The newest approach in feral cat population management is tr ap-neuter-return (TNR). The concept of TNR was introduced in Denmark and E ngland in the 1970s and has spread in recent decades to the United States. Trap-neuter-re turn programs generally focus on unowned cats, being fed by caretakers, and are often considered more acceptable to the public than trap and destroy methods (Mahlow & Slater 1996). TNR i nvolves trapping, sterilizing, and then returning feral cats to their initial capture site. Some TNR programs offer additional amenities including vaccination, parasite control, retr oviral testing, and treatment of injury or illness. The primary goal of TNR programs is to reduce populations of feral cats, and therefore, their impact on society. The long term goal of TNR is often extinction of a colony through natural attrition. The deaths of sterilized animals wi ll ultimately result in a slow total population decline. A threetiered approach of incorporating euthanasia of sick or injured animals, adoption of socialized cats, and TNR is considered to be most eff ective (Levy & Crawford 2004). TNR programs serve to prevent the birth of new litters, reduce the threat of feline and zoonotic diseases through vaccination, and improve the qual ity of life for homeless cats (F oley et al. 2005). Most feral populations are at a capacity for av ailable resources (Gibson et al 2002). Reducing the birth rate decreases the competition for food and shelter, therefore increasing survivability. In addition, animal stress is reduced with less fighting and competition for mates (Gibson et al. 2002). There is a disagreement among veterinarians and members of animal protection groups about whether TNR programs should be discourage d, tolerated, or encouraged (Patronek 1998). While most advocates of TNR recognize its lim itations, opposition arguments include mainstay topics such as concerns over z oonotic diseases, wildlife vulnerabi lity, hidden costs of performing surgery, and the questionable quality of life follo wing release. Additionally, the question arises

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19 that if these animals are indeed considered wild, why should they be treated any differently than other wild animals (Mahlow & Slater 1996)? Ev idence that TNR is an effective method for controlling cat populations is sc arce (Zaunbrecher & Smith 1993; Levy et al. 2003). The concept of TNR has contributed to a decline in population over time when compared to control colonies in which cats are not neutered (Stoskopf & Nutte r 2004). Several studies deliver varying results, illustrating both the potential benefits and limita tions associated with TNR (Levy et al. 2003; Stoskopf & Nutter 2004; Natoli et al. 2006). One limitation associated with TNR is the time n ecessary for results to become evident. In Rome, Italy, 8000 cats were neutered over the sp an of 10 years and reintroduced into their colonies (Natoli et al. 2006). While a significant decrease in overall population was observed (16-32%), it was not noted until at least 3 years from the time of neutering. While a decrease was observed, it was indicated that th e results were not as great as originally hoped for. Immigration due to abandonment and spontaneous arrivals we re found to be 21% in this study, offsetting the decrease from sterilization, and it was c oncluded that without proper education on overpopulation and abandonment. Similar to the findings of Natoli and Mara gliano, new arrivals as a result of illegal abandonment may hinder the success of a TNR progr am. One study revealed that the presence of highly visible, well-fed, establis hed feral colonies encouraged illegal desertion of pet cats (Castillo & Clarke 2003). While TNR was show n to decrease the orig inal population, the population at the end of the study was observed to in crease as a result of illegal abandonment. This phenomenon is thought to be the result of cat owners desperate attempts to give the cat a chance, as opposed to relinquishment to an animal shelter, where high rates of euthanasia exist (Levy & Crawford 2004).

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20 Conversely, the effects of TNR have also b een shown to substan tially reduce populations of feral cats. In Randolph County, North Carolin a, USA, a study used 9 managed colonies to assess reproductive parameters in feral cats (Stoskopf & Nutter 2004). Of the 9 colonies, 6 participated in a TNR program. The remaining 3 colonies did not participate in a TNR program and were used as control groups. Of the surgic ally sterilized colonies, all 6 decreased in population (mean decrease of 36%) and continued to d ecline within the first 2 years. In the same 2 years, the remaining 3 control colonies, which were not steril ized, were found to increase in number by 47%. The study concluded that TNR may br ing feral colonies to extinction, but is not a rapid solution. Similarly, an 11-year study at the University of Central Florida (USA) found TNR to be highly successful at reducing the number of feral cats amongst se veral populations (Levy et al. 2003). Between 1991 and 1995 an original group of 155 study cats were sterilized, with the exception of 1 male cat. While records were not kept prior to 1991, observe rs estimated the cat population on campus may have reached 120 cats. St erilization and adoption of socialized cats reduced the population to 68 by 1996 and only 23 cats remained on campus at the end of the study in 2003, representing a 66% reduction. Additionally, no known kittens were observed to be born on campus after 1995. The study conclude d that long-term reduction of feral cat populations is feasible by TNR. A separate study in north central Florida (USA) distributed a written survey to feral colony caretakers who participated in a local TNR Program (Centonze & Levy 2002). The survey reported 132 colonies being cared for with a total of 920 cats. At the time of the completed survey, caretakers had participated in monthly sterilization clinics for 1 to 9 months. Most colonies contained less than 10 cats with the la rgest colony containing 89 cats. The mean colony

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21 size before participation in monthly steriliza tion clinics was 7 cats. The mean colony size following participation in a TNR program was 5. 1 cats. Within less than one year of TNR participation, average colony size decreased by 27%, while the largest colony was observed to decrease in numbers from 89 to 24 cats. In co nclusion, implementation of TNR was determined to decrease colony size and the number of cats overall, from 920 to 678, as a result of death, disappearance, adoption, and the prevention of new births. In addition to halting reproduction, TNR has also been reported to offer additional benefits. One study reported improved body condition of feral cat s 1 year after sterilization surgery (Scott et al. 2002). Body weight, body condition scoring (BCS), and falciform fat pad measurements were used to determine changes in feral ca t body conditions before a nd after sterilization. Reported scores indicated more than half of feral cats were less than the ideal weight prior to surgery. Cats were found to increase in mean bo dy weight by 40% and scored 1 point higher on the BCS scale (1-9) 1 year follo wing participation in a TNR program. In addition, caretakers reported a decreased tendency to roam followi ng neutering. Fighting amongst cats was also observed to decrease fo llowing sterilization. The Gillis W. Long Hansens Disease Center, a federal research facility and hospital located in Carville, Louisiana, USA, was the si te of a well-established feral colony (Zaunbrecher & Smith 1993). In response to noise and odor compla ints by hospital residents and staff, trap and removal methods were employed without success. A TNR study was designed and initiated. The colony was regarded as a nuisance prior to th e study and implementation of TNR. After the initiation of the TNR program, not only was the p opulation found to stabili ze, but overall health and body condition was found to improve and compla ints about territorial behavior and noise decreased. The overall attitude toward the feral cats had also changed. After participation in the

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22 TNR program, cats attained a certain amount of status evoking a protective and possessive behavior from both patients and staff. The TNR pr ogram also incorporated the participation of several hospital patients that ha nd-delivered 18 cats to partak e in the study, indicating support and endorsement for the project. Patients and sta ff soon regarded the feral cats as pets. TNR was determined to be effective, economically feas ible, and a humane solution to the once negative attitude towards the colony. In th is particular example, not only did colony health improve, but the overall attitude and approach to the colony was increasingly positive. While it may not embody the gold standard for pe t cats, TNR offers an alternative way of life for feral cats. TNR programs offer the opportun ity for feral cats to live a good quality of life for an extended period of time as their popula tion is diminished by way of adoption, natural attrition, and the prevention of new births. Nonsurgical Contraception Alternatives to surgical sterilization programs, using pharmacaceutical or immunological methods, are currently under inve stigation for use in feral cats. One example of non-surgical contraception is chemical castra tion, in which intratesticular or intraepididymal injections of a chemical agent (4.5 % solution of chlorhexidine digluconate) are used to cause infertility in males (Kutzler & Wood 2006). Similarly in females, mechanical barriers, such as intravaginal and intrauterine devices, can be implanted to disrupt fertility. (Kutzler & Wood 2006). Additionally, hormonal treatments, including prog estins, androgens, or analogs of gonadotropin releasing hormone (GnRH) act e ither directly or indirectly to block reproductive hormonemediated events and concep tion (Kutzler & Wood 2006). Recently, the concept of immunocontraception has been investigated for a nonlethal and nonsurgical approach to controlling feral cat pop ulations (Levy et al. 2004; Kutzler & Wood 2006; Purswell & Kolster 2006). Immunocontracepti on, via vaccination against GnRH, uses the

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23 immune system to block fertility (Purswe ll & Kolster 2006). While immunocontraception is promising, there are also some drawbacks. In addi tion to finding the most appropriate antigen for a vaccine, appropriate delivery systems have proven to be a challenge. Oral vaccine baits raise the concern for non-target species and the implications of introducing a widely distributed oral contraceptive vaccine into the environment (Purswell & Kolster 2006). Additionally, animals generally require a series of immunizations fo r adequate immunity, some of which fail to respond and remain fertile (Levy et al. 2004). In order to be considered effective, immunocontraception vaccines for feral cats requir e long-term immunity for a large population, achieved with a single treatment, eliminating the need for repeat vaccines (Purswell & Kolster 2006). While progress continues to be made, the development of non-surg ical contraceptive strategies are complex and slow. Therefore, the use of surgical steri lization and TNR programs must be retained, at least for the pres ent time, to control feral cat populations. Operation Catnip: A Trap-Neuter-Return Program Operation Catnip is a non-profit organization that holds monthly feral cat sterilization clinics at the University of Floridas College of Veterinary Medicine. Cats are presented the morning of each clinic confined in humane, wire mesh traps. Upon arrival, cats are assigned an identification number. After being an esthetized, cats encounter a seri es of stations in preparation for surgery. Eyes are lubricated, bladders are ex pressed, injectable antibiotics are administered, and appropriate surgery site prep aration is performed. Af ter sterilization is complete, all cats are vaccinated against feline rabies, feline leukemia vi rus, feline panleukopenia virus, herpes virus, and calicivirus. In addition, they receive topical treatment with se lamectin for parasite control. The tip of the left ear is removed to permanently identify sterilized cats.

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24 Operation Catnip is considered a high-volume steri lization clinic, av eraging between 100 and 200 surgeries at each monthly clinic. The largest clinic to da te sterilized 230 feline participants. Each clinic is completed in a matte r of hours and is comprise d solely of volunteers, students, clinicians, and surge ons. In 2006, Operation Catnip ster ilized 3,725 feral cats (Scott 2007). Challenges of Working with Feral Cats The challenges associated with feral cats include a variety of obstacles in regards to their capture and sterilization. Trapping is relatively easy and requires lit tle to no training in order to safely transport and present feral cats for ster ilization; however, some feral cats may evade trapping attempts. Providing an acclimation period to traps prior to capture may prove beneficial to colonies not used to human contact or part icularly trap-shy cats. Additional methods are available, but are not practical as they require ex perience or the participati on of a veterinarian; an example being net capture or sedati ve-laced food (Nutter et al. 2004). Once trapped, feral cats pres ent a unique problem because these animals, similar to wildlife, cannot be safely handled while conscious. Therefore, feral cats must be anesthetized within their traps. Anesthesia presents additi onal challenges in regard to administration. Feral cats are usually of unknown weight, age, and health status, which are influential in choosing any anesthetic regime. Similarly, unknown factors such as injury or illness may influence or even compromise the safety of anesthesia. An anesthet ic protocol to be used in feral cats must consider the safety of both the handlers and the animals. Properties of an Ideal Anesthetic Injectable anesthetics permit immobilization while cats are confined within their traps, eliminating the potential for escape or contact with conscious animals that may prove to be dangerous. Intramuscular inject ions are the most efficient route of administration when

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25 anesthetizing feral cats. An ideal anesthetic regime to be used in feral cats would be predictable, reliable, and offer a wide margin of safety. It would be suitable for both males and females of any age and physical condition. In addition, it woul d provide rapid onset, sufficient duration of surgical anesthesia, rapid return to normal function, and adequate pos t-operative analgesia. Injectable anesthesia for use in feral cats also requires consideration of the injection volume. Ensuring a complete and accurate injection for feral cats restrained within their traps is difficult because restraining optio ns are limited and often ineffi cient. Large drug volumes pose the risk of incomplete administration because cats may move upon injection. A small volume increases the likelihood for complete administration. Feral Cat Anesthesia: Shortcomings of Current Methods The current anesthetic protoc ol used in Operation Catnip is an injectable combination of tiletamine, zolazepam, ketamine, and xylazine (TKX) given intramuscularly. TKX is considered an acceptable injectable anesthetic for use in fera l cat sterilization and importantly, is associated with a low (0.35%) perioperative mortality rate (Williams et al. 2002). However, TKX possesses several limitations that have prompted the sear ch for an alternative injectable anesthetic. Shortcomings include oxygen saturation levels that are below accepted values, prolonged recovery times, postoperative hypothermia, and likely inadequate pos t-operative analgesia (Cistola et al. 2004). Tiletamine is a dissociative anesthetic, ch emically related to ketamine. It provides analgesia and immobilization in a dose-depende nt manner (Lin et al. 1993). Zolazepam is a benzodiazepine and provides muscle relaxation (L in et al. 1993). Tiletamine and zolazepam are combined in a 1:1 ratio by mass and marketed under the trade name, Telazol (Fort Dodge Animal Health, Fort Dodge, IO, USA) (Lin et al. 1993). Telazol is not considered a good

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26 combination for maintenance of anesthesia be yond its initial dose, as recoveries may be prolonged and the actions of zol azepam may outlast those of tilet amine (Pascoe 1992). This is a problem because the animal experiences a great er degree of tranquilization than anesthesia during recovery (Plumb 2005). Xylazine is used as a sedative analgesic and also provides good muscle relaxation and is approved for use in the dog and cat in the United States. Xylazine may cause significant cardiovascular depressa nt effects (Paddleford & Harvey 1999). At the same inspired oxygen concentration, th ere is a tendency for arterial oxygen tensions to be less during general an esthesia than observed while conscious (McDonell 1996). Hemoglobin oxygen saturation (SpO2) > 95% is considered normal and SpO2 < 90% (defined as a PaO2 of < 60 mmHg) equates to serious hypoxemia (T hurmon et al. 1996). In cats anesthetized with TKX, SpO2 levels averaged 92 3% in males and 90 4% in females (Cistola et al. 2004). SpO2 levels were also found to dr op below 90% at least once in mo st cats (Cistola et al. 2004). TKX does not require animals to be intubated and room air (Fi = 0.21) is inspired. This is likely a contributing factor to low oxygen saturation levels seen in cats anesthetized with TKX. While low oxygen saturation is easily preventable and tr eatable, it is not feas ible to administer supplemental oxygen to all cats pa rticipating in Operation Catnip because equipment is limited and up to 50 cats may be anesthetized at one time. The exact repe rcussions of low SpO2 levels in cats anesthetized with TKX are unknown, but prom pt the search for alternative methods of anesthesia. Prolonged recoveries are often seen with the us e of TKX in cats. The sedative effects of xylazine last 1-2 hours, but complete recovery may take 2-4 hours (Paddleford & Harvey 1999). After surgery is complete, the effects of xylazine may be reversed using one of its antagonists, yohimbine. However, the time from reversal to sternal recumbency has been reported to be

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27 prolonged (72 42 minutes) in ca ts anesthetized with TKX (Cistola et al. 2004). The low specificity of yohimbine as an antagonist to xyla zine may contribute to prolonged recovery times (Virtanen et al. 1989). One side effect of Telazol is hypothermia (Plumb 2005). Normal body temperature for cats ranges from 37.8-39.5C (100-103.1F) (Plumb 2005). Cats administ ered TKX were reported to be hypothermic with temperatures dropping as low as 36.6 0.8C (97.8 1.4F) postoperatively (Cistola et al. 2004) Clinical hypothermia is associ ated with decreased liver and renal blood flow, resulting in reduced liver metabolism and renal excretion (Posner 2007). Subsequently, hypothermia-induced slowed metabolism of anesthetic drugs may account for prolonged recovery times seen in cats anesthet ized with TKX. Another complication resulting from hypothermia is CNS depression, which may pot entiate the effects of anesthetics and muscle relaxants (Short 1987). Additionally, hypothermic animals often shiver during recovery, increasing their metabolic requirements for oxygen. In humans, shivering in recovery is reported to be unpleasant (Kumar et al. 2005). Feline post-operative pain has been under treated largely as a resu lt of fear of side effects and lack of suitable pharmaceutical products (R obertson & Taylor 2004). It has been reported that cats undergoing ovariohysterectomy that are not provided with analgesics have more postoperative pain than cats that receive anal gesics (Slingsby et al. 1998). While xylazine and ketamine may offer analgesic properties, TKX does not contain a recognized analgesic and therefore, post-operative pain control is likely inadequate. Du e to the inadequacies surrounding TKX, alternative anesthetic regimes are desired.

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28 Proposed Drug Combination A combination of medetomidine, ketamine, and buprenorphine (MKB) has been proposed for use in feral cat sterilization surgery. Similar to TKX, this combination of drugs is combined and administered intramuscularly as a single injection. Medetomidi ne and its specific antagonist, atipamezole, are highly specific for alpha2 adrenoceptors. Ketamine is classified as a dissociative anesthetic, offering a state of unconsciousness and somatic analgesia. Buprenorphine is an opioid analgesic used in pain management. It is hypoth esized that the MKB co mbination may eliminate some of the inadequacies associated with TKX. Alpha2-Adrenoceptors Adrenergic drugs affect receptors stimulate d by norepinephrine or epinephrine. These drugs can act directly on the re ceptor (adrenoceptor or adrenoreceptor) by activating it, blocking neurotransmitter actions, or interrupting the rel ease of norepinephrine. Norepinephrine releasing neurons are found in the central and sympathetic nervous system where they serve as links between ganglia and effector or gans (Howland & Mycek 2000). Adrenoceptors can be distinguished pharmacol ogically and are divided into two families, alpha ( ) and beta ( ). Alpha adrenoceptors are further subdi vided into several classes, including alpha1 and alpha2, based on relative affinities for agonist s, independent of their anatomical location (Berthelsen & Pettinger 197 7; Wickberg 1978; Wikberg 1978). Alpha2-adrenoceptors have been isolated in the central nervous sy stem, gastrointestinal tract, uterus, kidney, and platelets and produce a variety of effects (Pad dleford & Harvey 1999). Pharmacologic studies have revealed alpha2-adrenoceptors to be locate d in either pre-synaptic or post-synaptic positions (Cullen 1996). Alpha2-adrenoceptors located in the central nervous system regulate the neuronal release of norepinephrine and several other neurot ransmitters that are intimately involved in the modulation of sympathetic outflo w, cardiovascular and endocrine function, vigilance, emotion,

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29 cognition, and nociception (Scheinin & MacDonald 1989). In most cell types, but not all, alpha2-adrenoceptors regulate adenylate cyclase activity. Specifically, they are linked to a guanine nucleotide regulatory protein (G-prote in), whereby receptor activation results in inhibition of adenylate cyclase act ivity and cAMP formation in target cells (Fain & Garcia-Sainz 1980). This leads to the inhibition of further release of norepine phrine from the neuron. When a sympathetic adrenergic nerve is stimulated, rel eased norepinephrine crosse s the synaptic cleft, interacting with alpha1 receptors. A portion of the released norepinephrine circles back and reacts with alpha2 receptors on the neuronal membrane. The stimulation of the alpha2 receptor results in feedback inhibition for continued norepinephrine release from the stimulated adrenergic neuron. This inhibito ry action decreases further output of the neuron and serves to reduce sympathetic output when sympathetic activity is high (Howland & Mycek 2000). Adrenoceptors are a natural target for the develo pment of sedatives and an esthetics because their activation leads to reduced norepin ephrine release and locus coeruleus activity, a site in the brain containing many norepinephrine rel easing neurons (Stenberg et al 1993). Norepinephrine is a neurotransmitter required for a variety of physiol ogical effects and is nece ssary for the mediation of arousal and pain (Paddleford & Harvey 1999) If norepinephrine is blocked, the result is sedation and analgesia (Paddleford & Harvey 1999). Activation of alpha2-adrenoceptors by specific agonists offer profound sedative-anesthetic e ffects in a variety of sp ecies (Scheinin et al. 1987). Medetomidine Medetomidine is one of the newer sedative drugs approved for veterinary use. It is classified as an adrenergic alpha2-agonist (Cullen 1996). Intended for use in dogs and cats, it provides predictable and dose-dependant seda tion and analgesia, mediated by receptor stimulation in the spinal cord and brain (Cul len 1996). Medetomidine is lipophilic and rapidly

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30 eliminated (Paddleford & Harvey 1999). Its alpha2 to alpha1 receptor selectivity binding ratio is 1620, compared to 160 for xylazine (Virtanen 1989). Alpha2 agonist drugs bind to alpha2adrenoceptors, altering their natural membranes and preventing the release of neurotransmitters (Paddleford & Harvey 1999). Mede tomidine induces sedation and analgesia, and in high doses, has anesthetic properties (Savola et al. 1986; Virtan en et al. 1988). It has been shown to induce change in metabolites of various transmitters resulting in their decreased release, metabolism, and turnover (Virtanen et al. 1988). A clinical evaluation by seven veterinary clin ics in Finland determined the recommended dose of medetomidine to be be tween 50-150 g/kg for various clin ical procedures in cats in which sedation was needed (Vaha-Vahe 1989a). Doses ranging between 80 and 110 g/kg were used for examinations, clinical procedures, and minor surgical operations in cats (Vaha-Vahe 1989a). The preferred route of administration was intramuscular injection (Vaha-Vahe 1989b; Vaha-Vahe 1989a). Cats administered 10 g/kg of medetomidine show stupor-like sedation with loss of reflexes (Stenberg et al. 1993). Seda tion for up to 90 minutes and analgesia for 20-50 minutes is reported with 80 g/kg (Vaha-Vahe 1990). Medetomidine has been shown to reduce dose requirements for other anesthetics in animal s when used concomitantly (Segal et al. 1988). An advantage of medetomidine is that the sedativ e and depressant effects associated with it can be fully and rapidly reversed with its specific anta gonist, atipamezole. Medetomidine: Cardiovascular and Respiratory Effects Medetomidine produces marked changes in th e cardiovascular system, mostly through stimulation of central receptors, increasing va gal tone and decreasi ng sympathetic activity, resulting in bradycardia a nd hypotension (Cullen 1996). The autonomic nervous system, under control by the central nervous system, is the prin cipal means by which heart rate is controlled (Berne et al. 2004). Drug lipophilicity is a major determinant of the rate of diffusion across

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31 biological membranes (Gaynor & Muir 2002). Medeto midine is highly li pophilic and therefore, its ease of penetration into the central nervous system is reflected by its rapid onset of cardiovascular effects (Savola 1989). After medeto midine administration, peripheral vascular resistance increases due to alpha2 adrenoceptor-mediated events (Paddleford & Harvey 1999). Stimulation of postsynaptic r eceptors located in venous and arterial walls results in vasoconstriction, whereas stimulation of presynaptic receptors inhibits norepinephrine release, reducing sympathetic tone, and contributing to bradycardia (Ruffolo 1985). In cats, medetomidine induces a biphasic effect on blood pressure by incr easing it transiently before a decrease to pre-injection control values or less is seen. Heart rate decreases immediately following injection (Savola et al 1986; Savola 1989). Prior admini stration of atropine did not eliminate the hypotensive or bradycardic actions associated with medetomidine, nor was it found to modify the initial hyperte nsive phase (Savola 1989). Medetomidine consistently produces marked bradycardia in cats and heart rate ma y decrease by as much as 50% of pre-injection values (Vaha-Vahe 1989b; Vaha-Vahe 1989a; Cu llen 1996). Cats administered 20 g/kg of medetomidine IM showed a 58% decrease in he art rate from baseline values 15 minutes following administration (Lamont et al. 2001). Mede tomidine-induced changes in heart rate are primarily due to centrally mediated effects a nd peripheral receptor st imulation; there is no evidence for a direct action of alpha2 agonists on heart musc le (Day & Muir 1993). Medetomidine has been reported to cause a decrease in arterial PaO2 in cats (Duke et al. 1994). Venous desaturation also occurs and is likely the result of increased tissue oxygen extraction associated with decreased cardiac output (Gaynor & Muir 2002). Medetomidine depresses the respiratory center, decreasing sensitivity to increases in PaCO2 (Muir et al. 2000).

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32 When large doses of medetomidine are admi nistered, the respiratory threshold for PaCO2 values increase, resulting in marked respir atory depression (Muir et al. 2000). Medetomidine: Side Effects The other most common adverse effects observe d clinically with the use of medetomidine are vomiting, muscle twitching, and hypothermia (Cullen 1996). In one study of 678 cats, 65% vomited after IM administration of medetomi dine, using doses ranging between 80-100 g/kg (Vaha-Vahe 1989b). In addition, pa le mucous membranes are ofte n witnessed as a result of medetomidines profound vasoconstrictive eff ects (Muir et al. 2000). Inhibition of gastric secretions have also been reported with the use of medetomidine (Cullen 1996). Atimpamezole A major advantage of the use of alpha2 agonists, like medetomidine, is that specific antagonists have been developed to fully revers e their physiological eff ects. Atipamezole is a potent alpha2 antagonist and is the most selective drug currently available for clinical use in veterinary anesthesia (Paddl eford & Harvey 1999). Its alpha2 to alpha1 receptor specificity is 8526, compared to 40 for yohimbine, and it has virtua lly no effect on other receptors (Virtanen et al. 1989). Atimpamezole has been shown to effectively antagonize the cardiovascular, respiratory, gastrointestinal, and hypothermic effects of medetomidine (Savola 1989; Cullen 1996). In one study, mean arterial pressure and he art rate values were completely restored following administration of atipamezole duri ng maximal hypotensive a nd bradycardic phases induced by medetomidine (Savola 1989). In dogs, a transient decrease in m ean arterial pressure of between 8% and 20% was found after intramus cular injection of atipamezole (Vainio 1990). In cats, the most effective dos e of atipamezole was found to be 2-4 times (on a mg basis) the medetomidine dose administered IM (Cullen 1996). Atipamezole can be administered intravenously, intramuscularly, or subcutaneously a nd its half-life is twice that of medetomidine,

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33 minimizing the risk for sedation relapse after at ipamezole administration (Paddleford & Harvey 1999; Bollen & Saxtorph 2006). Atipamezole revers es the undesirable de pressant effects of medetomidine and is useful for rapidl y returning animals to normal function. Atipamezole: Side Effects Adverse effects accompanying atipamezole reve rsal of medetomidine include urination, salivation, and muscle tremors (Vaha-Vahe 1990). Extremely hi gh doses may induce signs of CNS stimulation, extreme excitement, pant ing, and vomiting (Paddleford & Harvey 1999). Following IV administration, tachyc ardia and hypotension have occu rred and therefore slow IV or IM administration is recomm ended (Paddleford & Harvey 1999). Dissociative Anesthesia Dissociative anesthesia derives its name from its unique ability to simultaneously depress one area of the central nervous system, while stimulating another (Evans et al. 1972). Dissociative anesthetics produce uni que effects in which animals are assumed to feel dissociated, or apart, from their body (Bill 2006). It is this effect that allows dissociative drugs to provide analgesia and anesthesia without disrupting vital physiological f unctions (Evans et al. 1972). One advantage to using dissociative anesthesia in cats is that their airway remains patent, eliminating the need for endotracheal intuba tion (Beck et al. 1971). Dissociat ive anesthesia differs further from other anesthetics in that its use often re sults in emergence reactions and hallucinatory behavior, unlike sluggish recoveri es characteristic of most ot her agents (Wright 1982). These reactions are thought to be the result of CNS over stimulation. The consequences of feline hallucinations are not known, but post-anesthetic personality changes have been reported (Haskins et al. 1975).

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34 Ketamine Ketamine hydrochloride is classified as a shor t-acting dissociative anesthetic that is used for chemical restraint, anesthes ia induction, and surgical anesth esia in cats (Saywer et al. 1993). It is a rapid-acting general anesthetic that has significant analgesic activity and lacks cardiopulmonary depressant effects (Plumb 2005). In the past, ketamine has been recommended for most surgical procedures in cats, incl uding abdominal surgery (Evans et al. 1972). The functional disorganization associated with ketamine is the reason for its classification as a dissociative (Hanna et al 1988). Ketamine is a non-comp etitive N-methyl-D-aspartate (NMDA) receptor antagonist (Thurmon et al. 1996) By inhibiting NMDA receptors, it is thought that ketamine may prevent nociceptive stimul ation (Woolf & Thompson 1991). While its exact mechanism remains unclear, ketamine induces anesthesia by selectively interrupting CNS reactivity to various sensory impul ses, without blocking sensory i nput at spinal or brain stem levels (Wright 1982). This mechanism is unique as most anesthetic prope rties cause complete CNS depression. After injection, patients enter a cataleptic state, similar to a trance, in which loss of voluntary motion and muscle rigidity are often s een (Evans et al. 1972). Lack of complete muscular relaxation makes ketamine unsuitable as a sole anesthetic agent (Bill 2006). In cats, ketamine only provides loss of clinical reaction to pain during its maximal effect (Haskins et al. 1975). Additional doses of ketamine do not e nhance muscle-relaxing effects, but do prolong recovery (Arnbjerg 1979). Recommended doses vary depending on de sired depth of anesthesia, route of administration, and the use of othe r anesthetics concomita ntly. In cats, ketamine can be given in doses ranging from 2-33 mg/kg, although doses of 50 mg/kg have been used without fatalities (Arnbjerg 1979; Wright 1982). Ketamine produ ces dose-related unconsciousness and analgesia

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35 with a rapid onset of action (Thurmon et al. 1996). Following intram uscular injection, cats become recumbent in 1 to 8 minutes (Lumb & Jones 1973). After intramus cular injection, peak drug levels occur within approximately 10 minutes with the hi ghest concentrations found in the brain, liver, lung and fat (Plumb 2005). Duration of anesthesia is approximately 30 to 45 minutes (Lumb & Jones 1973). In one study, small doses (4 and 8 mg/kg) of ketamine caused slow induction times and produced circulatory stimula tion, catatonia, and bizarre behavior. Larger doses (32 and 64 mg/kg) caused circulatory de pression, respiratory depression, and prolonged recovery times (Child et al. 1972). Ketamine is excreted in the urine and a cat s reduced ability to excrete the drug due to compromised renal function may prolong recovery (Haskins et al. 1975). Ketamine is rapidly biotransformed to its only known metabolite, norketamine, in the cat (Chang & Glazko 1974; Heavner & Bloedow 1979). The elimination half-life of ketamine in the cat is approximately 1 hour (Plumb 2005). Recovery from symptoms asso ciated with ketamine may not be complete within 10 hours, but most cats can stand una ssisted within 2 hours (Evans et al. 1972) Ketamine offers many advantages. The route of administration is ve rsatile as it can be administered subcutaneously, intravenously, intr amuscularly, orally, and rectally (Wright 1982; Hanna et al. 1988; Wetzel & Ramsay 1998). Additi onally, ketamine may aid in the prevention of post-operative pain as it has shown to exhibit weak visceral analge sic properties (Saywer et al. 1993). Finally, ketamine has gained favor for use in animal surgical procedures because of its apparent lack of depressant effects on the card iovascular and respiration systems when used in small doses (Child et al. 1972; Haskins et al. 1975) Ketamine: Cardiovascular and Respiratory Effects Ketamine stimulates the heart and lacks th e depressant effects prevalent in other anesthetics (Wright 1982). The effects of keta mine on the cardiovascular system include

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36 increased cardiac output, heart rate, mean aortic pressure, pulmonary artery pressure, systemic arterial blood pressure, and central venous pressure (Wong & Jenkins 1975; Plumb 2005). An increase in heart rate and blood pressure has been reported in a clinical setting, but the increase in heart rate is not propo rtional to the dose of ketamine given (Arnbjerg 1979). Ketamine causes dose-dependent respirat ory depression (Wright 1982). Apneustic breathing is defined as sustained tonic contraction of the respiratory muscles, resulting in prolonged inspiration. Ketamine is capable of in ducing an apneustic respiratory pattern, and may be the result of its ability to alter the functi onal organization of the respiratory controller (Pokorski et al. 1987). Respiratory rates and/or tidal volumes were decreased by ketamine in cats and occasionally transient apnea has been reported (Wright 1982). Ketamine: Side Effects Ketamine has a pH of 3.5 and tissue irritation may occur during intramuscular injection as a result of its acidic properties (Wright 1982). Pedal reflexes remain intact and purposeless movements, of varying degree, are often seen unre lated to specific noxious stimuli (Evans et al. 1972). Cats eyes remain open after ketamine admi nistration and need to be protected with an ophthalmic lubricant (Plumb 2005). Reduced body temp erature may be seen with high doses of ketamine (Arnbjerg 1979). Body te mperatures decrease on average 1.6C after therapeutic doses (Plumb 2005). Due to its dissociative effects, hallucinatory behavior may be observed during emergence from ketamine anesthesia (Thurmon et al. 1996). Cats should be placed in areas with little visual or auditory stimulation to aid in a smoother recovery. Additional emergence reactions include ataxia, increased motor activity, sensitivity to touch, avoidance behavior of an invisible object, and violent rec overy (Plumb 2005). Sialorrhea, or excessive salivation, is also commonly seen with ketamine use (Evans et al 1972). Most cats recover from these symptoms within several hours without fu rther reoccurrence (Wright 1982).

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37 Medetomidine and Ketamine Combination There are a number of reports using a combina tion of medetomidine and ketamine in cats for anesthetic purposes (Verstegen et al. 1989; Verstegen et al. 1990; Verstegen et al. 1991a; Dobromylskyj 1996; Wiese & Muir 2006). Used in combination, the centrally stimulating effects of ketamine have been reported to ba lance the depressive effects of alpha2-agonists (Verstegen et al. 1991a). The tendency for ketamine to increase heart rate may assist in counteracting negative cardiovascular effects associated with me detomidine (Verstegen et al. 1991a). In cats, the use of medetomidine (80-100 g/kg) with a low dose of ketamine (7 mg/kg) proved to be sufficient for short acting (20-40 minutes) surgical anesthesia (Vaha-Vahe 1989b). Verstegen et al (1991) found that medetomidine ( 80 g/kg) greatly potentiated the effects of low doses (5-7.5 mg/kg) of ketamine, providing su itable surgical anesthesia for 59 minutes. Intramuscular administration of medetomidine (80 g/kg) combined with ketamine at doses of 2.5, 5, 7, 7.5 and 10 mg/kg produced anesthesia in less than 4 minutes and the duration ranged between 36 and 99 minutes, dependent upon the dos e of ketamine (Verstegen et al. 1990; Verstegen et al. 1991a). When increasing the dose of ketamine from 2.5 to 10 mg/kg, the duration of anesthesia was significantly extend ed (Verstegen et al. 1991a). Although the duration of action was found to be closely related to the do se of ketamine, the qual ity of anesthesia was similar in all groups. Verstegen and ot hers reported the advantages of the medetomidine/ketamine combination over that of the xylazine/ketamine combination to be the need for a lower dose of ketamine, a longer duration of action, and better analgesia (Verstegen et al. 1990). It was concluded that medetomidine co mbined with low doses of ketamine forms a suitable combination for anesthesia in cats.

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38 Medetomidine and Ketamine Combination: Cardiovascular and Respiratory Effects Bradycardia in cats is evident with medeto midine/ketamine combinations. In one study, varying doses of ketamine were combined with 80 g/kg of medetomidine and evaluated. When the dose of ketamine was increased from 2.5 to 10 mg/kg a change from bradycardia to mild tachycardia was observed (V erstegen et al. 1991a). In the same study, additional anesthetic drug combinations were evaluated, including combining ketamine with acepromazine or xylazine. Bradypnoea was seen in all groups receiving ketamine, regardless of it s anesthetic pairing (Verstegen et al. 1991a). Verstegen et al (1990) observed no respiratory depression in cats anesthetized with 80 g/kg of medetomidine and 5 mg/kg of ketamine (Versteg en et al. 1990). However, peri ods of apnea were observed in cats anesthetized with 80 g/kg of medetomidine and 10 mg/kg of ketamine (Verstegen et al. 1991a). Medetomidine and Ketamine Combination: Side Effects The most common side effects seen with the concomitant use of medetomidine and ketamine are vomiting, excitability, and apnea (V erstegen et al. 1990; Ve rstegen et al. 1991a). Analgesia NSAIDS Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in pain management in both humans and animals as they are easy to admi nister, inexpensive, o ffer a long duration of action, and are not controlled s ubstances (Papich 2000). NSAIDs, however, are not widely used in cats due to potential toxic effects. Due to their deficiency of certain metabolic pathways, particularly hepatic glucoroni dation, cats are prone to decreas ed NSAID metabolism (Lascelles et al. 2007). This prolongs the duration of eff ect and may ultimately result in drug accumulation. Slow clearance may result in hyperthermia, metabolic acidosis, and kidney or liver injury (Davis

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39 & Donnelly 1968). Severe adverse e ffects associated with NSAIDs also include gastrointestinal ulceration, perforation, and bleed ing or renal ischemia (Pap ich 2000). NSAID use should be based on confirming normal renal function prior to use; and doing so in feral cats is not feasible. Hypotension during anesthesia can contribute to the renal toxicity of NSAIDs and blood pressure is rarely measured during feral cat procedur es. Additionally, dehydration due to trapping may make some cats more susceptible to NSAID toxicity. Because fera l cats do not participate in follow up examinations post-operatively, NSAID us e is inappropriate. A lternative methods of pharmacologic analgesia should be sought for use in feral cats. Opioids Opioids are defined as any natural or syntheti c drug that produces an algesia without loss of proprioception or consciousness (Gaynor & Mu ir 2002). An important advantage for opioid analgesics is that they can be administered wit hout fear of the potential side effects associated with NSAIDS (Papich 2000). Opioid drugs are highly effective and remarkably safe (Papich 2000). They are generally characterized by rapid and extensive distribution as they are highly lipophilic drugs (Papich 2000). Opioids exert their effects by interaction with opioid receptors located on cell membranes and are currently one the most effective systemic means of controlling post-operative pain (Gaynor & Muir 2002)There are three known opioid receptor classifications: mu, kappa, and delta; however, more types likely exist (Gaynor & Muir 2002; Evers & Maze 2004). Receptors are located th roughout the body and drugs acting on them produce a variety of effects on tissue and or gan systems (Pascoe 2000). Opioid drugs are classified as agonist, partial a gonist, antagonist, or agonist-anta gonist based on their affinity for specific opioid receptors (Gaynor & Muir 2002).

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40 Buprenorphine Effective pain control is important in regards to the development of an anesthetic regime. The concomitant use of medetomidine and keta mine has been reported to offer analgesic properties. In one study, cats admi nistered a combination of mede tomidine and ketamine were shown to have less post-operative pain afte r ovariohysterectomy when compared to other anesthetic regimes (Slingsby et al. 1998). However, the short duration of action associated with these drugs likely limits their use as sole an algesics (Paddleford & Harvey 1999). In addition, any potential analgesic effects of medetomidine are reversed. In the proposed combination, MKB include s a drug specifically for pain control, buprenorphine. Buprenorphine is th e most popular opioid analgesic us ed in small animal species in the UK and is widely used in other parts of Europe, Australia, and South Africa (Watson et al. 1996; Capner et al. 1999; Joubert 2001). In clinical studies, it has provide d better analgesia than other opioids and is considered highly suitabl e for perioperative pain management in cats (Dobbins et al. 2002; Ro bertson & Taylor 2004). Buprenorphine is classified as a partial mu-opioid agonist (Howland & Mycek 2000). Mureceptors are responsible for e uphoria, sedation, analgesia, and re spiratory depression (Papich 2000). Partial mu-opioid agonist im plies that buprenorphine does not produce the same effects as a full agonist, such a morphine (Pascoe 2000) However, buprenorphine has produced better analgesia in clinical studies in cats when co mpared with morphine (Stanway et al. 2002). Agonists acting on receptor si tes inhibit pain transmission or modulate pain sensation by inhibiting neurotransmitters associated w ith pain production (Papich 2000). Use of buprenorphine in cats is associated with euphori a, and often purring combined with rolling and kneading of the front paws (Robertson et al. 200 5). The euphoric effects associated with muopiate receptors help to relieve anxiety and st ress for cats in an unfamiliar environment (Papich

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41 2000). Another advantage to using buprenorphine is its long acting effects, which may exceed 6 hours in cats (Pascoe 2000; R obertson et al. 2005). The recommended dose for buprenorphine ranges from 5-20 g/kg in cats and can be ad ministered intramuscularly, intravenously, subcutaneously, transmucosally, and orally (Pascoe 2000; Robertson et al. 2005). Thermal threshold responses have been used to evaluate the efficacy of buprenorphi ne. Cats that received 10 g/kg of buprenorphine intramuscularly incr eased thermal threshold from 4 to 12 hours following administration (Robertson et al. 2003). Another study conc luded that thermal threshold only increased 45 minutes after a subcutaneous in jection of buprenorphine (20 g/kg) (Steagall et al. 2006). This suggests that the route of administration of buprenorphine may impact its effectiveness. Routes that lead to slow uptake may not achieve sufficient concentration gradients to drive the drug into the biophase (Steagall et al. 2007). No difference was seen in pain scores between control groups, who did not receive any analgesics, and cats administered 6 g/kg of buprenorphine intramuscularly after ovariohyste rectomy (Slingsby & Waterman-Pearson 1998). Buprenorphine: Side Effects In animals, well documented effects of excite ment and dysphoria exis t in conjunction with opioid use (Papich 2000). Cats ar e ordinarily the species consid ered to be more prone to excitatory effects associated with opioid ad ministration (Papich 2000). However, many of the studies concluding these reactions were used in healthy, alert animals in which doses of opioids in excess of those required for analgesia were administered. These effects seem to be less apparent when opioids are admini stered to animals in pain (Papich 2000). Buprenorphine, on the other hand, is rarely seen to cause dysphoria in cats (Robertson & Taylor 2004). The use of opioid analgesics often raises conc erns regarding clinical hyperthermia, or the elevation of body temperature above normal range. In cats, hyperthermia is considered to be 39.3C (103F) (Tilley & Smith 2004) The effects of severe hyperthermia are primarily related

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42 to an increase in metabolic activity and cellu lar oxygen consumption a nd generalized cellular necrosis associated with the denaturation of pr oteins, enzymes, and cell membranes (Niedfeldt & Robertson 2006). Doses of bupre norphine ranging between 10-20 g/kg were not found to cause hyperthermia in cats when compared with othe r opioid analgesics (Nie dfeldt & Robertson 2006; Posner 2007). An additional side effect associated with bupr enorphine use in cats is excessive mydriasis, or pupil dilation (Robertson & Tayl or 2004). Precautions need to be taken when approaching the animal as they may not see clearly. In addition, they should be kept aw ay from bright lights while their pupils are excessively dilated. Bupren orphine rarely causes dysphoria or vomiting in cats (Robertson & Taylor 2004). Buprenorphine is highly effective, eas ily administered, longacting and considered highly suitable for pain management in cats (Robertson & Taylor 2004). Opioid and Alpha2 Agonists Interestingly, a close associ ation between opioid and alpha2-adenoceptors has been identified (Unnerstall et al. 1984). Enhanced antinociception occurs following simultaneous administration of agonists at specific sites in th e spinal cord (Ossipov et al. 1989; Ossipov et al. 1990; Omote et al. 1991). Alpha2 agonists and mu-opioid agonists produce similar pharmacological effects in the CN S because their receptors are lo cated in the same area of the brain, are connected to the same signal transducer and the same effector mechanism is used by both agonists (Paddleford & Harvey 1999). Heightened effects of opioid and alpha2 agonist combinations may prove to be useful in potentiati ng their anesthetic and analgesic properties for use in feral cat sterilization surgery. Summary The overpopulation of feral cats has contributed to a variet y of problems including animal welfare concerns, detriment to wildlife, and public health considerations. These issues have

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43 sharply divided veterinarians, ec ologists and conservationists, as well as the gene ral public. In the quest for a solution, some control methods have proven to be ineffective, while others offer considerable promise. Currently, there is no obv ious answer as to wh at the most effective management strategy is. Trap-neuter-return program s offer an alternative to lethal eradication methods and are bridging the gap until other so lutions become availabl e. Due to the unique situation feral cats present, successful anesthes ia in high-volume clinics is challenging. The currently used anesthetic protoc ol, TKX, possesses limitations that have prompted the search for a superior alternative. The purpose of this study was to evaluate a combination of medetomidine, ketamine, and buprenorphine (MKB) for use in la rge-scale feral cat ster ilization clinics.

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44 CHAPTER 2 MATERIALS AND METHODS Animals Feral cats admitted to trap-neuter-return programs in Alachua County (Operation Catnip and Maddies Outdoor Cat Program) were used in this study. Ca ts were captured from their colonies using humane traps and were transporte d to the University of Floridas College of Veterinary Medicine by colony ca regivers for sterilization. Over a 2-year study period, a total of 240 cats and kittens were anesthetized using a combination of medetomidine, ketamine, and buprenorphine (MKB). Cats selected for the stu dy were of unknown health status and because of this; all researchers were required to w ear gloves and be vaccinated for rabies. Overview All anesthetic and surgical procedures we re approved by the University of Florida Institutional Animal Care and Us e Committee. Cats arrived on th e morning of surgery in wire traps or plastic crates. Upon arri val, cats were assigned an iden tification number and a medical record to document anesthetic and surgical deta ils. Cats were sterilize d, vaccinated, and had the tip of their left ear removed for identification pur poses. Cats were sent home later the same day. Caretakers were instructed to release the cats to their colonies the following day. Cat Selection Every attempt was made to choose apparently healthy cats free from obvious signs of upper respiratory infection or ot her advanced disease. Cats w ith evidence of trauma, fecal staining from diarrhea or signs of dehydration were avoided. Most ca ts were judged to be adults ( 1 year of age) (n = 238), although kittens under 6 months of age (n = 2) were included in the study.

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45 Anesthetic Drugs Medetomidine HCl (M) 1 mg/ml (Domitor, Orion Corporation, Espoo, Finland), ketamine HCl (K) 100 mg/ml (Ketaject, Phoenix Pharmaceuticals Inc, St. Joseph, MO, USA), and buprenorphine HCl (B) 0.3 mg/ml (Buprenex, Reckitt Benckiser Healthcare, Hull, England, UK) were used in this study. Atip amezole HCl (A) 5 mg/ml (Antisedan, Orion Corporation, Espoo, Finland) was used to reverse the effects of medetomidine following the completion of surgery. Experimental Design This study was divided into three separate phases. Phase 1 was a dose-finding study to determine the optimal combination of medetomidi ne, ketamine, and buprenor phine to be used in feral cat ovariohysterectomy and cas tration surgeries. The route of administration and dose of atipamezole was modified based upo n clinical observations and le ngth of recovery. Each cat was instrumented non-invasively with monitoring equipment for measurem ent of the following physiological parameters: heart rate (HR), respiratory rate (RR), blood pressure (BP), and hemoglobin oxygen saturation (SpO2). Time intervals including time to lateral recumbency, surgical duration, and time from reversal to ster nal recumbency were recorded. The preliminary trials (Phase 1) continued until a satisfactory combination of MKB was achieved. The criteria required for the selected dos e of MKB included adequate duration of action, acceptable physiological parameters, and rapi d return to normal function. Phase 2 of this study evaluated the physiologi cal parameters of the selected combination acquired in Phase 1. A total of 100 cats were to be anesthetized using the selected MKB combination. Each cat was instrumented with non-invasive monitoring equipment that allowed HR, RR, BP, and SpO2 to be recorded. Time to lateral recumbency, surgical duration, and time from reversal to sternal recu mbency were also recorded.

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46 In Phase 3 of this study, a fixed dose was cr eated using an average estimated body weight of 3 kg/cat. A mixture of MKB wa s generated using the selected dosing regime evaluated in Phase 2. From this mixture, a fixed volume was calc ulated to be used in each cat, regardless of true weight. Physiological parameters were not monitored during Phase 3; although time to lateral recumbency, surgical du ration, and time from reversal to sternal recumbency intervals were recorded. Adjustments to the calculat ed MKB fixed volume were made based upon anesthetic requirements and overa ll assessment. If anesthesia wa s found to be inadequate, the fixed volume was increased in 0.1 mL increments A fixed volume of atipamezole was calculated based on the volume of medetomidine in the fi xed anesthetic combination. Adjustments to atipamezole were made based upon the volume of MKB, clinical observations, and the total time of recovery. Pre-operative Preparation Cats were weighed in their tr aps on a pediatric scale. Ten empty traps were weighed and determined to have an average weight of 2.4 0.1 kg. The estimated trap weight of 2.4 kg was used consistently throughout this study, although actual trap weight was found to vary slightly. An approximate body weight was calculated by subt racting the average trap weight (2.4 kg) from the total weight of the cat plus the trap. This weight was used for MKB dose calculations. Induction of Anesthesia Cats were restrained at one end of the tr ap by passing a wire comb through the wire meshing of the trap. A 22-gauge, 1-inch needle wa s used to administer an intramuscular injection of MKB. The target injection s ite was into the paralumbar mu scles, although this route of administration could not be confirmed.

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47 Drug Administration Phase 1: Dose Finding Study In Phase 1, several different anesthetic comb inations were performed, varying the dose of each drug and route of administration of the reve rsal agent. Previous evaluations of MKB (Verstegen et al. 1991a) were the basis of the preliminary dosing re gimes for the initial trials in this study. Based upon duration of action and the physiological parameters, adjustments were made in order to achieve optimum results. The drug combinations performed in Phase 1 are shown in Table 2-1. Each of the three drugs (M, K, and B) were measured separately and then combined into a single syringe immediately prior to injection. Each cat was admi nistered a single intramuscular injection of MKB. If the initia l dose of MKB was found to be in sufficient, an additional dose of 10 g/kg of medetomidine was injected intramus cularly and recorded. Insufficient effect was defined as: the cat was still responsive to toe pi nch through the trap 10 minutes post-injection. If the depth of anesthesia was still found to be insufficient (at t = 15 minutes), an additional dose of 2.5 mg/kg of ketamine was injected intramuscula rly. If anesthesia remained inadequate, a face mask was placed on the cat and isoflurane va porized in oxygen was administered, via a nonrebreathing Bain anesthetic circui t, for the duration of surgery. Dependent upon the conditions of the trial, atipamezole was given intramuscularly or subcutaneously at a volume of 0.125 or 0.25 times the initial volume of medetomidine. If cats were not sternal 1 hour post-inje ction, a second dose of atipamezole was administered. This dose was of equal volume and delivered intramuscularly, regardless of the initia l route of atipamezole administration. Drug Administration Phase 2: Selected Dose Study Physiological parameters in cats given the selected drug combination from Phase 1 were evaluated in Phase 2. Each of the three drugs (M K, and B) were calculated based upon each

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48 cats estimated weight (cat plus trap weight average trap we ight) and combined in a single syringe prior to injection. The selected dosing regime is shown in Table 2-2. If the initial dose of MKB was found to be insufficient (at t =10 minutes), an additional dose of 20 g/kg of medetomidine was injected intramuscularly. If anesthesia remained inadequate (at t =15 minutes) an additional dose of 2.5 mg/kg of ke tamine was injected intramuscularly. If anesthesia continued to be in sufficient, a face mask was placed on the cat and isoflurane gas vaporized in oxygen was administ ered via a non-rebreathing Bain anesthetic circuit, for the duration of surgery. At th e completion of surgery, each cat received a subcutaneous (intrascapular) dose of atipamezo le to reverse the eff ects of medetomidine. Drug Administration Phas e 3: Fixed Dose Study In Phase 3, the selected dosing regime ( 100 g/kg M, 10 mg/kg K, 10 g/kg B) was calculated for a 3 kg cat (Table 2-4). A mixture of MKB was calculated to accommodate 20 cats (Table 2-5). In a sterile 30 mL vial, 6.0 mL medetomidine, 6.0 mL ketamine, and 2.0 mL of buprenorphine were mixed together. From this vial, an injection volume of 0.7 mL was withdrawn (Table 2-4). If anesthesia was found to be inadequate, the fixed volume was increased by 0.1 mL (0.8 mL). The fixed volum e was administered to all cats regardless of true weight. The MKB injection was administered intramuscu larly. The target site was the paralumbar muscles, although this could not be confirmed. Subcutaneous atipamezole was administered po st-operatively to reverse the effects of medetomidine. The injection volume of atipam ezole was 0.08 mL (0.4 mg ) as calculated by the initital volume of medetomidine (T able 2-6). If cats did not ac hieve sternal recumbency by 1hour following the injection of atipamezole, an additional 0.4 mg (0.08 mL) of atipamezole was given into the paralumbar muscle intramuscularly.

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49 Cats that received the 0.8 mL (0.344 mg M, 34.4 mg K, 0.034 mg B) dose of MKB participated in the high-volume clinic (Operati on Catnip) without time interval, physiological measurement, or monitoring. Additionally, weig hts were not recorded. This was the first simulation of what would normally take place in a high volume clinic using the MKB protocol in mass. Due to the volume of cats anesthetized s imultaneously, every effort was made to note the need for supplemental anesthesia, although actual numbers may be higher. Clinical Procedures: Evaluati on of Anesthetic Effects Following injection, loss of reaction to toe pinch was tested from outside the trap. Once determined to be unresponsive, each cat was ca refully removed from its trap and its sex was determined. Palprebral reflex, jaw tone, and overall muscle relaxation were evaluated and recorded. These criteria were used to determine ad equacy of anesthesia be fore, during, and after surgical procedures. Clinical Procedures: Hemoglobin Oxygen Saturation A pulse oximeter sensor (Nellcor Puritan Bennett NPB-40, Nellcor Puritan Bennett Inc, Pleasanton, CA, USA) was placed on the cats tongue for the purpose of monitoring oxygen hemoglobin saturation (SpO2) levels and pulse rate. If readin gs could not be obtained from the tongue, digits or an ear were used in an attempt to obtain additional readings. Clinical Procedures: Evaluation of Cardiovascular Function Blood pressure was measured using a Doppler probe (Ultrasonic Doppler Flow Detector, Model 811-B and 811-L, Parks Medical Electronics Inc, Aloha, OR, USA). The hair over the caudal carpus was shaved. Ultrasound gel was app lied to the doppler probe, placed directly over the digital arteries, and secured with zinc oxide tape. A sma ll (size 3) blood pressure cuff (Critikon Inc, Southington, CT, USA) was applied proximally and attached to a sphygmomanometer (Welch Allyn, Beaverton, OR, USA) from whic h systolic blood pressure

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50 values were obtained. The size of each cuff wa s determined by cuff width encompassing 48-50% of the circumference of the forelimb where it was applied. Heart rate and systolic blood pressure were measured and recorded at 5 minute intervals throughout the duration of anesthesia. Pulse oximetr y readings were only accepted if consistent with the pulse rate counted from the Doppler probe and the heart rate obtained by palpation. Clinical Procedures: Evaluati on of Respiratory Function Respiratory rate was determined visually (c ounted for 30 seconds). Clear surgical drapes facilitated observation of chest movements during ovariohysterectomy surgeries. If clear surgical drapes were not used, respirat ory rate was determined by palpation. Respiratory rate was conducted at 5 minute intervals thro ughout the duration of anesthesia. Clinical Procedures: Temperature Rectal temperature was measured using a sta ndard electronic digita l thermometer (MABIS Healthcare, Inc., Waukegan, IL, USA). Temperatur e was determined at the time of induction, at the completion of surgery, and 5 minutes following the reversal of medetomidine. Clinical Procedures: Pre-surgical A sterile petroleum-based ophthalmic lubrican t (Akorn, Inc., Buffalo Grove, IL, USA) was applied to both eyes and each cat was administer ed a long-acting penicillin injection (Extended Action Penicillin G Benzathine and Penici llin G Procaine, G.C. Hanford Manufacturing Company, Syracuse, NY, USA) s ubcutaneously. Prior to surger y, approximately 1 cm of the distal tip of the left ear was removed using a ster ile hemostat and surgical scissors. This step was used as the first indicator of anesthesia efficacy in our study. Finally, the hair was clipped from the surgery site and the skin was prepared using alternating providine iodi ne and alcohol scrubs.

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51 Clinical Procedures: Post-operative After surgery was complete, each cat was vacci nated against rabies, feline leukemia virus, feline panleukopenia virus, herpes virus, and calicivirus (FVRCP) (Rabvac 3TF Fort Dodge Laboratories, Fort Dodge, IO, USA; Fel-O-Guard Plus 3 + Lv -K, Fort Dodge Laboratories, Fort Dodge, IO, USA). The rabies vaccine was admi nistered subcutaneously in the right hind leg. The feline leukemia/FVRCP combination vaccine wa s administered subcutaneously in the left hind leg. In addition, each cat received a si ngle dose of selamectin (Revolution) (Pfizer Animal Health, Exton, PA, USA) administered topically for parasite control. Quality of Recovery Following the completion of surgery and the subsequent reversal of medetomidine, a Quality of Recovery Score (QRS) was assigne d and recorded according to predetermined guidelines (Table 2-3). Data Least square mean (LSM) and true mean for physiological data were reported. The least LSM is identical to the true mean assuming no mi ssing data and the number of replications is the same in each group. Because our data did not m eet these criteria, both were reported for comparison. Statistical Analysis SAS PROC MIXED (SAS Institute Inc ., Cary, NC, 27513-2414, USA) was used to evaluate physiological paramete rs in support of missing data. SAS PROC MIXED assumes data are missing at random, which is suspected for th e majority of absent records in this study, although cannot be confirmed. Missing data was the result of equipment error, human error, or the result of other unforeseen complications.

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52 Individual anesthetic records were kept for each cat. Male and female data were compared. Physiological variables (BP, RR, SPO2, HR, and rectal temperature), the time from MKB injection until lateral recumbency, the time fr om MKB injection until the start of surgery, surgical duration, the time from atipamezole admi nistration to sternal recumbency, and the total time recumbent were compared between male s and females. Body weight, the need for additional MKB, and the need for additional atip amezole were also compared between males and females. In cats requiring additi onal MKB, time from reversal to sternal recumbency, total time recumbent, and additional atipamezole requir ements were compared and analyzed amongst males and females, as well. Weight, MKB injection to time of lateral recu mbency, MKB injection to start of surgery, surgical duration, time of reversal to sterna l recumbency, and total time recumbent were compared by means of an unpaired t-test. Physiological variables (BP, RR, HR, SPO2) were compared separately over time by means of a two-factor ANOVA (Time-fixed; Subject-random) test. Temperatures were compared over time using split-plot repeated measures ANOVA with post hoc time comparisons by means of Bonferronis t-test. The effect of multiple doses of MKB on the total time recumbent was evaluated us ing a two-way ANOVA test (SAS PROC MIXED, SAS Institute Inc., Cary, NC, 27513-2414, USA). Re versal to sternal time was compared between cats that did or did not require a dditional MKB by means of an unpaired t-test. The significance in the difference between physiological parameters upon the completion of surgery and 5 minutes following atipamezole administration were compared in all cats. Changes in physiological variables (BP, RR, HR, SPO2) before and after the reversal of medetomidine were analyzed using split-plot repeated measures ANOVA. The -priori significance level used thr oughout this study was P < 0.05.

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53 Finally, the associations between sex and a dditional MKB, and sex and the need for additional reversal were evalua ted using a 2 x 2 contingency ta ble and a chi-square test. Similarly, the need for additional MKB and the need for additional reversal were evaluated using a 2 x 2 contingency table and a chi-square test for males and females separately. If expected values were < 5, then a minimum chi-square test was used instead of chi-square.

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54 Table 2-1. Dose-finding study n = M K B A A g/kg mg/kg g/kg (x M volume) Route of Administration Trial 1 10 80 7.5 10 0.25 IM Trial 2 10 80 10 10 0.25 IM Trial 3 15 100 7.5 10 0.25 IM Trial 4 3 100 10 10 0.25 IM Trial 5 4 110 7.5 10 0.125 IM Trial 6 8 110 7.5 10 0.25 IM Trial 7 9 110 7.5 10 0.25 SC Trial 8 10 100 10 10 0.25 SC Table 2-2. Selected dosing regime Drug Dose Route of Administration Medetomidine (M) 100 g/kg IM Ketamine (K) 10 mg/kg IM Buprenorphine (B) 10 g/kg IM Atipamezole (A) 0.25 x M volume SC Table 2-3. Quality of recovery scores QRS Scoring Guidelines 3 Good: Smooth Recovery, No Excitement, < 45 min Reversal to Sternal Time 2 Acceptable: Mild Excitement and/or <1hr Reversal to Sternal Time 1 Unacceptable: Severe Excitement, 2nd Reversal and/or >1hr Reversal to Sternal Time Table 2-4. Fixed dose calculation Drug Dose Concentration mL/kg mL/3kg Medetomidine (M) 100 ug/kg 1 mg/ml 0.1 0.3 Ketamine (K) 10 mg/kg 100 mg/ml 0.1 0.3 Buprenorphine (B) 10 ug/kg 0.3 mg/ml 0.033 0.1 Table 2-5. MKB mixture calculation (20 Cats) mL/3 kg x # of Cats Total (mL) Medetomidine (M) 0.3 20 6 Ketamine (K) 0.3 20 6 Buprenorphine (B) 0.1 20 2

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55 Table 2-6. Atipamezole fixed dose calculation Volume of (M) x 0.25 0.3 mL x 0.25 = 0.075 mL

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56 CHAPTER 3 RESULTS Phase 1-Dose-Finding Study During Phase 1 of this study, 69 cats (41 males, 28 females) were an esthetized with MKB in 8 separate trial experiments (Table 3-1). A ll cats were of accept able body condition and appeared healthy at the time of the procedure. Pr egnancy (n = 3) and bila teral cryptorchidism (n =1) were observed in a small number of cats. In addition, one male was found to be previously castrated. Drug combinations in groups 1, 2, and 3 pr ovided good anesthesia, however, duration of action was inadequate for surgery completion. Dura tion of action in groups 1, 2, and 3 were 35 16 minutes (M: 36 minutes; R: 14-62 minutes ) (Median, Range), 41 14 minutes (M: 45 minutes, R: 19-67 minutes), and 38 25 minut es (M: 30 minutes; R: 15-105 minutes), respectively. In group 4 durati on of action was sufficient (62 26 minutes) (M: 75 minutes; R: 32-79 minutes) and physiological parameters were acceptable, but recoveries were violent and considered unacceptable in every cat (n = 3). In groups 5, 6, and 7 depth of anesthesia was good, but the duration of action was inconsistent and was not considered accep table. The duration of action in groups 5, 6, and 7 were 50 28 minut es (M: 46 minutes; R: 26-84 minutes), 30 6 minutes (M: 30 minutes; R: 21-40 minutes), 35 6 minutes (M: 35 minutes, R: 26-47 minutes), respectively. The dose of atipamezole and route of admi nistration in groups 1, 2, 3, and 4 provided acceptable recovery times ( 1 hour). In group 5, the reversal dose was decreased by one-half to see if a smaller dose would be sufficient. This pr otocol was found to result in delayed recoveries ( 1 hour) and all cats (n = 4) re quired an additional injection of atipamez ole. The reversal volume and route of administra tion in groups 6 and 7 were sa tisfactory, with group 7 providing

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57 an alternate option for atipamezole administration (subcutaneous injection) Cats that received subcutaneous atipamezole in group 7 were obs erved to have longer (28 15 minutes; M: 31 minutes, R: 5-50 minutes), yet acceptable, recove ries compared to group 4 (17 13 minutes; M: 14, R: 5-36 minutes). Recoveries in group 7 had no incidence of excitement or violent behavior. Group 4 was considered the best with respect to adequate depth of anesthesia and duration of action, however, recoveries were unacceptable. The recovery process appeared to take place undesirably fast, and was accompanied by exciteme nt and violent behavior. Based on these observations, group 8 combined the MKB doses from group 4 (100 g/kg M, 10 mg/kg K, 10 g/kg B) with the reversal dos e and route of administration fr om group 7 (1.25 mg (0.25 mL) x M; subcutaneously). This protocol was carried out in 10 cats and exhibi ted superior qualities when compared to previous trials. Duration of action was sufficient (33 11 minutes; M: 30, R: 15-57) and time to sternal recumbency (34 24 minutes; M: 25; R: 5-74 minutes) was adequate, uneventful, and within acceptabl e recovery parameters. The protocol executed in group 8 was considered to have the best potential for our needs, and therefore, was chosen for further investigation. Phase 1-Dose-Finding Study: Side Effects In Phase 1, 4 cats displayed severe respirator y depression. All 4 cats received the same dose of MKB (110 g/kg M, 7.5 mg/kg K, 10 g/kg B). Phase 2-Selected Dose Study: Animals One hundred and one cats (53 males, 48 female s) were anesthetized with the selected dose of MKB (100 g/kg M, 10 mg/kg K, 10 g/kg B) Ninety-nine cats were identified as adults and 2 cats were approximately 6 weeks of age. Tw o cats were pregnant and 2 cats were lactating at the time of surgery. Three cats were found to be previously st erilized (1 male, 2 females), therefore, a total of 98 cats (52 males, 46 female s) were sterilized usi ng the selected dose of

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58 MKB. With one exception, all cats were considered to be free from obvious signs of disease or trauma. One cat displayed signs of marked de hydration, diarrhea, and intestinal parasites upon examination following MKB administration. There wa s evidence of external parasites, such as fleas, on most cats. There was no significant difference in the we ight of male cats (3.2 0.2 kg) compared with female cats (2.9 0.1) (P = 0.15). Cat weights ranged between 0.93 kg and 6.31 kg and therefore, the volume of the MKB combination was between 0.22 mL and 1.4 mL, respectively. Phase 2-Selected Dose Study: Time Intervals Lateral recumbency was achie ved in 4.3 4 minutes and 5.2 5.6 minutes (mean SD) after the injection of MKB in male and fema le cats, respectively. There was no significant difference in lateral recumbency times between males and females (P = 0.35). Eight cats (2 males, 6 females) vomited following anesthetic injection, however, th e transition to lateral recumbency was free from signs of CNS exciteme nt. The time from MKB injection until the start of surgery was significantly l onger in females (23 6.2 minutes) than in males (16.1 5.2 minutes) (P < 0.0001) due to longer surgical prep aration requirements. Similarly, the surgical duration was significantly longer in female cats (29.6 18.7 minutes) compared to male cats (3.2 2.5 minutes) (P < 0.0001). The time from the injection of the reversal agent atipamezole until the onset of sternal recumbency was not significantly (P = 0.9) different between males (38.6 38 minutes) and females (40.6 78.2 minutes). There was also no difference (P = 0.6) in time to sternal recumbency in cats that received a second dose of MKB (n =11). The total time recumbent (including prepara tion, surgery, and recovery) was significantly longer in females (86.9 27.1 minutes) than in males (64.7 36.2 minutes) (P = 0.0009). The total time recumbent was significantly different (P = 0.008) in males (62 20.7 minutes) and

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59 females (103.8 28.4 minutes) who required a se cond dose of MKB (7 males, 4 females), however, there was no interaction observed between the two (total time recumbent and the need for additional MKB) (P = 0.34). There was no difference (P = 0.4) in the fr equency of additional MKB requirements in male (n = 7) and female (n = 4) cats. Similarl y, there was no difference (P = 0.4) in the frequency of cats (6 males, 8 females) requiring a second dose of the reversal agent, atipamezole. There was also no association (P = 0.3) between cats that required a second dose of MKB and cats that required a second dose of reversal agent. Phase 2-Selected Dose Study: Physiological Variables Physiological variables (BP, HR, SpO2, and RR) were measured immediately after removal from the trap, throughout the surgical pro cedure, and 5 minutes fo llowing the reversal of medetomidine. The feral nature of the cats prohibited further mon itoring beyond this point. Physiological data are missing intermittingly as a result of equipment error, human error, or other unforeseen complications. Absent data are beli eved to be missing at random, although this cannot be confirmed. Male and female data were assessed separate ly over time. The average range of data collections were between 5 and 35 minutes in ma les and between 5 and 85 minutes in females. Data were collected every 5 minutes using set ti me intervals. The start point and the length of these intervals were determined by the time of lateral recumbency and the surgical duration. Following the reversal of medetomidine, physio logical parameters were collected for an additional 5 minutes in all cats when possible. So me measurements were unable to be obtained in cats with unusually short recovery times. In males, a relationship between blood pr essure (R: 91-195 mm Hg) and time could not be made (P = 0.52) with > 95% confidence. Blood pressure (R: 38-190 mm Hg) decreased

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60 significantly over time (P < 0.0001) in female cat s. One female cat was hypotensive (< 60 mm Hg) at least once throughout the du ration of anesthesia. Twenty-two cats (7 females, 15 males) were hypertensive (> 160 mm Hg) at leas t once throughout the duration of anesthesia. Normotension was observed following the administ ration of medetomidine and throughout the duration of surgery in most ca ts (Figure 3-1 and Figure 3-2). In males, heart rate (R: 77-176 beats/minute) did not significantly (P = 0.32) change over time (Figure 3-3). No observation of tachycardi a (> 180 beats/minute) wa s observed in any cat. Conversely, heart rate (R: 57-172 bpm) significantly decreased (P < 0.0001) as a factor of time in female cats (Figure 3-4). One female was obser ved to be bradycardic (< 60 beats/minute) throughout the duration of anesthesia. Severe hemoglobin desaturation was observe d in both males (R: 36-99 %) and females (R: 73-100 %) 5 minutes following the administrati on of MKB. Hemoglobin saturation was 81.1 1.9% and 86.3 1.1 % 5 minutes following MKB administration in males and females, respectively. Hemoglobin oxygen saturation, however significantly increa sed over time in both males (P = 0.0003) and females (P < 0.0001) (Figur e 3-5 and Figure 3-6). There was no change in respiratory rate over time in males (R: 4-76 breaths/minute) (P = 0.13) or females (R: 4-56 breaths/minute) (P = 0.14) (Figure 3-7 and Figur e 3-8). Apneustic breathing was observed in 3 cats and periods of apnea (longer than 1 minute) were observed in 1 cat. Oral mucus membrane color was also evalua ted. Most cats contai ned pink membranes and were considered clinically acceptable. In ad dition, capillary refill time was evaluated in most cats and noted to be less than 2 seconds. Rectal body temperature was measured at thr ee separate times throughout the procedure: following MKB induction (start), at the completi on of surgery (pre-reversal), and 5 minutes

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61 following the reversal of medetomidine (post-re versal) (Figure 3-9). Rectal temperature was lower in females (P < 0.0001) at all three points in time and temper ature decreased over time in both males and females (P < 0.0001). Start, pre-reve rsal, and post-reversal temperatures in males were 38.9 0.6C, 38.2 0.7C, 37.9 0.7C, respectively. Start, pr e-reversal, and post-reversal temperatures in females were 38.7 0.5C, 36.8 1.1C, 36.7 1.2C, respectively. No male temperatures were below 34C (93.2F). One female had a te mperature of 33.1C (91.4F) and was considered hypothermic. Phase 2-Selected Dose Study: Physiologi cal Variables before and after Reversal Physiological parameters obtained following th e completion of surgery (pre-reversal) and 5 minutes following the reversal of medetomidine (post-reversal) were compared. Male (P < 0.0001) and female (P < 0.0001) blood pressures changed significantly over the 5 minute reversal period, but did not change differently over the 5 minute reversal period (P = 0.37). Blood pressures in females (P < 0.0001) were le ss than blood pressures in males (P < 0.0001) both prior to the reversal of medetomidine and following the reversal of medetomidine (Figure 310). Blood pressure was significan tly lower post-reversal (P = 0.0003) when compared to prereversal values (P < 0.0001) in both males and females. Heart rate increased followi ng the reversal of medetomidine in males (P < 0.0001) and females (P < 0.0001) when compared to immediat e pre-reversal values (Figure 3-11). Prereversal heart rates in males were greater th an in females (P = 0.0006), however, there was no difference between male and female heart rates following the reversal of medetomidine (P = 0.25). Following the reversal of medetomidine hemoglobin oxygen saturation significantly increased in males (P = 0.0001) and females (P = 0.03). Oxygen saturation value pre-reversal (P < 0.0001) and post-reversal (P = 0.002) were sign ificantly lower in males when compared to

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62 females at both time points (Figure 3-12). There we re no differences in respiratory rates in males or females over time (P = 0.7). Temperatures immediately following treatm ent with MKB were 38.9 0.6C (102F 1.1) in males and 38.7 0.5C (101. 7 0.9F) in females. Followi ng the completion of surgery, temperatures dropped to 38.1 0.7C (100.8 1.3 F) and 36.7 1.1C (98.4 1.9F) in males and females, respectively. Temperature was si gnificantly lower (P < 0.0001) in males (37.9 0.7C) (100.2 1.2F), but not in females (36.6 1.2 C) (98.2F) (P = 0.16) following reversal. Females, however, had lower temperature valu es at both pre-revers al and post-reversal recordings (P < 0.0001) compared to males (Figure 3-13). Phase 2-Selected Dose Study: Rescue Anesthesia (Isoflurane) A total of 11 cats (2 males, 9 females) requi red supplemental anesthesia which constitutes approximately 11% of the study population. Fe males required supplemental anesthesia significantly more often (P = 0.02) than males. Rescue anesthesia in the 2 males was required at the time of induction, following a second dose of MKB that proved to be insufficient. Of the 9 females that required supplemental anesthesia (iso flurane) 5 of them requ ired it after 45 minutes of successful anesthesia (timed from the initial injection). Phase 2-Selected Dose Study: Quality of Recovery Scores Quality of Recovery Scores (QRS) (Table 3-2) were assigned following the completion of surgery and subsequent revers al of medetomidine. Recovery tim es in males and females were 38.6 38 minutes (M: 30 minutes; R: 5-207 minu tes) and 40.6 78.2 minutes (M: 22 minutes, R: 4-130 minutes) in males and females, respective ly. Ninety-eight cats (51 males, 47 females) were scored for quality of recovery (QRS). Fifty-nine cats (28 males, 31 females) received a QRS of 3 (good) and 15 cats (12 males, 3 female s) received a QRS of 2 (acceptable). The remaining 24 cats received a QRS of 1 (unacceptable), mainly due to prolonged recovery times

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63 (n = 20). Only 4 cats (2 males, 2 females) were considered to have an unacceptable QRS as a result of overly excited or violent behavior. A pproximately 75% of cats achieved an acceptable or good QRS. Phase 2-Selected Dose Study: Side Effects Under MKB anesthesia, apneustic breathing (holding of breath upon inspiration) was observed in male (n = 3), but not female cats. Additionally, rapid shallow breaths were observed in 6 anesthetized male cats. Eight males responde d to the stimulus of cas tration surgery (tension on the spermatic cord) by hind limb movements, while spontaneous movement was observed in 3 females. Spontaneous movements were defined as movement that did not occur in response to a noxious stimulus; when it was noted, cats were checked by squeezing their toe and no response was elicited. Spontaneous movement included paw extension and ear flicking. Post-induction apnea (n = 1), post-operative retc hing (n = 1), and pawing at th e mouth post-reversal (n = 6) were also observed. Phase 3-Fixed Dose Study (0.7 mL): Animals Based on an average calculated weight of 3 kg/cat and the selected dosing regime achieved in Phase 1 and tested in Phase 2, a fi xed-dose of MKB was extr apolated and performed in Phase 3. Two fixed volumes of MKB were evaluated in this study. Thirty-six cats (16 males, 20 females) were anesthetized using an MKB fi xed dose volume of 0.7 mL (0.3 mg M, 30 mg K, 0.03 mg B). Seven cats were pregnant and one female was previously spayed. The average weight for both male and fe male cats was 2.8 0.6 kg. Based on the fixed dose, the average cat received an overdose of MKB (107 g/kg M, 10.7 mg/ kg K, 10.7 g/kg B). This represented a 7% increase in the total amount of medetomidine, ketamine, and buprenorphine given in excess. The average we ight for cats < 3 kg (n = 25) was 2.4 0.3 kg.

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64 Based on the fixed dose volume, cats weighing le ss than 3 kg were overdosed (125g/kg M, 12.5 mg/kg K, 12.5 g/kg B) on average by 25% for MKB. The smallest cat weighed 1.8 kg. Based on the fixed dose, this cat was overdosed (166 g/kg M, 16.6 mg/kg K, 16.6 g/kg B) as well. This represents a 66% increase in the amount of MKB given in excess. Approximately 30% of cats (n = 11) weighed over 3.0 kg. The average we ight for cats weighing > 3 kg was 3.56 0.4 kg. Cats weighing over 3 kg were under dosed (8 4 g/kg M, 8.42 mg/kg K, 8.42 g/kg B) by 16% Seven cats (2 males, 5 females) needed an additional injection (0.1 mL; 0.043 mg M, 4.3 mg K, 0.0042 mg B) of MKB. Four of the 7 cats that required an additi onal injection of MKB weighed 3.0 kg. Similarly, 7 cats (2 males, 5 female s) required an additi onal injection of the reversal agent atipamezole, including 3 cats (1 ma le, 2 females) that received a second dose of MKB. One female cat required a third injection of atipamezole approximately 2 hours following the initial atipamezole injecti on. That cat achieved sternal recu mbency approximately 10 minutes following the third injection of atipamezole. Phase 3-Fixed Dose Study (0.7 mL): Time Intervals Time to lateral recumbency was 7 5 minutes and 4 3 minutes in males and females, respectively. Surgical duration was longer in fe males (43 18 minutes) than in males (7 4 minutes). Time from reversal to sternal recu mbency was 31 20 minutes in males and 31 31 minutes in females. Total time recumbent was 64 20 minutes and 117 46 minutes in males and females, respectively. Phase 3-Fixed Dose Study (0.7 mL): Side Effects Apnea or severe respiratory depression was obs erved in several cats (n = 6). The weight of these cats (4 females, 2 males) was 2.9 0.5 kg (M: 2.9 kg, R: 2.34-3.9 kg). One cat vomited following injection of MKB.

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65 Phase 3-Fixed Dose Study (0.7 mL): Rescue Anesthesia Thirteen cats (2 males, 11 females) required supplemental anesthesia. Of the 13 cats, 7 weighed more than 3.0 kg. Cats were further di vided into those requiri ng inhaled supplemental anesthesia before (n = 7) 45 minutes of successf ul anesthesia and after (n = 6) 45 minutes of successful anesthesia. Approximately 36% of the total population rece iving the fixed dose required supplemental anesthesia. In conclusion, th is number was far greater than our initial goal of less than 10% of the population requiring rescue anesthesia, and therefore the volume of MKB was increased. Phase 3-Fixed Dose Study (0.8 mL): Thirty-four cats (9 males, 25 females) were anesthetized using a fixed MKB volume of 0.8 mL (0.344 mg M, 34.4 mg K, 0. 034 mg B). Physiological para meters were not monitored and time intervals were not recorded. Excessive requirements for MKB (n =3) or the need for supplemental isoflurane anesthesia (n = 9) were observed. Because cats were monitored as a whole, and not individually, this number may be higher as a result of mi ssed data. Three cats vomited following the initial injection of MKB. The initial injection of MKB was performed by an anesthetist unfamiliar with MKB and its volume in 28 cats. In 4 of the cats (14%), the anesthetist reported difficulty injecting a larger drug volume compared to the usual TKX protocol (0.25 mL). Two of the 4 cats with difficult injections required supplemental anesthesia. Apnea or severe respiratory depression was obs erved in most cats and was more recurrent in cats anesthetized with MKB (fixed volume) in Phase 3, compared to those anesthetized in Phase 2 (weight-specific). Because individual me dical records were not kept for each cat, an

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66 exact number is not available, although it is believed that more than half of the cats anesthetized with the 0.8 mL fixed volume of MKB displaye d clinical signs of re spiratory distress. Summary Based on preliminary findings in Phase 1, a sele cted dosing regime was chosen to be used in 100 feral cats. In Phase 2, cats anesthetized with the selected protocol were closely monitored, recording physiological paramete rs and time intervals of inte rest throughout the surgical procedure. The selected dose in Phase 2 provi ded an anesthetic combination that offered acceptable physiological parameters and the poten tial for a fixed-volume derivative. In Phase 3, a calculated a fixed volume of MKB (0.7 mL) base d upon an average calculated value for a feral cats weight (3.0 kg) was found to provide inadequate anesthes ia. Based on these observations, the decision was made to increase (0.8 mL) th e fixed volume of MKB. The 0.8 mL of MKB was considered undesirable as a high percentage ( 30%) of cats required rescue anesthesia. In addition, apnea or respiratory depression was obs erved in most cats. There was no perioperative mortality for cats anesthetized with MKB. In conclusion, the selected dose of MKB used is Phase 2 offered potential when used in a weight-specific manner, although failed to meet the goals set out at the st art of the study when extrapolated to a fixed dose to be used in al l cats, regardless of true weight. In addition, the adverse physiological effects observed with the fixed-dose results were less than desirable, making the studied fixed dose of MKB an unsuita ble combination for use in feral cats of unknown weight.

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67 Table 3-1. Dose-finding study groups n = M K B A A g/kg mg/kg g/kg (x M volume) Route of Administration Group 1 10 80 7.5 10 0.25 IM Group 2 10 80 10 10 0.25 IM Group 3 15 100 7.5 10 0.25 IM Group 4 3 100 10 10 0.25 IM Group 5 4 110 7.5 10 0.125 IM Group 6 8 110 7.5 10 0.25 IM Group 7 9 110 7.5 10 0.25 SC Group 8 10 100 10 10 0.25 SC Table 3-2. Quality of recovery scores QRS Scoring Guidelines 3 Good: Smooth Recovery, No Excitement, < 45 minutes Reversal to Sternal Time 2 Acceptable: Mild Excitement and/or <1hr Reversal to Sternal Time 1 Unacceptable: Severe Excitement, 2nd Reversal and/or >1hr Reversal to Sternal Time

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68 Figure 3-1. Blood pressure in male cats over time Figure 3-2. Blood pressure in female cats over time

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69 Figure 3-3. Heart rate in male cats over time Figure 3-4. Heart rate in female cats over time

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70 Figure 3-5. Sp O2 (%) in male cats over time Figure 3-6. Sp O2 (%) in female cats over time

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71 Figure 3-7. Respiratory ra te in male cats over time Figure 3-8. Respiratory rate in female cats over time

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72 Figure 3-9. Temperature over time Figure 3-10. Blood pressure before and after reversal

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73 Figure 3-11. Heart rate be fore and after reversal Figure 3-12. SpO2 (%) Before and after reversal

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74 Figure 3-13. Temperature before and after reversal

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75 CHAPTER 4 DISCUSSION Feral cat sterilization clinics are an integral component of Trap-Neu ter-Return programs. Such programs present a variety of challenges and rely heavily on the efficacy, predictability, and safety of an anesthetic regime. Not only must anesthesia protocols be adequate to perform all surgeries, they must also safely and effectively render cats unconscious while still in their traps. An anesthetic protocol for use in large feral ca t clinics must be inject able, provide adequate duration of action, support acceptable physiological parameters, have a wide margin of safety, and allow rapid return to normal function. In addition, postoperative analgesia must be adequate. TKX, the current anesthetic regime used in Operation Catnip accommodates many of the demands associated with feral cat anesthesia, howe ver, it also posses inadequacies. An attempt to improve the TKX protocol through the study of MKB was the purpose of this study. While MKB may compensate for some of the limitations associ ated with TKX, the doses of MKB used in this study exhibited its own shortcomings. The preliminary trials of this study led to a MKB combination of considerable promise. In Phase 1 of this study, superior components from tw o trial groups (4 and 7) were combined. It was hypothesized that if the durati on of action achieved in group 4 could be maintained while the recoveries could be slowed down and still prov ide acceptable recovery tim es, the overall product would provide adequate anesthesia and smoother recoveries, as seen in group 7. The anesthetic and physiological effects of the selected dose were considered acceptable and even resolved some of the limitations associated with TKX. However, when tested in a high-volume setting, the MKB fixed volume offered less than desirable an esthetic effects; these including the frequent need for additional MKB injections, rescue anesthes ia with isoflurane gas, and repeated reversal injections. In addition, apnea and respiratory depression were more pronounced and occurred

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76 with a higher incidence in cats that received the fixed volume dos e of MKB compared to those dosed in a weight specific manor in Phase 2. One study reported anesthetic-related deaths to be 0.24% (0.21-0.27 %) in cats (n = 79, 178) sedated or anesthetized for a variety of su rgical procedures usi ng a wide range of drug combinations (Brodbelt 2006). None of the cats (n =240) in this study died prior to being released back to their colonies. The absence of pe rioperative mortality is thought to contribute to a wide margin of safety associated with the us e of MKB. The MKB protocol used in this study was considered relatively easy to administer although the large injection volume may have compromised the ability to accura tely deliver full doses in so me cats. Approximately 11 % of cats in Phase 2 and 13% of cats in Phase 3 required a supplementa l injection of MKB. This may have been the result of a larg e injection volume preventing a comp lete and accurate injection or perhaps, more simply, the administration of a dos e insufficient at providing adequate anesthesia. Both of these factors may have contributed to th e need for supplemental anesthesia. Female cats had a greater need for rescue anesthesia compared to males. This is likely the result of lengthier preparation and surgical procedur es when compared to males. Hemoglobin desaturation, particularly in the first five minutes following MKB administration, was common in both male and fema le cats; however, it was more apparent in male cats. One male cat was observed to report an oxygen saturation value of 36 % following MKB administration. Respiratory depression and periods of apn ea (temporary suspension in breathing for more than 1 minute) were consistent with previous studies of similar medetomidine and ketamine combinations (80g/kg M; 10 mg/ kg K), in which apnea was observed in 8 out of 10 cats (Verstegen et al. 1989; Verstegen et al. 1991a).

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77 Low SpO2 values may be caused by anything that decreases the delivery of oxygen to the tissues including hypoxemia, vasoconstriction, or low cardiac output (Thurmon et al. 1996). Cardiac output (CO) is defined as the quant ity of blood pumped by the heart each minute and varies dependent upon heart rate (HR) and st roke volume (SV) (Berne et al. 2004). The relationship between cardiac out put and heart rate is linear (CO = HR x SV). Low SpO2 values may be the result of patient factors or detec tion limitations. Because pulse oximetry relies on peripheral blood flow, the accuracy of readi ngs may be affected as a result of the vasoconstriction or decreased he art rate observed following the ad ministration of medetomidine (Haskins 1996). The observed hemoglobin desa turation, especially as seen following the injection of MKB, may have b een the result of equipment inaccuracies or simply, the known depressant cardiovascular effect s of medetomidine. Cats were not intubated in this study and spontaneously breathed room air. This was lik ely a contributing factor to low oxygen saturation levels seen in cats anesthetiz ed with both TKX and MKB. A st udy assessing a combination of MKB with a significantly lower dose of medetomidine (40 g /kg) observed an overall SpO2 value of 94 4% (Cistola et al 2002). A higher do se of medetomidine, such as the amount used in this study, may have affected SpO2 values as a result of in creased vasoconstriction. An increase in vasoconstriction may have contributed to either (1) a decrease in oxygen delivery to tissues or (2) a decrease in the accu racy of pulse oximetry readings. SpO2 values were observed to increase over time in MKB treated cats. It is hypothesized that the increase in SpO2 values over time was a result of the metabolism of medetomidine, lowering plasma concentration values, and exhibiting less total e ffect (vasoconstriction). A stea dy decrease in vasoconstriction may have contributed to increased ox ygen delivery, resul ting in higher SpO2 values over time. Alternatively, decreased vasoconstriction may have provided more accurate pulse oximetry

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78 readings in which earlier readi ngs, when medetomidine plasma concentrations were higher, would be considered less precise. The tr ue cause for the observed increase in SpO2 values is unknown. Once the amount of deoxygenated hem oglobin exceeds 5 g/100 mL, the blood changes from a red color to a blue color (cya nosis) (Thurmon et al. 1996). Despite low pulse oximetry readings, oral mucous membrane color remained pink and was clinically acceptable in most cats. Pale mucous membranes were noted a nd hypothesized to be the result of drug-induced vasoconstriction following the administration of medetomidine. While low oxygen saturation is preventable and easily treated by providing supplemental oxygen, it is not feasible to administer to all cats due to the number of cats needi ng simultaneous administration and equipment limitations. Additionally, the cha llenge of identifying cats at ri sk of hypoxia and supplementing them as needed, should not be underestimated wh en many cats are anesth etized simultaneously. Hypoxia may result in abnormal organ function and/or cellular damage (Thurmon et al. 1996). The exact repercussions of low SpO2 levels in cats anesthetized with MKB are unknown and may result in injury not apparent in the immediate post-operative period. Normal heart rates in cats ra nge between 145 and 200 beats pe r minute (Muir et al 2000). Following the administration of MKB, heart rate was significantly lower compared to normal values, although true baseline values of conscious animals could not be determined in this study. Ninety-one percent of cats in this study were observed to have lower than normal heart rate values. In one study, heart rate in cats administ ered solely medetomidine (80 g/kg-110 g/kg) decreased to about 50% of starting values within 15-30 minutes (Vaha-Vahe 1989a). While baseline values were not obtaine d in this study, it is believed th at the measured values following induction were more than 50% of their starti ng values as a result of the cardiovascular stimulating effects of ketamine. In combination, it is thought that the central ly stimulating effects

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79 of ketamine counteract the depressive effects of alpha2 agonist compounds (Verstegen et al. 1989). In this study, heart rate was not observe d to change in males over time, but was considered below normal throughout the duration of anesthesia. Female heart rates, on the other hand, were observed to continually decrease over time to belo w normal values under anesthesia. Decreased heart rate is believed to be the resu lt of the bradycardic effects of medetomidine; however, one study concluded that medetomidine in cats did not conclusively demonstrate specific bradycardic action as a lowered state of vigilance could, in itself decrease heart rate (Stenberg et al. 1987). The obser ved bradycardia was believed to be a direct result of medetomidine as these effects were reversed fo llowing the administration of atipamezole. While the results of this study exhibite d below normal heart rate values in anesthetized cats, one study conversely found a similar dose of medetomidine and ketamine (80 g/kg M; 10 mg/kg K), without buprenorphine, to result in tachycardia between 10 an d 30 minutes following injection. Buprenorphine has been shown to decrease both bl ood pressure and heart ra te in cats, suggesting buprenorphine may have had an affect on heart ra te in this study (Benson & Tranquilli 1992). It is hypothesized that the analgesic properties of bur penorphine may have prevented an increase in heart rate and blood pressure by blocking nociceptive input in re sponse to surgical stimulus. Some clinicians prefer to preem ptively use anticholinergic drugs, such as atropine, in patients administered alpha2-adrenergic drugs, however, others disagree (Paddleford & Harvey 1999). They argue that (1) the bradycardia is a norma l physiological response to vasoconstriction and increased blood pressure, (2) anticholinergic drugs may increase myocardial work and oxygen consumption due to an increased heart rate, and (3) it may not be physiol ogically appropriate to have an increased heart rate in the face of se vere vasoconstriction (Paddleford & Harvey 1999).

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80 Normal systolic blood pressures in cats ra nge between 110 and 160 mm Hg (Muir et al 2000). Normotension was observed following the administration of MKB and throughout the duration of anesthesia in most cats. However, tw enty-three cats were observed to have systolic blood pressures rise above 160 mm Hg at least once following treatment with MKB, while 7 cats were observed to fall below 110 mm Hg at least once following treatment with MKB. Whether or not blood pressure was related to physiolo gical stress is unknown, however, blood pressure was not observed to rise consistent ly in response to surg ical stimulation. In males, a relationship between blood pressure and time could not be made with > 95 % confidence. A Type II statistical error is suspected as this observation may be the result of missing data points (at 5, 10, and 15 minutes only 10%, 60%, and 64% of data were available, respectively). Actual blood pressures may be higher than reported as the technique used in this study may underestimate systolic blood pressure by approximately 15% in cats (Grandy et al. 1992). In addition, there are no published reports assessing the accuracy of the Doppler technique when systolic blood pressure is in excess of 200 mm Hg (Dobromyl skyj 1996). Values did not exceed 200 mm Hg in this study, but some values were close (195 mm Hg). Blood pressures significantly decreased in both males and females following the reversal of me detomidine. It is hypot hesized that reversing the vasconstrictive effects of medetomidine resulted in a decrease in vascular resistance, and therefore a decrease in blood pressure. Neither blood pressure nor heart rate was obs erved to increase at any time during the surgical procedure. Similarly, in another st udy, a comparable combination although using a lesser dose of medetomidine (80 g /kg), with ketamine (10 mg/kg) reported no reflex responses to traction of the ovarian pedicl es (Verstegen et al. 1989). Base d on these observations in Phase

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81 2, it is assumed that anesthesia was adequate in the majority of cats b ecause changes suggestive of response to nociceptive stimuli, as measured by physiological variables, were not detected. Some opioids have been associated with an increase in body temperature in cats (Robertson & Taylor 2004). Alte rnatively, opioids ha ve actually been found to lower the threshold for shivering, a thermoregulatory event that is meant to increase heat production, which can further contribute to he at loss (Posner 2006). Post-anesthe tic rectal temperatures were not observed to rise significantly following bupre norphine administration in cats in a previous study (Niedfeldt & Robertson 2006). While temper atures were only collected during times of lateral recumbency in this study, no indication of measured hyperthermia (temperatures 103 F) or clinical evidence (panting) was noted. In fact, hypothermia was observed. The effects of anesthesia on thermoregulation are multifactoria l and include the loss of normal behavioral responses and an altering of normal thermoregul atory responses (Posner 2006). Temperatures in TKX treated cats (38.0 0.8C (100 1.4F) in males and 36.6 0.8C (97.8 1.4F) in females) and MKB treated cats (38.1 0.7C (100.7 1.3F) in males and 36.7 1.1C (98.3 2F) in females) were similar at the time of reversal (Cisto la et al. 2004). Loss of core body temperature occurs in three phases, the first of which is due to th e redistribution of heat from the core to the periphery, where it is then easily lost (Posner 2006 ). Higher body temperatures found in MKB cats may be attributed to the vaso constrictive properties of medetomidine as arteriovenous vasculature present in the skin contribute to ther moregulation (Posner 2006). The subsequent vasoconstriction of these shunts likely prevents heat loss from the core (Posner 2006). Core temperatures may actually have been lower than measured, as rectal temperature tends to lag behind changes in core body temp erature (Posner 2006). Nevertheless, even mild hypothermia can substantially prolong recovery times by decreasing hepatic and renal blood

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82 flow, therefore slowing the metabolism of an esthetic drugs (Posner 2006). Medetomidine elimination appears to rely heavily on biotrans formation and is likely regulated by hepatic blood flow, thus, maintenance of these metabolic proce sses is essential (Salon en 1989). The application of external heat sources duri ng surgery and recovery may reduc e the severity of prolonged recoveries and decrease recovery times; however, a logistical barrier arises when high numbers of cats are undergoing surgery a nd recovery, simultaneously. In addition, the ability to apply external heat sources from outside the trap is li mited which will likely compromise effectiveness. No observations of licking or biting at incision sites were noted. In addition, body posture and overall demeanor appeared to be co mfortable and relaxed in most cats. Immediate post-operative analgesia was assumed to be adequate as several studies have noted the efficacy of buprenorphine up to 6 hour s (Pascoe 2000; Robertson et al. 2005). There are no validated methods for pain assessment in cats, which makes evaluation and treatment difficult, however, pain can be managed on the basis of previous expe rience and intuition (Cambridge et al. 2000). Overall, the recovery times observed with MKB were shorter compared to TKX with reversal to sternal recumbency times of 72 42 minutes in cats administered TKX and 34 33 minutes in cats administered MKB in Phase 2 of this study (Cistola et al. 2004). Atipamezole administration appeared to completely reverse the effects of medetomidine, as evident by the significant increase in heart rate and decrease in blood pressure fo llowing reversal. Fourteen cats required a second injection of the reversal agen t. In dogs, the manufact urer recommends giving the same volume of atipamezole as medetomidine (5 mg/ml A: 1 mg/ml M) to reverse its effects (2007). In this study, a quarter of the volume of medetomidine was administered. This dose was sufficient in most cats; however, approximately 14% of the cats required additional reversal

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83 agent injections. Perhaps a larger volume of a tipamezole would have pr evented the need for a second reversal, although the side effects associat ed with an increased volume of atipamezole are unknown and should be considered. An unusually fast recovery, as observed in Phase 1 of this study, is unfavorable and could re sult with a larger dos e of atipamezole. Relapse to sedation is not believed to be the cause for the need for second reversal injections as the half-life of atipamezole is twice that of medetomidine (Paddleford & Harv ey 1999). Interestingly, there was no relationship between cats that received supplemental doses of MKB and cats that required an additional reversal agent injec tion. This may suggest that the initial atipamezole-medetomidine ratio was inadequate at providing acceptable recoveries in some cats. An atipamezolemedetomidine dose ratio (in mg) of 4:1 or 8:1 re sulted in speedier return to normal vigilance patterns than a 2:1 ratio in cat s receiving only medetomidine (S tenberg et al. 1993). However, one study that combined ketamine with medetomi dine recommended a dose ratio of 2.5:1 as it prevents the undesirable tachycar dia and CNS stimulation seen w ith higher doses of atipamezole (Verstegen et al. 1991b). The selected dose in Phase 2 provided adequa te duration of action in most cats. The number of cats requiring isoflurane supplemen tation was considered clinically acceptable. Approximately 11% of our study population required supplemental anesthesia. This was close to our initially set goal of less than 10% of the population requiring rescue anesthesia and the decisi on was made to initiate a fixed volume. Both fixed dose volumes (0.7 mL and 0.8 mL) of MKB were found to be inefficient at providing acceptable surgical anesthesia. Additio nally, apnea and severe respiratory depression were observed in most cats. In Phase 3, twenty -one cats (30%) required inhaled supplemental anesthesia at some point throughout the surgical pr ocedure. It is hypothesized that some of these

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84 cats may have weighed > 3.0 kg and that individual anesthetic re quirements were simply unmet. Furthermore, the 0.8 mL fixed dose was the first time anesthetists, other than those directly associated with this study, used the MKB protoc ol. In 14% of the injections, the anesthetist reported difficulty injecting the larger drug vol ume compared to the usual TKX protocol (.25 mL). Half of the cats with noted difficult inje ctions required supplemen tal anesthesia. It is hypothesized that these cats did not receive the full dose of MKB as they required supplemental anesthesia shortly after the initial MKB injection. For those weighing 3.0 kg, it remains unclear as to the differences observed in the fixed dose of MKB compared to the selected dose st udied in Phase 2. Data on the number of cats anesthetized with TKX that re quire supplemental anesthesia ar e not available; but, this information would be useful in future studies to compare the failure rates between the two protocols. Regardless, the fr equency of supplemental anesth esia and obvious physiological depressant effects observed with the fixed dos e of MKB are considered unacceptable and this protocol is not recommended. If the individual weight of a feral cat could be verified prior to an anesthesia regime, it is believed that a higher rate of success and usef ulness would be observed with the current combination of MKB. However, this would require in creased time and labor considerations. The studied combination of MKB appears to offer several advantages. Medetomidine potentiates the effects of ketamine and the disa dvantages associated with the two drugs may be offset by one another. Medetomidine makes up for the poor muscle relaxing and analgesic effects of ketamine, while the cardiovascular s timulating effects of ketamine compensate for the bradycardic tendencies of medetomi dine (Verstegen et al. 1989). The use of the medetomidines specific antagonist, atipamezole, a llows for the complete and rapi d reversal of the depressant

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85 effects exhibited by medetomidine. In addi tion, the combination of medetomidine and atipamezole may limit undesirable effects of less selective or less specif ic agonist/antagonist combinations. In conclusion, MKB appears to fulfill many of the demanding requirements necessary for feral cat anesthesia when true weight is c onsidered. In Phase 2, MKB provided a completely injectable regime that was predictable, offe red an acceptable duration of action, and provided a rapid return to normal function. The major shortcom ing of MKB in this st udy was the inability to determine an effective fixed dose volume to be used in all cats, rega rdless of true weight. Additionally, based on the high incidence of seve re respiratory depres sion observed in cats administered the fixed volume, it cannot be re commended. Moreover, it was determined that increasing the fixed dose volume further would be without regard for the safety of the animal. Although this study failed to produce an effectiv e MKB fixed dose to be used in high volume sterilization clinics, it is believed that MKB offe rs considerable promise in feral cat anesthesia. Slight changes in Operation Catnip may e nhance the effectiveness of MKB and may be of interest in further investiga tions. It is believed that the MK B combination in this study would be more effective if given in a weight-specifi c manor. The addition of a weight station would enable a dose to be calculated for each individu al cat, eliminating the ne ed for a universal fixed volume. Several categories of fixed volumes de signed to accommodate weight classes (0-1 kg, 12 kg, 2-3 kg, and > 3 kg) may prove to be benefi cial. The addition of a weight station would, however, add additional labor and time constrai nts. If an MKB dosing regime does not take weight into consideration, it is possible that MKB will never be considered appropriate for use in high-volume clinics. However, the studied comb ination of MKB may be suitable for smaller clinics with fewer surgeries performed and shorter duration of action requirements.

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86 There are approximately 1,440 combinations of MKB (based on relative doses of each drug used in cats). This study is believed to have narrowed the findings for an effective combination of MKB, although an exact fixed dos e was not accomplished. Further research is required to determine whether or not a specific combination of MKB has the ability to produce a fixed volume that fulfills the uni que demands of feral cat anesthes ia and subsequent sterilization procedures.

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87 LIST OF REFERENCES (2003) Rabies 2007. Centers for Di sease Control and Prevention http://www.cdc.gov/ncidod/dvrd/ra bies/introduction/intro.html (2007) Antisedan (atipamezole hydrochlor ide) 2007. Pfizer Animal Health http://www.pfizerah.com. Andersen MC, Martin BJ, Roemer GW (2004) Us e of matrix population m odels to estimate the efficacy of euthanasia versus trap-neuter-re turn for management of free-roaming cats. J Am Vet Med Assoc 225 1871-1876. Arnbjerg J (1979) Clinical manifest ations of overdose of ketamine -xylazine in the cat. Nord Vet Med 31 155-161. Beck CC, Coppock RW, Ott BS (1971) Evaluation of Vetalar (ketamine HCl). A unique feline anesthetic. Vet Med Small Anim Clin 66 993-996. Benson GJ, Tranquilli WJ (1992) Advantages and guidelines for using opioid agonist-antagonist analgesics. Vet Clin North Am Small Anim Pract 22 363-365. Berne RM, Levy MN, Koeppen BM et al. (2004) Physiology. Mosby, Inc., St. Louis. Berthelsen S, Pettinger WA (1977) A functional basis for classification of alpha-adrenergic receptors. Life Sci 21 595-606. Bester MN, Bloomer JP, van Aarde RJ et al. (2002) A review of the successful eradication of feral cats from sub-Antartic Marion Island, S outhern Indian Ocean. South African Journal of Wildlife Research 32 65-73. Bill R (2006) Clinical Pharmacology and Therapeutic s for the Veterinary Technician (3rd edn.). Mosby Elsevier, St. Louis, USA. Blanton JD, Krebs JW, Hanlon CA et al. (2006) Rabies surveillan ce in the United States during 2005. J Am Vet Med Assoc 229 1897-1911. Bollen PJ, Saxtorph H (2006) Cerebral state monitoring in Beagle dogs sedated with medetomidine. Vet Anaesth Analg 33 237-240. Brodbelt DC (2006) The Confidential Enquiry into Perioperative Small An imal FatalitiesDoctor of Philosophy. Royal Veterinary Co llege, University of London. pp. 269. Cambridge AJ, Tobias KM, Newberry RC et al. (2000) Subjective and objective measurements of postoperative pain in cats. Journal of th e American Veterinary Medical Association 217 685-690.

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88 Capner CA, Lascelles BD, Waterman-Pearson AE ( 1999) Current British veterinary attitudes to perioperative analgesia for dogs. Vet Rec 145 95-99. Case JB, Chomel B, Nicholson W et al. (2006) Serological survey of vector-borne zoonotic pathogens in pet cats and cats from animal sh elters and feral colonies. J Feline Med Surg 8 111-117. Castillo D, Clarke AL (2003) Trap/neuter/releas e methods ineffective in controlling domestic cat "colonies" on public lands. Nat Areas J 23 247-253. Centonze LA, Levy JK (2002) Characteristics of free-roaming cats and their caretakers. J Am Vet Med Assoc 220 1627-1633. Chang T, Glazko AJ (1974) Biotransformation and disposition of ketamine. Int Anesthesiol Clin 12 157-177. Child KJ, Davis B, Dodds MG et al. (1972) Anaest hetic, cardiovascular and respiratory effects of a new steroidal agent CT 1341: a comparison wi th other intravenous anaesthetic drugs in the unrestrained cat. Br J Pharmacol 46 189-200. Cistola AM, Golder FJ, Centonze LA et al. ( 2004) Anesthetic and physiologic effects of tiletamine, zolazepam, ketamine, and xylazine combination (TKX) in feral cats undergoing surgical sterilization. J Feline Med Surg 6 297-303. Clark KA (1988) Rabies. J Am Vet Med Assoc 192 1404-1406. Coleman JS, Temple SA, Craven SR (1997) Cats and wildlife: a conservation dilema. University of Wisconsin-Extension, Coope rative Extension,Vol. Univer sity of Wisconsin, Madison, WI. Coman BJ, Brunner H (1972) Food habits of the fe ral house cat in Victoria Journal of Wildlife Management 36 848-853. Cullen LK (1996) Medetomidine sedation in do gs and cats: a review of its pharmacology, antagonism and dose. Br Vet J 152 519-535. Dabritz HA, Atwill ER, Gardner IA et al. (2006) Outdoor fecal deposition by free-roaming cats and attitudes of cat owners and nonowners towa rd stray pets, wildlife, and water pollution. J Am Vet Med Assoc 229 74-81. Davis LE, Donnelly EJ (1968) Analgesic dr ugs in the cat. J Am Vet Med Assoc 153 1161-1167. Day TK, Muir WW, 3rd (1993) Alpha 2-adrenergic receptor agonist effect s on supraventricular and ventricular automaticity in dogs with complete atriovent ricular block. Am J Vet Res 54 136-141.

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89 Dobbins S, Brown NO, Shofer FS (2002) Co mparison of the effects of buprenorphine, oxymorphone hydrochloride, and ketoprof en for postoperative analgesia after onychectomy or onychectomy and sterilizati on in cats. J Am Anim Hosp Assoc 38 507514. Dobromylskyj P (1996) Cardiova scular changes associated with anaesthesia induced by medetomidine combined with ketamine in cats. J Small Anim Pract 37 169-172. Duke T, Cox AM, Remedios AM et al. (1994) Th e cardiopulmonary effects of placing fentanyl or medetomidine in the lumbos acral epidural space of isof lurane-anesthetized cats. Vet Surg 23 149-155. Eng TR, Fishbein DB (1990) Epidemiologic factor s, clinical findings, and vaccination status of rabies in cats and dogs in the United St ates in 1988. National Study Group on Rabies. J Am Vet Med Assoc 197 201-209. Evans A, Krahwinkel D, Sawyer D (1972) Dissoci ative anesthesia in the cat. Journal of the American Animal Hospital Association 8 371-373. Evers A, Maze M (2004) Anesthetic Pharmacology: Physiologic Principles and Clinical Practice. Churchill Livingstone, Philadelphia. Fain JN, Garcia-Sainz JA (1980) Role of phos phatidylinositol tu rnover in alpha 1 and of adenylate cyclase inhibiti on in alpha 2 effects of catecholamines. Life Sci 26 1183-1194. Fearneyhough MG (2001) Rabies postexposure prophylaxis. Human and domestic animal considerations. Vet Clin No rth Am Small Anim Pract 31 557-572. Foley P, Foley JE, Levy JK et al. (2005) Analysis of the impact of trap -neuter-return programs on populations of feral cats. J Am Vet Med Assoc 227 1775-1781. Gaynor JS, Muir WW (2002) Veterinary Pain Management. Mosby, Inc., St. Louis. Gibson KL, Keizer K, Golding C (2002) A tra p, neuter, and release program for feral cats on Prince Edward Island. Can Vet J 43 695-698. Girardet SAB, Veitch CR, Craig JL (2001) Bird and rat numbers on Little Barrier Island, New Zealand, over the period of cat eradication 1976-80. New Zealand Journal of Zoology 28 13-29. Grandy JL, Dunlop CI, Hodgson DS et al. (1992) Ev aluation of the Doppler ultrasonic method of measuring systolic arterial blood pr essure in cats. Am J Vet Res 53 1166-1169. Hanna RM, Borchard RE, Schmidt SL (1988) Phar macokinetics of ketamine HCl and metabolite I in the cat: a comparison of i.v., i.m., and rectal administration. J Vet Pharmacol Ther 11 84-93.

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96 BIOGRAPHICAL SKETCH Kelly Ann Meyer was born on October 30, 1981 in Chicago, Illinois, to Paula and Edward Meyer. An only child, she moved to Florida shortly after being born. Kelly graduated from Seminole High School in Seminole, Florida, in 20 00. In April 2005, she earned her B.S. from the University of Florida in animal sciences a nd began working toward her M.S. degree shortly thereafter. Kellys passion has always been animals and their well-being. She continues to pursue her goal of becoming a Doctor of Veterinary Medicine.