Comparison of the cardiopulmonary effects of isoflurane and sevoflurane in foals

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

MEETING ABSTRACTS

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, Louisiana,11^12 October 2001 Correspondence: Peter J. Pascoe, Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.

SMALL ANIMALS

tion in cats has a rapid onset and a dose of 10 mg kg1 produces a signi¢cant e¡ect for110 minutes.

Onset and duration of the antinociceptive activity of intravenous fentanyl in cats SA Robertson,1 PM Taylor,2 M Dixon2 and W Davies1 1 University of Florida, Gainesville, FL, USA; and 2University of Cambridge, Cambridge, UK

Systemic uptake of buprenorphine after buccal administration in cats SA Robertson,1, PM Taylor,2 M Bloom¢eld2 and JW Sear3 1 University of Florida, Gainesville, FL, USA; 2University of Cambridge, Cambridge and 3University of Oxford, Oxford, UK

Compared to other species, the data on the pharmacodynamic actions of opioids in cats are few. The time to onset and duration of the antinociceptive e¡ect of IV fentanyl (F) was studied in cats using a ramped thermal stimulus. Six young adult cats (four females, two males, mean
SD weight of 4.7
1.3 kg) were included in the study. On the day before each study, a cephalic catheter was placed, and the hair over the thorax was clipped. A small, lightweight probe was attached byVelcro to an elasticized band that was placed around the shaved thorax. Cats were accustomed to wearing the bands. The probe contained an electrical element and temperature sensor. The probe heated at a rate of 0.85 8C second1, creating a thermal stimulus. In£ating a blood pressure cu¡ incorporated into the band, to a constant pressure, ensured constant contact. The sensor output was read on a digital voltmeter. The end point was a distinct skin twitch, jump, or turn to look at the probe, at which time the thermal stimulus was stopped. A safety cut-o¡ was set at 60.5 8C. Three baseline thermal thresholds were recorded from each cat before treatment. Cats received 10 mg kg1 F, or saline (S) IV in a randomized crossover design; the total volume of all injections was 1.5 mL and the tester was blinded to treatments. Thermal threshold was tested at 5 minutes after treatment, then at 15-minute intervals for 3 hours. Fentanyl produced marked dilation of the pupils and mild euphoria. The baseline threshold for all cats was 41.5
0.95 8C. There was no signi¢cant change in thermal thresholds in the S-treated cats whereas the F-treated cats had signi¢cantly elevated thresholds for110 minutes after injection. The maximum e¡ect was seen at 5 minutes (55.3
2.15 8C). The antinociceptive action of Fafter IV administra-

Administration of drugs to cats can be challenging and simple but e¡ective techniques would be attractive to the owners. The purpose of this study was to compare the pharmacokinetics of buprenorphine (B) after buccal administration, and compare these to data previously collected from the same colony of cats after IV and IM injection. Twenty-four hours before each study, jugular catheters were inserted under iso£urane anesthesia into six adult female cats weighing between 2.9 and 4.5 kg. The buprenorphineinjectable formulation (0.01 mg kg1 ¼0.033 mL kg1) was administered into the side of the cat’s mouth. Blood was withdrawn before, at 1, 2, 4, 6, 10, 15, 30, 45, 60 minutes and at 2, 4, 6, 8, 12, and 24 hours after the drug administration. The volume of blood withdrawn was adjusted, so that <10% of the cat’s blood volume was collected over a 24-hour period. The plasma B concentrations were measured by radioimmunoassay. The noncompartmental methods were used to determine a pharmacokinetic pro¢le. The cats did not resent buccal administration of B. The mean residual time for buccal and IV dosage were 409
88 and 451
130 minutes, respectively. The Tmax after buccal administration ranged from 15 to 30 minutes and from 2 to 15 minutes after IM injection. The Cmax after buccal and IM dosing were similar (median of 7.5 and 8.5 ng mL1, respectively). Elimination half-life for the three routes of administration were comparable, but the volume of distribution was smaller, and clearance was slower after buccal administration. Comparison of pharmacokinetic data suggests100% bioavailability of buccal B. Buccal absorption of B in cats is greater than that published for people and may be an e¡ect of the di¡erences in 97

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

saliva pH between the species; human beings have a reported oral pH of 6.5 and the measured pH in this colony of cats ranged between 8 and 9. Buccal administration of B should be a useful technique for repeated analgesic dosing of cats by owners at home. The use of tiletamine–zolazepam–ketamine– xylazine anesthesia for feral cat sterilization LS Williams, JK Levy, SA Robertson, AM Cistola and LA Centonze University of Florida, Gainesville, FL, USA Trap-neuter-return programs have become a popular nonlethal alternative for the control of feral cat populations. The anesthetic used is an integral component of these programs. This study evaluated the use of tiletamine^zolazepam^ketamine^xylazine (TKX) as an IM anesthetic combination for large-scale feral cat sterilization surgery. Between July 1996 and August 2000, a total of 7502 cats entered large-scale feral cat clinics operating at the Colleges of Veterinary Medicine at North Carolina State University and the University of Florida. Up to 12 surgeries were performed simultaneously and up to 200 cats were sterilized in a single day. Cats were not weighed prior to anesthetic injection owing to their feral nature, so the initial anesthetic dose was based on estimated body weight. Tiletamine^zolazepam^ketamine^xylazine was administered IM while cats remained in their traps. Each milliliter of TKX contained 50 mg tiletamine, 50 mg zolazepam, 80 mg ketamine, and 20 mg xylazine. The cats were monitored by observation and palpation for mucous membrane color, heart rate, and respiratory rate, but these values were not recorded. Fluids were not routinely administered but were given subcutaneously in cases of dehydration or excessive blood loss. Yohimbine (0.5 mg) was administered IV at the end of the procedure, and cats were returned to their traps to recover. Cat signalment, drug use, and mortality data were analyzed retrospectively (July 1996^December 1999) and prospectively (December 1999^August 2000). Of those cats with complete drug records, more than 75% received a single dose of TKX with a mean total dose of 0.27
0.09 mL. The overall mortality rate was one in 289 cats (0.347%) and the death rate owing to unknown causes (potential anesthetic deaths) was one in 469 cats (0.213%). These results suggest that the use of TKX for large-scale feral cat sterilization clinics has several bene¢ts, including small volume of administration, predictable anesthetic quality and duration, low cost, and low mortality in feral cats.

males; 3.8^8.8 kg; 2^3 years) were anesthetized with only ISO in O2. Ventilation was spontaneous. The MAC of ISO was determined at four concentrations of N2O (0, 30, 50, and 70%) using the tail-clamp technique. The dose order of N2O was randomly assigned. The average of three measurements was considered MAC at each N2O concentration. Prior to each MAC measurement, heart rate (HR), direct arterial blood pressure (ABP), respiratory frequency ( f ), PaO2, PaCO2, pHa, PCV, total protein concentration, and the bispectral index (BIS) were determined. The esophageal temperature was kept constant [38.5
0.35 8C (mean
SD)]. A negative linear relationship between N2O and ISOMAC was demonstrated by four cats (Group 1), but not by the other eight cats (Group 2). Gender did not appear to in£uence these results. The ISOMAC (%) for Group 1 was 2.06
0.08, 1.90
0.17, 1.83
0.07, and 1.58
0.22 at 0, 30, 50, and 70% N2O, respectively, and similarly, ISOMAC for Group 2 was 1.86
0.22, 1.80
0.23, 1.84
0.19, and 1.85
0.22 at 0, 30,50, and 70% N2O, respectively. The relationships between N2O concentration and ISOMAC were signi¢cantly di¡erent for the two groups of cats ( p < 0.0001). The MAC at 70% N2O in Group1was signi¢cantly less than that at 0, 30, and 50% N2O. The relationships between N2O concentration and other physiological variables were not statistically di¡erent for the two groups of cats, so the values for the two groups were combined. In this case, an increase in HR, ABP, PCV, f, and BIS values was associated with an increase in N2O concentration and values at 70% were signi¢cantly greater than those at 0%. For example, HR, mean ABP, and PCV at 0 and 70% N2O were 174
22 versus 197
24 beats minute1;100
26 versus119
24 mm Hg; and 30
7 versus 36
7%, respectively. The PaO2 was always >100 mm Hg and PaCO2 was <46 mm Hg. These data suggest that within the cat population, there are both responders and nonresponders to the anesthetic sparing e¡ect of N2O. The present results also imply that N2O has stimulating properties out of proportion to its in£uence on ISOMAC. Hemodynamic effects of nitrous oxide in isoflurane anesthetized cats BH Pypendop, JE Ilkiw, A Imai and JA Bolich University of California-Davis, Davis, CA, USA

This study was conducted to determine the iso£urane (ISO) minimum alveolar concentration (MAC) reduction induced by nitrous oxide in cats. Twelve cats (four females, eight

Nitrous oxide (N2O) can be used as an anesthetic adjuvant in cats in an attempt to decrease the cardiovascular depression induced by potent inhalant anesthetics. However, its cardiovascular e¡ects in anesthetized cats have not, to our knowledge, been reported. Twelve healthy adult domestic short-haired cats were studied. Anesthesia was induced and maintained with iso£urane (ISO) in oxygen; ventilation was spontaneous. After instrumentation, end-tidal ISO concentration was set at 1.25 times the individual minimum alveolar concentration (MAC), determined in a previous study, and that concentration was maintained for the duration of the study. In addition, N2O was randomly administered at 0,30,50, and 70%,

98

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

Nitrous oxide does not consistently reduce isoflurane requirement in cats A Imai, JE Ilkiw, BH Pypendop,TB Farver and EP Ste¡ey University of California-Davis, Davis, CA, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

according to a Latin square design. Twenty-¢ve-minutes of stabilization were allowed after each change of concentration. The ECG (lead II) and heart rate, arterial blood pressure, pulmonary arterial blood pressure, central venous pressure, core body temperature, and inspired and end-tidal O2, ISO and N2O concentrations were continuously monitored and recorded. At selected times, pulmonary capillary wedge pressure was measured, cardiac output was determined in triplicate and averaged, and arterial and mixed venous blood samples were collected for pH and blood gas analysis, packed cell volume, total protein determinations, and lactate concentration measurement. Cardiac index, stroke index, systemic and pulmonary vascular resistance indices, rate-pressure product, and left and right ventricular stroke work indices were calculated. Data were analyzed by a repeated measures Latin square followed by a Tukey test for two-by-two comparisons. Mean arterial pressure, central venous pressure, mean pulmonary arterial pressure, packed cell volume, PaCO2, rate^pressure product, and systemic and pulmonary vascular resistance indices increased signi¢cantly with 70% N2O, compared to 0 and, for most variables,30%.Arterial and mixed venous pH decreased signi¢cantly with 70% N2O, compared to any other concentrations. The PaO2 decreased dose-dependently, according to FIO2. For 70% N2O, PaO2 was122.5
6.6 and PaCO2 was 43
3.5 mm Hg (mean
SE). The cardiac and stroke indices did not change. In conclusion, in cats anesthetized with1.25 MAC of ISO, addition of 70% N2O induced an increase in systemic and pulmonary arterial pressures, which appeared to be related to a vasoconstrictive e¡ect. Lower N2O concentrations did not signi¢cantly improve arterial pressure.

samples drawn concurrently. Accuracy of saturation readings were calculated as the root mean squared di¡erence (RMSD) (a product of bias and precision; usual human RMSD ¼ 2.5^3.5%). In dogs, the RMSD (%) for all readings were 2.7, 2.2, 2.4, 1.7, and 2.7 for NPB-395, NPB-190, NPB-290, NPB-40, and V3304, respectively. Failure to obtain readings occurred in 0, 0, 1, 0, and 20% of readings for NPB-395, NPB-190, NPB290, NPB-40, andV3304, respectively. In cats, the RMSD for all readings were 5.9,5.6,7.9,7.9, and 10.7 with failure rates of 0, 1, 0, 20, and 32% for NPB-395, NPB-190, NPB-290, NPB-40, and V3304. In cats, when SaO2 was >90%, the RMSD were 2.6, 4.4, 4.0, 3.5, and 4.8 with failure rates of 0, 2, 0, 25, and 43% for the NPB-395, NPB-190, NPB-290, NPB-40, and V3304. All the monitors were reasonably accurate in dogs. Large variability occurred in cats, but accuracy was acceptable when SpO2 was >90% Cardiorespiratory effects of intravenous morphine, xylazine and atropine in dogs JR Dodam, LA Cohn, HE Durham and B Szladovits University of Missouri, Columbia, MO, USA

Evaluation of pulse oximeters over a wide range of hemoglobin saturation is very limited in dogs and cats. This study evaluated ¢ve models of pulse oximeters for accuracy in dogs and cats. Five dogs and ¢ve cats were anesthetized (propofol, iso£urane) and instrumented with peripheral arterial catheters. The PaO2 was measured at the beginning and end of anesthesia. The Nellcor Puritan Bennett NPB-395, NPB-190, NPB-290, NPB-40 and Surgi-Vet V3304 were attached to veterinary probes at ¢ve sites in the body (5  5 Latin square design).The sites in dogs’ body were the tongue, lip, ear, toe and prepuce or vulva. In cats; the tongue, lip, ear, metacarpus and metatarsus were used. Ten readings (SpO2) were taken at each of three hemoglobin saturation values (98, 85, and 72% achieved by adding nitrogen into the circuit) from each site in each animal. The SaO2 was measured by a co-oximeter (set in cat or dog mode and calibrated with manufacturer’s QC solutions) from arterial

The IV injection of xylazine (0.4 mg kg1), morphine (0.4 mg kg1) and atropine (0.02 mg kg1) is frequently used to provide short-term sedation and analgesia for canine patients at our hospital. The purpose of the present investigation was to assess the cardiopulmonary e¡ects of this combination. Six hound dogs (weight 27
3 kg) had the skin over the ventral neck and dorsal metatarsus surgically prepared and anesthetized with lidocaine. Central venous and arterial catheters were percutaneously placed into the jugular vein and dorsal pedal artery, respectively. Baseline measurements of respiratory rate (RR), heart rate (HR), rectal temperature, direct systemic arterial pressure (SAP, MAP, DAP), central venous pressure (CVP), and arterial blood gas analysis were obtained. The 2-D, M-mode, and Doppler echocardiography were used to obtain or calculate fractional shortening and cardiac output. Level of alertness and resistance to handling were quanti¢ed on an analog scale. The drug mixture was given, and measurements repeated at 5, 15, 30, and 60 minutes. A repeated measures ANOVA was used to detect di¡erences over time, and Dunnett’s test was used for multiple comparisons when signi¢cance was reached ( p < 0.05). Respiratory rate was signi¢cantly decreased below baseline after drug administration, PaCO2 increased to 50
3 mm Hg (mean
SD) at 60 minutes, and pH decreased to 7.31
0.01at15 minutes PaO2 was una¡ected. The HR was decreased at 30 and 60 minutes and MAP was increased 5 minutes after drug administration. Fractional shortening and cardiac output were decreased and preinjection period/ejection time was increased by drug administration. Level of consciousness and resistance to restraint were decreased at all times after drug administration.

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

99

Evaluation of pulse oximeters in dogs and cats NS Matthews,1, S Hartke1 and JC Allen2 1 Texas A & M University, College Station, TX and 2Mallinckrodt Inc., Hazelwood, MO, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

The IV combination of xylazine, morphine, and atropine caused moderate cardiopulmonary dysfunction and reliable short-term sedation in dogs. Effects of oxymorphone and hydromorphone on isoflurane minimum alveolar concentration in dogs CEG Machado and DH Dyson University of Guelph, Guelph, Ontario, Canada The purpose of this study was to assess if the iso£urane (ISO) minimum alveolar concentration (MAC) in dogs is reduced when combined with either oxymorphone (OX) or hydromorphone (HY). We used six healthy, mixed-breed dogs (1^3 year, 17.5^ 31.0 kg) on three occasions in a randomized crossover study (at least1 week between treatments). Following mask induction with ISO in 33% oxygen (þN2O), anesthesia was maintained with ISO in 100% O2 (F-circuit) using mechanical ventilation to achieve eucapnia (PaCO2 35^45 mm Hg). The dogs were assigned to receive: OX at 0.05 mg kg1, HY at 0.1 mg kg1 or 1 mL of saline (control). The test drug was administered IVand a minimum of15 minutes was allowed before the ¢rst MAC assessment. The dog was equilibrated at each end-tidal ISO for at least 15 minutes. An electrical stimulus (50 Vat 50 cycles second1 for 10 ms) was applied for up to 1 minute to the toe web with a Grass stimulator to determine if purposeful response could be elicited. Adjustment of ISO vaporizer setting was made according to the response. The end-tidal ISO concentration midway between that allowing movement and that preventing it was the MAC for each treatment. If the ¢rst MAC was achieved before 1.5 hour after drug administration, it was con¢rmed to be the same at 1.5 hours (MAC-1.5 hour). Each dog remained anesthetized and MAC determination was repeated starting 3 hours after test drug injection. Final ISOMAC was con¢rmed at 4.5 hours if achieved earlier (MAC-4.5 hour). Two individuals, unaware of the treatment given, performed and agreed upon all assessments. Analysis of variance (mixed model) showed a signi¢cant drug^time interaction ( p < 0.0001). A Tukey analog compared the drugs at each time and between  times (signi¢cance at p < 0.05 from control is reported).   MAC-1.5 hour was1.2% (control),0.68% (OX),0.62% (HY).  TheMAC-4.5 hourwas1.1%(control),0.96%(OX),0.75% (HY). It was concluded that OX and HY signi¢cantly reduce ISOMAC in dogs at1.5 hours. After 4.5 hours of anesthesia HY has a signi¢cant ISOMAC sparing e¡ect, whereas OX does not. Cardiovascular and subjective evaluations of oxymorphone/diazepam and hydromorphone/ diazepam induction in experimentally induced hypovolemic dogs CEG Machado and DH Dyson University of Guelph. Guelph, Ontario, Canada The purpose of this study was to assess neuroleptanalgesic induction in experimentally induced hypovolemic dogs (removal of 30 mL kg1 of blood over 30 minutes). 100

Six healthy dogs (17.5^31 kg) were randomlyassigned in a crossover design to receive oxymorphone/diazepam (OD) or hydromorphone/diazepam (HD) with at least 3 weeks between trials. Dogs were anesthetized with iso£urane (ISO) in 33% oxygen (þN2O) by mask, maintained using controlled ventilation (CV) with ISO in 100% O2 for instrumentation [tracheal end-tidal gases (Criticare1100), HR, BP, thermodilution CI, CVP, pulmonary artery pressure (PAP), temperature (T) and blood gas measurements]. Normovolemic (NV) values were obtained following this and equilibration of 15 minutes at 1.8% end-tidal ISO (1.5 MAC). The percentage ISO was reduced as hypovolemia was induced and then the dogs were allowed to recover. Measurements were repeated after the dog was walking (HV) ^ at least 15 minutes after recovery. The dogs received IV oxymorphone 0.05 mg kg followed by diazepam (0.2 mg kg) (OD) or hydromorphone 0.1 mg kg1 followed by diazepam (0.2 mg kg1) (HD) and were reassessed, including subjective evaluation for depth. The opioid dose (OpD) was repeated after 5 minutes. A person, blind to the treatment, evaluated depth and ease of intubation (after 5 minutes). Other measurements were taken, endotracheal intubation performed, and 0.9% end-tidal ISO provided with CV. After 15 minutes equilibration, measurements were repeated. Glycopyrrolate (GL) 0.01 mg kg1 was given IV and the last measurements taken 10 minutes later. Dogs received half of the blood removed þ remaining volume  3 as crystalloid during recovery. Opioid/diazepam e¡ect occurred by 1 minute in all dogs. Intubation would not have been possible in 1/6 (HD, OD) with initial dose. All dogs were intubated after whole opioid dose (3/6 HD and 2/6 OD were more di⁄cult). An ANOVA for repeated measures was performed on changes produced with di¡erent interventions over time (e.g. HV^ OpD) with signi¢cance if p  0.015. The OpD resulted in a signi¢cant change (mean di¡erence
SE)inHR(HD  41
10b.p.m.;OD,30
12b.p.m.),diastolic BP (HD  5
5 mm Hg), pH (HD  0.10
0; OD  0.09
0), PaCO2 (HD þ 13
0.8 mm Hg, OD þ 15
1.5 mm Hg) compared to HV.Transfer of HVdogs to ISO resulted in changed CI (HD  30
6 mL kg1 minute1), BE (HD  2.5
0.6 mEq L1; OD  2.7
0.5 mEq L1) and T (OD 1.0
0.25 8C) compared to NV. Administration of GL changed HR (HD þ 50
9 b.p.m.; OD þ 42
13 b.p.m.), systolic BP (HD, 23
5 mm Hg) and SV index (HD, 0.4 mL kg1 minute1). The PAP values were di⁄cult to interpret but tended to be lower in OD following HV. The HD and OD provide comparable induction following hypovolemia. The GL reversal of opioid bradycardia provides no advantage in hypovolemic dogs. Bispectral index in dogs anesthetized with isoflurane: comparison with sevoflurane SA Greene, GJ Benson,WJ Tranquilli and KA Grimm University of Illinois, Urbana, IL, USA Bispectral index (BIS) is a numerical value derived from the EEG that is used clinically by anesthesiologists to assess Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

CNS depression in human beings. In a previous study, canine BIS values were inversely related to end-tidal sevo£urane (SEVO) concentration: BIS ¼ 102.7  (14.2  [SEVO]); R2 ¼ 0.754. The purpose of this study was to determine the relationship between BIS and end-tidal iso£urane (ISO) in the same dogs used in the SEVO study. ISO minimum alveolar concentration (MAC) was determined using the tail-clamp technique for six English pointer dogs (three males and three females) with a mean
SD age and weight of 3.7
2.0 years and 20.2
4.8 kg, respectively. One weekafter MAC determination, BIS was measured at 0.8, 1.0, 1.5, and 2.0 MAC multiples of ISO.Ventilation was controlled and atracurium (0.2 mg kg1 followed by 6 mg kg1 minute1 IV) was administered to eliminate EMG artefact from the EEG. The BIS was determined using an A-2000 monitor (Aspect Medical Systems Inc.). After a 15-minute equilibration period, BIS data were collected for 5 minutes and median BIS values were calculated. Heart rate, direct mean arterial blood pressure (MAP), esophageal temperature, and arterial blood gases were measured at each BIS collection period. End-tidal CO 2 and percentage [ISO] were monitored using a calibrated infra-red gas analyzer. Data were analyzed using RM ANOVA ( p < 0.05). The mean ISOMAC value was 1.3
0.2%. The BIS values were inversely related to [ISO]: BIS ¼ 93.9  (25.2  [ISO]); R2 ¼ 0.614. Mean
SD BIS values at 0.8, 1.0, 1.5, and 2.0 MAC were 65
8, 60
7, 52
3, and 15
27, respectively. At 2 MAC, three dogs had burst suppression that prevented reliable BIS determination.The BIS values were signi¢cantly higher during SEVO at 0.8 and 1.0 MAC compared to ISO. Minor, yet statistically signi¢cant, di¡erences between and within anesthetic groups were observed for cardiovascular and arterial blood gas data. We conclude that a predictive relationship exists between BIS and end-tidal [ISO]. However, BIS correlated with endtidal [SEVO] better than with [ISO]. The BIS appears to be somewhat agent dependent in this group of six dogs. Clinical use of BIS monitoring in dogs may require evaluation of speci¢c anesthetic drug combinations.

after trachael extubation, heart rate, respiratory rate, rectal temperature were obtained, and a single observer blinded to treatment assessed pain, lameness, trachael sedation and temperament. Owners assessed pain in their cats approximately 48 and 72 hours after trachael extubation. All cats were given acepromazine (ACE, 0.025 mg kg1), BUT (0.2 mg kg1), ketamine (5 mg kg1) and glycopyrrolate (0.01 mg kg1) IM and anesthesia was induced and maintained with iso£urane in O2. Front-limb onychectomy was performed by disarticulating P3 using sharp dissection with a scalpel. Nine cats in the BUT group and two in the PMB group were also simultaneously castrated. BUTor PMB was administered, and the front limbs were bandaged. Acepromazine or BUT were administered as necessary to treat pain or dysphoria in the postoperative period. A RM ANOVA and Wilcoxon rank sum test were used to analyze physiologic and categorical data, respectively. There was decreased requirement for ACE and/or BUT in the postoperative period for PMB cats (1.3
1 doses 24 hours1 (mean
SD) for BUT versus 0.6
0.6 doses 24 hours1 for PMB), and overall pain score was better in the PMB group. Behavior score at extubation was also better in the PMB group. Lameness at 24 hours was not di¡erent between groups, and owners’ assessment of postoperative pain was not di¡erent between groups. The local injection of PMB resulted in improved analgesia and a decreased requirement for postoperative pain medication in the early postoperative period. Preliminary evaluation of pain behaviors following neutering in dogs: effect of acepromazine dose PW Hellyer, GA Keeler, HE Everding III, JS Gaynor, AE Wagner, and C Glawe Colorado State University, Fort Collins, CO, USA

The purpose of this investigation was to compare the analgesic e¡ectiveness of a long-acting phospholipidencapsulated microcrystalline bupivacaine (PMB) preparation to butorphanol after onychectomy in cats. After obtaining informed owner consent and after physical examination, cats were randomly assigned to one of the two treatment groups: butorphanol (BUT, 0.4 mg kg1 IM; n ¼ 22) or local injection/application of PMB (5 mg kg1; n ¼ 23). Prior to surgery and at 0, 0.5,1, 2, 4,8, and 24 hours

The purpose of this study was to determine an acceptable dose of acepromazine (ACE) to be used in a large-scale study of pain behaviors following neutering in dogs. The objectives were to ¢nd a dose of ACE that was high enough to provide some sedation to facilitate induction and recovery from anesthesia without causing prolonged recovery that would prevent evaluation of postoperative pain behaviors, and to gain experience with the pain scales to be used in the study. Sixty dogs (33 males, 27 females),1.36
0.16 years of age and weighing 14.3
1.29 kg (mean
SEM) were the subjects of this study. Dogs were pre-medicated with glycopyrrolate (0.02 mg kg1 SQ) and randomly administered ACE at 0.025 mg kg1 SQ (LOW) or 0.05 mg kg1 SQ (HIGH). Approximately 30 minutes later, anesthesia was induced with diazepam (0.56 mg kg1 IV) and ketamine (11.1 mg kg1 IV) and maintained with iso£urane. The pain behaviors were evaluated for the ¢rst 4 hours of recovery using the University of Melbourne Pain Scale (UMPS) and Glasgow Composite Pain Tool by an observer unaware of ACE dose. Treatment groups were compared using an unpaired t-test, with p < 0.05 considered signi¢cant.

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

101

Phospholipid-encapsulated bupivacaine and analgesia after onychectomy in cats JR Dodam,1, B Boedeker,2 M Gross,1, KR Branson1, and GL Carroll3, 1 University of Missouri, Columbia, MO, 2AugustaVA Medical Center and Medical College of Georgia, Augusta, GA; and 3Texas A & M University, College Station,TX, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

Duration of anesthesia (25.4
1.5 minutes), duration of surgery (12.4
1 minutes), and length of incision (2.7
0.14 cm) were not di¡erent between treatment groups. Duration of surgery for females (14.2
1.1 minutes) was not di¡erent than males (11
1.6 minutes). Cumulative pain scores (UMPS) over the 4-h observation period for LOW (49.1
1.9) and HIGH (49.7
2) dose ACE were not signi¢cantly di¡erent. The results of this study suggest that ACE at 0.025 mg kg1 SQ a¡ects pain behaviors similarly to ACE at 0.05 mg kg1 SQ. Recognizing that the ACE can induce profound sedative e¡ects when combined with opioid analgesics, the low dose of ACE was chosen for the subsequent analgesic study. In this preliminary study, the UMPS had the advantage of providing a numeric value for comparison of pain scores, whereas the Glasgow Composite Pain Tool was easier to use, requiring less observer interpretation of behaviors. The influence of inhaled anesthetic and body temperature on serum fentanyl concentrations with transdermally administered fentanyl in anesthetized dogs G Pettifer, J Smith, G Hosgood, G Gomila and P Conlon Louisiana State University, Baton Rouge, LA, USA

mean (
SEM) serum fentanyl concentrations for both hypothermia treatments (Iso^Hypo ¼ 1.102
0.3 ng mL1; Hal^Hypo ¼ 0.957
0.2678) were signi¢cantly lower than baseline concentrations (Iso^Hypo ¼ 2.194
0.3133 ng mL1; Hal^Hypo ¼ 1.991
0.4253). This signi¢cant reduction persisted for the duration of anesthesia for the Iso^Hypo treatment. For the Hal^Hypo group, this reduction was signi¢cant only at t ¼ 1, 1.5 and 2 hours. Serum fentanyl concentrations returned to baseline levels within 1 hour of the end of anesthesia, regardless of body temperature. Analysis of covariance demonstrated a signi¢cant e¡ect of inhalant choice; overall, iso£urane-anesthetized animals had signi¢cantly lower fentanyl concentrations than halothane-anesthetized animals during the anesthetic period.

Postoperative arterial blood gases in spay/ castration dogs: a comparison of butorphanol versus hydromorphone VL Campbell, KJ Drobatz and SZ Perkowski University of Pennsylvania, Philadelphia, PA, USA

This investigation was designed to determine if: (a) hypothermia during 4 hours of anesthesia signi¢cantly in£uences the peri-anesthetic serum concentration of transdermally administered fentanyl, and (b) there is a signi¢cant di¡erence between the peri-anesthetic serum concentrations of transdermally administered fentanyl in dogs anesthetized with halothane compared to dogs anesthetized with iso£urane. Six dogs [10.65
0.43 kg (mean
SEM)] were used in a randomized-crossover design with four treatments: iso£urane þ normothermia (Iso^Norm), iso£urane þ hypothermia (Iso^Hypo), halothane þ normothermia (Hal^Norm), halothane þ hypothermia (Hal^Hypo). A 50-mg hour1 fentanyl patch was applied to the thorax 36 hours prior to the induction of anesthesia. At t ¼ 0, anesthesia was induced with either halothane or iso£urane. Dogs trachae were intubated, connected to a non-rebreathing system and maintained at 1.5 times MAC with a fresh gas £ow rate of 200 mL kg1 minute1. The dogs breathed spontaneously throughout the 4-hour anesthetic period. Animals in the hypothermia treatments were actively cooled to 35.5 8C following induction of anesthesia. Hemodynamic parameters, arterial blood gases, and end-tidal gases were monitored.Venous blood samples (jugular) for serum fentanyl analysis (Coat-A-Count Fentanyl RIA) were drawn at: 36, 24, 12, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 18, and 26 hours. The mean (
SEM) temperatures during the anesthetic period for the four treatments were: Iso^Norm ¼ 37.7
0.075 8C, Iso^Hypo ¼ 35.8
0.15 8C, Hal^Norm 37.7
0.06 5 8C, and Hal^Hypo ¼ 35.8
0.135 8C. At t ¼ 1 hour the

This study compared the frequency and severity of postoperative (postop) hypoxemia and hypercarbia in healthy dogs receiving butorphanol (BU) versus hydromorphone (HY). All dogs were admitted for neutering and proved normal on physical examination, CBC, creatinine, and preoperative (preop) arterial blood gas (ABG). Dogs received 0.02 mg kg1 acepromazine and 0.01 mg kg1 glycopyrrolate, with 0.4 mg kg1 BU (BU dogs, n ¼ 10) or 0.2 mg kg1 HY (HY dogs, n ¼ 10) IM preop. Despite BU and HY being equipotent on a per weight basis, they are not necessarily equianalgesic. Therefore, clinically accepted dosages of BU and HY were used. Anesthesia was induced with 2^4 mg kg1 thiopental boluses IV to e¡ect, and maintained with iso£urane (ISO) and O2. A catheter was placed in the dorsal metatarsal artery. The POET agent monitor with proximal endotracheal side-stream sampling measured end-tidal 0 0 FE ISO and CO 2. The FE ISO was targeted between 0.9 and 1.5% and the ETCO2 between 30 and 45 mm Hg using PPV or IPPV. An intraoperative (intraop) ABG was obtained during stage III anesthesia 10^30 minutes prior to extubation. The BU dogs received 0.4 mg kg1 BU and HY dogs 0.1 mg kg1 HY IM prior to extubation. Post-extubation, an ABG, HR, RR, temperature, pulse quality, MM color, CRT, and nonblinded pain/sedation scores were obtained by the primary investigator at 10 minutes, 30 minutes, 1, 2, 3, and 4 hours. Anesthesia time, age, and weight for BU dogs were 119
36.3 minutes, 1.9
2.7 years, and 24.1
8.4 kg and for HY dogs 170
64.7 minutes, 0.93
0.77 years, and 21.5
10.3 kg, respectively. Student’s t-test was used for statistical analysis on normally distributed data and the sign rank test on the A-a gradient data. Statistical signi¢cance was assigned for values of p < 0.05. Data are reported as mean
SEM.

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Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

In the HYdogs, PaCO2 was signi¢cantly higher compared to preop (preop PaCO2 ¼ 36.9
2.6 mm Hg) at 10 minutes, 30 minutes, 1, 2, and 3 hours (mean PaCO2 range ¼ 41.0^ 44.3 mm Hg). No di¡erences were found in PaCO2 of the BU dogs compared to preop. PaCO2 was signi¢cantly higher at 1and 2 hours in the HYdogs (44.6
3.1and 42.8
3.1 mm Hg, respectively) compared to the BU dogs (39.8
4.2 and 39.4
2.0 mm Hg, respectively).The PaO2 was signi¢cantly lower at 30 minutes compared to preop for the BU dogs (96.7
7.6 mm Hg versus100.2
8.1 mm Hg) and at 1 hour compared to preop in the HY dogs (90.9
10.4 mm Hg versus 101.4
4.0 mm Hg). The A-a gradient was signi¢cantly higher at 30 minutes compared to preop for the BU dogs (9.5
7.4 versus 5.5
6.2). No di¡erences in all other measured parameters were seen. Although HY caused more hypoventilation postop than BU and transient decreases in PaO2 occurred in both groups, mean PaCO2, PaO2, and A-a gradients remained clinically acceptable. The changes are statistically, but not clinically, signi¢cant. Future studies in compromised dogs should be performed.

postoperatively in a similar manner for both groups. There were no signi¢cant postoperative di¡erences in cortisol levels or any measured variable. It appears that the scoring system used was not sensitive enough to detect di¡erences in pain between a known analgesic and a placebo.

The analgesic effects of butorphanol and meloxicam after elective ovariohysterectomy in dogs N Caulkett, M Read, D Fowler and C Waldner University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Carprofen is an oral nonsteroidal anti-in£ammatory drug commonly used for treatment of chronic osteoarthritic pain. The injectable formulation has some e⁄cacy for treatment of acute surgical orthopedic pain. The purpose of this project was to assess the e⁄cacy of oral preoperative carprofen for control of postoperative pain in dogs undergoing knee surgery for repair of ruptured cranial cruciate ligaments. This was a randomized, placebo controlled, parallel study that investigated the e¡ectiveness of carprofen compared to placebo. Nineteen dogs, presented to the CSU VTH, were entered into the study and randomly assigned to the carprofen (C) (n ¼ 10) or placebo (P) (n ¼ 9) group. Dogs received either a loading dose of carprofen (2.2 mg kg1 PO BID) or placebo starting 24 hours prior to surgery including the morning of surgery. The placebo contained lactose and liver £avoring. Pain was assessed using a pain scoring system, visual analog scale, and a loaded pressure threshold device preoperatively, and at 1, 2, 4, 6, 24, and 48 hours and 10 and 21 days postoperatively. The treatment continued for 21 days. Blood for cortisol analysis was drawn at all assessment times. Data were analyzed using a likelihood-based mixed e¡ect model repeated measures. Data were considered signi¢cant if p < 0.05. Eight of10 C dogs and 5/9 P dogs were given at least1dose of morphine. The mean relative dose of morphine was greater in the C group at 1 hour ( p ¼ 0.01) and 24 hours ( p ¼ 0.02). The heart rate and respiratory rate decreased

This study was designed to compare the analgesic e¡ects of meloxicam and butorphanol following elective ovariohysterectomy. Group A (15 dogs) was pre-medicated with 0.05 mg kg1 IM of acepromazine plus 0.2 mg kg1 SC of meloxicam. Group B (15 dogs) was pre-medicated with 0.05 mg kg1 IM of acepromazine plus 0.2 mg kg1 IM of butorphanol. Both groups were induced to anesthesia with approximately 10 mg kg1 of thiopental and maintained on halothane in oxygen. All of the ovariohysterectomies were performed by a faculty surgeon or senior surgical resident. Following surgery, the dog was maintained in the recovery area for observation. All pain measurements were performed by one experienced individual. The observer was blinded to treatment. Pain scores (0^10) and VAS scores were performed at 2, 3, 4,6,12, and 24 hours post-premedication. An analgesiometer was used to determine the pressure required to produce an active avoidance response to pressure applied at the incision line. The analgesiometer was applied after the determination of pain and VAS scores. The association between treatment status (meloxicam or control), sample time and pain,VAS or analgesiometer scores were analyzed using a generalized estimating equation (GEE) method to account for over dispersion within the data resulting from the repeated measures design. Mucosal bleeding times were performed prior to pre-medication, and at 6 and 24 hours post-premedication. The 6 and 24 hour readings were compared to baseline with a paired t-test. Any animal with a pain score >3 received rescue analgesia (butorphanol 0.2 mg kg1 IM). Data from these animals, up to rescue analgesia, was included in the analysis. A signi¢cance level of p < 0.05 was considered signi¢cant. Surgery time was 27
16 minutes in the meloxicam group and 26
8 minutes in the butorphanol group. The animals in group A (meloxicam) demonstrated signi¢cantly lower pain and VAS scores, compared to group B. There was no di¡erence in analgesiometry scores and mucosal bleeding times did not change signi¢cantly with either treatment. Two animals required rescue analgesia. Both of these animals were in group B. Results of this study suggest that 0.2 mg kg1 of meloxicam will provide superior analgesia to 0.2 mg kg1 of butorphanol in dogs following ovariohysterectomy.

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

103

The effect of preoperative oral carprofen on postoperative pain in dogs undergoing knee surgery JS Gaynor, K Wander, C Mallinckrodt, G Baker and S Brevard Colorado State University, Fort Collins, CO, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

HORSES Quantification of dose-dependent respiratory depression in isoflurane-anesthetized horses RJ Brosnan, A Imai and EP Ste¡ey University of California-Davis, Davis, CA, USA The magnitude of respiratory depression in equidae anesthetized with iso£urane has not been thoroughly described. The aim of this study was to quantify changes in ventilation as a function of iso£urane (ISO) dose in the horse. Anesthesia was induced and maintained in ¢ve healthy adult horses weighing 564
52 kg (mean
SD) in left lateral recumbency using only ISO in O2. During spontaneous ventilation, four doses of constant end-tidal ISO measured by a calibrated infra-red analyzer were studied in randomized order: 1.31, 1.57, 1.83, and 2.10%; corresponding to the minimum alveolar concentration (MAC), 1.2 MAC, 1.4 MAC, and 1.6 MAC, respectively. The PaO2 and PaCO2 were measured using an automated blood gas analyzer and corrected to tonometrically derived standard curves. Respiratory rate ( f ) and tidal volume (VT) were measured via calibrated signal integration from a Silverman-style pneumotachometer; volumes were corrected to BTPS. Minute ventilation (VE) was the calculated product of VT and f. Data were analyzed using a repeated measures ANOVA;Tukey’s test was used for pairwise comparisons ( p < 0.05). The following results are listed in order of ascending MAC multiples: PaCO2 (mm Hg) ¼ 68
14, 68
9, 72
9, 78
5; f (min1) ¼ 4.3
2.4, 3.5
1.6, 2.5
1.0, 2.0
0.7; VT (mL kg1) ¼ 23
11, 22
11, 22
12, 21
7; V4E (mL minute1 kg1) ¼ 84
41,67
27,50
23,39
11. Significant di¡erences were observed between the highest and lowest MAC multiples for PaCO2, f, and VE, but not for VT. The PaO2 was always >80 mm Hg. The equations given below express median minute ventilation and median PaCO2 as a function of ISOMAC. Median values at each dose were used instead of mean values owing to the departure from sample variance uniformity. The yintercepts coincide with published reports of V4E and PaCO2 for awake, unmedicated horses (0 MAC). The x-intercept of Equation 1 predicts respiratory arrest at 2.4 MAC, near the apneic threshold for ISO. Future work directed towards increasing sample size in this study may remedy heterogeneous treatment variances present within the data and permit further re¢nement of dose^ventilation relationships in the horse. V4E ¼ 49  MAC þ 121

(1)

PaCO2 ¼ 22  MAC þ 39

(2)

Comparison of the cardiopulmonary effects of isoflurane and sevoflurane in foals

Six healthy 1^3-month-old foals (75^163 kg) that were undergoing two minor orthopedic procedures were randomly anesthetized with ISO or SEV in a crossover design. After induction with the inhalation agent in oxygen, foals were placed in dorsal recumbency and 0.1 mg kg1 butorphanol was administered IV to provide intraoperative analgesia. A 7 Fr 110 cm triple-lumen balloon catheter was advanced through a 8 Fr introducer in a jugular vein until the balloon was wedged in the pulmonary artery. The lungs of each foal were ventilated to maintain normocapnia. During the period of data collection, there was no surgical stimulation and individual depth of anesthesia was adjusted to maintain a weak palpebral re£ex (expired ISO 1.45
0.06%, SEV 2.34
0.14%). Measured parameters for the study included heart rate, direct systemic arterial pressure, central venous pressure, cardiac output, direct pulmonary arterial pressure, pulmonary wedge pressure, arterial and venous pH, HCO 3, and O2 and CO2 tensions, tidal volume, minute ventilation, and temperature. Measured parameters were used to calculate systemic vascular resistance, pulmonary vascular resistance, cardiac index, stroke volume, stroke index, arterial and mixed venous oxygen contents, oxygen delivery, oxygen consumption, extraction ratio, shunt fraction, and physiological dead space. Baseline data were recorded at15 minutes after anesthetic agent was ¢rst introduced. Data were recorded every15 minutes after baseline until 60 minutes, and arterial and mixed venous blood gas samples were collected at baseline, 30 minutes, and 60 minutes. After the¢naldatawerecollectedat60 minutes, surgery commenced. Data were analyzed for normality, and were compared using a two-way ANOVA and Bonferroni’s test. Signi¢cant di¡erences between drugs were taken if p ¼ 0.05. No signi¢cant di¡erences in any of the measured or calculated parameters were observed between ISO and SEV during this study. Sample data for ranges of mean values included: heart rate (ISO 63^67 beats minute1, SEV 68^73 beats minute1), mean arterial pressure (ISO 46^96 mm Hg, SEV 44^83 mm Hg), cardiac index (ISO 93^116 mL kg1 minute1, SEV 100^117 mL kg1 minute1), mean pulmonary pressure (ISO 10^23 mm Hg, SEV 13^19 mm Hg). Based on the results of this study, both ISO and SEV will provide comparable maintenance of anesthesia in 1^3-monthold foals. Comparison of induction and recovery in foals anesthetized with isoflurane or sevoflurane MR Read, EK Read,T Duke and DG Wilson University of Saskatchewan, Saskatoon, Saskatchewan, Canada

The purpose of this study was to compare the cardiopulmonarye¡ects of iso£urane (ISO) and sevo£urane (SEV) in foals.

The purpose of this study was to compare the induction and recovery characteristics of iso£urane (ISO) and sevo£urane (SEV) in foals undergoing two minor orthopedic procedures. Six healthy 1^3-month-old foals (75^163 kg) were randomly anesthetized with ISO or SEV in a crossover design. Each foal was nasotracheally intubated while concious,

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MR Read, EK Read,T Duke and DG Wilson University of Saskatchewan, Saskatoon, Saskatchewan, Canada

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

followed by connection of the endotracheal tube to a rebreathing circuit with an out-of-circuit, agent-speci¢c vaporizer. Oxygen £ow was maintained at 40 mL kg1 minute1, and the vaporizer was immediately dialed to deliver the maximum concentration for the vaporizer (5% for ISO, 7% for SEV). Foals were allowed to ventilate spontaneously, and the inspired and expired concentrations of the agents were measured continuously during induction with a gas analyzer (Poet IQ, Criticare Systems). Time to recumbency, number of breaths to recumbence, induction score from a blinded observer (0 ¼ smooth, 1 ¼ mild excitement/struggle, 2 ¼ moderate excitement/struggle, 3 ¼ marked excitement/struggle), and maximum inspired and expired concentrations of each agent were recorded. Prior to surgery,0.1 mg kg1 butorphanol was administered IV. Total duration of anesthesia and surgery were similar between groups (ISO 142
19 minutes, SEV 134
15 minutes) and foals were ventilated to maintain normocapnia during this time. Vaporizer settings were adjusted to maintain a surgical plane of anesthesia (¢nal expired gas concentration before recovery ^ ISO 1.5
0.13%, SEV 2.4
0.22%). At the conclusion of surgery, foals were disconnected from the circuit. Time taken to ¢rst movement, to swallowing, and to standing, and recovery score (same observer and scale as for induction score) were recorded. Data were analyzed for normalcy and compared using paired t-tests. Signi¢cance was taken if p ¼ 0.05. There were no statistically signi¢cant di¡erences for induction parameters: maximum inspired multiple of MAC (ISO1.81
0.33 versus SEV1.56
0.59, p ¼ 0.32), maximum expired multiple of MAC (ISO 1.17
0.22 versus SEV 1.16
0.34, p ¼ 0.98), time to recumbency (ISO 2.1
0.5 minutes versus SEV 2.5
0.95 minutes, p ¼ 0.44), number of breaths to recumbency (ISO 45
13 versus SEV 73
32, p ¼ 0.10), induction scores (ISO 1.67
0.81 versus SEV 1.5
0.83, p ¼ 0.74). There were also no di¡erences for recovery parameters: time to ¢rst movement (ISO 3.2
2.3 minutes versus SEV 4.1
1.5 minutes, p ¼ 0.43), time to swallow (ISO 4.8
2.5 minutes versus SEV 4.6
1.1 minutes, p ¼ 0.87), time to standing (ISO 12.5
4.5 minutes versus SEV 9.2
1.5 minutes, p ¼ 0.18), recovery score (ISO 1.67
0.51 versus SEV 1.33
0.81, p ¼ 0.36). Based on the results of this study, using nasotracheal intubation, ISO and SEV will provide comparable induction of, and recovery from anesthesia in foals.

gradient between brain and heart. It was, therefore, hypothesized that ISO-anesthetized horses in lateral recumbency would have increased intracranial pressure (ICP) and decreased CPP compared to standing, unmedicated horses. Anesthesia was induced and maintained in six healthy horses in left lateral recumbency using only ISO in oxygen. Central venous pressure (CVP) from the right atrium and MAP from the right carotid artery were recorded on a calibrated physiograph. A Codman Microsensor ICP transducer was placed in the subarachnoid space through a right parietal craniotomy. The PaO2, PaCO2, and pHa were obtained using an automated blood gas analyzer with values corrected to tonometrically derived standard curves. Horses were ventilated to 18^22 cm H2O inspiratory pressure and 0^2 cm H2O end-expiratory pressure. End-tidal iso£urane was measured by calibrated gas analyzers and maintained at 1.57%, or 1.2 times minimum alveolar concentration. Measurements in laterally recumbent horses were made at least 20 minutes following constant end-tidal iso£urane conditions. Measurements in awake horses were made 1 hour following standing recovery from anesthesia. The following data were obtained from anesthetized and awake horses, respectively (mm Hg; mean
SD): MAP ¼ 71
6 and133
17, CVP ¼ 9
3 and 4
14, ICP ¼ 24
5 and 2
4, CPP ¼ 48
4 and 102
26. Paired t-tests showed signi¢cant di¡erences between anesthetized and awake horses for MAP ( p < 0.0005), ICP ( p < 0.00005), and CPP ( p < 0.005), but not for CVP. In both groups, PaCO2 ranged between 34 and 43 mm Hg, and PaO2 was always greater than 80 mm Hg. Results from this study indicate that healthy horses anesthetized with ISO in lateral recumbency have signi¢cantly increased ICPand decreased CPP compared to unmedicated, standing horses. Thus, in the absence of adequate cerebrovascular autoregulation, it is possible that this species may be especially susceptible to periods of cerebral ischemia during anesthesia. Anesthesia for laryngoplasty with or without sacculectomy in 85 draft horses: comparison with 322 Thoroughbreds KN Olson University of Pennsylvania, Kennett Square, PA, USA

As a cerebral vasodilator, iso£urane (ISO) can interfere with normal cerebrovascular autoregulation and may exacerbate cerebral perfusion pressure (CPP) changes in horses brought about by drugs that decrease mean arterial pressure (MAP) and by body positions that alter the hydrostatic

The few references in the literature concerning chemical restraint and anesthesia in the draft breeds suggest their response to drugs may be more profound than the light breeds, and their large size may make them prone to postoperative complications. The anesthesia records of 85 draft horses (D) and 322 Thoroughbreds (T) anesthetized for laryngoplasty, with or without sacculectomy, from 1991 through 1998 were compared. All horses received xylazine or detomidine as the primary sedative. Some horses received multiple doses of xylazine. In addition, some horses were given acepromazine and/or butorphanol. All horses received guaifenesin, except two draft horses and four Thoroughbreds. All horses were

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105

Intracranial and cerebral perfusion pressures in awake versus isoflurane-anesthetized horses RJ Brosnan, RA LeCouteur, A Imai, GD Kortz and EP Ste¡ey University of California-Davis, Davis, CA, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

induced with ketamine; most also received thiopental. Fifteen percent of Thoroughbreds and 48% of draft horses were anesthetized with iso£urane. The remainder received halothane. Data were compared using Student’s t-test with p < 0.05 considered signi¢cant. Signi¢cantly lower doses (mean
SEM) of xylazine were given to draft breeds compared to the Thoroughbreds, whether a single or multiple doses were required (single dose: D 0.41
0.02 mg kg1, T 0.48
0.01 mg kg1; multiple doses: D 0.56
0.03 mg kg1, T 0.69
0.02 mg kg1). This was also true for horses given acepromazine and/or butorphanol. Doses of butorphanol (D 0.009
0.0006 mg kg1,T 0.01
0.0005 mg kg1), guaifenesin (D 22
0.7 mg kg1,T 36
0.6 mg kg1), ketamine (D 2.2
0.05 mg kg1, T 2.5
0.02 mg kg1), and thiopental (D 0.6
0.03 mg kg1, T 0.7
0.02 mg kg1) were signi¢cantly lower in the draft breeds. When the drug doses were converted to metabolic size (kg3/4), only the guaifenesin dose remained signi¢cantly lower (D 122
4 mg kg3/4 T 170
3 mg kg3/ 4 ). Anesthesia time was signi¢cantly shorter in the draft horses (D 86
1 minutes, T 119
2 minutes). Time from the end of anesthesia to standing was not di¡erent between groups. Five (5.8%) draft horses su¡ered postoperative complications, including two myopathies, two neuropathies and one prolonged recovery. Four (1.2%) Thoroughbreds had complications, including three myopathies and one neuropathy. The draft horses require lower doses of many sedatives and anesthetics compared to the Thoroughbreds (on a mg kg1 basis), but when doses are adjusted for metabolic size, this holds true only for guaifenesin. The incidence of postoperative complications is greater in draft horses.

The pre-drug values within a treatment group were not signi¢cantly di¡erent. The combined pre-drug values were heart rate (HR) ¼ 32
1 beats minute1, respiratory frequency ( f ) ¼ 11
1 breaths minute1, PaO2 ¼ 66.6
1.5 mm Hg (Mexico City is 2240 m above sea level; yearly average PBAR ¼ 582 mm Hg), PaCO2 ¼ 36.2
0.7 mm Hg and pHa ¼ 7.42
0.01. During 20 minutes of anesthesia HR, f and PaCO2 were not signi¢cantly di¡erent from predrug values.The PaO2 decreased byan average of12 mm Hg during anesthesia but returned to the pre-drug values within 15 minutes after the horses stood. The quality of anesthetic induction varied and brief paddling limb movements occurred occasionally after recumbency regardless BUTOR dose. Recovery from anesthesia was subjectively graded good to excellent. The BUTOR dose did not signi¢cantly in£uence recumbency time (33
2 minutes for all studies). The BUTOR dose did not markedly in£uence study results. However, some physiological e¡ects likely were confounded by the notably low PaO2 that was in£uenced by geographic location of study.The magnitude of PaO2 implies a narrow margin for error for hypoxemia-related complications attending anesthetic management of horses breathing air at high altitude without supplemental O2.

Evaluation of pulse oximeters in horses NS Matthews, SM Harts¢eld and CP Boutros Texas A & M University, College Station, TX, USA

The purpose of this study was to evaluate selected physiological and behavioral responses to xylazine (XYL)^butorphanol (BUTOR) supplemented propofol (PROP) anesthesia in horses and the in£uence of BUTOR dose on outcome. Eight horses [13
2 (mean
SE) year], weighing 524
9 kg were anesthetized three times with at least 3 weeks between each anesthesia. After collecting pre-drug data, horses were always medicated with 0.5 mg kg1 XYL IV. Five minutes later, BUTOR was administered IV according to a randomized order of three doses: 0.025, 0.05, and 0.075 mg kg1; all horses received the complete dose set. Five minutes after BUTOR, anesthesia was induced with PROP, 2 mg kg1 IV. The resultant data were grouped by treatment and parameter and analyzed by RM ANOVA; p < 0.05 considered signi¢cant.

Evaluation of pulse oximeters over a wide range of hemoglobin saturation is very limited in horses.This study evaluated ¢ve pulse oximeter models for accuracy in horses. Five horses (mean age, 9.8 year; mean weight, 493 kg) were anesthetized and instrumented with arterial catheters. Anesthesia was induced with xylazine (1.1 mg kg1 IV) followed by diazepam (0.03 mg kg1 IV) and ketamine (2.2 mg kg1 IV) and maintained with iso£urane. Horses were mechanically ventilated and mean blood pressure was maintained at >60 mm Hg. The PaO2 was measured at beginning and end of anesthesia. The Nellcor Puritan Bennett NPB-395, NPB-190, NPB-290, NPB-40, and SurgiVet V3304 were attached to veterinary probes placed on ¢ve sites (5  5 Latin square design). Sites included the tongue, lip, nostril, ear and prepuce or vulva. Ten readings (SpO2) were taken at each of three hemoglobin saturation plateaus (98, 85 and 72% achieved by mixing nitrogen into the anesthesia circuit) in each horse from each probe site. SaO2 was measured by a co-oximeter (set in horse mode and calibrated with manufacturer’s QC solutions), using arterial samples drawn concurrently. Accuracy of saturation measurements was calculated as the root mean squared di¡erence (RMSD)(a product of bias and precision; usual human RMSD ¼ 2.5^3.5%). RMSD (%) were 3.1, 3.0, 4.7, 3.3, and 2.1 for the NPB-395, NPB-190, NPB-290, NPB-40, and V3304, respectively. Pulse oximeters failed to obtain readings on numerous occasions:

106

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

Evaluation of xylazine, butorphanol and propofol for short-term intravenous anesthesia in horses AA Garcia Lascurain, H Sumano Lopez, EP Ste¡ey, P Santillan Doherty and E Nun‹ez Hernandez Universidad Nacional Autonoma de Mexico, Mexico City, Mexico

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

10, 21,0,17, and 60% from the NPB-395, NPB-190, NPB-290, NPB-40 and V3304, respectively. Failure to obtain readings may have been related to vasoconstriction caused by induction drugs (many failures occurred within 30 minutes after induction), dark pigmentation and probe placement sites. Accuracy of the monitors varied as did ability to obtain readings. Generally, all of the monitors evaluated, produced fairly accurate readings when readings were available.

Effect of xylazine and detomidine on urine production in horses deprived of food and water E Nun‹ez Hernandez, EP Ste¡ey, L Ocampo Camberos, A Rodriguez Monterde and AA Garcia Lascurain Universidad Nacional Autonoma de Mexico, Mexico City, Mexico Alpha-2 agonists cause transient dose-related increase in urine £ow in normal horses. Although important clinically, e¡ects of these drugs in dehydrated animals are not known. The purpose of this study was to describe the in£uence of xylazine (XYL) and detomidine (DET) on urine £ow in mares deprived of food and water for 24 hours. Six clinically normal mares [12.5
3.3 (mean
SE) years] weighing 471
23 kg were each studied four times; each study was separated by at least 7 days. The morning following fasting, the urinary bladder was catheterized (Foley) and emptied. Urine was then collected for 2 hours and a composite urine sample along with a sample of jugular venous blood provided baseline values. Shortly after emptying the bladder, saline, 0.5 or 1.0 mg kg1 XYL or 0.03 mg kg1 DET was injected IV (treatment randomly assigned) and urine and blood samples obtained over the next 2 hours. Data were analyzed by RM ANOVA followed by Dunnett’s test for pairwise comparisons p < 0.05; indicated by (S). Pretreatment urine£owwas 0.30
0.03 mL kg1 hour1, urine speci¢c gravity (SG) was 1.032
0.001, packed cell volume (PCV) was 37.8
1.0%, and total plasma solids (TP) was 6.85
0.12 g dL1; values for four treatment periods within a grouping did not di¡er. At 1 hour post-treatment, urine £ow (mL kg1 hour1) was 0.31
0.04, 1.09
0.48, 2.33
0.89(S), and 2.14
0.58 (S) for saline, 0.5 XYL, 1.0 XYL and DET, respectively. By 2 hours, urine £ow was at or returning to baseline with all treatments except DET where a further increase was noted (8.28
0.92(S)). A time related decrease in urine speci¢c gravity (e.g. 1.010^1.021 at 1 hour post-treatment) was associated with the increase in urine £ow but PCVand TP did not change signi¢cantly with time or treatment. These data indicate that XYL and DET cause an important time-related, transient increase in urine £ow despite food and water deprivation. Consequently, severity of dehydration accompanying inadequate water intake during periods of normal or excessive £uid losses may be exacerbated by concurrent administration of alpha-2 agonists in horses. Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

Urinary effects of xylazine and general anesthesia in horses ZE Watson, EP Ste¡ey, LM Van Hoogmoed and JR Snyder University of California-Davis, Davis, CA, USA The purpose of this study was to characterize urine £owand biochemical parameters in horses given xylazine (XYL) and anesthetized with ketamine and iso£urane. Nine mares [9
2 (mean
SE) years; 492
17 kg] were studied. They were anesthetized for 2 hours in support of a campus-approved, laboratory-based orthopedic study. The day prior to anesthesia, a venous blood sample was obtained for biochemical analysis from each unmedicated mare. The urinary bladder was catheterized and emptied, and urine collected over the next three hours to quantitate the predrug values. The next day the mares were similarly catheterized. After obtaining urine and venous blood samples, XYL (1.1 mg kg1 IV) was administered. Anesthesia was induced 5 minutes later with ketamine (2.2 mg kg1 IV) and diazepam (0.04 mg kg1 IV) and maintained with iso£urane in O2. Lactated Ringer’s solution (10 mL kg1 hour1) was administered IV and dobutamine infused as required to maintain mean arterial blood pressure between 70 and 80 mm Hg. Mechanical ventilation maintained PaCO2 between 48 and 52 mm Hg and PaO2 > 200 mm Hg. Blood and urine were collected at 30, 60, and 120 minutes during anesthesia, and at 1 hour postanesthesia. Data were analyzed with RM ANOVA; with p < 0.05. Control urine £ow was 0.92
0.17 mL kg1 hour1. Urine £ow was signi¢cantly increased at 30 and 60 minutes following XYL (2.14
0.59 and2.86
0.97 mL kg1 hour1, respectively), but returned to control levels by the end of anesthesia. The most notable biochemical change was an initial signi¢cant increase in serum glucose from 121
4 to 167
8 mg dL1 at 30 minutes post-XYL that was not accompanied by a signi¢cant glucosuria (control value 4
1 mg dL1). We conclude that urine output increases in anesthetized horses following XYL, but this increase is not as a result of glucosuria. Cardiopulmonary, hematological, serum chemistry and peritoneal fluid alterations associated with abdominal insufflation with carbon dioxide during standing laparoscopy in healthy horses sedated with detomidine and butorphanol F Latimer, S Eades, G Pettifer, J Tetens, G Hosgood and R Moore Louisiana State University, Baton Rouge, LA, USA Changes in cardiopulmonary function, hematology, serum chemistry and peritoneal £uid were examined in six healthy, pharmacologically restrained, mature horses during and after abdominal insu¥ation with CO 2 (15 mm Hg) during standing laparoscopy. Each horse underwent standing left £ank exploratory laparoscopy (LFL) and a sham 107

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

procedure (SLFL) (cannula placement without insu¥ation) in a randomized cross-over design with at least 4 weeks between procedures. Heart rate (HR), respiratory rate (RR), cardiac output (thermodilution) (CO), right atrial pressure (RAP), systemic arterial blood pressures (ABP), pulmonary arterial pressure (PAP) and arterial blood gases (ABG) were measured. Cardiac index (CI), systemic vascular resistance (SVR) and pulmonary vascular resistance (PVR) were derived from measured parameters. Baseline measurements were the average of measurements taken every 15 minutes for 60 minutes. Following baseline measurements, samples for complete blood count (CBC), serum chemistry analysis (SC) and peritoneal £uid (PF) analysis were obtained. The horses were then sedated with detomidine (0.02 mg kg1 IV) followed in 5 minutes by butorphanol (0.02 mg kg1 IV) and the £ank was prepared for laparoscopy. Cardiopulmonary data and blood gas samples were obtained 5 minutes postdetomidine sedation, 10 minutes after butorphanol administration and at 0, 5,15, 30, 45, and 60 minutes after abdominal insu¥ation with CO2 (15 mm Hg) (LFL) or instrumentation without insu¥ation (SLFL). CBC, SC, and PF analyses were repeated at the conclusion of insu¥ation and desu¥ation and 24 hours after the conclusion of each procedure. Signi¢cant decreases in HR, CO, and CI and signi¢cant increases in MRAP, SVR and PVR occurred immediately after detomidine administration. There were no clinically signi¢cant e¡ects of abdominal insu¥ation with CO2 on any measure of cardiopulmonary function, including blood gases. There was a signi¢cant increase in peritoneal £uid total nucleated cell count 24 hours following LFL. Abdominal insu¥ation with CO 2 (15 mm Hg) for 1 hour during the standing laparoscopy does not cause signi¢cant alterations in cardiopulmonary function, but does cause a mild in£ammatory response within the peritoneal cavity.

(56), orthopedic (44), and reproductive (35) procedures. Majority of maintenance anesthesia was iso£urane in oxygen, 21 animals received halothane, and six received des£urane. Relaxation was evaluated using train-of-four or 50 Hz tetanic stimulus to the super¢cial peroneal nerve or the facial nerve, and subsequent muscle response was observed. Atracurium was given by single IV bolus dose, by infusion, or a combination of techniques. Initial bolus of atracurium was 0.1^0.2 mg kg1. Repeat bolus doses and dose interval varied. Mean infusion durationwas77 minutes Infusion rate varied, but was 0.2 mg kg1 hour1 for orthopedic and ophthalmologic procedures. Edrophonium (0.5 mg kg1) given IV over 1 minute, was used to antagonize atracurium in173 cases. No cardiovascular e¡ects were noted. Recovery to standing was reported as smooth for 158 animals, fair for 33, and rough for 24. A total of 40 recoveries did not have a detailed description. Eight horses were recovered in a support sling. Nine horses were euthanized prior to recovery. In conclusion, atracurium is a useful, safe adjunct to large animal anesthesia, especially when the surgical conditions speci¢cally require relaxation.

Airlifting horses by helicopter: sedation requirements G Pettifer, J Smith, R McConnico, F Latimer and J Hubert Louisiana State University, Baton Rouge, LA, USA

Predictable duration and unique method of elimination make atracurium a suitable muscle relaxant for large animals. This abstract presents experience with clinical use of atracurium in large animal anesthesia from1989 to 2001. Anesthesia records for large animals were reviewed for use of atracurium. Species of animal, nature of the surgical procedure, maintenance anesthetic, method of atracurium administration, antagonism of atracurium, and recovery experience were noted. Of the 264 animals that received atracurium, 248 were horses. Other species included cattle, pigs, llama, and one lion. Surgical procedures most likely to be associated with atracurium use were laparotomy (63) and ophthalmologic

Horses airlifted by helicopter must be cooperative, able to support their own weight plus the weight of the rescue sling, nonreactive to helicopter approach, hovering, lift-o¡, and transport; and able to support their own weight without signi¢cant ataxia during delivery to safe ground. The £ooding that occurs in Louisiana has given us the opportunity to be involved in airlift rescue of eight horses stranded by high water. In our experience, the e¡ective titration of sedatives is best accomplished through an IV catheter placed in one of the jugular veins rather than by repeated IV injections. Prior to the catheter placement, we sedate the horses with either xylazine (0.4^0.5 mg kg1 IV) or detomidine (8^ 10 mg kg1 IV). The process of airlifting can be divided into four phases: (1) attachment of lift sling; (2) helicopter approach and hover during attachment of the sling to the aircraft; (3) lift and transport; and (4) delivery to safe zone. The IV administration of an additional 0.4^0.5 mg kg1 of xylazine immediately prior to placing the horse in the lift sling produces an appropriate level of sedation without excessive ataxia.With the sling in place and the horse blindfolded, the helicopter is called. As the helicopter approaches, another 0.4^0.5 mg kg1 xylazine administered. The IV is generally su⁄cient to prevent reaction to the noise and wind associated with the hovering of the helicopter. After the lift sling is connected to the helicopter, a ¢nal dose of xylazine (0.25 mg kg1 IV) has proven e¡ective in reducing reaction to lift and transport.This sedation protocol has proven e¡ective for airlifts of approximately 5^10-minutes duration.

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Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

Clinical use of atracurium in large animal species SV Hildebrand and JA Bolich University of California-Davis, Davis, CA, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

Thus sedated, horses are able to support their weight without excessive ataxia when delivered to their destination. Xylazine appears to be more e¡ective than detomidine because of its shorter latency of onset and duration of action.

Cutaneous analgesic, respiratory and cardiovascular effects, and beta-endorphin concentration in CSF and plasma of horses after electro-acupuncture RT Skarda, GA Tejwani and WW Muir The Ohio State University, Columbus, OH, USA

Epidural administration of tiletamine–zolazepam in horses CC Natalini, SDL Alves and EP Robinson Universidade Federal de Santa Maria, Santa Maria, RS Brazil; and University of Minnesota, St. Paul, MN, USA

We tested the hypothesis that electro-acupuncture (EAP) can activate the horse’s pain modulation system (pituitary or brain stem) to release beta-endorphin in spinal £uid and plasma which provides pain relief in horses. Eight adult healthy mares (510
40 kg) were used in a randomized-crossover design study of 2 hours of EAP (test) and needle placement without electrical stimulation (sham-controls) with at least 3 weeks between experiments. Catheters were aseptically placed in the lumbar subarachnoid space, left carotid artery, and jugular vein of mares, using local anesthesia (2% lidocaine). Cerebrospinal £uid (3 mL) and venous blood (10 mL) were collected for radioimmunoassay of beta-endorphin (Tejwani et al., Life Sci. 1985). Arterial blood pressure, blood pH, PO2, PCO 2, PCV, and TS concentrations were determined. Hwato acupuncture needles (28 gauge, 12.5 cm) were inserted at BL 18, 23, 25, and 28 on both sides of the spinal column of mares and were stimulated by an EAP stimulator (ITO IC 4107) using 15 and 30 Hz alternating frequencies, 4 V, 1 mA, and 0.1 ms biphasic square pulses in the test mares. Nociceptive skin pain threshold was measured by skin twitch re£ex latency (STRL) and avoidance to radiant heat (48.5 8C cut-o¡) at the paralumbar fossa. Numerical scores of STRL, sedation, ataxia, respiratory and cardiovascular function, and beta-endorphin concentration in CSF and venous plasma were determined before (time 0), and 30, 60, 90, and 120 minutes after beginning and cessation of EAP and sham-controls. Two-way ANOVA with repeated measures and Dunnett’s post test were used. EAP signi¢cantly ( p < 0.001) increased STRL [12.4
2.1 seconds (mean
SD) at baseline; 17.3
2.2 seconds at 2 hours after EAP] and concentration of CSF betaendorphin [17.5
3.9 pg mL1 (mean
SD) at baseline; 26.1
6.2 pg mL1 at 2 hours after EAP], and minimally a¡ected behavior and respiratory and cardiovascular systems of adult mares during and after the 2 hour-testing period.

Epidural administration of phencyclidine derivatives has been reported in horses. Ketamine has been shown to produce dose-dependent analgesia over the perineal region with minimum ataxia and cardiovascular depressant e¡ects. Tiletamine is a similar drug that has not been studied epidurally in the equine species. This study was designed to evaluate the cardiovascular, behavioral and analgesic e¡ects of tiletamine and zolazepam (100 mg mL1 total drug) combination epidurally administered to horses. Six healthy adult horses (400
98 kg) were studied. A 19-SWG catheter was placed through the ¢rst intercoccygeal epidural space 48 hours before tiletamine^zolazepam administration. Epidural tiletamine^zolazepam 0.5 or 1.0 mg kg1 were administered to each horse through the epidural catheter with a 7-day interval. Heart rate, respiratory rate, noninvasive oscillometric arterial blood pressure, arterial blood gases, sedation, ataxia and analgesia were evaluated before and every 15 minutes after tiletamine^ zolazepam administration for 240 minutes. Ataxia was classi¢ed as mild, moderate or severe. The horses were walked out of the stocks and observed. Analgesia was evaluated using mechanical stimulation of the skin over the perineal region by pinching with forceps. Responses were graded as 0 (strong conscious response, such as kicking, no analgesic e¡ect); 1 (mild conscious response, such as turning the head towards the site of stimulation); 2 (absence of conscious response to noxious stimulation). Comparison between groups was done using two-way repeated measures ANOVA and Bonferroni’s test for parametric data and ANOVA on ranks for nonparametric data. The results showed no signi¢cant changes in cardiovascular and respiratory function over time and no di¡erences between groups. In each group 75% of the horses were scored as grade 1analgesia and 25% were scored as grade 0 analgesia. Muscle fasciculation and central nervous system excitation were observed in one horse (vigorous head and neck movements and dilated nares). Moderate to severe ataxia was observed in all horses in both groups. Sedation was not observed. The authors concluded that 0.5 and 1.0 mg kg1 epidural tiletamine^zolazepam in horses produces either none or mild-to-moderate analgesia, moderate-to-severe ataxia, and minimal cardiovascular and respiratory depression. Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

LLAMAS Pharmacokinetics and pharmacodynamics of butorphanol in llamas following intravenous and intramuscular administration GL Carroll, DM Boothe, SM Harts¢eld, EA Martinez, AC Spann and A Hernandez Texas A & M University, College Station, TX, USA Our purposes were to evaluate the disposition of butorphanol (BUT) in llamas after intravenous (IV) and intramuscular (IM) administration, to evaluate the e¡ect of BUT on 109

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

EXOTIC AND LABORATORY ANIMALS

certain physiologic variables, and to evaluate BUT’s analgesic e⁄cacy after IM administration. Six healthy neutered male llamas (4.5
1.6 years) weighing 102.9
16.4 kg were given BUT (0.1 mg kg1, IV or IM) using a nonrandomized crossover design; each llama received each treatment at a 1-month interval. The dose chosen for evaluation was that which is currently used to treat pain in llamas. Blood samples were withdrawn from the venous catheter, after £ushing with heparinized saline and collecting a waste sample. A volume of 6 mL of blood were collected and placed in heparinized tubes at 0, 2,5,10,15, and 30 minutes and1, 2,3,4,6,8,16, and 24 hours for the IV study and at 0,15, 30, and 45 minutes and 1,1.5, 2, 3, 4, 6, 8, 16, and 24 hours for the IM study. Drug in plasma was detected by high performance liquid chromatography and subjected to standard pharmacokinetic analysis using linear regression. Two months later, BUT was administered IM; physiologic variables (heart rate, respiratory rate, rectal temperature, indirect blood pressure) and analgesia were assessed at 15-minute intervals for 2 hours. Analgesia was assessed using a modi¢ed hoof-tester ¢tted with an electronic force transducer to measure applied isometric force to the withers, mid-neck region, and metacarpus. Elimination between the two routes was compared using an unpaired two-tailed t-test; continuous variables after IM BUT were subjected to repeated measures ANOVA; the p-values < 0.05 were considered statistically signi¢cant. The C0 after IV BUT was 94.8
53.1 ng mL1; Cmax after IM BUT was 34.3
11.6 ng mL1. TheVss after IV BUT was 0.822
0.329 L kg1 and systemic clearance was 0.050
0.014 L kg1 minute1. The slope of the elimination phase and the elimination half-life were signi¢cantly shorter after IV (15.9
9.1 minutes) versus IM (66.8
13.5 minutes) BUT. Bioavailability was 110
49%. Heart rate decreased (30^105 minutes) and rectal temperature increased (30^60 minutes). Somatic analgesia increased at 30 minutes (plasma BUT ¼ 23.8 ng mL1) in the withers compression model and did not return to baseline; in the mid-neck compression model, somatic analgesia increased at 45 minutes (21.0 ng mL1) and returned to baseline by 120 minutes (9.2 ng mL1). Two llamas weretransiently sedated and two were transiently excited after IM BUT. The relationship among plasma BUT concentration, time, and analgesia di¡ered with the area of compression. Clinical trials in llamas could better de¢ne the plasma BUT concentrations associated with somatic and visceral analgesia. The longer half-life of IM BUT is more likely to be clinically convenient compared to IV BUT.

Active warming of pet birds under general anesthesia is necessary to prevent hypothermia and its associated, potentially life-threatening complications. The ability of a forcedair warming system to provide thermal support was compared to a circulating-water blanket and an infra-red heat emitter during iso£urane anesthesia of Hispaniolan Amazon parrots (Amazona ventralis). Ten Hispaniolan Amazon parrots were anesthetized once weekly for one of ¢ve 60-minute trials using di¡erent heating devices. Trial (1) no thermal support;Trial (2) surgical drape only;Trial (3) circulating water blanket and surgical drape; Trial (4) ceramic infra-red heat emitter and surgical drape; Trial (5) forced-air warmer and surgical drape. Each bird acted as its own control. The birds were mask-induced with iso£urane in oxygen, intubated and maintained on iso£urane with spontaneous ventilation. Subjects were positioned in dorsal recumbency on a cotton towel on a stainless steel surgical table. A 5.5 cm  5.5 cm area on the ventral abdomen was plucked and surgical prepared to simulate a surgical situation. A lead II ECG was continuously monitored to determine heart rate and rhythm. A temperature probe was inserted into the thoracic esophagus and readings were taken every 5 minutes. Digital thermometers were placed around the bird to monitor the ambient temperature immediately adjacent to the bird and the surrounding area. The readings were taken every 15 minutes. Body temperature and surgical area temperature were considered to be continuous and were found to follow a normal distribution using the Shapiro Wilk Statistics, where di¡erences were evident, selected multiple comparisons were made within treatments to baseline temperature and between treatments. Multiple comparisons were made using adjusted least squares means, controlling the experimental type 1 error and 0.05 PROC MIXED was used for the analysis (SAS V8, SAS Institute, Cary, NC, USA). None of the warming devices prevented a signi¢cant decrease in esophageal temperature over the 60 minutes. The average temperature losses for the control trial,

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Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

Comparison of traditional thermal support with the forced-air warmer system in Hispaniolan Amazon parrots (Amazona ventralis) MS Rembert, JA Smith, G Pettifer, G Hosgood, SL Marks and TN Tully Louisiana State University, Baton Rouge, LA, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

drape-only, and heat emitter, respectively, were 3.15, 2.45, and 2.55 8C. A signi¢cant decrease from 15 minutes was observed with all warming treatments, except the forcedair warmer, which prevented a signi¢cant decrease until 30 minutes. For the last 30 minutes, there was a signi¢cant decrease in esophageal temperature for the forced-air warmer treatment (from 39.135 to 39.125 8C). However, the esophageal temperature remained within the clinically acceptable normothermic range (all temperatures remained above 38.35 8C). The forced-air warmer system proved superior to traditional heating modalities in preventing heat loss during iso£urane anesthesia in Hispaniolan Amazon parrots.

Clinical and cardiopulmonary effects of propofol in the spotted bamboo shark (Chylloscyllium plagiosum) MA Mitchell,1 S Miller,2 JJ Heatley,1 T Wolf,1 F Lapuz,1 M Lafortune1 and JA Smith1, 1 Louisiana State University, Baton Rouge, LA and 2The Audubon Institute, Aquarium of theAmericas, New Orleans, LA, USA

signi¢cant di¡erence was determined at p < 0.05.Where differences were apparent, Rhyne and Steels method for comparison of related samples to a control (time 0) was used with an experimental-wise error of alpha ¼ 0.05. HR and RR did not change signi¢cantly over time. Respective values (mean
SD) for each data collection point were T (0), HR 37
10 beats minute1, RR 38
7 breaths minute1; T (5), HR 40
5, RR 44
15; T (10), HR 41
6; RR 41
15; T (15), HR 43
7, RR 38
13; T (30), HR 39
50, RR 39
14; T (45), HR 43
9, RR 37
14; T (60), HR 45
9, RR 38
11; T (75), HR 44
6, RR 38
12. The righting response was lost in all sharks within 5 minutes of propofol administration. A surgical plane of anesthesia was observed in all nine sharks. The righting response returned within 60 minutes in 4/9 sharks, 75 minutes in 2/9 sharks, and over 200 minutes in 3/9 sharks. All nine animals had uneventful recoveries. Propofol provided a safe alternative for immobilization of spotted bamboo sharks. However, manual restraint is required for IV administration. Further studies are necessary to determine an ideal dose and further evaluate propofol’s suitability as a general anesthetic for painful procedures.

Sharks are important exhibit animals at aquariums worldwide. Restraint is often necessary for physical examination, diagnostic evaluation, medical treatment and/or surgical procedures. Manual restraint is often used for simple procedures but may result in dangerous contact for the shark and the handler and, when used alone, is not su⁄cient for painful procedures. Limited reports describe the use of tricaine methane sulfonate, ketamine, or tiletamine^zolazepam in sharks. This study evaluates the clinical and cardiorespiratory e¡ects of propofol in spotted bamboo sharks (Chylloscyllium plagiosum). Nine, wild-caught, adult female spotted bamboo sharks weighing 1.75^2.5 kg were used in this study. The sharks were housed in individual portable plastic containers during data collection.Water chemistries and temperature were maintained within normal limits. An initial physical examination was performed using manual restraint. Propofol (2.5 mg kg1) was administered IV in the caudal tail vein over 30 seconds. The HR, RR, time to relaxation, resistance to handling, ¢n movement, loss of righting re£ex, and response to painful stimuli (¢n pinch) were evaluated and recorded at baseline and 5,10,15, 30, 45,60, and 75 minutes after propofol administration. Surgical anesthesia was thought to be achieved when a shark lost its righting re£ex, did not respond to painful stimuli, and no longer resisted handling. The HR and RR were evaluated over time using Friedman’s nonparametric analysis of repeated data. A

The principle cause of mortality and chronic morbidity after spinal cord injury (SCI) is respiratory failure. Hemisection of the second cervical spinal segment (C2HS) is frequently used as a model of SCI.The e¡ects of this injury on breathing pattern, however, have not been investigated. The pattern of breathing was examined at1-month (controls, n ¼ 12; C2HS, n ¼ 7) and 2-months postinjury (controls, n ¼ 11; C2HS, n ¼ 5). Measurements were made before and after bilateral vagotomy to determine the role of vagal a¡erents in the e¡ects of injury. Rats were anesthetized with urethane and allowed to breathe room air spontaneously. Direct arterial blood pressure was measured with a calibrated pressure transducer from a catheter in the femoral artery positioned via cut down. Arterial blood gases were measured using an i-STAT analyzer. Normothermia was maintained throughout the study. A linear pneumotachometer was calibrated by standard methods before and after each study day and attached to the end of a tracheotomy tube and 30 minutes was allowed before measurements were taken. The inspiratory and expiratory air£ow was measured before and after bilateral vagotomy. The

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

111

The effects of cervical spinal cord injury on the pattern of breathing in the rat F Golder, P Reier and D Bolser University of Florida, Gainesville, FL, USA

Proceedings of the American College of Veterinary Anesthesiologists 26th Annual Meeting, New Orleans, 2001

This investigation determined if increasing the degree of self-reliant learning (allowing students to set goals, identify resources, and implement learning strategies) in an Anesthetic Emergencies/Cardiopulmonary Resuscitation laboratory learning exercise would increase surface knowledge and con¢dence acquisition.

A total of 100 students enrolled in a surgical exercises course in the junior year of a DVM program participated. One month prior to the laboratory devoted to Anesthetic Emergencies/Cardiopulmonary Resuscitation, students in two of four laboratory sections were asked to submit a protocol designed for the laboratory that included cardiopulmonary arrest and resuscitation, jugular venous catheterization with central venous pressure measurement, and tracheotomy. The validity of the methodology included in the protocols was reviewed by the instructor prior to the laboratory. The remaining two laboratory sections were given a laboratory outline that included speci¢c directions for the target procedures, as well as instructor-selected references. A 10-question multiple choice question test designed to test surface knowledge was given at the beginning of the laboratory and the same 10 questions were embedded in the ¢nal examination for the surgical exercises course. At the beginning and end of the laboratory, each student was asked to rate his/her con¢dence level associated with administering CPR (visual analogue scale). Group means were compared using a Wilcoxon’s rank sum test (p < 0.05) and ANOVA for repeated measures was used to test for di¡erences in con¢dence levels and test scores over time ( p < 0.05). There was no signi¢cant di¡erence between the mean (
SEM) entry quiz test score for the Self-Reliant Learning (SRL) group (4.1
0.26) and that for the Instructor-Directed Learning (IDL) group (4.6
0.24). The exit quiz scores for the IDL group (5.2
0.224) were signi¢cantly higher than those for the SRL group (3.9
0.21) although the di¡erence between entry and exit quiz scores for the two groups was not signi¢cant. There was no signi¢cant di¡erence between entry or exit con¢dence levels for the two groups. Students in the SRL group reported investing a signi¢cantly greater number of hours in preparation for the laboratory than students in the IDL group (4.8
0.4 versus 3.0
0.23). There was no signi¢cant di¡erence between how the two groups rated the quality of the learning experience (IDL ¼ 7.3
0.33; SRL ¼ 7.2
0.33). In comparison to IDL, an isolated SRL experience does not signi¢cantly increase surface knowledge acquisition or retention, con¢dence level associated with target skills, or estimation of the quality of learning experience.

112

Veterinary Anaesthesia and Analgesia, 2002, 29, 97^112

air£ow signal from the pneumotachometer was integrated to give expired tidal volume (VT). Respiratory rate (RR) was measured from the air£ow signal. All data are presented as mean
SD. Means for expired tidal volume were compared between animal groups using the Kruskal^Wallis ANOVA and the Mann^Whitney U-test. All other means were compared using a two factor ANOVA. Multiple comparisons were made using t-tests with Bonferroni’s correction. No di¡erences in blood pressure or blood gases were detected between groups. Injured rats maintained the same minute ventilation as controls by utilizing higher RR (minute1) (1-month; controls 127
19, injured 177
31: 2months; controls 126
20, injured 168
23) and lower VT (mL kg1) (1-month; controls 8.6
0.8, injured 6.9
0.2: 2months; controls 8.3
0.7, injured 5.9
0.2). In addition, the frequency of augmented breaths was greater in injured rats at 2-months postinjury compared to the 2-month control group (minute1) (controls 0.12
16, injured 0.45
0.20). After bilateral vagotomy,VT increased and RR decreased in all groups and the pattern of breathing was no longer di¡erent between injured and control animals. In conclusion, the C2HS alters the pattern of breathing at 1- and 2-months postinjury and increases the frequency of augmented breaths at 2-months postinjury. These results also suggest that the pattern of breathing may be determined by the vagal mechanisms rather than impaired respiratory motor drive.

ANESTHESIA EDUCATION Does increasing self-reliant learning in a cardiopulmonary resuscitation laboratory improve knowledge and confidence acquisition? G Pettifer Louisiana State University, Baton Rouge, LA, USA