Effect of anesthetic induction with propofol, alfaxalone or ketamine on intraocular pressure in cats: a randomized masked clinical investigation.

OBJECTIVE: To compare the effect of propofol, alfaxalone and ketamine on intraocular pressure (IOP) in cats. STUDY DESIGN: Prospective, masked, randomized clinical trial. ANIMALS: A total of 43 ophthalmologically normal cats scheduled to undergo general anesthesia for various procedures. METHODS: Following baseline IOP measurements using applanation tonometry, anesthesia was induced with propofol (n = 15), alfaxalone (n = 14) or ketamine (n = 14) administered intravenously to effect. Then, midazolam (0.3 mg kg-1) was administered intravenously and endotracheal intubation was performed without application of topical anesthesia. The IOP was measured following each intervention. Data was analyzed using one-way anova and repeated-measures mixed design with post hoc analysis. A p-value <0.05 was considered significant. RESULTS: Mean ± standard error IOP at baseline was not different among groups (propofol, 18 ± 0.6; alfaxalone, 18 ± 0.7; ketamine, 17 ± 0.5 mmHg). Following induction of anesthesia, IOP increased significantly compared with baseline in the propofol (20 ± 0.7 mmHg), but not in the alfaxalone (19 ± 0.8 mmHg) or ketamine (16 ± 0.7 mmHg) groups. Midazolam administration resulted in significant decrease from the previous measurement in the alfaxalone group (16 ± 0.7 mmHg), but not in the propofol group (19 ± 0.7 mmHg) or the ketamine (16 ± 0.8 mmHg) group. A further decrease was measured after intubation in the alfaxalone group (15 ± 0.9 mmHg). CONCLUSIONS AND CLINICAL RELEVANCE: Propofol should be used with caution in cats predisposed to perforation or glaucoma, as any increase in IOP should be avoided.

Effect of intravenous butorphanol infusion on the minimum alveolar concentration of isoflurane in cats.

OBJECTIVE: To determine the effect of butorphanol, administered by intravenous (IV) infusion, on the minimum alveolar concentration of isoflurane (MACISO) in cats and to examine the dosage dependence of this effect. STUDY DESIGN: Randomized, placebo-controlled, crossover experimental study. ANIMALS: A group of six healthy adult male neutered cats. METHODS: Cats were anesthetized with isoflurane in oxygen. A venous catheter was placed for fluid and drug administration, and an arterial catheter was placed for measurement of arterial pressure and blood sampling. Four treatments were administered at random with at least 2 week interval between treatments: saline (control), butorphanol low dosage (treatment LD; 0.25 mg kg-1 IV bolus followed by 85 µg kg-1 minute-1 for 20 minutes, then 43 µg kg-1 minute-1 for 40 minutes, then 19 µg kg-1 minute-1), medium dosage (treatment MD, double the dosages in LD) and high dosage (treatment HD, quadruple the dosages in LD). MACISO was determined in duplicate using the bracketing technique and tail clamping. Pulse rate, arterial pressure, hemoglobin oxygen saturation, end-tidal partial pressure of carbon dioxide and arterial blood gas and pH were measured. RESULTS: Butorphanol reduced MACISO in a dosage-dependent manner, by 23 ± 8%, 37 ± 12% and 68 ± 10% (mean ± standard deviation) in treatments LD, MD and HD, respectively. The main cardiopulmonary effect observed was a decrease in pulse rate, significant in treatment HD compared with control. CONCLUSIONS AND CLINICAL RELEVANCE: Butorphanol caused a dosage-dependent MACISO reduction in cats. IV infusion of butorphanol may be of interest for partial IV anesthesia in cats.

Pharmacokinetics of butorphanol in male neutered cats anesthetized with isoflurane.

This study characterized the pharmacokinetics of butorphanol in cats anesthetized with isoflurane. Six young healthy male neutered cats were used. Cats were anesthetized with isoflurane in oxygen. Catheters were placed in a jugular vein for blood sampling and in a medial saphenous vein for butorphanol and lactated Ringer's solution administration. Butorphanol tartrate (1 mg/kg over 5 min) was administered intravenously. Blood samples were collected prior to butorphanol administration and at various times up to 365 min following administration. Plasma butorphanol concentration was measured using liquid chromatography/tandem mass spectrometry. Compartment models were fitted to the time-concentration data using nonlinear mixed effect modeling. A three-compartment model best fitted the data. Typical value (% interindividual variability) for the three volumes of distribution, the metabolic clearance, and the two distribution clearances were 230 (72), 1095 (not estimated), and 2596 (not estimated) ml/kg, and 18.4 (72), 169.6 (52), and 55.0 (43), respectively. Pharmacokinetic simulation suggested that a loading dose (µg/kg) calculated as 0.287 × target plasma concentration in ng/ml (CT ) followed by intravenous infusions (µg/kg/min) of 0.098 × CT for 20 min, 0.049 × CT for 40 min, and 0.022 × CT thereafter would rapidly achieve and maintain CT  ± 10% for up to 6.5 h.

Evaluation of alfaxalone and midazolam with or without flumazenil reversal in Egyptian fruit bats (Rousettus aegyptiacus).

OBJECTIVES: To evaluate alfaxalone-midazolam anesthesia in Egyptian fruit bats (Rousettus aegyptiacus) and the effect of flumazenil administration on recovery time and quality. STUDY DESIGN: Randomized, blinded, crossover and controlled, experimental trial. ANIMALS: A total of 10 male Egyptian fruit bats. METHODS: Bats were anesthetized with alfaxalone (15 mg kg-1) and midazolam (2 mg kg-1) administered subcutaneously. During anesthesia, vital signs, muscle tone and reflexes were monitored every 10 minutes. Flumazenil (0.3 mg kg-1) or saline at an equal volume was administered subcutaneously 60 minutes after anesthetic administration. Time to induction, time to first movement and recovery time (flying) were measured. Quality of induction, anesthesia and recovery were assessed on a 1-3 scale (1, poor; 2, good; 3, excellent). RESULTS: Time to induction was 4.2 ± 1.9 minutes (mean ± standard deviation), with median quality score of 2 (range, 1-3). Anesthesia quality score was 3 (1-3). During anesthesia, heart rate and respiratory frequency decreased significantly and penis relaxation, indicating muscle tone, increased significantly. Administration of flumazenil significantly reduced mean recovery time compared with saline (10 ± 5 versus 45 ± 17 minutes, respectively), and significantly improved the quality of recovery [2.5 (2-3) versus 1 (1-2), respectively]. CONCLUSIONS AND CLINICAL RELEVANCE: Alfaxalone-midazolam anesthesia resulted in good induction, muscle relaxation and sufficient anesthesia to perform routine diagnostic and therapeutic procedures for approximately 40 minutes. Reversal of midazolam with flumazenil is recommended, resulting in quicker and better recovery.

MEDETOMIDINE-KETAMINE-MIDAZOLAM VERSUS MEDETOMIDINE-KETAMINE-BUTORPHANOL FOR IMMOBILIZATION OF RED KANGAROOS (OSPHRANTER RUFUS).

The objectives of this clinical study were to compare the effectiveness and safety of medetomidine-ketamine-midazolam (MKM) versus medetomidine-ketamine-butorphanol (MKB) for immobilization of captive red kangaroos (Osphranter rufus). Twenty red kangaroos were randomly immobilized for routine treatments using intramuscular injection of MKM (0.065 ± 0.004, 2.2 ± 0.3, and 0.12 ± 0.04 mg/kg, respectively) or MKB (0.070 ± 0.015, 2.3 ± 0.5, and 0.23 ± 0.05 mg/kg, respectively) (n = 10/group). Induction, immobilization, and recovery times were recorded; vital signs monitored; and quality of induction, immobilization, and recovery scored using a single-blinded design. Oxygen was not supplemented. For reversal, atipamezole at five times the medetomidine dosage was administered intramuscularly (both groups), and flumazenil (0.020 ± 0.003 mg/kg; MKM) or naltrexone (0.23 ± 0.05 mg/kg; MKB) were administered intravenously. Induction time was significantly shorter in the MKB group versus the MKM group (7:26 ± 04:22 and 11:54 ± 04:50 minutes, respectively). Induction quality in both groups was rated "excellent" and immobilization quality was "excellent" in MKM and "very good" in MKB. Heart rate was significantly lower and hemoglobin oxygen saturation (SpO2) was significantly higher in the MKM versus the MKB group. However, SpO2 < 90% occurred with both protocols. Following antagonists administration, recovery time and quality were 17:40 ± 08:33 minutes and "very good" in the MKM group, and 14:28 ± 05:27 minutes and "excellent" in the MKB group, respectively. Both protocols provided smooth induction, good immobilization, and generally quick recovery. MKB is recommended for shorter induction time. Oxygen supplementation should be available with both protocols.

Retrobulbar vs peribulbar regional anesthesia techniques using bupivacaine in dogs.

OBJECTIVE: To compare the effectiveness of retrobulbar anesthesia (RBA) and peribulbar anesthesia (PBA) in dogs. ANIMAL STUDIED: Six adult mixed-breed dogs (18-24 kg). PROCEDURES: In a randomized, masked, crossover trial with a 10-day washout period, each dog was sedated with intravenously administered dexmedetomidine and administered 0.5% bupivacaine:iopamidol (4:1) as RBA (2 mL via a ventrolateral site) or PBA (5 mL divided equally between ventrolateral and dorsomedial sites). The contralateral eye acted as control. Injectate distribution was evaluated by computed tomography. Following intramuscularly administered atipamezole, corneal and periocular skin sensation, intraocular pressure (IOP), and ocular reflexes, and appearance were evaluated for 24 hours. Comparisons were performed with mixed-effects linear regression (IOP) or the exact Wilcoxon signed rank test (scores). Significance was set at P ≤ .05. RESULTS: Injectate distribution was intraconal in 2/6 RBA- and 4/6 PBA-injected eyes. Eyes undergoing PBA had significantly reduced lateral, ventral, and dorsal periocular skin sensation for 2-3 hours, and significantly reduced corneal sensitivity for 4 hours, relative to control eyes. Chemosis and exophthalmos occurred in 33%-40% of eyes undergoing RBA and 83%-100% eyes undergoing PBA but resolved within 14 hours. Anterior uveitis developed in 2/6 and 1/6 eyes of RBA and PBA, respectively, of them corneal ulcer developed in one eye of each treatment. Both resolved 1-3 days following medical treatment. CONCLUSIONS: Peribulbar injection produced notable anesthesia more reliably than did retrobulbar injection. Both techniques may produce adverse effects, although the uveitis/ulcer could have resulted from the contrast agent used.

A review of ophthalmic local and regional anesthesia in dogs and cats.

OBJECTIVE: Orbital and globe surgeries are commonly performed in companion animals and are considered to cause moderate to severe pain. Regional anesthesia techniques can provide complete sensory blockade, analgesia for painful procedures and improve surgical conditions. The purpose of this review is to summarize local and regional anesthesia techniques for ophthalmic surgery in dogs and cats with emphasis on veterinary publications in the past 12 years. DATABASES USED: Review of the literature was conducted using PubMed and Google Scholar. The search terms were 'ophthalmic regional anesthesia', 'retrobulbar anesthesia', 'peribulbar anesthesia', 'sub-Tenon's anesthesia', 'intracameral anesthesia', 'eye infiltration', 'dogs' and 'cats'. Further studies and reports were obtained from the reference lists of the retrieved papers. In addition, related veterinary anatomy, ophthalmology and regional anesthesia books were reviewed. CONCLUSIONS: Reported techniques include regional techniques such as retrobulbar anesthesia, peribulbar anesthesia and sub-Tenon's anesthesia, and local techniques such as eyelid and conjunctival infiltration, intracameral anesthesia, splash block and insertion of intraorbital absorbable gelatin sponge infused with local anesthetic. Administration guidelines, indications and contraindications, and complications of each technique are discussed. Regional anesthesia techniques were reported to be effective during ophthalmic surgeries and are recommended for use as part of the anesthetic regimen and pain management in animals. However, the veterinary literature is still lacking controlled clinical trials and adverse events reports; therefore, there is very little evidence for choosing one technique over another.

Immobilization of captive Persian fallow deer (Dama dama mesopotamica) using medetomidine-ketamine or medetomidine-midazolam.

OBJECTIVE: To establish and compare the effectiveness of two medetomidine-based immobilization protocols in Persian fallow deer (Dama dama mesopotamica). STUDY DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: A group of 31 captive Persian fallow deer. METHODS: Deer scheduled for translocation were immobilized with a combination of medetomidine (76 ± 11 µg kg-1) and ketamine (1.0 ± 0.2 mg kg-1) (MK; n = 15) or medetomidine (77 ± 11 µg kg-1) and midazolam (0.10 ± 0.01 mg kg-1) (MM; n = 16) administered intramuscularly. An observer unaware of group assignments recorded times to immobilization and recovery, monitored physiologic variables and scored the quality of induction, immobilization and recovery (scale 1-5: 1, poor; 5, excellent). Atipamezole was administered for reversal. Data analysis was performed using the t test, the Mann-Whitney U test, the chi-square test and the Fisher's exact test. Significance was set at p < 0.05. RESULTS: Data are presented as mean ± standard deviation or median (range). Time to induce immobilization was 9 ± 4 and 10 ± 4 minutes in the MK and MM groups, respectively. Immobilization quality score was 5 (1-5) following both combinations. Hemoglobin oxygen saturation (SpO2) was significantly lower in the MK (80 ± 8%) than in the MM group (87 ± 8%) although respiratory frequency did not differ between MK and MM (11 ± 5 and 10 ± 2 breaths minute-1, respectively). Recovery times were 13 ± 6 (MK) and 14 ± 7 minutes (MM) and did not differ between groups. No morbidities or mortalities were recorded during 1 month after immobilization. CONCLUSIONS AND CLINICAL RELEVANCE: The MK and MM combinations produced sufficient immobilization in captive Persian fallow deer for short nonpainful procedures. Based on the SpO2 values, the MM combination may be associated with less respiratory depression; nevertheless, both combinations may result in a decrease in SpO2.

Description of a regional anaesthesia technique for the dorsal cranium in the dog: a cadaveric study.

OBJECTIVE: To identify landmarks and to describe a technique for nerve blockade of the dorsal cranium in dogs. STUDY DESIGN: Anatomic cadaveric study. ANIMALS: A total of 39 dog cadavers, weighing 18.0 ± 9.7 kg (mean ± standard deviation). METHODS: The study was performed in three parts. In the initial part, cadavers were dissected to determine the location of the frontal, zygomaticotemporal, and major occipital nerves, and to identify prominent landmarks for their blockade. In the second part, one technique was developed to block each of the frontal and zygomaticotemporal nerves, and two techniques, rostral and caudal, were developed to block the major occipital nerve. Injection solution was 0.05% methylene blue in 0.5% bupivacaine. In the third part, cadavers were used to test the techniques developed in the second part with 0.04 mL kg-1 of the same injectate administered at each site (maximal volume 0.5 mL per site). The length of nerve stained was measured, with a length ≥6 mm considered successful. Confidence intervals were calculated using Fisher's exact test. RESULTS: Success rates (95% confidence interval) for the frontal, zygomaticotemporal, and rostral and caudal locations for the major occipital nerve were 94% (80-99%), 91% (76-98%), 74% (58-86%) and 77% (59-89%), respectively. With a combination of both locations, the success rate for the major occipital nerve was 100% (90-100%). CONCLUSION AND CLINICAL RELEVANCE: This study describes a simple regional anaesthesia technique using palpable anatomical landmarks that may provide analgesia for dogs undergoing craniotomy.

Plasma bupivacaine concentrations following orbital injections in cats.

OBJECTIVE: To determine plasma bupivacaine concentrations after retrobulbar or peribulbar injection of bupivacaine in cats. STUDY DESIGN: Randomized, crossover, experimental trial with a 2 week washout period. ANIMALS: Six adult healthy cats, aged 1-2 years, weighing 4.6 ± 0.7 kg. METHODS: Cats were sedated by intramuscular injection of dexmedetomidine (36-56 µg kg-1) and were administered a retrobulbar injection of bupivacaine (0.75 mL, 0.5%; 3.75 mg) and iopamidol (0.25 mL), or a peribulbar injection of bupivacaine (1.5 mL, 0.5%; 7.5 mg), iopamidol (0.5 mL) and 0.9% saline (1 mL) via a dorsomedial approach. Blood (2 mL) was collected before and at 5, 10, 15, 22, 30, 45, 60, 120, 240 and 480 minutes after bupivacaine injection. Atipamezole was administered approximately 30 minutes after bupivacaine injection. Plasma bupivacaine and 3-hydroxybupivacaine concentrations were determined using liquid chromatography-mass spectrometry. Bupivacaine maximum plasma concentration (Cmax) and time to Cmax (Tmax) were determined from the data. RESULTS: The bupivacaine median (range) Cmax and Tmax were 1.4 (0.9-2.5) µg mL-1 and 17 (4-60) minutes, and 1.7 (1.0-2.4) µg mL-1, and 28 (8-49) minutes, for retrobulbar and peribulbar injections, respectively. In both treatments the 3-hydroxybupivacaine peak concentration was 0.05-0.21 µg mL-1. CONCLUSIONS AND CLINICAL RELEVANCE: In healthy cats, at doses up to 2 mg kg-1, bupivacaine peak plasma concentrations were approximately half that reported to cause arrhythmias or convulsive electroencephalogram (EEG) activity in cats, and about one-sixth of that required to produce hypotension.

Intratesticular and incisional line infiltration with ropivacaine for castration in medetomidine-butorphanol-midazolam sedated dogs.

OBJECTIVE: To evaluate whether intratesticular and incisional ropivacaine infiltration produces sufficient intra- and postoperative analgesia for castrating dogs under sedation. STUDY DESIGN: Randomized, blinded, controlled clinical study. ANIMALS: Twenty-three healthy dogs weighing 5.8-35.6 kg admitted for castration. METHODS: Dogs were sedated with medetomidine (0.01 mg kg-1), butorphanol (0.2 mg kg-1) and midazolam (0.2 mg kg-1) intramuscularly, and were randomly assigned to group R, 0.2-0.4 mL kg-1 of ropivacaine 0.5%, or group S, an equivalent volume of saline injected intratesticularly and along the incision line. If persistent motion was observed during surgery, sedation was considered to be insufficient and general anaesthesia was induced. Carprofen 2.2 mg kg-1 was administered postoperatively. Pain was evaluated in all dogs before sedation and postoperatively following atipamezole administration at 1, 2, 4, 8 and 24 hours using an interactive visual analogue scale (IVAS; 0-100), the Glasgow composite pain scale-short form (CMPS-SF; 0-24), and a mechanical algometer. Methadone 0.3 mg kg-1 was administered intravenously to dogs if IVAS >30 or CMPS-SF >4. RESULTS: There was no significant difference between groups for the number of dogs administered general anaesthesia. The time from the beginning of surgery to induction of general anaesthesia was significantly shorter [median (range)] in group S [6 (3-25) minutes] than in group R [56 (36-76) minutes]. At 8 hours IVAS was significantly higher in group S (14 ± 10) than in group R (6 ± 4). CONCLUSIONS AND CLINICAL RELEVANCE: Intratesticular and incisional ropivacaine infiltration delayed the time to anaesthesia induction, and provided analgesia after castration performed under deep sedation in dogs. Intratesticular local anaesthesia can be an important part of the anaesthetic plan for castration.

A comparison of retrobulbar and two peribulbar regional anesthetic techniques in dog cadavers.

OBJECTIVE: To compare injectate distribution and likelihood of regional anesthesia to the orbit following retrobulbar (RB) or peribulbar (PB) injections in dog cadavers. STUDY DESIGN: Randomized, masked study. ANIMALS: Twenty-four dog cadavers (aged 5.5-17 years, 2.0-36.3 kg). METHODS: Orbits underwent one of three injection techniques with bupivacaine 0.5% and iohexol (1:1): ventrolateral RB injection (1-2 mL; 15 orbits), medial canthal PB injection (2-8 mL; PB-1; 16 orbits), or dorsomedial and ventrolateral PB injections (each 1-4 mL; PB-2; 16 orbits). The likelihood of successful regional anesthesia was estimated based on computed tomographic images scored for injectate volume of distribution at the base and within the extraocular muscle cone (EOMC), and injectate distribution around the optic nerve. Intraocular pressure (IOP) was measured before and after injections. Mixed-effects linear regression with post hoc Bonferroni contrast adjustments was performed. Significance was set at 0.05. RESULTS: A difference in injectate volume of distribution within or at the base of the EOMC was not detected among groups. The median optic nerve circumference of injectate distribution was significantly higher in the RB injected group than in the PB-2 group. Injectate distribution following RB, PB-1 and PB-2 injections was graded as likely to provide regional anesthesia within the EOMC in 40%, 19% and 31% of eyes, and at the EOMC base in 60%, 63% and 50% of eyes, respectively. The probability of likelihood to provide regional anesthesia was lower in dogs of higher body weights. The IOP was significantly higher than baseline following PB-1 (18 ± 14 mmHg) and in comparison with RB (2 ± 3 mmHg), but not different from PB-2 injection (10 ± 11 mmHg). CONCLUSIONS AND CLINICAL RELEVANCE: None of the techniques reliably produced 'successful' injectate distribution based on this study's definitions; however, clinical assessment of anesthetic success is required.

A RETROSPECTIVE COMPARISON OF CHEMICAL IMMOBILIZATION WITH THIAFENTANIL, THIAFENTANIL-AZAPERONE, OR ETORPHINE-ACEPROMAZINE IN CAPTIVE PERSIAN FALLOW DEER (DAMA DAMA MESOPOTAMICA).

Records of 56 Persian fallow deer (Dama dama mesopotamica) immobilized for translocation were reviewed. Twenty-three were administered 0.05 ± 0.01 (mean ± SD) mg/kg thiafentanil (THIA), 20 were administered 0.045 ± 0.008 mg/kg thiafentanil combined with 0.19 ± 0.03 mg/kg azaperone (THIA-AZP), and 13 were administered 0.032 ± 0.04 mg/kg etorphine-acepromazine (ETOR-ACP) by intramuscular remote injection. Parameters recorded and compared between groups included induction and recovery times, heart rate, respiratory rate, rectal temperature, oxygen saturation, blood pressure, reflexes, quality of immobilization, and blood concentrations of lactate and glucose. Naltrexone (THIA groups) or diprenorphine (ETOR-ACP) were administered for reversal. Mean induction time was significantly shorter in the THIA group versus the ETOR-ACP group (2.0 ± 1.3 and 4.8 ± 2.8 min, respectively), but not significantly shorter than the THIA-AZP group (2.8 ± 3.1 min). Respiratory rate was significantly higher in the THIA group in comparison to the two other groups. None of the protocols provided excellent immobilization quality, which was significantly poorer in the THIA group. Following antagonist administration, all deer from the THIA and ETOR-ACP groups recovered quickly, while there were five perianesthetic morbidity and mortality cases in the THIA-AZP group. Mean recovery time was significantly shorter in the THIA group versus the THIA-AZP and ETOR-ACP groups (0.5 ± 0.3, 1.1 ± 0.8, and 2.3 ± 1.1 min, respectively). In conclusion, the use of THIA provided faster induction and recovery, with less respiratory depression, but poorer immobilization. The THIA-AZP combination should be used with caution in Persian fallow deer until further investigation.

Effect of morphine, methadone, hydromorphone or oxymorphone on the thermal threshold, following intravenous or buccal administration to cats.

OBJECTIVE: To determine the effects of morphine, methadone, hydromorphone or oxymorphone on the thermal threshold in cats, following buccal and intravenous (IV) administration. STUDY DESIGN: Randomized crossover study. ANIMALS: Six healthy adult female ovariohysterectomized cats weighing 4.5 ± 0.4 kg. METHODS: Morphine sulfate (0.2 mg kg-1 IV or 0.5 mg kg-1 buccal), methadone hydrochloride (0.3 mg kg-1 IV or 0.75 mg kg-1 buccal), hydromorphone hydrochloride (0.1 mg kg-1 IV or 0.25 mg kg-1 buccal) or oxymorphone hydrochloride (0.1 mg kg-1 IV or 0.25 mg kg-1 buccal) were administered. All cats were administered all treatments. Skin temperature and thermal threshold were measured in duplicate prior to drug administration, and at various times up to 8 hours after drug administration. The difference between thermal threshold and skin temperature (ΔT) was analyzed. RESULTS: Administration of methadone and hydromorphone IV resulted in significant increases in ΔT at 40 minutes after drug administration. Buccal administration of methadone resulted in significant increases in thermal threshold, although no significant difference from baseline measurement was detected at any time point. IV administration of morphine and oxymorphone, and buccal administration of morphine, hydromorphone and oxymorphone did not cause significant thermal antinociception. CONCLUSION AND CLINICAL RELEVANCE: At the doses used in this study, IV administration of methadone and hydromorphone, and buccal administration of methadone resulted in transient thermal antinociception. The results of this study do not allow us to predict the usefulness of these drugs for providing analgesia in clinical patients.

Effect of One-Lung Ventilation With or Without Low-Pressure Carbon Dioxide Insufflation on Cardiorespiratory Variables in Cats Undergoing Thoracoscopy.

OBJECTIVES: To document a technique for one-lung ventilation (OLV) in cats and evaluate the effect of low-pressure carbon dioxide insufflation and OLV (OLV-CDI) on cardiorespiratory variables in cats. STUDY DESIGN: Prospective randomized study. ANIMALS: Cats (n = 6). METHODS: General anesthesia was induced using a standardized anesthetic protocol. A thermodilution catheter was placed into the pulmonary artery using fluoroscopic guidance. Two 6 mm thoracoscopic cannulae were placed at a subxiphoid and intercostal location, respectively, to allow direct observation of all lung lobes. OLV was induced using an endobronchial blocker, which was placed into the right and left main stem bronchi in randomized order using bronchoscopic guidance. Cardiorespiratory variables were measured at 5 and 30 minutes after induction of OLV and subsequently at 5 and 30 minutes after initiation of OLV-CDI at intra-thoracic pressures of 3 mmHg. RESULTS: Left-sided OLV was successful in 5 cats, right-sided OLV was successful in 2 cats, and neither was successful in 1 cat. No significant effects on hemodynamic variables or oxygen delivery were observed after right or left-sided OLV alone. Hemodynamic variables were also well-preserved after OLV-CDI; however, oxygen delivery was significantly lower after left OLV-CDI compared with right OLV-CDI, and in 2 cats, severe desaturation occurred after L-OLV-CDI before the 30 minute time point. CONCLUSIONS: OLV can be used in cats for thoracoscopic interventions. Although right OLV-CDI was tolerated better than left OLV-CDI, the technique requires further investigation before it can be recommended for widespread clinical use.

IMMOBILIZATION OF CAPTIVE NUBIAN IBEX (CAPRA NUBIANA) WITH BUTORPHANOL-MIDAZOLAM-MEDETOMIDINE OR BUTORPHANOL-AZAPERONE-MEDETOMIDINE AND ATIPAMEZOLE REVERSAL.

Seventeen captive Nubian ibex (Capra nubiana) were immobilized for transportation and/or hoof trimming, deworming, and vaccinations. Of these, 11 were immobilized with a combination of butorphanol (0.13±0.03 mg/kg), midazolam (0.13±0.03 mg/kg), and medetomidine (0.13±0.03 mg/kg) (BMM), and 6 were immobilized with a combination of butorphanol (0.11±0.03 mg/kg), azaperone (0.22±0.06 mg/kg), and medetomidine (0.11±0.03 mg/kg) (BAM) by intramuscular injection. Induction and recovery times were recorded. Heart rate, respiratory rate, rectal temperature, blood pressure, and oxygen saturation were measured. The quality of induction, immobilization, and recovery were scored (scale 1-5; 1=poor, 5=excellent). Mean induction time was significantly shorter in the BMM group versus the BAM group (8.8±2.7 and 20.1±7.8 min, respectively). Median induction score and median immobilization score were significantly higher (i.e., better) in the BMM group than the BAM group (5 versus 2.5 and 4 versus 3, respectively). The mean and diastolic blood pressures were significantly higher in the BMM group at the 25-min time point. Atipamezole was administered at the end of procedures, and all ibex recovered smoothly. Mean recovery time was significantly longer in the BMM group versus the BAM group (9.5±4.3 and 3.3±2.2, respectively). In conclusion, at the doses used, the combination of BMM was superior to BAM for short-term immobilization in captive Nubian ibex.

Taenia multiceps brain cyst removal in two wild Nubian ibex (Capra nubianas).

Two wild adult Nubian ibex (Capra nubiana) were captured and admitted to the Hebrew University Veterinary Teaching Hospital with various neurologic signs, including alerted mentation, head tilt, and pathologic nystagmus. The lesion in the central nervous system was localized to the forebrain in one ibex and to the cerebellum of the other. Both ibex's were diagnosed with brain cyst using computed tomography (CT). Craniectomy was performed to remove the cysts, and both animals returned to their natural environment after a rehabilitation period. Parasitologic examination revealed cysts of Taenia multiceps coenurus. This is the first report to describe the neurologic signs, CT findings, surgical procedure, and follow-up postsurgery information in wild Capra nubiana.

Naltrexone does not affect isoflurane minimum alveolar concentration in cats.

OBJECTIVE: To test whether naltrexone, an opioid receptor antagonist, affects the minimum alveolar concentration (MAC) of isoflurane in cats, a species that is relatively resistant to the general anesthetic sparing effects of most opioids. STUDY DESIGN: Randomized, crossover, placebo-controlled, blinded experimental design. ANIMALS: Six healthy adult cats weighing 4.9 ± 0.7 kg. METHODS: The cats were studied twice. In the first study, baseline isoflurane MAC was measured in duplicate. The drug (saline control or 0.6 mg kg(-1) naltrexone) was administered IV every 40-60 minutes, and isoflurane MAC was re-measured. In the second study, cats received the second drug treatment using identical methods 2 weeks later. RESULTS: Isoflurane MAC was 2.03 ± 0.12% and was unchanged from baseline following saline or naltrexone administration. CONCLUSION AND CLINICAL RELEVANCE: Minimum alveolar concentration was unaffected by naltrexone. Because MAC in cats is unaffected by at least some mu-opioid agonists and antagonists, spinal neurons that are directly modulated by mu-opioid receptors in this species cannot be the neuroanatomic sites responsible for immobility from inhaled anesthetics.

Retrobulbar and peribulbar regional techniques in cats: a preliminary study in cadavers.

OBJECTIVE: To compare injectate distribution and potential complications of retrobulbar and peribulbar injections in cat cadavers. STUDY DESIGN: Prospective randomized masked study. ANIMALS: Ten cat cadavers (20 eyes). METHODS: A dorsomedial retrobulbar injection (RB) of 1 mL of 0.5% bupivacaine and iopamidol (1:1) was performed in seven eyes. A dorsomedial peribulbar injection (PB-1) of 4 mL of the same injectate was performed in seven eyes, and two peribulbar injections (PB-2) of the same injectate, divided equally between the dorsomedial and ventrolateral regions (2 mL each) were performed in six eyes. Intraocular pressure (IOP) was measured before, immediately and 15 minutes after injection. Cadavers underwent computed tomography before and following injections. A radiologist scored injectate distribution within the intraconal space (none, moderate, or large) and around the optic nerve (degrees). An injection was defined as likely to provide adequate regional anesthesia if the volume of distribution of intraconal injectate was 'large' and it contacted over 270° of the optic nerve circumference. RESULTS: The success rate (95% confidence interval) of RB, PB-1, and PB-2 injections was 71% (29.0-96.3%), 86% (42.1-99.6%), and 67% (22.3-95.7%), respectively. With all three techniques, IOP increased significantly after injection, but returned to baseline by 15 minutes following RB injection. No intraocular, intravascular, intrathecal, or intraneural injectate was observed. CONCLUSION AND CLINICAL RELEVANCE: The single-peribulbar injection technique may be superior to retrobulbar or double-peribulbar injections, however, all techniques require further studies in live cats to determine safety and efficacy prior to clinical use.

Anesthesia, pain management and surgical approach of ovariectomy or orchiectomy in six Egyptian fruit bats (Rousettus aegyptiacus): A case report.

The purpose of this report is to describe the anesthetic and analgesic management and the surgical procedures of gonadectomy in six (four females and two males) healthy adult Egyptian fruit bats (Rousettus aegyptiacus). Bats were anesthetized with a combination of alfaxalone, midazolam, and morphine administered subcutaneously. Incisional line infiltration using bupivacaine was administered in all bats, and additional bilateral intratesticular injection was administered in the males. Ovariectomy was performed via a dorsal approach, by bilateral midline skin incisions at the paralumbar fossa level. Orchiectomy was performed via a ventral approach, by bilateral midline incisions of scrotal skin above the testes. Following surgery, all bats were administered flumazenil for midazolam reversal, and meloxicam for postoperative analgesia, subcutaneously. All bats recovered from anesthesia uneventfully. Bats were monitored for complications up to 10 days following surgery, when skin sutures were removed. No morbidities or mortalities occurred during this period in any of the bats. In conclusion, ventral approach orchiectomy and dorsal approach ovariectomy using the injectable combination alfaxalone-midazolam-morphine in conjunction with local anesthesia and meloxicam are feasible procedures in Egyptian fruit bats and can be performed with relative ease. However, further studies using these techniques in a larger group of bats should be performed to establish their safety.