cis-Atracurium in dogs with and without porto-systemic shunts.

OBJECTIVE: To evaluate the non-depolarizing neuromuscular blocking drug cis-atracurium in dogs with porto-systemic shunts, and to compare it in clinically normal animals. ANIMALS: Thirteen dogs of mixed breed and sex, aged between 3 and 31 months old, weighing 2.2-25.5 kg, with ASA physical status II-IV, and undergoing surgical attenuation of porto-systemic shunt. A control group of 11 bitches of mixed breed, between 8 and 60 months old, and weighing 4.5-41.0 kg, all ASA physical status I, undergoing routine ovarohysterectomy were also studied. MATERIALS AND METHODS: Pre-anaesthetic medication was an opioid analgesic, given either alone or in combination with acepromazine. Following induction of general anaesthesia with intravenous (IV) propofol and oro-tracheal intubation, anaesthesia was maintained using isoflurane in either oxygen or oxygen and nitrous oxide. Ventilation was controlled. The train of four (TOF) technique was used to monitor neuromuscular blockade. An initial dose of 0.1 mg kg(-1)cis-atracurium was given IV and additional doses of 0.03 mg kg(-1)cis-atracurium were administered when at least one twitch of the TOF was present. RESULTS: Except for one dog that was killed during surgery because its anomaly was inoperable, all animals recovered satisfactorily from anaesthesia and surgery. In dogs with porto-systemic shunt, onset of neuromuscular blockade was 3.1 +/- 1.1 minutes (mean +/- SD) and in control dogs was 3.4 +/- 0.7 minutes (not significantly different). Neuromuscular blockade lasted 34 +/- 13 minutes in dogs with porto-systemic shunt and 29 +/- 17 minutes in control dogs (not significantly different). CONCLUSIONS: The presence of porto-systemic shunt did not affect the rate of onset or duration of action of cis-atracurium. CLINICAL RELEVANCE: cis-Atracurium may have a use in veterinary anaesthesia for producing neuromuscular blockade in dogs with hepatic insufficiency, including those with porto-systemic shunt.

Comparison of two thiopental infusion rates for the induction of anaesthesia in dogs.

OBJECTIVE: To compare the induction dose requirements of thiopental using two different infusion rates for induction of anaesthesia in dogs. STUDY DESIGN: Prospective, randomized study. ANIMALS: Fifty, healthy (ASA I or II) client-owned dogs with a mean age of 4.1 years and a mean mass of 20.4 kg undergoing elective surgery. MATERIALS AND METHODS: Animals were randomly assigned to receive an infusion of 2.5% thiopental at a rate of either 0.1 ml kg(-1) minute(-1) or 0.4 ml kg(-1)minute(-1), 30-40 minutes after pre-anaesthetic medication with intramuscular acepromazine (0.025 mg kg(-1)) and pethidine (3.5 mg kg(-1)). Thiopental administration was controlled by a precision syringe driver. Statistical analyses of the results, using the outcome 'mg kg(-1) required for induction' (log-transformed) included unpaired t-tests for all categorical data (thiopental infusion rate, breed, sex, obesity, sedation quality) and univariable linear regression for continuous variables (mass, age). All variables were then considered in a multivariable linear regression model. The quality of induction with the two different infusion rates was also assessed. RESULTS: After controlling for quality of sedation, the thiopental induction dose requirement was significantly less (p < 0.001) with the slower infusion rate (median = 7.5 mg kg(-1); range 4.9-13.7) compared with the faster infusion rate (median =11.0 mg kg(-1); range 6.6-18.0). The quality of sedation also affected the dose required (p = 0.03). The slower infusion rate was associated with a significantly poorer induction quality (p = 0.03) [corrected] CONCLUSIONS: Slow thiopental infusion (0.1 ml kg(-1) minute(-1)) for anaesthesia induction after acepromazine/pethidine pre-anaesthetic medication reduced the induction dose requirement, although the quality of induction was inferior. CLINICAL RELEVANCE: The induction dose of thiopental was reduced with a slower administration rate and so slow administration is recommended in thiopental-sensitive animals.

Overdose during chemical restraint in a black rhinoceros (Diceros bicornis).

A juvenile female black rhinoceros (Diceros bicornis) was successfully treated after overdose of drugs used for chemical restraint. Subsequent general anaesthesia for surgical reduction of a recurrent rectal prolapse was uneventful. Over a 25-minute period before transportation to the veterinary hospital, the animal received a total dose of 1.225 mg etorphine, 30 mg acepromazine and 30 mg detomidine. Based on an estimated mass of 200 kg, these corresponded to doses of 6.1 microg kg(-1) etorphine, 150 microg kg(-1) acepromazine, and 150 microg kg(-1) detomidine which constitutes considerable overdose for each drug given separately, notwithstanding the synergy that probably resulted when the three drugs were present concurrently. The estimated body mass may have substantially overestimated the actual body mass and exacerbated overdosage. The animal was recumbent and apnoeic on arrival at the hospital. Heart sounds were auscultated and a weak peripheral pulse was palpated; no pulse deficits were detected, although the heart rate was low. The trachea was intubated, inspired breath was enriched with oxygen and the lungs ventilated manually. Diprenorphine (1.5 mg) was given intravenously and spontaneous breathing resumed 11 minutes later. After induction of general anaesthesia using isoflurane, emergency surgery for correction of rectal prolapse was performed, from which the animal recovered uneventfully. The case highlights some of the practical problems that may be encountered in dealing with dangerous and unfamiliar species.

Acid-base, blood gas, and physiologic parameters during laparoscopy in the head-down position in white-tailed deer (Odocoileus virginianus).

The objective of this project was to evaluate the acid-base, blood gas, and physiologic parameters of white-tailed deer (Odocoileus virginianus) during laparoscopy in the head-down position. Eleven white-tailed does were captured and then immobilized with xylazine (6 mg/kg i.m.) and ketamine (7 mg/kg i.m.). The deer were intubated orotracheally and maintained with isoflurane in oxygen. The deer were positioned in dorsal recumbency and positive pressure ventilated. Heart rate (HR), arterial blood pressure, end-tidal carbon dioxide concentration (FE/CO2), and CO2 insufflation pressure were recorded every 5 min. Respiratory parameters, plasma electrolytes, and peak inspiratory pressure were measured immediately before tilting deer in the head-down position (45-55 degrees), 5 min after tilting, and immediately before the end of the procedure (while tilted). Butorphanol (0.05 mg/kg i.m.) was administered at the end of the procedure and yohimbine (0.2 mg/kg i.v.) administered before release. The deer weighed 52 kg (28-70 kg) [median (minimum-maximum)]. The peak inspiratory pressure in dorsal recumbency while still horizontal was 25 cm H2O (16-28 cm H2O), which increased to 29 cm H2O (18-46 cm H2O) after tilting (P = 0.02). PaO2, PaCO2, FE/CO2, and pH did not change after tilting in the head-down position or after insufflation. HR did not change during the anesthetic period. Mean arterial pressure did not change after tilting or abdominal insufflation, but decreased by the end of the anesthetic period (approximately 1 hr). Time from intubation to extubation was 117 min (72-170 min) (n = 5) and surgery time was 31 min (17-60 min; n = 10). We conclude that captured white-tailed deer have minimal derangements to acid-base, blood gas, or physiologic parameters during laparoscopy in the head-down position with abdominal insufflation, and thus this procedure may be performed safely in ventilated white-tailed deer.