Comparison of racemic ketamine and S-ketamine as agents for the induction of anaesthesia in goats.

Objective: To compare racemic ketamine and S-ketamine as induction agents prior to isoflurane anaesthesia.
Study Design: Prospective, blinded, randomized experimental study.
Animals: Thirty-one healthy adult goats weighing 39-86 kg.
Methods: Goats were premedicated with xylazine (0.1 mg kg(-1)) intravenously (IV) given over 5 minutes. Each goat was assigned randomly to one of two treatments for IV anaesthetic induction: group RK (15 goats) racemic ketamine (3 mg kg(-1)) and group SK (16 goats) S-ketamine (1.5 mg kg(-1)). Time from end-injection to recumbency was measured and quality of anaesthetic induction and condition for endotracheal intubation were scored. Anaesthesia was maintained with isoflurane in oxygen for 90 minutes. Heart rate, invasive arterial blood pressure, oxygen saturation, temperature, end-tidal carbon dioxide and isoflurane were recorded every 5 minutes. Arterial blood samples were taken for analysis every 30 minutes. Recovery time to recurrence of swallowing reflex, to first head movement and to standing were recorded and recovery quality was scored. Two-way repeated measures anova, Mann-Whitney and a Mantel-Cox tests were used for statistical analysis as relevant with a significance level set at p<0.05.
Results: Induction of anaesthesia was smooth and uneventful in all goats. There was no statistical difference between groups in any measured parameter. Side effects following anaesthetic induction included slight head or limb twitching, moving forward and backward, salivation and nystagmus but were minimal. Endotracheal intubation was achieved in all goats at first or second attempt. Recovery was uneventful on all occasions. All goats were quiet and needed only one or two attempts to stand.
Conclusions and Clinical Relevance: S-ketamine at half the dose rate of racemic ketamine in goats sedated with xylazine and thereafter anaesthetised with isoflurane induces the same clinically measurable effects.
(© 2010 The Authors. Veterinary Anaesthesia and Analgesia © 2010 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.)