• Nicola J Grint and Pamela J Murison.
• Department of Clinical Veterinary Science, University of Bristol, Bristol, UK. n.j.grint@liverpool.ac.uk
• Vet Anaesth Analg. 2008 Mar 1;35(2):113-21.

ObjectiveTo compare ketamine-midazolam (KMZ) and ketamine-medetomidine (KMT) anaesthesia in rabbits using anaesthetic induction, maintenance and recovery data.Study DesignRandomized, prospective, blinded clinical trial.AnimalsFifty rabbits (25 male, 25 female) of different breeds undergoing ovariohysterectomy or castration. Rabbits were 12.7 +/- 9.8 months old with body mass 2.24 +/- 0.61 kg.Study DesignRandomized, prospective, blinded clinical trial.MethodsKetamine (15 mg kg(-1)) and midazolam (3 mg kg(-1)) or medetomidine (0.25 mg kg(-1)) were administered by intramuscular (IM) injection. Ten minutes after IM injection, blind intubation of the trachea was attempted. The time taken, the number of attempts and a subjective score of the ease of intubation were recorded. Isoflurane (range 0-3.6%) in 100% oxygen was delivered via a Jackson Rees modification of an Ayre's T-piece non-rebreathing system. Carprofen (3 mg kg(-1)) and dextrose saline (5 mL kg(-1) hour(-1)) were administered intravenously (IV). During surgery heart rate (HR), respiratory rate (RR) and arterial oxygen saturation of haemoglobin (SpO(2)) were monitored. Times to extubation and first head lift were recorded. Group KMT received atipamezole (0.5 mg kg(-1)) IM 30 minutes after discontinuation of isoflurane. Activity was scored at 30, 60 and 120 minutes after volatile agent discontinuation. Mean time to loss of righting reflex (LRR), body mass, RR and vaporizer setting were compared using a two-tailed t-test. Median values for all other data were compared using a Mann-Whitney test.ResultsMean time to LRR (+/-SD) was significantly shorter with KMT (1.64 +/- 0.55 minutes) compared with KMZ (2.28 +/- 0.66 minutes). Intubation was not possible in seven rabbits (three with KMT, four with KMZ) and three with KMT developed laryngospasm. Mean HR, SpO(2) and vaporizer settings were all significantly lower in group KMT.Conclusion And Clinical RelevanceKMT has a faster onset of action and a greater isoflurane-sparing effect when compared with KMZ. Rabbits with KMT were more prone to laryngospasm and had significantly lower HR.

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