• Kathy L Murphy, Johnny V Roughan, Mark G Baxter, and Paul A Flecknell.
• Department of Experimental Psychology, University of Oxford, South Parks Road, Oxford, UK. kathy.murphy@vet.ox.ac.uk
• Vet Anaesth Analg. 2010 May 1; 37 (3): 222-9.

ObjectiveTo assess the effects of premedication with buprenorphine on the characteristics of anaesthesia induced with ketamine/medetomidine.Study DesignProspective crossover laboratory study.AnimalsSix female New Zealand White rabbits.MethodsRabbits received, on occasions separated by 7 days, either buprenorphine (0.03 mg kg(-1)) or saline subcutaneously (SC) as premedication, followed 1 hour later by SC ketamine (15 mg kg(-1)) and medetomidine (0.25 mg kg(-1)) (K/M). At pre-determined time points reflex responses and cardiopulmonary parameters were recorded and arterial blood samples taken for analysis. Total sleep time was the duration of loss of the righting reflex. Duration of surgical anaesthesia was the time of suppression of the ear pinch and pedal withdrawal reflexes. Wilcoxon signed-ranks tests were used to compare data before (T(0)) and 10 minutes after (T(10)) injection with K/M.ResultsAll animals lost all three reflex responses within 10 minutes of injection of K/M. The duration of loss of these reflexes significantly increased in animals that received buprenorphine. At induction, animals that had received buprenorphine tended to have a lower respiration rate but there were no significant differences in arterial PCO(2), PO(2) or pH between treatments. Hypoxaemia [median PaO(2) < 6.0 kPa (45 mmHg)] developed in both treatments at T(10) but there was no significant difference between treatments. Mean arterial pressure (MAP) was lower at T(10) in animals that had received buprenorphine.Conclusion And Clinical RelevancePremedication with buprenorphine significantly increased the duration of anaesthesia induced by K/M, with no significant depression of respiration further to the control treatment within the first 10 minutes of anaesthesia. The MAP decreased but this was not reflected in a difference in other physiological parameters. These data show that premedication with buprenorphine, before K/M anaesthesia in the rabbit, has few negative effects and may provide beneficial analgesia.

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