• Lydia Love, Christine Egger, Barton Rohrbach, Sherry Cox, Meredith Hobbs, and Thomas Doherty.
• Animal Emergency & Referral Associates, Fairfield, NJ, USA.
• Vet Anaesth Analg. 2011 Jul 1;38(4):292-300.

ObjectiveTo determine the effect of intravenous ketamine on the minimum alveolar concentration of sevoflurane needed to block autonomic response (MAC(BAR)) to a noxious stimulus in dogs.Study DesignRandomized, crossover, prospective design.AnimalsEight, healthy, adult male, mixed-breed dogs, weighing 11.2-16.1 kg.MethodsDogs were anesthetized with sevoflurane on two occasions, 1 week apart, and baseline MAC(BAR) (B-MAC(BAR)) was determined on each occasion. MAC(BAR) was defined as the mean of the end-tidal sevoflurane concentrations that prevented and allowed an increase (≥15%) in heart rate or invasive mean arterial pressure in response to a noxious electrical stimulus (50 V, 50 Hz, 10 ms). Dogs then randomly received either a low-dose (LDS) or high-dose series (HDS) of ketamine, and treatment MAC(BAR) (T-MAC(BAR)) was determined. The LDS had an initial loading dose (LD) of 0.5 mg kg(-1) and constant rate infusion (CRI) at 6.25 μg kg(-1) minute(-1), followed, after T-MAC(BAR) determination, by a second LD (1 mg kg(-1)) and CRI (12.5 μg kg(-1) minute(-1)). The HDS had an initial LD (2 mg kg(-1)) and CRI (25 μg kg(-1) minute(-1)) followed by a second LD (3 mg kg(-1)) and CRI (50 μg kg(-1) minute(-1)). Data were analyzed with a mixed-model anova and are presented as LSM ± SEM.ResultsThe B-MAC(BAR) was not significantly different between treatments. Ketamine at 12.5, 25, and 50 μg kg(-1) minute(-1) decreased sevoflurane MAC(BAR), and the maximal decrease (22%) occurred at 12.5 μg kg(-1) minute(-1). The percentage change in MAC(BAR) was not correlated with either the log plasma ketamine or norketamine concentration.Conclusions And Clinical RelevanceKetamine at clinically relevant doses of 12.5, 25, and 50 μg kg(-1) minute(-1) decreased sevoflurane MAC(BAR), although the reduction was neither dose-dependent nor linear.© 2011 The Authors. Veterinary Anaesthesia and Analgesia. © 2011 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesiologists.

29 keywords...

hide…