Physiologic effects of anesthesia induced and maintained by intravenous administration of a climazolam-ketamine combination in ponies premedicated with acepromazine and xylazine

Abstract

Objective - To examine the physiologic and pharmacokinetic effects of a technique of total intravenous anesthesia in ponies. Animals - 6 healthy ponies. Procedure - Ponies were premedicated with acepromazine (0.03 mg/kg of body weight, IV) and xylazine (1.0 mg/kg, IV). Two minutes later, anesthesia was induced with ketamine (2.0 mg/kg, IV) followed by climazolam (0.2 mg/kg, IV). Anesthesia was maintained for 120 minutes by an infusion of climazolam (0.4 mg/kg/h) and ketamine (6.0 mg/kg/h). Oxygen (5 L/min) was supplemented. 20 minutes after the infusion was stopped, sarmazenil (0.04 mg/kg, IV) was administered. Cardiovascular and respiratory function measurements were taken before and after premedication, and during anesthesia. Plasma cortisol, ACTH, and catecholamine concentrations were used to assess adrenal and pituitary gland function. Ketamine and climazolam kinetics were calculated, on the basis of plasma drug concentrations. Results - There were no significant changes from prexylazine values in heart rate, respiratory rate, arterial blood pressure, cardiac index, systemic vascular resistance, or arterial P(O2), P(CO2), and pH. Plasma cortisol concentration decreased during anesthesia, but plasma ACTH and catecholamine concentrations did not change. Recovery was fairly smooth, but some excitement and ataxia were noted in 2 ponies. Conclusion - Ketamine-climazolam infusion appeared suitable for maintenance of anesthesia in ponies, although recovery was not ideal in 2 of 6 ponies.