A randomized clinical trial to compare ketamine-butorphanol-azaperone-medetomidine and detomidine-etorphine-acepromazine for anesthesia of captive Przewalski horses (Equus przewalskii)

Abstract

Abstract OBJECTIVE To compare ketamine-butorphanol-azaperone-medetomidine (KBAM) to detomidine-etorphine-acepromazine (DEA) for field anesthesia in captive Przewalski horses (Equus przewalskii). ANIMALS 10 adult Przewalski horses. PROCEDURES A prospective randomized crossover trial was conducted. Each horse was immobilized once with KBAM (200 mg ketamine, 109.2 mg butorphanol, 36.4 mg azaperone, and 43.6 mg medetomidine) and once with DEA (40 mg detomidine premedication, followed 20 minutes later by 3.9 to 4.4 mg etorphine and 16 to 18 mg acepromazine). Both protocols were administered by IM remote dart injection with a washout period of 6 months between treatments. Selected cardiorespiratory variables and quality of anesthesia were recorded. Antagonists were administered IM (KBAM, 215 mg atipamezole and 50 mg naltrexone; DEA, 4 mg RX821002 and 100 mg naltrexone). RESULTS All horses were anesthetized and recovered uneventfully. Inductions (DEA, 6.8 min; KBAM, 11.6 min; P = 0.04) and recoveries (DEA, 3.2 min; KBAM, 19.6 min; P < 0.01) were faster with DEA compared with KBAM. Quality scores for induction and recovery did not differ between protocols, but maintenance quality was poorer for DEA (P < 0.01). Clinical concerns during DEA immobilizations included apnea, severe hypoxemia (arterial partial pressure of oxygen < 60 mm Hg), muscle rigidity, and tremors. Horses treated with KBAM were moderately hypoxemic, but arterial partial pressures of oxygen were higher compared with DEA (P < 0.01). CLINICAL RELEVANCE Captive Przewalski horses are effectively immobilized with KBAM, and this protocol results in superior muscle relaxation and less marked hypoxemia during the maintenance phase, but slower inductions and recoveries, compared with DEA.