Total intravenous anesthesia with alfaxalone, dexmedetomidine and remifentanil in healthy foals undergoing abdominal surgery

Abstract

ObjectiveTo evaluate effects of anesthesia induced with alfaxalone and maintained with alfaxalone, dexmedetomidine and remifentanil infusions in foals. Study designProspective, experimental study. AnimalsA group of six healthy foals [median (range) 11 (8–33) days] undergoing abdominal surgery. MethodsIntravenous (IV) dexmedetomidine (3–7μgkg−1) provided sedation for insertion of a pulmonary artery catheter. IV anesthesia was induced with alfaxalone (2mgkg−1) and maintained with alfaxalone (6mgkg−1hour−1), dexmedetomidine (1μgkg−1hour−1) and remifentanil (3μgkg−1hour−1). Foals were endotracheally intubated and lungs were mechanically ventilated with oxygen. Cardiac output (thermodilution), heart rate and systemic arterial pressure were measured. Arterial and mixed venous blood was analyzed for PO2 and PCO2, and glucose, lactate and electrolyte concentrations. Anesthetic depth was subjectively assessed. Systemic vascular resistance (SVR), oxygen utilization and intrapulmonary shunt were calculated. Preinduction (PB) or 10 minutes postinduction (+10B) data were used as baselines with one-way analysis of variance for repeated measures. Data are mean ± standard deviation; significance was p ≤ 0.05. ResultsDuration of anesthesia was 129 ± 22minutes. One foal was administered additional alfaxalone (0.5mgkg−1) following induction. Cardiac index decreased to 107 ± 31 and 87 ± 21mLkg−1minute−1 at 60 and 80minutes, respectively, compared with PB (157 ± 33mLkg−1minute−1). SVR increased to 1223 ± 166dynessecond−1cm−5 at 80minutes compared with +10B (704 ± 247dynessecond−1cm−5). Mean arterial pressures were 63–128mmHg. Time from stopping infusions to standing was 46–106minutes. All foals were hypothermic (<36°C) and three foals were administered atipamezole (0.05mgkg−1) intramuscularly during recovery. Conclusionand clinical relevance Combined alfaxalone–dexmedetomidine–remifentanil provided suitable anesthesia to permit laparotomy in foals. At the doses evaluated, prolonged recovery may occur.