Isoflurane anesthesia for equine colic surgery. Comparison with halothane anesthesia

Isoflurane was compared with halothane as an anesthetic agent for emergency colic surgery in a series of 38 juvenile and adult horses. After presurgical stabilization with fluids and supportive medications, anesthesia was induced by intravenous xylazine and/or diazepam followed by ketamine. Anesthesia was maintained with isoflurane or halothane in oxygen with controlled ventilation. Heart rates (HR), arterial blood gases, mean arterial pressures (MAP), rate pressure products (RPP), requirements for cardiovascular support medications, and recovery times to standing were compared using nonparametric methods. Cardiopulmonary responses to isoflurane and halothane anesthesia were generally comparable although some temporal differences were observed. Higher HR (p less than 0.02) and lower PaCO2 levels (p less than 0.01) were identified during the course of isoflurane anesthesia. Recovery times to standing were significantly shorter (0.02 less than p less than 0.05) after isoflurane than halothane anesthesia.