Use of sevoflurane for anesthetic management of horses during thoracotomy

Objective - To evaluate sevoflurane as an inhalation anesthetic for thoracotomy in horses. Animals - 18 horses between 2 and 15 years old. Procedure - 4 horses were used to develop surgical techniques and were euthanatized at the end of the procedure. The remaining 14 horses were selected, because they had an episode of bleeding from their lungs during strenuous exercise. General anesthesia was induced with xylazine (1.0 mg/kg of body weight, IV) followed by ketamine (2.0 mg/kg, IV). Anesthesia was maintained with sevoflurane in oxygen delivered via a circle anesthetic breathing circuit. Ventilation was controlled to maintain Paco₂ at approximately 45 mm Hg. Neuromuscular blocking drugs (succinylcholine or atracurium) were administered to eliminate spontaneous breathing efforts and to facilitate surgery. Cardiovascular performance was monitored and supported as indicated. Results - 2 of the 14 horses not euthanatized died as a result of ventricular fibrillation. Mean (± SD) duration of anesthesia was 304.9 ± 64.1 minutes for horses that survived and 216.7 ± 85.5 minutes for horses that were euthanatized or died. Our subjective opinion was that sevoflurane afforded good control of anesthetic depth during induction, maintenance, and recovery. Conclusions and Clinical Relevance - Administration of sevoflurane together with neuromuscular blocking drugs provides stable and easily controllable anesthetic management of horses for elective thoracotomy and cardiac manipulation.