Complications associated with administration of detomidine into the caudal epidural space in a horse

A 364-kg (800-lb) 15-month-old sexually intact cryptorchid male Quarter Horse was admitted to the veterinary teaching hospital for castration. The horse was placed in standing stocks, and a caudal epidural injection of 18 mg of detomidine hydrochloride (50 micrograms/kg [23 micrograms/lb] of body weight) was administered. Fifteen minutes after injection, the horse unexpectedly collapsed to the floor, first into sternal, and then into lateral, recumbency. Because the horse would not get up, the decision was made to perform the surgery with the horse under general anesthesia. The horse required little halothane to maintain a surgical plane of anesthesia for most of the duration of surgery. Recovery from anesthesia was prolonged. Care must be taken when anesthetizing horses that have received large doses of detomidine via caudal epidural injection.