Reversible anesthesia of captive California sea lions (Zalophus californianus) with medetomidine, midazolam, butorphanol, and isoflurane.

Two adult California sea lions (Zalophus californianus) were effectively anesthetized 13 times with medetomidine (0.010-0.013 mg/kg), midazolam (0.2-0.26 mg/kg), and butorphanol (0.2-0.4 mg/kg) by i.m. hand or pole syringe injection. For each anesthetic event, atropine (0.02 mg/kg, i.m.) was administered 6-20 min after initial injections, and oxygen administration via face mask or nasal insufflation began at the same time. Light anesthesia was induced in 8-22 min and lasted 13-78 min. During eight of the procedures, isoflurane (0.5-2.0%) was administered via face mask or endotracheal tube for an additional 30-120 min to facilitate longer procedures or surgery. Anesthesia was antagonized with atipamezole (0.05-0.06 mg/kg) and naltrexone (0.1 mg/kg) in seven events, with the addition of flumazenil (0.0002-0.002 mg/kg) in six events. The antagonists were administered by i.m. injection 42-149 min after administration of the induction agents. All sea lions recovered to mild sedation within 4-17 min after administration of the antagonists.