The effect of epidural xylazine on halothane minimum alveolar concentration in ponies

Thomas J. Doherty
Dennis R. Geiser
Barton W. Rohrbach Dr., University of Tennessee - Knoxville

Abstract

The effects of epidurally administered xylazine on halothane minimum alveolar concentration (MAC) were examined in 6 healthy pony geldings. Anaesthesia was induced with i.v. administration of thiopentone (4 mg/kg) and succinylcholine (0.15 mg/kg) and maintained with halothane in oxygen. Following baseline halothane MAC determination, each pony was given 0.15 mg/kg xylazine hydrochloride or saline epidurally. No change in halothane MAC was observed following saline administration. Xylazine administration, however, significantly decreased halothane MAC from 0.93 to 0.61% in the thoracic limb and from 0.93 to 0.53% in the pelvic limb. Recovery from anaesthesia was uneventful and no adverse effect was observed. It is concluded that epidural xylazine has significant antinociceptive effect in ponies.