Minimal anesthetic concentration and cardiopulmonary dose-response of halothane in ducks.

The minimal anesthetic concentration (MAC) for halothane and cardiopulmonary dose-responses at several concentrations of halothane were determined during spontaneous ventilation in nine young adult Pekin ducks. The MAC for halothane was 1.04 +/- 0.11 (mean +/- SD). There were dose-dependent decreases in ventilation, significant reductions in inspiratory and expiratory times, and prolongation of expiratory pause times. The end-tidal halothane concentration at apnea in five ducks was less than 1.53% and anesthetic index was less than 1.51. Heart rate increased significantly as the concentration of halothane was increased, but arterial blood pressure did not change. Cardiac arrhythmias developed in five ducks at end-tidal halothane concentrations as low as 1.15%, and one duck died of cardiac arrest.