COMPARISON OF THE EFFECTS OF HALOTHANE, ISOFLURANE, AND SEVOFLURANE ON ATRIOVENTRICULAR-CONDUCTION TIMES IN PENTOBARBITAL-ANESTHETIZED DOGS

It is not known how sevoflurane affects the cardiac conduction system. We compared the effects of halothane, isoflurane, and sevoflurane on specialized atrioventricular (AV) conduction times in eight pentobarbi tal-anesthetized dogs. AV conduction times with three inhaled anesthet ics at end-tidal concentrations of 1 and 2 minimum alveolar anesthetic concentration (MAC), were measured by His-bundle electrocardiography during both sinus rhythm and right atrial pacing at a slightly higher rate than sinus one. Heart rate and arterial pressure were simultaneou sly recorded. Halothane prolonged AV nodal conduction time during sinu s rhythm (A-H interval) at 2 MAC compared with the control value, wher eas isoflurane and sevoflurane did not alter the A-H interval, His-Pur kinje conduction time (H-V interval), and ventricular conduction time (H-S interval) during sinus rhythm at 1 and 2 MAC. All three inhaled a nesthetics did not change AV conduction times during right atrial paci ng. No significant difference in AV conduction times was observed betw een isoflurane and sevoflurane. Heart rate during sinus rhythm remaine d unchanged despite a decrease in arterial pressure with three inhaled anesthetics. The property of sevoflurane and isoflurane which does no t affect the cardiac conduction system may be important in the stabili ty of the cardiac rhythm during anesthesia with these drugs.