Abstract
Previous studies have showed that halothane has depressed ventricular activation in a canine myocardial infarction model. It is also well known that class I antiarryhthmic drugs depress ventricular activation in the infarcted myocardium. In the present study, we examined whether some electrophysiologic interactions between halothane and two class I antiarrhythmic drugs, lidocaine and procainamide, occur in a canine myocardial infarction model. Halothane, lidocaine and procainamide prolonged the activation time in the infarcted zone, and the combination of halothane and either lidocaine or procainamide markedly prolonged the activation time or blocked the delayed activation in the infarcted zone. Although the mechanism of the interaction is not clear, the present results suggest a synergistic interaction between halothane and class I antiarrhythmic drugs. Therefore, care should be taken that doses of class I antiarrhythmic drugs during halothane anesthesia will not be an overdose.
