Influence of imipramine and pargyline on the arrhythmogenicity of epinephrine during halothane, enflurane or methoxyflurane anesthesia in dogs

Abstract

Each group of six male mongrel dogs was treated with oral pargyline, 100 mg/day, or imipramine, 25 mg/day, for at least 8 days. During continued drug treatment each animal was studied 3 times between day 8–14 and was anesthetized by 1.2 MAC (minimal elveolar concentration) halothane, enflurane or methoxyflurane with 50% N 2OO 2, but only one of the anesthetic regimens was administered during each study. Lead II of the ECG, esophageal temperature and femerol arterial pressure were monitored continuously during controlled ventilation, maintaining normocarbia. Epinephrine was infused at the rate of 1 ug/kg/min until the occurence of three or more consecutive PVC's (premature ventricular contractions) as the end point of the arrhythmia threshold dose. The latter is significantly lower in the imipramine pretreated group in comparison with the pargyline pretreated and the control groups. The results also suggest that methoxyflurane and enflurane may be less harmful to the myocardium than halothane during epinephrine-induced arrhythmias.