Effect of Procaine Hydrochloride on Response of the Heart to Epinephrine During Cyclopropane Anaesthesia

Abstract

Following premedication with 1 mg./kg. morphine sulfate and 0.04 mg./kg. atropine sulfate, 18 dogs were allowed to equilibrate with a mixture of cyclopropane and O2 adjusted to produce stage III, plane 3 anesthesia. Seventy-eight injns. of epinephrine were made intra-ven. In 32 cases procaine HC1 (5-15 mg./kg.) was given 5 min. before the epinephrine. Effects were observed by means of a continuously writing ink-recording ecg. The immediate effects of procaine HC1 were an increase in cardiac rate and reversion of cardiac irregularities present to regular sinus rhythms. An analysis of its subsequent effect on the reaction to epinephrine revealed no significant difference in the occurrence of ventricular fibrillation, ventricular tachycardia, or ventricular premature systoles. There was a significant increase in the number of regular sinus rhythms, and a significant decrease in the occurrence of sinus arrhythmia and in positive evidence for increase in vagal tone. A protecting action against epinephrine-induced arrhythmias could not be demonstrated for the doses of procaine HC1 investigated. Its predominant effect was an antivagal one.