PROTECTION BY DIBENAMINE AGAINST “SPONTANEOUS” ARRHYTHMIAS OCCURRING DURING CYCLOPROPANE ANESTHESIA

Abstract

All concns. of cyclopropane sensitize the myocardium circulating epinephrine. It was suggested that dibenamine (N, N-dibenzyl-beta-chlorethylamine) which blocks many excitatory effects of epinephrine might protect against cardiac irregularities induced by epinephrine in the presence of cyclopropane. Pre-anesthetic medication consisting of barbiturate, morphine, and scopolamine was given to 20 healthy young adult patients undergoing elective surgery. Dibenamine, which has a very persistent action with nearly maximal effect existing from 30 min. to 18 hrs. after admn., was given 17 min. to 14 hrs. pre-operatively. Seven patients received 5-6 mg./kg. and six, 7.0-7.5 mg./kg. of dibenamine added to 50 cc. of 5% dextrose soln. in saline, intraven. over a period of 10 to 72 min. (avg. 38 min.), preceded by 0.1 or 0.2 g. of pentobarbital or seconal. Cyclopropane was administered in a closed system with CO2 absorption. Each patient was carried slowly through the planes of surgical anesthesia to respiratory arrest and back to plane 1 or 2 over a period of about 30 min. In plane 4 adequate oxygenation was maintained by intermittent pressure on the re-breathing bag, except for short periods during which the effects of superimposed hypoxia were studied. Ecg. tracings were taken, starting several min. before anesthesia and continuing for at least 30 min. during anesthesia. Arrhythmias were classified as (1) nodal or auricular rhythm, (2) ventricular beats, less than 1/3 total no. of beats, (3) ventricular beats, more than 1/3 total no. of beats, and (4) ventricular tachycardia. In the control group of 7 patients, 66% developed arrhythmias, the severity of arrhythmias encountered increased exponentially with the depth of anesthesia. In patients receiving 5-6 mg./kg. of dibenamine the incidence of arrhythmias was decreased to 35%. Of the patients receiving 7.0-7.5 mg./kg. 9% showed sinus rhythm, and 10% showed moderate rhythm disturbances in stage IV anesthesia. Short periods of hypoxia significantly increased the severity of arrhythmias in all control patients, and in those receiving 5-6 mg./kg. During operation there was no significant alteration in systolic pressure, but pulse pressure increased in patients that received dibenamine pre-operatively. Side effects of dibenamine included nausea, vomiting, and nasal congestion.