THE EFFECT OF INTRAVENOUS PROCAINE ON THE HEART

Abstract

The effects are described of rapid injns. of 2 or 4% soln. of procaine hydro-chloride in doses from 4 mg./kg. to 80 mg./kg. in 20 dogs. With doses of 4 mg./kg. there was usually no change in ecg., heart sounds or blood pressure. Progressive changes occurred as the amt. of procaine was increased. Ecg. changes consisted of a heightening, sometimes a flattening or even an inversion of the T wave; lowering of the voltage of R, increase in the depth of the S wave and depression of the S-T segment; increase in the width of the QRS complex; prolongation of the P-R interval; ventricular tachycardia, and, ultimately, ventricular fibrillation. All changes except ventricular fibrillation were reversible, provided that respiration was maintained. Blood and pulse pressures dropped as the QRS complex widened. The greatly dilated heart at necropsy and the flabby condition of the muscle speak for an effect of procaine on the cardiac musculature. Small doses (4 to 10 mg./kg.) caused an increase in respiratory rate which was independent of any change in blood pressure; larger doses (20 mg./kg. or more) first increased, then decreased the respiratory rate. With doses of 40 mg./kg. or more, respiration usually ceased within 30 sec. of the injn. If sudden collapse occurs during the use of procaine, immediate institution of artificial respiration might mean a fair chance of recovery, provided that ventricular fibrillation has not occurred.