The combined effect of ephedrine and atropine on complete heart-block

Abstract 1. 1. Two cases of complete heart-block responded to ephedrine quite differently. (a) With a small dose of ephedrine, Case 1 showed practically no change in auricular or ventricular rate, but a moderate elevation of blood pressure. In Case 2 there was an increase of auricular rate, but practically no change in ventricular rate or blood pressure. (b) With a large dose of ephedrine Case 1 showed an increase of auricular and ventricular rate and a marked elevation of blood pressure. The ventricular complexes varied and there were frequent ventricular extrasystoles. In Case 2 there was a decrease in auricular rate while the ventricular rate remained constant. There was practically no pressor response, and no change in the electrocardiograms. 2. 2. In instances in which slowing of the auricles occurred without any appreciable elevation of blood pressure, the slowing may be ascribed to the stimulating effect of ephedrine on the parasympathetic nerves. 3. 3. When an effective dose of atropine was administered to an ephedrinized patient with complete heart-block, a marked increase of auricular rate and a slight elevation of ventricular rate with a marked elevation of blood pressure and increase of pulse pressure occurred. This action of ephedrine in combination with atropine suggests that atropine neutralizes the parasympathetic effect that results either from the individual's vagotony or from the stimulating effect of ephedrine on the parasympathetic nerves. 4. 4. Atropine hastened and intensified the pressor effect of ephedrine but shortened its duration, and abolished the depressor reflex effect of high blood pressure on the auricular rate. 5. 5. No corresponding effect was noticed when atropine was combined with pseudoephedrine. 6. 6. Ephedrine and ephedrine in combination with atropine did not abolish the complete block.