Canadian Journal of Anesthesia, Vol 23, 92-98, Copyright © 1976 by Canadian Anesthesiologists' Society

The Effects of Atropine on the Heart Rate

¹ Department of Anesthesia, The Southern Illinois Clinic, Ltd., 1 Doctors' Park Road, Mount Vernon, Ill. 62864

The cardiac-accelerating effects of 0.6 mgm of atropine administered intravenously were tested in 111 patients (three groups of 37 patients each). The patients in Group "A" received pentobarbitone and diphenhydramine orally before the atropine injection; those in Group "B" received no medications and those in Group "C" received pentobarbitone orally and meperidine intramuscularly. For the purpose of greater precision the time elapsed between ten consecutive electrical systoles was taken as the measure of the heart rate. Measurements were carried out before and two minutes after atropine injection.

The control mean heart rate was slower in Group "C" and faster in Group "A". Atropine increased the heart rate of all patients, most of those in Group "C" and least of those in Group "A" and in such a manner that, after atropine, the means for the three groups were nearly identical.

There is very poor correlation between the weight-adjusted dose and the cardiac accelerating effects of 0.6 mg atropine administered intravenously. The highest correlation coefficient (0.680) is found between the heart rate before and after atropine; i.e., the slower hearts are those that accelerated the most and the fastest hearts accelerated the least, irrespective of weight-adjusted dose or concomitant premedication routine.