Effect of atropine dose on heart rate during electroconvulsive therapy.

Introduction: Transient bradycardia during the stimulation phase of electroconvulsive therapy (ECT) is a well-known clinical observation. The optimal dose of atropine needed to prevent bradycardia has not been determined. This study was designed to investigate the effect of low doses of atropine on heart rate during ECT.

Methods: Patients who received at least 2 different doses of atropine over their series of right unilateral ECT were included in the analysis. The anesthetic consisted of 0, 0.2, 0.3, or 0.4 mg of atropine, methohexital, and succinylcholine. Heart rate was measured by the RR interval, the time between sequential R waves on the electrocardiogram. Analysis was performed using logistic multivariate regression and repeated-measures multivariate analysis of variance.

Results: One hundred eighteen ECT sessions were identified from 19 patients. Patients were grouped into 4 groups by atropine dose (0, 0.2, 0.3, or 0.4 mg) with 9, 33, 13, and 63 ECT sessions identified for each dose, respectively. Patients who received atropine had significantly less bradycardia after electrical stimulus and a faster heart rate through the seizure than patients who did not receive atropine. There was no significant difference in heart rate between patients receiving 0.2, 0.3, and 0.4 mg of atropine at any time point. There was no significant difference in heart rate at time points after the seizure conclusion in any group of patients.

Conclusion: Low-dose atropine results in significantly less bradycardia after electrical stimulus. There was no significant difference in heart rate across low doses of atropine.