BACKGROUND: Electroconvulsive therapy (ECT) that works by electrically inducing grand mal seizure is an effective therapy for patients with major psychosis and affective disorders. But ECT may produce intense stimulation of the central nervous system resulting in hypertension and tachycardia. Such an acute hyperdynamic state may be undesirable because of possible cardiovascular complications. We compared the ability of different bolus doses of esmolol to blunt the hemodynamic effects of ECT. METHODS: Twenty ASA physical status 1~2 patients were enrolled in a crossover design study to determine the effects of two standard esmolol bolus doses (0.5 mg/kg and 1.0 mg/kg) on the hemodynamic response and seizure duration during ECT. In each patients receiving esmolol or placebo, arterial pressure, heart rate, seizure duration and peripheral oxygen saturation (SpO2) were recorded. RESULTS: The seizure duration with placebo was 43 +/- 9 sec, esmolol 0.5 mg/kg bolus dose was 39 +/- 14 sec and esmolol 1.0 mg/kg bolus dose was 39 +/- 12 sec, but it was not significant. Compared with esmolol 0.5 mg/kg bolus dose, esmolol 1.0 mg/kg bolus dose decreased blood pressure and heart rate during ECT more effectively. CONCLUSIONS: Esmolol 1.0 mg/kg bolus dose was considered to be the better dose in blunting the hyperdynamic response during ECT without shortening of seizure duration.