Sotalol is a beta-adrenergic blocking drug with the additional property of lengthening the cardiac action potential. These electrophysiologic properties render the drug attractive for use in the prevention of postoperative supraventricular arrhythmias (SVA), and previous studies have suggested that it was indeed effective. The hemodynamic response to sotalol and its safety early after coronary artery bypass graft (CABG) surgery were therefore studied. Forty-two patients undergoing CABG were randomly assigned either to receive sotalol to prevent postoperative SVA (25 patients) or to serve as controls (17 patients). Sotalol was started 6 hours after surgery if patients had a cardiac index > 2.8 L/min/m2 with a pulmonary capillary wedge pressure < 15 mmHg, and if they had no contraindications to the use of beta-blockers. The drug was given as a loading infusion of 1 mg/kg over 2 hours, followed by a maintenance infusion of 0.15 mg/kg/h for 24 hours. Three hours later, patients received the first oral dose of 80 mg to be repeated every 8 or 12 hours. Adverse effects necessitating discontinuation of the drug (bradycardia < 50 beats/min, systolic blood pressure < 90 mmHg, or cardiac index < 2.2 L/min/m2) occurred in six patients (24%) and were mainly related to the loading infusion. The hemodynamic data for patients who completed the study were characterized by a significant fall of the cardiac index caused by a lower heart rate without significant change of the stroke volume index. The incidence of supraventricular arrhythmias was not significantly different in the two groups (3/19 in the sotalol group, 5/17 in the control group).(ABSTRACT TRUNCATED AT 250 WORDS)