Cardiovascular responses to verapamil during coronary artery bypass graft surgery

The cardiovascular effects of verapamil administration during coronary artery bypass graft surgery were studied in patients with normal left ventricular function. Anesthesia consisted of morphine, diazepam, and nitrous oxide. Before atrial cannulation for cardiopulmonary bypass, 16 patients received either verapamil (N = 8) 0.075 mg X kg-1 or an equal volume of its solvent (N = 8) administered intravenous over 1 min. Hemodynamic functions and serum verapamil levels were measured over the succeeding 10 min. Verapamil produced rapid reductions in systemic vascular resistance, systemic arterial blood pressure, and left ventricular stroke work index. The PR interval increased slightly and two of the patients who had a baseline PR interval of 200 msec developed a mild first degree heart block. Heart rate, cardiac index, pulmonary capillary wedge pressure, central venous pressure, and right ventricular stroke work index did not significantly change. No measured cardiovascular functions changed in the control group. Serum verapamil levels peaked at 346.4 +/- 143.5 ng X ml-1 0.5 min after drug administration and then rapidly declined. Both groups of patients tolerated surgery and the immediate postoperative recovery period without hemodynamic compromise. Verapamil can be safely administered before cardiopulmonary bypass in patient with good left ventricular function during narcotic-based anesthesia.