Sodium Nitroprusside Therapy for Cardiac Failure in Anesthetized Patients with Valvular Insufficiency

Abstract

Cardiac function was evaluated in 17 patients with cardiac valvular insufficiency scheduled for valve replacement immediately prior to the induction of anesthesia, during stable anesthetic and surgical conditions after the chest was opened, and during a constant sodium nitroprusside infusion about 15 min later but prior to cannulation for cardiopulmonary bypass. Preoperative awake hemodynamic measurements indicated that these patients were in a state of compensatory cardiac failure with a low cardiac index of 2.20 .+-. 0.15 l/min per m2 and a high systemic vascular resistance of 1560 .+-. 150 dyn .cntdot. s .cntdot. cm-5. Pulmonary capillary wedge pressure was 13 .+-. 3 torr, central venous pressure 4 .+-. 1 torr, and stroke volume index was 29.6 .+-. 2.1 ml/beat per m2. During steady-state anesthesia with the operation in progress, there were significant increases in systemic vascular resistance to 2370 .+-. 160 dyn .cntdot. s .cntdot. cm-5 and pulmonary capillary wedge pressure to 24 .+-. 2 torr and significant decreases in cardiac index to 1.63 .+-. 0.08 l/min per m2 and stroke volume index to 19.4 .+-. 1.3 ml/beat per m2, demonstrating cardiac decompensation. An infusion of sodium nitroprusside, 20-96 .mu.g/min, produced significant decreases in systemic vascular resistance to 1490 .+-. 130 dyn .cntdot. s .cntdot. cm-5 and pulmonary capillary wedge pressure to 16 .+-. 2 torr. Cardiac index increased to 2.21 .+-. 0.15 l/min per m2 and stroke volume index to 24.4 .+-. 1.9 ml/beat per m2. Patients in compensated cardiac failure secondary to valvular insufficiency respond to anesthesia and operation with a marked deterioration in cardiac function primarily due to a further increase of the already high systemic vascular resistance. Sodium nitroprusside, by decreasing vascular tone and ventricular afterload, reverses some of the cardiovascular depression and failure in these patients, mitigating the deleterious effects of anesthesia and operation.