Systemic and pulmonary effects of nitroprusside during mitral valve replacement in patients with mitral regurgitation.

The effects of sodium nitroprusside on the systemic and pulmonary circulation were assessed in 17 patients with severe mitral regurgitation (MR) during mitral valve replacement. In nine patients, MR was related to rheumatic heart disease, in six resulted from acute myocardial infarction, and in two was due to subacute bacterial endocarditis. Nitroprusside was administered intraoperatively at an infusion rate of 10 to 65 mcg/min. During vasodilation therapy, forward stroke volume increased from 34 +/- 2.8 to 46 +/- 4.8 ml, while left ventricular filling pressure decreased from 28.7 +/- 1.9 to 20.6 < or = 1.8 mm Hg. There was a significant decrease in systemic vascular resistance (from 2379 +/- 204 to 1646 +/- 161 dynes.sec.cm-5) and mean arterial pressure (from 89.8 +/- 4 to 78.1 +/- 5 mm Hg). Similarly, a significant decrease was observed in both pulmonary vascular resistance (from 414 +/- 45 to 208 +/- 31 dynes.sec.cm-5) and mean pulmonary arterial pressure (from 42.5 +/- 2.5 to 29.7 +/- 2.5 mm Hg) with nitroprusside. In all patients there was a decrease in the magnitude of the peak V wave of the pulmonary capillary wedge pressure (from 45.2 +/- 3.9 to 26.1 +/- 3.1 mm Hg). These findings suggest that judicious intraoperative administration of nitroprusside improves right and left ventricular function in patients with MR undergoing mitral valve replacement, by increasing forward stroke volume while decreasing ventricular filling pressures and vascular resistance (preload and afterload).