Specific afterload reduction with parenteral hydralazine following cardiac surgery.

In a group of seven patients who had had cardiac operations, intravenous (IV) hydralazine was used to provide afterload reduction in situations of severe left ventricular dysfunction. Despite fluid loading, inotropic support with dopamine, and afterload reduction with sodium nitroprusside, the patients had persistent states of low cardiac output and high systemic vascular resistance. Administration of sodium nitroprusside was limited by its effect on preload and blood pressure, so that it necessitated frequent fluid challenges. The addition of IV hydralazine to this regimen caused a mean increase of 44.7% in the stroke index and a mean reduction of 28.6% in systemic vascular resistance without significant change in pulmonary artery wedge pressure, mean arterial pressure, or heart rate. Rapid weaning of sodium nitroprusside and, on occasion, dopamine was facilitated. Frequent fluid challenges to restore preload were unnecessary. Dose requirements of hydralazine were small: 2.5 to 5.0 mg IV initially, and then a maintenance dose of 2.5 to 7.5 mg IV every 4 to 6 hours. These preliminary clinical observations indicate that in patients with low cardiac output--high resistance states and normal or elevated preload, the important benefit of specific afterload reduction may be provided by parenteral hydrolazine in the early period following cardiac surgery. Prospective, controlled studies with this agent in this situation appear warranted.