Hemodynamic effects of intraaortic administration of protamine

Seventy-nine consecutive patients were given protamine rapidly into the ascending aorta during neutralization of heparin at the end of cardiopulmonary bypass. Simultaneously left atrial, diastolic pulmonary arterial, or right atrial pressures were maintained constant by appropriate infusion of oxygenated blood into the aorta. The systemic and pulmonary vascular resistances did not change, mean arterial blood pressure increased slightly, and cardiac output increased significantly (p less than 0.001). It seems that this method of heparin neutralization is safe provided that the intravascular volume can be maintained constant.