Milrinone can improve myocardial systolic function and hemodynamics by increasing contractility and decreasing afterload, although its appropriate dose regimen has not yet been established for cardiac surgical patients. Despite milrinone effectively increases cardiac function after cardiopulmonary bypass, few studies have specifically evaluated its efficacy during cardiac surgery. We investigated the effects of milrinone on hemodynamics and left systolic ventricular function in cardiac surgical patients immediately after emergence from cardiopulmonary bypass (CPB). Forty five patients undergoing cardiac surgery were studied. They received milrinone (25, 50, or 75 ug/kg) bolus dose over ten minutes followed by 0.25, 0.5, 0.75 ug/kg/min in three patients groups. Heart rate, mean arterial blood pressure, pulmonary capillary wedge pressure, and cardiac index were determined before and after the administration of milrinone and transesophageal echocardiogram were recorded while constant filling pressures were maintained by volume reinfusion from the CPB reservoir. All three doses of milrinone significantly increased CI ( 2.5, 3.1,3.2 L/min/m