The hemodynamic and oxygen transport effects of low-dose (0.75 mg/kg loading dose + 10 μg/kg/min infusion, n = 12) and high-dose (2.25 mg/kg loading dose + 20 μg/kg/min infusion, n = 12) amrinone were evaluated in extubated patients 24 h after CABG. At both doses, amrinone significantly (p<0.05) increased HR, but decreased mean arterial, mean pulmonary artery, central venous and pulmonary artery occlusion pressures. High-dose amrinone significantly decreased systemic vascular resistance. Arterial oxygen saturation decreased significantly following both low- (97.8±0.4 to 95.6±0.9 percent) and high- (98.8±3.4 to 93.9±1.2 percent) dose amrinone. Pulmonary shunt increased significantly following low-dose amrinone and markedly increased Qs/Qt after high-dose amrinone. Although amrinone significantly increased cardiac index in a dose-dependent fashion (low:3.0±0.2 to 3.3±0.3 L/min/m2; high:2.7±0.2 to 3.4±0.2 L/min/m2), mixed venous oxygen saturation did not change. Thus, mixed venous oxygen saturation may not predict the hemodynamic response to amrinone infusion in postoperative surgical patients.