We compared the relative effects of dobutamine (5 μg/kg/min) and amrinone (1.0 mg/kg bolus followed by 10 μg/kg/min) on right and left ventricular function and pulmonary arterial pressures during weaning from cardiopulmonary bypass in patients with a mean preoperative pulmonary pressure >30 mmHg. Twenty patients scheduled for mitral valve replacement were studied in a prospective, randomized, double-blind trial. Patients receiving amrinone had a greater increase in cardiac index (CI) of 1.38 (±0.95) litre/min/m2 at separation vs 0.69 (±0.63) litre/min/m2 in the dobutamine group (P<0.05). The amrinone group also had a greater increase in right ventricular ejection fraction (0.15±0.08 at separation from cardiopulmonary bypass versus an increase of 0.04 ±0.11 in those receiving dobutamine; P<0.005). Amrinone produced a larger decrease in pulmonary artery wedge pressure 8.0 (±4.4) mmHg vs 0.75 (±6.6) mmHg at separation; pulmonary artery systolic and diastolic pressures also were reduced more in the amrinone group. There were no differences in heart rate, mean arterial pressure, central venous pressure and right ventricular stroke work index between patient groups. In the doses chosen, the use of amrinone compared to dobutamine was associated with a reduction in pulmonary arterial pressures and an increase in cardiac index and right ventricular ejection fraction after separation from bypass in patients with severe preoperative pulmonary hypertension.
Right ventricular ejection fraction is better reflected by transverse rather than longitudinal wall motion in pulmonary hypertension