Hemodynamic effects of dobutamine in patients following mitral valve replacement

Mitral valve replacement is frequently complicated by a low cardiac output syndrome and elevated pulmonary arterial pressures. In the present study, we used dobutamine to increase cardiac index and measured the pulmonary hemodynamic effects in 10 patients with increased pulmonary vascular tone following mitral valve replacement. Using increasing doses of dobutamine up to 10 μg·kg^-1·min^-1, we observed a statistically significant increase in mean cardiac index (from 2.39 ± 1.4 liters·min^-1·m^-2 to 3.52 ± .33, P < 0.01) and mean heart rate (from 71.6 ± 5.2 beats·min^-1 to 84.3 ± 8.1, P < 0.01). This was associated with stable mean systemic arterial pressures and mean pulmonary arterial pressures. Both mean systemic and pulmonary vascular resistances decreased significantly (from 1210 ± 99 dynes·sec·cm^-5 to 809 ± 90 [P < 0.01], and from 195. 9 ± 30.6 dynes·sec·cm^-5 to 129.4 ± 41.2 [P < 0.01] respectively) with dobutamine. Intrapulmonary shunt flow increased significantly in the five patients studied. Though increases in heart rate and pulmonary shunt flow may limit its use, dobutamine increases cardiac output and decreases pulmonary vascular resistance in patients with increased pulmonary arterial pressure following mitral valve replacement.