Pulmonary microvascular pressures (PMVP) have important diagnostic and therapeutic implications when utilized to monitor pulmonary dysfunction after cardiopulmonary bypass. Elevations in PMVP may lead to interstitial pulmonary edema and right ventricular failure. This study evaluated the influence of Dobutamine on PMVP in a trial of 80 consecutive patients undergoing isolated coronary artery bypass grafting (CABG). Forty patients were randomized to the Dobutamine study group and received 5 micrograms/kg/min of Dobutamine for 24 hours, starting at the completion of bypass. In the control group, patients received postoperative inotropic support as indicated (dopamine [n = 10] or amrinone [n = 6]) by the clinical situation. PMVP values were computed based on continuous hemodynamic monitoring at 6, 12, 18 and 24 hours. Preoperative demographic descriptors and operative variables were comparable between the two groups. Postoperative fluid requirements and nonpulmonary complications were also similar between groups. Upon completion of cardiopulmonary bypass, PMVP (mean +/- SD) were PMVP decreased over time in the Dobutamine group, while it did not change in the control group. Clinically mean time to extubation was reduced from 18 to 12 hours (p < 0.06) in the Dobutamine group. We conclude that in patients undergoing cardiopulmonary bypass, the postoperative administration of Dobutamine significantly reduces the PMVP. This may reduce pulmonary interstitial edema and pulmonary complications. Upon completion of cardiopulmonary bypass, PMVP (mean +/- SD) were measured at 6 hours, 12 hours, 18 hours and 24 hours. The control group measured 25 +/- 5 mmHg, 26 +/- 2 mmHg, 27 +/- 3 mmHg and 28 +/- 3 mmHg. The Dobutamine group measured 25 +/- 6 mmHg, 24 +/- 3 mmHg, 22 +/- 2 mmHg and 18 +/- 5 mmHg. PMVP decreased over time in the Dobutamine group (p < 0.001), while it did not change in the control group. Clinically mean time to extubation was reduced from 18 to 12 hours (p < 0.06) in the Dobutamine group. We conclude that in patients undergoing cardiopulmonary bypass, the post-operative administration of Dobutamine significantly reduced PMVP. This may reduce pulmonary interstitial edema and pulmonary complications post cardiopulmonary bypass.