Milrinone increases middle cerebral artery blood flow velocity after cardiopulmonary bypass

Objective: To evaluate the effects of milrinone on middle cerebral artery blood flow velocity (Vmca) and pulsatility index (PI) during normocapnia and hyperventilation in adults after cardiopulmonary bypass (CPB). Design: A prospective study. Setting: University-affiliated hospital and Veterans Affairs Medical Center. Participants: Twenty-five adults with left ventricular ejection fraction >40% undergoing coronary artery bypass graft surgery. Interventions: After separation from CPB, using transcranial Doppler ultrasonography, peak and mean Vmca and PI were recorded before and after the administration of 50 mug/kg of milrinone under normocapnia and with hyperventilation. Measurements and Main Results: Heart rate, arterial blood pressure, central venous pressure, and cardiac output were documented after each study period. Compared with base-line, milrinone increased peak Vmca by 20%, increased mean Vmca by 19%, and decreased PI by 16% (p < 0.001). Before the administration of milrinone, hyperventilation decreased peak Vmca by 20%, decreased mean Vmca by 26%, and increased PI by 24% (p < 0.01). After milrinone administration, hyperventilation also decreased peak Vmca by 22%, decreased mean Vmca by 21%, and increased PI by 19% (p < 0.01). Milrinone increased cardiac index and decreased mean arterial pressure and systemic vascular resistance (p < 0.05); however, heart rate and central venous pressure remained unchanged. Conclusion: The administration of milrinone increases cerebral blood flow after CPB most likely as a result of cerebral vasodilation. The response to hyperventilation seems to be partially preserved. Copyright 2002, Elsevier Science (USA). All rights reserved.