Effects of milrinone versus epinephrine on grafted internal mammary arteryflow after cardiopulmonary bypass

Objective: To compare changes on grafted internal mammary artery (IMA) flow after cardiopulmonary bypass in response to the administration of milrinon e or epinephrine. Design: Prospective and randomized. Setting: University-affiliated hospital. Participants: Twenty consenting, adult patients undergoing CABG. Interventions: Patients were randomized to receive either milrinone, 50 mu g/kg, or epinephrine, 0.03 mu g/kg/min, immediately after cardiopulmonary b ypass. IMA flow was measured with a laser Doppler flow probe before and aft er the administration of either drug. Measurements and Main Results: Baseline grafted IMA flow was similar for bo th groups (milrinone, 38 +/- 14 mL/min; epinephrine, 33 +/- 10 mL/min). In patients who received milrinone, flow increased by 24% to 50 +/- 17 mL/min, p < 0.05; whereas with epinephrine, it remained essentially unchanged (33 +/- 10 v 31 +/- 11 mL/min). Conclusions: This study confirms that the vasodilatory effect of milrinone on the IMA is also present after its anastomosis, whereas low-dose epinephr ine exhibits neither beneficial nor adverse effects. It is suggested that i n the absence of excessive vasodilation, milrinone should be considered as a first-line inotrope after coronary artery bypass graft surgery, to achiev e an increase in contractility and IMA artery flow. Copyright (C) 2000 by W .B. Saunders Company.