Effects of milrinone versus epinephrine on grafted internal mammary artery flow after cardiopulmonary bypass.

OBJECTIVE

To compare changes on grafted internal mammary artery (IMA) flow after cardiopulmonary bypass in response to the administration of milrinone 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 microg/kg, or epinephrine, 0.03 microg/kg/min, immediately after cardiopulmonary bypass. IMA flow was measured with a laser Doppler flow probe before and after the administration of either drug.

MEASUREMENTS AND MAIN RESULTS

Baseline grafted IMA flow was similar for both 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 epinephrine exhibits neither beneficial nor adverse effects. It is suggested that in the absence of excessive vasodilation, milrinone should be considered as a first-line inotrope after coronary artery bypass graft surgery, to achieve an increase in contractility and IMA artery flow.