[Influence of milrinone on internal mammary artery grafts]

To evaluate the effects of milrinone on blood flow in the left internal mammary artery (LIMA) grafts and hemodynamic variables, we conducted a prospective randomized study. Twenty-four patients undergoing coronary artery bypass grafting were randomized to receive milrinone treatment (Milrinone; n = 12) or no milrinone treatment (Control; n = 12). Milrinone was given after induction of anesthesia at a speed of 0.5 microgram/kg/min for 24 hours. After start of cardiopulmonary bypass (CPB), CPB perfusion flow was adjusted to 2.4 l/m2 and LIMA blood flow was measured. Blood samples for determination of plasma cAMP levels were collected and hemodynamic measurements were also assessed perioperatively. LIMA blood flow was significantly greater in Milrinone than that in Control (40 +/- 4 vs 29 +/- 4 ml/min/m2, p < 0.05). Plasma levels of cAMP were significantly (p < 0.05) greater in Milrinone than those in Control at tha start of CPB (18 +/- 1 vs 13 +/- 1 pmol/ml) and at the end of CPB (24 +/- 2 vs 17 +/- 2 pmol/ml). Systemic vascular resistance was significantly (p < 0.05) lower and cardiac index was significantly (p < 0.05) greater in Milrinone than those in Control postoperatively. With its positive inotropic and systemic vasodilator activities, milrinone may have direct vasodilator effect on LIMA.