The effect of milrinone on metabolism after cardiopulmonary bypass

The aim of this study was to examine the effects of milrinone on tissue metabolism perioperatively in cardiac surgery patients using extracorporeal circulation, in comparison to adrenaline and placebo. These effects were measured indirectly by measuring serum lactate, base excess and glucose levels at standard intervals.

Seventy-seven consecutive patients, who underwent elective cardiac surgery, were allocated in 3 groups. Inotropic support was initiated coming off CPB (cardiopulmonary bypass) if there was evidence of hypotension (mean arterial pressure [MAP] <60 mmHg), after adequate preload (pulmonary capillary wedge pressure [PCWP] >10 mmHg). Milrinone was used in patients with pulmonary hypertension (MPAP >20 mmHg). Group 1 (N.=26) received no inotropes, placebo. Group 2 (N.=32) received adrenaline. Group 3 (N.=19) received adrenaline + milrinone at 0.5 microg/kg/min infusion. Adrenaline was infused at a variable dose (0.01-0.02 microg/kg/min) to achieve a MAP >60 mmHg. The serum lactate, base excess and glucose levels were measured at standard intervals in all 3 groups. Diabetic, hepatic or renal failure patients (serum creatinine >2 mg/dL), were excluded from the study. Patient demographic and clinical characteristics were similar in all 3 groups.

Repeated measure analysis of variance between groups showed significantly lower serum lactate levels and higher base excess in the milrinone group (P<0.05), after 2 to 4 hours of treatment. Serum glucose levels were higher in the adrenaline group (P=0.01). There were no immediate complications, morbidity or mortality in the study groups.

These findings suggest that milrinone has a beneficiary effect on aerobic tissue metabolism after extracorporeal circulation, reflected on serum lactate, base excess and glucose levels, possibly due to a combination of positive inotropic and peripheral vasodilatory effect of the drug.