Hemodynamic effects of milrinone during weaning from cardiopulmonary bypass: Comparison of patients with a low and high prebypass cardiac index

Objective: To compare the hemodynamic effects of milrinone during weaning from cardiopulmonary bypass (CPB) in patients with a low pre-CPB cardiac index (CI) <2.5 L/min/m²) and in patients with a high pre-CPB CI (≥2.5 L/min/m²). Design: Prospective, randomized, double-blind study. Setting: University hospital. Participants: Forty-eight patients scheduled for elective coronary artery bypass graft surgery. Intervention: Patients were divided into 4 groups: (1) low pre-CPB CI/placebo, (2) low pre-CPB CI/milrinone, (3) high pre-CPB CI/placebo, and (4) high pre-CPB CI/milrinone. Patients received a loading dose of 20 μg/kg of milrinone followed by an infusion of 0.2 μg/kg/min or placebo 15 minutes before the anticipated weaning time. Measurements and Main Results: In the low pre-CPB CI/placebo group, low CIs and high systemic vascular resistances (SVRs) were observed after CPB. High doses of dopamine and dobutamine were needed, and infusion of epinephrine was used in 5 of the 12 patients for hemodynamic support. Milrinone improved CI and reduced SVR in the low pre-CPB CI/milrinone group. Norepinephrine was needed to maintain an adequate systemic blood pressure in 6 of the 12 patients, however. In the high pre-CPB CI/placebo group, satisfactory CIs and SVRs were observed during weaning from CPB with low doses of dopamine and dobutamine. Milrinone significantly increased CI and decreased SVR in the high pre-CPB CI/milrinone group: 10 of the 12 patients had CIs above the upper limit of normal, and 7 patients had SVRs below the lower limit of normal. Conclusion: Milrinone was effective during weaning from CPB in patients with a low pre-CPB CI. Milrinone in combination with norepinephrine was a good alternative to epinephrine for the treatment of myocardial dysfunction after CPB. Copyright (C) 2000 by W.B. Saunders Company.