COMPARISON OF 2 DIFFERENT LOADING DOSES OF MILRINONE FOR WEANING FROMCARDIOPULMONARY BYPASS

Objective: To compare the hemodynamic effects, pharmacokinetic profile s, and the need for vasoactive agents between a low (20 mu g/kg during 15 minutes [group 1; n = 10]) and a high (40 mu g/kg during 15 minute s [group 2; n = 10]) loading dose of milrinone. Design: Prospective, r andomized, double-blind. Setting: University hospital. Participants: T wenty patients scheduled for elective coronary artery surgery. Interve ntions: Weaning from CPB was achieved using a strict protocol. After a trioventricular pacing at 90 beats per minute and preload optimalizati on, a first weaning attempt was started with only calcium and nitrogly cerin as support. If this attempt was unsuccessful (cardiac index < 2L /min/m(2)), CPB was reinitiated and weaning level 2 was prepared, cons isting of inotropic support with milrinone. Patients received either t he low (group 1) or the high (group 2) loading dose of milrinone. Afte r the end of the loading dose, a continuous infusion of milrinone of 0 .5 mu g/kg/min was started in both groups. Measurements and Main Resul ts: Both groups were comparable regarding preoperative and intraoperat ive data. Hemodynamic data were comparable in both groups at each time of measurement (p = 0.941). The need for vasoactive medication (norep inephrine [NE]) in order to keep mean arterial pressure greater than o r equal to 50 mm Hg was significantly higher in group 2 (p = 0.004). N eed for NE during the loading infusion was 9.6 +/- 4.9 mu g (mean +/- SEM) in group 1 and 41.6 +/- 7.6 mu g in group 2 (p = 0.004). Need for NE during the immediate post-CPB period was also higher in group 2 (1 6.0 +/- 10.4 mu g in group 1 and 232.5 +/- 82.8 mu g in group 2 in = 0 .002)). Plasma clearance of milrinone after CPB was less in both group s than in healthy volunteers. However, clearance of milrinone was sign ificantly higher in group 2 (p = 0.006), and consequently, half-life o f milrinone was significantly less in group 2 (p = 0.007). Conclusions : The present results demonstrate that when milrinone is used during w eaning from CPB, a loading dose of 20 mu g/kg provided to similar hemo dynamic support a loading dose of 40 mu g/kg. The need for vasoconstri ctive medication was significantly less in the group with the low load ing bose. Copyright (C) 1995 by W.B. Saunders Company