Intravenous milrinone following cardiac surgery: II. Influence of baseline hemodynamics and patient factors on therapeutic response. The European Milrinone Multicentre Trial Group.

Further analysis of the data from 99 adult patients who received an intravenous infusion of milrinone following elective cardiac surgery was done. All patients received a bolus infusion of 50 micrograms/kg over 10 minutes, followed by a maintenance infusion of either 0.375, 0.5 or 0.75 microgram/kg/min for a period of 12 hours. Hemodynamic measurements were made after the bolus infusion (15 minutes), and then after 30, 45, and 60 minutes at 3, 6, and 12 hours, and 4 hours after treatment was stopped. The following was found: (1) pretreatment cardiac index (CI) affected the response to treatment. Patients with a low CI (1.59 L/min/m2) had a 54% increase after the bolus infusion compared to a 27% increase in patients with a higher pretreatment value (2.2 L/min/m2) (P < 0.05); (2) patients with a high resting level of pulmonary vascular resistance (PVR > 200 dynes.sec.cm-5) had a greater response to treatment (26% fall in PVR) than the remainder (9% fall in PVR) after 60 minutes; (3) patients with a low pretreatment mean arterial pressure (MAP) (n = 17, MAP 64 mmMg, range, 52 to 70) showed no fall in MAP following treatment, but showed a significant increase in CI (+55%). A good therapeutic response was found that was similar in patients undergoing valve replacement surgery or coronary artery bypass graft surgery, and in patients in sinus rhythm or atrial fibrillation before treatment. It is concluded that the therapeutic response to intravenous milrinone following cardiac surgery is partially determined by pretreatment hemodynamics.