ABSTRACT
Milrinone can improve myocardial systolic function and hemodynamics by increasing contractility and decreasing afterload, although its appropriate dose regimen has not yet been established for cardiac surgical patients. Despite milrinone effectively increases cardiac function after cardiopulmonary bypass, few studies have specifically evaluated its efficacy during cardiac surgery. We investigated the effects of milrinone on hemodynamics and left systolic ventricular function in cardiac surgical patients immediately after emergence from cardiopulmonary bypass [CPB]. Forty five patients undergoing cardiac surgery were studied. They received milrinone [25, 50, or 75 ug/kg] bolus dose over ten minutes followed by 0.25, 0.5, 0.75 ug/kg/min in three patients groups. Heart rate, mean arterial blood pressure, pulmonary capillary wedge pressure, and cardiac index were determined before and after the administration of milrinone and transesophageal echocardiogram were recorded while constant filling pressures were maintained by volume reinfusion from the CPB reservoir. All three doses of milrinone significantly increased CI [2.5, 3.1,3.2 L/min/m2], HR [98, 96,100 bpm], SV [61,66,67 ml/beat] and EF [61, 66, 66%] after 5 min from the milrinone use [p<0.001] and significantly decreased the MAP [80, 81, 82 mmHg], SVR [1127, 965, 928 dyn.s.cm-5] and PVR [183, 165, 157 dyn.s.cm-5] at the same time interval [p<0.001] while the PCWP and CVP did not show valuable change. The 50- and 75-ug/kg doses produced significantly larger increases in cardiac index than the 25-ug/kg dose; however, the 75 ug/kg dose did not produce a significantly larger increase in cardiac index than did the 50-ug/kg dose. Two patients receiving milrinone 25 ug/kg developed premature ventricular contractions. The 75-ug/kg dose was associated with a case of ventricular tachycardia treated with xylocaine infusion and three cases of severe hypotension [BP <60 mmHg] requiring phenylephrine infusion and IV fluid replacement. Thus, milrinone improves hemodynamics and left ventricular systolic function when constant loading conditions are maintained