A COMPARISON OF THE HEMODYNAMIC-EFFECTS OF AMRINONE AND SODIUM-NITROPRUSSIDE IN INFANTS AFTER CARDIAC-SURGERY

The phosphodiesterase inhibitor amrinone (AMR) increases cardiac outpu t in children after cardiac surgery. In vitro, amrinone has both posit ive inotropic and vasodilatory effects. However the relative contribut ion of these effects to the increases in cardiac output observed clini cally is unclear, and it has not been demonstrated that amrinone offer s a hemodynamic advantage above that of pure vasodilators in infants. We compared the hemodynamic effects of AMR and sodium nitroprusside (S NP) in 10 infants after cardiac surgery. Cardiac index (CI) was measur ed by thermodilution after SNP administration, titrated to decrease me an blood pressure (MBP) by 20%, and then after a 1.5-mg/kg bolus dose of AMR. Each patient served as his or her own control. Preload, as mea sured by left atrial pressure and transesophageal echocardiography (in eight patients), was kept constant throughout the protocol. Both SNP and AMR caused significant decreases in MBP and systemic vascular resi stance index (SVRI). However, only AMR resulted in a significant incre ase in CI. The ratio of fractional increase in CI to fractional absolu te decrease in MBP was significantly greater for AMR than SNP, indicat ing greater efficacy for AMR in the treatment of low cardiac output sy ndrome and suggesting that, in infants after cardiac surgery, AMR has clinically relevant positive inotropic effects.