Regional blood flow and neurohormonal responses to milrinone in congestive heart failure

We measured systemic hemodynamics, regional blood flow, and neurohormonal parameters in 13 patients with severe chronic congestive heart failure before and after 1 month of therapy with oral milrinone, a bipyridine cardiotonic agent. After milrinone there were significant reductions in pulmonary wedge pressure (27 +/- 2 to 19 +/- 3 mm Hg; P less than 0.02) and systemic vascular resistance (1866 +/- 152 to 1393 +/- 93 dyne X sec/cm5; P less than 0.05) that were associated with increases in cardiac index (1.85 +/- 0.15 to 2.47 +/- 0.20 L/min/m2; P less than 0.02). There was a marked improvement in forearm blood flow (1.98 +/- 0.14 to 3.02 +/- 0.16 ml/min/dl; P less than 0.01) and a reduction in forearm vascular resistance (45 +/- 3 to 30 +/- 3 U; P less than 0.01). Overall there was no significant change in renal blow flow, renal vascular resistance, or glomerular filtration rate. However, there was a heterogeneous response of renal blood flow and glomerular filtration rate, such that both were directly correlated with the magnitude of increase of cardiac index (r = 0.587 [P less than 0.05] and r = 0.721 [P less than 0.01], respectively). After milrinone there were no significant overall or subgroup changes in urinary sodium excretion, blood volume, plasma renin activity, urinary aldosterone levels, plasma or platelet vasopressin levels, or plasma norepinephrine levels. Thus 1 month of therapy with milrinone improves systemic and forearm hemodynamics, but its effects on renal blood flow and function were heterogeneous. These heterogeneous effects on regional blood flow may depend on the relative vasodilator and inotropic effects of milrinone.