Effects of hydralazine on cardiac performance in infants receiving extracorporeal membrane oxygenation.

To determine the effects of afterload reduction on cardiac performance during partial cardiopulmonary bypass, we administered hydralazine to infants who were either normotensive (n = 11) or hypertensive (n = 12) 1 hour after extracorporeal membrane oxygenation (ECMO) was begun. Load-dependent and load-independent measures of cardiac performance and indexes of cerebral blood flow were measured. Infants in both groups had similar weight, heart rate, blood pressure, and inotropic support before ECMO. Shortening fraction was normal in both groups before ECMO (47 +/- 11% vs 49 +/- 10%; p greater than or equal to 0.05), decreased during ECMO (31 +/- 18% vs 39 +/- 12%; p greater than or equal to 0.05), and did not change after administration of hydralazine (31 +/- 12% vs 37 +/- 8%; p greater than or equal to 0.05). Cardiac output was normal in both groups before ECMO (176 +/- 71 vs 157 +/- 72 ml/kg per minute; p greater than or equal to 0.05), decreased during ECMO (120 +/- 80 vs 105 +/- 64 ml/kg per minute; p greater than or equal to 0.05), and did not change after hydralazine administration. Velocity of circumferential fiber shortening, an index of contractility (circumference per second), was normal in both groups before ECMO (1.96 +/- 0.57 vs 1.90 +/- 0.43 circ/sec; p greater than or equal to 0.05), decreased during ECMO (1.18 +/- 0.83 vs 1.56 +/- 0.58 circ/sec; p greater than or equal to 0.05), and did not change after hydralazine administration. The relationship between velocity of circumferential fiber shortening and wall stress was similar in both groups before ECMO, during ECMO, and after hydralazine administration. The cerebral blood flow resistance index was similar in both groups before ECMO (0.70 +/- 0.16 vs 0.70 +/- 0.20; p greater than or equal to 0.05), decreased during ECMO (0.45 +/- 0.13 vs 0.43 +/- 0.09; p greater than or equal to 0.05), and did not change after administration of hydralazine. We conclude that hydralazine does not improve cardiac performance during ECMO.