The Annals of Thoracic Surgery, Vol 32, 188-192, Copyright © 1981 by The Society of Thoracic Surgeons
Continuous hydralazine infusion for afterload reduction
MT Swartz, GC Kaiser, VL Willman, JE Codd, DH Tyras and HB Barner
Impedance reduction with a continuous infusion of hydralazine was evaluated
in 20 patients following cardiopulmonary bypass. Patients were selected for
therapy when the cardiac index (CI) was less than 2.2 L/m2/min, when the
systemic vascular resistance index (SVRI) was greater than 2,500 dyne sec
cm-5, or when both conditions were present. No other vasoactive or
cardiotonic drugs were used intraoperatively or postoperatively. Responses
were measured at 15, 30, 60, 120, 180, and 240 minutes and compared with
control measurements. Significant responses appeared by 15 minutes in the
mean arterial pressure, CI, and SVRI, which were maximal by 2 hours. At 4
hours, the SVRI was 1,520 +/- 276 dyne sec cm-5 (control, 3,235 +/- 222)
and pulmonary vascular resistance index, 365 +/- 102 dyne sec cm-5
(control, 592 +/- 71). The CI was 3.20 +/- 0.29 L/m2/min (control, 1.96 +/-
0.16) and mean arterial pressure, 75 +/- 2.3 mm Hg (control, 92 +/- 2.4).
Left atrial, pulmonary artery diastolic, and right atrial pressures
increased from control but not significantly: 11.4 +/- 0.8 to 13.3 +/- 1.2
mm Hg, 13.6 +/- 1.6 to 17.2 +/- 1.5 mm Hg, and 6 +/- 1.6 to 9.4 +/- 1.7 mm
Hg, respectively. In 16 patients, hydralazine was continued for 24 hours
and in 11, the transition to oral therapy was made. Hydralazine by infusion
effectively reduces after load, avoids the fluctuations of bolus therapy,
and allows the transition to oral therapy if needed.
