Pulmonary vascular resistance after cardiopulmonary bypass in infants: Effect on postoperative recovery

Objective: We sought to define the contemporary clinical effect of increase d pulmonary vascular resistance in infants after congenital heart operation s with cardiopulmonary bypass. Methods: Fifteen infants (median age, 0.31 years; median weight, 5.1 kg) un derwent cardiac operations involving cardiopulmonary bypass (range, 49-147 minutes). Pulmonary vascular resistance was measured in the immediate posto perative period in the intensive care unit by means of the direct Fick prin ciple, with respiratory mass spectrometry to measure oxygen consumption. Th e effect of ventilation with an inspired oxygen fraction of 0.65, with addi tional infusion of L-arginine, substance P, and inhaled nitric oxide, was a ssessed and subsequently correlated with the length of mechanical ventilati on from the end of cardiopulmonary bypass to successful extubation. Results: Overall, pulmonary vascular resistance at baseline (11.7 +/- 5.6 W U . m(2)) could be reduced to a minimum of 6.1 +/- 3.5 WU . m(2). The venti latory time was 0.86 to 14.9 days (median, 1.75 days) and correlated direct ly with the lowest pulmonary vascular resistance value achieved during the pulmonary vascular resistance study (r(2) = 0.64, P < .01). The patient sub group with mechanical ventilation of greater than 2 days had significantly higher pulmonary vascular resistance at all stages of the study protocol, a nd in this group there was a correlation of cardiopulmonary bypass time and ventilatory support time (r(2) = 0.48, P < .05). Conclusion: Increased pulmonary vascular resistance, either directly or as a surrogate of the systemic inflammatory response after cardiopulmonary byp ass, continues to have a significant effect on postoperative recovery of in fants after cardiac operations.