Effect of inhaled nitric oxide on raised pulmonary vascular resistance in children with congenital heart disease.

OBJECTIVE To study the short-term effects of inhaled nitric oxide in infants and young children with congenital heart disease. SETTING A supraregional referral centre for children with congenital heart disease. PATIENTS AND METHODS 22 infants and children aged 3-32 months (median age 5 months) with congenital heart disease undergoing preoperative cardiac catheterisation. All but one infant had intracardiac shunt lesions and 13 had increased pulmonary vascular resistance. During catheterisation the patients inhaled nitric oxide in a concentration of 40 parts per million in room air. Pulmonary and systemic haemodynamic variables were evaluated by means of measured oxygen consumption and the Fick principle before and after 10 minutes' exposure to nitric oxide. RESULTS Inhaled nitric oxide did not affect the systemic circulation. There was a significant reduction in the pulmonary vascular resistance, but only in the 13 infants with pulmonary hypertension, in whom pulmonary vascular resistance was reduced by 34% from 8.6 (4.6) mm Hg.min.m2.l-1 (mean (SD)) to 5.7 (3.5) mm Hg.min.m2.l-1. The pulmonary circulation in infants with normal pulmonary vascular resistance was not affected. No statistically significant increase in methaemoglobin was seen, though there were large individual differences. No other side effects were seen. CONCLUSION The present study shows that in infants with congenital heart disease inhaled nitric oxide reduced pathologically increased pulmonary vascular resistance without affecting systemic circulation and without important side effects with brief exposure.