Inhalation of low-dose nitric oxide to evaluate pulmonary vascular reactivity in children with congenital heart disease

The objective of this study was to investigate the efficacy of low-dose nit ric oxide (NO). The study used fifteen consecutive Japanese preoperative pa tients (7 males and 8 females) with congenital heart disease and pulmonary hypertension (mean pulmonary arterial pressure >30 mmHg), 6 of these patien ts had Down's syndrome. Hemodynamic measurements were taken in room air, 10 0% oxygen, 5 and 40 parts per million NO (NO5 and NO40) by inhalation. The differences between two observations within the same group were determined by the two-tailed paired t-test. A pulmonary vascular resistance (R-p) regr ession curve was constructed by using linear regression analysis. The perce ntage change in pulmonary arterial pressure per systemic arterial pressure (P-p/P-s) with NO40 (P-p/P-s-40) exceeded that of PpPs-5 (p < 0.0001), The percentage change for the R-p with NO40 (Rp-40) was larger than that for th e R-p-5 (p = 0.0003). The percentage change of P-p/P-s-5 and that with oxyg en were similar (p = 0.266), The relationship between R-p-5 and R-p-40 was linear. In conclusion, the effects of NO5 were equivalent to 100% oxygen bu t less than NO40. NO5 should initially be used to test pulmonary reactivity , If there is no response, patients should still be given NO40.