Objectives. To assess the dose-related effects of inhaled nitric oxide (I-NO) as a specific adjunct to early conventional therapy for term infants with persistent pulmonary hypertension (PPHN), with regard to neonatal outcome, oxygenation, and safety.

Methods. Randomized, placebo-controlled, double-masked, dose-response, clinical trial at 25 tertiary centers from April 1994 to June 1996. The primary endpoint was the PPHN Major Sequelae Index ([MSI], including the incidence of death, extracorporeal membrane oxygenation (ECMO), neurologic injury, or bronchopulmonary dysplasia [BPD]). Patients required a fraction of inspired oxygen [Fio2] of 1.0, a mean airway pressure ≥10 cm H2O on a conventional ventilator, and echocardiographic evidence of PPHN. Exogenous surfactant, concomitant high-frequency ventilation, and lung hypoplasia were exclusion factors. Control (0 ppm) or nitric oxide (NO) (5, 20, or 80 ppm) treatments were administered until success or failure criteria were met. Due to slowing recruitment, the trial was stopped at N = 155 (320 planned).

Results. The baseline oxygenation index (OI) was 24 ± 9 at 25 ± 17 hours old (mean ± SD). Efficacy results were similar among NO doses. By 30 minutes (no ventilator changes) the Pao2 for only the NO groups increased significantly from 64 ± 39 to 109 ± 78 Torr (pooled) and systemic arterial pressure remained unchanged. The baseline adjusted time-weighted OI was also significantly reduced in the NO groups (-5 ± 8) for the first 24 hours of treatment. The MSI rate was 59% for the control and 50% for the NO doses (P = .36). The ECMO rate was 34% for control and 22% for the NO doses (P = .12). Elevated methemoglobin (>7%) and nitrogen dioxide (NO2) (>3 ppm) were observed only in the 80 ppm NO group, otherwise no adverse events could be attributed to I-NO, including BPD.

Conclusion. For term infants with PPHN, early I-NO as the sole adjunct to conventional management produced an acute and sustained improvement in oxygenation for 24 hours without short-term side effects (5 and 20 ppm doses), and the suggestion that ECMO use may be reduced.

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