Inhaled Nitric Oxide for Persistent Pulmonary Hypertension in Term Neonates: An Updated Meta-Analysis of Mortality and Need for ECMO

Abstract

Introduction: Persistent pulmonary hypertension of the newborn (PPHN) causes severe hypoxemia. Inhaled nitric oxide (iNO) is a selective pulmonary vasodilator, but trials have shown variable effects on mortality and extracorporeal membrane oxygenation (ECMO) requirement. This updated review synthesizes recent evidence.

Methods: Cochrane Library, Embase, and ClinicalTrials.gov were searched for RCTs of iNO versus placebo or standard care in term/late preterm (≥34 weeks) neonates with PPHN (oxygen index ≥15). Primary outcomes: all-cause mortality before discharge, need for ECMO. Secondary: length of ventilation, neurodevelopmental impairment. Fixed-effects meta-analysis for rare events.

Results: Twelve RCTs (n=1,284 neonates) were included. iNO significantly reduced ECMO requirement (RR 0.67, 95% CI 0.54–0.83, p<0.001, NNT=8). Mortality reduction did not reach significance (RR 0.81, 95% CI 0.62–1.06, p=0.12). In subgroup analysis, neonates with oxygenation index >40 had greater mortality benefit (RR 0.62, 95% CI 0.43–0.89). No difference in severe neurodevelopmental impairment at 18 months (RR 0.94, 95% CI 0.71–1.24). Methemoglobin levels >5% occurred in 3% of iNO infants.

Discussion: iNO effectively reduces ECMO need but mortality benefit is limited to the most hypoxemic subgroup. This suggests iNO prevents progression to ECMO but does not reverse underlying parenchymal disease. Lack of long-term neuroprotection is consistent with severe PPHN’s overall poor prognosis.

Conclusions: iNO is indicated for term neonates with severe PPHN and oxygen index >40. For less severe cases, benefit is marginal. ECMO should remain available for iNO non-responders.