Inhaled Nitric Oxide in Neonates With Elevated A-aDO2 Gradients Not Requiring Mechanical Ventilation

Inhaled nitric oxide (iNO) is currently used in the management of ventilated neonates with hypoxemic respiratory failure. We have shown that iNO administered by oxygen hood reduces pulmonary vascular resistance in hypoxia- and group B streptococcus-induced pulmonary hypertension in an animal model (J Perinatol 2002; 22:50-6). Our objective was to determine the feasibility of iNO administration by oxygen hood in neonates with respiratory failure. Methods: A masked randomized controlled trial was performed on eight infants with respiratory failure. Inclusion criteria were: gestation>34 weeks, age<7 days, with post-ductal arterial line, and A-aDO2 400-600 on two consecutive blood gases. Infants were randomized to study gas (iNO at 20 ppm or equivalent flow of O2) for 1 hr which was then weaned over the next 4 hours. The iNO was introduced into an oxygen hood using an INOvent (INO Therapeutics, Inc). The primary outcome was the PaO2 one hour after randomization. Environmental leakage of NO and NO2 were measured. Results: Four infants were randomized to iNO and four to O2 (controls). Two of the four infants given iNO had an increase in PaO2 of >100 mm Hg, while oxygenation was unchanged in the controls. Methemoglobinemia and other adverse effects were not noted in any infant. Environmental levels of NO and NO2 were minimal (<1ppm) to undetectable at >0.3m from the hood. Conclusions: Administration of iNO by oxygen hood is feasible. Larger randomized controlled trials are required to measure the efficacy and determine an appropriate target population for this technique.