Methemoglobin and the response to inhaled nitric oxide in persistent pulmonary hypertension of the newborn

We aimed to investigate whether the change in methemoglobin levels (ΔMHb) predicts oxygenation response to inhaled nitric oxide (iNO) in persistent pulmonary hypertension of the newborn (PPHN) with lung disease, with or without pulmonary hypoplasia.In this prospective observational study, infants were categorized based on ΔMHb and oxygenation response (ΔPaO2/FiO2) following iNO: ΔMHb ≤0 or ΔMHb0, and ΔPaO2/FiO2 20 mmHg (Non-responder) or≥20 mmHg (Responder). ΔMHb levels were compared among infants with or without pulmonary hypoplasia.Among infants with pulmonary hypoplasia (n = 28), ΔMHb was not associated with an oxygenation response to iNO or survival without ECMO. Among infants without hypoplasia (n = 29), subjects with ΔMHb0 following iNO (n = 21) had a greater ΔPaO2/FiO2 (median, 64 mmHg; IQR, 127; p 0.01) and 100% survival without extracorporeal membrane oxygenation (ECMO) when compared to infants with ΔMHb ≤0 (n = 8; median 10 mmHg; IQR, 33).PPHN secondary to lung disease without hypoplasia with increased ΔMHb following iNO was associated with better oxygenation response and survival without ECMO compared to subjects without an increase in MHb.