Methemoglobin to cumulative nitric oxide ratio and response to inhaled nitric oxide in PPHN.
BACKGROUND
One-third of infants with persistent pulmonary hypertension of the newborn (PPHN) do not respond to inhaled nitric oxide (iNO). If iNO is not delivered to the pulmonary vasculature because of parenchymal lung disease, it cannot interact with hemoglobin to form methemoglobin (MHb).


OBJECTIVE
To study the correlation between oxygenation response to iNO in infants with PPHN secondary to parenchymal lung disease and initial MHb% to cumulative NO exposure (ppm x hours) ratio (MHb/SigmaNO).


METHODS
Retrospective chart review of neonates with PPHN secondary to parenchymal lung disease treated with iNO comparing non-responders (PaO(2)/FiO(2) ratio<10 change with iNO) with responders (>or=10 change).


RESULTS
Non-responders (n=16) had a PaO(2)/F(iO2) of 83+/-48 (mean+/-s.d.) and decreased to 74+/-44 after iNO. PaO(2)/FiO(2) increased from 70+/-48 to 151+/-63 with iNO among responders (n=36). The MHb/SigmaNO ratio was low (0.024+/-0.012) among non-responders compared with responders (0.07+/-0.053, P<0.005).


CONCLUSIONS
Inadequate oxygenation response to iNO is associated with lower MHb/SigmaNO, suggesting suboptimal delivery of iNO to the pulmonary vasculature.
Pabalan
M J
MJ
Department of Pediatrics, Division of Neonatology, University at Buffalo, Women and Children's Hospital of Buffalo, Buffalo, NY 14222, USA.
Nayak
S P
SP
Ryan
R M
RM
Kumar
V H
VH
Lakshminrusimha
S
S
D000280:Administration, Inhalation; D001784:Blood Gas Analysis; D016022:Case-Control Studies; D004305:Dose-Response Relationship, Drug; D016903:Drug Monitoring; D006801:Humans; D007231:Infant, Newborn; D008471:Meconium Aspiration Syndrome / Q000150:complications; D008706:Methemoglobin / Q000032:analysis* / Q000378:metabolism; D009569:Nitric Oxide / Q000008:administration & dosage* / Q000097:blood*; D010547:Persistent Fetal Circulation Syndrome / Q000150:complications / Q000188:drug therapy*; D011015:Pneumonia, Aspiration / Q000150:complications; D012127:Respiratory Distress Syndrome, Newborn / Q000150:complications; D012189:Retrospective Studies; D017211:Treatment Failure; D014665:Vasodilator Agents / Q000008:administration & dosage* / Q000097:blood*
D014665:Vasodilator Agents; D009569:Nitric Oxide; D008706:Methemoglobin