URINARY NITRITE AND NITRATE CONCENTRATIONS IN PATIENTS WITH IDIOPATHIC PERSISTENT PULMONARY-HYPERTENSION OF THE NEWBORN AND EFFECT OF EXTRACORPOREAL MEMBRANE-OXYGENATION

Persistent pulmonary hypertension of the newborn (PPHN) often requires extracorporeal membrane oxygenation (ECMO), during which time pulmona ry vascular resistance gradually declines. Nitric oxide (NO) is a rece ntly recognized pulmonary vasodilator, but its role in PPHN is unknown . We tested the hypothesis that the concentrations of the urinary meta bolites of NO, i.e. nitrite and nitrate, are reduced in patients with PPHN and increase during ECMO as the PPHN resolves. Eight newborn infa nts with PPHN on ECMO were studied. Daily urinary concentrations of ni trite/nitrate were measured. We found that mean urinary concentrations of nitrite/nitrate were lower in patients with PPHN than in 47 contro ls without pulmonary disease (p < 0.005). Urinary nitrite/nitrate conc entration showed an initial increase after initiation of ECMO. However , a decrease to concentrations still lower than controls occurred on t he day before decannulation. We conclude that intrinsic NO production is significantly lower in patients with PPHN than in controls but incr eases with oxygenation. We speculate that decreased urinary NO metabol ite concentrations imply a role for NO deficiency in the pathogenesis of PPHN.