ABSTRACT
A full-term, female neonate developed acute hypoxemic respiratory failure complicated by persistent pulmonary hypertension of the newborn (PPHN), and responded to high-frequency oscillatory ventilation (HFOV) and inhaled nitric oxide (iNO). Discontinuation of iNO was attempted three times and was followed by severe desaturation due to right-to-left shunt through the patent ductus arteriosus and patent foramen ovale. As a result of iNO dependency state and rebound pulmonary hypertension, the neonate was maintained on iNO therapy for dipyridamole alone was unsuccessful. However, successful discontinuation of iNO therapy was achieved by combination of L-Arginine and dipyridamole. Exogeous NO may lead to down regulation of endogenous NO production, and further lead to rapid hydrolization of cyclic guanosine 3', 5' monophosphate (cGMP), the smooth muscle relaxant, by the enzyme phosphodiesterase. Moreover L-Arginine, the precursor for the formation of endogenous NO, has been found to be deficient in neonates with PPHN, so we speculated that by inhibiting phosphodiesterase and administrating L-Arginine smooth muscle relaxation occurred, and consequent weaning from iNO was achieved.