Response to inhaled nitric oxide in premature and term neonates

Inhaled nitric oxide (iNO) has emerged as a promising therapeutic agent in the treatment of persistent pulmonary hypertension of the newborn. Several theories exist regarding causes of both response and nonresponse to iNO. Cl inical trials differentiate disease entities (primary vs secondary persiste nt pulmonary hypertension associated with meconium aspiration syndrome, pne umonia or congenital diaphragmatic hernia) and their specific response rate s, iNO combined with high-frequency ventilation appears to be superior to i nhalation of nitric oxide (NO) during conventional ventilation. Little is k nown regarding the role of the degree of lung expansion and its modificatio n - no matter what mode of ventilation is applied. Gestational age plays an important role in relation to the potential adverse effects of NO. Of part icular concern in the premature neonate is the effect of NO on bleeding tim e and the inhibition of platelet aggregation. Those potentially hazardous e ffects need to be carefully weighed against early intervention with iNO at a comparably low oxygenation index in order to prevent the vicious cycle of hypoxaemia and subsequent increased right-to-left shunting. Further studie s are required to determine the optimal timing, mode of delivery and mode o f ventilation used with iNO therapy in order to optimise the response of pr emature and term neonates.