Inhaled nitric oxide therapy in premature infants with mild to moderate respiratory distress syndrome.

ABSTRACT

Inhaled nitric oxide (iNO) therapy has been demonstrated to acutely improve oxygenation in preterm infants with severe pulmonary disease. Administration of iNO to the premature infants with less severe pulmonary illness has not yet been studied extensively. Therefore, the authors performed a pilot study enrolling thirty-four premature infants with respiratory distress syndrome (RDS) within 72 hours of age, birth weight between 500-2,000 g, whose oxygenation indexes exceeded our birthweight-specific criteria. Infants were randomly assigned to either treatment with (iNO group; n = 16) or without (control group; n = 18) iNO. Inhaled NO was started at 20 ppm and weaned to 5 ppm over 24-48 hours. Routine cranial ultrasonography was performed and the occurrence of intraventricular hemorrhage (IVH) was interpreted by an attending pediatric radiologist unaware of the treatment group assignment. The study showed that the two groups were of similar birth weight (mean+/-SEM) control 901+/-73 g vs iNO 874+/-70 g; and gestational age control 27.2+/-0.5 wk vs iNO 26.8+/-0.5 wk. Other baseline parameters between the two groups were also similar. The mean ages of the infants at the time of entry were 11.7+/-2.2 and 8.3+/-0.9 hours in the controls and iNO group. The entry oxygenation index (OI) did not differ between the two groups control 11.9+/-2.2 vs iNO 10.8+/-1.50. After 30 minutes of iNO therapy, there was a 50 per cent increase in partial pressure of oxygen tension (PaO2) and 15 per cent reduction in OI, (p = 0.02 and p = 0.04 vs baseline, respectively). No statistical difference in the incidence of significant IVH (Grade III and IV) was detected control 27.8 per cent; iNO 25.0 per cent. The incidence of other acute complications as well as early neonatal death, were comparable between the groups. The mean methemoglobin concentration was 1.2+/-0.5 per cent. In conclusion, these preliminary data suggest that iNO, as used in this protocol, acutely improves oxygenation without increasing significant IVH in premature infants with mild to moderate RDS. These important findings serve to justify further study of the efficacy of iNO on long term pulmonary outcome and mortality in this group of infants.