Ellsworth KR, et al. - Using data from the Pediatrix Medical Group’s Clinical Data Warehouse, the researchers intended to determine whether treatment with inhaled nitric oxide during the first week of life was correlated with improved in-hospital survival in a cohort of extremely preterm neonates with pulmonary hypoplasia. The results obtained from this cohort study suggested that early treatment with inhaled nitric oxide was not related to improved survival among extremely preterm neonates with pulmonary hypoplasia.

Methods

• A data set containing information from more than 350 Neonatal Intensive Care Units in 35 US states and Puerto Rico was obtained.
• They used 1-to-1 propensity score matching to reduce the imbalance of measured covariates between the 2 treatment groups since inhaled nitric oxide was not randomly prescribed.
• Singleton neonates who were born between 22 and 29 weeks’ gestation, had a birth weight of 400 g or more, were diagnosed with pulmonary hypoplasia as a cause of their respiratory distress, remained free of major anomalies, and were discharged between January 1, 2000, and December 31, 2014 were included in this initial, unmatched cohort.
• Exposure was defined as the initiation of inhaled nitric oxide on day t in days 0 to 7 of the life of a neonate.
• After that, each exposed neonate was matched 1-to-1 to a neonate who had not initiated inhaled nitric oxide on a given day.
• Mortality defined as death prior to transfer or discharge home was the primary outcome.
• Any-stage necrotizing enterocolitis, retinopathy of prematurity requiring treatment, chronic lung disease, and periventricular leukomalacia were the secondary outcomes.

Results

• Out of 92,635 neonates, they identified 767 (0.8%) with pulmonary hypoplasia who met all study inclusion criteria, of whom 185 (0.2%) were exposed to inhaled nitric oxide.
• They did not identify a significant association between inhaled nitric oxide use and mortality (hazard ratio [HR], 0.79; 95% CI, 0.57-1.11) among 151 matched pairs of exposed and unexposed neonates.
• Subgroup analyses of neonates with and without persistent pulmonary hypertension (PPHN) likewise showed no significant relationship between inhaled nitric oxide use and mortality (pulmonary hypoplasia with PPHN: HR, 0.67; 95% CI, 0.45-1.01; pulmonary hypoplasia without PPHN: HR, 1.11; 95% CI, 0.61-2.02), however, these findings may have been influenced by ascertainment bias.