Association between peak serum bilirubin and severity of respiratory distress syndrome in infants of less than 30 weeks' gestation.

Introduction: Bilirubin can enter the alveolar space where it could inactivate surfactant and act as an anti-oxidant agent.

Objective: To assess the hypothesis that total serum bilirubin level (TSB) may affect the severity of respiratory distress syndrome (RDS) and the need of respiratory supports in preterm infants.

Study Design: We performed a retrospective study of 184 preterm infants with RDS, whose peak TSB had a median value of 194.8 micromol/L (=11.3 mg/dL). This value was used to stratify patients into two groups: neonates who developed low and high TSB (< or = or >194.8 micromol/L, respectively). For each patient the highest values of inspired oxygen fraction (FiO(2)), arterial to alveolar oxygen tension ratio (a/APO(2)), oxygenation index (O.I.), ventilatory index (V.I.), and the need and duration of respiratory supports were recorded.

Results: Seventy-five infants were included in the low TSB group and 74 were included in the high TSB group. The RDS severity and the need of respiratory supports were similar in both the groups. The first day of life TSB and peak TSB did not correlate with the highest values of FiO(2) and a/APO(2), and the duration of mechanical ventilation.

Conclusions: We did not find any correlation between TSB level and RDS severity. We speculate that this result is because the potential inhibiting effect of bilirubin on surfactant function is neutralized by the exogenous surfactant treatment, while its antioxidant effects do not provide appreciable benefits in the lung tissue.