Factors affecting plasma bilirubin in preterm infants ventilated for respiratory distress syndrome

OBJECTIVE: To evaluate the contribution of various factors to plasma bilirubin level in preterm infants with a birth weight of < 1500 gm in need of mechanical ventilation for respiratory distress syndrome (RDS) during their first week of life. METHODOLOGY: A total of 50 very low birth wight (< 1500 gm) pretenn infants consecutively admitted to the neonatal intensive care unit were studied Plasma bilirubin levels were determined every 8 hours for the first week of life. Data relating to daily body weight, daily fluid intake, age at onset of gavage feeds, daily caloric intake, and grade of intraventricular hemorrhage (IVH) were collected Data relating to mechanical ventilation were collected every 4 hours as follows: fractional inspired O₂, arterial Po₂, arterial Pco₂, and mean airway pressure. An arterial/alveolar Po₂ ratio and a corrected oxygenation index were computed for the first 2 days of life. A bilirubin index (BI), defined as the ratio of peak plasma bilirubin level to birth weight^1/3, was used to study the association between bilirubin and the above variables. A BI was also used as a criterion for starting and discontinuing phototherapy. Multiple linear regression analysis was used to model BI. RESULTS: IVH (p < 0.0001), age at onset of gavage feeds (p < 0.003), oxygenation index (p < 0.007), and gestational age (p < 0.05) made a significant contribution to variations in BI (37.16%, 43.71%, 48.99%, and 53.33%, respectively). CONCLUSION: Hyperbilirubinemia in ventilated preterm infants with RDS is most likely multifactorial; entities quite distinct from RDS (such as nutrition and IVH) may significantly contribute to its variation.