Serial changes in levels of IL-6 and IL-1β in premature infants at risk for bronchopulmonary dysplasia

The aim of this study was to define the inflammatory changes occurring in the lungs of infants at risk for bronchopulmonary dysplasia (BPD) over the first 28 days of life, and to define an optimal strategy for steroids therapy in the prevention of BPD. We measured levels of interleukin-6 (IL-6) and interleukin-l beta (IL-1 beta) in tracheal aspirate (TA) samples and blood of premature infants with severe respiratory distress syndrome RDS (n=45) on the first day of life prior to initiation of surfactant therapy and on days 5-7, 12-14, 19-21, and 26-28. Levels of IL-6 and IL-1 beta were determined with a commercially available enzyme-linked immunoassay. Logistic regression analyses were performed in order to examine differences in trends in levels of IL-6 and IL-1 beta between groups of infants. Infants were divided into group I (n = 30, FiO(2) less than or equal to 0.35 at 28 days) and group II (n=15, FiO(2)>0.35 based on their likelihood of developing BPD at 36 weeks postconceptional age (PCA). The infants were comparable with respect to mean (+/-SEM) birth weight (895+/-33 g vs. 900 +/- 40 g), gestational age (27 +/- 0.38 weeks vs. 27 +/- 0.54 weeks), and severity of respiratory illness at entry into the study (mean airway pressure: 12 +/- 1 cmH(2)O vs, 12 +/- 1 cmH(2)O, and oxygen index: 15 +/- 2 vs. 19 +/- 4) (group I vs. group II, respectively), Logistic regression analyses failed to reveal any significant differences in linear trends of levels of IL-6 and IL-1 beta in TA samples between both groups of infants. No particular pattern of change in levels of IL-6 or IL-1 beta could be identified among groups of infants. Levels of IL-6 and IL-1 beta in TA samples on the first day of life failed to predict the need for FiO(2) > 0.35 at 28 days of age. We could not identity an increasing trend or a specific pattern of changes in postnatal levels of IL-6 or IL-1 beta in TA samples of infants who were at greater risk of developing BPD at 36 weeks PCA compared to infants who were not.