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Many premature infants at risk for bronchopulmonary dysplasia experience episodes of surfactant dysfunction with reduced surfactant protein B (SP-B). In this study, we investigated the safety and responses to booster doses of surfactant. A total of 87 infants, 500 to 1250 g birth weight, who were ventilated at 7 to 10 days received 2 or 3 doses of Infasurf (Calfactant, Forest Pharmaceuticals, St Louis, MO, USA) within a 1-week period. For 184 doses, occurrence rates of transient bradycardia (13) and plugged endotracheal tube (5) were low, and no other adverse effects were noted. Treatment transiently improved the respiratory severity score (FiO2 × mean airway pressure), SP-B content (+75%) and surface properties of isolated surfactant. Levels of eight proinflammatory cytokines in tracheal aspirate were interrelated and unchanged from baseline after surfactant treatment. Booster doses of surfactant for premature infants with lung disease are safe and transiently improve respiratory status as well as composition and function of endogenous surfactant.

Methods Peripheral blood samples were collected from premature infants at the time of hospital discharge at multiple sites and shipped to a central laboratory. Freshly purified PBMCs were isolated by Ficoll gradient centrifugation, sorted into individual lymphocyte cell types, and processed for total RNA. RNA isolated from CD8 lymphocytes (n=79) was used for RNA-Seq analysis using the Illumina HiSeq2500. Sequences were aligned using the SHRiMP algorithm and expression values were summarized using HTSeq. Normalized gene expression data were analyzed for significant changes in expression using various statistical approaches. Ingenuity Pathway Analysis software was used for gene set interpretation.