Biochemical Features and Clinical Factors Influencing Response to Surfactant Treatment Among Infants Born Late...

To evaluate main biophysically active surfactant components and inflammatory mediators, and to identify the factors associated with good response to surfactant, in late preterm infants with respiratory distress syndrome (RDS).

This was a prospective, multicenter, cohort study enrolling late (gestational age 34^+0/7-36^+6/7 weeks [late-PT_RDS]) and moderately (gestational age 32^+0/7-33^+6/7 weeks, [moderately-PT_RDS]) preterm infants with RDS. Term infants with no lung disease (term-NLD) were enrolled as controls. The concentration of disaturated-phosphatidylcholine (DSPC), surfactant protein-B (SP-B), total proteins, interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in epithelial lining fluids were measured by high-performance liquid chromatography-mass spectrometry, enzyme-linked immunosorbent assay, Lowry, or Luminex techniques, respectively, and corrected using plasma-to-bronchoalveolar lavage fluid urea ratio. Clinical data, including inspired oxygen fraction (FiO₂) and preductal oxygen hemoglobin saturation (SpO₂), were recorded in real-time.

We studied 55 late-PT_RDS, 44 moderately-PT_RDS, and 18 term-NLD infants. DSPC was lower in late-PT_RDS (43 [24-124] mg/dL) than in term-NLD (249 [147-688] mg/dL, P < .001) but similar to that of moderately-PT_RDS (30 [9-80] mg/dL, P = .083). SP-B, total proteins, IL-1β, IL-6, and tumor necrosis factor-α were similar between late-PT_RDS and moderately-PT_RDS. SP-B, total proteins, and IL-6 were significantly higher in late-PT_RDS than term-NLD. Each hour of delay for surfactant administration, each 5-point increase in FiO₂ threshold, and each 5-point decrease in preductal hemoglobin saturation SpO₂/FiO₂ ratio before surfactant treatment decreased the likelihood of good response by 12% (P = .002), 28% (P = .019) and 15% (P = .028), respectively.

Late-PT_RDS had DSPC and SP-B levels similar to moderately-PT_RDS. Early administration, lower FiO₂ threshold, and better oxygenation prior to surfactant treatment were associated with a better response to surfactant therapy.