Elastase activity and surfactant protein concentration in tracheal aspirates from neonates receiving synthetic surfactant

Neutrophil elastase activity and the concentration of surfactant proteins A and B (SP-A, B) were measured in tracheal aspirate fluid from preterm neonates who were treated with the synthetic surfactant Exosurf Neonatal or air placebo in randomized, placebo-controlled, clinical trials. Elastase activity was transiently reduced in surfactant-treated infants on the second day of life, but the reduction was not sustained. In placebo-treated infants with established respiratory distress syndrome, tracheal aspirate SP-A was low on the first day of life and increased with time as respiratory distress syndrome resolved. In infants with respiratory distress syndrome treated with surfactant, significantly higher levels of SP-A were observed by 2 days after treatment and were maintained through at least the sixth day of life. These data suggest that lung inflammation is not increased and that endogenous surfactant secretion may be stimulated, not suppressed, by treatment with synthetic surfactant.