Effects of surfactant treatment on gas-exchange and clinical course in near-term newborns with RDS

Objective: To determine if there is a relationship between acute improvement in pulmonary gas exchange and surfactant use in near-term (35-39 weeks' gestation) infants with respiratory distress syndrome (RDS). Methods: We examined retrospectively the records of 54 infants admitted during a 15 month period who were 35 or more weeks of gestation, and who demonstrated all the diagnostic features of RDS. Data analyzed included: birth weight; gestational age; Apgar scores; calculated alveolar to arterial oxygen gradient (AaDO(2)) and oxygenation index (0I); hours of life at intubation; surfactant administration; complications with surfactant administration; use of inotropic medications. Results: A total of 30 of infants were treated with intubation and surfactant administration. Mean FiO(2) at the time of surfactant administration was 0.96. The AaDO(2) decreased from 64.0 +/- 14.8 kPa to 41.8 +/- 22.5 kPa by 6 hrs (p < 0.0001). There was no relationship between age at treatment (6-89 hr) and response to treatment as measured by changes in AaDO(2), FiO(2), or oxygenation index (OI). Conclusions: Near-term infants with severe RDS often respond to exogenous surfactant, suggesting a functional deficiency of endogenous surfactant at a "late" stage in their disease process. We speculate that delayed treatment may still be effective in these patients.