Endogenous Surfactant Production in Preterm Infants Is Not Supressed By Exogenous Surfactant Administration

Aims. Whether endogenous surfactant production in preterm infants changes due to exogenous surfactant therapy is unknown. Therefore, we measured endogenous surfactant production with a new method using stable isotopes. Methods. Four preterm infants (992±88g, 27.9±0.8 wk) with mild neonatal RDS without exogenous surfactant treatment and 4 preterm infants (968±74 g, 27.6±1.3 wk) with severe RDS with exogenous surfactant treatment were included. All patients received a 24h [U-¹³C]glucose infusion, starting 4.2±1.1 h after birth. Tracheal aspirates were obtained and the surfactant phosphatidylcholine(PC) was isolated. The enrichment of plasma glucose and of palmitic acid in surfactant PC was measured by GC-IRMS. The fractional synthesis rate (FSR) which is the fraction of the total pool synthesised per day was calculated as the PC palmitate enrichment divided by the steady state plasma glucose enrichment. The absolute production rate was calculated as the FSR times the total pool size. Results. In the untreated patients the surfactant PC pool size is ≤ 87 mg/kg, after 2x surfactant treatment the total surfactant PC pool size is -179 mg/kg.Table

Table 1

Conclusion. This novel method shows no suppression of exogenous surfactant on endogenous surfactant production. The data even suggest that exogenous surfactant stimulates absolute endogenous surfactant production.