495 Impaired Surfactant Protein B Synthesis in Infants with Congenital Diaphragmatic Hernia

Abstract

Background: Whether congenital diaphragmatic hernia (CDH) is associated with surfactant deficiency or dysfunction is controversial. Aims: To measure disaturated phosphatidylcholine (DSPC) and surfactant protein B (SP-B) synthesis and metabolism in infants with CDH. Methods: DSPC and SP-B amounts and kinetics were studied in tracheal aspirates (TA) of 12 infants with CDH (BW 2978±447g, GA 38±2 wk) and in 8 GA-matched control infants (BW 3160±350g, GA 38±2 wk). Seventeen infants received a 24h infusion of 13C-leucine, an i.v. bolus of 2H2O and 0.0625% of fluid intake as 2H2O every 12h over the next 48h. Three infants received only 13C-leucine infusion. DSPC and SP-B were isolated from TA. DSPC amounts, 2H-palmitate and 13C-leucine enrichments were measured by gas chromatography mass spectrometry. Results: DSPC amount and kinetics have been measured in 17 newborns, and SP-B kinetics in 18. DSPC median (interquartile range) fractional synthesis rate (FSR) was 5.0 %/day (3.5-8.5) in CDH patients vs 6.1 %/day (5.8-7.0) in controls (p=0.31). DSPC secretion time (ST) was 10.7h (6.9-11.5) vs 7.9h (5.2-14.0) (p=0.65). SP-B FSR was 33.4 %/day (28.4-42.9) vs 52.0 %/ day (40.0-83.4) (p=0.03); SP-B peak time was 26h (24-32) vs 18h (15-21) (p=0.02), both significantly lower in the CDH group. SP-B ST was 6.1h (4.0- 9.9) vs 2.7h (1.1-7.1) (p=0.24), and half life 7.5h (5.2-9.1) vs 11.1h (5.8-17.3) (p=0.33). Conclusions: Decreased and delayed SP-B synthesis was found in newborns with CDH compared to controls while DSPC kinetics was similar in both groups, which may contribute to severe respiratory failure in these patients.