Surfactant phosphatidylcholine metabolism in neonates with meconium aspiration syndrome

Because meconium directly inhibits surfactant function, we sought to determine the effect of meconium on endogenous surfactant synthesis and clearance. We studied surfactant phosphatidylcholine kinetics with the use of stable isotopes in 11 newborn infants with meconium aspiration syndrome (MAS) who required extracorporeal membrane oxygenation (ECMO). For comparison we studied 6 neonates with persistent pulmonary hypertension (PPHN) on ECMO and 10 term neonates ventilated for non-pulmonary indications and not on ECMO. All patients received a 24-hour [U- 13C]glucose infusion as precursor for the palmitic acid in surfactant phosphatidylcholine. In the meconium group, the maximal 13C-incorporation in phosphatidylcholine (PC) was half of that in controls (0.09 ± 0.01 vs 0.18 ± 0.03 atom percent excess [APE], P = .027). There was a trend toward lower surfactant synthesis in the MAS group (3.3 ± 0.7%/day) and PPHN group (2.6 ± 0.3%/day) compared with controls 8.0 ± 2.4%/day, P = .058). Significantly lower PC concentrations in tracheal aspirates were found in the MAS group (4.4 ± 2.6 mg/mL) and PPHN group (3.6 ± 2.0 mg/mL) compared with controls (12.8 ± 2.6 mg/mL, P = .01). Endogenously synthesized surfactant had a similar half-life in all groups, ranging from 63 to 98 hours. We conclude that surfactant synthesis is disturbed and that surfactant PC concentrations are low in infants with MAS on ECMO.