Surfactant phosphatidylcholine metabolism in neonates with meconium aspiration syndrome

Objective: Because meconium directly inhibits surfactant function, we sought to determine the effect of meconium on endogenous surfactant synthesis and clearance. Study design: 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. Results: 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. Conclusion: We conclude that surfactant synthesis is disturbed and that surfactant PC concentrations are low in infants with MAS on ECMO.