Surfactant in meconium aspiration syndrome

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Meconium aspiration syndrome (MAS) has been one of the most frightening adverse consequences of term delivery. Fortunately, severe MAS has decreased strikingly in recent years because fewer infants deliver after 40-41 weeks gestation and because obstetric management has avoided most hypoxic events during labor and delivery. MAS has been described as a syndrome where the aspiration is simply the proximal indicator for a series of events resulting from birth depression and often in pulmonary hypertension. However, meconium does have effects on the lung: it causes airway obstruction, inflammation and inactivates surfactant. Therefore, MAS might be a sentinel event that could result in abnormal surfactant metabolism as a result of direct toxicity causing inhibition or inflammation/injury to type II cells or indirectly because of the effects of the associated birth asphyxia or pulmonary hypertension on the fetal lung. The worst cases of MAS have pulmonary hypertension and may end up on extracorporeal membrane oxygenation (ECMO). Janssen et al report that infants with MAS on ECMO have disturbed surfactant synthesis and decreased surfactant concentrations in airway fluid. They used sophisticated modeling and measurements with stable isotopes to complement previous reports that the function of surfactant in MAS is abnormal and that surfactant treatments can improve lung function. Clearly, surfactant function and metabolism is disturbed at many levels and for multiple reasons in infants with MAS.