Inhibition of pulmonary surfactant function by meconium

Article Abstract:

When meconium (a mixture of bile salts, cholesterol, enzymes, and cell debris from the fetal intestinal tract) becomes lodged in the respiratory tract of infants, there is an increased risk for neonatal respiratory distress, a condition of serious impairment of breathing. Meconium is present in amniotic fluid (in which the fetus floats) in as many as 18 percent of all deliveries, and many infants inhale meconium during delivery. While much of the damage associated with meconium aspiration results from airway obstruction, it is possible that these substances also have chemical effects on the lung. In adult respiratory distress (RDS; acute respiratory failure), a frequently fatal condition, pulmonary surfactant may become inactivated. Surfactant is a substance that lines the lung and lowers its surface tension, preventing collapse of the organ. It is possible that meconium also affects surfactant adversely in the infant. This was evaluated in experiments that tested the effects of meconium obtained from healthy infants on lung surfactant from calves. Meconium was found to inhibit the ability of surfactant to lower the surface tension; at low concentrations of surfactant, even very small quantities of meconium led to considerable increases in surface tension. Above a certain concentration of surfactant, no inhibitory effect was seen, but that concentration was quite high. The results suggest that replacing surfactant may be an effective treatment for some cases of pulmonary disease involving meconium. (Consumer Summary produced by Reliance Medical Information, Inc.)

Respiratory distress syndrome, Pulmonary surfactant, Pulmonary surfactants

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Inhibition of neutrophil oxidative burst and phagocytosis by meconium

Article Abstract:

The presence of meconium in amniotic fluid may increase the risk of infection by reducing the ability of cells to digest and eliminate bacteria. Researchers analyzed the interaction of meconium and amniotic fluid obtained from four infants at delivery. Both light and very light levels of meconium inhibited the ability of cells to kill bacteria by oxidative burst. Moderate levels of meconium inhibited the ability of infection-fighting cells to swallow bacteria, but light levels of meconium did not. Meconium has been known to be associated with infection within the amniotic sac, and this study explains how meconium may increase the risk of infection.

Risk factors, Neutrophils, Chorioamnionitis

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A selective aggressive approach to the neonate exposed to meconium-stained amniotic fluid

Article Abstract:

Intubating only selected infants exposed to meconium at birth may be appropriate. Intubating involves inserting a breathing tube into the airway. Doctors did not intubate newborns exposed to meconium if they weighed more than 2500 grams at birth, were delivered vaginally, or were born after more than 37 weeks of pregnancy. According to these criteria they placed breathing tubes in 48% of 659 exposed infants. None of the exposed infants who were not intubated developed meconium aspiration syndrome. All exposed newborns were suctioned with a DeLee device.

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