Plasma endothelin-1 in the neonatal respiratory distress syndrome.

In order to study the contribution of the vasoconstrictory peptide endothelin-1 (ET-1) to the elevation of the pulmonary vascular resistance in the neonatal respiratory distress syndrome (RDS) seven preterm infants were studied at 2, 24 and 48 hours of age for plasma ET-1 concentrations and systolic pulmonary artery pressure (PAP), measured by Doppler sonography. Plasma ET-1 levels were high during the first day after birth, but declined soon to normal levels thereafter. During the study period, the systolic PAP also decreased, whereas the systemic pressure remained unchanged. There were no correlations between plasma ET-1 and vascular pressures, but there was a significant association between ET-1 and the requirement of supplemental oxygen and the arterial-alveolar oxygen tension ratio. Our results thus suggest that high plasma ET-1 levels in the acute phase of RDS reflect the severity of the pulmonary disease, but may not significantly contribute to the elevation of the pulmonary vascular resistance in the RDS.