Endothelin-1 in plasma and airways of preterms with respiratory distress syndrome

ABSTRACT

The objective of the study was to characterize the relationship between endothelin 1 [ET-1] concentration in plasma and airway of the preterm and the severity of respiratory distress syndrome [RDS] in early postnatal period. 44 preterm neonates were enrolled in two groups. Group I comprised 29 preterm with RDS requiring mechanical ventilation. They were further discriminated into 3 subgroups according to severity of RDS [mild, moderate and severe RDS]. Group II comprised 15 preterms on mechanical ventilation for repeated attacks of apnea of prematurity, matched for gestational and postnatal age with group I and served a reference group. Laboratory investigations included plain chest radiographs, sepsis work -up to rule out infection, arterial blood gas analysis with calculation of arterial alveolar oxygen ratio [a/A O2]. ET-1 concentration was measured in plasma and tracheal aspirates within the first 48 hours of life. Mean plasma ET-1 concentrations were significantly elevated in preterms with moderate and severe RDS as compared to reference preterms [P <0.01 and P <0.001, respectively]. Significant negative correlation existed between plasma ET-1 and each of gestational age and 1 and 5 minutes Apgar scores, whereas significant positive correlation-existed between plasma ET-1 and each of fraction of inspired oxygen [Fi02], mean airway pressure [MAP] and radiographic grading of severity of RDS. On the contrary, mean concentration of ET-1 in tracheal aspirate was significantly lower in preterms with severe RDS as compared to reference preterms [P <0.01]. A significant positive correlation was found between tracheal aspirate ET- 1 levels and 5 minutes Apgar score, while a significant negative correlation existed between tracheal aspirate ET-1 and MAP. Finally, a significant negative correlation was found between plasma and tracheal aspirate levels of ET-1 [P <0.001] in preterms with RDS, as well as in reference preterms. High plasma ET-1 level is associated with more severe RDS and could be a specific marker for pulmonary endothelial injury that may contribute to the development of elevated pulmonary vascular resistance in this setting. Meanwhile, the association of low ET-1 level in the airway with severe RDS may be attributable to limitation of its stimulant effect on surfaetant secretion and /or the development of airway epithelium; hence, rise in airway ET-1 is indicative of improved pulmonary status in the early course of the disease