Measurement of pulmonary status and surfactant protein levels during dexamethasone treatment of neonatal respiratory distress syndrome

Background - Early postnatal use of dexamethasone in infants with respiratory distress syndrome (RDS) has been shown effectively to improve pulmonary status and to allow early weaning off mechanical ventilation. However, the mechanisms to explain the beneficial effects of dexamethasone in ventilatory dependent preterm infants remain unclear. Methods - A double blind, placebo controlled study was performed to determine the change in pulmonary ventilation of premature infants with RDS as a result of dexamethasone treatment, and to evaluate the effect of dexamethasone on the levels of surfactant-associated proteins A (SP-A) and D (SP-D) in the tracheal fluid from 34 premature infants with RDS and 29 control subjects. Results - Dexamethasone treatment decreased fractional inspired oxygen concentration (FIO₂), arterial carbon dioxide tension (PCO₂), mean airway pressure (MAP), and facilitated successful weaning from mechanical ventilation. SP-A concentrations in the tracheal aspirates were increased at days 7 and 14, and SP-D concentrations were increased during the period from days 3 to 14 in the dexamethasone treated group compared with the control group. However, albumin levels in the tracheal aspirate samples were decreased after dexamethasone treatment over the period from days 3 to 14. There was an inverse correlation between PCO₂ values and SP-A concentrations. Conclusions - These result suggest that early use of dexamethasone can improve pulmonary status and also increase SP-A and SP-D levels in the tracheal fluid in premature infants with RDS.