To investigate the pulmonary effects of
steroid treatment in neonates with
meconium aspiration, 25 10- to 12-d-old piglets were studied for 6 h after an intratracheal bolus of human meconium.
Dexamethasone (0.5 mg/kg) was given in two treatment schedules, either 1 h before (n = 6) or 1 h after meconium instillation (n = 8). Eight piglets served as controls. Three additional piglets were given
dexamethasone without meconium instillation. Pulmonary hemodynamics and oxygenation were followed, and lung tissue samples investigated for signs of
inflammation and ultrastructural injury, including apoptosis. Pulmonary artery pressure and vascular resistance increased after meconium instillation, but this rise was significantly prevented after prophylactic
dexamethasone. This treatment also improved the acutely deteriorated oxygenation of the piglets after meconium insufflation. Prophylactic, but not early,
dexamethasone treatment further protected the lungs from the ultrastructural changes caused by meconium instillation. Additionally, the increase of apoptotic epithelial cell deaths was significantly prevented by both
dexamethasone treatments. These results show that prophylactic
dexamethasone treatment significantly attenuates the early pulmonary hemodynamic deterioration and structural lung damage caused by
meconium aspiration. Further studies on the apoptosis-inhibiting effect of
dexamethasone administration in neonatal lungs exposed to heavy meconium are warranted.