Dexamethasone treatment attenuates pulmonary injury in piglet meconium aspiration

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 giv en in two treatment schedules, either 1 h before (n = 6) or 1 h after mecon ium instillation (n = 8). Eight piglets served as controls. Three additiona l piglets were given dexamethasone without meconium instillation. Pulmonary hemodynamics and oxygenation were followed, and lung tissue samples invest igated for signs of inflammation and ultrastructural injury, including apop tosis. Pulmonary artery pressure and vascular resistance increased after me conium instillation, but this rise was significantly prevented after prophy lactic 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 ult rastructural changes caused by meconium instillation. Additionally, the inc rease of apoptotic epithelial cell deaths was significantly prevented by bo th dexamethasone treatments. These results show that prophylactic dexametha sone treatment significantly attenuates the early pulmonary hemodynamic det erioration and structural lung damage caused by meconium aspiration. Furthe r studies on the apoptosis-inhibiting effect of dexamethasone administratio n in neonatal lungs exposed to heavy meconium are warranted.