N-acetylcysteine alleviates the meconium-induced acute lung injury

Meconium aspiration in newborns causes lung inflammation and injury, which may lead to meconium aspiration syndrome (MAS). In this study, the effect of the antioxidant N-acetylcysteine on respiratory and inflammatory parameters were studied in a model of MAS. Oxygen-ventilated rabbits were intratracheally given 4 mL/kg of meconium (25 mg/mL) or saline. Thirty minutes later, meconium-instilled animals were administered N-acetylcysteine (10 mg/kg; i.v.), or were left without treatment. The animals were oxygen-ventilated for additional 5 h. Ventilatory pressures, oxygenation, right-to-left pulmonary shunts, and leukocyte count were measured. At the end of experiment, trachea and lung were excised. The left lung was saline-lavaged and a total and differential count of cells in bronchoalveolar lavage fluid (BAL) was determined. Right lung tissue strips were used for detection of lung edema (expressed as wet/dry weight ratio) and peroxidation (expressed by thiobarbituric acid-reactive substances, TBARS). In lung and tracheal strips, airway reactivity to acetylcholine was measured. In addition, TBARS and total antioxidant status were determined in the plasma. Meconium instillation induced polymorphonuclear-derived inflammation and oxidative stress. N-acetylcysteine improved oxygenation, reduced lung edema, decreased polymorphonuclears in BAL fluid, and diminished peroxidation and meconium-induced airway hyperreactivity compared with untreated animals. In conclusion, N-acetylcysteine effectively improved lung functions in an animal model of MAS.