Increased alveolar epithelial permeability with acid aspiration: the effects of high-dose steroids

Using the in vivo, liquid-filled dog lung model, we found that aspriation of acid with a pH of 2.5 or less led to increased alveolar epithelial permeability for albumin (molecular weight, 69,000 daltons; molecular radius, 35 a) and exogenously administered, polydispersed dextrans (molecular weight, 150,000 to 170,000 daltons: approximately molecular radius, 100 a). This increased permeability occurred with a large-volume (3 to 5 ml/kg) or small-volume (1 to 1.5 ml/kg) aspirate and with acid nebulization (1 to 1.5 ml/kg). When animals were either pretreated (30 min before aspiration) or post-treated (30 min after aspiration) with 30 mg of methylprednisolone/kg of body weight, there was no improvement in the increased permeability associated with acid aspiration. We conclude that, acutely, steroids have no effect on the increased alveolar epithelial permeability associated with acid aspiration.