The effect of inhalation of nebulized steroid on the acid aspiration syndrome.

The effects of acid aspiration on lung mechanics, gas exchange, haemodynamics and lung water, and their modification by nebulized dexamethasone were studied in 10 dogs. Each dog received 0.1 N HCl pH of 1.0 (15 ml/l vital capacity), instilled down the tracheal tube. PEEP 0.98 kPa (10 cm H2O) was introduced 20 minutes after aspiration and was continued until the completion of experiment. Treated animals (N = 5) received dexamethasone 5 mg . kg-1 by continuous nebulization over a two hour period starting 20 minutes after aspiration. Untreated (N = 5) animals received nebulized saline. Measurements were taken before aspiration and at 20 minutes 2.5 and 5.0 hours after aspiration. Red blood cells labelled with 51Cr were injected before sacrifice. After sacrifice multiple lung samples were taken for measurement of pulmonary extravascular water (PEW) by the gravimetric technique. Acid aspiration caused significant changes in lung volumes, PaO2, and intrapulmonary shunt. Pulmonary extravascular water was 6.16 +/- 0.93 ml/g dry tissue in treated and 6.47 +/- 0.60 ml/g dry tissue in untreated animals. These results indicate the presence of severe pulmonary oedema. There were no significant differences in any measured parameter between treated and untreated animals. We conclude that nebulized dexamethasone is of no value in treatment of the acute changes induced by acid aspiration.