Aerosolized surfactant in lung-lavaged adult rats: factors influencing thetherapeutic response

Objective: To evaluate the effect of aerosolized modified natural surfactan t in adult rats with respiratory failure. Methods: Lung-lavaged adult rats were treated with aerosolized surfactant, aerosolized saline or a bolus of surfactant. Surfactant was labelled with d imyristoylphosphatidylcholine (DMPC) and human serum albumin was given intr avenously for evaluation of lung protein leakage. Blood gases and dynamic c ompliance were measured intermittently At the end of ventilation, the lungs were either fixed by vascular perfusion for histological examination or wa shed for determination of total phospholipids, DMPC and human albumin in th e lavage fluid. Results: Treatment with bolus surfactant led to a quick and sustained resto ration of pre-lavage blood gas values in most animals. The response to aero solized surfactant varied considerably, with an overall moderate improvemen t of gas exchange. The saline-treated group failed to show any significant recovery of lung function. No histopathological differences were found betw een any of the groups. On average 0.46% of total administered aerosolized s urfactant could be recovered. Vascular-to-alveolar leakage of human albumin averaged 11%, with no significant differences between the groups. Final va lues fur PaO2 were significantly correlated with total phospholipids in the lavage fluid, and inversely related to the vascular-to-alveolar leakage of albumin. Conclusion: Neither bolus nor aerosolized surfactant influenced lung morpho logy. Nebulized surfactant improved lung function but the effect was inferi or to that obtained with bolus surfactant, and the outcome depended on the balance between the combined pool size of exogenous and endogenous surfacta nt and the vascular-to-alveolar leakage of serum protein. (C) Acta Anaesthe siologica Scandinavica 44 (2000).