TIMING OF EXOGENOUS SURFACTANT ADMINISTRATION IN A RABBIT MODEL OF ACUTE LUNG INJURY

The purpose of this study was to evaluate early vs. late administratio n of exogenous surfactant in an adult rabbit model of acute lung injur y. Lung injury was induced by repetitive whole lung saline lavage and subsequent mechanical ventilation. Bovine lipid extract surfactant was instilled either 1 (Early) or 4 h (Late) after the last lavage. Anima ls were monitored for 7 h after the last lavage. Although arterial P-O 2 values increased significantly immediately after treatment in both t he Early and Late groups, this improvement was not sustained in the La te group. There was also a higher incidence of pneumothoraxes in the L ate group vs. both the Early group and a nontreated control group. The ratio of poorly functioning small surfactant aggregates to superior f unctioning large aggregates was higher in the Late group compared with the Early group. Morphological analysis revealed that early surfactan t treatment prevented the progression of lung injury over time. We con clude that administration of exogenous surfactant at an early time poi nt in lung injury resulted in superior responses compared with later t reatments.