Altered Alveolar Surfactant Is an Early Marker of Acute Lung Injury in Septic Adult Sheep

The purpose of this study was to characterize changes in the endogenous surfactant system in adult sheep rendered septic via cecal ligation and perforation (CLP). Forty-eight hours after CLP, septic animals had significant increases in mean pulmonary artery pressure (PAP) (p < 0.01), cardiac index (CI) (p < 0.01), and arterial lactate (p < 0.05) values compared with their respective baseline values, while the same measurements in a sham-operated control group did not change significantly. The changes in the septic group were associated with significantly lower PaO2 (p < 0.05) and alveolar to arterial (A-a) oxygen gradient values (p < 0.01) at 48 h compared with baseline measurements. No changes in oxygenation occurred within the sham-operated group. Surfactant phospholipid (PL) composition and surface activity measurements of isolated alveolar surfactant aggregate forms were similar for the two groups at 48 h. However, the ratio of poorly functioning small aggregate forms (SA) to superior functioning larg...