Alterations in pulmonary surfactant during the course of sepsis-induced ARDS predisposition

To test the hypothesis that alterations of the endogenous surfactant system persist and contribute to lung dysfunction in sepsis-induced ARDS predisposition, we analyzed sequentially obtained bronchoalveolar lavage fluid (BALF) from a homogeneous group of thirteen postoperative sepsis-induced ARDS at-risk patients. Beginning no later than 12 h after risk identification, we continued to analyze BALF for the biochemical composition and surface properties of endogenous surfactant at 48 h intervals for seven days. Eleven non-smoking healthy patients prior to minor elective surgery served as control group. Five at-risk patients developed ARDS during the study period. In at-risk patients who did not develop ARDS the mean (± SE) percentage of PMN (p < 0.001), SA/LA ratio (p < 0.05), and γmin (p < 0.001) was elevated, whereas SP-A content (p < 0.01) was decreased compared to the control group. The paO₂/FiO₂ was 271.3 ± 12.0 and P(A-a)O₂ was 154.1 ± 19.5 mmHg. Static compliance of the respiratory system was inversely related to γmin. During the time course SP-A remained significantly decreased and γmin significantly elevated at every point of measurement compared to the control group. Our data show that profound alterations in endogenous surfactant not only occure initially but also persist in septic patients during the early clinical course of their ARDS predisposition, and correspond with lung dysfunction even prior to the possible development of the syndrome.