Supplemental intraoperative oxygen augments antimicrobial and proinflammatory responses of alveolar macrophages

Background: The first goal was to test the hypothesis that 100% inspired oxygen maintained for approximately 8 h intraoperatively is not associated with impaired pulmonary oxygenation, The authors also tested the hypothesis that intraoperative inhalation of 100% oxygen augments proinflammatory and antimicrobial responses of alveolar macrophages during anesthesia and surgery. Methods: The authors studied patients administered 100% oxygen (n = 30) and 30% oxygen (n = 30) during propofolfentanyl general anesthesia. Alveolar macrophages were harvested by bronchoalveolar lavage immediately, 2, 4, and 6 h after induction of anesthesia, and at the end of surgery,The authors measured "opsonized" and "unopsonized" phagocytosis and microbicidal activity. RNA was extracted from harvested cells and cDNA was synthesized. The expression of interleukin(IL)-1 beta, IL-6, IL-8, interferon-gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha) was measured by semiquantitative polymerase chain reaction. Results: Gene expression of all proinflammatory cytokines except IL-6 increased fourfold to 20-fold over time in both groups. However, expression of TNF-alpha and IL-8, IFN-gamma, and IL-6 and IL-1 beta was 2-20 times greater in patients administered 100% than in those administered 30% oxygen. Unopsonized and opsonized phagocytosis and microbicidal activity decreased progressively, with the decreases being nearly twice as great during inhalation of 30% oxygen versus 100% oxygen. Conclusion: Inhalation of 100% oxygen improved intraoperative decreases in phagocytic and microbicidal activity possibly because expression of proinflammatory cytokines was augmented. These data therefore suggest that intraoperative inhalation of 100% oxygen augments antimicrobial and proinflammatory responses in alveolar macrophages during anesthesia and surgery.