The development of early-onset ventilator-associated pneumonia after cardiac surgery with cardiopulmonary bypass is associated with toll-like receptor 4 signal transduction pathways.

Abstract

We evaluated the hypothesis that early-onset ventilator-associated pneumonia (VAP) after cardiac surgery with cardiopulmonary bypass (CPB) requires Toll-like receptor 4 (TLR4)-dependent signaling pathways. We enrolled 50 patients undergoing mitral and aortic double valve replacement, collecting left atrial blood samples from all patients preoperatively (T1), when opening the atrial septum (T2), closing the atrial septum (T3), and at the end of CPB (T4). TLR4 expression on monocytes and lymphocytes was detected immediately with flow cytometry. Serum levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-10 (IL-10) were measured using enzyme-linked immunosorbent assays (ELISA). Data from flow cytometry, ELISA, and the clinical outcomes in the two groups were evaluated and compared. Seventeen patients were included for analysis, and assigned to group A (without early-onset VAP, n = 10) and group B (with early-onset VAP, n = 7). TLR4 expression on lymphocytes in group B at T1, T3, and T4 were significantly higher than those in group A. Serum levels of IL-10 in group A at T4 were significantly higher than for group B. We found characteristic patterns in TLR4 expression on lymphocytes in left atrial blood of patients undergoing cardiac surgery with CPB. Our findings clarify the role of TLR4 and its association with the development of postoperative pneumonia.