Exposure to Bacteroides fragilis endotoxin during cardiac surgery

Although endotoxemia has been observed during cardiac surgery, the identity of endotoxins to which patients are exposed is unknown. We tested the hypo thesis that antibodies to Bacteroides fragilis tan anaerobic gut commensal and a common pathogen) decrease during cardiac surgery, thereby reflecting systemic exposure to this type of endotoxin. Serum antiendotoxin antibody l evels were measured in 55 patients during routine cardiac surgery at the fo llowing times: Preoperatively, Pre-CPB (immediately before initiation of ca rdiopulmonary bypass [CPB]), Pre-CPB +5 (5 min after initiation of CPB), an d End tend of surgery). Antiendotoxin antibody levels were determined by us ing enzyme-linked immunosorbent assay. Total immunoglobulin M (IgM) levels were measured by using laser nephelometry and decreases in total IgM levels were used to control changes in antiendotoxin antibody levels attributable to hemodilution. Median (interquartile range) hemodilution corrected IgM a nti-B fragilis antibody levels decreased by 12% (5%-20%) from Preoperativel y to End of surgery (P < 0.001). In contrast, median hemodilution corrected anti-B fragilis antibody levels did not change significantly from Pre-CPB to Pre-CPB +5, validating the correction for hemodilution. Immunoglobulin G anti-B fragilis antibody levels and IgM and immunoglobulin G anticore anti body levels decreased similarly during surgery. Intraoperatively, levels of anti-B fragilis endotoxin antibodies decreased significantly out of propor tion to hemodilution. These results suggest that cardiac surgical patients are exposed to B fragilis endotoxin. implications: We prospectively measure d hemodilution-corrected antiendotoxin antibody levels in 55 cardiac surgic al patients. We observed significant decreases in hemodilution-corrected le vels of antibody to both Bacteroides fragilis and the core of endotoxin.