The presence of circulating endotoxin is common during sepsis but its prognostic value is poor. We hypothesized that this lack of correlation with outcome could be related in part to the presence of circulating antiendotoxin antibodies. In a 14-bed medical intensive care unit, in an 821-bed tertiary teaching hospital, we prospectively assessed endotoxin and antiendotoxin antibodies in patients with severe sepsis or septic shock. Blood samples for the determination of circulating endotoxin and antiendotoxin antibodies were drawn when severe sepsis or septic shock were diagnosed (day 0) and then on day 1, day 2, and day 4. Daily measurements of antiendotoxin antibodies did not discriminate survivors from nonsurvivors. No antibody depletion was observed. However, during follow-up, the antiendotoxin immunoglobulin (Ig)M antibody level increased among survivors but decreased among nonsurvivors (51.2 vs -44.8 MU/mL, P=007). Circulating endotoxin was detectable among 9 of 17 patients on inclusion but neither the basal value nor sequential measurements correlated with outcome. These results suggest that during severe sepsis and septic shock, circulating endotoxin is a poor prognostic marker whereas the detection of an increase in IgM antiendotoxin antibody levels could identify survivors. This increase in IgM antibody levels could be attributed to a reactivation of the immune system.
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