Microbial infection and the septic response in critical surgical illness. Sepsis, not infection, determines outcome.

The differential roles of infection as a microbial phenomenon and sepsis as a host response were studied in 210 critically ill surgical patients. Infections occurred in 41.4% of all cases and in 82% of nonsurviving patients. Both infection and the expression of a septic response, measured as a sepsis score, were associated with significantly increased intensive care unit morbidity and mortality. Nonsurviving patients with infection had significantly higher sepsis scores than did survivors. Nonsurvivors with sepsis, on the other hand, did not differ from survivors with respect to any variable reflecting infection but did have higher mean sepsis scores. Maximum sepsis scores and sepsis scores on the day of death were similar in patients dying without infection and those dying with uncontrolled infection. The magnitude of the host septic response, independent of the presence, bacteriologic characteristics, or control of infection, is an important determinant of outcome in critical surgical illness.