Systemic inflammatory response syndrome in the trauma intensive care unit:Who is infected?

Background: Systemic inflammatory response syndrome (SIRS) is common in tra uma patients, and infection represents an important and treatable source of SIRS, C-Reactive protein (:CRP), an acute phase protein, is elevated in in fection and discriminates between infected and uninfected patients in other patient populations. Our goal was to examine the ability of CRP and other commonly used markers of infection (maximum temperature [Tmax], and white b lood cell count [WBC]) to distinguish between infectious and noninfectious causes of SIRS. Methods: This was a prospective study of a consecutive series of trauma pat ients who spent greater than 48 hours in the intensive care unit, Studied v ariables included CRP, Tmax, WBC, and culture-proven infection compared wit h standard definitions of infection and the presence of SIRS, The ability o f these variables to correctly classify patients as infected (INF) or not i nfected was examined by using receiver operating characteristic curves. Val ues on the day of infection diagnosis in the INF group and on postadmission day 5 (the mean day of onset of infection in the INP group) in the not inf ected group were used, Multivariate discriminant analysis was used to exami ne the relative contributions of Tmax and CRP in predicting infection. Sign ificance was defined asp < 0.05. Results: Fifty-nine patients were admitted over a 4-month period, Of these, 35 patients (59%) had SIRS at the time of comparison (29 INF, 6 not infect ed), Thirty-three patients (56%) developed an infection, Both CRP and Tmax discriminated between patients with and without infection whereas WBC did n ot (areas under receiver operating characteristic curve: 0.86, 0.81, and 0. 47, respectively), In patients with SIRS, cutoff values of 17 mg/dL for CRP (specificity 100%) and 102 degrees F for Tmax (specificity 83%) were ident ified. CRP added significant discriminatory power to Tmax in determining pr esence of infection in patients with SIRS (p = 0.003), Conclusion: Infection must be presumed to be the source of SIRS in patients with CRP more than 17 mg/dL and Tmax more than 102 degrees F after postinj ury day 4. WBC is not useful in determining the presence of infection.