Incidence of bacteremia at the time of ICU admission and its impact on outcome.

Context: Blood culture is routinely taken at the time of admission to the intensive care unit (ICU) for patients suspected to have infection. We undertook this study to determine the incidence of bacteremia at the time of ICU admission and to assess its impact on the outcome. Methods: Retrospective cohort study from all the admissions in ICU, in whom blood cultures sent at the time of admission were analyzed. Data regarding patient demographics, probable source of infection, previous antibiotic use and ICU course was recorded. Severity of illness on admission was assessed by acute physiology and chronic health evaluation II score. Statistical Analysis: Qualitative data were analyzed using Chi-square or Fisher Exact test and quantitative data were analyzed using Student's t -test. Primary outcome measure was ICU mortality. Results: Of 567 patients, 42% patients were on antibiotics. Sixty-four percent of the patients were direct ICU admission from casualty, 10.76% were from wards and 6.17% from other ICUs, and 19.05% were transfers from other hospitals. Blood cultures were positive in 10.6% patients. Mortality was significantly higher in patients with positive blood cultures (45% vs. 13.6%; P =0.000). On univariate analysis, only previous antibiotic use was statistically associated with higher mortality ( P =0.011). Bacteremic patients who were already on antibiotics had a significantly higher mortality (OR 12.9, 95% CI: 1.6-100). Conclusions: Blood cultures may be positive in only minority of the patients with suspected infection admitted to ICU. Nevertheless, the prognosis of those patients with positive blood culture is worse, especially if culture is positive in spite of the patient being on antibiotics.