Abstract
IntroductionTo estimate the incidence of intensive care unit (ICU)-acquired bloodstream infection (BSI) and its independent effect on hospital mortality.MethodsWe retrospectively studied acquisition of BSI during admissions of >72 hours to adult ICUs from two university-affiliated hospitals. We obtained demographics, illness severity and co-morbidity data from ICU databases and microbiological diagnoses from departmental electronic records. We assessed survival at hospital discharge or at 90 days if still hospitalized.ResultsWe identified 6339 ICU admissions, 330 of which were complicated by BSI (5.2%). Median time to first positive culture was 7 days (IQR 5-12). Overall mortality was 23.5%, 41.2% in patients with BSI and 22.5% in those without. Patients who developed BSI had higher illness severity at ICU admission (median APACHE III score: 79 vs. 68, P < 0.001). After controlling for illness severity and baseline demographics by Cox proportional-hazard model, BSI remained independently associated with risk of death (hazard ratio from diagnosis 2.89; 95% confidence interval 2.41-3.46; P < 0.001). However, only 5% of the deaths in this model could be attributed to acquired-BSI, equivalent to an absolute decrease in survival of 1% of the total population. When analyzed by microbiological classification, Candida, Staphylococcus aureus and gram-negative bacilli infections were independently associated with increased risk of death. In a sub-group analysis intravascular catheter associated BSI remained associated with significant risk of death (hazard ratio 2.64; 95% confidence interval 1.44-4.83; P = 0.002).ConclusionsICU-acquired BSI is associated with greater in-hospital mortality, but complicates only 5% of ICU admissions and its absolute effect on population mortality is limited. These findings have implications for the design and interpretation of clinical trials.
Highlights
To estimate the incidence of intensive care unit (ICU)-acquired bloodstream infection (BSI) and its independent effect on hospital mortality
BSI was associated with an 18.7% increase in crude hospital mortality from 22.5% to 41.2%
We found that the collective effect of BSI on survival was statistically related to infections with candida, S. aureus, and Gram-negative bacilli, while infections with coagulase-negative staphylococci and enterococci were not significantly associated with increased risk of death in our dataset
Summary
To estimate the incidence of intensive care unit (ICU)-acquired bloodstream infection (BSI) and its independent effect on hospital mortality. Nosocomial bloodstream infection (BSI) is a serious and potentially preventable complication of hospitalization and has been estimated to be the eighth leading cause of death in the USA [1]. Ill patients are vulnerable to hospital-acquired infections [2,3], which are two to seven times more common in the ICU [4,5,6,7] and can account for approximately half of all hospital-acquired BSI [8]. Our ability to demonstrate the survival benefit of any intervention to prevent BSI will be dependent on the baseline incidence of BSI, the mortality rate of patients who develop it, and, crucially, on its true independent influence on outcome once correction has been made for other markers of illness severity
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