Routine surveillance blood cultures: their place in the management of critically ill patients

The use of surveillance blood cultures has been advocated as a means to allow earlier detection of septic episodes amongst intensive care patients, and therefore earlier institution of appropriate antibiotic therapy. We compared the results of surveillance cultures and clinically indicated blood cultures for bacterial isolates grown and the influence of culture results on patient management. Blood cultures were obtained from all intensive care unit (ICU) patients over the course of 3 months at a set surveillance time (surveillance group) or according to clinical indications (clinical group). Bacteriological results were compared and real-time chart review performed to assess the influence of the surveillance cultures on patient management, with particular reference to antibiotic therapy. Two hundred and forty-nine blood culture sets were collected over 3 months, 99 in the surveillance group and 150 in the clinical group. A total of 256 bacterial isolates were grown, 95 in the surveillance group and 161 in the clinical group. For the surveillance group 36%, 20%, and 44% of the isolates represented bacteraemia, line colonization and culture contamination, respectively. For the clinical group the distibution was 69%, 7%, and 24% respectively (P<0.001, P<0.01, and P<0.0027 for comparisons of percentages within each classification). On only one occasion was antibiotic therapy started based on the result of a surveillance culture, and on only one occasion was a septic episode detected earlier by a surveillance culture; however, this culture result did not lead to a change in patient management. Surveillance blood cultures are expensive and add very little to the management of patients in the intensive care environment.