Risk of catheter-related bloodstream infection: higher in more severe patients?

Introduction

Vascular devices are associated with the risk of catheter-related bloodstream infection (Cr-BSI). The aim of this study was to evaluate the risk of Cr-BSI in our ICU.

Methods

A nonconcurrent cohort study at an adult, 11-bed medical/surgical unit, between 1 January and 31 December 2005. Data were retrospectively reviewed from clinical records and bacteriological data concerning the presence of central venous (CVC) or haemodialysis catheter (HDC) colonization and Cr-BSI (no data on arterial catheters) were collected. Catheter insertion and dressing of the insertion site were done according to CDC guidelines for Cr-BSI prevention. Diagnosis of Cr-BSI required microbial concordance between a culture of the removed catheter and a separate percutaneously drawn blood culture, and the exclusion of other overt source of bacteraemia. Intravascular devices were cultured for evidence of colonization whenever there was clinical suspicion of Cr-BSI. Severity scores (SOFA, SAPS II) were assessed and analysed facing Cr-BSI data.

Results

During the study period, 378 patients were admitted to the ICU (59% male; mean age 58.3 ± 19.8 years), the mean SOFA score (admission) being 7.9 ± 4.0 and the mean SAPS II (at 24 hours) being 47.6 ± 19.7. In the 266 patients with CVC, the total duration of implantation was 3.190 days, with a mean duration of CVC placement/patient of 12 days. Positive cultures of CVC were found in 18 patients (6.8%). The incidence density of positive catheter cultures was 6.3/1,000 days of CVC use. CVC-related BSI was diagnosed in 5 patients, the risk of CVC-related BSI being 1.6/1,000 days of CVC use. Fifty-two patients also had a HDC. Positive cultures of HDC occurred in two of these patients (3.8%), none of them with Cr-BSI. The isolated microorganisms from CVC and HDC were typical skin bacteria, excluding two cases with catheter colonization in patients with other overt sources of bacteraemia. The mean SOFA score in patients with positive catheter cultures was 10.2 ± 3.1, the mean SAPS II was 63 ± 19.6 and the mean catheter placement duration in these patients was 32.1 ± 15.7 days. The overall ICU mortality rate was 20.1%, being 40% in the subgroup of patients in whom Cr-BSI was diagnosed.

Conclusion

Preventing Cr-BSI is important, but special care is particularly relevant in patients with higher SAPS II scores and a longer duration of catheter placement. More studies are needed to confirm this possible higher risk of Cr-BSI in this more severe patient subgroup.