Microbial Control in Renal Support for Acute Kidney Injury

Fluids for Continuous Renal Replacement Therapy – an Evaluation of Microbial Integrity

Purpose

We have previously demonstrated widespread microbial contamination in the dialysis and replacement fluid circuits of bicarbonate-buffered, continuous renal replacement therapies (CRRTs). It is not known whether different CRRT fluids have an impact on bacterial activity.

Methods

In this study the in vitro growth and biofilm formation associated with seven strains of bacteria ( Burkholderia cepacia, Escherichia coli, Staphylococcus aureus, Stenotrophomonas maltophilia, Pseudomonas aeruginosa, Pseudomonas fluorescens, and Staphylococcus epidermidis) in five CRRT fluids (Prismocitrate, Monosol S, Accusol 35, tri-sodium citrate and Ci-Ca K2) were studied. The fluids were each inoculated with light and heavy concentrations of each of the bacterial strains and incubated at 22 or 37°C for up to 72 h with and without bacterial growth medium. Bacterial growth was assessed by spectrophotometry. Biofilm formation was assessed by a standard microtiter plate assay.

Results

Unsupplemented fluids did not support bacterial growth or biofilm formation after 72 h incubation. When supplemented with bacterial growth medium, some fluids, in particular Accusol 35, Ci-Ca K2, and tri-sodium citrate, had an inhibitory effect on bacterial growth, although none suppressed growths across the panel of tested organisms.

Conclusions

Different CRRT fluids have different impacts on bacterial growth and biofilm formation, but all remain susceptible to extrinsic contamination.

Initial and extended use of femoral versus nonfemoral double-lumen vascular catheters and catheter-related infection during continuous renal replacement therapy

BACKGROUND

The risk of catheter-related infection or bacteremia, with initial and extended use of femoral versus nonfemoral sites for double-lumen vascular catheters (DLVCs) during continuous renal replacement therapy (CRRT), is unclear.

STUDY DESIGN

Retrospective observational cohort study.

SETTING & PARTICIPANTS

Critically ill patients on CRRT in a combined intensive care unit of a tertiary institution.

FACTOR

Femoral versus nonfemoral venous DLVC placement.

OUTCOMES

Catheter-related colonization (CRCOL) and bloodstream infection (CRBSI).

MEASUREMENTS

CRCOL/CRBSI rates expressed per 1,000 catheter-days.

RESULTS

We studied 458 patients (median age, 65 years; 60% males) and 647 DLVCs. Of 405 single-site only DLVC users, 82% versus 18% received exclusively 419 femoral versus 82 jugular or subclavian DLVCs, respectively. The corresponding DLVC indwelling duration was 6±4 versus 7±5 days (P=0.03). Corresponding CRCOL and CRBSI rates (per 1,000 catheter-days) were 9.7 versus 8.8 events (P=0.8) and 1.2 versus 3.5 events (P=0.3), respectively. Overall, 96 patients with extended CRRT received femoral-site insertion first with subsequent site change, including 53 femoral guidewire exchanges, 53 new femoral venipunctures, and 47 new jugular/subclavian sites. CRCOL and CRBSI rates were similar for all such approaches (P=0.7 and P=0.9, respectively). On multivariate analysis, CRCOL risk was higher in patients older than 65 years and weighing >90kg (ORs of 2.1 and 2.2, respectively; P<0.05). This association between higher weight and greater CRCOL risk was significant for femoral DLVCs, but not for nonfemoral sites. Other covariates, including initial or specific DLVC site, guidewire exchange versus new venipuncture, and primary versus secondary DLVC placement, did not significantly affect CRCOL rates.

LIMITATIONS

Nonrandomized retrospective design and single-center evaluation.

CONCLUSIONS

CRCOL and CRBSI rates in patients on CRRT are low and not influenced significantly by initial or serial femoral catheterizations with guidewire exchange or new venipuncture. CRCOL risk is higher in older and heavier patients, the latter especially so with femoral sites.