title: Loss of antimicrobial effect of trisodium citrate due to 'lock' spillage from haemodialysis catheters.
abstract: BACKGROUND
  Due to its reported antimicrobial effects, hypertonic citrate (46.7%) is a widely used catheter lock solution, but following instillation, citrate inevitably spills into the systemic circulation. This process is mainly driven by hydraulic effects during instillation and density differences between blood and lock solution. Hence, in haemodialysis catheters, intra-luminal citrate concentration ranges from 0% (at the tip in catheters with side holes), 3% (between the side holes and the highest point of the catheter) to 46.7% (at the Luer end) with possible differences in antimicrobial effects. We investigated in vitro the antimicrobial effect of pure citrate 46.7%, citrate 46.7% diluted with saline and blood to a net concentration of 3% (=citrate 3%), and of citrate-free blood, simulating in vivo conditions in different catheter sections.
  
  
  METHODS
  Time-kill studies measuring the antimicrobial effect of citrate 46.7%, citrate 3% and citrate-free blood were performed with overnight cultures of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus).
  
  
  RESULTS
  Citrate 46.7% reduced the number of E. coli by 2 log units but after 24 h, 10(6) CFU/mL were still present. Citrate 3% and citrate-free blood had no antimicrobial effect on E. coli. Citrate 46.7%, citrate 3% and citrate-free blood had scarce antimicrobial effect on S. aureus within 24 h.
  
  
  CONCLUSIONS
  Spillage of catheter lock solution leading to reduced intra-luminal citrate concentrations considerably reduces the antimicrobial effect of citrate 46.7% on E. coli. As none of the solutions tested had relevant antimicrobial effect on S. aureus, the antimicrobial effect of 46.7% citrate lock solution in vivo has to be seriously questioned.
authors: Clinical Division of Nephrology, Department of Internal Medicine, Medical University of Graz, Graz, Austria.
authors: Gernot
authors: G
authors: Schilcher
authors: Daniel
authors: D
authors: Schneditz
authors: Werner
authors: W
authors: Ribitsch
authors: Joerg H
authors: JH
authors: Horina
authors: Martin
authors: M
authors: Hoenigl
authors: Thomas
authors: T
authors: Valentin
authors: Alexander R
authors: AR
authors: Rosenkranz
authors: Robert
authors: R
authors: Krause
mesh_terms: D000925:Anticoagulants / Q000494:pharmacology; D055499:Catheter-Related Infections / Q000188:drug therapy* / Q000209:etiology; D002408:Catheters, Indwelling / Q000009:adverse effects* / Q000382:microbiology; D002951:Citrates / Q000494:pharmacology*; D006801:Humans; D006435:Renal Dialysis / Q000009:adverse effects* / Q000295:instrumentation; D017211:Treatment Failure
chemical_list: D000925:Anticoagulants; D002951:Citrates; C514290:trisodium citrate
keywords: catheter-related bloodstream infection; central venous catheter; lock solution; lock spillage; trisodium citrate