What is Catheter Locking During Hemodialysis?
Catheter locking is a procedure performed at the end of each dialysis session where a solution (typically containing an anticoagulant like heparin or citrate) is instilled into each lumen of the central venous catheter and left to dwell until the next dialysis session to maintain catheter patency and prevent infection. 1
Purpose and Mechanism
Catheter lock solutions serve two primary functions:
- Prevent thrombosis and catheter dysfunction by filling the catheter lumen with anticoagulant solution that prevents blood from clotting within the catheter between dialysis sessions 1, 2
- Reduce catheter-related bloodstream infections (CRBSI) when antimicrobial agents are added to the lock solution, as these high-concentration solutions can eradicate biofilm-forming bacteria within the catheter lumen 1
Standard Locking Procedure
The technique follows a specific sequence at the end of each dialysis session:
- Flush each catheter lumen thoroughly with normal saline (5-10 mL) using a turbulent flushing technique to clear residual blood and optimize patency 1, 3
- Instill the lock solution into each lumen in a volume that matches the internal catheter volume (typically 2-5 mL per lumen) 1
- Clamp the catheter and leave the solution dwelling until the next dialysis session 1
- The lock solution is renewed after every dialysis session (typically 3 times per week for most hemodialysis patients) 1
Types of Lock Solutions
Standard Anticoagulant Locks
- Heparin 1,000 units/mL is the recommended concentration by the American Society of Diagnostic and Interventional Nephrology, balancing catheter patency with lower systemic anticoagulation risk 3, 4, 2
- Low-concentration citrate (<5%) is an alternative that provides both anticoagulant and antimicrobial properties while minimizing systemic effects 3, 4, 5
Antibiotic Lock Therapy (for Treatment of CRBSI)
When catheter-related bloodstream infection occurs, antibiotic lock therapy becomes a therapeutic intervention rather than prophylaxis:
- Antibiotic lock must always be combined with systemic antimicrobial therapy, never used alone, with both regimens administered for 10-14 days 1
- The antibiotic is combined with heparin at supratherapeutic concentrations (100-1000 times the MIC) and instilled into each catheter lumen at the end of each dialysis session 1
- Success rates vary by pathogen: 87-100% for gram-negative infections, 75-84% for coagulase-negative staphylococci, but only 40-55% for S. aureus 1
Critical Distinctions
Prophylactic locking (routine maintenance) differs fundamentally from therapeutic antibiotic lock therapy (treatment of active infection). The former uses standard anticoagulants to prevent complications, while the latter adds high-concentration antibiotics to treat established CRBSI while attempting catheter salvage 1, 6
Common Pitfalls to Avoid
- Do not exceed the internal catheter volume when instilling lock solution, as overflow into systemic circulation can cause unintended anticoagulation 4, 2
- Avoid confusing heparin concentration with total dose: some protocols erroneously use 12,500 units per lumen when they should specify concentration (e.g., 1,000 units/mL) 3
- For CRBSI due to S. aureus or Candida, catheter removal is recommended rather than attempting salvage with antibiotic lock therapy, unless no alternative catheter site exists 1
- Antibiotic lock therapy only addresses intraluminal infection and will not eradicate extraluminal or tunnel infections 1