Heparin Dosing in Peritoneal Dialysis
For peritoneal dialysis, add 500 units of heparin per liter of dialysate to prevent intraperitoneal fibrin formation without causing systemic anticoagulation. 1
Recommended Dosing Protocol
Standard Concentration
- Add 500 units/L (0.5 units/mL) of unfractionated heparin to each peritoneal dialysis bag 1
- This concentration effectively prevents fibrin precipitation in the dialysate while maintaining negligible systemic absorption 1
- Alternative dosing of 2.5-5 units/mL has been studied, though 500 units/L represents the most validated approach 2
Mechanism and Rationale
- The low antithrombin III (AT-III) concentration in dialysate (approximately 0.44 mg/dL, only 1.5% of plasma levels) is sufficient to inhibit thrombin activity when accelerated by heparin 1, 2
- Intraperitoneal heparin dramatically reduces fibrinopeptide A (a marker of fibrin formation) in dialysate from 155.8 ng/mL to 8.5 ng/mL 1
- Plasma fibrinopeptide A levels also decrease from 63.2 ng/mL to 4.9 ng/mL, indicating reduced systemic coagulation activation 1
Pharmacokinetics and Safety
Systemic Absorption
- No detectable heparin activity appears in plasma even after 52 hours of continuous intraperitoneal administration at 500 units/L 1
- The half-life of heparin activity in dialysate is only 0.5-2 hours, with activity dropping to 0.5-1.4 units/mL by 6 hours 2
- Whole blood clotting time remains unaffected due to minimal transfer to plasma 2
Clinical Indications for Use
- Most beneficial at the initiation of CAPD when fibrin formation risk is highest 2
- Essential during peritonitis episodes when intraperitoneal AT-III levels are relatively increased 2
- Prevents catheter dysfunction from fibrin sheath formation 3
Important Clinical Considerations
When to Use Heparin in PD Bags
- Routine use is not necessary for all exchanges in stable patients 2
- Reserve for situations with increased fibrin formation risk: new catheter placement, peritonitis, bloody dialysate, or catheter malfunction 2
Monitoring
- No aPTT monitoring required due to lack of systemic anticoagulation 1
- Visual inspection of dialysate for fibrin strands or cloudiness is sufficient 1
Common Pitfalls to Avoid
- Do not use hemodialysis heparin dosing protocols (which require 5000 unit bolus plus 1500 units/hour infusion) for peritoneal dialysis 4
- Avoid confusion between catheter flush solutions (which use 500-5000 units for central venous catheters) and intraperitoneal dialysate dosing 3
- Higher concentrations (>5 units/mL) provide no additional benefit and waste medication 2