Heparin Dosage Regimens for Dialysis
For patients undergoing hemodialysis, the recommended heparin regimen is an initial bolus of 25-30 units/kg followed by an infusion rate of 1,500-2,000 units/hour, adjusted based on coagulation monitoring. 1
Standard Dosing Approaches
Heparin administration during hemodialysis is critical to prevent clot formation in the extracorporeal circuit while minimizing bleeding risk. There are several approaches:
Continuous Infusion Method
- Initial bolus: 25-30 units/kg
- Maintenance infusion: 1,500-2,000 units/hour
- Timing: Continue until 30-45 minutes before the end of dialysis session
- Monitoring: Adjust based on aPTT or anti-Xa levels 1, 2
Bolus Method
- Initial bolus: 5,000 units IV at the start of dialysis
- Second bolus: 2,000-3,000 units after 2 hours (if needed)
- Advantage: Simpler administration, may be more effective at maintaining adequate anticoagulation 3
Low-Dose Protocol
- Initial bolus: 15-20 units/kg
- Maintenance: 500 units/hour
- Benefit: Reduced bleeding risk while maintaining dialysis efficacy 4
Monitoring and Adjustment
Proper monitoring is essential to balance anticoagulation efficacy with bleeding risk:
- Target aPTT: 1.5-2.5 times normal (equivalent to heparin level of 0.2-0.4 U/mL) 2
- Anti-Xa level: 0.3-0.7 U/mL when available 2
- Frequency: Check coagulation parameters at 30 minutes after starting dialysis and at the end of the session 3
Use this adjustment protocol based on aPTT results:
| aPTT (seconds) | aPTT (× control) | Action |
|---|---|---|
| <35 | <1.2 | 80 units/kg bolus; increase infusion by 4 units/kg/hour |
| 35-45 | 1.2-1.5 | 40 units/kg bolus; increase infusion by 2 units/kg/hour |
| 46-70 | 1.5-2.3 | No change (therapeutic range) |
| 71-90 | 2.3-3.0 | Reduce infusion by 2 units/kg/hour |
| >90 | >3.0 | Stop infusion for 1 hour, then reduce rate by 3 units/kg/hour |
Special Considerations
Patients with Increased Bleeding Risk
- Reduced dosing: Consider the low-dose protocol (15-20 units/kg loading, 500 units/hour maintenance) 4
- Regional heparinization: Administration of heparin to the arterial line with protamine neutralization to the venous return may be considered in high bleeding risk patients 5
Patients with Renal Impairment
- Standard unfractionated heparin is preferred over LMWH in severe renal impairment as it doesn't require dose adjustment for renal function 6
Visual Circuit Assessment
- Regularly inspect the extracorporeal circuit for visible clotting
- Pay particular attention to arterial and venous bubble traps, which may show early signs of inadequate anticoagulation 7
Common Pitfalls and Caveats
Overdosing: Excessive heparin increases bleeding risk, particularly at vascular access sites. The risk increases with age >60 years, hepatic dysfunction, and multiple comorbidities 2
Underdosing: Insufficient heparin leads to clotting in the dialysis circuit, reduced dialysis efficiency, and potential blood loss. Signs include visible fibrin strands or clots in the circuit 8
Heparin-Induced Thrombocytopenia (HIT): Monitor platelet counts regularly between days 4-14 of therapy. If HIT is suspected, switch to alternative anticoagulants like argatroban or danaparoid 2
Failure to adjust for patient factors: Weight, baseline coagulation status, and comorbidities should influence initial dosing
Inadequate monitoring: Relying solely on visual inspection without laboratory monitoring can lead to suboptimal anticoagulation
The weight-based dosing approach (25-30 units/kg bolus followed by 1,500-2,000 units/hour) has been shown to be more effective than fixed dosing in maintaining appropriate anticoagulation levels and reducing complications during dialysis 1, 8.