How do you manage clotting during hemodialysis?

Managing Clotting During Hemodialysis

Unfractionated heparin (UFH) remains the standard anticoagulant for hemodialysis, administered as an initial bolus of 25-50 units/kg followed by continuous infusion of 500-1500 units/hour, with the infusion stopped during the final hour to minimize bleeding risk. 1, 2, 3

Standard Anticoagulation Protocol

Unfractionated Heparin Administration

• Initial bolus: 25-50 units/kg IV over 10 minutes before connecting the patient to the circuit 1, 2, 3
• Continuous infusion: 500-1500 units/hour during the dialysis session 1, 2
• Timing adjustment: Stop the infusion 30-60 minutes before the end of the 4-hour session to allow anticoagulant effect to dissipate and minimize post-dialysis bleeding 4
• UFH requires no dose adjustment for renal impairment as it is metabolically cleared by the liver and not removed by dialysis 1, 2

Monitoring Strategy

• Routine outpatient hemodialysis does NOT require laboratory monitoring 2, 5
• Visual inspection of the dialyzer header and venous chamber for clot formation guides dose adjustments in most patients 5, 6
• When laboratory monitoring is indicated (extremes of body weight, repeated clotting or bleeding), target aPTT should be 1.5-2.5 times normal, corresponding to anti-Factor Xa levels of 0.35-0.70 IU/mL 2, 3

Alternative Anticoagulation for High Bleeding Risk

Regional Citrate Anticoagulation

Regional citrate is the preferred alternative for patients at high bleeding risk or those who cannot receive heparin, as it provides anticoagulation limited to the extracorporeal circuit without systemic effects. 7, 1, 8

• Citrate demonstrates similar efficacy to heparin with superior safety profile, including reduced bleeding and reduced risk of HIT 7
• More cost-effective than alternative non-heparin anticoagulants 7

Managing Heparin-Induced Thrombocytopenia (HIT)

Acute HIT Requiring Dialysis

For patients with acute HIT, use argatroban as the first-line alternative anticoagulant. 7, 1

• Argatroban dosing: 250 μg/kg bolus for intermittent hemodialysis or 100 μg/kg for continuous hemodialysis, followed by continuous infusion 1, 2
• Argatroban is ideal because it lacks renal clearance and is minimally removed by high-flux dialysis membranes 1
• Demonstrates low rates of new thrombosis (0-4%) and major bleeding (0-6%) 1
• Alternative agents: Danaparoid (3,750 units bolus if weight ≥55 kg, 2,500 units if <55 kg) or bivalirudin, though these have more limitations 7, 1

Subacute or Remote HIT

For patients with subacute HIT A, subacute HIT B, or remote HIT who require anticoagulation only for the dialysis circuit, regional citrate is preferred over heparin or other non-heparin anticoagulants. 7

Troubleshooting Recurrent Clotting

When Standard Heparin Fails

If clotting occurs despite standard UFH dosing:

1. Increase heparin dose incrementally: Add 500-1000 units to the bolus or increase infusion rate by 250-500 units/hour 6
2. Ensure adequate mixing: Administer the bolus a few minutes before connecting the patient to optimize heparin distribution, as heparin binds to plasma proteins and requires thorough mixing 6
3. Consider inflammatory states: COVID-19 and other inflammatory conditions increase filter clotting and may require higher heparin doses or therapeutic anticoagulation 1
4. Evaluate for fibrin sheath formation: If pharmacologic therapy fails, mechanical interventions (catheter exchange, fibrin sheath stripping, or disruption) may be necessary 7

Low-Dose Strategies for Bleeding Risk

For patients with moderate bleeding risk who cannot use regional citrate:

• Heparin with albumin and citrate-containing dialysate (HAC): Reduces heparin exposure while maintaining circuit patency 9
• Heparin-coated filters (Evodial®): Minimizes systemic heparin administration, though may reduce dialysis adequacy 9
• Avoid single heparin bolus without priming, as this has the highest rate of premature dialysis interruption (33%) 9

Critical Pitfalls to Avoid

• Do not use LMWHs without anti-Xa monitoring in dialysis patients: LMWHs are contraindicated or require significant dose adjustment when creatinine clearance <30 mL/min, with bleeding risk up to twice as high in severe renal impairment 1
• Avoid rivaroxaban and dabigatran for systemic anticoagulation: These agents show increased major bleeding risk compared to warfarin in hemodialysis patients 1
• Do not use low-dose prophylactic anticoagulation (warfarin 1 mg daily, LMWH) to prevent catheter thrombosis: Inadequate evidence supports routine use, and risks may outweigh benefits 7
• When drawing pre-dialysis labs from catheters: Withdraw and discard 10 mL (adults) or 3-5 mL (pediatrics) before collecting samples to prevent heparin contamination 2