What is the recommended anticoagulation treatment for a patient diagnosed with heparin-induced thrombocytopenia (HIT)?

Anticoagulation for Heparin-Induced Thrombocytopenia (HIT)

Immediately discontinue all heparin products and start a non-heparin anticoagulant—specifically argatroban, lepirudin, or danaparoid—without waiting for laboratory confirmation when HIT is suspected. 1, 2

Immediate Actions

• Stop all heparin exposure immediately, including IV heparin, subcutaneous heparin, heparin flushes, and heparin-coated catheters 3, 4
• Do not use low-molecular-weight heparin (LMWH) as an alternative—this is a dangerous misconception since LMWH cross-reacts with HIT antibodies in 80-90% of cases 3
• Start alternative anticoagulation immediately before laboratory confirmation, as the thrombotic risk is extremely high (odds ratio 37 for thrombosis) 4, 5
• Send HIT antibody testing (anti-PF4 antibodies) to confirm diagnosis, but do not delay treatment 3, 4

First-Line Anticoagulant Selection Algorithm

For Patients with Normal Renal Function:

Choose argatroban, lepirudin, or danaparoid based on availability, cost, and monitoring capabilities 1, 2

For Patients with Renal Insufficiency:

Use argatroban preferentially because it is hepatically metabolized and does not accumulate in renal failure 1, 2

For Patients with Hepatic Impairment:

Avoid argatroban; instead use bivalirudin, danaparoid, or fondaparinux 2

For Pregnant Patients:

Danaparoid is preferred, with lepirudin or fondaparinux as alternatives if danaparoid is unavailable 2

Specific Clinical Scenarios

Percutaneous Coronary Intervention (PCI):

Bivalirudin is the preferred agent (Grade 2B recommendation), with argatroban as an alternative (Grade 2C) 1, 2, 4

Urgent Cardiac Surgery:

Use bivalirudin if surgery cannot be delayed 1, 4

Non-Urgent Cardiac Surgery:

Delay surgery until HIT resolves and antibodies are negative (typically >1 month) 1

Argatroban Dosing and Monitoring

• Initial dose: 2 μg/kg/min continuous IV infusion 6
• Reduce to 0.5-1 μg/kg/min in hepatic impairment, cardiac surgery, or critical illness 3
• Target aPTT: 1.5-3 times baseline (but keep aPTT <100 seconds) 3
• Check aPTT 2 hours after starting infusion and 2 hours after any dose adjustment 3

Critical Management of Warfarin Transition

Do not start warfarin during acute thrombocytopenia—this can cause venous limb gangrene and skin necrosis 1, 2, 3

When to Start Warfarin:

• Wait until platelet count recovers to ≥150 × 10⁹/L 1, 2
• Use low initial doses only (maximum 5 mg warfarin or 6 mg phenprocoumon) 1
• Overlap with non-heparin anticoagulant for minimum 5 days and until INR is therapeutic 1, 2
• Recheck INR after the non-heparin anticoagulant effect has resolved 1

If Warfarin Already Started:

Administer vitamin K immediately when HIT is diagnosed 1, 3

Duration of Treatment

• Continue non-heparin anticoagulant for mean 5-7 days until platelet count recovers to >150,000/μL 3
• For isolated HIT (without thrombosis), use the same agents and approach as HIT with thrombosis 1

Common Pitfalls to Avoid

• Never continue heparin or LMWH once HIT is suspected with intermediate or high probability 2, 3
• Do not give platelet transfusions unless active bleeding or high-risk invasive procedures are planned 1, 2, 3
• Do not delay treatment waiting for laboratory confirmation when clinical probability is intermediate or high 2, 4
• Do not start warfarin monotherapy during acute HIT—this promotes thrombosis progression to gangrene 3, 7

Emerging Alternatives

Fondaparinux is an emerging alternative with less robust evidence than traditional agents, but can be considered when other options are unavailable or contraindicated 2, 7, 8

The 2020 Anaesthesia guidelines suggest fondaparinux or oral anticoagulants (VKA or DOACs) for patients with recent HIT requiring elective procedures, though this represents a more recent but lower-strength recommendation compared to the established direct thrombin inhibitors 1