What is the recommended approach for Deep Vein Thrombosis (DVT) prophylaxis (ppx) in a patient with Heparin-Induced Thrombocytopenia (HITT)?

DVT Prophylaxis in Patients with Heparin-Induced Thrombocytopenia (HIT)

In patients with HIT requiring DVT prophylaxis, discontinuation of all heparin products and initiation of a non-heparin anticoagulant is strongly recommended. 1

Initial Management

When HIT is diagnosed or strongly suspected:

1. Immediately discontinue all forms of heparin including:

   • Unfractionated heparin (UFH)
   • Low molecular weight heparin (LMWH)
   • Heparin flushes
   • Heparin-coated catheters

2. Initiate a non-heparin anticoagulant at therapeutic intensity unless contraindicated due to high bleeding risk 1

Choice of Non-Heparin Anticoagulant

Several options are available, with selection based on specific patient factors:

Recommended Options:

• Argatroban: Preferred in patients with renal dysfunction or critical illness due to short half-life and hepatic clearance 1, 2
• Bivalirudin: Alternative for critically ill patients or those requiring procedures 1
• Fondaparinux: Good option for stable patients with normal renal function 1
• Direct Oral Anticoagulants (DOACs): Appropriate for clinically stable patients with normal organ function 1
• Danaparoid: Option where available (not available in some countries) 1

Key Selection Factors:

• Renal function: Avoid fondaparinux and use caution with DOACs in renal impairment
• Hepatic function: Avoid argatroban or reduce dose in moderate/severe hepatic dysfunction
• Clinical stability: Prefer parenteral agents with shorter half-lives in critically ill patients
• Need for procedures: Consider agents with shorter half-lives (argatroban, bivalirudin)
• Bleeding risk: Consider reduced intensity in high bleeding risk patients

Dosing Considerations

Argatroban:

• Standard dose: 2 mcg/kg/min continuous infusion
• Hepatic impairment: Reduce initial dose to 0.5-1.0 mcg/kg/min
• Target: aPTT 1.5-3 times baseline (not exceeding 100 seconds)
• Monitor: Check aPTT 2 hours after initiation and after dose changes 2

DOACs (if using rivaroxaban):

• Acute HIT with thrombosis: 15 mg twice daily for 3 weeks, then 20 mg once daily
• Acute HIT without thrombosis: 15 mg twice daily until platelet count recovery, then 20 mg once daily if ongoing anticoagulation indicated 1

Duration of Therapy

• HIT without thrombosis: Continue therapeutic anticoagulation until platelet count recovers (typically ≥150 × 10^9/L) 1
• HIT with thrombosis: Continue therapeutic anticoagulation for at least 3 months 1

Special Considerations

Transitioning to Vitamin K Antagonists (VKAs):

• Do not initiate VKA until platelet count has substantially recovered (≥150 × 10^9/L)
• Continue non-heparin anticoagulant during VKA initiation for at least 5 days and until INR reaches therapeutic range 1

Invasive Procedures:

• Avoid IVC filters in patients with HIT as they do not prevent all thrombotic complications and may increase risk 1
• For patients requiring cardiac surgery, delay if possible until HIT antibodies are no longer detectable 1

Monitoring

• Monitor platelet count daily until recovery
• Perform bilateral lower extremity ultrasound to screen for asymptomatic DVT in patients with isolated HIT 1
• For patients with upper extremity central venous catheters, perform upper extremity ultrasound to screen for DVT 1

Common Pitfalls to Avoid

1. Inadequate anticoagulation: Simply stopping heparin without starting an alternative anticoagulant is insufficient and dangerous
2. Premature VKA initiation: Starting warfarin before platelet recovery can precipitate venous limb gangrene
3. Inadequate monitoring: Failure to monitor anticoagulant effect can lead to under- or over-anticoagulation
4. Restarting heparin: Avoid reintroduction of heparin products in acute or subacute HIT

By following these evidence-based recommendations, clinicians can effectively manage DVT prophylaxis in patients with HIT while minimizing thrombotic and bleeding complications.