What is the management of heparin-induced thrombocytopenia (HIT)?

Management of Heparin-Induced Thrombocytopenia (HIT)

For patients with suspected heparin-induced thrombocytopenia, immediately discontinue all forms of heparin and initiate therapeutic-dose non-heparin anticoagulation, even before laboratory confirmation. 1, 2

Initial Assessment and Management

• Calculate the 4T score to determine pre-test probability of HIT:

  • Low probability (≤3 points): HIT can be excluded and heparin can be continued with monitoring 1, 2
  • Intermediate (4-5 points) or high (≥6 points): Stop all heparin and start alternative anticoagulation 1, 2

• Immediately remove all potential sources of heparin exposure, including heparin flushes and heparin-coated catheters 1, 2

• For intermediate or high pre-test probability, perform anti-PF4 antibody testing while simultaneously initiating alternative anticoagulation 1

• Start therapeutic-dose (not prophylactic) non-heparin anticoagulation immediately due to high thrombotic risk in HIT, without waiting for laboratory confirmation 1, 2

Alternative Anticoagulant Options

• Argatroban (direct thrombin inhibitor):

  • Initial dose: 2 mcg/kg/min as continuous IV infusion 3
  • Monitor aPTT to maintain 1.5-3 times baseline value 3
  • Preferred in renal impairment (creatinine clearance <30 mL/min) 1, 2
  • Dose adjustment needed for hepatic impairment 3

• Bivalirudin (direct thrombin inhibitor):

  • Shorter half-life (20-30 minutes), useful for procedures requiring short-acting anticoagulation 1
  • Not recommended in severe renal impairment 2

• Danaparoid (heparinoid):

  • Requires monitoring of anti-Xa activity with specific calibration 1
  • Not recommended in severe renal failure 2

• Fondaparinux (factor Xa inhibitor):

  • Option for stable patients without severe renal or hepatic impairment 2
  • Does not require specific monitoring 2

Special Situations

• For severe HIT (massive PE, extensive/arterial thrombosis, venous gangrene):

  • Prefer argatroban or bivalirudin with strict biological monitoring 1, 2

• For cardiac surgery in patients with HIT:

  • Two strategies are possible: 4
    • Combination of intravenous antiplatelet agent (tirofiban, cangrelor, or iloprost) with unfractionated heparin 4
    • Use of thrombin inhibitor anticoagulant (bivalirudin or argatroban) 4

• For patients with renal dysfunction:

  • Argatroban is preferred over bivalirudin 1, 2

• For patients with hepatic impairment:

  • Bivalirudin, danaparoid, or fondaparinux may be used 1
  • Adjust argatroban dosing in moderate or severe hepatic impairment 3

Transitioning to Oral Anticoagulation

• Wait for platelet count recovery (>150,000/μL or return to baseline) before transitioning to vitamin K antagonists (VKAs) 1, 2

• Avoid VKAs in the acute phase of HIT, as they can potentially cause venous limb gangrene 2

• Overlap parenteral anticoagulant with oral agent for at least 5 days 1

Common Pitfalls and Caveats

• Do not give platelet transfusions, as they may worsen thrombosis in HIT patients 2

• Do not wait for laboratory confirmation before stopping heparin if clinical suspicion is high 1, 2

• Do not use prophylactic doses of alternative anticoagulants - therapeutic doses are required 1, 2

• Avoid re-exposure to heparin, especially within 3 months of HIT diagnosis 1, 2

• Biological confirmation of HIT diagnosis is necessary but should never delay stopping heparin and starting alternative anticoagulation 4

Long-term Management

• Document HIT diagnosis in medical records and provide patients with documentation of their diagnosis 1, 2

• Schedule follow-up with hematology within 3 months of diagnosis 1

• For future anticoagulation needs, use oral anticoagulants (VKA or DOAC) or fondaparinux 1, 2

• Consider extended anticoagulation (3-6 months) depending on the clinical situation 2