What is the immediate management for a patient presenting with Heparin-Induced Thrombocytopenia (HIT) symptoms?

Immediate Management of Heparin-Induced Thrombocytopenia (HIT)

When HIT is suspected, 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, with scores categorized as low (≤3), intermediate (4-5), or high (≥6) 1, 2
• For intermediate or high pre-test probability, immediately perform anti-PF4 antibody testing while simultaneously initiating alternative anticoagulation 1
• Stop all forms of heparin, including heparin flushes and heparin-coated catheters, and remove all potential sources of heparin exposure 2
• Do not give platelet transfusions, as they may worsen thrombosis in HIT patients 2

Alternative Anticoagulation Options

• Start therapeutic-dose (not prophylactic) non-heparin anticoagulation immediately due to high thrombotic risk in HIT 1, 2
• Recommended non-heparin anticoagulants for acute HIT include:
  • Argatroban: Initial dose of 2 mcg/kg/min as continuous IV infusion, with monitoring of aPTT to maintain 1.5-3 times baseline value; preferred in renal impairment 1, 2
  • Bivalirudin: A direct thrombin inhibitor with shorter half-life (20-30 minutes), useful for procedures requiring short-acting anticoagulation; not recommended in severe renal impairment 1
  • Danaparoid: Requires monitoring of anti-Xa activity with specific calibration; not recommended in severe renal failure 1, 2
  • Fondaparinux: An option for stable patients without severe renal or hepatic impairment 1, 2

Special Situations

• For severe HIT (massive PE, extensive/arterial thrombosis, venous gangrene, consumption coagulopathy), prefer argatroban or bivalirudin with strict biological monitoring 1, 2
• In severe renal impairment (CrCl <30 mL/min), argatroban is the preferred agent 1, 2
• In severe hepatic impairment, bivalirudin, danaparoid, or fondaparinux may be used 1

Transitioning to Oral Anticoagulation

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

Common Pitfalls and Caveats

• Do not delay discontinuation of heparin and initiation of alternative anticoagulation while waiting for laboratory results 2
• Do not use prophylactic doses of alternative anticoagulants - therapeutic doses are required 2
• It is not recommended to prescribe an oral antiplatelet agent to treat acute HIT 3
• Do not insert an inferior vena cava filter in the acute phase of HIT 3
• Do not use IV immunoglobulins as first-line treatment for acute HIT 3

Perioperative Management

• For patients with acute HIT (<1 month), postpone any surgery beyond the first month if this does not generate a major vital or functional risk 3
• If surgery cannot be delayed, use short-acting agents like argatroban (stop 4 hours before procedure) or bivalirudin (stop 2 hours before procedure) 3
• In postoperative care, if prolonged anticoagulation is needed and bleeding risk is controlled, treat preferentially with fondaparinux or an oral anticoagulant (VKA or DOAC) 3

Long-term Management

• Document HIT diagnosis in medical records 2
• Consider extended anticoagulation (3-6 months) depending on the clinical situation 2
• For future anticoagulation needs, use oral anticoagulants (VKA or DOAC) or fondaparinux 2
• Avoid re-exposure to heparin, especially within 3 months of HIT diagnosis 2