What is the recommended management for Heparin-Induced Thrombocytopenia (HIT)?

Management of Heparin-Induced Thrombocytopenia (HIT)

When clinical probability of HIT is intermediate or high, heparin therapy should be immediately discontinued and replaced with non-heparin anticoagulant therapy at therapeutic doses, without waiting for laboratory confirmation. 1, 2

Initial Assessment and Management

• Use the 4T score to determine pre-test probability of HIT, with scores categorized as low (≤3), intermediate (4-5), or high (≥6) 2
• For low pre-test probability (4T ≤3), HIT can be excluded and heparin can be continued with close monitoring of platelet count 1
• For intermediate (4T = 4-5) or high (4T ≥6) pre-test probability, perform anti-PF4 antibody testing while simultaneously initiating alternative anticoagulation 1, 2
• Immediately discontinue all forms of heparin (including heparin flushes and heparin-coated catheters) when HIT is suspected with intermediate or high probability 1

Alternative Anticoagulation Options

• Start therapeutic-dose non-heparin anticoagulation immediately, even if thrombosis is not present, due to the high thrombotic risk in HIT 1, 2
• Recommended alternative anticoagulants include argatroban, bivalirudin, danaparoid, fondaparinux, and direct oral anticoagulants (DOACs) 1, 3

Argatroban

• First-line option for HIT with standard dosing of 2 mcg/kg/min as continuous IV infusion 4
• Preferred in patients with renal dysfunction (no dose adjustment needed) but requires dose reduction in hepatic impairment 1, 2
• Monitor using aPTT with target of 1.5-3 times baseline value 4
• Reduce initial dose to 0.5-1 mcg/kg/min in critically ill patients, cardiac surgery patients, and those with moderate hepatic impairment 1

Bivalirudin

• Short half-life (20-30 minutes) makes it useful for procedures requiring short-acting anticoagulation 2
• Not recommended in severe renal impairment (creatinine clearance <30 mL/min) 2

Danaparoid

• Not recommended as first-line treatment for HIT in severe renal failure 1
• Requires therapeutic (not prophylactic) dosing with monitoring of anti-Xa activity using a specific calibration curve 1
• Should be replaced if platelet count doesn't recover or if thrombosis appears or extends 1

Special Situations

• For severe HIT (massive PE, extensive/arterial thrombosis, venous gangrene, consumption coagulopathy), prefer argatroban or bivalirudin with strict biological monitoring 1
• In severe renal impairment (CrCl <30 mL/min), argatroban is the preferred agent 1, 2
• In severe hepatic impairment (Child-Pugh C), 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
• Direct oral anticoagulants (DOACs) are increasingly used in acute HIT (off-label) as they are easier to administer and more cost-effective than parenteral options 3
• When transitioning to VKAs, overlap with parenteral anticoagulant for at least 5 days 2

Perioperative Management

• For patients with acute HIT (<1 month), postpone elective surgery beyond the first month if possible 1
• If surgery cannot be delayed, use short-acting agents like argatroban or bivalirudin 1, 2
• For cardiac surgery in patients with a history of HIT, systematically perform ELISA for anti-PF4 antibodies before surgery 1

Long-term Considerations

• Provide patients with documentation of their HIT diagnosis and laboratory results 2
• Avoid re-exposure to heparin, especially within 3 months of HIT diagnosis 2, 5
• Consider extended anticoagulation (3-6 months) for patients with thrombotic events 2

Common Pitfalls and Caveats

• Avoid platelet transfusions as they may worsen thrombosis in HIT patients 2
• Do not initiate vitamin K antagonists (VKAs) until platelet count has recovered, as they can potentially cause venous limb gangrene in acute HIT 1, 6
• Overdiagnosis and overtreatment are common due to the frequency of thrombocytopenia in hospitalized patients and limited specificity of immunoassays 7
• Delayed HIT can develop days to weeks after heparin discontinuation, requiring vigilance even after stopping heparin 6