Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia
Updated: 07/24/2023
© Jun Wang, MD, PhD

General features
  • Complication of heparin therapy
  • More commonly associated with unfractionated heparin (UFH) than low molecular weight heparin (LMWH)
  • Type I:  Presents within the first 2 days after exposure to heparin, and the platelet count normalizes with continued heparin therapy, nonimmune disorder resulted from direct effect of heparin on platelet activation
  • Type II:  Immune-mediated disorder, typically occurs 4-10 days after exposure to heparin, life- and limb-threatening thrombotic complications, THE HIT when discussed
  •  Diagnosis based on
History of heparin usage
Clinical presentations of thromboembolism
Thrombocytopenia
 Laboratory studies of HIT antibodies
Clinical presentations
  • Thromboembolism
  • Most commonly venous thrombosis
  • 4Ts
Thrombocytopenia
Timing of platelet count drop, typically 5-14 days, or less in one day if previously exposed to heparin
Thrombosis and associated consequences
Rule out other causes of Thrombocytopenia
Key risk factors
  • Prolonged use of heparin, commonly for postoperative thrombophylaxis
Key pathogenesis
  • Autoantibodies bind to complexes of heparin and platelet factor 4 (PF4)
  • Binding activates platelets and promotes a prothombotic status
Key Laboratory findings
  • Thrombocytopenia
  • HIT antibodies
Management
  • Discontinue all heparin products
  • Anticoagulants


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