Please confirm topic selection

Are you sure you want to trigger topic in your Anconeus AI algorithm?

Please confirm action

You are done for today with this topic.

Would you like to start learning session with this topic items scheduled for future?

Updated: Dec 18 2021

Heparin-Induced Thrombocytopenia (HIT)

Images
https://upload.medbullets.com/topic/121677/images/hit.jpg
https://upload.medbullets.com/topic/121677/images/deep_vein_thrombosis_of_the_right_leg.jpg
  • Snapshot
    • A 60-year-old woman presents after a 12-hour train ride with right-sided crampy leg pain. She is currently on hormone-replacement therapy for menopausal symptoms. On exam, the circumference on the right calf is larger than the left. An ultrasound shows a lower extremity DVT. She is started on heparin. Two days later, her platelets come back at 24,000/mm3. They were previously 30,000/mm3. Her labs are monitored routinely, and her platelets returned to baseline after a few days.
  • Introduction
    • Decreased platelets due to exposure to heparin
  • Epidemiology
    • Female > male (1.7x)
    • Risk factors
      • more common with unfractionated heparin
      • longer duration of heparin use
  • etiology
    • Type I HIT
      • presents within first 2 days after exposure to heparin
      • platelet count normalizes spontaneously
      • non-immune mediated
      • direct effect of heparin on platelet activation
    • Type II HIT
      • hypercoagulable state associated with significant risk of thrombosis
      • can be fatal
      • presents 5-10 days after exposure to heparin
      • pathogenesis
        • heparin binds to platelet factor 4 (PF4)
        • IgG antibodies recognize the heparin-PF4 complex
        • complex-bound antibodies bind to platelets and cause platelet activation
          • thrombosis
          • thrombocytopenia
          • type II hypersensitivity reaction
  • Presentation
    • Type I - asymptomatic
    • Type II - symptoms
      • 5-10 days after heparin
      • > 30% drop in platelets
      • venous > arterial thrombosis
        • DVT/PE
        • skin necrosis
        • stroke
      • some may present with acute systemic reactions after IV heparin bolus
        • fever
        • chills
        • dyspnea
      • overt bleeding is rare
        • can see bleeding at injection sites
  • studies
    • Complete blood count
      • drop in platelet count by > 30%
        • no matter the absolute platelet count
    • ↑ bleeding time
    • Normal PT/PTT
    • Presence of anti-PF4-heparin
      • serotonin release assay
      • enzyme immunoassay
  • Differential Diagnosis
    • DIC
    • ITP
    • TTP
    • HUS
  • Treatment
    • Prevention
      • Avoid heparin-containing products
    • First step
      • stop all heparin-containing products
    • Subsequent steps
      • direct thrombin inhibitors
        • argatroban, lepirudin, and bivalirudin
      • transition to warfarin when platelets are back at baseline
    • PLT infusion is contraindicated
      • may worsen thrombosis
  • Complications
    • Thrombosis
  • Prognosis
    • Mortality 5-10% in patients with HIT type II
      • from thrombosis
Card
1 of 0
Question
1 of 5
Private Note