Heparin-induced thrombocytopenia: Difference between revisions

No edit summary
Line 1: Line 1:
==Background==
==Background==
*Despite low plt count pt is actually hypercoagulable; bleeding is unusual
*Pathologic activation / consumption of platelets due to antibodies against heparin-plt complex
*Pathophysiology
*Despite the low platelet count, the patient is actually hyper coagulable and bleeding is unusual.  The activated platelets cause blood clot formation and the platelet count falls because the platelets are bound in clots.
**Pathologic activation / consumption of platelets due to Ab against heparin-plt complex
*Can be caused by unfrationated or LMWH (10x common in the former)
**Activated platelets then cause blood clot formation
*Occurs in 0.5-5% of patients treated with heparin<ref name="Lovecchio"> Lovecchio F. Heparin-induced thrombocytopenia. Clin Toxicol (Phila). 2014 Jul;52(6):579-83</ref>
***Platelet count falls b/c plts are bound in clots
*Thrombosis occurs in 35-75% of patients ; 20-30% die within 1 month<ref name="Lovecchio"></ref>
**Can be caused by unfrationated or LMWH (10x common in the former)
***Occurs in 0.5-5% of pts tx'd w/ heparin
*Thrombosis occurs in 35-75% of pts; 20-30% die w/in 1 month


==Clinical Features==
==Clinical Features==
Line 58: Line 55:


==Source==
==Source==
Tintinalli
<references/>


[[Category:Heme/Onc]]
[[Category:Heme/Onc]]

Revision as of 12:34, 4 July 2014

Background

  • Pathologic activation / consumption of platelets due to antibodies against heparin-plt complex
  • Despite the low platelet count, the patient is actually hyper coagulable and bleeding is unusual. The activated platelets cause blood clot formation and the platelet count falls because the platelets are bound in clots.
  • Can be caused by unfrationated or LMWH (10x common in the former)
  • Occurs in 0.5-5% of patients treated with heparin[1]
  • Thrombosis occurs in 35-75% of patients ; 20-30% die within 1 month[1]

Clinical Features

  • Typical
    • Symptoms begin 5-10d after initiation of heparin
      • >50% decrease in plt count (median nadir is ~60K; rarely <20K)
      • DVT or PE
      • Cerebral vein or adrenal vein thrombosis
      • Limb arterial occlusion
      • CVA
      • MI
      • Skin necrosis
  • Rapid onset
    • Symptoms begin within hours of initiation of heparin
      • Due to preexisting circulating antibody from sensitization several weeks earlier
      • Sudden drop in plt count
      • Thrombosis
      • Flushing
      • Tachycardia
      • Hypotension
      • Dyspnea
  • Delayed onset
    • Symptoms begin several days after heparin stopped
    • Severe thromboses

DDX

Diagnosis

  • Serotonin release assay (SRA) = gold standard
    • Positivity determined by optical density (OD) reported w/ assay (same concept as a titer)
      • OD <1 = <5% chance of HIT
      • OD 1.4 = 50% chance of HIT
      • OD >2 = 90% chance of HIT

Treatment

  1. Discontinue all heparin products
  2. Do not give platelts (may precipitate thrombosis)
  3. Start anticoagulation
    1. Consider direct thrombin inhibitor [lepirudin (unless renal failure), argatroban (unless hepatobiliary disease), bivalirudin] or direct Xa inhibitor (fondaparinux, danaparoid)
    2. Avoid warfarin until platelets >100K-150K

Dispostion

  • Admit

See Also

Source

  1. 1.0 1.1 Lovecchio F. Heparin-induced thrombocytopenia. Clin Toxicol (Phila). 2014 Jul;52(6):579-83