DR Medhat MRCP

Heparin-induced thrombocytopaenia (HIT)
- Immune mediated - antibodies form which cause the activation of platelets
- Usually does not develop until after 5-10 days of heparin treatment
- Despite being associated with low platelets HIT is actually a prothrombotic condition
• Types:
Type I :
o Usually occurs 48 to 72 hours post commensing heparing and PLT rarely
< 100.
o PLT returns to normal over 4 days and there is no↑ risk of
thromboembolism.
Type II :
o Much rarer and usually occurs 5 to 10 days after starting heparin
o PLT usually 50% reduction in platelets
سؤال DVT. 2) Thrombosis : arterial or venous but most commonly
3) Skin allergy.
• Diagnosis: is clinical:
Thrombocytopenia: PLT < 100 or < 50% from the patient's baseline
The exclusion of other causes of thrombocytopenia
The resolution of thrombocytopenia after cessation of heparin.
Supportive lab tests: HIT antibodies can be demonstrated in vitro by functional
tests (are more specific) and immunoassays.
• Treatment :
Alternative direct thrombin inhibitors (Heparinoids) such as
o Lepirudin (Refludan).
o Danaparoid (Orgaran).→Safe in pregnancy (not crossing placental barrier)
o Bivalirudin (Angiomax).
- Warfarin should NOT be initiated for longer-term protection from further events
until substantial platelet count recovery has occurred.
- HIT patients who are switched to warfarin alone after the discontinuation of
heparin may paradoxically have worsening thrombosis and develop venous limb
gangrene and skin necrosis.
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