Heparin Induced Thrombocytopenia

Heparin may be used for both prevention and the treatment of thrombosis. In HIT, the platelet count in the blood falls below the normal range, a condition called thrombocytopenia. However, it is generally not low enough to lead to an increased risk of bleeding.

Usual scenario:
Relative fall in platelet count >/50 % with absolute count of not less than 20 associated with

• arterial or venous thrombosis
• skin necrosis
• anaphylatoid reaction

There is no alternative explanation for thrombocytopenia.

A clinical probability score ( 4 Ts ):


Management:


Bilateral lower extremity compression USS should be performed in all patients with HIT, whether or not there is clinical evidence of lower limb DVT as it will influence the duration of anticoagulation.

For patients with HIT associated thrombosis, anticoagulate for a defined course typically 3 - 6 months as with other provoked thromboses.

For patients with HIT without thrombosis, the optimal duration of anticoagulation is unknown but anticoagulation for at least 0ne months is usual.

Non-heparin anticoagulants such as danaparoid, lepirudin and Fondaparinux is recommended.

HIT patients are at risk of venous limb gangrene during initiation of warfarin and warfarin should not be introduced until the platelet count is more than 150.