Heparin-induced thrombocytopenia history and symptoms
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Overview
Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy. Unlike other immune mediated thrombocytopenia (idiopathic thrombocytopenic purpura), the levels of platelet stays > 20,000 microl, thus frank clinical bleeding is less common in HIT when compared to other conditions, where the platelet may fall below 10,000/ microl.
History
- Occurs commonly after 5-10 days of initiation of heparin therapy. Onset of HIT after 2 weeks of heparin therapy is uncommon. Earlier onset of HIT is usually seen in patients who have been previously treated with heparin (1-3 months back) and have circulating HIT antibodies in them. In these patients the median time of platelet fall is less than 12 hours after the start of heparin administration
- Delayed onset HIT is uncommon.