Heparin-induced thrombocytopenia history and symptoms: Difference between revisions
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==History== | ==History== | ||
===Heparin therapy=== | |||
* 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 | * 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: | * Delayed onset HIT: | ||
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** The phenomena is sometimes explained by the fact that unusually high antibody levels react with platelet-associated Platelet Factor 4 (PF4) bound to non-heparin [[glycosaminoglycans]] like [[chondroitin sulfate]] and not to heparin. | ** The phenomena is sometimes explained by the fact that unusually high antibody levels react with platelet-associated Platelet Factor 4 (PF4) bound to non-heparin [[glycosaminoglycans]] like [[chondroitin sulfate]] and not to heparin. | ||
* The incidence of delayed onset [[HIT]] are less compared to other forms of HIT. | * The incidence of delayed onset [[HIT]] are less compared to other forms of HIT. | ||
===Cardiac surgery=== | |||
* In cardiac surgery patients decrease in the platelet count > 50 % can occur with 3 days after surgery. This may be attributed to prolonged contact of platelets with the artificial surface, administration of large amount of unfractionated heparin (UFH). However, a diagnosis of HIT is done if a fall in the platelet count ≥50 % is seen after 5-10 days of heparin therapy. | |||
{{WH}} | {{WH}} | ||
{{WS}} | {{WS}} | ||
Revision as of 16:07, 4 December 2011
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Heparin-induced thrombocytopenia |
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Differentiating Heparin-induced thrombocytopenia from other Diseases |
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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
Heparin therapy
- 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:
- Occurs after heparin has been withdrawn (median time of 14 days after heparin withdrawl)
- High titer platelet-activating antibodies that have both increased heparin-dependent and heparin independent platelet activation
- The phenomena is sometimes explained by the fact that unusually high antibody levels react with platelet-associated Platelet Factor 4 (PF4) bound to non-heparin glycosaminoglycans like chondroitin sulfate and not to heparin.
- The incidence of delayed onset HIT are less compared to other forms of HIT.
Cardiac surgery
- In cardiac surgery patients decrease in the platelet count > 50 % can occur with 3 days after surgery. This may be attributed to prolonged contact of platelets with the artificial surface, administration of large amount of unfractionated heparin (UFH). However, a diagnosis of HIT is done if a fall in the platelet count ≥50 % is seen after 5-10 days of heparin therapy.