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[[Heparin-induced thrombocytopenia]] is diagnosed when the [[platelet]] count falls by > 50% typically after 5-10 days of [[heparin]] therapy.
[[Heparin-induced thrombocytopenia]] is diagnosed when the [[platelet]] count falls by > 50% typically after 5-10 days of [[heparin]] therapy.
==Risk factors==
==Risk factors==
Genetic risk factors for thrombosis such as [[factor V Leiden]], [[prothrombin]] gene mutation, [[methylenetetrahydrofolate reductase]] ([[MTHFR]]) polymorphism and platelet-receptor polymorphisms do not increase the risk of developing HIT associated thrombosis.


4 factors that affect the risk of developing HIT are noted as follows.<ref>Warkentin TE, Sheppard JA, Sigouin CS, Kohlmann T, Eichler P, Greinacher A. Gender imbalance and risk factor interactions in heparin-induced thrombocytopenia. ''Blood'' 2006;108:2937-41. PMID 16857993.</ref>
* Genetic risk factors for thrombosis such as [[factor V Leiden]], [[prothrombin]] gene mutation, [[methylenetetrahydrofolate reductase]] ([[MTHFR]]) polymorphism and platelet-receptor polymorphisms do not increase the risk of developing HIT associated thrombosis.
1) Duration of heparin treatment; long duration, up to 2 weeks is associated with the greatest risk.  
* Factors that affect the risk of developing HIT are noted as follows.<ref>Warkentin TE, Sheppard JA, Sigouin CS, Kohlmann T, Eichler P, Greinacher A. Gender imbalance and risk factor interactions in heparin-induced thrombocytopenia. ''Blood'' 2006;108:2937-41. PMID 16857993.</ref>
2) The type of heparin involved; UFH has a greater risk than LMWH.   
** Duration of heparin treatment; long duration, up to 2 weeks is associated with the greatest risk.  
3) The type of patient; surgical patients are at higher risk than medical; cardiac surgical patients have the highest risk of all.
** The type of heparin involved; unfractionated heparin[[UFH]] has a greater risk than [[low molecular weight heparin]] LMWH.   
4) Females have a higher risk.
** The type of patient; surgical patients are at higher risk than medical; cardiac surgical patients have the highest risk of all.
** Females have a higher risk.


CPB bypass:  The management of cardiopulmonary bypass (CPB) patients with active HIT is controversial.  Direct Thrombin Inhibitors such as agatroban and hirudin are used (and increase the aPTT in a dose dependent manner).  However, in the large doses required for CPB hirudin's effects cannot be monitored well.  Following CPB surgery the platelet count drops to about 40-60% of normal within the first 2-3 days postop due to hemodilution and platelet consumption.  But there is also a risk of HIT.  20-50% of patients develop heparin antibodies during the first 5-10 days following CPB and some develop HIT (1-3% if UFH is continued through the postop period).
==Reference==
==Reference==
{{Reflist|2}}
{{Reflist|2}}

Revision as of 17:15, 10 December 2011

Heparin-induced thrombocytopenia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Cafer Zorkun, M.D., Ph.D. [2], Aric C. Hall, M.D., [3]

Overview

Heparin-induced thrombocytopenia is diagnosed when the platelet count falls by > 50% typically after 5-10 days of heparin therapy.

Risk factors

  • Genetic risk factors for thrombosis such as factor V Leiden, prothrombin gene mutation, methylenetetrahydrofolate reductase (MTHFR) polymorphism and platelet-receptor polymorphisms do not increase the risk of developing HIT associated thrombosis.
  • Factors that affect the risk of developing HIT are noted as follows.[1]
    • Duration of heparin treatment; long duration, up to 2 weeks is associated with the greatest risk.
    • The type of heparin involved; unfractionated heparinUFH has a greater risk than low molecular weight heparin LMWH.
    • The type of patient; surgical patients are at higher risk than medical; cardiac surgical patients have the highest risk of all.
    • Females have a higher risk.

Reference

  1. Warkentin TE, Sheppard JA, Sigouin CS, Kohlmann T, Eichler P, Greinacher A. Gender imbalance and risk factor interactions in heparin-induced thrombocytopenia. Blood 2006;108:2937-41. PMID 16857993.

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