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Heparin induced thrombocytopenia

HIT

Overview

Heparin-induced thrombocytopenia (HIT) is an adverse reaction to the drug heparin resulting in an abnormally low amount of platelets (thrombocytopenia). HIT is usually an immune response which typically occurs 4-10 days after exposure to heparin; it can lead to serious complications and be life-threatening. This condition occurs in up to 5% of those who are exposed to heparin. Characteristic signs of HIT are a drop in platelet count of  greater than 50% and/or the formation of new blood clots during heparin therapy.  The first step of treatment is to discontinue and avoid all heparin products immediately. Often, affected individuals require another medicine to prevent blood clotting (anticoagulants).

Symptoms - Heparin induced thrombocytopenia

Thrombocytopenia signs and symptoms may include:

  • Easy or excessive bruising (purpura)
  • Superficial bleeding into the skin that appears as a rash of pinpoint-sized reddish-purple spots (petechiae), usually on the lower legs
  • Prolonged bleeding from cuts
  • Bleeding from your gums or nose
  • Blood in urine or stools
  • Unusually heavy menstrual flows
  • Fatigue
  • Enlarged spleen
  • Jaundice

Causes - Heparin induced thrombocytopenia

Characteristic signs of HIT are a drop in platelet count of >50% and/or new thromboembolic complications during heparin therapy. Two types of HIT are recognized. Nonimmune heparin-associated thrombocytopenia is due to a direct interaction between heparin an platelets. The other type of HIT, immune-mediated HIT, is caused by heparin dependent IgG (HIT-IgG) that recognizes a complex of heparin and platelet factor 4 (PF4), leading to platelet activation via the platelet Fc gammaRIIa receptor.

Prevention - Heparin induced thrombocytopenia

At present, the most effective measure to reduce the risk of HIT is to use low-molecular-weight heparin (LMWH) instead of UFH, if possible, sine LMWH is less frequently associated with HIT.

Diagnosis - Heparin induced thrombocytopenia

Regular platelet count monitoring is best suited for early diagnosis of HIT, especially if UFH is used. Functional and antigen assays are available to confirm HIT.

Prognosis - Heparin induced thrombocytopenia

If you have thrombocytopenia, try to:

  • Avoid activities that could cause injury. Ask your doctor which activities are safe for you. Contact sports, such as boxing, martial arts and football, carry a high risk of injury.
  • Drink alcohol in moderation, if at all. Alcohol slows the production of platelets in your body. Ask your doctor whether it's OK for you to drink alcohol.
  • Use caution with over-the-counter medications. Over-the-counter pain medications, such as aspirin and ibuprofen (Advil, Motrin IB, others) can impair platelet function.

Treatment - Heparin induced thrombocytopenia

Heparin withdrawal and treatment with an agent that directly inhibits thrombin or decreases thrombin generation should be initiated prior to laboratory confirmation because of the rapidity with which thrombotic complications occur following platelet decline. Alternative anticoagulants are available for patients affected with HIT.

Approved therapies:
Lepirudin (Refluden) - FDA-approved indication: For anticoagulation in patients with heparin-induced thrombocytopenia and associated thromboembolic disease in order to prevent further thromboembolic complications.

Resources - Heparin induced thrombocytopenia

Refer to research Publications.

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