Heparin-induced thrombocytopenia history and symptoms

Heparin-induced thrombocytopenia
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2] Shyam Patel [3]

Overview

The history of HIT always involves exposure to heparin. Typical features of a patient's history depend on the type and location of thrombosis and whether the platelet count is sufficiently low to result in bleeding. Venous and arterial thromboses can result in variable symptoms. Symptoms of deep vein thrombosis include leg pain, swelling, and/or erythema. Symptoms of pulmonary embolism include dyspnea, pleuritic chest, and/or hypotension. Symptoms of arterial occlusion of a limb include limb pain and necrosis. Bleeding can occur spontaneously when the platelet count reaches very low levels, such as less than 10000 per microliter, though this is rare in HIT.

History

Heparin therapy

The history of HIT always includes exposure to heparin or heparinoids.

• Classic HIT: This occurs typically after 5-10 days of initiation of heparin or heparin-like 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 prior) and have circulating HIT antibodies. In these patients the median time of platelet fall is less than 12 hours after the start of heparin administration. Patients will typically have low platelet counts and possibly thrombosis.

• Delayed onset HIT: This occurs after heparin has been withdrawn (median time of 14 days after heparin withdrawal). Patients will typically have low platelet counts and possibly thrombosis.

Recent surgery

Patients with HIT often have a history of a recent cardiac or orthopedic surgery. They may develop low platelet count and deep vein thrombosis or other thrombotic manifestation.

• In cardiac surgery patients, decrease in the platelet count by > 50 % can occur within 3 days of surgery. This may be attributed to prolonged contact of platelets with the artificial surface and administration of large amount of unfractionated heparin (UFH). However, a diagnosis of HIT is more probable if a fall in the platelet count exceeds 50% is seen after 5-10 days of heparin therapy. Note that a history of surgery is not required as part of the history of HIT. Some patients with no surgical history will develop HIT.

Symptoms

Patients can present with symptoms suggestive of arterial and venous thrombosis. The increased incidences of thrombosis may be attributed to:

• Release of procoagulants by activated platelets
• Release of platelet membranes that in turn activates coagulation pathways
• Binding and activation of HIT antibodies to endothelial cells resulting in release of tissue factor and thrombin

Venous thrombosis

• Leg pain: This is a common manifestation of deep vein thrombosis. It typically occurs in the calf muscles. Homan's sign is pain on dorsiflexion of the calf.
• Leg swelling: This is a common manifestation of deep vein thrombosis. Swelling is due to obstruction of venous return and dilation of the surface veins.
• Leg erythema: This is a common manifestation of deep vein thrombosis.
• Dyspnea (new or worsening): This is a common manifestation of pulmonary embolism.
• Pleuritic chest pain: This can be a manifestation of pulmonary embolism.
• Sustained hypotension: This can be a manifestation of a massive pulmonary embolism.

Arterial thrombosis

The symptoms of arterial thrombosis are variable and depend on the organ involved. It can present itself as stroke, myocardial infarction, peripheral arterial occlusion, or end organ infarction (for example, renal dysfunction from renal artery occlusion).

Limb gangrene

This can be seen in both upper and lower extremities. However, lower extremities are more common compared to upper.

Skin necrosis

Skin necrosis is commonly seen in the abdomen, distal extremities, and nose.

• Redness of skin
• Purpura
• Bleeding from the skin

Bleeding

Bleeding can occur in the setting of thrombocytopenia. Spontaneous bleeding usually does not occur unless the platelet count is less than 10000 per microliter. Bleeding can occur at platelet counts below 50000 per microliter if a patient is undergoing an invasive procedure or experiences trauma.