Heparin Induced Thrombocytopenia

HIT or Heparin induced thrombocytopenia is reported in patients who are under the treatment of UFH for 5 or more days. The patients suffering from this complication can develop arterial or venous thrombosis. That is why this subset of symptoms is also known as Heparin Induced Thrombocytopenia and thrombosis syndrome (HITTS). This complication of Heparin is a immune mediated syndrome. Heparin produce specific type of immunoglobulins which bridge the platelets. As a result this mechanism can cause both thrombocytopenia and thrombosis. In some patients the onset of HIT occurs after the discontinuation of the heparin therapy. This condition is known as delayed onset HIT.
Heparin therapy should be immediately stopped on the suspicion of HIT. Laboratory tests are available which can confirm the diagnosis of this complication. As HIT can also cause thrombosis so the patient needs an alternate form of anticoagulant therapy. Some drugs which are used for the therapy of HIT are lepirudin, argatroban and bivalirudin. Argatroban can be given to a patient suffering from HIT and needs PCI for ACS. Argatroban is a direct thrombin inhibitor. Argatroban can be given as a bolus of 240 -mcg/ kg bolus which is followed by 20-mcg/kg infusion per minute. This drug can be given even without GP IIb/IIIa blockade.

Heparin - The Acute Anticoagulant

Heparin which is also known as unfractioned Heparin is an Injectable anticoagulant work wonders in emergency situations like ACS and venous thrombosis. Heparin is a hetrogenous mucopolysaccharide. It mainly acts on the interaction of antithrombin and thrombin (factor lla). This drug inhibits the thrombin induced platelet aggregation. Heparin silmentaneously binds to thrombin and antithrombin. Heparin - Antithrombin complex also inhibits fator xa and xia and other factors which are part of intrinsic coagulation pathway. This drug mainly binds to proteins, macrophages as well as endothelial cells. This binding property of drug inactivates some part of drug. This anticoagulant can also induce thrombocytopenia in some cases. The dose of heparin needs to be controlled and monitored. Heparin is not excreted by kidneys so it can be easily prescribed to the patients suffering from renal diseases.

The Administration and Dose Control of intravenous Heparin


Heparin is usually diluted with normal saline or dextrose. As per European recommendations the heaparin should be given as a bolus of 60 - 70 IU/Kg , upto 5000 IU. The bolus should be followed by an infusion of 12-15 IU/ Kg (Maximum 1000 IU/Kg). The dose of the drug is adjusted with the help of aPTT levels. The aPTT value should be maintained 1.5 - 2.5 times the control aPTT value. The aPTT values can also be maintained from 50 to 75 seconds. The aPTT value should be monitored every 6 hrs. Higher aPTT values can result in cerebral bleeding. ACT or activated clotting time can also be used to control the dose of heparin in catherization laborateries and on the bed side.

Precautions should be taken to reduce the side effects and complications of the drug. The heparin infusion should not be continued more than 48 hours. Long duration infusions of heparin can result in HIT (Heparin Induced Thrombocytopenia). Patients suffering from hemophilia, SABE, GI tract ulcers and hepatic diseases are more prone to heparin induced bleeding disorders. Heparin can cause allergy in some patients because the drug is derived from animal tissue. In case of overdosage ,heparin should be stopped immediately and a slow infusion of 1% protamine sulfate should be started.