Heparin-induced thrombocytopenia(HIT)More than 12 million Americans have been treated with heparin annually．Heparin-induced thrombocytopenia(HIT)has become one of the most devastating and serious immune-mediated adverse drug reactions in current clinical practice．In the United States alone，the annual estimated health care cost of HIT associated complications in cardiac surgery is about$300 million(1，2)．HIT is the development of thrombocytopenia secondary to administration of heparin，typically 5 t0 14 days after exposure．Low-molecular weight heparin(LMWH)Can also cause HIT，but at significantly lower rates． Despite of the low platelet count,HIT is a prothrombotic disorder presented with thrombosis in the venous and arterial microvasculature，which Can lead to catastrophic sequela such as limb gangrene or life-threatening thromboembolic complications(1-4)．HIT exists in two forms．Type I HIT is a common，non-immunologic phenomenon occurring in up to 20％ of all patients involving a transient decrease in platelets following administration ofheparin．Type I HIT resolves even with the continued administration of heparin．
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