Heparin-induced thrombocytopenia (HIT) is an antibody mediated adverse reaction to heparin involving 1% ~ 2% of patients treated with heparin for more than 4 days.The clinical picture of HIT is characterized by isolated thrombocytopenia,or thrombocytopenia combined with the occurrence of thromboembolic complications,including deep venous thrombosis,pulmonary emboli,myocardial infarction,cerebral vascular accident,peripheral ischemic events,and others and is associated with up to a 50% morbidity and mortality.Patients who present for cardiopulmonary bypass (CPB) operations with HIT present unique problems for surgical,anesthesia and medical management,with greatly increased risk intra-and postoperative thromboembolic complications.