Heparin-induced thrombocytopenia during extracorporeal membrane oxygenation

摘要

HEPARIN-INDUCED THROMBOCYTOPENIA (HIT) is an immune-mediated adverse effect of heparin therapy. Two clinical entities of HIT can be distinguished: HIT I and HIT n. HIT I is a harmless pharmacologic phenomenon associated with decreased platelet count within 24-48 h after initiation of heparinization. Unlike HIT n, it is not associated with thrombosis and does not necessitate discontinuation of heparin. In contrast, HIT II can cause both bleeding and thrombotic complications. It is the most important and most frequent drug-induced immunologic thrombocytopenia.Besides orthopedic and vascular surgery patients, patients after cardiac surgery are at highest risk of developing HIT II (1-5%). Its clinical importance is based on its strong association with venous and arterial thrombosis and thromboembolism (heparin-induced thrombocytopenia with associated thrombosis, HITT). HIT is caused by the development of an IgG antibody that recognizes multimolecular complexes of platelet factor 4 (PF4) and heparin.