Fatal Heparin-Induced Thrombocytopenia 8 Months After Prior Exposureto Heparin

摘要

HEPARIN-INDUCED THROMBOCYTOPENIA (HIT) is a syndrome of thrombocytopenia caused by circulating Ig antibodies ("HIT antibodies") that bind to heparin platelet factor 4 complexes. HIT with thrombosis (HTTT) is HIT with the clinical syndrome of arterial or venous thrombosis because of platelet activation. The frequency of development of HIT antibodies depends on the type of heparin exposure (higher with unfractionated heparin [UFH] compared with low-molecular-weight heparin [LMWH]) and the patient population (surgical patients higher than medical patients). Cardiac surgical patients who are exposed to UFH perioperatively have a 50% incidence of detectable HIT antibodies. In orthopedic surgical patients, the incidence is 15% with exposure to UFH but only 8% with exposure to LMWH. Not all patients who develop HIT antibodies will become thrombocytopenic. Clinical HIT with thrombocytopenia below 100,0000muL is uncommon, and thrombosis (HITT) is rare (0%-5% of patients).