Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT type II) is a potentially serious adverse drug effect. Unlike other drug-induced thrombocytopenias which cause bleeding, HIT type II causes thrombosis leading to limb gangrene or even death. HIT type II is mediated by an IgG antibody to the heparin-platelet factor 4 (PF4) complex. The antibody-heparin-PF4 complex binds to platelet surface receptors and induces platelet activation and aggregation, and simultaneously, activates blood coagulation pathways and endothelial tissue factor. Diagnosis of HIT type II is made on clinical criteria, supported whenever possible by laboratory tests. Several approaches are available in the perioperative management of a patient with acute or recent HIT type II presenting for surgery.