title: Heparin-induced thrombocytopenia in critically ill patients.
abstract: Many critically ill patients receive heparin, either before intensive care unit (ICU) admission (e.g., postcardiac surgery), for prophylaxis/treatment of thrombosis, for hemodialysis/filtration, or even incidentally (e.g., flushing of intravascular catheters), and are therefore at risk for developing immune heparin-induced thrombocytopenia (HIT), a prothrombotic drug reaction caused by platelet-activating antiplatelet factor 4 (PF4)/heparin antibodies. However, HIT explains at most 1 in 100 thrombocytopenic ICU patients (HIT frequency 0.3-0.5% vs. 30-50% background frequency of ICU-associated thrombocytopenia), and most patients who form anti-PF4/heparin antibodies do not develop HIT; hence, HIT overdiagnosis often occurs. This review discusses HIT-related issues relevant to ICU patients, including how to (1) distinguish HIT both clinically and serologically from non-HIT-related thrombocytopenia; (2) recognize HIT-mimicking disorders, such as the acute disseminated intravascular coagulation (DIC)/liver necrosis-limb necrosis syndrome; (3) prevent HIT in the ICU through use of low-molecular-weight heparin; and (4) treat HIT, including awareness of "PTT confounding" when anticoagulating patients with DIC.
authors.affiliation: Department of Pathology and Molecular Medicine, Michael G. DeGroote School of Medicine, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Theodore E
authors.initials: TE
authors.lastname: Warkentin
mesh_terms: D000925:Anticoagulants / Q000009:adverse effects*; D016638:Critical Illness; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D013921:Thrombocytopenia / Q000139:chemically induced*
chemical_list: D000925:Anticoagulants; D006493:Heparin