Heparin-Induced Thrombocytopenia

Abstract

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder caused by antibodies that recognize complexes of platelet factor 4 (PF4) and heparin. HIT is frequently considered in the differential diagnosis of thrombocytopenia occurring in patients on heparin therapy. HIT is a challenging diagnosis because of routine heparin use in hospitalized patients, the common occurrence of thrombocytopenia, and high rates of anti-PF4/heparin seroconversions in patients treated with heparin. This chapter will summarize our diagnostic approach to HIT by underscoring critical elements of the clinical and laboratory evaluation. Keywordsplatelet factor 4; PF4; heparin; PF4/H complexes; HIT Heparin-induced thrombocytopenia (HIT) is a potentially life-threatening immune complication which occurs after exposure to unfractionated heparin (UFH) or less commonly, to low-molecular weight heparins (LMWHs). 1 It is characterized by declining platelet counts beginning 5-14 days after heparin exposure occurring in isolation (isolated HIT) or concurrent with new arterial and venous thrombotic complications. 2 HIT is caused by antibodies directed against complexes formed by a platelet protein, platelet factor 4, and heparin (PF4/H). Circulating immune complexes containing IgG and PF4/H complexes bind to platelet and monocyte Fc receptors and promote cellular activation leading to procoagulant microparticle release and thrombin generation. 3,4 Historically, the challenge associated with HIT was lack of awareness of the syndrome and its pursuant complications; the challenge now is in over-diagnosis and treatment of HIT. With the widespread availability of screening immunoassays and the desire of clinicians to avoid the thrombotic consequences associated with true disease, many patients without HIT Correspondence to: Gowthami M. Arepally, arepa001@mc.duke.edu. now suffer needless morbidity due to bleeding complications from use of alternative anticoagulants. To avoid a reflexive diagnosis of HIT in the heparinized thrombocytopenic patient, clinicians must have a sound understanding of the clinical and laboratory diagnostic elements essential for a diagnosis of HIT. This paper reviews our diagnostic and management strategy in evaluating the common presentation of thrombocytopenia in a heparinized patient. NIH Public Access Diagnosing HIT: the clinical challengeHIT is a challenging clinical diagnosis. The increasing use of UFH/LMWH for thromboprophylaxis in hospitalized patients 5 coupled with the frequency of thrombocytopenia, particularly among critically ill patients, 6 results in a significant overlap of patients suspected of HIT. In a recent registry of ~1000 patients treated with thromboprophylactic dosed heparin, 19% (n = 190) met thrombocytopenia criteria compatible with a diagnosis of HIT (as defined by a platelet count < 150 × 10 9 /L or > 50% drop in platelet counts), but only 5% of patients were diagnosed with HIT. 6 This study and clinical experience suggest that other causes of thrombocytopenia, such as infection, medi...

Trombocitopenia aguda pós-angioplastia coronária primária

“…3 Dois tipos distintos de plaquetopenia são associados à terapia com heparina. 4 A forma mais comum, que pode ocorrer em até 15% dos pacientes recebendo doses terapêuticas, é um efeito colateral benigno e autolimitado.…”

“…5 Os principais fatores de risco para esse distúr-bio são: uso da heparina > 4 dias, uso de heparina nos últimos 100 dias, heparina não-fracionada (a incidência com heparina de baixo peso molecular é 10% menor), pacientes cirúrgicos e sexo feminino. 3 O declínio plaquetário normalmente é moderado, com um nadir típico de 50-60 x 10 9 /l. Mais de 90% dos pacientes com trombocitopenia induzida pela heparina clínica têm queda da contagem plaquetária maior que 50% do basal durante o tratamento com heparina.…”

Prevention of venous thromboembolism in the Enhanced Recovery After Surgery (ERAS) setting: an evidence-based review

“…It may be safe to use heparin after this window, but expert opinion suggests the use of alternative agents in patients with a history of HIT, even if remote. 24 Low-molecular-weight heparin and UFH are the most widely studied agents for perioperative thromboprophylaxis. For surgical patients, evidence for DOAC use is limited to hip and knee arthroplasty.…”

The History of the Present Illness

“…The patient's blood platelet count is closely followed, as heparin-associated thrombocytopenia (HIT) can occur on heparin. 12 HIT always needs to be considered in a patient on heparin (unfractionated heparin or low molecular weight heparin) who develops a new thrombotic event or has a platelet count decrease of Ͼ30% from baseline or below 100 000ϫ10 6 /mL. It is a potentially devastating complication of unfractionated heparin, less commonly of low molecular weight heparin therapy.…”