Seminars in thrombosis and hemostasis
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Semin. Thromb. Hemost. · Feb 2015
ReviewVenous thromboembolism prophylaxis in critically ill patients.
Venous thromboembolism (VTE), including deep vein thrombosis (DVT) and pulmonary embolism (PE), is recognized as a common complication in critically ill patients. Risk factors including critical illness, mechanical ventilation, sedative medications, and central venous catheter insertion are major contributing factors to the high risk of VTE. Because of their impaired cardiopulmonary reserve, PE arising from thrombosis in the deep veins of the calf that propagates proximally is poorly tolerated by critically ill patients. ⋯ As a result, over the past decades, VTE prophylaxis had become a standard of preventive measure in the intensive care unit (ICU). In clinical practice, the rate of VTE prophylaxis varies and may be inadequate in some centers. A perception of a high bleeding risk in critically ill patients is a major concern for most physicians that may lead to inadequate prophylaxis.
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Semin. Thromb. Hemost. · Feb 2015
ReviewHemostasis and thrombosis in continuous renal replacement treatment.
During continuous renal replacement therapy, the delicate equilibrium of hemostasis is disturbed. Owing to a complex interaction of critical illness, uremia, use of an extracorporeal circuit and anticoagulation, patients exhibit both hypercoagulability and an increased risk of bleeding. Contact of blood with foreign material initiates coagulation by triggering the contact activation coagulation pathway, the tissue factor-factor VIIa pathway and activation of platelets and monocytes, which adhere to the membrane. ⋯ Its interference with anticoagulation is therefore unreliable during critical illness. Citrate provides regional anticoagulation and increases biocompatibility. It is better tolerated than heparin and confers less bleeding, less transfusion, and longer circuit life.
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Semin. Thromb. Hemost. · Feb 2015
ReviewHeparin-induced thrombocytopenia in critically ill patients.
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.
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Cardiac surgery with cardiopulmonary bypass determines a serious imbalance of the hemostatic system. The clinical pattern is multifactorial, involving patient-related, drug-related, and surgery-related factors. As a result, the patient is prone to both hemorrhagic and thrombotic complications. ⋯ Thromboembolic complications are the other side of the coin, and their prevention is still a matter of debate. Consumption of natural anticoagulants and endothelial disturbance are important mechanisms underlying this condition. Strategies to limit antithrombin (AT) consumption or to correct low postoperative levels of AT are still a matter of discussion.
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The antiphospholipid syndrome (APS) is characterized by venous or arterial thrombosis and/or pregnancy morbidity in patients with persistent presence of antiphospholipid antibodies (aPL). Patients who are diagnosed with APS are identified to have a high risk of recurrent thrombosis, which can occur despite anticoagulant therapy. ⋯ Recognizing that patients with APS may potentially have different thrombotic risk profiles may assist clinicians in assessing the risks, benefits, and optimal duration of anticoagulation. Future studies that delineate thrombotic risk in APS and evaluate current and novel anticoagulants as well as nonanticoagulant therapies are required.