Seminars in thrombosis and hemostasis
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Semin. Thromb. Hemost. · Apr 2011
Case ReportsPractical viewpoints on the diagnosis and management of heparin-induced thrombocytopenia.
Heparin-induced thrombocytopenia (HIT, type II) is an immune-mediated disorder due to antibodies formed against heparin-platelet factor 4 complexes, usually appearing at days 5 to 14 after initiation of heparin. It is important to recognize HIT because heparin prophylaxis or treatment paradoxically associates with new venous and/or arterial thrombosis. Early clinical suspicion and diagnosis together with proper pharmacotherapy and close laboratory monitoring are the cornerstones for successful management. ⋯ New anticoagulants and platelet inhibitors may offer future alternatives in the management of HIT, but the current treatment options provide the best experience and benefit. The joint clinical and laboratory guidelines provided in this article along with two practical case scenarios were prepared by a Nordic expert panel. They will be valuable for hematologists and colleagues who do not routinely encounter HIT.
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Semin. Thromb. Hemost. · Apr 2011
ReviewPreventing postsurgical venous thromboembolism: pharmacological approaches.
The use of antithrombotic drugs for the prevention of venous thromboembolism (VTE) in patients undergoing surgery is presently based on solid principles and high-level scientific evidence. This article reviews current strategies of pharmacological thromboprophylaxis. The level of VTE risk following surgery depends on a variety of factors that the surgeon should take into account, including the type of surgery and the presence of additional risk factors, such as elderly age and cancer. ⋯ Patients undergoing major orthopedic surgery have a particularly high risk of VTE, and routine thromboprophylaxis with LMWH, fondaparinux, or a vitamin K antagonist (international normalized ratio target: 2.0 to 3.0) is the standard of care in this group of patients. Recently, two new oral anticoagulants, rivaroxaban (a factor Xa inhibitor) and dabigatran etexilate (a direct thrombin inhibitor) have been licensed to be used for thromboprophylaxis after orthopedic surgery in Europe. Mechanical methods of thromboprophylaxis (compression stockings, intermittent pneumatic compression, vena cava filters), not discussed in detail in this review, should always be considered in patients at high thrombotic risk, in association with the pharmacological strategies, or in cases of contraindications to anticoagulants, as in patients or procedures at high risk of bleeding.
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Sickle cell disease (SCD) is characterized by the presence of sickle hemoglobin, which has the unique property of polymerizing when deoxygenated. The pathophysiology of acute and chronic clinical manifestations of SCD have shown the central role of dense, dehydrated red cells in acute and chronic clinical manifestations of this pathology. ⋯ This review discusses, in the context of SCD, (1) abnormalities in the coagulation system, (2) perturbation of platelet activation and aggregation, (3) vascular endothelial dysfunction, (4) the contribution of cell inflammatory responses, and (5) the connection with nitric oxide metabolism. We also review the available studies on the therapeutic approaches in clinical management of hypercoagulability in SCD.
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Semin. Thromb. Hemost. · Apr 2011
Comparative StudyPrevention of venous thromboembolism: focus on mechanical prophylaxis.
Venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism, is a leading health-care problem whose pathogenesis is usually related to the so-called Virchow's triad and involves a variety of factors classified as inherited or acquired, predisposing, or triggers. The main goal of thromboprophylaxis is to reduce mortality and morbidity associated with VTE risk factors. Although striking evidence now indicates that the various pharmacological anticoagulant therapies can substantially lower the risk, this benefit might be offset by a small but definite risk of hemorrhage in some circumstances. ⋯ The main mechanism of action appears to be related to a milking (wavelike) effect to evacuate leg veins and reduce venous stasis because an effect on the enhancement of fibrinolysis remains unproven. Although the biological and clinical evidence suggests that graduate compression stockings are an effective, relatively cheap, and more comfortable thromboprophylactic measure, they appear less effective overall than intermittent pneumatic compression. In conclusion, although the preventive benefits of mechanical prophylaxis on VTE might be circumscribed to select medical and surgical settings, there appears to exist no clinical reason to discourage adoption of these measures when indicated.