Seminars in respiratory and critical care medicine
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Massive pulmonary embolism (PE) with hemodynamic instability (e.g., hypotension and cardiac shock) is associated with a poor prognosis and high mortality rates (> 50%). Accordingly patients with massive PE should be treated aggressively with thrombolytic agents (or surgical or interventional procedures). Streptokinase, urokinase, and recombinant tissue plasminogen activator (rtPA) have been used, with generally similar results. ⋯ This article reviews indications for thrombolysis in massive PE, with an emphasis on recent data derived from normotensive patients. Further, we propose a diagnostic and therapeutic algorithm for treating acute PE. Additional studies are required to determine the benefit and safety of thrombolytic therapy for PE.
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Semin Respir Crit Care Med · Feb 2008
ReviewThrombophilias: when should we test and how does it help?
Venous thromboembolism can be a life-threatening event, occurring in ~1 in 1000 adults annually. An underlying cause for thrombosis can now be identified in up to 80% of cases, including both inherited and acquired causes of thrombophilia. ⋯ This article reviews both the inherited and the acquired causes of thrombophilia, focusing on the clinical scenarios in which these disorders should be suspected and on how to appropriately test for them when clinically indicated. By the conclusion of this article, the clinician should be equipped with an algorithm of how to approach a patient with a thromboembolic event, from decisions regarding which thrombophilia tests to order to how the results of these tests affect patient management.
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Heparin-induced thrombocytopenia (HIT) is a prothrombotic drug reaction caused by platelet-activating antibodies that recognize multimolecular complexes of platelet factor 4 (PF4) bound to heparin. HIT is an intense hypercoagulability state (increased thrombin generation in vivo) that is complicated more often by venous thromboembolism (deep vein thrombosis, pulmonary embolism) than by arterial thrombosis. HIT is a risk factor for coumarin-induced microthrombosis, particularly affecting acral regions of limbs with deep vein thrombosis (venous limb gangrene). ⋯ Recognition of HIT may be facilitated through the use of a clinical scoring system, the 4Ts ( Thrombocytopenia, Thrombosis, Timing, and o Ther explanations). Anti-PF4/polyanion enzyme-immunoassays (EIAs) and washed platelet activation assays readily detect HIT antibodies, and thus have high diagnostic sensitivity; however, only the platelet activation assays have high diagnostic specificity, suggesting that HIT is likely to be overdiagnosed in settings where EIAs are used exclusively for diagnosis. Treatment of HIT emphasizes substitution of heparin with an alternative nonheparin anticoagulant, such as a direct thrombin inhibitor (lepirudin, argatroban), or an indirect (antithrombin-mediated) inhibitor of factor Xa (danaparoid, fondaparinux?).
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Semin Respir Crit Care Med · Feb 2008
ReviewInterventional approaches to acute venous thromboembolism.
During the last decade, advances in minimally invasive technologies have spurred a renaissance in the aggressive treatment of venous thromboembolism (VTE) using percutaneous techniques. In this article, we outline the relative risks and benefits of endovascular VTE therapies, highlight clinical situations in which the benefits of endovascular treatment are likely to outweigh its risks, and provide an update regarding the specific new modalities that may be applied to VTE. Pharmacomechanical thrombolysis represents the most promising currently available method to treat VTE. ⋯ At present, highly compromised patients with pulmonary emboli (PE) in whom systemic thrombolytic therapy has failed or is contraindicated are reasonable candidates for catheter-based PE interventions. Adjunctive pharmacomechanical catheter-directed deep venous thrombosis (DVT) thrombolysis is best indicated for the first-line treatment of patients with phlegmasia cerulea dolens, acute inferior vena cava (IVC) occlusion, and acute iliofemoral DVT after careful clinical assessment and a balanced discussion with the patient. It is hoped that multidisciplinary clinical trials with involvement by both interventionalists and pulmonary physicians will validate these techniques in the near future.