Topical Issues in Venous Thromboembolism

Abstract

Despite clear guidelines and the availability of effective treatments, venous thromboembolism (VTE) remains relatively common, particularly in the hospital setting. This paper reviews topical issues in VTE, in terms of treatments, data and guidelines. Existing anticoagulants have several limitations. Bleeding risk is a concern with all anticoagulants. Vitamin K antagonists are the mainstay of oral anticoagulant therapy, but they are limited by the need for frequent monitoring. Unfractionated heparin (UFH) is limited by an inconvenient route of administration (continuous intravenous infusion) and a higher risk of heparin-induced thrombocytopenia and bleeding compared with low molecular weight heparins (LMWH). LMWH have a more predictable pharmacokinetic profile and greater bioavailability than UFH, which permits weight-adjusted LMWH dosing without the need for monitoring in most patients. LMWH also have a more convenient dosing strategy than UFH (once-daily subcutaneous injection). Fondaparinux is a selective inhibitor of factor Xa and, like LMWH, does not require monitoring. The efficacy of fondaparinux in long-term VTE treatment remains to be established. The optimal time to initiate thromboprophylaxis in patients undergoing orthopaedic surgery remains controversial. Initiating thromboprophylaxis just before or soon after surgery (the 'just-in-time' strategy) achieves better thromboprophylaxis but could increase the risk of bleeding complications. Balancing the need for extended thromboprophylaxis after major surgery with the need to minimize bleeding remains an important consideration. Despite clear guidelines, thromboprophylaxis is widely underused, particularly in medical patients, in whom rates as low as 28% have been reported. Electronic alert systems may be of value for increasing the use of adequate thromboprophylaxis. The use of different definitions of VTE and bleeding in clinical trials, together with missing venography data, conflicting guidelines in patients undergoing total hip or knee arthroplasty, and the limited amount of data in children, also make VTE prevention and management more difficult. Administering thromboprophylaxis to a wider group of patients, employing the 'just-in-time' protocols, ensuring adequate duration of thromboprophylaxis, combining different methods of thromboprophylaxis and developing new anticoagulants should help to improve thromboprophylaxis.