Anticoagulation therapies, or treatments that reduce the amount of clotting factors in the blood, are quite common and used for a variety of reasons.
Typically, they are used to prevent major blood clotting complications, such as stroke and heart attack or blood clots brought on as a result of: trauma; major surgery, especially joint replacement surgery; or the presence of a mechanical heart valve. People at risk for one or more of these events are often administered a daily dose of anticoagulant medication. Anticoagulants may be administered orally, such as aspirin or warfarin, or intravenously or by subcutaneous injection (just under the skin), such as heparin and low-molecular-weight heparin (LMWH).
Despite improvements and standardization in the use of anticoagulants, many problems remain for clinicians. Two studies presented during the 46th Annual Meeting of the American Society of Hematology (ASH) help shed some light on anticoagulation therapy and add to the increasing knowledge necessary for the most effective application of this complex therapy.
"Millions of people successfully use anticoagulants every day, and several thousands of lives have been saved," said James George, M.D., President-Elect of the American Society of Hematology and Professor of Medicine at the University of Oklahoma Health Sciences Center, Oklahoma City. "However, there are a number of special populations that need to be cautious about the use of these treatments and need to be educated about how to properly take anticoagulants with other therapies."
Enoxaparin is Effective and Safe as Bridging Anticoagulation in Patients with a Mechanical Prosthetic Heart Valve Who Require Temporary Interruption of Warfarin Because of Surgery or an Invasive Procedure
People with severely damaged heart valves, which are prone to disease and malfunction, may have them replaced with prosthetic heart valves; too often, the body recognizes the prosthetics as foreign and attempts to protect itself from the invasion. As a result of this response, blood clots may form and cause serious problems if they travel to other parts of the body and become lodged in a blood vessel. To help counteract this problem, people with mechanical heart valves are often prescribed long-term warfarin, the most common oral-anticoagulation therapy, which reduces the amount of clotting factors in the blood, decreasing the incidence of blood clots. Warfarin is an oral anticoagulant that decreases the clotting ability of the blood and therefore helps to prevent harmful clots from forming in the blood vessels; it is more commonly known as a "blood thinner."
When patients on this maintenance therapy elect to undergo surgery or an invasive procedure of any type, they are at risk for a major bleeding event due to the warfarin therapy. It is standard procedure, therefore, to discontinue the warfarin and treat patients with enoxaparin (a low-molecular- weight heparin that is widely used in patients with acute coronary syndrome and venous thromboembolism) several days prior to the procedure and then resume the use of warfarin after the procedure. This is because the anticoagulant effect of enoxaparin is shorter than warfarin and therefore it can be adjusted to prevent excessive bleeding from the surgery. However, there is concern about enoxaparin's use in patients with mechanical prosthetic heart valves because of recent reports of fatal thromboembolism occurring in pregnant women with mechanical heart valves who received long-term enoxaparin therapy instead of warfarin, during pregnancy.
Researchers at McMaster University, Ontario, Canada, conducted a prospective study to assess the efficacy and safety of enoxaparin as a bridging anticoagulation therapy in patients with a mechanical prosthetic heart valve who require temporary interruption of warfarin therapy because of an elective surgical or other invasive procedure.
Results showed that enoxaparin appears to be effective and safe as a bridging anticoagulation therapy in patients with a mechanical prosthetic heart valve who require temporary interruption of warfarin therapy. After three months of clinical follow-up, only four patients developed non-fatal major bleeding events, one patient had a non-fatal stroke, and four patients died due to non-drug-related serious adverse events.
One hundred and seventy-four patients enrolled in this trial had warfarin interruption and bridging anticoagulation with subcutaneous enoxaparin, one mg/kg twice daily, and underwent clinical follow-up for three months after surgery. No patient was lost to follow-up. The incidence of major bleeding events, arterial thromboembolic events (such as stroke, transient ischemic attack, systemic embolism, valve thrombosis), and all-cause death were measured outcomes for this study. Warfarin therapy was resumed on the evening of or the day after the procedure.
Researchers concluded that enoxaparin is a practical approach to anticoagulant bridging in mechanical heart valve patients resulting in a low rate of bleeding and very low rates of thromboembolism. Patients who need to undergo anticoagulation bridging therapy, a standard medical practice with inherent risks now have a safe option available."
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