The value of the anticoagulants as antithrombotic agents has been best assessed by studying their effectiveness in preventing and treating venous thromboembolic disease. Oral anticoagulants have been repeatedly shown to prevent venous thrombosis and pulmonary embolism in patients at high risk of developing these complications. However, the increased risk of postoperative bleeding has prevented their widespread use for this purpose in surgical patients. Recently, the use of low doses of heparin, given subcutaneously before and after surgery, has been shown to markedly reduce the incidence of venous thrombosis and pulmonary embolism (including fatal pulmonary embolism) after major elective abdominal surgery, and to produce only a slight increase of postoperative bleeding. This represents a major advance in anticoagulant prophylaxis of venous thromboembolism in surgical patients. However, low dose heparin prophylaxis is relatively ineffective in patients having hip surgery, and has not been evaluated in patients having other types of orthopaedic surgery. The defibrinating agent ancrod has had limited clinical trial, but appears to give no advantages over heparin. Intravenous infusion of dextran, a glucose polymer, has been shown to have an antithrombotic effect in many experimental models of thrombosis. However, the evidence that dextran is a clinically valuable antithrombotic drug is conflicting. A number of controlled randomised studies have shown that dextran can prevent postoperative venous thromboembolism when a large volume of dextran 40 or 70 was infused rapidly during and after surgery. However, blood volume expansion during dextran treatment prohibits its use in patients with reduced cardiac reserve, and infrequent though sometimes severe, allergic reactions have been reported. Evidence that dextran is of value for the treatment of venous or arterial thromboembolism comes from uncontrolled studies and is not convincing.
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|Published - 1976