Low Molecular Weight Heparin Prophylaxis in Total Knee Arthroplasty: The Answer

Venous thrombosis continues to be a major risk after total knee arthroplasty. Without prophylaxis, the prevalence of deep vein thrombosis is as high as 84%, with proximal occurrence as high as 20%. Of more concern is the occurrence of pulmonary embolism as high as 7%, with fatal pulmonary embolism as high as 0.7%. This high prevalence mandates that prophylaxis for thromboembolic disease be used for patients undergoing total knee arthroplasty. Low molecular weight heparin has been studied extensively and is safe and effective prophylaxis after total knee arthroplasty. Low molecular weight heparins have a predictable dose response, offer high bioavailability at low doses, and produce linear pharmacokinetics. It has a half-life of approximately 4.5 hours providing effective dosing every 12 to 24 hours with rapid antithrombotic action. Routine pharmacologic prophylaxis with low molecular weight heparin seems to be effective in decreasing the occurrence of venous thromboembolism. However, venographic prevalence of deep vein thrombosis among patients undergoing total knee arthroplasty and receiving prophylaxis remains substantial at 30.6%. Prophylaxis with low molecular weight heparin beyond hospitalization may be indicated with decreased hospital stays, although studies have not been convincing that extended outpatient prophylaxis for more then 7 to 10 days is necessary.