Ardeparin (low-molecular-weight heparin) vs graduated compression stockings for the prevention of venous thromboembolism - A randomized trial in patients undergoing knee surgery

Background: Deep vein thrombosis is common in patients undergoing major knee surgery. Static graduated compression stockings effectively prevent venous thrombosis in general surgery. Because of the demonstrated prophylactic efficacy of pneumatic compression in knee surgery, the similar efficacy of static graduated compression and pneumatic compression in neurosurgery, and the easier use of static graduated compression in knee surgery, graduated static compression stockings were used as the control arm in our clinical trial. Although low-molecular-weight heparin had been shown to be effective in general surgery and hip replacement, its efficacy was unproved in knee surgery. Methods: A double-blind, randomized trial compared the combination of low-molecular-weight heparin and graduated compression stockings with graduated compression stockings alone in patients undergoing major knee surgery. Patients received either ardeparin (Normiflo) (low-molecular-weight heparin), 0.005 mL/kg (50 anti-Xa U/kg), or placebo. Both were administered subcutaneously twice daily commencing 12 to 24 hours after surgery and continued for 14 days or until discharge, if sooner. Both study groups wore graduated compression stockings. Bilateral venography was performed on day 14, or sooner if the patient was ready for discharge. Results: One hundred twenty-two patients were allocated to receive ardeparin and 124 received placebo. Ninety-six patients in the ardeparin group and 103 in the placebo group had evaluable venograms. Deep vein thrombosis was detected in 28 patients in the ardeparin group and in 60 in the placebo group. Proximal deep vein thrombosis was detected in two patients who received ardeparin and 16 who received placebo. One patient in each group, both of whom did not have venography, experienced pulmonary embolism. Thus, deep vein thrombosis or pulmonary embolism was detected in 29 (29.9%) of the 97 patients in the ardeparin group and in 61 (58.7%) of the 104 patients in the placebo group, a relative risk reduction of 49% (P<.001). The rate of major bleeding in the ardeparin group was 2.5%, compared with 2.4% in the placebo group. Conclusion: Ardeparin administered postoperatively twice daily is effective and safe for the prevention of venous thrombosis in patients undergoing major knee surgery. Whereas graduated compression stockings have been shown to be effective prophylactic agents in general surgery and neurosurgery, they have little effect in knee surgery.