POWERS

Warfarin vs. ASA for the prevention of venous thromboembolism in patients undergoing surgery for fractured hip (1989)

Condition

Prophylaxis for VTE in patients admitted for surgery because of hip fracture

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Objective

To compare the efficacy and safety of warfarin and ASA for VTE prophylaxis after surgery for fractured hip

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Trial design

Randomized, double-blinded (ASA), placebo-controlled study
Active treatment: warfarin 10 mg as soon as possible after surgery, followed by adjusted daily doses to achieve an aPTT of 16 s by the 5th postoperative day and to maintain an aPTT of 16–18 s (INR 2.0–2.7) up to day 21 after surgery or discharge from hospital (n=65)
Control treatment: ASA 650 mg (n=66) or ASA placebo (n=63) twice daily for 21 days or until hospital discharge

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Endpoints

Primary efficacy endpoint: DVT and PE during the postoperative period
Primary safety endpoints: major and minor bleeding
Secondary endpoints: blood transfusion requirement, death

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Trial participants

194 consecutive patients (aged 30–91 years) admitted for surgical treatment of hip fracture

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Results

Efficacy outcome: DVT and/or PE was detected in 13 of 65 patients (20.0%) in the warfarin group, 27 of 66 patients (40.9%) in the ASA group, and 29 of 63 patients (46.0%) in the placebo group. The difference between warfarin and ASA was statistically significant (p=0.005). Proximal DVT occurred in 9.2% of the warfarin-treated patients, 10.6% of the patients given ASA and 30.2% in the patients assigned to placebo. The differences between the placebo group and either the warfarin or ASA group were statistically significant (p=0.001). One patient receiving ASA and 2 patients receiving placebo developed PE (1.5% and 3.2% respectively)
Safety outcome: Major bleeding occurred in 5 patients in each of the warfarin and placebo groups and in 1 patient given ASA (8.0%, 7.9%, and 1.5%, respectively); none of theses bleeding episodes was fatal. Clinical important major and minor hemorrhage was observed in 6 patients (9.2%) treated with warfarin, 3 patients (4.5%) given ASA, and 6 patients (9.5%) in the placebo group. The number of patients who needed blood transfusions was similar across treatment groups. 6 patients died during the 21-day treatment period: 2 in the warfarin group, 3 in the ASA group and 1 on the placebo group

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Summary

Efficacy: In patients undergoing surgery for hip fracture, less intensive warfarin was significantly much more effective than ASA or placebo in preventing VTE, and there was little difference between ASA and placebo
Safety: In patients treated with warfarin, there was no increase in bleeding complications, as compared with the ASA and placebo groups

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Reference

Powers PJ, Gent M, Jay RM, Julian DH, Turpie AG, Levine M, Hirsh J. A randomized trial of less intense postoperative warfarin or aspirin therapy in the prevention of venous thromboembolism after surgery for fractured hip. Arch Intern Med 1989;149:771-774

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Corresponding author

Peter J. Powers, MD, St. Joseph’s Hospital, 50 Charlton Ave E, Hamilton, Ontario, Canada L8N 4A6

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