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Letter to the Editor

Editor, – The article by Professor Gallus (Aust Prescr 2010;33:42–7) discussed the clinical applications of the new oral anticoagulants – rivaroxaban and dabigatran. In those patients who had had hip or knee replacements, the new drugs were started either 6–8 hours after wound closure or 1–4 hours after surgery. Would Professor Gallus kindly give his advice to orthopaedic surgeons for those patients who have had a previous deep vein thrombosis or who possess one of the inherited thrombotic tendencies such as Factor V Leiden mutation.

JL Raven
Clinical haematologist and Consultant physician
Waikiki Private Hospital
Waikiki, WA

Author's comments

Professor Alex Gallus, author of the article, comments:

Patients with a previous deep vein thrombosis or pulmonary embolism pose special problems for surgeons because of their increased risk of a postoperative recurrence. After recent venous thromboembolism, elective surgery should be delayed for at least 3–6 months to permit the initially high risk for a recurrence to subside. Beyond 3–6 months, individual practice varies, since there is little good evidence to guide the clinician.

One common approach is to add intermittent pneumatic leg compression to low molecular weight heparin prophylaxis, and start warfarin once the postoperative bleeding risk allows. The duration of warfarin treatment would then depend on whether the patient's history justifies long-term therapy. It is not yet known if prophylactic doses of the new oral anticoagulants can replace warfarin for the secondary prevention of venous thromboembolism. In the dabigatran and rivaroxaban studies of prophylaxis after joint replacement, 2–4% of patients reported a history of venous thrombosis. This was too few for meaningful subgroup analyses of relative efficacy.

There is substantial evidence that heterozygosity for Factor V Leiden or the G20210A prothrombin gene mutation, without a personal history of thromboembolism, does not raise the risk of postoperative thrombosis above the average. In these patients, standard prophylactic dosing regimens should be sufficient. Risk associated with homozygosity or double heterozygosity, however, is well above average and would need more intense and longer prophylaxis.