Low Dose Warfarin Is Effective Prophylaxis Against Deep Vein Thrombosis Following Total Hip Arthroplasty.

Thromboembolic disease (TED) including deep vein thrombosis (DVT) and pulmonary embolus (PE) remain major complications following total hip arthoplasty. Warfarin is an important pharmacologic prophylaxis against these complications. How to optimally use warfarin remains a sourse of debate. This retrospective patient report extends eariler observations that low dose warfarin is effective prophylaxis against symptomatic thromboembolic disease. Patients planned for elective unilateral total hip replacement were given 1 mg of warfarin for 7 days prior to surgery. Patients were excluded from this regimen if they had a coagulopathy, platelet count less than 140,000/mm³, previous TED, cancer, or were in need of long term anticogulation for other reasons. Prothrombin times were measured on the morning of surgery. The night following surgery they were prescribed variable dose warfarin which was continued while in hospital, with target INR 1.5–2.0. They were discharged to rehabilitation centers or home taking 1 mg daily until their 4–6 week followup visit. All patients received post-operative pneumatic compression stockings, followed by elastic compression stockings when ambulatory. Patients were encouraged to begin isometric exercises immediately after surgery and were mobilized on day 1 or 2 following surgery. Hospital and clinic charts for 13 months of consecutive patients were reviewed for any evidence of TED. Auxiliary data basis were probed for any additional evidence of TED, including the hospital logs of Radiology Department, Orthopedic Department Morbidity and Mortality rounds, Adverse Events, Medical Records Department, and Case Management. There were 833 primary and 170 revision total hip athroplasties. Of the 1003 patients studied, 3 had TED (0.3%, 95% CI 0.0–0.6), including 2 with DVT and l with nonfatel PE. The followup rate was 98.9%, with 11 patients lost to follow-up. Complications from the warfarin were minimal. The prothrombin times on the morning of surgery were below INR 1.4 for 98.9% of the patients. Two patients with INR greater than 1.49 on day of surgery received fresh frozen plasma. Seven patients had post-operative wound hematomas, one of which had INR greater than 1.5. Very low warfarin when started preopartively, continued as variable dose in the immediate postoperative period, and continued at 1 mg until the patient is fully ambulatory, combined with the mechanical tools listed, is effective and safe prophylaxis against TED.