Level 2: Mid-level evidence

Fondaparinux (Arixtra) may prevent symptomatic and asymptomatic venous thromboembolism in bedridden hospital patients with an acute illness (BMJ. 2006;332:325-329; full-text available online without charge at www.bmj.com/cgi/content/full/332/7537/325. Accessed March 15, 2007). This finding is based on a trial with 849 medical inpatients aged 60 years and older who were randomized to fondaparinux 2.5 mg or placebo subcutaneously once daily for 6-14 days. Patients were hospitalized for congestive heart failure, acute respiratory illness (in the presence of chronic lung disease), or acute infectious or inflammatory disease and were expected to remain in bed for at least four days. Exclusion criteria included high risk for bleeding, acute bacterial endocarditis, cerebral metastasis, recent stroke, central nervous system (CNS) surgery, CNS catheter, anticipated intubation for >24 hours, and serum creatinine >2.04 mg/dL (180 µmol/L) when well hydrated. The use of aspirin or other nonsteroidal anti-inflammatory drugs was discouraged; compression stockings and physiotherapy were allowed.

The primary efficacy analysis included 644 patients (76%) with evaluable venograms (134 patients did not have venography, 61 patients had a nonevaluable venogram, and 10 patients did not receive treatment). Comparing fondaparinux vs. placebo, 5.6% vs. 10.5% had venous thromboembolism on bilateral venography at 6-15 days (NNT 20) and 0% vs. 1.5% (five patients) had symptomatic venous thromboembolism (NNT 65). Based on 829 patients who received medication, one patient in each group had major bleeding (0.2% vs 0.2%) and 2.6% vs. 1% had minor bleeding. The mortality rates at 32 days were 3.3% vs. 6% (P =0.06), which included three (0.7%) vs. seven (1.7%) deaths due to pulmonary embolism and two (0.5%) vs. one (0.25%) death due to bleeding.

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