Meta-analysis of venous thromboembolism prophylaxis in medically Ill patients

Venous thromboembolism (VTE) prophylaxis in medically ill patients has received a level 1A recommendation in previously published clinical guidelines. Pharmacologic prophylaxis for VTE includes unfractionated heparin (UFH), low-molecular-weight heparin (LMWH), and fondaparinux. Few direct comparisons between anticoagulants exist in medically ill patients.

This meta-analysis was conducted to assess UFH and LMWH (including the selective factor Xa inhibitor fondaparinux) in the reduction of in-hospital VTE in unselected medically ill patients.

We searched MEDLINE, EMBASE, and the Cochrane Controlled Trials Registry databases from January 1981 through September 2007 (English language) for randomized controlled trials using the following terms: dalteparin, enoxaparin, fondaparinux, nadroparin, and heparin. References of included articles and key review papers for additional studies were also searched. Data from studies were included in the analysis if the studies included medically ill patients with risk factors for VTE who had been followed up for 7 to 21 days.

A total of 12,391 patients (of whom 8357 were in placebo-controlled trials) from 9 studies were included. Mean age for the entire cohort was 72.8 years; mean (SD) body mass index, 25.6 kg/m2; and mean (SD) actual body weight, 68.2 kg. Deep vein thrombosis (DVT) was significantly reduced with the addition of an LMWH compared with placebo (odds ratio [OR], 0.60; 95% CI, 0.47-0.75; P < or = 0.001), but rates of DVT were similar when comparing LMWH with UFH (OR, 0.92; 95% CI, 0.56-1.52). No significant differences in pulmonary embolism (PE) or death were found among the UFH, LMWH, and placebo groups. LMWH was associated with a significant increased risk for minor bleeding compared with placebo (OR, 1.64; 95% CI, 1.18-2.29; P = 0.003). However, no significant difference was found between LMWH and UFH (OR, 0.68; 95% CI, 0.27-1.70). Major bleeding events were similar among all groups: LMWH/fondaparinux versus placebo, OR, 1.65 (95% CI, 0.8-3.4); LMWH/fondaparinux versus UFH, OR, 0.69 (95% CI, 0.29-1.68); LMWH/fondaparinux versus UFH or placebo, OR, 1.16 (95% CI, 0.66-2.04).

This analysis suggests that VTE prophylaxis with an LMWH (including fondaparinux) or UFH is effective in reducing the rate of DVT, but this benefit did not extend to enhanced protection against PE. Additionally, LMWH and UFH had similar bleeding outcomes.