Weight-adjusted versus fixed dose heparin thromboprophylaxis in hospitalized obese patients: A systematic review and meta-analysis

Background: Fixed dose unfractionated or low molecular weight heparin is the recommended treatment for venous thromboembolism (VTE) prevention in hospitalized patients. However, its efficacy has been questioned in obese population. Results of previous studies on weight-adjusted doses of heparin for VTE prevention are contradictory. Different anticoagulant regimens are used in clinical practice, but their role remains to be elucidated. Aims: To clarify the efficacy and safety of weight-adjusted dose heparin for VTE prevention in obese subjects hospitalized for medical and surgical conditions. Methods: Twelve studies were identified as reporting VTE occurrence, major or minor bleeding and anti-Xa levels. A random-effect meta-analysis was conducted to derive odds ratios (OR) comparing fixed vs weight adjusted-doses heparins on VTE occurrence, bleeding, anti-Xa levels. Medical and surgical patients, prospective vs retrospective and quality of studies were extracted for moderators and meta-regression analysis. Results: Weight-adjusted dose heparin administration was not associated with reduced VTE occurrence (6320/ 13317 patients, OR 1.03, 95% C.I. 0.79 to 1.35), nor increased bleeding (5840/10906 patients, OR 0.84, 95% C.I. 0.65 to 1.08), but it was associated with higher anti-Xa levels (284/294 patients, ES 2.04, 95% C.I. 1.16 to 2.92, p<0.0001). A significant heterogeneity was present for comparison of anti-Xa levels (I2=94%, p=0.0001) but not for VTE occurrence or bleeding (I2=7.6% and 12.8% respectivel). None of the moderators explained the heterogeneity of the results among primary studies. Conclusion: Weight-adjusted dose as compared to fixed-dose of heparins in the prevention of VTE in obese patients was not associated with a lower risk of VTE nor a higher risk of bleeding.

Automated summary

In obese hospitalized patients, weight-adjusted dose heparin is not associated with a lower risk of VTE or a higher risk of bleeding compared to fixed-dose heparins. However, it is associated with higher anti-Xa levels.