Efficacy and Safety of Low Molecular Weight Heparin Versus Unfractionated Heparin for Prevention of Venous Thromboembolism in Trauma Patients: A Systematic Review and Meta-Analysis.

Purpose Trauma patients are at high risk of venous thromboembolism (VTE). We summarize the efficacy and safety of low molecular weight heparin (LMWH) versus unfractionated heparin (UFH) for the prevention of VTE in trauma patients. Methods We searched six databases from inception through March 12th, 2021. We included randomized controlled trials (RCTs) or observational studies comparing LMWH vs UFH for thromboprophylaxis in adult trauma patients. We pooled effect estimates across RCTs and observational studies separately, using random-effects model and inverse variance weighting. We assessed risk of bias using the Cochrane tool for RCTs and the ROBINS-I tool for observational studies and assessed certainty of findings using GRADE methodology. Results We included 4 RCTs (879 patients) and 8 observational studies (306,747 patients). Based on pooled RCT data, compared to UFH, LMWH reduces deep vein thrombosis (DVT) (relative risk [RR] 0.67, 95% confidence interval [CI] 0.50 to 0.88, moderate certainty) and VTE (RR 0.68, 95% CI 0.51 to 0.90, moderate certainty). As compared to UFH, LMWH may reduce pulmonary embolism (adjusted odds ratio from pooled observational studies (aOR) 0.56 (95% CI 0.50 to 0.62) and mortality (aOR from pooled observational studies 0.54, 95% CI 0.45 to 0.65), though based on low certainty evidence. There was an uncertain effect on adverse events (RR from pooled RCTs 0.80, 95% CI 0.48 to 1.33, very low certainty) and heparin induced thrombocytopenia (RR from pooled RCTs 0.26 (95% CI 0.03 to 2.38, very low certainty). Conclusion Among adult trauma patients, LMWH is superior to UFH for DVT and VTE prevention and may additionally reduce pulmonary embolism and mortality. The impact on adverse events and heparin induced thrombocytopenia is uncertain.