Low molecular weight heparin and unfractionated heparin in thrombosis prophylaxis after major surgical intervention: Update of previous meta-analyses

Background Previous meta-analyses comparing low molecular weight heparin (LMWH) and unfractionated heparin for thrombosis prophylaxis after surgical interventions need updating. Methods This is a publication-based meta-analysis of 36 double-blind studies including 16 583 patients. Main outcome measures are incidence of deep vein thrombosis (efficacy) and wound haematoma (safety). Results In general surgery there is no increased efficacy in favour of LMWH (odds ratio (OR) 0.88, 95 per cent confidence interval (c.i.) 0.60-1.30) but there exists a higher incidence of bleeding complications (OR 1.47, 95 per cent c.i. 1.07-2.01). Low-dose LMWH is equally efficacious (OR 1.03, 95 per cent c.i. 0.85-1.26) but safer than unfractionated heparin (OR 0.68, 95 per cent c.i. 0.56-0.82). In orthopaedic surgery there is a trend towards an increased efficacy for LMWH (OR 0.83, 95 per cent c.i. 0.68-1.02) with equivalent safety (OR 0.96, 95 per cent c.i. 0.68-1.36). Conclusion A superiority of LMWH is suggested but heterogeneity might make generalizability to future patients questionable. A meta-analysis on individual patient data should be the next step before randomizing additional patients in future trials.