• Raza Alikhan and Alexander T Cohen.
• Arthur Bloom Haemophilia Centre and Haemostasis Laboratory, University Hospital of Wales, Heath Park, Cardiff, UK, CF14 4XW.
• Cochrane Db Syst Rev. 2010 Jan 1(2):CD003747.

BackgroundVenous thromboembolic disease has been extensively studied in surgical patients. The benefit of thromboprophylaxis is now generally accepted, but it is medical patients who make up the greater proportion of the hospital population. Medical patients differ from surgical patients with regard to their health and the pathogenesis of thromboembolism and the impact that preventative measures can have. The extensive experience from thromboprophylaxis studies in surgical patients is therefore not necessarily applicable to non-surgical patients.ObjectivesTo determine the effectiveness and safety of heparin thromboprophylaxis in general medical patients.Search StrategyThe Cochrane Peripheral Vascular Diseases Group searched their Specialised Register (last searched 24 April 2009) and the Cochrane Central Register of Controlled Trials in The Cochrane Library (last searched Issue 2, 2009)We handsearched meeting abstracts, and consulted with colleagues and investigators as well as the manufacturers of the various LMWH preparations to identify unpublished or missed studies.Selection CriteriaRandomised controlled trials comparing unfractionated heparin (UFH) or low molecular weight heparin (LMWH) with placebo or no treatment, or comparing UFH with LMWH.Data Collection And AnalysisOne author identified possible trials, and the other author confirmed eligibility for inclusion in the review. Both authors extracted the data. Disagreements were resolved by discussion. We performed the meta-analysis as a fixed-effect model with relative risks.Main ResultsA significant risk reduction in deep vein thrombosis (DVT) by 60% (relative risk (RR) 0.40; 95% confidence interval CI 0.31 to 0.53; P < 0.00001) and pulmonary embolism (PE) by 42% (RR 0.58; 95% CI 0.43 to 0.80; P = 0.0007) was observed with heparin compared with placebo or no treatment. However, heparin resulted in a significant increase in major haemorrhage (RR 2.18; 95% CI 1.28 to 3.72; P = 0.004) and minor haemorrhage (RR 1.74; 95% CI 1.26 to 2.41; P = 0.0008). There was no statistically significant difference in efficacy between LMWH and UFH. There was a statistically significant 72% risk reduction in major bleeding when LMWH was compared with UFH (RR 0.28; 95% CI 0.10 to 0.78; P = 0.02).Authors' ConclusionsThe data from this review support the use of heparin thromboprophylaixs in medical patients presenting with an acute medical illness. Although the analysis found no significant difference in efficacy between LMWH and UFH, it did note differences in the incidence of DVT and clinical PE with a significantly reduced risk of bleeding in favour of LMWH.

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