title: Low molecular weight heparin in prevention of perioperative thrombosis.
abstract: OBJECTIVE
  To determine whether prophylactic treatment with low molecular weight heparin reduces the incidence of thrombosis in patients who have had general or orthopaedic surgery.
  
  
  METHODS
  Meta-analysis of results from 52 randomised, controlled clinical studies (29 in general surgery and 23 in orthopaedic surgery) in which low molecular weight heparin was compared with placebo, dextran, or unfractionated heparin.
  
  
  METHODS
  Patients who had had general or orthopaedic surgery.
  
  
  METHODS
  Once daily injection of a low molecular weight heparin compared with placebo, dextran, or unfractionated heparin.
  
  
  METHODS
  Incidence of deep venous thrombosis, pulmonary embolism, major haemorrhages, and death.
  
  
  RESULTS
  The results confirm that low molecular weight heparins are more efficacious for the prophylactic treatment of deep venous thrombosis than placebo (common odds ratio 0.31, 95% confidence interval 0.22 to 0.43; p < 0.001) and dextran (0.44, 0.30 to 0.65; p < 0.001). The results suggest that low molecular weight heparins are also more efficacious than unfractionated heparin (0.85, 0.74 to 0.97; p = 0.02), with no significant difference in the incidence of major haemorrhages (1.06, 0.93 to 1.20; p = 0.62).
  
  
  CONCLUSIONS
  Low molecular weight heparins seem to have a higher benefit to risk ratio than unfractionated heparin in preventing perioperative thrombosis. However, it remains to be shown in a suitably powered clinical trial whether low molecular weight heparin reduces the risk of fatal pulmonary embolism compared with heparin.
mesh_terms: D016063:Blood Loss, Surgical; D003911:Dextrans / Q000627:therapeutic use; D006493:Heparin / Q000627:therapeutic use; D006495:Heparin, Low-Molecular-Weight / Q000627:therapeutic use*; D006801:Humans; D015994:Incidence; D007431:Intraoperative Complications / Q000453:epidemiology / Q000517:prevention & control*; D009985:Orthopedics; D010919:Placebos; D011655:Pulmonary Embolism / Q000453:epidemiology / Q000517:prevention & control*; D013924:Thrombophlebitis / Q000453:epidemiology / Q000517:prevention & control*
chemical_list: D003911:Dextrans; D006495:Heparin, Low-Molecular-Weight; D010919:Placebos; D006493:Heparin