title: Systematic review, meta-analysis and meta-regression of the effect of tranexamic acid on surgical blood loss.
abstract: BACKGROUND
  Tranexamic acid (TXA) reduces blood transfusion in surgery but the extent of the reduction in blood loss and how it relates to the dose of TXA is unclear.
  
  
  METHODS
  A systematic review of randomized trials was performed. Data were extracted on blood loss from trials comparing intravenous TXA with no TXA or placebo in surgical patients. A Bayesian linear regression was used to describe the relationship between the reduction in blood loss with TXA and the extent of bleeding as measured by the mean blood loss in the control group. A meta-analysis of the log-transformed data was conducted to quantify the effect of TXA on blood loss, stratified by type of surgery, timing of TXA administration and trial quality. Meta-regression was used to explore the effect of TXA dosage.
  
  
  RESULTS
  Data from 104 trials were examined. Although the absolute reduction in blood loss with TXA increased as surgical bleeding increased, the percentage reduction was similar. TXA reduced blood loss by 34 per cent (pooled ratio 0·66, 95 per cent confidence interval 0·65 to 0·67; P < 0·001). The percentage reduction in blood loss with TXA differed by type of surgery, timing of TXA administration and trial quality, but the differences were small. The effect of TXA on blood loss did not vary over the range of doses assessed (5·5-300 mg/kg).
  
  
  CONCLUSIONS
  TXA reduces blood loss in surgical patients by about one-third. A total dose of 1 g appears to be sufficient for most adults. There is no evidence to support the use of high doses.
authors.affiliation: Clinical Trials Unit, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK. katharine.ker@lshtm.ac.uk
authors.forename: K
authors.initials: K
authors.lastname: Ker
authors.forename: D
authors.initials: D
authors.lastname: Prieto-Merino
authors.forename: I
authors.initials: I
authors.lastname: Roberts
mesh_terms: D000328:Adult; D000933:Antifibrinolytic Agents / Q000008:administration & dosage*; D016063:Blood Loss, Surgical / Q000517:prevention & control*; D004305:Dose-Response Relationship, Drug; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D012044:Regression Analysis; D014148:Tranexamic Acid / Q000008:administration & dosage*
chemical_list: D000933:Antifibrinolytic Agents; D014148:Tranexamic Acid