title: The effect of pre-operative aspirin on bleeding, transfusion, myocardial infarction, and mortality in coronary artery bypass surgery: a systematic review of randomized and observational studies.
abstract: OBJECTIVE
  To obtain estimates of the efficacy and safety of pre-operative aspirin in patients undergoing coronary artery bypass grafting (CABG).
  
  
  RESULTS
  Eligible studies included randomized controlled trials (RCTs) and observational studies of patients undergoing CABG, comparing pre-operative aspirin with no aspirin/placebo, and reporting at least one of our primary outcomes. In eight RCTs (n = 805), pre-operative aspirin increased post-operative bleeding [Mean difference (MD), 104.9 mL; 95% confidence interval (CI), 19.2-190.6; P = 0.016] and reoperation [odds ratio (OR), 2.52; 95% CI, 1.18-5.38; P = 0.017), but not transfusion requirements (MD, 0.62 units; 95% CI, -0.06-1.30; P = 0.072). Subgroup analysis suggested that bleeding was increased with aspirin doses > or =325 mg/day, but not with lower doses. In 14 observational studies (n = 4485), pre-operative aspirin increased post-operative bleeding (MD, 113.6 mL; 95% CI, 45.2-182.0; P = 0.001) and transfusion requirements (MD, 0.34; 95% CI, 0.12-0.56 units; P = 0.002), but not reoperation (OR, 1.12; 95% CI, 0.69-1.83; P = 0.647). Neither analysis detected a significant effect on myocardial infarction or death.
  
  
  CONCLUSIONS
  Pre-operative aspirin increases post-operative bleeding, but this may be avoided by the use of aspirin doses <325 mg/day. Most of the RCTs are old and the meta-analysis was underpowered for efficacy outcomes. A large randomized trial is necessary to determine the safety and efficacy of pre-operative aspirin in the setting of contemporary cardiac surgical practice.
authors.affiliation: Division of Cardiac Surgery, Hamilton General Hospital, McMaster University, 237 Barton St. E., Hamilton, Ontario, Canada L8L 2X2. sunjc2@mcmaster.ca
authors.forename: Jack C J
authors.initials: JC
authors.lastname: Sun
authors.forename: Richard
authors.initials: R
authors.lastname: Whitlock
authors.forename: Ji
authors.initials: J
authors.lastname: Cheng
authors.forename: John W
authors.initials: JW
authors.lastname: Eikelboom
authors.forename: Lehana
authors.initials: L
authors.lastname: Thabane
authors.forename: Mark A
authors.initials: MA
authors.lastname: Crowther
authors.forename: Kevin H T
authors.initials: KH
authors.lastname: Teoh
mesh_terms: D000368:Aged; D001241:Aspirin / Q000009:adverse effects*; D016063:Blood Loss, Surgical / Q000401:mortality / Q000517:prevention & control; D001026:Coronary Artery Bypass / Q000401:mortality; D003328:Coronary Thrombosis / Q000401:mortality / Q000517:prevention & control*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality / Q000517:prevention & control*; D010975:Platelet Aggregation Inhibitors / Q000009:adverse effects*; D019106:Postoperative Hemorrhage / Q000139:chemically induced*; D011292:Premedication; D016032:Randomized Controlled Trials as Topic
chemical_list: D010975:Platelet Aggregation Inhibitors; D001241:Aspirin