European Heart Journal Advance Access originally published online on March 16, 2008
European Heart Journal 2008 29(8):1057-1071; doi:10.1093/eurheartj/ehn104
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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
1 Division of Cardiac Surgery, Hamilton General Hospital, McMaster University, 237 Barton St. E., Hamilton, Ontario, Canada L8L 2X2
2 Department of Mathematics and Statistics, McMaster University, Hamilton, Canada
3 Department of Medicine, McMaster University, Hamilton, Canada
4 Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Canada
Received 1 October 2007; revised 29 December 2007; accepted 14 February 2008; online publish-ahead-of-print 16 March 2008.
* Corresponding author. Tel: +1 905 537 3134, Fax: +1 905 521 1551. Email: sunjc2{at}mcmaster.ca
Aims: To obtain estimates of the efficacy and safety of pre-operative aspirin in patients undergoing coronary artery bypass grafting (CABG).
Methods and 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 
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.
Conclusion: 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.
Key Words: Aspirin • Coronary bypass surgery • Haemorrhage • Myocardial infarction • Mortality