A Prospective Audit of Blood Loss and Blood Transfusion in Patients Undergoing Coronary Artery Bypass Grafting After Clopidogrel and Aspirin Therapy

OBJECTIVE: Platelet dysfunction is a common cause of bleeding after coronary artery bypass graft (CAG) surgery. This prospective observational audit explored the effects of clopidogrel and aspirin on chest drain output for the first 24 hours after CAG surgery. METHODS: During a 7 week period from July to Aug 2003, all patients who underwent CAG at the London Chest Hospital were audited. Patients undergoing concomitant valvular surgery were excluded. The study population included patients who had previous cardiac surgery and patients undergoing emergency procedures. Patients were sub-divided into those who were exposed within 7 days of surgery to clopidogrel alone, aspirin alone, both aspirin and clopidogrel and those not exposed to either agent. RESULTS: During the study period, 91 patients were audited. Two patients were excluded due to concomitant valvular surgery. The remaining 89 patients, included those who were exposed within 7 days of surgery to clopidogrel alone (n = 2 ), both aspirin and clopidogrel (n = 12), aspirin alone (n = 65) and those not exposed to either agent (n = 10). The groups were comparable in age, gender, body weight and baseline haematocrit. The clopidogrel and aspirin group had a lower mean chest drain output at 24 hours post CAG compared with both the aspirin alone and non-clopidogrel non-aspirin groups (694.4 mL vs. 831.9 mL vs. 726 mL), although these differences were not statistically significant. Both the clopidogrel-with-aspirin and the aspirin-only groups received blood products more frequently when compared with the non-clopidogrel non-aspirin group and also the mean number of units transfused per patient was greater. Consistent with the highest mean blood loss, the aspirin group was transfused more units of blood than the clopidogrel and aspirin group and non-clopidogrel non aspirin groups (1.67 vs. 1.0 vs. 0.6 units of blood) Again, these differences were not statistically significant. Nevertheless, overall, the frequency and amount of blood transfusion in those patients who were not receiving aspirin or clopidogrel preoperatively was lower than for those receiving clopidogrel and/or aspirin. CONCLUSIONS: Our audit suggested that continuing to administer clopidogrel and/or aspirin in the 7 days prior to CAG surgery is associated with higher postoperative bleeding and morbidity. However, this increased bleeding tendency did not appear to result in a clinically significant increased requirement for allogenic blood product transfusion.