Aspirin resistance incidence and associations between aspirin effect and outcomes in cardiac surgery

Background When, and on whom, aspirin should be ceased before elective cardiac surgery is controversial. This study assessed the incidence of preoperative aspirin resistance and whether the quantitative antiplatelet effect of aspirin was associated with perioperative outcomes. Methods Aspirin-induced antiplatelet effect was measured by multiple electrode aggregometry in 250 adult cardiac surgical patients within 24 hours before surgery. Aspirin resistance was defined by a normal platelet function testing result for those who had continued taking aspirin until the day before the platelet function testing. Results Aspirin resistance was observed in 16 (11.9%) patients (95% confidence interval [CI], 7.4-18.4). Of the 250 patients included, 75 (30%) required allogeneic blood product transfusion subsequently. Aspirin induced antiplatelet effect (odds ratio [OR], 0.991 per unit increment in the area under the curve on the platelet function testing, with a smaller area indicating more platelet inhibition; 95% CI, 0.982-0.999; P = .035), a higher EuroSCORE [European System for Cardiac Operative Risk Evaluation] II risk (OR, 1.184 per EuroSCORE II risk percentage increment; 95% CI, 1.017-1.379; P = .001), and a lower body mass index (OR, 0.926 per unit increment; 95% CI, 0.867-0.990; P = .024) were the only factors independently associated with requiring perioperative allogeneic blood product transfusion. Conclusions The degree of aspirin effect immediately before cardiac surgery was weakly associated with the risks of postoperative bleeding and allogeneic blood product transfusion, suggesting that measuring aspirin-induced antiplatelet effect before cardiac surgery may be useful as an adjunct in optimizing patient blood management for patients who are at high risk of bleeding and requiring allogeneic blood transfusion