The effects of recent aspirin ingestion on platelet function in cardiac surgical patients

OBJECTIVE: To examine the effects of the preoperative aspirin-free interval on platelet function in cardiac surgical patients. DESIGN: Prospective clinical investigation. SETTING: University-affiliated teaching hospital. PARTICIPANTS: Patients undergoing elective coronary artery bypass graft surgery (n = 100). INTERVENTIONS: The patients were divided into 3 groups based on the number of days since they last ingested aspirin: < or =2 days, 3 to 7 days, and >7 days. Preoperative platelet function was assessed in all patients using platelet aggregation responses to arachidonic acid, 5 microg/mL, and Platelet Function Analyser (PFA100) collagen/epinephrine closure times. MEASUREMENTS AND MAIN RESULTS: Patients who ceased aspirin < or =2 days preoperatively had weaker platelet aggregation responses (18.5% +/- 7% maximum aggregation, mean +/- SD, n = 36) than patients who ceased aspirin 3 to 7 days preoperatively (68.8% +/- 29%, n = 48, p < 0.001) or >7 days preoperatively (68.3% +/- 28%, n = 16, p < 0.001). Similarly, patients who ceased aspirin < or =2 days preoperatively had longer PFA100 closure times (168 +/- 52 sec) than patients who ceased aspirin 3 to 7 days preoperatively (122 +/- 43 sec, p < 0.001) or >7 days preoperatively (128 +/- 42 sec, p < 0.01). The percentage of abnormal responses was also greatest in the aspirin < or =2 days group. CONCLUSION: Cardiac surgical patients who ingest aspirin < or =2 days preoperatively have greater impairment of platelet function than patients who have a longer preoperative aspirin-free interval.