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-affiliate teaching hospital. Participants: Patients undergoing elective coronary artery bypass graft sur gery (n = 100). Interventions: The patients were divided into 3 groups based on the number of days since they last ingested aspirin: less than or equal to2 days, 3 to 7 days, and >7 days. Preoperative platelet function was assessed in all pa tients using platelet aggregation responses to arachidonic acid, 5 mug/mL, and Platelet Function Analyser (PFA100) collagen/epinephrine closure times. Measurements and Main Results: Patients who ceased aspirin less than or equ al to2 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, patient s who ceased aspirin <less than or equal to>2 days preoperatively had longe r 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 preoperativ ely (128 +/- 42 sec, p < 0.01). The percentage of abnormal responses was al so greatest in the aspirin <less than or equal to>2 days group. Conclusion: Cardiac surgical patients who ingest aspirin less than or equal to2 days preoperatively have greater impairment of platelet function than patients who have a longer preoperative aspirin-free interval. Copyright (C ) 2001 by W.B. Saunders Company.