Multiple daily doses of acetyl‐salicylic acid (ASA) overcome reduced platelet response to once‐daily ASA after coronary artery bypass graft surgery: a pilot randomized controlled trial

• Published in: Journal of thrombosis and haemostasis 2015-03, Vol.13 (3), p.448-456
• Main Authors: Paikin, J. S., Hirsh, J., Ginsberg, J. S., Weitz, J. I., Chan, N. C., Whitlock, R. P., Pare, G., Johnston, M., Eikelboom, J. W.
• Format: Article
• Language: English
• Subjects: Aged; aspirin; Aspirin - administration & dosage; Aspirin - adverse effects; Biomarkers - blood; Blood Platelets - drug effects; Blood Platelets - metabolism; coronary artery bypass; Coronary Artery Bypass - adverse effects; Drug Administration Schedule; Drug Resistance; Female; Humans; Male; Middle Aged; Ontario; perioperative period; Pilot Projects; Platelet Aggregation - drug effects; Platelet Aggregation Inhibitors - administration & dosage; Platelet Aggregation Inhibitors - adverse effects; Platelet Count; Platelet Function Tests; Thromboxane B2 - blood; Time Factors; Treatment Outcome
• ISSN: 1538-7933; 1538-7836; 1538-7836
• DOI: 10.1111/jth.12832

Summary Background The efficacy of ASA for prevention of graft failure following CABG surgery may be limited by incomplete platelet inhibition due to increased post‐operative platelet turnover. Objectives To determine whether acetyl‐salicylic acid (ASA) 325 mg once‐daily or 81 mg four‐times daily overcomes the impaired response to ASA 81 mg once‐daily in post‐operative coronary artery bypass graft (CABG) patients. Methods We randomized 110 patients undergoing CABG surgery to either ASA 81 mg once‐daily, 81 mg four times daily or 325 mg once‐daily and compared their effects on serum thromboxane B2 (TXB2) suppression and arachidonate‐induced platelet aggregation. Results One hundred patients were included in the final analysis. Platelet counts fell after surgery, reached a nadir on day 2, and then gradually increased. Although there was near complete suppression of TXB2 on the second or third post‐operative day, TXB2 levels increased in parallel with the rise in platelet count on subsequent days. This increase was most marked in patients receiving ASA 81 mg once‐daily and less evident in those receiving ASA four times daily. On post‐operative day 4, (i) median TXB2 levels were lower with four times daily ASA than with either ASA 81 mg once‐daily (1.1 ng/mL; Quartile(Q) Q1,Q3: 0.5, 2.4 and 13.3 ng/mL; Q1,Q3: 7.8, 30.8 ng/mL, respectively; P