Over-expression of cyclooxygenase-2 in increased reticulated platelets leads to aspirin resistance after elective off-pump coronary artery bypass surgery

The arachidonic acid-induced platelet aggregation (PLAA) decreased to < 20% within 8 h after taking 100 mg aspirin in healthy volunteers. However, in the OPCAB patients, PLAA levels remained over 20% in 16 (53.3%) patients after resuming aspirin for 24 h. The surgical bleeding volumes were higher in the AR patients compared to the normal responders (512.5 ± 192.8 vs. 314.3 ± 94.9, p = 0.002). The platelet count on Day 8, RP proportions on Days 1, 4, 8, and COX-2 level on Day 4 were significantly increased compared to their baseline levels in AR group but not in AS group. Platelet count on Day 8, RP proportion and COX-2 on Day 4 were all significantly higher in AR group than those in AS group. The surgical bleeding volume and COX-2 over-expression were predictors of post-OPCAB AR. As a conclusion, the inability of aspirin to inhibit the COX-2 created by increased RP would account for the post-OPCAB AR.