The absorption of aspirin is reduced after coronary artery bypass grafting.

BACKGROUND

Despite treatment with the antiplatelet drug aspirin, some patients who undergo coronary artery bypass grafting (CABG) experience a thromboembolic event in the early postoperative period. The etiology of a reduced aspirin effect after CABG is still unsolved. Hence, we investigated whether patients who undergo CABG have a reduced absorption of aspirin after surgery, measured as levels of plasma salicylic acid (SA).

METHODS

In total, 53 patients were included between October 2015 and May 2018. Blood samples where obtained at the day before surgery, and at the first (day 1) and second (day 2) postoperative day. A subgroup of 10 patients had additional blood samples obtained on day 1. Plasma SA was measured using liquid chromatography-electrospray-ionization tandem-mass spectrometry. Multiplate Analyzer (Roche, Roche Diagnostics, Mannheim, Germany) and VerifyNow Aspirin Test (Accumetrics, San Diego, Calif) were used to assess platelet aggregation as a measurement of the antiplatelet effect of aspirin.

RESULTS

A comparison of the difference in change of SA concentration between the day before surgery with day 1 and day 2 showed a significantly reduced increase in SA plasma levels after intake of aspirin at day 1 and day 2 after surgery (P < .0001), including a significantly reduced SA increase in the subgroup at 2, 3, and 4 hours after intake of aspirin. Corresponding with a reduced effect of aspirin, neither Multiplate Analyzer arachidonic acid, nor VerifyNow Aspirin Test showed a significant reduction in platelet aggregation 1 hour after intake of aspirin at day 1 (P < .0001). This also accounted for the subgroup 2, 3, and 4 hours after aspirin intake on day 1. At day 2 the same pattern as preoperatively was detected.

CONCLUSIONS

After CABG, the SA level and the effect of aspirin were reduced in the immediate postoperative period.