Adenosine diphosphate-induced single-platelet count aggregation and bleeding in clopidogrel-treated patients undergoing coronary artery bypass grafting.

Objectives: To investigate the association between adenosine diphosphate (ADP)-induced platelet aggregation measured by single-platelet count testing and postoperative blood loss in clopidogrel-treated patients with acute coronary syndromes undergoing coronary artery bypass grafting (CABG).

Design: Prospective observational study.

Setting: Clinical study in one cardiac surgery center.

Participants: Eighty-eight patients treated with clopidogrel (300-600 mg loading dose followed by 75 mg daily) within 7 days before CABG.

Interventions: Platelet function was assessed preoperatively by single-platelet count ADP-induced platelet aggregation. Postoperative blood loss and transfusion requirements were recorded.

Measurements And Main Results: There was no significant association between ADP-induced platelet aggregation and blood loss 12 hours postoperatively (estimate -7.51; 95% confidence interval [CI]: -16.9-1.9; p = 0.12). ADP-induced platelet aggregation was associated significantly with the number of platelet concentrates administered within 24 hours after surgery (incidence rate ratio [IRR] 0.95; 95% CI: 0.92-0.98; p<0.01), but not to the number of packed red blood cells (IRR 0.98; 95% CI: 0.95-1.01; p = 0.14).

Conclusions: Preoperative ADP-induced platelet aggregation measured by single-platelet count testing in clopidogrel-treated patients with acute coronary syndromes undergoing CABG was not associated with postoperative blood loss or packed red blood cells transfused, but was associated significantly with number of platelet concentrates administered during the initial 24 postoperative hours.