The interaction between preoperative platelet count and function and its relationship with postoperative bleeding in cardiac surgery

Platelet function tests (PFTs) before cardiac surgery are predictive of postoperative bleeding and can guide a correct timing of surgery in patients under P2Y12 inhibitors. Thrombocytopenia affects PFT and may determine postoperative bleeding. The present study aims to investigate the relationship between platelet count and function, and its role in determining postoperative bleeding in cardiac surgery patients pre-treated with P2Y12 inhibitors. The study includes 589 consecutive cardiac surgery patients, tested before surgery with platelet count and multiple electrode aggregometry (MEA) ADPtest (investigating P2Y12 receptor platelet reactivity) and TRAPtest (investigating the thrombin-dependent platelet reactivity). Platelet function was linearly associated (P = 0.001) with platelet count at the ADPtest and the TRAPtest, demonstrating a positive association in the whole spectrum of platelet count. The ADPtest (P = 0.001) and platelet count (P = 0.001) were negatively associated with postoperative bleeding, whereas the TRAPtest was not. At a multivariable analysis, the ADPtest (P = 0.026) and platelet count (P = 0.006) remained independent predictors of postoperative bleeding. The platelet transfusion rate was 5.7% in patients with ADPtest ≥30 U and platelet count ≥150 000 cells/µL, 14.3% in patients with ADPtest ≥30 U and platelet count <150 000 cells/µL, 38.9% in patients with ADPtest <30 U and platelet count ≥150 000 cells/µL, and 50% in patients with ADPtest <30 U and platelet count <150 000 cells/µL (P = 0.001). Platelet function at MEA is dependent on the platelet count not only in the case of thrombocytopenia, but also in the whole range of platelet count; preoperative platelet count and function are determinants of postoperative bleeding, with a larger effect on platelet transfusions attributable to a poor P2Y12-dependent platelet function.