Multiple Electrode Aggregometry After Cardiopulmonary Bypass to Assess Platelet (Dys)-Function and Transfusion Threshold: A Concordance Study

Objective: Cardiac surgery patients have a high risk of postoperative bleeding. Historically, the platelet count has been one of the main parameters used to establish the need for platelet transfusions, and the recent introduction of point-of-care tests for platelet function has allowed clinicians to rationalize platelet transfusion needs by assessing the platelet (dys-)function of the patient. For the present study, the authors evaluated how the introduction of one of these systems—the adenosine diphosphate (ADP) test, performed using a Multiplate electrode analyzer (Roche Diagnostics, Basel, Switzerland)—into their clinical practice had modified their platelet transfusion practice. The relationship between the platelet count and the functional evaluation of platelet aggregation (via the ADP test) also was examined. Design: This was a retrospective, single-center, observational study. Setting: Cardiac surgery department of a tertiary care center in North-east Italy. Participants: Cardiac surgery patients requiring cardiac bypass in 2017 and 2019. Interventions: The primary outcome was to compare platelet transfusion practice before and after the implementation of a platelet function test (the ADP test) into the institution's transfusion algorithm, which replaced the platelet count as the trigger. Secondary outcomes were assessing whether the incorporation of the ADP test into their transfusion algorithm brought about a reduction in the frequency of platelet transfusions compared with previous rates (when only platelets counts were used); assessing patient blood loss in the first 12 postoperative hours; and ascertaining the percentage of patients requiring surgical reexplorations. Measurements and Main Results: The study comprised 110 patients undergoing cardiac surgery from the platelet count period (2017) and 110 patients from the ADP test period (2019). Agreement between platelet counts versus ADP tests in determining the need for platelet transfusion was moderate (κ = 0.483; 95% confidence interval [CI] 0.239-0.728), and the general linear regression relationship between platelet counts and the ADP test (Akaike information criterion = 2536; p < 0.001) was determined. Since the introduction of ADP testing, a highly significant reduction in platelet transfusions has occurred: 41.82% (platelet count period) versus 13.64% (ADP test period) (p < 0.001); average blood loss in the 12 hours postsurgery also was less in the ADP test period (p < 0.001) at 300 mL (95% CI 150-730) compared with 440 mL in the platelet count period (95% CI 135-900). Furthermore, a decreasing trend was observed in the number of patients requiring reexploration to optimize hemostasis in the first 12 hours postsurgery (6.36% v 2.73%); however, this trend did not achieve statistical significance (p = 0.195). Conclusion: The application of new Multiplate analyzer technologies, like the ADP test, have the potential to reduce platelet transfusion rates in cardiac surgery patients compared with the use of platelet counts alone; this point-of-care test may constitute an important strategy to help spare the use of allogeneic blood products. Additional studies are needed to confirm this trend and establish the best cutoff values to apply.