Platelet transfusions reduce fibrinolysis but do not restore platelet function during trauma hemorrhage.

Introduction: Platelets play a critical role in hemostasis with aberrant function implicated in trauma-induced coagulopathy. However, the impact of massive transfusion protocols on platelet function during trauma hemorrhage is unknown. The aim of this study was to characterize the effects of platelet transfusion on platelet aggregation and fibrinolytic markers during hemostatic resuscitation. Methods: Trauma patients enrolled into the prospective Activation of Coagulation and Inflammation in Trauma (ACIT) study between January 2008 and November 2015 who received at least four units of packed red blood cells (PRBCs) were included. Blood was drawn in the emergency department within 2 hours of injury and at intervals after every 4 units of PRBCs transfused. Platelet aggregation was assessed in whole blood with multiple electrode aggregometry. Plasma proteins were quantified by enzyme-linked immunosorbent assay. Results: Of 161 patients who received 4 or more PRBCs as part of their initial resuscitation, 44 received 8-11 units and 28 received 12 units or more. At each time point during bleeding, platelet aggregation was similar in patients who had received a platelet transfusion compared to those who had only received other blood products (p>0.05 for all time points). Platelet transfusion during the 4PRBC intervals was associated with a decrease in maximum lysis on rotational thromboelastometry (start of interval 6% [2-12] vs end of interval 2% [0-5], p=0.001), an increase in plasminogen activator inhibitor-1 (PAI-1; start of interval: 35.9 +/- 14.9 vs end of interval: 66.7 +/- 22.0, p=0.007) and a decrease in tissue plasminogen activator (start of interval: 26.2 +/- 10.5 vs end of interval: 19.0 +/- 5.1, p=0.04). No statistically significant changes in these parameters occurred in intervals which did not contain platelets. Conclusion: Current hemostatic resuscitation strategies do not appear to restore platelet aggregation during active hemorrhage. However, stored platelets may attenuate fibrinolysis by providing an additional source of PAI-1. Further investigation into the effects of early platelet transfusion on platelet function, haemostatic and clinical outcomes during bleeding are warranted. Level of Evidence: Prospective observational study, level III (C) 2017 Lippincott Williams & Wilkins, Inc.

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