Functional testing for tranexamic acid effect duration using modified viscoelastometry

Introduction Tranexamic acid (TXA) is considered gold standard for treatment and prophylaxis of hyperfibrinolysis in trauma patients and cardiac surgery [1,2]. However, prolonged inhibition of lysis (so-called “fibrinolytic shutdown”) correlates with increased mortality in critical ill patients [3]. Additionally, there is still an ongoing discussion about minimal plasma concentrations, effect duration and dose reduction in renal dysfunction [4]. A new viscoelastometric test enables bedside quantification of the antifibrinolytic activity of TXA using tissue plasminogen activator (TPA) and could therefore be useful in dosage and administration of TXA. Methods 25 cardiac surgery patients were included in this prospective observational trial. In-vivo, viscoelastometric TPA-test was used to determine Lysis Time (LT) and Maximum Lysis (ML) over 96h after TXA bolus. Additionally, TXA plasma concentration and plasminogen-activator-inhibitor-1 (PAI-1) were measured. Moreover, dose-effect-curves from blood of healthy volunteers were performed in-vitro. Data presented as median with 25-75th percentiles. Results In-vivo at all timepoints TXA plasma concentration correlated with LT (r=0.55; p Discussion Determination of antifibrinolytic activity using TPA-test is feasible. This is of interest since TXA-induced lysis inhibition varies depending on kidney function. In future, the individual fibrinolytic capacity, e.g. in critically ill patients, can be measured and TXA dosage can be adapted. Our in vitro results supports recent recommendations that TXA plasma concentrations of 10-15µg/ml are sufficient to inhibit fibrinolysis.