Functional Testing for Tranexamic Acid Duration of Action Using Modified Viscoelastometry.

Area of Science:

• Hemostasis and Thrombosis
• Pharmacology
• Critical Care Medicine

Background:

• Tranexamic acid (TXA) is a standard antifibrinolytic agent used to prevent or treat hyperfibrinolysis.
• Prolonged inhibition of fibrinolysis, termed
• fibrinolytic shutdown,
• is associated with increased mortality.
• A novel viscoelastometric assay allows for bedside measurement of TXA' ,
• s antifibrinolytic effect using tissue plasminogen activator (TPA).

Purpose of the Study:

• To evaluate the feasibility of a new viscoelastometric TPA test for quantifying TXA' ,
• s antifibrinolytic activity at the bedside.
• To assess the duration and variability of TXA-induced lysis inhibition in cardiac surgery patients.
• To investigate the correlation between TXA plasma concentrations, antifibrinolytic activity, and patient factors like renal function.

Main Methods:

• A prospective observational study involving 25 cardiac surgery patients.
• In vivo measurement of lysis time (LT) and maximum lysis (ML) using the viscoelastometric TPA test for up to 96 hours post-TXA administration.
• Measurement of plasma TXA and plasminogen activator inhibitor 1 (PAI-1) concentrations, alongside in vitro dose-response curves in healthy volunteers.

Main Results:

• TXA plasma concentration significantly correlated with LT and ML (r = 0.55–0.62, p < 0.0001).
• Fibrinolysis remained inhibited up to 96 hours, with significant inter-individual variability observed after 24 hours (p = 0.0013).
• Impaired renal function was associated with higher TXA concentrations (p < 0.0001) and more pronounced lysis inhibition.

Conclusions:

• The TPA test is a feasible method for determining antifibrinolytic activity at the bedside.
• Individual fibrinolytic capacity can be measured, particularly relevant in critically ill patients.
• TXA-induced lysis inhibition is variable and influenced by factors such as renal function.