Thrombelastographic Whole Blood Coagulation Parameters Demonstrate Improved Clot Strength Induced by Tranexamic Acid during Cardiopulmonary Bypass.

Background: Tranexamic acid reduces the fibrinolytic activity, and may hereby reduce bleeding associated with surgery. However, to date no studies have been published that monitor and display the effect ex vivo. We hypothesized that tranexamic acid improves clot strength and overall coagulation capacity following cardiopulmonary bypass, and the aim of this study was to assess this effect ex vivo using thrombelastography.

Methods: Patients (N=8) undergoing elective coronary artery bypass grafting using cardiopulmonary bypass were randomly assigned to receive either preoperatively 1 gram of tranexamic acid or no tranexamic acid (control group). Blood specimens were collected before and immediately after cardiopulmonary bypass, and whole blood coagulation analysis was performed on a ROTEG® thrombelastograph employing activation with a reaction mixture of tissue factor (Innovin®, final dilution 1:50000 ∼0.15 pM) and single chain recombinant tissue plasminogen activator (4 nM). The coagulation signal was processed to obtain dynamic parameters of clot formation such as maximum velocity (MaxVel), time to maximum velocity (t, MaxVel), minimum velocity (MinVel), and time to minimum velocity (t, MinVel). Overall haemostatic capacity was evaluated using a calculated parameter denoted overall coagulation quality (OCQ) = (maxvel/t, MaxVel)*(t, MinVel - t, MaxVel)).

Results: The integrated mean difference in time (seconds (sec)) to minimal velocity was consistently positive in the tranexamic acid group compared to the control group (1139 sec (95% CI: 463 to 1667) vs −1474 sec (95% CI: −2454 to −588). The overall coagulation quality was compromised in both groups, but less in the tranexamic acid group (−6.98 (95% CI: −25.68 to 11.71) vs −15.31 (95% CI: −37.28 to 6.66)).

Conclusion: Ex-vivo monitoring of the effect of tranexamic acid during cardiopulmonary bypass is feasible, and patients receiving tranexamic acid produce a significantly more lysis resistant clot and a less compromised overall coagulation quality as compared to control patients.