The Use of Thromboelastography to Measure the Influence Inclusion of a Local Anesthetic Agent has on the Mechanical and Kinetic Properties of Fibrin.

Context: Delivery of slow-release local anesthesia has considerable potential for postoperative analgesia. Fibrin gel has shown huge potential for drug delivery, but has not been fully investigated for the delivery of local anesthetics nor has whether incorporation of anesthetic drugs into fibrin alters its mechanical properties.

Aims: This study aimed to evaluate the effects of bupivacaine inclusion on the mechanical and kinetic properties of fibrin as measured by thromboelastography (TEG).

Materials and Methods: Serial dilutions of fibrinogen with thrombin were tested with TEG to identify the optimal concentrations to give reproducible results. Following this, fibrinogen samples diluted with bupivacaine 0.5% in place of normal saline (also 1:20 dilution) were added to thrombin to assess what influence this had on clot strength and kinetics as measured by TEG values (with R , K , and α angle relating to clot kinetics and MA and G (or shear elastic modulus strength) relating to clot strength).

Results: The mean values yielded for R were higher and lower for α angle, suggesting that the inclusion of bupivacaine produced a fibrin clot at a slower rate. The values for MA and G were both lower when bupivacaine was included, suggesting inclusion of the local anaesthetic also resulted in a fibrin clot of inferior strength. These results were not statistically significant.

Conclusion: Although TEG failed to consistently measure these properties, the results suggest that inclusion of local anesthetic affects the clotting process of fibrin, potentially interfering with its ability to function as a sealant, adhesive, or hemostat.