Geometric Morphometrics Analysis of the Effect of Liposomal Bupivacaine on Nerve Tissue During Peripheral Nerve Blockades

Peripheral nerve blocks play an important role in achieving analgesia in patients undergoing various surgical procedures. Knowledge of the functional histology of nerves is essential for understanding the mode of action of local anesthetics and the mechanism of nerve damage. Geometric morphometrics is a method which we can used to analyse the morphological changes of examined structures. The main objective of our research was to explore the potential nerve tissue damage after intraneural and perineural application of liposomal bupivacaine using geometric morphometrics methods, by assessing the change in the shape of the axons and nerve fibers. Material and method: The sample in this study consisted of sixty sciatic nerves, randomized into four groups to receive intraneural 4mL of liposomal bupivacaine or physiological solution or perineural 4mL of liposomal bupivacaine or physiological solution. Nerve samples were taken and stained with the Azan method. Using a light microscope connected to a digital camera, pictures were made, after which geometric morphometrics was applied. Five nerve fibers from five parts of the image of the microscopic preparation were used for analysis (center, upper-left, upper-right, lower-left, and lower-right parts of the image), and eight specific points (landmarks) were marked. The file was imported into the MorphoJ program for further analysis of the shape of the two-dimensional models. Results: A statistically significant difference in nerve fiber shape was observed after the perineural application of liposomal bupivacaine and the intraneural application of physiological solution (p = 0.014). A statistically significant difference in axon shape was recorded after the intraneural application of the liposomal bupivacaine and intraneural application of the physiological solution (p = 0.0061). Conclusion: When applied in a clinically controlled environment and in appropriate doses liposomal bupivacaine will not pose significant changes in the shape of nerve fibers or axons.