ESRA19-0492 Neurotoxicity of bupivacaine and liposome bupivacaine after sciatic nerve block in healthy and streptozotocin-induced diabetic mice

<h3>Background and aims</h3> To assess the neurotoxicity of liposome bupivacaine after the sciatic nerve block in streptozotocin (STZ)-induced diabetic mice. <h3>Methods</h3> 18 streptozotocin-induced diabetic and 18 non-diabetic female mice were included in the study. Once peripheral neuropathy was confirmed using tail flick and paw withdrawal tests, peripheral sciatic nerve block was performed. Application of 1.3% liposome bupivacaine, 0.25% bupivacaine hydrochloride (HCl) and 0.9% NaCl was achieved percutaneously, introducing the needle posteromedial to the great trochanter and injecting solutions at the moment the tip of the needle hit the bone. Seven days after the nerve block the sciatic nerves were harvested. Neurotoxicity was assessed using high-resolution light microscopy and morphometric analysis using Ellipse program. <h3>Results</h3> In both diabetic and nondiabetic mice, the G-ratio and axon diameter of 0.25% bupivacaine HCl treated sciatic nerves were significantly increased compared to 0.9% NaCl and 1.3% liposome bupivacaine. the 0.25% bupivacaine HCl treated sciatic nerves showed a decrease in fiber density and an increase in large fiber and axon diameters compared to untreated sciatic nerves in both diabetic and nondiabetic mice. No evidence of acute or chronic inflammation in any of the treatment groups was observed. <h3>Conclusions</h3> Under the conditions of our study, application of bupivacaine HCl, but not liposome bupivacaine or NaCl results in histomorphometric indices of neurotoxicity in diabetic mice. the presence of diabetes did not appear to increase the severity of the histologic findings.