Intrathecal lidocaine neurotoxicity: Combination with bupivacaine and ropivacaine and effect of nerve growth factor

AimsThe study aims to investigate the neurotoxicity induced by combined use of intrathecal lidocaine with bupivacaine and ropivacaine, and to examine the effect of nerve growth factor (NGF) on lidocaine-induced neurotoxicity.Main methodsAll rats received intrathecal infusion of anesthetics and NGF. To study the neurotoxicity of combined use of lidocaine with bupivacaine and ropivacaine, rats received saline, 5% lidocaine, 1.065% bupivacaine, 1.5% ropivacaine, 5% lidocaine + bupivacaine, or 5% lidocaine + 1.5% ropivacaine. To study the neurotoxicity of different proportions of lidocaine and bupivacaine, mixtures were made by mixing 10% lidocaine and 2.5% bupivacaine in ratios of 1:3, 1:2, 1:1, 2:1 and 3:1 by volume. To study the effect of NGF on lidocaine-induced neurotoxicity, rats received saline or 10 μg NGF for 1, 2, 5 and 8 days.Key findingsThe neurotoxicity of lidocaine was significantly increased when combined with ropivacaine. A mixture of lidocaine and bupivacaine in a ratio of ≤ 1:1 did not significantly increase lidocaine-induced neurotoxicity. NGF significantly reduced lidocaine-induced neurobehavioral and morphological damage in the spinal cord. This was accompanied by downregulation of caspase 3 expression.SignificanceRopivacaine is not safe when intrathecally administered with lidocaine at the concentrations used in this study. Bupivacaine may be safely used with lidocaine at a ratio of 1:1. NGF can reduce lidocaine-induced neurotoxicity, possibly via inhibition of caspase 3-mediated apoptosis.