Aims: The 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 methods: All 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 findings: The 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.
Significance: Ropivacaine 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.
Keywords: Bupivacaine; Caspase; Lidocaine; Local anesthetics; Nerve growth factor; Neurotoxicity; Ropivacaine.
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