Ketamine could aggravate central nervous toxicity of lidocaine in rats convulsive model

Previous studies demonstrated that systemic administration of lidocaine could induce central nervous toxicities, including behavioral convulsion as well as cognitive and cellular injury. Ketamine, a general anesthetic, is commonly used as an adjuvant in regional anesthesia with combination of lidocaine. The present was designed to investigate the effects of ketamine in central nervous toxicities of lidocaine. Ketamine (1.2 mg/kg, i.v.) was intravenously injected before and/or after administration of lidocaine in rats. After injection of lidocaine, convulsive behaviors of rats were scored according to the modified Racine scale. Cognitive functions and pathology of hippocampus CA3 pyramid neurons of these rats were evaluated on the one, three, five, and seven days after lidocaine induced convulsion. Both pre- and/or post-administration of ketamine (1.2 mg/kg) could significantly improve lidocaine induced convulsive behaviors of rats (P < 0.01). One, three, five, and seven days after lidocaine induced convulsion, cognitive function and pathology of hippocampus CA3 pyramid neurons of these rats were significantly impaired. In addition, cognitive functions and pathology of neurons of the rats that received ketamine (both pre- and/or post-) were further impaired, compared to the rats without ketamine. We conclude that both pre- and/or post-administration of ketamine could improve lidocaine induced convulsive behaviors. However, cognitive functions and pathology of neurons of these rats are further impaired, compared to the rats without ketamine. This result indicates that ketamine combined with lidocaine might be risky in regional anesthesia.