Anticonvulsant action of midazolam, thiopental and propofol on ropivacaine-induced convulsion in rats / 中华麻醉学杂志

ABSTRACT

Objective To assess the anticonvulsant effect of midazolam, thiopental and propofol on the convulsion induced by ropivacaine in rats and the underlying mechanism.Methods Fifty male SD rats, 4-6 months of age, weighing 250-300 g were randomly divided into five groups of 10 animals each (1) control group (C); (2) ropivacaine group; (R) (3) midazolam-ropivacaine group (MR); (4) thiopental-ropivacaine group (SR) and (5) propofol-ropivacaine group (PR) . In control group normal saline 2 ml was infused i.v. . In ropivacaine group (R) 0.75% ropivacaine was infused i.v. at 0.5 ml?min-1 until convulsion occurred. In midazolam - ropivacaine group (MR) midazolam 0.23 mg?kg-1 was injected i.v. 3 min before 0.75% ropivacaine infusion. In SR and PR groups thiopental 2 mg?kg-1 or propofol 1 mg?kg-1 was injected i.v. 1 min before 0.75% ropivacaine infusion. As soon as convulsion occurred ropivacaine infusion was stopped. The animals were decapitated and their brains were removed and kept in liquid nitrogen for determination of the contents of excitatory ammo-acids (aspartic acid and glutamic acid) and the inhibitory amino-acids [glycine and ?-amino butyric acid (GABA)] by high-performance liquid chromatography . The amount of ropivacaine infused in each group was recorded and calculated.Results The dose of ropivacaine needed to produce convulsion was 4.6?0.5 mg?kg-1 in group R and was significantly increased in the 3 groups pretreated with general anesthetics and was 2.96 times the dose in group R in MR group, 2.84 times in SR group and 1.54 times in PR group. The 4 amino-acid concentrations in the brain were significantly higher in group R than in control group. Compared to group R the Asp, Gly and GABA concentrations were significantly lower in group MR and PR but in group SR only Asp concentration was significantly lower. There was no significant difference in glutamic acid concentration among the4 roopivacaine groups (group 2-5).Conclusion Midazolam, thiopental and propofol can all increase the dose of ropivacaine needed to induce convulsion and midazolam and thiopental are more effective than propofol.