Neurotoxic effects of different concentrations of tetracaine and ropivacaine on brachial plexus nerve in rats

Abstract

Objective To investigate the neurotoxic effects of different concentrations of tetracaine and ropivacaine on the brachial plexus nerve in rats.Methods Forty-eight male Sprague-Dawley rats,weighing 410-430 g,were randomly divided into 8 groups (n =6 each):normal saline group (group NS),0.25％,0.50％ and 1.00％ tetracaine groups (groups T1-3 ),and 0.25％,0.50％,1.00％ and 2.00％ ropivacaine groups (groups R1-4 ).The rats received injection of normal saline 1.0 ml,0.25％,0.50％ and 1.00％ tetracaine 0.5 ml,0.25％,0.50％,and 1.00％ ropivacaine 1.0 ml and 2.00％ ropivacaine 0.5 ml in groups NS,T1-3 and R1-4 respectively through one side of the axillary sheath.The other side of the axillary sheath served as control side.Five days later,compound action potential and nerve conduction velocity (NCV) of the brachial plexus nerve were measured.Tne brachial plexus nerve was obtained as the specimen for microscopic examination with light and transmission electron microscope.Results Compared with the control side and group NS,the compound action potential and NCV of the brachial plexus nerve were significantly decreased in groups T2,3 and R3,4 ( P ＜ 0.05 ).The compound action potential and NCV of the brachial plexus nerve were gradually decreased with the increasing concentrations of tetracaine in groups T1 3 ( P ＜ 0.05 ).The compound action potential and NCV of the brachial plexus nerve were significantly decreased in group R4 as compared with groups R1-3 (P ＜ 0.05).The microscopic examination showed that the pathologic changes were more severe in groups T2,3 and R3,4 than those on the control side and than in group NS.Conclusion 0.50％ and 1.00％ tetracaine,and 1.00％ and 2.00％ ropivacaine can result in pathologic damage to the brachial plexus nerve in rats and the degree of damage is related to the concentration. Key words: Tetracaine; Amides; Brachial plexus; Drug toxicity