Anxiety, vocalization, and agitation following peripheral nerve block withropivacaine

Background and Objectives. Central nervous system (CNS) and cardiovascular toxicity are potential side effects of local anesthetics. However, ropivaca ine has been reported to be less CNS toxic than bupivacaine in human volunt eers. Methods. We describe three cases of peripheral nerve blockade with ro pivacaine that resulted in unusual symptoms of CNS toxicity. Results. In th ree patients, unexpected behavioral changes occurred during administration of ropivacaine. The patients became extremely agitated, anxious, and scream ed, and they did not repsond to Verbal commands. Conclusion: This case repo rt shows that ropivacaine may cause CNS toxicity that differs from classica l signs of local anesthetic-induced toxicity. This effect might be related to the unique structure of ropivacaine, which is formulated in an S-enantom er preparation. It has been shown that S-enantomers bind differently to rec eptors in both the CNS and cardiovascular systems. This property may accoun t for the disinhibition of select neural pathways that are specifically inv olved in mediation of anxiety and aggression.