Comparison of neurotoxicity of dexmedetomidine as an adjuvant in brachial plexus block in rats of different age

Dexmedetomidine is a local anesthetic adjuvant that exerts neuroprotective effects in addition to its sedative and analgesic properties. However, it is not clear whether dexmedetomidine causes any neurotoxicity in neonates. We injected dexmedetomidine alone or in combination with ropivacaine to induce brachial plexus block in rats of different age, corresponding to human neonate, childhood, adolescence and adulthood. We then examined pro-inflammatory cytokines and activated caspase 3 to determine the neurotoxicity effects. We found that high dose of dexmedetomidine significantly reduced IL-6 and TNF-α levels in all aged rat brachial plexus compared to saline treatment, and these levels are similar to that of control brachial plexus at postnatal day 14, 18 and adulthood. Caspase 3 level is not significantly different between dexmedetomidine and control group, except that it is higher in dexmedetomidine treated group at postnatal day 5. We found that this neurotoxicity effect of dexmedetomidine is only present at a high dose. Dexmedetomidine shows minimal neurotoxicity in neonate rats during brachial plexus block when moderate doses are administered. This observation warrants more detailed clinical studies to determine the safety of using dexmedetomidine for brachial plexus block in infant or early childhood patients.