A New Step Toward Evidence of In Vivo Perineural Dexamethasone Safety: An Animal Study.

Background and Objectives: The aim of this study was to analyze histological nerve toxicity of perineural dexamethasone administration in combination with ropivacaine on mice. Efficacy of perineural dexamethasone in combination with regional anesthesia is clearly demonstrated. However, the safety of this procedure is still a matter of debate. Methods: A sciatic nerve block was performed on 90 mice. Five groups, each containing 18 mice assigned randomly, were used in these experiments: the sham group (isotonic saline solution), R group (perineural ropivacaine), D group (perineural dexamethasone), RDPN group (perineural ropivacaine and perineural dexamethasone), and the RDS group (perineural ropivacaine and systemic dexamethasone). Sensory and motor blocks were evaluated every 30 minutes for 14 hours. Fourteen and 28 days after this procedure, 9 mice in each group were killed for sciatic nerve histological assessment. Results: No statistical difference was observed between different groups for Wallerian degeneration (P = 0.28 at day 14 and P = 0.22 at day 28) and perineural inflammation (P = 0.9 at day 14). Motor and sensory block durations were tested for each group. A statistical difference was observed for motor block duration between the RDPN group (150 minutes [127-172 minutes]), the RDS group (120 minutes [90-120 minutes]), and the R group (60 minutes [60-90 minutes]). Sensory block duration was also statistically different: 660 minutes (660-720 minutes) in the RDPN group, 480 minutes (427-660 minutes) in RDS group, 330 minutes (240-410) in the R group. Conclusions: A combination of ropivacaine and perineural dexamethasone allows longer sensory block duration compared with ropivacaine alone or ropivacaine and systemic dexamethasone, without increased neural toxicity. Copyright (C) 2017 by American Society of Regional Anesthesia and Pain Medicine.

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