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Thermal Hyperalgesia After Sciatic Nerve Block in Rat Is Transient and Clinically Insignificant

Janda, Allison BA*; Lydic, Ralph PhD; Welch, Kathleen B. MA, MPH; Brummett, Chad M. MD§

Regional Anesthesia & Pain Medicine: March/April 2013 - Volume 38 - Issue 2 - p 151–154
doi: 10.1097/AAP.0b013e3182813aae
Brief Technical Reports

Abstract: Ropivacaine has been associated with transient heat hyperalgesia in sciatic nerve blocks in rat. The goal of the present study was to evaluate the hypothesized presence of transient heat hyperalgesia after perineural injection of ropivacaine with a secondary subanalysis of 2 published studies. Paw withdrawal latency was used to assess the duration of sensory blockade and presence of heat hyperalgesia at 210, 240, 270, and 300 minutes and 24 hours after injection. The analysis revealed hyperalgesia at a single time point (240 minutes after injection; mean difference, −0.60 seconds; P = 0.012) that resolved within 30 minutes, and there was no other significant hyperalgesia at other time points. Although statistically significant, the single time point measurement represented only an 11% change from baseline and was no longer present 30 minutes later. These data support the need for a reevaluation of the interpretation that pain can be worsened by perineural ropivacaine injection.

From the *University of Michigan Medical School; †Department of Anesthesiology, The University of Michigan Health System; ‡Center for Statistical Consultation and Research, University of Michigan; and §Division of Pain Medicine, Department of Anesthesiology, The University of Michigan Health System, Ann Arbor, MI

Accepted for publication November 28, 2012.

Address correspondence to: Chad M. Brummett, MD, Division of Pain Medicine, Department of Anesthesiology, The University of Michigan Health System, 1500 E Medical Center Dr, 1H247 UH, Box 5048, Ann Arbor, MI 48109 (e-mail: cbrummet@umich.edu).

Study was performed at the Department of Anesthesiology, University of Michigan, Ann Arbor, MI.

C.M.B. was supported by grant UL1RR024986 from the National Center for Research Resources (National Institutes of Health, Bethesda, MD). A.J. was supported by the Foundation for Anesthesia Education and Research Fellowship (Rochester, MN). R.L. is supported by National Institutes of Health grants HL-40881 and HL-65272. Additional support was received from the Department of Anesthesiology, University of Michigan, Ann Arbor, MI.

The University of Michigan has filed for a patent covering the use of perineural dexmedetomidine for use in regional anesthesia. C.M.B. is inventor; The Regents of the University of Michigan; Assignee, Anesthetic Methods and Compositions; US patent application US 12/791,506; June 1, 2010.

The content is solely the responsibility of the authors and does not necessarily represent the official views of National Center for Research Resources or the National Institutes of Health.

Joseph M. Neal, MD, served as editor-in-chief for this article.

©2013 American Society of Regional Anesthesia and Pain Medicine