• Scott J Farber, Maryam Saheb-Al-Zamani, Lawrence Zieske, Osvaldo Laurido-Soto, Amit Bery, Daniel Hunter, Philip Johnson, and Susan E Mackinnon.
• Division of Plastic and Reconstructive Surgery, Washington University in St. Louis, 660 S Euclid Ave., 1150 NW Tower Campus Box 8238, St. Louis, MO 63110. mackinnons@wudosis.wustl.ed.
• Anesth. Analg.. 2013 Sep 1;117(3):731-9.

BackgroundA well-known complication of peripheral nerve block is peripheral nerve injury, whether from the needle or toxicity of the medication used. In this study, we sought to determine the extent of damage that results from intrafascicular injection of various commonly used local anesthetics (LAs).MethodsSixteen Lewis rats received an intrafascicular injection of saline (control) or 1 of 3 LAs (bupivacaine, lidocaine, or ropivacaine) into the sciatic nerve (n = 4). At a 2-week end point, the sciatic nerves were harvested for histomorphometric and electron microscopic analysis.ResultsAnimals that received intrafascicular LA injections showed increased severity of injury as compared with control. In particular, there was a significant loss of large-diameter fibers as indicated by decreased counts (P < 0.01 for all LAs) and area (P < 0.01 for all LAs) of remaining fibers in severely injured versus noninjured areas of the nerve. There was a layering of severity of injury with most severely injured areas closest to and noninjured areas furthest from the injection site. Bupivacaine caused more damage to large fibers than the other 2 LAs. In all groups, fascicular transection injury from the needle was observed. Electron microscopy confirmed nerve injury.ConclusionsFrequently used LAs at traditional concentrations are toxic to and can injure the peripheral nerve. Any combination of motor and/or sensory sequelae may result due to the varying fascicular topography of a nerve.

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