Intraneural injection during anterior approach for sciatic nerve block.

To the Editor:—We read with interest the case report by Sala-Blanch et al. The authors describe an unorthodox but interesting treatment for patients undergoing continuous sciatic nerve block that raises several concerns. In short, using computed tomographic imaging without clear clinical indication, the authors documented that nerve stimulator–guided needle placement during sciatic nerve block through the anterior approach resulted in an intraneural needle placement. The authors then inserted the catheter and administered local anesthetics. Conventional wisdom suggests that intraneural needle placement and catheter insertion should be avoided because intraneural application of local anesthetics has been shown to result in neurologic injury in animal models. However, despite the documented intraneural needle and catheter placement—although it is not clear whether the stimulating needle lies between fascia and epineurium or between epineurium and perineurium—the patients did not have neurologic injury. Therefore, this case report suggests that not all intraneural injections lead to neurologic injury. It also suggests that nerve stimulators may not be reliable in avoiding intraneural needle or catheter placement. Finally, a better definition of what constitutes an intraneural versus an intraepineural sheath injection during blockade of peripheral nerves and plexuses is needed for more meaningful discussion of this matter. Some experts may view the patient treatment in report by Sala-Blanch et al. unusual or even potentially hazardous. However, their findings should be welcomed because they clearly pose some important questions. At the least, they suggest that future research should continue to focus on developing more reliable and objective tools of nerve localization and injection monitoring techniques to help avoid intraneural injection and reduce the risk of consequent neurologic injury. In any case, it is recommended to withdraw the needle or the catheter if one has any doubt that its position is too close to the nerve, for the safety of regional anesthesia.