Correspondence  |   June 2019
Ultrasound-guided Popliteal Intraneural Approach: Reply
Author Notes
  • Anesthesia, Intensive Care, and Pain Therapy, Azienda Sanitaria Locale (AUSL), Istituto di Ricerca e Cura a Carattere Scientifico (IRCCS) Reggio Emilia, Reggio Emilia, Italy (G.C.). gianluca.cappelleri@ausl.re.it
  • (Accepted for publication March 6, 2019.)
    (Accepted for publication March 6, 2019.)×
Article Information
Correspondence
Correspondence   |   June 2019
Ultrasound-guided Popliteal Intraneural Approach: Reply
Anesthesiology 6 2019, Vol.130, 1084-1085. doi:10.1097/ALN.0000000000002718
Anesthesiology 6 2019, Vol.130, 1084-1085. doi:10.1097/ALN.0000000000002718
We thank all the authors who commented on our study regarding the intraneural local anesthetic injection.1  Although the general concern regarding this approach is understandable, the conclusions in the received comments apparently do not stem from scientific evidence. Allocating resources to avoid intraneural local anesthetic injection should not be based on common sense but on clear evidence that it could be worse than the extraneural injection.
Jiang et al. suggested that the axonal damage could be attributable to a higher concentration/volume of the local anesthetic deposited around the nerve fascicles after injection within the epineurium. Furthermore, the injection pressure below 15 psi used in our study could be too high for sciatic nerve causing ischemia. Although the hypothesis of nerve fascicle ischemia as the cause of axonal damage is plausible, the possible mechanism described by Jiang et al. is not supported by evidence. A previous animal study demonstrated that nerve fascicle damage ensued only when the intraneural injection pressure was greater than 25 psi.2  Moreover, in our previous study,3  we found that the amplitude reduction seen after injection out of the epineurium was comparable with that observed after intraneural injection. When the sciatic nerve, with an intact epineurium, was exposed to a clinically relevant concentration of lidocaine, the epineurium contained 30% of the “total neural local anesthetic” when the equilibrium was reached.4  Unfortunately, this drop in concentration caused by the epineurium seems to reduce the block effectiveness but not to prevent axonal damage.3