Correspondence  |   June 2019
Ultrasound-guided Popliteal Intraneural Approach: Comment
Author Notes
  • Mount Sinai Health System, New York, New York (Y.H.L.). Yan.Lai@mountsinai.org
  • (Accepted for publication March 6, 2019.)
    (Accepted for publication March 6, 2019.)×
Article Information
Correspondence
Correspondence   |   June 2019
Ultrasound-guided Popliteal Intraneural Approach: Comment
Anesthesiology 6 2019, Vol.130, 1083. doi:10.1097/ALN.0000000000002717
Anesthesiology 6 2019, Vol.130, 1083. doi:10.1097/ALN.0000000000002717
Although the study by Cappelleri et al.1  provides us with insights about the reduction of nerve action potentials in human sciatic nerves that persist to at least 6 months after ultrasound-guided intraneural injections, we are concerned by the ethical implications and interpretation of safety of this study in widespread regional anesthesia practice. An unanticipated finding from a previous study, showing that unintentional intraneural injection in a small subgroup (4 of 48 patients) resulted in a faster block onset, allowed Cappelleri et al. to justify providing intentional intraneural injections to subjects receiving sciatic nerve blocks. Unfortunately, the original study was neither powered nor designed to measure long-term consequences on human nerves.2  Similarly, a 2016 trial of 88 patients from the same author shaped the ethical foundation of this current study. However, the 2016 study lacked a sample size calculation on an important secondary outcome (electrophysiologic impairment) and was not powered to detect differences in neurologic recovery at 5 weeks.3  Also, only two thirds of those patients completed assessment at 5 weeks.3  This further weakened the probability of finding a difference in electrophysiologic impairments between the intraneural and extraneural groups. What if there had been significant recovery of amplitude and latency of action potentials in the extraneural group but not the intraneural group by 6 months in the 2016 study? Then, it would be ethically challenging to substantiate the current all-intraneural design. Alarmingly, during follow-up at 5 weeks in that 2016 article, “there was a nonsignificant trend toward patients in the intraneural group to present with more postoperative neurologic symptoms (in 5 of 7 patients).”3