Distinguishing clinical efficacy from vagal target engagement in perioperative transcutaneous auricular vagus nerve stimulation

Abstract

Yuan and colleagues report a randomized, sham-controlled trial in which perioperative transcutaneous auricular vagus nerve stimulation (taVNS) was associated with lower cough pain and reduced postoperative opioid use after thoracoscopic partial lung resection [1]. The clinical signal is of interest, but two details of the stimulation protocol make the physiological interpretation less certain. First, stimulation intensity was individualized by increasing current until the participant reported clear tingling or pricking and then reducing it to a subthreshold level. That procedure is understandable for the preoperative session. The second session, however, was delivered after skin incision during general anesthesia. The report does not explain whether the preoperative setting was reused, whether a fixed current was selected, or whether another rule was applied. The actual delivered current is also not reported for either group. Consensus reporting standards for transcutaneous vagus nerve stimulation recommend reporting both how stimulation dose is selected and the dose actually applied [2]. Without that information, the intraoperative session cannot be reproduced exactly with respect to stimulation intensity, although the stimulation site, frequency, pulse width, duty cycle, timing, and duration are reported. Second, the sham condition