OBJECTIVES: Transcutaneous auricular vagus nerve stimulation (taVNS) has been proposed as a non-pharmacological intervention for postoperative pain, but its effects remain unclear. We conducted this study to evaluate the efficacy and safety of taVNS for postoperative pain management.
METHODS: A systematic literature search was performed in PubMed, Embase, the Cochrane Library, and Web of Science. Randomized controlled trials comparing perioperative taVNS with sham stimulation implemented using inactive electrical output, electrical insulation, transient stimulation followed by deactivation, or electrode placement at presumed non-vagal auricular sites in adult surgical patients were included. The review protocol was prospectively registered in PROSPERO (CRD420251129040). Outcomes included postoperative pain scores, postoperative opioid consumption, proportion of patients requiring rescue analgesia, incidence of rebound pain, and incidence of postoperative nausea and vomiting (PONV). Standardized mean differences (SMD) or mean differences (MD) with 95% confidence intervals (CI) were calculated for continuous outcomes, and risk ratios (RR) for dichotomous outcomes, using random-effects models.
RESULTS: Seven studies (684 patients) were included in the meta-analysis. The results showed that taVNS significantly reduced postoperative pain scores at early (MD -0.79, 95% CI -1.02 to -0.56), middle (MD -0.77, 95% CI -1.10 to -0.43), and late (MD -0.88, 95% CI -1.06 to -0.70) time points. Postoperative opioid consumption was not significantly different between the taVNS and sham groups (SMD -0.69, 95% CI -1.40 to 0.03). taVNS reduced the need for rescue analgesia and the incidence of rebound pain and was associated with a borderline lower incidence of PONV.
CONCLUSION: Perioperative taVNS may reduce postoperative pain intensity and the incidence of rescue analgesia, rebound pain, and PONV; however, it was not associated with a statistically significant reduction in postoperative opioid consumption. Given the moderate-to-very-low certainty of evidence and the exclusively Chinese origin of the included trials, larger multicentre and multinational RCTs using standardized stimulation and sham protocols are required before routine clinical adoption.
| Discipline Area | Score |
|---|---|
| Physician |  |
Physician rater
The fact that all studies are from one geographic region suggests that there may be other mechanisms, not understood or not explored, at play here.
Physician rater
Lack of TSA to reduce the risk of Type I and II errors inherent in frequentist meta-analysis; small sample size; 2 or 3 studies per outcome; and lack of sensitivity analysis (nerve block, NSAIDs, exclusion of studies at high risk of bias, etc.) The clinical relevance threshold was not met.
Physician rater
The problem with this meta-analysis was the variety of surgical procedures and the fact that some studies included a regional anesthetic technique while others did not. This confounding will influence all of the results and makes conclusions impossible.
, McMaster University