Transcutaneous auricular vagus nerve stimulation to prevent rebound pain after interscalene block for arthroscopic shoulder surgery

BACKGROUND: Rebound pain frequently occurs after resolution of single-shot interscalene brachial plexus block (ISB) and may diminish the overall analgesic benefit of regional anesthesia. Transcutaneous auricular vagus nerve stimulation (taVNS) has demonstrated analgesic and anti-inflammatory properties, but its effect on rebound pain after shoulder arthroscopy remains unclear. METHODS: In this single-center, randomized, participant- and assessor-blinded, sham-controlled trial, 120 adults undergoing elective arthroscopic shoulder surgery with ultrasound-guided single-shot ISB were randomized 1:1 to receive either active taVNS or sham stimulation. Active stimulation was applied perioperatively and continued on postoperative days 1 and 2. The primary outcome was the incidence of rebound pain within 24 hours after surgery. Secondary outcomes included postoperative pain scores, cumulative sufentanil consumption, quality of recovery (QoR-15), sleep quality (Richards-Campbell Sleep Questionnaire), and adverse events. RESULTS: One hundred twenty participants completed the study and were included in the intention-to-treat analysis. Rebound pain occurred in 12 of 60 patients (20.0%) assigned to taVNS compared with 26 of 60 patients (43.3%) assigned to sham stimulation (absolute risk reduction 23.3%, 95% CI 7.2% to 39.5%; number needed to treat 4.3, 95% CI 2.5 to 13.9; relative risk 0.46, 95% CI 0.26 to 0.82; p=0.006). taVNS was associated with lower resting pain scores (mean difference -0.50, 95% CI -0.63 to -0.37; p<0.001) and movement-evoked pain scores (mean difference -0.39, 95% CI -0.65 to -0.14; p=0.003). Patients receiving taVNS demonstrated higher QoR-15 scores on postoperative days 1 and 2 and better sleep quality on the night of surgery and postoperative night 1 (all p<0.01). The between-group difference in cumulative sufentanil consumption was not statistically significant (GMR 0.67, 95% CI 0.44 to 1.01; p=0.056). No stimulation-related adverse events were observed. CONCLUSIONS: Perioperative taVNS may reduce the incidence of rebound pain following single-shot ISB in patients undergoing arthroscopic shoulder surgery. taVNS was also associated with modest reductions in pain scores and improvements in quality of recovery and sleep quality without an increase in adverse events. TRIAL REGISTRATION NUMBER: ChiCTR2500107694.