Effect of Transauricular Vagus Nerve Stimulation on Rebound Pain After Ropivacaine Single Injection Femoral Nerve Block for Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

Clinical Efficacy of Auricular Vagus Nerve Stimulation in the Treatment of Chronic and Acute Pain: A Systematic Review and Meta-analysis

INTRODUCTION

Current guidelines for pain treatment recommend a personalized, multimodal and interdisciplinary approach as well as the use of a combination of drug and non-drug therapies. Risk factors for chronification should already be reduced in patients with acute pain, e.g., after surgery or trauma. Auricular vagus nerve stimulation (aVNS) could be an effective non-drug therapy in the multimodal treatment of chronic and acute pain. The aim of this systematic review and meta-analysis is to evaluate the clinical efficacy and safety of aVNS in treating chronic and acute pain conditions.

METHODS

A systematic literature search was performed regarding the application of auricular electrical stimulation in chronic and acute pain. Studies were classified according to their level of evidence (Jadad scale), scientific validity and risk of bias (RoB 2 tool) and analyzed regarding indication, method, stimulation parameters, duration of treatment and efficacy and safety. A meta-analysis on (randomized) controlled trials (using different comparators) was performed for chronic and acute pain conditions, respectively, including subgroup analysis for percutaneous (pVNS-needle electrodes) and transcutaneous (tVNS-surface electrodes) aVNS. The visual analog pain scale (VAS) was defined as primary efficacy endpoint.

RESULTS

A total of n = 1496 patients were treated with aVNS in 23 identified and analyzed studies in chronic pain, 12 studies in acute postoperative pain and 7 studies in experimental acute pain. Of these, seven studies for chronic pain and six studies for acute postoperative pain were included in the meta-analysis. In chronic pain conditions, including back pain, migraine and abdominal pain, a statistically significant reduction in VAS pain intensity for active compared to sham aVNS or control treatment with an effect size Hedges' g/mean difference of - 1.95 (95% confidence interval [CI]: - 3.94 to 0.04, p = 0.008) could be shown and a more favorable effect in pVNS compared to tVNS (- 5.40 [- 8.94; - 1.85] vs. - 1.00 [- 1.55; - 0.44]; p = 0.015). In acute pain conditions, single studies showed significant improvements with aVNS, e.g., in kidney donor surgery or tonsillectomy but, overall, a non-statistically significant reduction in VAS pain intensity for active compared to sham aVNS or control with - 0.70 [- 2.34; 0.93] (p = 0.15) could be observed in the meta-analysis. In acute pain results vary greatly between studies depending especially on co-medication and timepoints of assessment after surgery. A significant reduction in analgesics or opiate intake was documented in most studies evaluating this effect in chronic and acute pain. In 3 of the 12 randomized controlled trials in patients with chronic pain, a sustainable pain reduction over a period of up to 12 months was shown. Overall, aVNS was very well tolerated.

CONCLUSION

This systematic review and meta-analysis indicate that aVNS can be an effective and safe non-drug treatment in patients with specific chronic and acute postoperative pain conditions. Further research is needed to identify the influence of simulation parameters and find optimal and standardized treatment protocols while considering quality-of-life outcome parameters and prolonged follow-up periods. A more standardized approach and harmonization in study designs would improve comparability and robustness of outcomes.

Clinical application of transcutaneous auricular vagus nerve stimulation: a scoping review

PURPOSE

Transcutaneous auricular vagus nerve stimulation (taVNS) is an emerging non-invasive neuromodulation therapy. This study aimed to explore the therapeutic use of taVNS, optimal stimulation parameters, effective sham protocols, and safety.

METHODS

A scoping review was conducted. Five databases and grey literature were searched. The data extracted included stimulation parameters, adverse events (AEs), and therapeutic effects on clinical outcomes.

RESULTS

109 studies were included. taVNS was used across 21 different clinical populations, most commonly in psychiatric, cardiac, and neurological disorders. Overall, 2,214 adults received active taVNS and 1,017 received sham taVNS. Reporting of stimulation parameters was limited and inconsistent. taVNS appeared to have a favourable therapeutic effect across a wide range of clinical populations with varied parameters. Three sham protocols were reported but their effectiveness was documented in only two of the 54 sham-controlled studies. Most reported adverse events were localised to stimulation site.

CONCLUSION

There is growing evidence for taVNS therapeutic effect. taVNS appears safe and tolerable. Sham protocols need evaluation. Standardised and comprehensive reporting of both stimulation parameters and adverse events is required. Two different questionnaires have been proposed to evaluate adverse events and the effectiveness of sham methods in blinding participants.

Effects of esketamine on postoperative rebound pain in patients undergoing unilateral total knee arthroplasty: a single-center, randomized, double-blind, placebo-controlled trial protocol

Introduction

Rebound pain, transient and acute postoperative pain after the disappearance of regional block anesthesia, has been a concern in recent years. Insufficient preemptive analgesia and hyperalgesia induced by regional block are the main mechanisms. At present, the evidence for the treatment of rebound pain is limited. The esketamine, as an antagonist of the N-methyl-D-aspartate receptor, has been proven to prevent hyperalgesia. Therefore, this trial aims to evaluate the impact of esketamine on postoperative rebound pain in patients undergoing total knee arthroplasty.

Methods/design

This study is a single-center, prospective, double-blind, randomized, placebo-controlled trial. Participants who plan to undergo total knee arthroplasty will be randomly assigned to the esketamine group (N = 178) and placebo group (N = 178) in a ratio of 1:1. This trial aims to evaluate the impact of esketamine on postoperative rebound pain in patients undergoing total knee arthroplasty. The primary outcome of this trial is the incidence of rebound pain within 12 h after the operation in the esketamine group and the placebo group. The secondary outcome will be to compare (1) the incidence of rebound pain 24 h after the operation; (2) the time to enter the pain cycle for the first time within 24 h after the procedure; (3) the first time of rebound pain occurred within 24 h after surgery; (4) the modified rebound pain score; (5) NRS score under rest and exercise at different time points; (6) the cumulative opioid consumption at different time points; (7) patient's prognosis and knee joint function evaluation; (8) blood glucose and cortisol concentration; (9) patient's satisfaction score; (10) adverse reactions and adverse events.

Discussion

The effect of ketamine on preventing postoperative rebound pain is contradictory and uncertain. The affinity of esketamine to the N-methyl-D-aspartate receptor is about four times higher than levo-ketamine, the analgesic effect is 3 times higher than levo-ketamine, and there are fewer adverse mental reactions. To our knowledge, there is no randomized controlled trial to verify the impact of esketamine on postoperative rebound pain in patients undergoing total knee arthroplasty. Therefore, this trial is expected to fill an important gap in relevant fields and provide novel evidence for individualized pain management.

Clinical Trial Registration

http://www.chictr.org.cn, identifier ChiCTR2300069044.