Low-intensity transcutaneous auricular vagus nerve stimulation reduces postoperative ileus after laparoscopic radical resection of colorectal cancer: a randomized controlled trial

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.

Non-invasive vagus nerve stimulation to reduce ileus after colorectal surgery: randomized feasibility trial and efficacy assessment (IDEAL Stage 2B)

AIM

Ileus is characterized by a period of intestinal dysmotility after surgery, leading to vomiting and constipation. In preclinical models, vagus nerve stimulation reduces intestinal inflammation and prevents smooth muscle dysfunction, accelerating the return of gut function. This study explored the feasibility of a definitive trial of non-invasive vagus nerve stimulation (nVNS) along with an early assessment of efficacy.

METHOD

A multicentre, randomized feasibility trial (IDEAL Stage 2B) of self-administered nVNS was performed. Patients undergoing colorectal surgery were randomized to nVNS or sham before and after surgery. Feasibility outcomes comprised assessments of recruitment, compliance, blinding and attrition. Clinical outcomes were measures of intestinal function and adverse events. All participants were followed up for 30 days. Interviews with patients and health professionals explored barriers to feasibility and perspectives around implementation.

RESULTS

In all, 125 patients were approached about the study and 97 (77.6%) took part. Across all randomized groups, the median compliance to treatment was 19 out of 20 stimulations (interquartile range 17-20). The incidence of adverse events was similar across groups. In this unpowered feasibility study, the time taken for the return of gut function (such as first passage of stool) was similar between nVNS and sham treatments. According to interviews, patients were highly motivated to use the device because it provided them with an opportunity to engage actively in their care. Health professionals were highly driven to tackle the problem of ileus.

CONCLUSION

Powered assessments of clinical efficacy are required to confirm or refute the promise of nVNS, as already demonstrated in preclinical models. This feasibility study concludes that a definitive randomized assessment of the clinical benefits of nVNS is desired and feasible.

Postoperative Ileus after Minimally Invasive Colorectal Surgery: A Summary of Current Strategies for Prevention and Management

BACKGROUND

Postoperative ileus (POI) is one of the most common postoperative complications after colorectal surgery and prolongs hospital stays. Minimally invasive surgery (MIS) has reduced POI, but it remains common. This review explores the current methods for preventing and managing POI after MIS.

SUMMARY

Preoperative interventions, including optimising nutrition, preoperative medicationn, and mechanical bowel preparation with oral antibiotics, may have a role in preventing POI. Transversus abdominis plane blocks and lidocaine could replace epidural analgesia in MIS. Fluid overload should be avoided; in some cases, goal-directed fluid therapy may aid in achieving this. Pharmacological agents, such as prucalopride and dexmedetomidine, could target mechanisms underlying POI. New strategies to stimulate vagal nerve activity may promote postoperative gastrointestinal motility. Preoperative bowel stimulation could potentially reduce POI following loop ileostomy closure. However, the evidence base for several interventions remains weak and requires further corroboration with robust studies.

KEY MESSAGES

Despite the increasing use of MIS, POI remains a major issue following colorectal surgery. Further strategies to prevent POI are rapidly emerging. Studies using standardised definitions and perioperative care will help validate these interventions and remove barriers to accurate meta-analysis. Future studies should focus on establishing the impact of these interventions on POI after MIS specifically.

Putative role of non-invasive vagus nerve stimulation in cancer pathology and immunotherapy: Can this be a hidden treasure, especially for the elderly?

Cancer is globally a disease of significant public health concern owing to its prevalence, and association with morbidity and mortality. Thus, cost-effective treatments for cancer are important to help reduce its significant morbidity and mortality. However, the current therapeutic options for cancer such as chemotherapy, radiotherapy, and surgery may produce serious adverse events such as nausea, vomiting, fatigue, and peripheral neuropathy, especially in the long term. In addition, these therapeutic options may not be well tolerated by the elderly especially those who are frail. The current article is aimed at discussing an alternative therapeutic option, non-invasive vagus nerve stimulation (VNS), and the roles it plays in cancer pathology and immunotherapy. The VNS does this by reducing oxidative stress via silent information regulator 1 (SIRT1); inhibiting inflammation via both hypothalamic-pituitary-axis (HPA) and the release of corticosteroid from the adrenal gland, and cholinergic anti-inflammatory pathway (CAP), and increasing vagal activity which helps in the regulation of cell proliferation, differentiation, apoptosis, and metabolism, and increase chance of survival. Furthermore, it helps with reducing complications due to cancer or its treatments such as postoperative ileus and severity of peripheral neuropathy induced by chemotherapy, and improves cancer-related fatigue, lymphopenia, and quality of life. These suggest that the importance of non-invasive VNS in cancer pathology and immunotherapy cannot be overemphasized. Therefore, considering the safety of non-invasive VNS and its cost-effectiveness, it is a therapeutic option worth trying for these patients, especially in combination with other therapies.