Noninvasive vagus nerve stimulation to reduce ileus after major colorectal surgery: early development study

Gastrointestinal Electrical Stimulation as Prevention of Postoperative Ileus-A Blinded Randomized Controlled Porcine Trial

INTRODUCTION

Postoperative ileus (POI) is a condition characterized by a transient cessation of gastrointestinal function caused by surgical trauma and represents a clinical challenge after major abdominal surgery. Despite abdominal surgery being performed frequently and that a diverse range of treatment options for POI has been investigated, no single intervention has proven effective.

AIM

This randomized controlled animal study aimed to investigate the effect of postoperative electrical sigmoid colonic stimulation as a treatment of POI and to explore gastrointestinal motility in POI using a wireless motility capsule.

METHOD

Sixteen pigs were used as study material. All animals underwent a previously developed surgical POI model procedure. A wireless motility capsule (SmartPill, Given Imaging) was inserted in the jejunum or colon. Two pace wires were attached to the sigmoid colon and connected to a pacemaker (Enterra; Medtronic). Animals were randomized to having the pacemaker turned on (experimental group) or turned off (control group). Postoperative gastrointestinal function was observed daily. Intestinal motility was monitored using the SmartPill system. Animals were terminated after regaining normal gastrointestinal function.

RESULTS

All animals in the intervention group passed stool on the first postoperative day, whereas the control group passed stool between the second and the fourth postoperative day (p = 0.001). The number of days till food intake was 1 (range 1-2) in the intervention group and 2 (range 1-3) in the control group (p = 0.02).

CONCLUSION

This study demonstrated improved gastrointestinal recovery time from electrical stimulation as measured by time to first stool and time to first food intake. These novel findings warrant further clinical studies within this field.

Reduction of postoperative ileus in gastrointestinal surgery: systematic review and meta-analysis

BACKGROUND

Postoperative ileus is a surgical complication that affects intestinal motility. There are measures to reduce this problem, but not all have conclusive evidence. This study aimed to determine which measures, such as coffee, chewing gum (CG), electroacupuncture (EA), daikenchuto (DKT), and prokinetic agents, are most effective in reducing postoperative ileus in patients undergoing gastrointestinal surgeries.

METHODS

A systematic search was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines on Google Scholar, PubMed, ScienceDirect, and Web of Science. The following measures were studied to define postoperative ileus: time to passage of the first flatus and time to passage of the first stool. The mean differences were determined by subgroup analyses.

RESULTS

Of 176 studies, 37 were selected for the systematic review, which involved 4647 patients. The reduction in time to passage of the first flatus was -18.33 h (95% CI, -26.46 to -10.20; P <.01) for EA, -5.83 h (95% CI, -9.40 to -2.26; P <.01) for DKT, -14.87 h (95% CI, -26.84 to -2.90; P =.01) for CG, and -1.90 h (95% CI, -8.28 to 4.48; P =.56) for coffee. The reduction in time to passage of the first stool was -32.27 h (95% CI, -39.28 to -25.26; P <.01) for prokinetic agents, -23.05 h (95% CI, -29.31 to -16.78; P <.01) for CG, -12.89 h (95% CI, -17.78 to -8.01; P <.01) for coffee, -19.76 h (95% CI, -32.79 to -6.72; P <.01) for EA, and -0.70 h (95% CI, -25.51 to 26.92; P =.96) for DKT.

CONCLUSION

The use of CG, EA, and prokinetic agents decreased the time to passage of the first flatus and time to passage of the first stool and indirectly reduced postoperative ileus.

Mechanism and Applications of Vagus Nerve Stimulation

Over the past three decades, vagus nerve stimulation (VNS) has emerged as a promising rehabilitation therapy for a diverse range of conditions, demonstrating substantial clinical potential. This review summarizes the in vivo biological mechanisms activated by VNS and their corresponding clinical applications. Furthermore, it outlines the selection of parameters and equipment for VNS implementation. VNS exhibits anti-inflammatory effects, modulates neurotransmitter release, enhances neural plasticity, inhibits apoptosis and autophagy, maintains blood-brain barrier integrity, and promotes angiogenesis. Clinically, VNS has been utilized in the treatment of epilepsy, depression, headache, stroke, and obesity. Its potential applications extend to anti-inflammatory treatment and the management of cardiovascular and cerebrovascular diseases and various brain disorders. However, further experiments are required to definitively establish the efficacy of VNS's various mechanisms. Additionally, there is a need to explore and identify optimal rehabilitation treatment parameters for different diseases.

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.

Alpha 7 nicotinic acetylcholine receptors signaling boosts cell-cell interactions in macrophages effecting anti-inflammatory and organ protection

Activation of the cholinergic anti-inflammatory pathway (CAP) via vagus nerve stimulation has been shown to improve acute kidney injury in rodent models. While alpha 7 nicotinic acetylcholine receptor (α7nAChR) positive macrophages are thought to play a crucial role in this pathway, their in vivo significance has not been fully understood. In this study, we used macrophage-specific α7nAChR-deficient mice to confirm the direct activation of α7nAChRs in macrophages. Our findings indicate that the administration of GTS-21, an α7nAChR-specific agonist, protects injured kidneys in wild-type mice but not in macrophage-specific α7nAChR-deficient mice. To investigate the signal changes or cell reconstructions induced by α7nAChR activation in splenocytes, we conducted single-cell RNA-sequencing of the spleen. Ligand-receptor analysis revealed an increase in macrophage-macrophage interactions. Using macrophage-derived cell lines, we demonstrated that GTS-21 increases cell contact, and that the contact between macrophages receiving α7nAChR signals leads to a reduction in TNF-α. Our results suggest that α7nAChR signaling increases macrophage-macrophage interactions in the spleen and has a protective effect on the kidneys.

Non-invasive Vagus Nerve Stimulation for COVID-19: Results From a Randomized Controlled Trial (SAVIOR I)

Background

Severe coronavirus disease 2019 (COVID-19) is characterized, in part, by an excessive inflammatory response. Evidence from animal and human studies suggests that vagus nerve stimulation can lead to reduced levels of various biomarkers of inflammation. We conducted a prospective randomized controlled study (SAVIOR-I) to assess the feasibility, efficacy, and safety of non-invasive vagus nerve stimulation (nVNS) for the treatment of respiratory symptoms and inflammatory markers among patients who were hospitalized for COVID-19 (ClinicalTrials.gov identifier: NCT04368156).

Methods

Participants were randomly assigned in a 1:1 allocation to receive either the standard of care (SoC) alone or nVNS therapy plus the SoC. The nVNS group received 2 consecutive 2-min doses of nVNS 3 times daily as prophylaxis. Efficacy and safety were evaluated via the incidence of specific clinical events, inflammatory biomarker levels, and the occurrence of adverse events.

Results

Of the 110 participants who were enrolled and randomly assigned, 97 (nVNS, n = 47; SoC, n = 50) had sufficient available data and comprised the evaluable population. C-reactive protein (CRP) levels decreased from baseline to a significantly greater degree in the nVNS group than in the SoC group at day 5 and overall (i.e., all postbaseline data points collected through day 5, combined). Procalcitonin level also showed significantly greater decreases from baseline to day 5 in the nVNS group than in the SoC group. D-dimer levels were decreased from baseline for the nVNS group and increased from baseline for the SoC group at day 5 and overall, although the difference between the treatment groups did not reach statistical significance. No significant treatment differences were seen for clinical respiratory outcomes or any of the other biochemical markers evaluated. No serious nVNS-related adverse events occurred during the study.

Conclusions

nVNS therapy led to significant reductions in levels of inflammatory markers, specifically CRP and procalcitonin. Because nVNS has multiple mechanisms of action that may be relevant to COVID-19, additional research into its potential use earlier in the course of COVID-19 and its potential to mitigate some of the symptoms associated with post-acute sequelae of COVID-19 is warranted.

Transcutaneous vagal nerve simulation to reduce a systemic inflammatory response syndrome and the associated intestinal failure: study protocol of a prospective, two-armed, sham-controlled, double-blinded trial in healthy subjects (the NeuroSIRS-Study)

PURPOSE

Surgery initiates pro-inflammatory mediator cascades leading to a variably pronounced sterile inflammation (SIRS). SIRS is associated with intestinal paralysis and breakdown of intestinal barrier and might result in abdominal sepsis. Technological progress led to the development of a neurostimulator for transcutaneous auricular vagal nerve stimulation (taVNS), which is associated with a decline in inflammatory parameters and peristalsis improvement in rodents and healthy subjects via activation of the cholinergic anti-inflammatory pathway. Therefore, taVNS might be a strategy for SIRS prophylaxis.

METHODS

The NeuroSIRS-Study is a prospective, randomized two-armed, sham-controlled, double-blind clinical trial. The study is registered at DRKS00016892 (09.07.2020). A controlled endotoxemia is used as a SIRS-mimicking model. 2 ng/kg bodyweight lipopolysaccharide (LPS) will be administered after taVNS or sham stimulation. The primary objective is a reduction of clinical symptoms of SIRS after taVNS compared to sham stimulation. Effects of taVNS on release of inflammatory cytokines, intestinal function, and vital parameters will be analyzed.

DISCUSSION

TaVNS is well-tolerated, with little to no side effects. Despite not fully mimicking postoperative inflammation, LPS challenge is the most used experimental tool to imitate SIRS and offers standardization and reproducibility. The restriction to healthy male volunteers exerts a certain bias limiting generalizability to the surgical population. Still, this pilot study aims to give first insights into taVNS as a prophylactic treatment in postoperative inflammation to pave the way for further clinical trials in patients at risk for SIRS. This would have major implications for future therapeutic approaches.

The impact of acetylcholinesterase inhibitors on ileus and gut motility following abdominal surgery: a clinical review

Postoperative ileus is a common complication in the days following colorectal surgery occurring in up to 50% of patients. When prolonged, this complication results in significant morbidity and mortality, doubling the total costs of hospital stay. Postoperative ileus (POI) results from the prolonged inflammatory phase that is mediated in part by the cholinergic anti-inflammatory pathway. Acetylcholinesterase inhibitors, such as neostigmine and pyridostigmine, delay the degradation of acetylcholine at the synaptic cleft. This increase in acetylcholine has been shown to increase gut motility. They have been effective in the treatment of acute colonic pseudo-obstruction, but there is limited evidence for the use of these medications for reducing the incidence of POI. This review was conducted to summarise the evidence of acetylcholinesterase inhibitors' effect on gut motility and discuss their potential use as part of an enhanced recovery protocols to prevent or treat POI.

Post-operative ileus: definitions, mechanisms and controversies

Post-operative ileus (POI) is a syndrome of impaired gastrointestinal transit which occurs following abdominal surgery. There are few effective targeted therapies for ileus, and research has been limited by inconsistent definitions and an incomplete understanding of the underlying pathophysiology. Despite considerable effort, there remains no widely-adopted definition of ileus, and recent work has identified variation in outcome reporting is a major source of heterogeneity in clinical trials. Outcomes should be clearly-defined, clinically-relevant, and reflective of the underlying biology, impacts on hospital resources and quality of life. Further collaborative efforts will be needed to develop consensus definitions and a core outcome set for postoperative gastrointestinal recovery. Investigation into the pathophysiology of POI has been hindered by use of low-resolution techniques and difficulties linking cellular mechanisms to dysmotility patterns and clinical symptoms. Recent evidence has suggested the common assumption of post-operative GI paralysis is incorrect, and that the distal colon becomes hyperactive following surgery. The post-operative inflammatory response is important in the pathophysiology of ileus, but the time course of this in humans remains unclear, with the majority of evidence coming from animal models. Future work should investigate dysmotility patterns underlying ileus, and identify biomarkers which may be used to diagnose, monitor and stratify patients with ileus.

Electrical vagus nerve stimulation as a prophylaxis for SIRS and postoperative ileus

Abdominal surgery results in an activation of immune cells of the bowel wall and a consecutive cytokine and nitric oxide (NO) release leading to an inflammation of the muscularis externa and a bowel paralysis, the so-called postoperative ileus (POI). In addition to the local inflammation, major surgical trauma can also lead to a variable pronounced systemic inflammation up to its maximum variant, the systemic inflammatory response syndrome (SIRS), with hypotension, capillary leak and a breakdown of the intestinal barrier function followed by multi-organ dysfunction (MODS). Until now, neither for SIRS nor for POI, a prophylaxis or an evidence-based treatment exists. Since the pioneering work from Kevin Tracey and his group in the late 90s characterizing the role of the vagus nerve in inflammation and describing the cholinergic anti-inflammatory pathway (CAIP) for the first time, substantial efforts have been made in the research field of neuro-immune interactions. Today, the anti-inflammatory potential of vagus nerve stimulation is moving more and more into focus resulting in new therapeutic approaches. This review focuses on the role of the CAIP in the development of SIRS and POI. Furthermore, new therapeutic options like transcutaneous vagus nerve stimulation are highlighted.