Gastric dysrhythmias: a potential objective measure of nausea

Who says you are so sick? An investigation on individual susceptibility to cybersickness triggers using EEG, EGG and ECG

In this research paper, we conducted a study to investigate the connection between three objective measures: Electrocardio-gram(EGG), Electrogastrogram (EGG), and Electroencephalogram (EEG), and individuals' susceptibility to cybersickness. Our primary objective was to identify which of these factors plays a central role in causing discomfort when experiencing rotations along three different axes: Roll, Pitch, and Yaw. This study involved 35 participants who were tasked with destroying asteroids using their eye gaze while undergoing passive rotations in four separate sessions. The results, when combined with subjective measurements (specifically, Fast motion sickness questionnaire (FMS) and Simulator sickness questionnaire (SSQ) score), demonstrated that EGG measurements were superior in detecting symptoms associated with nausea. As for ECG measurements, our observations did reveal significant changes in Heart Rate Variability (HRV) parameters. However, we caution against relying solely on ECG as a dependable indicator for assessing the extent of cybersickness. Most notably, EEG signals emerged as a crucial resource for discerning individual differences related to these rotational axes. Our findings were significant not only in the context of periodic activities but also underscored the potential of aperiodic activities in detecting the severity of cybersickness and an individual's susceptibility to rotational triggers.

A review of the auditory-gut-brain axis

Hearing loss places a substantial burden on medical resources across the world and impacts quality of life for those affected. Further, it can occur peripherally and/or centrally. With many possible causes of hearing loss, there is scope for investigating the underlying mechanisms involved. Various signaling pathways connecting gut microbes and the brain (the gut-brain axis) have been identified and well established in a variety of diseases and disorders. However, the role of these pathways in providing links to other parts of the body has not been explored in much depth. Therefore, the aim of this review is to explore potential underlying mechanisms that connect the auditory system to the gut-brain axis. Using select keywords in PubMed, and additional hand-searching in google scholar, relevant studies were identified. In this review we summarize the key players in the auditory-gut-brain axis under four subheadings: anatomical, extracellular, immune and dietary. Firstly, we identify important anatomical structures in the auditory-gut-brain axis, particularly highlighting a direct connection provided by the vagus nerve. Leading on from this we discuss several extracellular signaling pathways which might connect the ear, gut and brain. A link is established between inflammatory responses in the ear and gut microbiome-altering interventions, highlighting a contribution of the immune system. Finally, we discuss the contribution of diet to the auditory-gut-brain axis. Based on the reviewed literature, we propose numerous possible key players connecting the auditory system to the gut-brain axis. In the future, a more thorough investigation of these key players in animal models and human research may provide insight and assist in developing effective interventions for treating hearing loss.

Anaesthesia by intravenous propofol reduces the incidence of intra-operative gastric electrical slow-wave dysrhythmias compared to isoflurane

Gastric motility is coordinated by bioelectrical slow-wave activity, and abnormal electrical dysrhythmias have been associated with nausea and vomiting. Studies have often been conducted under general anaesthesia, while the impact of general anaesthesia on slow-wave activity has not been studied. Clinical studies have shown that propofol anaesthesia reduces postoperative nausea and vomiting (PONV) compared with isoflurane, while the underlying mechanisms remain unclear. In this study, we investigated the effects of two anaesthetic drugs, intravenous (IV) propofol and volatile isoflurane, on slow-wave activity. In vivo experiments were performed in female weaner pigs (n = 24). Zolazepam and tiletamine were used to induce general anaesthesia, which was maintained using either IV propofol (n = 12) or isoflurane (n = 12). High-resolution electrical mapping of slow-wave activity was performed. Slow-wave dysrhythmias occurred less often in the propofol group, both in the duration of the recorded period that was dysrhythmic (propofol 14 ± 26%, isoflurane 43 ± 39%, P = 0.043 (Mann-Whitney U test)), and in a case-by-case basis (propofol 3/12, isoflurane 8/12, P = 0.015 (Chi-squared test)). Slow-wave amplitude was similar, while velocity and frequency were higher in the propofol group than the isoflurane group (P < 0.001 (Student's t-test)). This study presents a potential physiological biomarker linked to recent observations of reduced PONV with IV propofol. The results suggest that propofol is a more suitable anaesthetic for studying slow-wave patterns in vivo.

Effects of acupuncture on gastrointestinal diseases and its underlying mechanism: a literature review of animal studies

Acupuncture is a non-pharmacological traditional Chinese medical technique that has been used for various types of gastrointestinal (GI) diseases in Eastern medicine. However, the specific mechanisms underlying acupuncture treatment in the GI tract have not yet been elucidated. In this study, we searched the electronic databases PUBMED, EMBASE, and MEDLINE and identified 30 eligible studies that were summarized in this review. This review demonstrates that treatments, including both manual and electroacupuncture, have therapeutic mechanisms in diverse GI diseases. The underlying mechanisms are broadly divided into the following: changes in gene expression in the gastric mucosa or nuclei of the solitary tract, metabolic change induction, regulation of anti-inflammatory substances, vagal activity increase, change in functional connectivity between brain regions, and control of the number of neurons related to GI diseases. Although this study is limited in that it does not represent all types of GI diseases with different acupuncture methods, this study identified acupuncture as effective for GI diseases through various biological mechanisms. We hope that our study will reveal various mechanisms of acupuncture in GI diseases and play an important role in the therapy and treatment of GI diseases, thus advancing the field of study.

Gastroparesis: The Complex Interplay with Microbiota and the Role of Exogenous Infections in the Pathogenesis of the Disease

Gastroparesis (GP) is a disorder of gastric functions that is defined by objective delayed gastric emptying in the absence of mechanical obstruction. This disease is characterized by symptoms such as nausea, post-prandial fullness, and early satiety. GP significantly impacts patients' quality of life and contributes to substantial healthcare expenses for families and society. However, the epidemiological burden of GP is difficult to evaluate, mainly due its significant overlap with functional dyspepsia (FD). GP and FD represent two similar diseases. The pathophysiology of both disorders involves abnormal gastric motility, visceral hypersensitivity, and mucosal inflammation. Moreover, both conditions share similar symptoms, such as epigastric pain, bloating, and early satiety. The latest evidence reveals that dysbiosis is directly or indirectly connected to gut-brain axis alterations, which are the basis of pathogenesis in both FD and GP. Furthermore, the role of microbiota in the development of gastroparesis was demonstrated by some clinical studies, which found that the use of probiotics is correlated with improvements in the gastric emptying time (GET). Infections (with viruses, bacteria, and protozoa) represent a proven etiology for GP but have not been sufficiently considered in current clinical practice. Previous viral infections can be found in about 20% of idiopathic GP cases. Moreover, delayed gastric emptying during systemic protozoal infections represents a huge concern for compromised patients, and few data exist on the topic. This comprehensive narrative review analyzes the relationship between microorganisms and GP. We explore, on the one hand, the correlation between gut microbiota dysbiosis and GP pathogenesis, including treatment implications, and, on the other hand, the association between exogenous infections and the etiology of the disease.

Diagnostic Methods for Evaluation of Gastric Motility-A Mini Review

Gastric motility abnormalities are common in patients with disorders of gut-brain interaction, such as functional dyspepsia and gastroparesis. Accurate assessment of the gastric motility in these common disorders can help understand the underlying pathophysiology and guide effective treatment. A variety of clinically applicable diagnostic methods have been developed to objectively evaluate the presence of gastric dysmotility, including tests of gastric accommodation, antroduodenal motility, gastric emptying, and gastric myoelectrical activity. The aim of this mini review is to summarize the advances in clinically available diagnostic methods for evaluation of gastric motility and describe the advantages and disadvantages of each test.

Physiological changes associated with copper sulfate-induced nausea and retching in felines

Nausea is a common disease symptom, yet there is no consensus regarding its physiological markers. In contrast, the process of vomiting is well documented as sequential muscular contractions of the diaphragm and abdominal muscles and esophageal shortening. Nausea, like other self-reported perceptions, is difficult to distinguish in preclinical models, but based on human experience emesis is usually preceded by nausea. Here we focused on measuring gastrointestinal and cardiorespiratory changes prior to emesis to provide additional insights into markers for nausea. Felines were instrumented to chronically record heart rate, respiration, and electromyographic (EMG) activity from the stomach and duodenum before and after intragastric delivery of saline or copper sulfate (CuSO₄, from 83 to 322 mg). CuSO₄ is a prototypical emetic test agent that triggers vomiting primarily by action on GI vagal afferent fibers when administered intragastrically. CuSO₄ infusion elicited a significant increase in heart rate, decrease in respiratory rate, and a disruption of gastric and intestinal EMG activity several minutes prior to emesis. The change in EMG activity was most consistent in the duodenum. Administration of the same volume of saline did not induce these effects. Increasing the dose of CuSO₄ did not alter the physiologic changes induced by the treatment. It is postulated that the intestinal EMG activity was related to the retrograde movement of chyme from the intestine to the stomach demonstrated to occur prior to emesis by other investigators. These findings suggest that monitoring of intestinal EMG activity, perhaps in combination with heart rate, may provide the best indicator of the onset of nausea following treatments and in disease conditions, including GI disease, associated with emesis.

Effects of peristaltic amplitude and frequency on gastric emptying and mixing: a simulation study

The amplitude and frequency of peristaltic contractions are two major parameters for assessing gastric motility. However, it is not fully understood how these parameters affect the important functions of the stomach, such as gastric mixing and emptying. This study aimed to quantify the effects of peristaltic amplitude and frequency on gastric mixing and emptying using computational fluid dynamics simulation of gastric flow with an anatomically realistic model of the stomach. Our results suggest that both the increase and decrease in peristaltic amplitude have a significant impact on mixing strength and emptying rate. For example, when the peristaltic amplitude was 1.2 times higher than normal, the emptying rate was 2.7 times faster, whereas when the amplitude was half, the emptying rate was 4.2 times slower. Moreover, the emptying rate increased more than proportionally with the peristaltic frequency. The nearest contraction wave to the pylorus and the subsequent waves promoted gastric emptying. These results suggest the importance of maintaining parameters within normal ranges to achieve healthy gastric function.

Synergistic augmentation of rhythmic myogenic contractions of human stomach by arginine vasopressin and adrenaline: Implications for the induction of nausea

BACKGROUND AND PURPOSE

Nausea is associated with the hormonal secretion of vasopressin and adrenaline, although their actions in inducing nausea is poorly understood. Here, we have investigated their actions on human stomach muscle.

EXPERIMENTAL APPROACH

Muscle strips were suspended in tissue baths and neuronal-/non-neuronally-mediated contractions were measured. Custom software analysed eight motility parameters defining spontaneous phasic non-neuronally mediated contractions. Receptor distributions were assessed by qPCR and immunofluorescence.

KEY RESULTS

V_1A receptors and α₁ -adrenoceptors were located on muscle as well as interstitial cells of Cajal (ICCs). Myogenic contractions of human proximal and distal stomach (respectively, 2.6 ± 0.1 and 2.7 ± 0.0 per minute; n = 44) were larger in the distal area (1.1 ± 0.1 and 5.0 ± 0.1 mN), developing relatively slowly (proximal) or rapidly (distal). Vasopressin caused tonic (proximal) or short-lived (distal) increases in muscle tone and increased myogenic contraction amplitude, frequency and rate (acting at V_1A receptors; thresholds 10^-11 -10^-10  M); by contrast, cholinergically mediated contractions were unaffected. Oxytocin acted similarly to vasopressin but less potently, at OT receptors). Adrenaline increased (10^-10 -10^-5  M; α₁ -adrenoceptors) and decreased (≥10^-6  M; β-adrenoceptors) muscle tone and enhanced/reduced myogenic contractions. Cholinergically mediated contractions were reduced (α₂ -adrenoceptors). Combined, vasopressin (10^-9  M) and adrenaline (10^-8  M) increased muscle tone and phasic myogenic activity in a synergistic manner.

CONCLUSIONS AND IMPLICATIONS

Vasopressin and adrenaline increased human gastric tone and myogenic contraction amplitude, rate of contraction and frequency. In combination, their actions were further increased in a synergistic manner. Such activity may promote nausea.

Electrogastrogram-Derived Features for Automated Sickness Detection in Driving Simulator

The rapid development of driving simulators for the evaluation of automated driving experience is constrained by the simulator sickness-related nausea. The electrogastrogram (EGG)-based approach may be promising for immediate, objective, and quantitative nausea assessment. Given the relatively high EGG sensitivity to noises associated with the relatively low amplitude and frequency spans, we introduce an automated procedure comprising statistical analysis and machine learning techniques for EGG-based nausea detection in relation to the noise contamination during automated driving simulation. We calculate the root mean square of EGG amplitude, median and dominant frequencies, magnitude of Power Spectral Density (PSD) at dominant frequency, crest factor of PSD, and spectral variation distribution along with newly introduced parameters: sample and spectral entropy, autocorrelation zero-crossing, and parameters derived from the Poincaré diagram of consecutive EGG samples. Results showed outstanding robustness of sample entropy with moderate robustness of autocorrelation zero-crossing, dominant frequency, and its median. Machine learning reached an accuracy of 88.2% and revealed sample entropy as one of the most relevant and robust parameters, while linear analysis highlighted spectral entropy, spectral variation distribution, and crest factor of PSD. This study clearly indicates the need for customized feature selection in noisy environments, as well as a complementary approach comprising machine learning and statistical analysis for efficient nausea detection.

Abnormalities on Electrogastrography in Nausea and Vomiting Syndromes: A Systematic Review, Meta-Analysis, and Comparison to Other Gastric Disorders

BACKGROUND

Functional nausea and vomiting syndromes and gastroparesis, collectively grouped as nausea and vomiting syndromes (NVS), are overlapping conditions with incompletely understood pathophysiology. Gastric slow wave abnormalities are thought to contribute.

AIMS

This study aimed to systematically review and meta-analyze the prevalence of slow wave abnormalities measured by electrogastrography (EGG) in patients with NVS.

METHODS

MEDLINE, EMBASE, EMBASE classic, and CENTRAL databases were systematically searched for articles using EGG in adults (≥ 18 years) with NVS. EGG metrics of interest were percentage time in bradygastria, normogastria, and tachygastria as well as dominant frequency and dominant power. Outcomes were also compared with functional dyspepsia (FD), gastroesophageal reflux disease (GORD), and control cohorts.

RESULTS

Seven hundred and sixty NVS patients and 308 controls were included from 24 studies. Overall, 64% of patients had EGG abnormalities. Average percent time in normogastria was low during fasting (50%; 95% CI 40-63%) and fed (53%; 95% CI 41-68%) states in patients, with substantial periods in fasting bradygastria (34.1%; 95% CI 25-47%) and postprandial tachygastria (21%; 95% CI 17-26%). Across gastric disorders, pooling of 84 studies showed a comparably high prevalence of EGG abnormalities in NVS (24 studies; n = 760) and GORD (13 studies; n = 427), compared to FD (47 studies; n = 1751) and controls (45 studies; n = 1027).

CONCLUSIONS

Frequency-based gastric slow wave abnormalities are prominent in NVS. The strength and consistency of these associations across many studies suggests that gastric dysrhythmia may be an important factor in NVS, motivating the development of more reliable methods for their clinical assessment.

Oxidative stress and motion sickness in one crew during competitive offshore sailing

Competitive Offshore Ocean Sailing is a highly demanding activity in which subjects are exposed to psychophysical stressors for a long time. To better define the physiological adaptations, we investigated the stress response of subjects exposed to 3-days long ocean navigation with disruption of circadian rhythms. 6 male subjects were involved in the study and provided urine and saliva samples before setting sail, during a single day of inshore sailing, during 3-days long ocean navigation, and at the arrival, to measure oxidative stress, cortisol, nitric oxide metabolites (NOx) and metabolic response. Motion Sickness questionnaires were also administered during the navigation. The crew suffered a mean weight loss of 1.58 kg. After the long navigation, a significant increase in ROS production and decrease in total antioxidant capacity and uric acid levels were observed. Lipid peroxidation, NO metabolites, ketones, creatinine, and neopterin levels were also increased. Furthermore, a significant increase in cortisol levels was measured. Finally, we found a correlation between motion sickness questionnaires with the increase of NOx, and no correlation with cortisol levels. Physical and psychological stress response derived from offshore sailing resulted in increased oxidative stress, nitric oxide metabolites, and cortisol levels, unbalanced redox status, transient renal function impairment, and ketosis. A direct correlation between motion sickness symptoms evaluated through questionnaires and NOx levels was also found.

Insights Into Acute and Delayed Cisplatin-Induced Emesis From a Microelectrode Array, Radiotelemetry and Whole-Body Plethysmography Study of Suncus murinus (House Musk Shrew)

Purpose: Cancer patients receiving cisplatin therapy often experience side-effects such as nausea and emesis, but current anti-emetic regimens are suboptimal. Thus, to enable the development of efficacious anti-emetic treatments, the mechanisms of cisplatin-induced emesis must be determined. We therefore investigated these mechanisms in Suncus murinus, an insectivore that is capable of vomiting.

Methods: We used a microelectrode array system to examine the effect of cisplatin on the spatiotemporal properties of slow waves in stomach antrum, duodenum, ileum and colon tissues isolated from S. murinus. In addition, we used a multi-wire radiotelemetry system to record conscious animals’ gastric myoelectric activity, core body temperature, blood pressure (BP) and heart rate viability over 96-h periods. Furthermore, we used whole-body plethysmography to simultaneously monitor animals’ respiratory activity. At the end of in vivo experiments, the stomach antrum was collected and immunohistochemistry was performed to identify c-Kit and cluster of differentiation 45 (CD45)-positive cells.

Results: Our acute in vitro studies revealed that cisplatin (1–10 μM) treatment had acute region-dependent effects on pacemaking activity along the gastrointestinal tract, such that the stomach and colon responded oppositely to the duodenum and ileum. S. murinus treated with cisplatin for 90 min had a significantly lower dominant frequency (DF) in the ileum and a longer waveform period in the ileum and colon. Our 96-h recordings showed that cisplatin inhibited food and water intake and caused weight loss during the early and delayed phases. Moreover, cisplatin decreased the DF, increased the percentage power of bradygastria, and evoked a hypothermic response during the acute and delayed phases. Reductions in BP and respiratory rate were also observed. Finally, we demonstrated that treatment with cisplatin caused inflammation in the antrum of the stomach and reduced the density of the interstitial cells of Cajal (ICC).

Conclusion: These studies indicate that cisplatin treatment of S. murinus disrupted ICC networking and viability and also affected general homeostatic mechanisms of the cardiovascular system and gastrointestinal tract. The effect on the gastrointestinal tract appeared to be region-specific. Further investigations are required to comprehensively understand these mechanistic effects of cisplatin and their relationship to emesis.

The Short-Term Effects and Tolerability of Low-Viscosity Soluble Fibre on Gastroparesis Patients: A Pilot Clinical Intervention Study

Gastroparesis is a motility disorder that causes severe gastric symptoms and delayed gastric emptying, where the majority of sufferers are females (80%), with 29% of sufferers also diagnosed with Type-1 or Type-2 diabetes. Current clinical recommendations involve stringent dietary restriction and includes the avoidance and minimization of dietary fibre. Dietary fibre lowers the glycaemic index of food, reduces inflammation and provides laxation. Lack of dietary fibre in the diet can affect long-term gastrointestinal health. Our previously published rheological study demonstrated that "low-viscosity" soluble fibres could be a potentially tolerable source of fibre for the gastroparetic population. A randomised controlled crossover pilot clinical study was designed to compare Partially-hydrolysed guar gum or PHGG (test fibre 1), gum Arabic (test fibre 2), psyllium husk (positive control) and water (negative control) in mild-to-moderate symptomatic gastroparesis patients (requiring no enteral tube feeding). The principal aim of the study was to determine the short-term physiological effects and tolerability of the test fibres. In n = 10 female participants, post-prandial blood glucose, gastroparesis symptoms, and breath test measurements were recorded. Normalized clinical data revealed that test fibres PHGG and gum Arabic were able to regulate blood glucose comparable to psyllium husk, while causing far fewer symptoms, equivalent to negative control. The test fibres did not greatly delay mouth-to-caecum transit, though more data is needed. The study data looks promising, and a longer-term study investigating these test fibres is being planned.

The gastric conduction system in health and disease: a translational review

Gastric peristalsis is critically dependent on an underlying electrical conduction system. Recent years have witnessed substantial progress in clarifying the operations of this system, including its pacemaking units, its cellular architecture, and slow-wave propagation patterns. Advanced techniques have been developed for assessing its functions at high spatiotemporal resolutions. This review synthesizes and evaluates this progress, with a focus on human and translational physiology. A current conception of the initiation and conduction of slow-wave activity in the human stomach is provided first, followed by a detailed discussion of its organization at the cellular and tissue level. Particular emphasis is then given to how gastric electrical disorders may contribute to disease states. Gastric dysfunction continues to grow in their prevalence and impact, and while gastric dysrhythmia is established as a clear and pervasive feature in several major gastric disorders, its role in explaining pathophysiology and informing therapy is still emerging. New insights from high-resolution gastric mapping are evaluated, together with historical data from electrogastrography, and the physiological relevance of emerging biomarkers from body surface mapping such as retrograde propagating slow waves. Knowledge gaps requiring further physiological research are highlighted.

Preclinical Evaluation of the Effects of Trazpiroben (TAK-906), a Novel, Potent Dopamine D2/D3 Receptor Antagonist for the Management of Gastroparesis

Current therapies for gastroparesis, metoclopramide and domperidone, carry risks of extrapyramidal symptoms and life-threatening cardiac arrhythmias. Trazpiroben, a novel, potent dopamine D₂/D₃ receptor antagonist, has low brain permeation and very low affinity for human ether-à-go-go-related gene (hERG) channel inhibition, potentially improving on safety profiles of existing therapies. Trazpiroben demonstrated the following receptor affinities: high for D₂ and D_3, moderate for D₄ and minimal for D₁ and D₅ It demonstrated moderate affinity for adrenergic alpha 1B (α_1B) and 5-hydroxytryptamine 2A (5HT_2A) receptors and low potential for off-target adverse events (AEs). Trazpiroben potently inhibited dopamine-activated D_2L receptor activation of cognate G-proteins in human embryonic kidney 293 cell membranes and was a neutral D_2L receptor antagonist. In vivo, trazpiroben dose-dependently increased prolactin release in orally dosed rat (0.1-1mg/kg). Additionally, multiple oral doses in the rat (100mg/kg) and dog (50mg/kg) for 3 days produced robust plasma exposures and prolactin increases in both species. Trazpiroben inhibited retching/vomiting in the dog with apomorphine-induced emesis with a potency (0.1-1mg/kg) like that of trazpiroben-mediated prolactin increases in rat. Oral trazpiroben (1, 10, and 30mg/kg) did not affect rat rotarod performance, suggesting low brain penetration. Trazpiroben concentrations were low in cerebrospinal fluid versus plasma following multiple oral doses for 4 days in rat and dog. Trazpiroben weakly inhibited the hERG channel current (concentration causing half-maximal inhibition of control-specific binding of 15.6µM), indicating little potential for disrupting cardiac rhythm. Overall, trazpiroben is a potent D₂/D₃ receptor antagonist designed to avoid serious potential AEs associated with current gastroparesis therapies. Significance Statement Trazpiroben is a novel, potent dopamine D₂/D₃ selective receptor antagonist designed to avoid adverse effects associated with the current pharmacological therapies, metoclopramide and domperidone. Pre-clinical studies have demonstrated low brain penetration and weak affinity for the hERG channel, indicating that trazpiroben is not expected to be associated with central nervous system or cardiovascular safety issues. With these pharmacological properties, trazpiroben may represent a viable new treatment option for gastroparesis due to a potentially improved safety profile relative to existing therapies.

Clinical features and gastric myoelectrical activity in patients with idiopathic and post-surgical rapid gastric emptying who present with unexplained chronic nausea

BACKGROUND

The cause of chronic nausea can be difficult to diagnose. Idiopathic rapid gastric emptying (iRGE) can cause nausea, but limited literature exists on clinical and pathophysiological features. In contrast, dumping syndrome or post-surgical rapid gastric emptying (psRGE) is well-known and may present with early phase vasomotor symptoms, diarrhea, and late phase reactive hypoglycemia. Our aim is to compare clinical and gastric motility characteristics in patients with iRGE and psRGE and unexplained chronic nausea.

METHODS

A retrospective study was conducted on patients with unexplained chronic nausea and RGE (<30% retention of a standard isotope-labeled solid meal at 1-h). Gastric myoelectrical activity (GMA) was recorded during water load satiety tests (WLST) using validated electrogastrogram (EGG) recording methods.

KEY RESULTS

Thirty iRGE and sixteen psRGE patients with unexplained chronic nausea were identified; average 1-hour meal retention was 18.6% and 16.2%, respectively. Nausea, bloating, early satiety, and bowel function were similar in the two groups; fewer iRGE patients had abdominal pain and none had vasomotor symptoms. Normal 3 cpm GMA was recorded in 44% of iRGE vs 29% of psRGE, tachygastria in 13% vs 43%, bradygastria in 25% vs 14%, and mixed in 19% vs 14% (p values >0.05). Abnormal WLST volume (<300 ml) was found in 69% of iRGE and 43% of psRGE (p = 0.36).

CONCLUSIONS & INFERENCES

(a) iRGE and psRGE patients may present with unexplained chronic nausea rather than classic vasomotor symptoms and diarrhea. (b) iRGE and psRGE patients had similar gastric dysrhythmias and accommodation dysfunction, which may contribute to RGE.

Body surface mapping of the stomach: New directions for clinically evaluating gastric electrical activity

BACKGROUND

Gastric motility disorders, which include both functional and organic etiologies, are highly prevalent. However, there remains a critical lack of objective biomarkers to guide efficient diagnostics and personalized therapies. Bioelectrical activity plays a fundamental role in coordinating gastric function and has been investigated as a contributing mechanism to gastric dysmotility and sensory dysfunction for a century. However, conventional electrogastrography (EGG) has not achieved common clinical adoption due to its perceived limited diagnostic capability and inability to impact clinical care. The last decade has seen the emergence of novel high-resolution methods for invasively mapping human gastric electrical activity in health and disease, providing important new insights into gastric physiology. The limitations of EGG have also now become clearer, including the finding that slow-wave frequency alone is not a reliable discriminator of gastric dysrhythmia, shifting focus instead toward altered spatial patterns. Recently, advances in bioinstrumentation, signal processing, and computational modeling have aligned to allow non-invasive body surface mapping of the stomach to detect spatiotemporal gastric dysrhythmias. The clinical relevance of this emerging strategy to improve diagnostics now awaits determination.

PURPOSE

This review evaluates these recent advances in clinical gastric electrophysiology, together with promising emerging data suggesting that novel gastric electrical signatures recorded at the body surface (termed "body surface mapping") may correlate with symptoms. Further technological progress and validation data are now awaited to determine whether these advances will deliver on the promise of clinical gastric electrophysiology diagnostics.

Gastric Electrical Stimulation for Treatment of Refractory Gastroparesis: the Current Approach to Management

Purpose of Review

Gastroparesis is one of the more challenging entities in the landscape of gastroenterology, posing difficulties for both patients and physicians with regard to effective management and therapies. In this article, we reviewed various gastroparesis treatment options, with an emphasis on gastric electrical stimulation (GES).

Recent Findings

GES has demonstrated a significant reduction of cardinal symptoms in refractory gastroparetic patients, particularly nausea and vomiting, across multiple studies. However, GES has not been shown to conclusively decrease gastric emptying time in these patients. Such finding has led the investigators to analyze the impact of combining GES with pyloroplasty. While this treatment pathway is nascent, its results thus far reveal an amplified improvement of gastroparesis symptomatology in addition to significant reduction of gastric transit, compared to GES by itself.

Summary

Limited treatment choices are available for refractory gastroparesis. Combining GES with pyloroplasty holds promise but requires further assessment in large-scale trials to fully evaluate the risks and benefits.

Electrogastrography in Autonomous Vehicles-An Objective Method for Assessment of Motion Sickness in Simulated Driving Environments

Autonomous vehicles are expected to take complete control of the driving process, enabling the former drivers to act as passengers only. This could lead to increased sickness as they can be engaged in tasks other than driving. Adopting different sickness mitigation techniques gives us unique types of motion sickness in autonomous vehicles to be studied. In this paper, we report on a study where we explored the possibilities of assessing motion sickness with electrogastrography (EGG), a non-invasive method used to measure the myoelectric activity of the stomach, and its potential usage in autonomous vehicles (AVs). The study was conducted in a high-fidelity driving simulator with a virtual reality (VR) headset. There separate EGG measurements were performed: before, during and after the driving AV simulation video in VR. During the driving, the participants encountered two driving environments: a straight and less dynamic highway road and a highly dynamic and curvy countryside road. The EGG signal was recorded with a proprietary 3-channel recording device and Ag/AgCl cutaneous electrodes. In addition, participants were asked to signalize whenever they felt uncomfortable and nauseated by pressing a special button. After the drive they completed also the Simulator Sickness Questionnaire (SSQ) and reported on their overall subjective perception of sickness symptoms. The EGG results showed a significant increase of the dominant frequency (DF) and the percentage of the high power spectrum density (FSD) as well as a significant decrease of the power spectrum density Crest factor (CF) during the AV simulation. The vast majority of participants reported nausea during more dynamic conditions, accompanied by an increase in the amplitude and the RMS value of EGG. Reported nausea occurred simultaneously with the increase in EGG amplitude. Based on the results, we conclude that EGG could be used for assessment of motion sickness in autonomous vehicles. DF, CF and FSD can be used as overall sickness indicators, while the relative increase in amplitude of EGG signal and duration of that increase can be used as short-term sickness indicators where the driving environment may affect the driver.

Bioelectrical Signals for the Diagnosis and Therapy of Functional Gastrointestinal Disorders

Coordinated contractions and motility patterns unique to each gastrointestinal organ facilitate the digestive process. These motor activities are coordinated by bioelectrical events, sensory and motor nerves, and hormones. The motility problems in the gastrointestinal tract known as functional gastrointestinal disorders (FGIDs) are generally caused by impaired neuromuscular activity and are highly prevalent. Their diagnosis is challenging as symptoms are often vague and difficult to localize. Therefore, the underlying pathophysiological factors remain unknown. However, there is an increasing level of research and clinical evidence suggesting a link between FGIDs and altered bioelectrical activity. In addition, electroceuticals (bioelectrical therapies to treat diseases) have recently gained significant interest. This paper gives an overview of bioelectrical signatures of gastrointestinal organs with normal and/or impaired motility patterns and bioelectrical therapies that have been developed for treating FGIDs. The existing research evidence suggests that bioelectrical activities could potentially help to identify the diverse etiologies of FGIDs and overcome the drawbacks of the current clinically adapted methods. Moreover, electroceuticals could potentially be effective in the treatment of FGIDs and replace the limited existing conventional therapies which often attempt to treat the symptoms rather than the underlying condition.

Management of Gastrointestinal Symptoms (Nausea, Anorexia and Cachexia, Constipation) in Advanced Illness

Anorexia and cachexia, nausea and vomiting, and constipation are gastrointestinal symptoms that commonly accompany serious illness. Basic science and clinical research continue to improve the understanding of their pathophysiology. Thorough assessment necessitates history, physical examination, and laboratory and diagnostic testing. Pharmacologic management attempts to counteract or reverse the underlying pathophysiologic mechanisms that accompany each symptom, which may benefit from a multimodal approach to achieve adequate control. Future improvements in management require investments in clinical research to determine the efficacy of novel agents along with comparator studies to better understand which treatments should be used in what sequence or combination.

Comparison of clinical findings in 293 dogs with suspect acute pancreatitis: Different clinical presentation with left lobe, right lobe or diffuse involvement of the pancreas

Pancreatitis is a common clinical condition seen in companion animals. The correlation of the region of the pancreas affected to the presentation of clinical signs has not been previously described. A retrospective study on the clinical findings in 293 client-owned dogs diagnosed with suspect pancreatitis based on history, clinical signs, laboratory testing and abdominal ultrasonography was performed. Based on ultrasonography, dogs were divided into three groups: group 1: 41 dogs with ultrasonographic changes consistent with pancreatitis within the left lobe of the pancreas; group 2: 105 dogs with ultrasonographic changes compatible with pancreatitis within the right lobe of the pancreas; and group 3: 147 dogs with ultrasonographic evidence of diffuse pancreatitis. No significant differences regarding age, breed and sex were evident. Furthermore, statistical significance was demonstrated with the presence of pain in group 3; poor appetite in groups 2 and 3; and vomiting and diarrhoea in group 3. Pain is expected to occur with a higher frequency in diffuse pancreatitis, but it is not a common clinical sign. This may represent a more severe form of the disease when the pancreas is diffusely affected. Vomiting was more common than diarrhoea with both clinical signs more prevalent in dogs with diffuse pancreatitis, and this could be ascribed to gastric and intestinal tract involvement. Poor appetite occurred more frequently in dogs with diffuse and right lobe pancreatitis. A possible explanation can be attributed to the fact that the duodenum has many receptors and is referred to as the 'organ of nausea'.

Role of lactic acidosis as a mediator of sprint-mediated nausea

This study aims to determine whether there is a relationship between nausea level and lactic acidosis during recovery from sprinting. In all, 13 recreationally active males completed a 60 s bout of maximal intensity cycling. Prior to and for 45 min following exercise, blood pH, pCO2 , and lactate levels were measured together with nausea. In response to sprinting, nausea, lactate, and H+ concentrations increased and remained elevated for at least 10 min (p < .001), whereas pCO2 increased only transiently (p < .001) before falling below pre-exercise levels (p < .001), with all these variables returning toward pre-exercise levels during recovery. Both measures of nausea adopted for analyses (nausea profile, NP; visual analogue scale, VAS), demonstrated significant repeated measures correlation (rmcorr) post-exercise between nausea and plasma lactate (VAS and NPrrm > 0.595, p < .0001) and H+ concentrations (VAS and NPrrm > 0.689, p < .0001), but an inconsistent relationship with pCO2 (VAS rrm  = 0.250, p = .040; NP rrm  = 0.144, p = .248) and bicarbonate levels (VAS rrm  = -0.252, p = .095; NP rrm  = -0.397, p = .008). Linear mixed modeling was used to predict the trajectory of nausea over time, with both lactate and H+ concentrations found to be key predictors of nausea (p < .0001). In conclusion, this study reveals a strong positive relationship between nausea and both H+ and lactate concentrations during recovery from sprinting, a finding consistent with H+ and lactate being potential mediators of nausea post-sprinting. However, as the timing of the recovery of both H+ and lactate was delayed, compared to that of nausea, further research is required to confirm these findings and investigate other potential mechanisms.

Revisiting the physiology of nausea and vomiting-challenging the paradigm

PURPOSE

The predominant neurotransmitters and receptors for acute and delayed chemotherapy-induced nausea and vomiting (CINV) are represented in the current paradigm, which reflects successful control of emesis. However, control of nausea (N) lags behind management of vomiting (V). This review aims to re-examine and incorporate new information about the mechanisms of V and N.

METHODS

The initial literature search focused on CINV. Keywords in articles led to subsequent discovery of publications focused on N&V in other medical and scientific fields (e.g., gastroenterology, neurology, cannabinoid science, neuropharmacology, and motion sickness). Using keywords to identify other sources continued until no further recent, meaningful publications were found.

RESULTS

More than 86% of references were from recent non-oncology journals and books, suggesting there are many areas for cross-fertilization research into mechanisms and management of N&V-particularly of N, which involves overlapping and dissimilar CNS areas from V. Information from cited articles was incorporated into visual representation of N&V, which is certainly not exhaustive but supports highly complex processes in the stomach and gut, the vagus nerve and spinal cord neurons, the nucleus tractus solitarii, and the anterior insular cortex and anterior cingulate cortex with input from the amygdala.

CONCLUSIONS

These data support the idea that mechanisms for N, whatever the cause, must be highly similar. Continued research into nausea, including patient-reported evaluation and outcomes, is important; interventions for nausea could be considered adjuvants to current standard of care antiemetics and be individualized, depending on patient-reported efficacy and adverse effects and preferences.

Lessons Learned: Gastric Motility Assessment During Driving Simulation

In the era of technological advances and innovations in transportation technologies, application of driving simulators for the investigation and assessment of the driving process provides a safe and suitable testing environment. Although driving simulators are crucial for further improvements in transportation, it is important to resolve one of their main disadvantages–simulator sickness. Therefore, suitable methods for the assessment of simulator sickness are required. The main aim of this paper was to present a non-invasive method for assessing simulator sickness by recording gastric myoelectrical activity–electrogastrography. Open-source hardware for electrogastrography together with recordings obtained in 13 healthy volunteers is presented, and the main aspects of signal processing for artifact cancellation and feature extraction were discussed. Based on the obtained results, it was concluded that slow-wave electrical gastric activity can be recorded during driving simulation by following adequate recommendations and that proposed features could be beneficial in describing non-ordinary electrogastrography signals.

Pathophysiology of idiopathic gastroparesis and implications for therapy

OBJECTIVES

Idiopathic gastroparesis is a gastric motility disorder characterized by chronic upper gastrointestinal symptoms and delayed gastric emptying without an identifiable underlying condition. This review summarizes recent understanding of the pathophysiology and treatment of idiopathic gastroparesis.

MATERIALS AND METHODS

Structured literature search in the PubMed, Embase and ClinicalTrials.gov databases.

RESULTS

Idiopathic gastroparesis involves several alterations in gastric motility and sensation, including delayed gastric emptying, altered myoelectrical activity, impaired fundic accommodation, visceral hypersensitivity and disturbances in antropyloroduodenal motility and coordination. Multiple cellular changes have been identified, including depletion of interstitial cells of Cajal (ICC) and enteric nerves, as well as stromal fibrosis. The underlying cause of these changes is not fully understood but may be an immune imbalance, including loss of anti-inflammatory heme-oxygenase-1 positive (HO-1) macrophages. There is currently no causal therapy for idiopathic gastroparesis. The treatment ladder consists of dietary measures, prokinetic and antiemetic medications, and varying surgical or endoscopic interventions, including promising pyloric therapies. There are ongoing trials with several novel medications, raising hopes for future treatment.

CONCLUSIONS

Patients with idiopathic gastroparesis present several pathophysiological alterations in the stomach, where depletion of ICC is of special importance. Treatment is currently focused on alleviating symptoms through dietary adjustments, medication or surgical or endoscopic interventions.

Chronic nausea and orthostatic intolerance: Diagnostic utility of orthostatic challenge duration, Nausea Profile Questionnaire, and neurohumoral measures

BACKGROUND

Chronic nausea in pediatrics is a debilitating condition with unclear etiology. We aimed to define hemodynamic and neurohumoral characteristics of chronic nausea associated with orthostatic intolerance in order to improve identification and elucidate mechanism.

METHODS

Children (10-18 years) meeting Rome III criteria for functional dyspepsia with nausea and symptoms of orthostatic intolerance (OI) completed a Nausea Profile Questionnaire followed by prolonged (45 minutes rather than the traditional 10 minutes) head-upright tilt (HUT) (70° tilt up) test. Circulating catecholamines, vasopressin, aldosterone, renin, and angiotensins were measured supine and after 15 minutes into HUT. Beat-to-beat heart rate and blood pressure were continuously recorded to calculate their variability and baroreflex sensitivity.

KEY RESULTS

Within 10 and 45 minutes of HUT, 46% and 85% of subjects, respectively, had an abnormal tilt test (orthostatic hypotension, postural orthostatic tachycardia, or syncope). At 15 and 45 minutes of HUT, nausea was elicited in 42% and 65% of subjects respectively. Higher Nausea Profile Questionnaire scores correlated with positive HUT testing at 10 minutes (P = 0.004) and baroreflex sensitivity at 15 minutes (P ≤ 0.01). Plasma vasopressin rose 33-fold in subjects with HUT-induced nausea compared to twofold in those who did not experience HUT-induced nausea (P < 0.01).

CONCLUSIONS AND INFERENCES

In children with chronic nausea and OI, longer duration HUT elicited higher frequency of abnormal tilt testing and orthostatic-induced nausea. The Nausea Profile Questionnaire predicted the orthostatic response to tilt testing. Exaggerated vasopressin release differentiated patients with HUT-induced nausea (vs those without nausea), suggesting a possible mechanism for chronic nausea in childhood.

A History of Drug Discovery for Treatment of Nausea and Vomiting and the Implications for Future Research

The origins of the major classes of current anti-emetics are examined. Serendipity is a recurrent theme in discovery of their anti-emetic properties and repurposing from one indication to another is a continuing trend. Notably, the discoveries have occurred against a background of company mergers and changing anti-emetic requirements. Major drug classes include: (i) Muscarinic receptor antagonists-originated from historical accounts of plant extracts containing atropine and hyoscine with development stimulated by the need to prevent sea-sickness among soldiers during beach landings; (ii) Histamine receptor antagonists-searching for replacements for the anti-malaria drug quinine, in short supply because of wartime shipping blockade, facilitated the discovery of histamine (H1) antagonists (e.g., dimenhydrinate), followed by serendipitous discovery of anti-emetic activity against motion sickness in a patient undergoing treatment for urticaria; (iii) Phenothiazines and dopamine receptor antagonists-investigations of their pharmacology as "sedatives" (e.g., chlorpromazine) implicated dopamine receptors in emesis, leading to development of selective dopamine (D2) receptor antagonists (e.g., domperidone with poor ability to penetrate the blood-brain barrier) as anti-emetics in chemotherapy and surgery; (iv) Metoclopramide and selective 5-hydroxytryptamine3(5-HT3) receptor antagonists-metoclopramide was initially assumed to act only via D2 receptor antagonism but subsequently its gastric motility stimulant effect (proposed to contribute to the anti-emetic action) was shown to be due to 5-hydroxytryptamine4 receptor agonism. Pre-clinical studies showed that anti-emetic efficacy against the newly-introduced, highly emetic, chemotherapeutic agent cisplatin was due to antagonism at 5-HT3 receptors. The latter led to identification of selective 5-HT3 receptor antagonists (e.g., granisetron), a major breakthrough in treatment of chemotherapy-induced emesis; (v) Neurokinin1receptor antagonists-antagonists of the actions of substance P were developed as analgesics but pre-clinical studies identified broad-spectrum anti-emetic effects; clinical studies showed particular efficacy in the delayed phase of chemotherapy-induced emesis. Finally, the repurposing of different drugs for treatment of nausea and vomiting is examined, particularly during palliative care, and also the challenges in identifying novel anti-emetic drugs, particularly for treatment of nausea as compared to vomiting. We consider the lessons from the past for the future and ask why there has not been a major breakthrough in the last 20 years.

Methods for High-Resolution Electrical Mapping in the Gastrointestinal Tract

Over the last two decades, high-resolution (HR) mapping has emerged as a powerful technique to study normal and abnormal bioelectrical events in the gastrointestinal (GI) tract. This technique, adapted from cardiology, involves the use of dense arrays of electrodes to track bioelectrical sequences in fine spatiotemporal detail. HR mapping has now been applied in many significant GI experimental studies informing and clarifying both normal physiology and arrhythmic behaviors in disease states. This review provides a comprehensive and critical analysis of current methodologies for HR electrical mapping in the GI tract, including extracellular measurement principles, electrode design and mapping devices, signal processing and visualization techniques, and translational research strategies. The scope of the review encompasses the broad application of GI HR methods from in vitro tissue studies to in vivo experimental studies, including in humans. Controversies and future directions for GI mapping methodologies are addressed, including emerging opportunities to better inform diagnostics and care in patients with functional gut disorders of diverse etiologies.

Gastric myoelectrical and neurohormonal changes associated with nausea during tilt-induced syncope

BACKGROUND

Nausea is a common prodromal symptom of neurally mediated syncope, but the biological factors linking nausea with syncope have not been studied. We aimed to characterize nausea during tilt-induced syncope by exploring related changes in gastric myoelectrical activity and plasma epinephrine, norepinephrine, and vasopressin concentrations across study phases of recumbency, tilt, syncope, and recovery.

METHODS

Electrogastrographic and plasma hormone changes were compared between patients with tilt-induced syncope and nausea (n = 18) and control subjects (n = 6) without symptoms or hemodynamic changes during tilt-table testing.

KEY RESULTS

Over a 4-minute period preceding syncope, sequential electrogastrography epochs demonstrated an increase over time in bradygastria (P = .003) and tachygastria (P = .014) power ratios, while the dominant frequency (P < .001) and the percent normogastria (P = .004) decreased. Syncope led to significant differences between cases and controls in electrogastrographic power ratios in each frequency range: bradygastria (P = .001), tachygastria (P = .005), and normogastria (P = .03). Nausea always followed electrogastrographic changes, and nausea resolution always preceded electrogastrographic normalization. Plasma vasopressin (676.5 ± 122.8 vs 91.2 ± 15.3 pg/mL, P = .012) and epinephrine (434 ± 91.3 vs 48.7 ± 2.5 pg/mL, P = .03), but not norepinephrine (P > .05), also differed with syncope between cases and controls.

CONCLUSIONS AND INFERENCES

The nausea related to tilt-induced syncope is temporally associated with changes in gastric myoelectrical activity and increases in plasma vasopressin and epinephrine. The biological mechanisms that induce syncope are physiologically distinct from other experimental models of nausea such as illusory self-motion, yet nausea with syncope appears to have similarly associated electrogastrographic and hormone changes. Thus, tilt-induced syncope could serve as an informative experimental model for nausea research.

Ambulatory gastric mucosal slow wave recording for chronic experimental studies

Dysrhythmic bioelectric slow wave activity have been implicated in major functional motility disorders such as gastroparesis and chronic unexplained nausea and vomiting, but its correlation to symptoms is still unclear. For patients with severe gastroparesis, high-frequency gastric stimulation is offered as a therapy in some centers. Temporary gastric electrical stimulation has also been proposed an approach to screen patients who would benefit from the implantation of a permanent stimulator. In this study we introduced novel methods for recording slow wave activity from the gastric mucosa during the entire temporary stimulation phase of 5 days, in 3 patients. An ambulatory recording system was applied to record 3 channels of mucosal slow wave activity, as well as three axis accelerometer data to monitor when the patient was mobile. Techniques were developed to detect large movements and these time periods were excluded from analyses of mucosal slow waves. The frequency and amplitude of the slow waves was calculated in a 5 min segment, with 75% overlap, for the entire duration. In feasibility studies, the slow wave frequency and amplitude for the patients were 3.0±0.96 cpm and 1.43±1.75 mV. Large variations in slow wave amplitude were seen in comparsion to slow wave frequency, which were concordant with previous studies. The use of the ambulatory system will allow for investigation of pathophysiology, correlation of electrophysiology data to patient symptoms and to determine the effects of post-prandial and noctural slow wave patterns. We anticipate that future use of slow wave information alongside patient symptoms may allow improved selection of patients for stimulaton techniques.

Investigational drug therapies for the treatment of gastroparesis

INTRODUCTION

Gastroparesis is defined by nausea, vomiting, pain, early satiety and bloating, and characterized by delayed gastric emptying without obvious structural abnormalities. Metoclopramide is widely used, increasing gastric emptying and inhibiting nausea and vomiting. Other drugs are available in certain countries and some are used 'off-label' because they increase gastric emptying or inhibit emesis. However, correlation between gastroparesis symptoms and rates of gastric emptying is poor. For anti-emetic drugs, dose-ranging and Phase III trials in gastroparesis are lacking. Areas covered: Gastric motility may still be disordered, leading to nausea, even though gastric emptying is unchanged. One hypothesis is that interstitial cells of Cajal (ICC) are damaged by diabetes leading to gastric dysrhythmia and nausea. Novel approaches to treatment of nausea also include the use of ghrelin receptor agonists, highlighting a link between appetite and nausea. Expert opinion: There is an urgent need to diversify away from historical drug targets. In particular, there is a need to control nausea by regulating ICC functions and/or by facilitating appetite via ghrelin receptor agonists. It is also important to note that different upper gastrointestinal disorders (gastroparesis, chronic unexplained nausea and vomiting, functional dyspepsia) are difficult to distinguish apart, suggesting wider therapeutic opportunity.

Relationship between gastric motility and liquid mixing in the stomach

The relationship between gastric motility and the mixing of liquid food in the stomach was investigated with a numerical analysis. Three parameters of gastric motility were considered: the propagation velocity, frequency, and terminal acceleration of peristaltic contractions. We simulated gastric flow with an anatomically realistic geometric model of the stomach, considering free surface flow and moving boundaries. When a peristaltic contraction approaches the pylorus, retropulsive flow is generated in the antrum. Flow separation then occurs behind the contraction. The extent of flow separation depends on the Reynolds number (Re), which quantifies the inertial forces due to the peristaltic contractions relative to the viscous forces of the gastric contents; no separation is observed at low Re, while an increase in reattachment length is observed at high Re. While mixing efficiency is nearly constant for low Re, it increases with Re for high Re because of flow separation. Hence, the effect of the propagation velocity, frequency, or terminal acceleration of peristaltic contractions on mixing efficiency increases with Re.

Simultaneous anterior and posterior serosal mapping of gastric slow-wave dysrhythmias induced by vasopressin

NEW FINDINGS

What is the central question of this study? This study aimed to provide the first comparison of simultaneous high-resolution mapping of anterior and posterior gastric serosa over sustained periods. What is the main finding and its importance? Episodes of spontaneous gastric slow-wave dysrhythmias increased significantly following intravenous infusion of vasopressin compared with the baseline state. A number of persistent dysrhythmias were defined, including ectopic activation, conduction block, rotor, retrograde and collision/merger of wavefronts. Slow-wave dysrhythmias could occur either simultaneously or independently on the anterior and posterior gastric serosa, and interacted depending on activation-repolarization and frequency dynamics. High-resolution mapping enables mechanistic insights into gastric slow-wave dysrhythmias and is now achieving clinical translation. However, previous studies have focused mainly on dysrhythmias occurring on the anterior gastric wall. The present study simultaneously mapped the anterior and posterior gastric serosa during episodes of dysrhythmias induced by vasopressin to aid understanding of dysrhythmia initiation, maintenance and termination. High-resolution mapping (8 × 16 electrodes on each serosa; 20-74 cm2 ) was performed in anaesthetized dogs. Baseline recordings (21 ± 8 min) were followed by intravenous infusion of vasopressin (0.1-0.5 IU ml-1 at 60-190 ml h-1 ) and further recordings (22 ± 13 min). Slow-wave activation maps, amplitudes, velocity, interval and frequency were calculated, and differences compared between baseline and postinfusion. All dogs demonstrated an increased prevalence of dysrhythmic events following infusion of vasopressin (17 versus 51%). Both amplitude and velocity demonstrated significant differences (baseline versus postinfusion: 3.6 versus 2.2 mV; 7.7 versus 6.5 mm s-1 ; P < 0.05 for both). Dysrhythmias occurred simultaneously or independently on the anterior and posterior serosa, and then interacted according to frequency dynamics. A number of persistent dysrhythmias were compared, including the following: ectopic activation (n = 2 animals), conduction block (n = 1), rotor (n = 2), retrograde (n = 3) and collision/merger of wavefronts (n = 2). We conclude that infusion of vasopressin induces gastric dysrhythmias, which occur across a heterogeneous range of frequencies and patterns. The results demonstrate that different classes of gastric dysrhythmias may arise simultaneously or independently in one or both surfaces of the serosa, then interact according to their relative frequencies. These results will help to inform interpretation of clinical dysrhythmia.

What is nausea? A historical analysis of changing views

The connotation of "nausea" has changed across several millennia. The medical term 'nausea' is derived from the classical Greek terms ναυτια and ναυσια, which designated the signs and symptoms of seasickness. In classical texts, nausea referred to a wide range of perceptions and actions, including lethargy and disengagement, headache (migraine), and anorexia, with an awareness that vomiting was imminent only when the condition was severe. However, some recent articles have limited the definition to the sensations that immediately precede emesis. Defining nausea is complicated by the fact that it has many triggers, and can build-up slowly or rapidly, such that the prodromal signs and symptoms can vary. In particular, disengagement responses referred to as the "sopite syndrome" are typically present only when emetic stimuli are moderately provocative, and do not quickly culminate in vomiting or withdrawing from the triggering event. This review considers how the definition of "nausea" has evolved over time, and summarizes the physiological changes that occur prior to vomiting that may be indicative of nausea. Also described are differences in the perception of nausea, as well as the accompanying physiological responses, that occur with varying stimuli. This information is synthesized to provide an operational definition of nausea.

Acute Slow Wave Responses to High-Frequency Gastric Electrical Stimulation in Patients With Gastroparesis Defined by High-Resolution Mapping

BACKGROUND AND AIMS

High-frequency gastric electrical stimulation (GES) has emerged as a therapy for gastroparesis, but the mechanism(s) of action remain unclear. There is a need to refine stimulation protocols for clinical benefit, but a lack of accurate techniques for assessing mechanisms in clinical trials, such as slow wave modulation, has hindered progress. We thereby aimed to assess acute slow wave responses to GES in gastroparesis patients using high-resolution (HR) (multi-electrode) mapping, across a range of stimulation doses achievable by the Enterra stimulation device (Medtronic Inc., MN, USA).

MATERIALS AND METHODS

Patients with medically refractory gastroparesis (n = 8) undergoing device implantation underwent intraoperative HR mapping (256 electrodes). Baseline recordings were followed by four protocols of increasing stimulation intensity, with washout periods. Slow wave patterns, frequency, velocity, amplitude, and dysrhythmia rates were quantified by investigators blinded to stimulation settings.

RESULTS

There was no difference in slow wave pattern, frequency, velocity, or amplitude between baseline, washout, and stimulation periods (all p > 0.5). Dysrhythmias included ectopic pacemakers, conduction blocks, retrograde propagation, and colliding wavefronts, and dysrhythmia rates were unchanged with stimulation off vs. on (31% vs. 36% duration dysrhythmic; p > 0.5). Symptom scores and gastric emptying were improved at 5.8 month follow-up (p < 0.05).

CONCLUSIONS

High-frequency GES protocols achievable from a current commercial device did not acutely modulate slow wave activity or dysrhythmias. This study advances clinical methods for identifying and assessing therapeutic GES parameters, and can be applied in future studies on higher-energy protocols and devices.

Chronic nausea and vomiting: insights into underlying mechanisms

Chronic nausea and vomiting are common and debilitating symptoms in adults. There are some fundamental problems that make our understanding of mechanisms difficult, diagnostic definitions of patient-cohorts being central. As there is no unifying mechanism with a direct link to chronic nausea or vomiting, it is most likely that several mechanisms interact, e.g., pylorus function and its relation to gastric emptying, or gastric sensory and motor function. In this mini-review, we highlight the roles and evidence for brain-gut interactions as well as gastrointestinal neurophysiologic, motor, sensory, and hormonal factors involved in the pathophysiology of chronic nausea and vomiting. There are factors not mentioned in the text, mostly as they are not well characterized in the setting of chronic symptoms or only in animal models.

Ghrelin and motilin receptors as drug targets for gastrointestinal disorders

The gastrointestinal tract is the major source of the related hormones ghrelin and motilin, which act on structurally similar G protein-coupled receptors. Nevertheless, selective receptor agonists are available. The primary roles of endogenous ghrelin and motilin in the digestive system are to increase appetite or hedonic eating (ghrelin) and initiate phase III of gastric migrating myoelectric complexes (motilin). Ghrelin and motilin also both inhibit nausea. In clinical trials, the motilin receptor agonist camicinal increased gastric emptying, but at lower doses reduced gastroparesis symptoms and improved appetite. Ghrelin receptor agonists have been trialled for the treatment of diabetic gastroparesis because of their ability to increase gastric emptying, but with mixed results; however, relamorelin, a ghrelin agonist, reduced nausea and vomiting in patients with this disorder. Treatment of postoperative ileus with a ghrelin receptor agonist proved unsuccessful. Centrally penetrant ghrelin receptor agonists stimulate defecation in animals and humans, although ghrelin itself does not seem to control colorectal function. Thus, the most promising uses of motilin receptor agonists are the treatment of gastroparesis or conditions with slow gastric emptying, and ghrelin receptor agonists hold potential for the reduction of nausea and vomiting, and the treatment of constipation. Therapeutic, gastrointestinal roles for receptor antagonists or inverse agonists have not been identified.

Nausea: a review of pathophysiology and therapeutics

The sensation of nausea is a common occurrence with diverse causes and a significant disease burden. Nausea is considered to function as a protective mechanism, warning the organism to avoid potential toxic ingestion. Less adaptive circumstances are also associated with nausea, including post-operative nausea, chemotherapy-induced nausea, and motion sickness. A common definition of nausea identifies the symptom as a precursor to the act of vomiting. The interaction, though present, does not appear to be a simple relationship. Nausea is unfortunately the 'neglected symptom', with current accepted therapy generally directed at improving gastrointestinal motility or acting to relieve emesis. Improved understanding of the pathophysiological basis of nausea has important implications for exploiting novel mechanisms or developing novel therapies for nausea relief.

Motion sickness

Over 2000 years ago the Greek physician Hippocrates wrote, "sailing on the sea proves that motion disorders the body." Indeed, the word "nausea" derives from the Greek root word naus, hence "nautical," meaning a ship. The primary signs and symptoms of motion sickness are nausea and vomiting. Motion sickness can be provoked by a wide variety of transport environments, including land, sea, air, and space. The recent introduction of new visual technologies may expose more of the population to visually induced motion sickness. This chapter describes the signs and symptoms of motion sickness and different types of provocative stimuli. The "how" of motion sickness (i.e., the mechanism) is generally accepted to involve sensory conflict, for which the evidence is reviewed. New observations concern the identification of putative "sensory conflict" neurons and the underlying brain mechanisms. But what reason or purpose does motion sickness serve, if any? This is the "why" of motion sickness, which is analyzed from both evolutionary and nonfunctional maladaptive theoretic perspectives. Individual differences in susceptibility are great in the normal population and predictors are reviewed. Motion sickness susceptibility also varies dramatically between special groups of patients, including those with different types of vestibular disease and in migraineurs. Finally, the efficacy and relative advantages and disadvantages of various behavioral and pharmacologic countermeasures are evaluated.

Pathophysiology and treatment of motion sickness

PURPOSE OF REVIEW

Motion sickness remains bothersome in conventional transport and is an emerging hazard in visual information technologies. Treatment remains unsatisfactory but advances in brain imaging, neurophysiology, and neuropharmacology may provide insights into more effective drug and behavioural management. We review these major developments.

RECENT FINDINGS

Recent progress has been in identifying brain mechanisms and loci associated with motion sickness and nausea per se. The techniques have included conventional neurophysiology, pathway mapping, and functional MRI, implicating multiple brain regions including cortex, brainstem, and cerebellum. Understanding of the environmental and behavioural conditions provocative of and protective against motion sickness and how vestibular disease may sensitize to motion sickness has increased. The problem of nauseogenic information technology has emerged as a target for research, motivated by its ubiquitous applications. Increased understanding of the neurophysiology and brain regions associated with motion sickness may provide for more effective medication in the future. However, the polysymptomatic nature of motion sickness, high interindividual variability, and the extensive brain regions involved may preclude a single, decisive treatment.

SUMMARY

Motion sickness is an emerging hazard in information technologies. Adaptation remains the most effective countermeasure together with established medications, notably scopolamine and antihistamines. Neuropharmacological investigations may provide more effective medication in the foreseeable future.

Loss of Interstitial Cells of Cajal and Patterns of Gastric Dysrhythmia in Patients With Chronic Unexplained Nausea and Vomiting

BACKGROUND & AIMS

Chronic unexplained nausea and vomiting (CUNV) is a debilitating disease of unknown cause. Symptoms of CUNV substantially overlap with those of gastroparesis, therefore the diseases may share pathophysiologic features. We investigated this hypothesis by quantifying densities of interstitial cells of Cajal (ICCs) and mapping slow-wave abnormalities in patients with CUNV vs controls.

METHODS

Clinical data and gastric biopsy specimens were collected from 9 consecutive patients with at least 6 months of continuous symptoms of CUNV but normal gastric emptying who were treated at the University of Mississippi Medical Center, and from 9 controls (individuals free of gastrointestinal disease or diabetes). ICCs were counted and ultrastructural analyses were performed on tissue samples. Slow-wave propagation profiles were defined by high-resolution electrical mapping (256 electrodes; 36 cm(2)). Results from patients with CUNV were compared with those of controls as well as patients with gastroparesis who were studied previously by identical methods.

RESULTS

Patients with CUNV had fewer ICCs than controls (mean, 3.5 vs 5.6 bodies/field, respectively; P < .05), with mild ultrastructural abnormalities in the remaining ICCs. Slow-wave dysrhythmias were identified in all 9 subjects with CUNV vs only 1 of 9 controls. Dysrhythmias included abnormalities of initiation (stable ectopic pacemakers, unstable focal activities) and conduction (retrograde propagation, wavefront collisions, conduction blocks, and re-entry), operating across bradygastric, normal (range, 2.4-3.7 cycles/min), and tachygastric frequencies; dysrhythmias showed velocity anisotropy (mean, 3.3 mm/s longitudinal vs 7.6 mm/s circumferential; P < .01). ICCs were less depleted in patients with CUNV than in those with gastroparesis (mean, 3.5 vs 2.3 bodies/field, respectively; P < .05), but slow-wave dysrhythmias were similar between groups.

CONCLUSIONS

This study defined cellular and bioelectrical abnormalities in patients with CUNV, including the identification of slow-wave re-entry. Pathophysiologic features of CUNV were observed to be similar to those of gastroparesis, indicating that they could be spectra of the same disorder. These findings offer new insights into the pathogenesis of CUNV and may help to inform future treatments.

Gastric arrhythmias in gastroparesis: low- and high-resolution mapping of gastric electrical activity

Gastric arrhythmias occur in gastroparesis but their significance is debated. An improved understanding is currently emerging, including newly-defined histopathologic abnormalities in gastroparesis. In particular, the observation that interstitial cells of Cajal are depleted and injured provides mechanisms for arrhythmogenesis in gastroparesis. Electrogastrography has been the dominant clinical method of arrhythmia analysis, but is limited by summative nature, low signal quality, and incomplete sensitivity and specificity. Recently, high-resolution (HR; multi-electrode) mapping has emerged, providing superior spatial data on arrhythmic patterns and mechanisms. However, HR mapping is invasive, and low-resolution approaches are being assessed as bridging techniques until endoscopic mapping is achieved.

The stomach-brain axis

The stomach has distinct functions in relation to the ingestion and handling of solids and liquids. These functions include storage of the food before it is gradually emptied into the duodenum, mechanical crushing of larger food particles to increase the surface area, secretion of an acidic enzyme rich gastric juice and mixing the ingested food with the gastric juice. In addition, the stomach 'senses' the composition of the gastric content and this information is passed via the vagal nerve to the lateral hypothalamus and the limbic system, most likely as palatability signals that influence eating behaviour. Other sensory qualities related to the stimulation of gastric tension receptors are satiety and fullness. Receptors that respond to macronutrient content or gastric wall tension influence appetite and meal related hormone responses. The ingestion of food - in contrast to an infusion of nutrients into the stomach - has distinct effects on the activation of specific brain regions. Brain areas such as thalamus, amygdala, putamen and praecuneus are activated by the ingestion of food. Gastric nutrient infusion evokes greater activation in the hippocampus and anterior cingulate. The brain integrates these interrelated neural and hormonal signals arising from the stomach as well as visual, olfactory and anticipatory stimuli that ultimately influence eating and other behavioural patterns. Furthermore, there is now good evidence from experimental studies that gastric afferents influence mood, and animal studies point towards the possibility that gastric dysfunction may be a risk factor for mood disorders such as anxiety and depression. The stomach is also not only colonised by Helicobacter pylori but a large array of bacteria. While there is sufficient evidence to suggest that H. pylori may alter caloric intake and mood, the role of other gastric microbiome for the brain function is unknown. To address this appropriate targeted gastric microbiome studies would be required instead of widely utilised opportunistic stool microbiome studies. In summary, it is now well established that there are important links between the brain and the stomach that have significant effects on gastric function. However, the stomach also influences the brain. Disturbances in the crosstalk between the stomach and the brain may manifest as functional GI disorders while disturbances in the stomach-brain communication may also result in an altered regulation of satiety and as a consequence may affect eating behaviour and mood. These observations may enable the identification of novel therapies targeted at the gastroduodenum that positively alter brain function and treat or prevent conditions such as obesity or functional gastrointestinal disorders.