Effect of Menstrual Cycle and Menopause on Human Gastric Electrophysiology

Chronic gastroduodenal symptoms disproportionately affect females of childbearing age; however, the effect of menstrual cycling on gastric electrophysiology is poorly defined. To establish the effect of the menstrual cycle on gastric electrophysiology, healthy subjects underwent non-invasive Body Surface Gastric Mapping (BSGM; 8x8 array), with validated symptom logging App (Gastric AlimetryⓇ, New Zealand). Participants were premenopausal females in follicular (n=26) and luteal phases (n=18). Postmenopausal females (n=30) and males (n=51) were controls. Principal gastric frequency (PGF), BMI-adjusted amplitude, Gastric Alimetry Rhythm Index (GA-RI), fasted-fed amplitude ratio (ff-AR), meal response curves, and symptom burden were analysed. Menstrual cycle-related electrophysiological changes were then transferred to an established anatomically-accurate computational gastric fluid dynamics model (meal viscosity 0.1 Pas), to predict the impact on gastric mixing and emptying. PGF was significantly higher in the luteal vs. follicular phase (mean 3.21 cpm, SD (0.17) vs. 2.94 cpm, SD (0.17), p<0.001) and vs. males (3.01 cpm, SD (0.2), p<0.001). In the computational model, this translated to 8.1% higher gastric mixing strength and 5.3% faster gastric emptying for luteal versus follicular phases. Postmenopausal females also exhibited higher PGF than females in the follicular phase (3.10 cpm, SD (0.24) vs. 2.94 cpm, SD (0.17), p=0.01), and higher BMI-adjusted amplitude (40.7 µV (33.02-52.58) vs. 29.6 µV (26.15-39.65), p<0.001), GA-RI (0.60 (0.48-0.73) vs. 0.43 (0.30-0.60), p=0.005), and ff-AR (2.51 (1.79-3.47) vs. 1.48 (1.21-2.17), p=0.001) than males. There were no differences in symptoms. These results define variations in gastric electrophysiology with regard to human menstrual cycling and menopause.

Designing, Developing, and Validating a Set of Standardized Pictograms to Support Pediatric-Reported Gastroduodenal Symptoms

OBJECTIVE

To develop and validate a set of static and animated gastroduodenal symptom pictograms for children.

STUDY DESIGN

There were 3 study phases: 1: cocreation using experience design methods to develop pediatric gastroduodenal symptom pictograms (static and animated); 2: an online survey to assess acceptability, as well as face and content validity; and 3: a preference study. Phases 2 and 3 compared the novel pediatric pictograms with existing pictograms used with adult patients.

RESULTS

Eight children aged 6-15 years (5 female) participated in phase 1, and 69 children in phase 2 (median age 13 years: IQR 9-15); an additional 49 participants were included in phase 3 (median age 15: IQR 12-17). Face and content validity were higher for the pediatric static and animated pictogram sets compared with pre-existing adult pictograms (78% vs 78% vs 61%). Participants with worse gastric symptoms had superior comprehension of the pediatric pictograms (χ2 [8, N = 118] P < .001). All participants preferred the pediatric static pictogram set was over both the animated and adult sets (χ2 [2, N = 118] P < .001).

CONCLUSIONS

The cocreation phase resulted in the symptom concept confirmation and design of 10 acceptable static and animated gastroduodenal pictograms with high face and content validity when evaluated with children aged 6-18. Validity was superior when children reported more problematic symptoms. Therefore, these pictograms could be used in clinical and research practice to enable standardized symptom reporting for children with gastroduodenal disorders.

Transcutaneous Auricular Vagus Nerve Stimulation Normalizes Induced Gastric Myoelectrical Dysrhythmias in Controls Assessed by Body-Surface Gastric Mapping

OBJECTIVES

Transcutaneous auricular vagus nerve stimulation (TaVNS) is a supplementary treatment for gastric symptoms resulting from dysrhythmias. The main objective of this study was to quantify the effects of 10, 40, and 80 Hz TaVNS and sham in healthy individuals in response to a 5-minute water-load (WL5) test.

MATERIALS AND METHODS

Eighteen healthy volunteers aged between 21 and 55 years (body mass index: 27.1 ± 3.2) were recruited. Each subject fasted for up to eight hours and participated in four 95-minute sessions, which consisted of 30 fasted baseline, 30 minutes TaVNS, WL5, and 30 minutes post-WL5. Heart rate variability was assessed using sternal electrocardiogram. Body-surface gastric mapping and bloating (/10) were recorded. One-way ANOVA with post hoc Tukey test was performed to test the difference between TaVNS protocols in terms of frequency, amplitude, bloating scores, root mean square of the successive differences (RMSSD), and stress index (SI).

RESULTS

On average, the subjects consumed 526 ± 160 mL of water, with volume ingested correlated to bloating (mean score 4.1 ± 1.8; r = 0.36, p = 0.029). In general, the reduction in frequency and rhythm stability during the post-WL5 period in sham was normalized by all three TaVNS protocols. Both 40- and 80-Hz protocols also caused increases in amplitude during the stim-only and/or post-WL5 periods. RMSSD increased during the 40-Hz protocol. SI increased during the 10-Hz protocol but decreased during the 40- and 80-Hz protocols.

CONCLUSION

TaVNS proved effective in normalizing gastric dysrhythmias by WL5 in healthy subjects by altering both parasympathetic and sympathetic pathways.

Longitudinal outcome monitoring in patients with chronic gastroduodenal symptoms investigated using the Gastric Alimetry system: study protocol

INTRODUCTION

The Gastric Alimetry platform offers a multimodal assessment of gastric function through body surface gastric mapping (BSGM) and concurrent symptom-tracking via a validated App. We aim to perform a longitudinal cohort study to examine the impact of Gastric Alimetry, and changes in clinical management on patient symptoms, quality of life and psychological health.

METHODS AND ANALYSIS

This is a prospective multicentre longitudinal observational cohort study of participants with chronic gastroduodenal symptoms. Consecutive participants undergoing Gastric Alimetry will be invited to participate. Quality of life will be assessed via EuroQol-5D and the Patient Assessment of Upper Gastrointestinal Disorders-Quality of Life score. Gastrointestinal symptoms will be assessed via the Patient Assessment of Upper Gastrointestinal Symptom Severity index, and the Gastroparesis Cardinal Symptom Index. Psychometrics will be assessed, including anxiety via the General Anxiety Disorder-7, perceived stress using the Perceived Stress Scale 4, and depression via the Patient Health Questionnaire 9. Clinical parameters including diagnoses, investigations and treatments (medication and procedures) will also be captured. Assessments will be made the week after the BSGM test, at 30 days, 90 days, 180 days and 360 days thereafter. The primary outcome is feasibility of longitudinal follow-up of a cohort that have undergone Gastric Alimetry testing; from which patients' continuum of care can be characterised. Secondary outcomes include changes in patient-reported symptoms, quality of life and psychometrics (anxiety, stress and depression). Inferential causal analyses will be performed at the within patient level to explore causal associations between treatment changes and clinical outcomes. The impact of Gastric Alimetry on clinical management will also be captured.

ETHICS AND DISSEMINATION

The protocol has been approved in Aotearoa New Zealand by the Auckland Health Research Ethics Committee. Results will be submitted for conference presentation and peer-reviewed publication.

Efficacy of different surgical treatments for management of anal fistula: a network meta-analysis

PURPOSE

Currently, the anal fistula treatment which optimises healing and preserves bowel continence remains unclear. The aim of our study was to compare the relative efficacy of different surgical treatments for AF through a network meta-analysis.

METHODS

Systematic searches of MEDLINE, EMBASE and CENTRAL databases up to October 2022 identified randomised controlled trials (RCTs) comparing surgical treatments for anal fistulae. Fistulae were classified as simple (inter-sphincteric or low trans-sphincteric fistulae crossing less than 30% of the external anal sphincter (EAS)) and complex (high trans-sphincteric fistulae involving more than 30% of the EAS). Treatments evaluated in only one trial were excluded from the primary analyses to minimise bias. The primary outcomes were rates of success in achieving AF healing and bowel incontinence.

RESULTS

Fifty-two RCTs were included. Of the 14 treatments considered, there were no significant differences regarding short-term (6 months or less postoperatively) and long-term (more than 6 months postoperatively) success rates between any of the treatments in patients with both simple and complex anal fistula. Ligation of the inter-sphincteric fistula tract (LIFT) ranked best for minimising bowel incontinence in simple (99.1% of comparisons; 3 trials, n = 70 patients) and complex anal fistula (86.2% of comparisons; 3 trials, n = 102 patients).

CONCLUSIONS

There is insufficient evidence in existing RCTs to recommend one treatment over another regarding their short and long-term efficacy in successfully facilitating healing of both simple and complex anal fistulae. However, LIFT appears to be associated with the least impairment of bowel continence, irrespective of AF classification.

Optimization of Gastric Pacing Parameters Using High-Resolution Mapping

OBJECTIVE

Abnormal slow-wave activity has been associated with functional motility disorders. Gastric pacing has been investigated to correct slow-wave abnormalities, but clinical therapies are yet to be established. This study aimed to define optimal parameters to advance the application of gastric pacing.

METHODS

High-resolution gastric mapping was utilized to evaluate four pacing parameters in in-vivo pig studies: (i) orientation of the pacing electrodes (longitudinal vs circumferential), (ii) pacing energy (900 vs 10,000 ms mA2), (iii) the pacing location (corpus vs antrum), and (iv) pacing period (between 12 and 36 s).

RESULTS

The probability of slow-wave initiation and entrainment with the pacing electrodes oriented longitudinally was significantly higher than with electrodes orientated circumferentially (86 vs 10%). High-energy pacing accelerated entrainment over the entire mapped field compared to low-energy pacing (3.1±1.5 vs 7.3±2.4 impulses, p < 0.001). Regardless of the location of the pacing site, the new site of slow-wave initiation was always located 4-12 mm away from the pacing site, between the greater curvature and negative pacing electrode. A pacing period between 14-30 s resulted in stable slow-wave initiation and entrainment.

CONCLUSION

These data will now inform effective application of gastric pacing in future studies, including human translation.

Principles and clinical methods of body surface gastric mapping: Technical review

BACKGROUND AND PURPOSE

Chronic gastric symptoms are common, however differentiating specific contributing mechanisms in individual patients remains challenging. Abnormal gastric motility is present in a significant subgroup, but reliable methods for assessing gastric motor function in clinical practice are lacking. Body surface gastric mapping (BSGM) is a new diagnostic aid, employs multi-electrode arrays to measure and map gastric myoelectrical activity non-invasively in high resolution. Clinical adoption of BSGM is currently expanding following studies demonstrating the ability to achieve specific patient subgrouping, and subsequent regulatory clearances. An international working group was formed in order to standardize clinical BSGM methods, encompassing a technical group developing BSGM methods and a clinical advisory group. The working group performed a technical literature review and synthesis focusing on the rationale, principles, methods, and clinical applications of BSGM, with secondary review by the clinical group. The principles and validation of BSGM were evaluated, including key advances achieved over legacy electrogastrography (EGG). Methods for BSGM were reviewed, including device design considerations, patient preparation, test conduct, and data processing steps. Recent advances in BSGM test metrics and reference intervals are discussed, including four novel metrics, being the 'principal gastric frequency', BMI-adjusted amplitude, Gastric Alimetry Rhythm Index™, and fed: fasted amplitude ratio. An additional essential element of BSGM has been the introduction of validated digital tools for standardized symptom profiling, performed simultaneously during testing. Specific phenotypes identifiable by BSGM and the associated symptom profiles were codified with reference to pathophysiology. Finally, knowledge gaps and priority areas for future BSGM research were also identified by the working group.

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.

Normative Values for Body Surface Gastric Mapping Evaluations of Gastric Motility Using Gastric Alimetry: Spectral Analysis

INTRODUCTION

Body surface gastric mapping (BSGM) is a new noninvasive test of gastric function. BSGM offers several novel and improved biomarkers of gastric function capable of differentiating patients with overlapping symptom profiles. The aim of this study was to define normative reference intervals for BSGM spectral metrics in a population of healthy controls.

METHODS

BSGM was performed in healthy controls using Gastric Alimetry (Alimetry, New Zealand) comprising a stretchable high-resolution array (8 × 8 electrodes; 196 cm 2 ), wearable Reader, and validated symptom-logging App. The evaluation encompassed a fasting baseline (30 minutes), 482 kCal meal, and 4-hour postprandial recording. Normative reference intervals were calculated for BSGM metrics including the Principal Gastric Frequency, Gastric Alimetry Rhythm Index (a measure of the concentration of power in the gastric frequency band over time), body mass index (BMI)-adjusted amplitude (μV), and fed:fasted amplitude ratio. Data were reported as median and reference interval (5th and/or 95th percentiles).

RESULTS

A total of 110 subjects (55% female, median age 32 years [interquartile range 24-50], median BMI 23.8 kg/m 2 [interquartile range 21.4-26.9]) were included. The median Principal Gastric Frequency was 3.04 cycles per minute; reference interval: 2.65-3.35 cycles per minute. The median Gastric Alimetry Rhythm Index was 0.50; reference interval: ≥0.25. The median BMI-adjusted amplitude was 37.6 μV; reference interval: 20-70 μV. The median fed:fasted amplitude ratio was 1.85; reference interval ≥1.08. A higher BMI was associated with a shorter meal-response duration ( P = 0.014).

DISCUSSION

This study provides normative reference intervals for BSGM spectral data to inform diagnostic interpretations of abnormal gastric function.

Characterising nationwide reasons for unplanned hospital readmission after colorectal cancer surgery

BACKGROUND

Readmissions after colorectal cancer surgery are common, despite advancements in surgical care, and have a significant impact on both individual patients and overall healthcare costs. The aim of this study was to determine the 30-and 90 days readmission rate after colorectal cancer surgery, and to investigate the risk factors and clinical reasons for unplanned readmissions.

METHOD

A multicenter, population-based study including all patients discharged after index colorectal cancer resection from 2010 to 2020 in Aotearoa New Zealand (AoNZ) was completed. The Ministry of Health National Minimum Dataset was used. Rates of readmission at 30 days and 90 days were calculated. Mixed-effect logistic regression models were built to investigate factors associated with unplanned readmission. Reasons for readmission were described.

RESULTS

Data were obtained on 16,885 patients. Unplanned 30-day and 90-day hospital readmission rates were 15.1% and 23.7% respectively. The main readmission risk factors were comorbidities, advanced disease, and postoperative complications. Hospital level variation was not present. Despite risk adjustment, R² value of models was low (30 days: 4.3%, 90 days: 5.2%). The most common reasons for readmission were gastrointestinal causes (32.1%) and wound complications (14.4%). Rates of readmission did not improve over the 11 years study period (p = 0.876).

CONCLUSION

Readmissions following colorectal resections in AoNZ are higher than other comparable healthcare systems and rates have remained constant over time. While patient comorbidities and postoperative complications are associated with readmission, the explanatory value of these variables is poor. To reduce unplanned readmissions, efforts should be focused on prevention and early detection of post-discharge complications.

Localized bioelectrical conduction block from radiofrequency gastric ablation persists after healing: safety and feasibility in a recovery model

Gastric ablation has demonstrated potential to induce conduction blocks and correct abnormal electrical activity (i.e., ectopic slow-wave propagation) in acute, intraoperative in vivo studies. This study aimed to evaluate the safety and feasibility of gastric ablation to modulate slow-wave conduction after 2 wk of healing. Chronic in vivo experiments were performed in weaner pigs (n = 6). Animals were randomly divided into two groups: sham-ablation (n = 3, control group; no power delivery, room temperature, 5 s/point) and radiofrequency (RF) ablation (n = 3; temperature-control mode, 65°C, 5 s/point). In the initial surgery, high-resolution serosal electrical mapping (16 × 16 electrodes; 6 × 6 cm) was performed to define the baseline slow-wave activation profile. Ablation (sham/RF) was then performed in the mid-corpus, in a line around the circumferential axis of the stomach, followed by acute postablation mapping. All animals recovered from the procedure, with no sign of perforation or other complications. Two weeks later, intraoperative high-resolution mapping was repeated. High-resolution mapping showed that ablation successfully induced sustained conduction blocks in all cases in the RF-ablation group at both the acute and 2 wk time points, whereas all sham-controls had no conduction block. Histological and immunohistochemical evaluation showed that after 2 wk of healing, the lesions were in the inflammation and early proliferation phase, and interstitial cells of Cajal (ICC) were depleted and/or deformed within the ablation lesions. This safety and feasibility study demonstrates that gastric ablation can safely and effectively induce a sustained localized conduction block in the stomach without disrupting the surrounding slow-wave conduction capability.NEW & NOTEWORTHY Ablation has recently emerged as a tool for modulating gastric electrical activation and may hold interventional potential for disorders of gastric function. However, previous studies have been limited to the acute intraoperative setting. This study now presents the safety of gastric ablation after postsurgical recovery and healing. Localized electrical conduction blocks created by ablation remained after 2 wk of healing, and no perforation or other complications were observed over the postsurgical period.

Validation of noninvasive body-surface gastric mapping for detecting gastric slow-wave spatiotemporal features by simultaneous serosal mapping in porcine

Gastric disorders are increasingly prevalent, but reliable noninvasive tools to objectively assess gastric function are lacking. Body-surface gastric mapping (BSGM) is a noninvasive method for the detection of gastric electrophysiological features, which are correlated with symptoms in patients with gastroparesis and functional dyspepsia. Previous studies have validated the relationship between serosal and cutaneous recordings from limited number of channels. This study aimed to comprehensively evaluate the basis of BSGM from 64 cutaneous channels and reliably identify spatial biomarkers associated with slow-wave dysrhythmias. High-resolution electrode arrays were placed to simultaneously capture slow waves from the gastric serosa (32 × 6 electrodes at 4 mm spacing) and epigastrium (8 × 8 electrodes at 20 mm spacing) in 14 porcine subjects. BSGM signals were processed based on a combination of wavelet and phase information analyses. A total of 1,185 individual cycles of slow waves were assessed, out of which 897 (76%) were classified as normal antegrade waves, occurring in 10 (71%) subjects studied. BSGM accurately detected the underlying slow wave in terms of frequency (r = 0.99, P = 0.43) as well as the direction of propagation (P = 0.41, F-measure: 0.92). In addition, the cycle-by-cycle match between BSGM and transitions of gastric slow wave dysrhythmias was demonstrated. These results validate BSGM as a suitable method for noninvasively and accurately detecting gastric slow-wave spatiotemporal profiles from the body surface.NEW & NOTEWORTHY Gastric dysfunctions are associated with abnormalities in the gastric bioelectrical slow waves. Noninvasive detection of gastric slow waves from the body surface can be achieved through multichannel, high-resolution, body-surface gastric mapping (BSGM). BSGM matched the spatiotemporal characteristics of gastric slow waves recorded directly and simultaneously from the serosal surface of the stomach. Abnormal gastric slow waves, such as retrograde propagation, ectopic pacemaker, and colliding wavefronts can be detected by changes in the phase of BSGM.

The role of colonic motility in low anterior resection syndrome

Low anterior resection syndrome (LARS) describes the symptoms and experiences of bowel dysfunction experienced by patients after rectal cancer surgery. LARS is a complex and multifactorial syndrome exacerbated by factors such as low anastomotic height, defunctioning of the colon and neorectum, and radiotherapy. There has recently been growing awareness and understanding regarding the role of colonic motility as a contributing mechanism for LARS. It is well established that rectosigmoid motility serves an important role in coordinating rectal filling and maintaining continence. Resection of the rectosigmoid may therefore contribute to LARS through altered distal colonic and neorectal motility. This review evaluates the role of colonic motility within the broader pathophysiology of LARS and outlines future directions of research needed to enable targeted therapy for specific LARS phenotypes.

Outcomes following out-of-hours acute cholecystectomy: A systematic review and meta-analysis

BACKGROUND

Cholecystectomy is one of the most commonly performed abdominal operations. Rising demands on acute operating theater availability and resource utilization in the daytime have led to acute cholecystectomy being performed out-of-hours (in the evenings, at night, or on weekends), although it remains unknown whether outcomes differ between out-of-hours and in-hours (during the daytime on weekdays) acute cholecystectomy. This systematic review and meta-analysis aimed to compare outcomes following out-of-hours versus in-hours acute cholecystectomy.

METHODS

The study protocol was prospectively registered on PROSPERO (ID: CRD42021226127). MEDLINE, EMBASE, and Scopus databases were systematically searched for studies comparing outcomes following out-of-hours and in-hours acute cholecystectomy in adults with any acute benign gallbladder disease. The outcomes of interest were rates of bile leakage, bile duct injury, overall postoperative complications, conversion to open cholecystectomy, specific intraoperative and postoperative complications, length of stay, readmission, and mortality. Subgroup (evening/night-time vs. daytime, weekend vs. weekday, acute surgical unit [ASU]-only, non-ASU, and laparoscopic-only) and sensitivity analyses of adjusted multivariate regression analysis results was also performed.

RESULTS

Eleven studies were included. There were no differences between out-of-hours and in-hours acute cholecystectomy for rates of bile leakage, bile duct injury, overall postoperative complications, conversion to open cholecystectomy, operative duration, readmission, mortality, and postoperative length of stay. Higher rates of postoperative sepsis (odds ratio, 1.58; 95% confidence interval, 1.04-2.41; p = 0.03) and pneumonia (odds ratio, 1.55; 95% confidence interval, 1.06-2.26; p = 0.02) were observed following out-of-hours acute cholecystectomy on univariate meta-analysis, but not after the adjusted multivariate meta-analysis. Higher conversion rates were observed when out-of-hours cholecystectomy was performed in centers without an ASU.

CONCLUSION

This systematic review and meta-analysis has not shown an increased risk in overall or specific complications associated with out-of-hours compared with in-hours acute cholecystectomy. However, future studies should assess the potential impact of structural hospital factors, such as an ASU, on outcomes following out-of-hours acute cholecystectomy.

LEVEL OF EVIDENCE

Systematic Review and Meta-Analysis Study, Level IV.

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.

Comparison of gold and PEDOT:PSS contacts for high-resolution gastric electrical mapping using flexible printed circuit arrays

Motility of the stomach is governed by an electrophysiological event termed gastric slow waves. High-resolution (HR) bioelectrical mapping involves placing array of electrodes over the surface of the stomach to record gastric slow waves. Conductive polymer materials have recently been applied to great effect in cardiology and neurophysiology due to its compliant and biocompatible properties. The aim of this study was to quantify the performance of poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) deposited on a flexible print circuit electrode array for gastric slow wave HR mapping. The Au electrodes were coated with PEDOT:PSS at 1 V and different levels of charges (0.3-1.2 mC). HR mapping alongside standard Au electrodes was performed in three anesthetized pigs. Overall, the PEDOT:PSS electrodes detected both antegrade and retrograde slow wave propagations, with comparable frequency, velocity and signal-to-noise ratio to the Au electrodes. Differences between the two electrodes were noted in terms of amplitude and downstroke gradient. The findings of this study will inform designs of future stretchable and implantable HR mapping electrode arrays for gastrointestinal recording and stimulation therapies.

322 Clinical Factors Predictive of Both Successful and Unsuccessful Arterial Embolization in The Management of Lower Gastrointestinal Bleeding

Aim

To develop a model of clinical factors that may predict: (1) technically and clinically successful embolization of a bleeding vessel at Digital Subtraction Angiography (DSA) for lower gastrointestinal bleed (LGIB); (2) a negative DSA in the presence of positive CT-mesenteric angiography (CTMA) for LGIB.

Method

A retrospective cohort study of all DSAs conducted with intent for embolization for acute LGIB over a 10-year period was undertaken. Pre-procedural and intra-procedural clinical variables were evaluated using uni- and multi-variate analysis.

Results

123 DSAs were evaluated. Technical success was 81% (64/78) with clinical success 78%. Technical success was associated with super-selective approach, contrast extravasation on CT, haemoglobin drop, anatomical source and time from CT to DSA on univariate analysis. On multivariate analysis time from CT to DSA was significant with a higher success probability within 120 minutes with different factors being salient depending on degree of delay. Clinical success was only associated with APTT (&lt;27.5s). Technical failure from a negative DSA following a positive CTMA was associated with anatomical source, haemodynamic stability, platelet count and time from CT to DSA on univariate analysis. The latter three remained so on multivariate analysis.

Conclusions

A triaging approach to utilising emergency DSA may be helpful. If prolonged delay between a positive CT and DSA is anticipated, with haemodynamic stability and a near normal platelet count, the DSA may not be fruitful. Technical success may be more likely if DSA occurs within 120mins. Clinical success may be more likely if APTT is within normal range.

Gastric dysrhythmia in gastroesophageal reflux disease: a systematic review and meta-analysis

BACKGROUND

Gastroesophageal reflux disease (GERD) is a commonly diagnosed gastrointestinal disorder, with a substantial impact on the quality of life. The underlying pathophysiology of GERD is multifactorial and incompletely understood. Abnormal gastric electrical activity, measured using electrogastrography (EGG), may contribute. This study aimed to systematically review and meta-analyse the existing literature in which EGG was used in patients with GERD.

METHODS

Databases were systematically searched for studies using EGG in adults with GERD. The primary outcome was the percentage of recording time in the normogastric frequency range. Secondary outcomes were dominant frequency, dominant power, power ratio and prevalence of any EGG abnormality.

RESULTS

In total, 591 participants (427 patients with GERD; 164 healthy controls) from 13 studies were included. GERD patients spent 17.3% (SMD - 1.18, 95%CI: - 1.84, - 0.52) and 18.7% (SMD - 1.11, 95%CI: - 1.55, - 0.68) less of the preprandial and postprandial recording time in normogastric frequency ranges, respectively, compared to healthy controls. The dominant frequency, dominant power and power ratio were not significantly different to healthy controls in the preprandial and postprandial periods. The pooled prevalence of any EGG abnormality was significantly greater in patients with GERD than in healthy controls [46% (95%CI: 39-64%) vs. 10% (95%CI: 4-23%); p < 0.0001]. Correlations between GERD symptoms and EGG recordings were inconsistently studied. EGG techniques were heterogeneous.

CONCLUSIONS

Consistent abnormalities in gastric slow-wave activity, as measured by EGG, were identified in adults with GERD. Further investigation into these abnormalities using novel emerging electrophysiology techniques is desirable, to better define their contribution toward GERD pathophysiology.

Transcutaneous Electrical Stimulation for Neurogenic Bladder Dysfunction Following Spinal Cord Injury: Meta-Analysis of Randomized Controlled Trials

OBJECTIVES

To assess the efficacy of transcutaneous electrical nerve stimulation (TENS) for neurogenic bladder dysfunction secondary to spinal cord injury (SCI).

MATERIALS AND METHODS

A systematic search of MEDLINE, EMBASE, Web of Science, Scopus, and Cochrane libraries up to February 2021 was performed using PRISMA methodology. All randomized controlled trials (RCTs) that studied TENS for neurogenic bladder in a SCI population were included. The primary outcomes of interest were maximum cystometric capacity (MCC) and maximum detrusor pressure (Pdet). Meta-analysis was conducted with RevMan v5.3.

RESULTS

Six RCTs involving 353 participants were included. Meta-analysis showed that TENS significantly increased MCC (standardized mean difference 1.11, 95% confidence interval [CI] 0.08-2.14, p = 0.03, I²  = 54%) in acute SCI. No benefits were seen for maximum Pdet. TENS was associated with no major adverse events.

CONCLUSIONS

TENS may be an effective, safe intervention for neurogenic bladder dysfunction following SCI. Further studies are essential to confirm these results and more work is required to determine optimal stimulation parameters and duration of the treatment.

Impact of gastric resection and enteric anastomotic configuration on delayed gastric emptying after pancreaticoduodenectomy: a network meta-analysis of randomized trials

Introduction

Delayed gastric emptying (DGE) is frequent after pancreaticoduodenectomy (PD). Several RCTs have explored operative strategies to minimize DGE, however, the optimal combination of gastric resection approach, anastomotic route, configuration and the use of enteroenterostomy remains unclear.

Methods

MEDLINE, Embase and CENTRAL databases were systematically searched for RCTs comparing gastric resection (classic Whipple, pylorus-resecting, pylorus-preserving), anastomotic route (antecolic, retrocolic), configuration (loop gastroenterostomy/Billroth II, Roux-en-Y), and use of enteroenterostomy (Braun). A random-effects, Bayesian network meta-analysis with non-informative priors was conducted to determine the optimal combination of approaches to PD for minimizing DGE.

Results

Twenty-four RCTs, including 2526 patients and 14 approaches were included. There was some heterogeneity, although inconsistency was low. The overall incidence of DGE was 25.6 per cent (647 patients). Pylorus-resecting, antecolic, Billroth II with Braun enteroenterostomy was associated with the lowest rates of DGE and ranked the best in 35 per cent of comparisons. Classic Whipple, retrocolic, Billroth II with Braun ranked the worst for DGE in 32 per cent of comparisons. Pairwise meta-analysis of retrocolic versus antecolic route for gastrojejunostomy found increased risk of DGE with the retrocolic route (odds ratio 2.10, 95 per cent credibility interval (cr.i.) 0.92 to 4.70). Pairwise meta-analysis of enteroenterostomy found a trend towards lower DGE rates when this was used (odds ratio 1.90, 95 per cent cr.i. 0.92 to 3.90). Having a Braun enteroenterostomy ranked the best in 96 per cent of comparisons.

Conclusion

Based on existing RCT evidence, a pylorus-resecting, antecolic, Billroth II with Braun enteroenterostomy seems to be associated with the lowest rates of DGE.

Preregistration

PROSPERO submitted 23 December 2020. CRD42021227637

Risk factors for readmission with dehydration after ileostomy formation: A systematic review and meta-analysis

AIM

Ileostomy formation is a commonly performed procedure with substantial associated morbidity. Patients with an ileostomy experience high rates of unplanned hospital readmission with dehydration, and such events have a long-term health and economic impact. Reports of the significant risk factors associated with these readmissions have been inconsistent. This study aimed to identify the significant risk factors for readmission with dehydration following ileostomy formation.

METHOD

A systematic search was conducted using the Medline, Embase, Cochrane and CINAHL databases. All original research articles reporting risk factors for readmission with dehydration following ileostomy formation in adults were included. The primary outcome was the pooled risk ratio of clinically relevant variables potentially associated with dehydration-related readmission following ileostomy formation. The secondary outcome was the incidence of dehydration-related readmission.

RESULTS

Ten studies (27 089 patients) were included. The incidences of 30- and 60-day readmission with dehydration were 5.0% (range 2.1%-13.2%) and 10.3% (range 7.3%-14.1%), respectively. Eight variables were found to be significantly associated with dehydration-related readmission: age ≥65 years, body mass index ≥30 kg/m² , diabetes mellitus, hypertension, renal comorbidity, regular diuretic use, ileal pouch-anal anastomosis procedure and length of stay after index admission. A preoperative diagnosis of colorectal cancer was less likely to result in readmission with dehydration.

CONCLUSION

Readmission with dehydration following ileostomy formation is a significant issue with several risk factors. Awareness of these risk factors will help inform the design of future studies addressing risk prediction, allow risk stratification of ileostomates and aid in the development of personalized prevention strategies.

Design and Validation of a Surface-Contact Electrode for Gastric Pacing and Concurrent Slow-Wave Mapping

OBJECTIVE

Gastric contractions are, in part, coordinated by slow-waves. Functional motility disorders are correlated with abnormal slow-wave patterns. Gastric pacing has been attempted in a limited number of studies to correct gastric dysmotility. Integrated electrode arrays capable of pacing and recording slow-wave responses are required.

METHODS

New flexible surface-contact pacing electrodes (SPE) that can be placed atraumatically to pace and simultaneously map the slow-wave activity in the surrounding area were developed. SPE were applied in pigs in-vivo for gastric pacing along with concurrent high-resolution slow wave mapping as validation. Histology was conducted to assess for tissue damage around the pacing site. SPE were compared against temporary cardiac pacing electrodes (CPE), and hook-shaped pacing electrodes (HPE), for entrainment rate, entrainment threshold, contact quality, and slow-wave propagation patterns.

RESULTS

Pacing with SPE (amplitude: 2 mA, pulse width: 100 ms) consistently achieved pacemaker initiation. Histological analysis illustrated no significant tissue damage. SPE resulted in a higher rate of entrainment (64%) than CPE (37%) and HPE (24%), with lower entrainment threshold (25% of CPE and 16% of HPE). High resolution mapping showed that there was no significant difference between the initiated slow-wave propagation speed for SPE and CPE (6.8 ± 0.1 vs 6.8 ± 0.2 mm/s, P>0.05). However, SPE had higher loss of tissue lead contact quality than CPE (42 ± 16 vs 13 ± 10% over 20 min).

CONCLUSION

Pacing with SPE induced a slow-wave pacemaker site without tissue damage.

SIGNIFICANCE

SPE offered an atraumatic pacing electrode with a significant reduction of power consumption and placement time compared to impaled electrodes.

Relationships between serum electrolyte concentrations and ileus: A joint clinical and mathematical modeling study

Aim

Prolonged postoperative ileus (PPOI) occurs in around 15% of patients after major abdominal surgery, posing a significant clinical and economic burden. Significant fluid and electrolyte changes may occur peri‐operatively, potentially contributing to PPOI; however, this association has not been clearly elucidated. A joint clinical‐theoretical study was undertaken to evaluate peri‐operative electrolyte concentration trends, their association with ileus, and predicted impact on bioelectrical slow waves in interstitial cells of Cajal (ICC) and smooth muscle cells (SMC).

Methods

Data were prospectively collected from 327 patients undergoing elective colorectal surgery. Analyses were performed to determine associations between peri‐operative electrolyte concentrations and prolonged ileus. Biophysically based ICC and SMC mathematical models were adapted to evaluate the theoretical impacts of extracellular electrolyte concentrations on cellular function.

Results

Postoperative day (POD) 1 calcium and POD 3 chloride, sodium were lower in the PPOI group (p < 0.05), and POD3 potassium was higher in the PPOI group (p < 0.05). Deficits beyond the reference range in PPOI patients were most notable for sodium (Day 3: 29.5% ileus vs. 18.5% no ileus, p = 0.04). Models demonstrated an 8.6% reduction in slow‐wave frequency following the measured reduction in extracellular NaCl on POD5, with associated changes in cellular slow‐wave morphology and amplitude.

Conclusion

Low serum sodium and chloride concentrations are associated with PPOI. Electrolyte abnormalities are unlikely to be a primary mechanism of ileus, but their pronounced effects on cellular electrophysiology predicted by modeling suggest these abnormalities may adversely impact motility recovery. Resolution and correction of electrolyte abnormalities in ileus may be clinically relevant.