Enteric transit and absorption after canine ileostomy. Effect of pacing

Intestinal Electrical Stimulation to Increase the Rate of Peristalsis

BACKGROUND

Pediatric gastrointestinal motility disorders are a large and broad group. Some of these disorders have been effectively treated with electrical stimulation. The goal of our present study is to determine whether the rate of intestinal peristalsis can be increased with electrical stimulation.

METHODS

Juvenile mini-Yucatan pigs were placed under general anesthesia and a short segment of the jejunum was transected. Ultrasound gel was placed inside the segment. The segment of the jejunum was first monitored for 20 min under no stimulation, followed by direct electrical stimulation using a planar electrode. The gel extruded out of the intestine via peristalsis was collected and weighed for each 20-min time interval.

RESULTS

Effective delivery of the current to the intestine was confirmed via direct measurements. When there was no direct intestinal electrical stimulation, an average of 0.40 g of gel was expelled in 20 min, compared to 1.57 g of gel expelled during direct electrical stimulation (P < 0.01).

CONCLUSIONS

Direct intestinal electrical stimulation accelerates the transit of gastrointestinal contents. This approach may be useful in the treatment of a range of pediatric motility disorders.

Duodenum electrical stimulation delays gastric emptying, reduces food intake and accelerates small bowel transit in pigs

Duodenum electrical stimulation (DES) has been shown to delay gastric emptying and reduce food intake in dogs. The aim of this study was to investigate the effects of DES on gastric emptying, small bowel transit and food intake in pigs, a large animal model of obesity. The study consisted of three experiments (gastric emptying, small bowel transit, and food intake) in pigs implanted with internal duodenal electrodes for DES and one or two duodenal cannulas for gastric emptying and small bowel transit. We found that (i) gastric emptying was dose-dependently delayed by DES of different stimulation parameters; (ii) small bowel transit was significantly accelerated with continuous DES in proximal intestine but not with intermittent DES; (iii) DES significantly reduced body weight gain with 100% duty cycle (DC), but not with DES with 40% DC. A marginal difference was noted in food intake among 100% DC session, 40% DC session, and control session. DES with long pulses energy-dependently inhibits gastric emptying in pigs. DES with appropriate parameters accelerates proximal small bowel transit in pigs. DES reduces body weight gain in obese pigs, and this therapeutic effect on obesity is mediated by inhibiting gastric emptying and food intake, and may also possibly by accelerating intestinal transit. DES may have a potential application to treat patients with obesity.

Mechanisms and potential applications of intestinal electrical stimulation

PURPOSE

Electrical stimulation of the gut has recently been under intensive investigation and various studies have revealed therapeutic potentials of gastrointestinal electrical stimulation for gastrointestinal motility disorders and obesity. While there have been a number of reviews on gastric electrical stimulation, there is a lack of systematic reviews on intestinal electrical stimulation. The aim of this review is to provide an overview on the effects, mechanisms, and applications of intestinal electrical stimulation.

RESULTS

We evaluated published data on intestinal electrophysiology, pathophysiology, and different methodologies on intestinal electrical stimulation and its possible mechanisms in both research and clinical settings using the MEDLINE database for English articles from 1963 to 2008. Based on this systematic review, intestinal electrical stimulation has been reported to alter intestinal slow waves, contractions and transit; the effects were mediated via both vagal and adrenergic pathways. Intestinal electrical stimulation has been reported to have potentials for treating various intestinal motility disorders and obesity.

CONCLUSIONS

It is concluded that intestinal electrical stimulation may have promising applications for treating motility disorders associated with altered intestinal contractile activity. The most recent studies have revealed possible applications of intestinal electrical stimulation for the treatment of obesity. Basic research results are promising; however, further clinical studies are needed to bring IES from bench to bedside.

Intestinal electric stimulation accelerates whole gut transit and promotes fat excrement in conscious rats

INTRODUCTION

Intestinal electric stimulation (IES) is proposed as a potential tool for the treatment of morbid obesity. Our earlier study showed that IES with one pair of electrodes accelerated intestinal transit and decreased fat absorption in a segment of the jejunum in anesthetized rats. The aims of this study were to assess the effects of IES on whole gut transit and fat absorption in conscious rats, to examine the effects of multi-pairs IES and to explore the cholinergic mechanism behind the effects of IES.

METHODS

Thirty-eight male rats implanted with serosal electrodes were randomized into five groups: control without IES, two- or three-pairs IES with short pulses, atropine and atropine plus IES. The whole gut transit and fat remained and emptied from the gut were analyzed after continuous 2-h IES.

RESULTS

Two- and three-pairs IES significantly accelerated phenol red (PR, marker used for transit) excretion (analysis of variance (ANOVA), P<0.001). No significant difference was found between two- and three-pairs IES. Two-pairs IES significantly increased the excretion of fat (P<0.05). Atropine significantly blocked the accelerated transit induced by IES (ANOVA, P<0.001). Correlation was found between the percentage of PR and fat retained in the whole gut (r=0.497, P<0.01).

CONCLUSIONS

IES accelerates whole gut transit and promotes fat excrement in conscious rats, and these effects are mediated through the cholinergic nerves. These findings are in support of the concept that IES may be a promising treatment option for obesity.

Central neuronal mechanisms of intestinal electrical stimulation: effects on duodenum distention-responsive (DD-R) neurons in the VMH of rats

Intestinal electrical stimulation (IES) has been shown to produce inhibitory effects on gastric contractions, gastric emptying, food intake and body weight in rats and dogs, suggesting a therapeutic potential for obesity. The aims of this study were (1) to test the hypothesis that the neurons in the VMH are involved in the central mechanisms of IES treatment for obesity; (2) to compare the effects of IES at the duodenum and IES at the ileum on neuronal activities of the VMH; (3) to better understand if the neuronal activity modulated by IES was mediated via the vagal pathway. Extracellular potentials of neurons in the VMH were recorded in 18 anesthetized rats. IES at the duodenum or ileum was performed in duodenal-distention responsive (DD-R) neurons with 3 sets of parameters (IES-1 with trains of short-pulses: 4mA, 2s-on, 3s-off, 2ms, 20Hz; IES-2 with long-pulses: 6mA, 20cpm, 100ms; IES-3, same as IES-1 but 40Hz). IES-1 at the duodenum and the ileum activated 70.6% and 73.3% of the DD-R neurons, respectively. Similar percentages of the neurons were activated with IES-3 at the duodenum and the ileum (70.6% vs. 66.7%, P=0.91), respectively. IES-2 at these locations activated only 25% and 46.2% of the DD-R neurons, respectively (P>0.05). IES at the duodenum with parameter set, IES-1 or IES-3 was significantly more potent than the parameter set, IES-2 (neuronal activation: 70.6% vs. 25%, P<0.05). Bilateral vagotomy only partially blocked the effects of IES on the neuronal activity in the VMH, indicating that extra-vagal pathways can mediate these effects. IES with different parameters activates 25-70.6% of the VMH neurons responsive to DD, and IES with trains of short-pulses seems more effective than IES with long-pulses. The vagal pathway and extra-vagal pathways are involved in the modulatory effects of IES on the central neurons in the satiety center.

Pouchitis: an evolving clinical enigma--a review

While the overall incidence of pouchitis is low, extensive research continues at clinical and experimental levels in attempts to unravel its etiology. The ileal pouch and pouchitis together represent a unique in vivo opportunity to study mucosal adaptation and inflammation in depth. In the recent past, molecular data relating to pouchitis has significantly expanded. These data provide invaluable insight into intracellular and extracellular events that underpin mucosal adaptation and inflammation. Advances in classification, risk factor evaluation, and prevention have meant that a review of this data, as well as its relationship to our current understanding of pouchitis, is both timely and warranted. Therefore, the aim of this review is to summarize recent data in the context of the established literature.

Gastrointestinal electrical stimulation for treatment of gastrointestinal disorders: gastroparesis, obesity, fecal incontinence, and constipation

Electrical stimulation of the gastrointestinal (GI) tract is an attractive concept. Since these organs have their own natural pacemakers, the electrical signals they generate can be altered by externally delivering electric currents by intramuscular, serosal, or intraluminal electrodes to specific sites in the GI tract. This article reviews the advances in electrical stimulation of the GI tract by describing various methods of GI electrical stimulation and their peripheral and central effects and mechanisms; updating the status of GI electrical stimulation in the clinical settings of gastroparesis, obesity, fecal incontinence, and constipation; and predicting future directions and developments of GI electrical stimulation technology and their areas of possible clinical applications.

Intestinal electric stimulation decreases fat absorption in rats: therapeutic potential for obesity

OBJECTIVE

Effective treatment of obesity is based on the restriction of food intake or reduction of absorption or both. The aim of this study was to study whether intestinal electric stimulation (IES) would reduce fat absorption and, thus, would be a potential therapy for obesity.

RESEARCH METHODS AND PROCEDURES

Forty rats implanted with serosal electrodes and two jejunal cannulas were divided into 4 groups of 10 each: control (no stimulation), IES with long pulses, IES with trains of short pulses, and IES with trains of short pulses plus treatment with lidocaine. Jejunal transit and fat absorption of a 20-cm jejunal segment (between two cannulas) were investigated during a 45-minute period with or without IES.

RESULTS

It was found that both methods of IES accelerated intestinal transit measured by recovery of phenol red and increased the percentage of triglycerides recovered from the distal cannula in comparison with the control group. IES with trains of short pulses was more effective than IES with long pulses in accelerating jejunal transit and reducing fat absorption. Neither of the two IES methods altered the output of fatty acids from the distal cannula. The effects of IES with trains of short pulses on the transit and fat absorption were partially abolished with the treatment of lidocaine.

DISCUSSION

It was concluded that IES accelerates intestinal transit and reduces fat absorption, suggesting a therapeutic potential for obesity. IES with trains of short pulses is more effective than IES with long pulses, and its effects are partially mediated by enteric nerves, jejunum.

Electrical stimulation of the vagus nerve restores motility in an animal model of achalasia

Esophageal peristalsis generally does not return to normal after surgical treatment of achalasia. Direct electrical stimulation of the vagus nerve is known to stimulate antegrade peristalsis in the normal esophagus; however, it is not known whether electrical stimulation will induce return of peristalsis once an achalasia-like disorder has been established. The objective of this study was to perform quantitive and qualitative measurements of motility during electrical stimulation of the vagal nerve in an animal model of achalasia. An already established and verified animal achalasia model using adult North American opossums (Didelphis virginiana) was used. Fifteen opossums were divided into three groups. Sham surgery was performed on three animals (group 1). In group 2 (n=6) a loose Gore-Tex band (110% of the esophageal circumference) was placed around the gastroesophageal junction to prevent relaxation of the lower esophageal sphincter during swallowing. In group 3 (n=6) a relatively tighter band (90% of the esophageal circumference) was used to further elevate the lower esophageal sphincter pressure. At 6 weeks, after manometric and radiolologic confirmation of achalasia, electrical stimulation of the esophagus was performed before and after removal of the band using a graduated square-wave electrical stimulus. Changes in esophageal neural plexi were assessed histologically. Pre- and postoperative manometric data were compared using standard statistical techniques. No difference was observed in esophageal characteristics and motility after sham surgery in group 1. Animals in group 2 demonstrated a vigorous variety of achalasia (high-amplitude, simultaneous, repetitive contractions), moderate esophageal dilatation, and degeneration of 40% to 60% of intramuscular nerve plexi. Animals in group 3 developed amotile achalasia with typical low-amplitude simultaneous (mirror image) contractions, severely dilated ("bird beak") esophagus, and degeneration of 50% to 65% of nerve plexi. Vagal stimulation in group 2 demonstrated a significant increase in the amplitude of contractions (P<0.001) and return of peristaltic activity in 49% of swallows before band removal. After band removal, all of the contractions were peristaltic. In group 3 vagal stimulation before and after removal of the band demonstrated a significant increase in amplitude of contractions (P<0.0001) but no return of propagative peristalsis before band removal, however, 44% of contractions were progressive in the smooth portion of the esophagus after removal of the band. Electrical stimulation of the vagus nerve improved the force of esophageal contractions irrespective of the severity of the disease; however, peristaltic activity completely returned to normal only in the vigorous (early) variety of achalasia. Removal of the functional esophageal outlet obstruction, as with a surgical myotomy, may be necessary to obtain significant peristalsis with vagal pacing in severe achalasia.

Gastrointestinal pacing

Gastrointestinal pacing has been used to alter motor function and is effective in animal models in modulating gastric emptying, intestinal transit, and absorption. Application of gastrointestinal pacing to disorders of the human stomach and small bowel is an attractive treatment option that may some day become a clinical reality. Several technical problems must be overcome before further clinical testing can proceed.

Anal sphincter-saving operations for chronic ulcerative colitis

Three anal sphincter-saving operations--ileorectostomy, ileal pouch-anal anastomosis, and ileal pouch-distal rectal anastomosis--are currently being used in the surgical treatment of chronic ulcerative colitis. All three operations remove the disease, or most of it, and yet they maintain transanal defecation, reasonable fecal continence, and a satisfactory quality of life. All three avoid permanent abdominal ileostomy. Ileorectostomy is the easiest to perform, but it leaves residual disease in the remaining rectum and proximal anal canal that may cause symptoms and that may predispose the patient to cancer. In contrast, ileal pouch-anal anastomosis, although a more technically demanding procedure, totally eradicates the colitis. Its main drawbacks--frequent stooling, nocturnal fecal spotting, and pouchitis--are usually satisfactorily treated with loperamide hydrochloride and metronidazole. Ileal pouch-distal rectal anastomosis is somewhat easier to perform than ileal pouch-anal anastomosis and may result in less nocturnal fecal spotting. Like ileorectostomy, however, the operation leaves residual disease in the distal rectum and proximal anal canal. Considering all of these factors, the ileal pouch-anal operation is preferred today for most patients who require surgery for chronic ulcerative colitis.