Electrical pacing of the Roux limb resolves delayed gastric emptying

Evaluation of Pacing Parameters to Induce Contractions in the Small Intestine

Postoperative ileus and chronic intestinal pseudo-obstruction are intestinal motility disorders that can compromise bowel function resulting in a significant reduction in quality of life and prolonged hospital stays. While medication and nutritional support provides relief for some patients, a significant patient population remains untreated. Therefore, alternative treatment options are required. A novel framework that enables small intestine pacing and video mapping of the contractile response was developed. Pacing pulse parameters (pulse-period: 2.7, 10 s, pulse-width: 100, 400 ms, and pulse-amplitude: 4, 6, 8 mA) were systematically varied to investigate the effect of pacing on the small intestine contractility. The contractile response was quantified by computing the strain of the intestinal diameter at the pacing site. The framework was applied in vivo on porcine jejunal loops (n=4) where segmental contractions were induced in response to pacing pulses. Strain increased with increasing pulse-amplitude and pulse-width, while pacing at a period of 2.7 s elicited higher contractile strains compared to pacing at a period of 10 s at all settings (e.g., -0.18 ± 0.06 vs 0.12 ± 0.06 at 8 mA, 400 ms). For a pulse-width of 100 ms, the contractile strain continued to increase with increasing pulse-amplitude, while the induced strain was comparable for all pulse-amplitudes when paced with high pulse-width (400 ms). Therefore, pacing is an effective tool in modulating the intensity of segmental contractions.Clinical Relevance- Different pacing parameters can define contraction intensity and frequency in the small intestine. This is of therapeutic potential for treating motility disorders such as post-operative ileus and chronic intestinal pseudo-obstruction.

Systematic review of small intestine pacing parameters for modulation of gut function

BACKGROUND AND PURPOSE

The efficacy of conventional treatments for severe and chronic functional motility disorders remains limited. High-energy pacing is a promising alternative therapy for patients that fail conventional treatment. Pacing primarily regulates gut motility by modulating rhythmic bio-electrical events called slow waves. While the efficacy of this technique has been widely investigated on the stomach, its application in the small intestine is less developed. This systematic review was undertaken to summarize the status of small intestinal pacing and evaluate its efficacy in modulating bowel function through preclinical research studies.

METHODS

The literature was searched using Scopus, PubMed, Ovid, Cochrane, CINAHL, and Google Scholar. Studies investigating electrophysiological, motility, and/or nutrient absorption responses to pacing were included. A critical review of all included studies was conducted comparing study outcomes against experimental protocols.

RESULTS

The inclusion criteria were met by 34 publications. A range of pacing parameters including amplitude, pulse width, pacing direction, and its application to broad regional small intestinal segments were identified and assessed. Out of the 34 studies surveyed, 20/23 studies successfully achieved slow-wave entrainment, 9/11 studies enhanced nutrient absorption and 21/27 studies modulated motility with pacing.

CONCLUSION

Small intestine pacing shows therapeutic potential in treating disorders such as short bowel syndrome and obesity. This systematic review proposes standardized protocols to maximize research outcomes and thereby translate to human studies for clinical validation. The use of novel techniques such as high-resolution electrical, manometric, and optical mapping in future studies will enable a mechanistic understanding of pacing.

Diffused and sustained inhibitory effects of intestinal electrical stimulation on intestinal motility mediated via sympathetic pathway

OBJECTIVE

The aims were to investigate the energy-dose response effect of intestinal electrical stimulation (IES) on small bowel motility, to compare the effect of forward and backward IES, and to explore the possibility of using intermittent IES and mechanism of IES on intestinal motility.

MATERIALS AND METHODS

Five dogs implanted with a duodenal cannula and one pair of intestinal serosal electrodes were studied in five sessions: 1) energy-dose response study; 2) forward IES; 3) backward IES; 4) intermittent IES vs. continuous IES; 5) administration of guanethidine. The contractile activity and tonic pressure of the small intestine were recorded. The duration of sustained effect after turning off IES was manually calculated.

RESULTS

1) IES with long pulse energy dose dependently inhibited contractile activity and tonic pressure of the small intestine (p < 0.001). 2) The duration of sustained inhibitory effect of IES on the small intestine depended on the energy of IES delivered (p < 0.001). 3) The potency of the inhibitory effect was the same between forward and backward IES. 4) The efficacy of intermittent IES was the same as continuous IES in inhibiting motility of the small intestine. 5) Guanethidine blocked the inhibitory effect of IES on intestinal motility.

CONCLUSIONS

IES with long pulses inhibits small intestinal motility; the effect is energy-dose dependent, diffused, and sustained. Intermittent IES has the same efficacy as the continuous IES in inhibiting small intestinal motility. Forward and backward IES have similar inhibitory effects on small bowel motility. This IES-induced inhibitory effect is mediated via the sympathetic pathway.

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.

Esvaziamento gástrico e jejunal proximal em ratos submetidos ou não à gastrectomia parcial com reconstrução do trânsito intestinal em Y de Roux ou a Billroth II

Estudou-se os efeitos da reconstrução gastrojejunal em Y de ROUX (YR) ou a BILLROTH II (BII) no esvaziamento gástrico (EG) e jejunal proximal de líquido nutriente. Constitui-se quatro grupos de dez ratos Wistar machos: simulado (grupo I), antrectomia em YR (grupo II), gastrectomia subtotal em YR (grupo III) e antrectomia a BII (grupo IV). O EG e jejunal proximal foram avaliados no sétimo dia de pós-operatório, 60 minutos após a introdução gástrica de ovo cru mexido marcado com Tc99m. Após esse tempo, retirou-se separadamente o estômago, intestino proximal e restante do intestino, seguindo-se da quantificação do radioisótopo presente em cada segmento, numa câmara de ionização. O EG foi mais rápido nos animais gastrectomizados do que naqueles sem gastrectomia (α < 0,05). O EG no grupo antrectomia em YR foi mais lento do que no grupo gastrectomia subtotal em YR (α < 0,05), mas não apresentou diferença significante com relação ao grupo antrectomia a BII. O esvaziamento da alça de ROUX (grupos TI e III) não mostrou diferença significante em relação ao da alça eferente de igual comprimento (grupo IV). Concluiu-se que o EG de liquido nutriente foi semelhante na antrectomia em YR ou a BII e que nas reconstruções em YR, foi mais rápido na gastrectomia subtotal do que na antrectomia.

Effect of gastric resection, Roux-en-Y diversion and vagotomy on gastric emptying in the rat

Solid and liquid gastric emptying studies were conducted in 61 male Wistar rats. In 20 animals a two-thirds Pólya-type gastric resection was performed and 21 had a similar resection with a 10-cm Roux-en-Y diversion. In nine of the Roux diversions truncal vagotomy was also carried out. Twenty animals acted as controls: ten unoperated and ten that received laparotomy only. Body-weight and gastric emptying were measured weekly for 4 weeks and monthly for 4 months after surgery. Animals subjected to gastrectomy revealed a weight loss of approximately 16 per cent after operation. Weight gain was slower after Roux reconstruction than after Pólya-type anastomosis and slowest in animals with vagotomy and Roux drainage (P < 0.05). Gastric emptying was unchanged in unoperated controls. Animals in which a laparotomy was performed had delayed solid and liquid emptying for the first 4 weeks after operation (P < 0.05). Following Pólya-type gastrectomy, liquid emptying was delayed for 4 months. Solid emptying was unchanged, with no evidence of the delay present in animals with a laparotomy. Animals subjected to Roux-en-Y diversion showed a greater delay in liquid emptying than those with a Pólya resection; solid emptying was also delayed (P < 0.05). Severe gastric retention of liquids and solids occurred in the early postoperative phase when vagotomy was added to the Roux diversion (P < 0.01). Emptying of solids adopted a relatively normal linear pattern after this initial retention. Emptying of liquids, however, remained abnormal, appearing to adopt a biphasic pattern.

Cisapride in treatment of Roux-en-Y syndrome

After Roux-en-Y gastrojejunostomy patients frequently complain of upper abdominal pain, fullness, nausea, and vomiting. This Roux-en-Y syndrome is caused by slow gastric emptying, Roux-limb stasis, or both. Treatment of this syndrome is cumbersome. We evaluated the effect of cisapride on complaints and on transit through gastric remnant and Roux limb in 24 such patients. Thirteen of them had slow gastric emptying and 13 had stasis in the Roux limb (two patients had both). Symptoms and transit were evaluated before and after three weeks of treatment using a questionnaire and scintigraphy. Responding subjects continued therapy and were interviewed again after six months. Seven patients with slow gastric emptying and three patients with Roux-limb stasis had enduring symptomatic relief; all exhibited accelerated transit during therapy: mean half gastric emptying time in the seven patients with slow gastric emptying was 204 +/- 89 min before and 111 +/- 59 min during cisapride (P less than 0.05); mean percentage of radioactivity, emptied from the gastric remnant, which remained in the Roux limb at 60 min in the three patients with Roux limb stasis was 74 +/- 4% before and 25 +/- 10% during cisapride (P less than 0.05). In patients without symptomatic response, transit did not improve.

CONCLUSION

with cisapride long-lasting symptomatic relief and improved transit is achieved in about 40% of patients with the Roux-en-Y syndrome.

Electrical dysrhythmias in the Roux jejunal limb: cause and treatment

Electrical dysrhythmias in the Roux limb after Roux gastrojejunostomy are associated with upper gut stasis of food. The aim of this study was to determine the cause of the dysrhythmias and whether they could be eliminated with pacing. A set of four dogs (Group A) underwent three sequential operations: placement of jejunal electrodes at sites corresponding to the Roux limb; construction of a Roux limb without vagotomy, gastrectomy, or gastrojejunostomy; and transthoracic truncal vagotomy. A second set of five dogs (Group B) underwent truncal vagotomy, distal gastrectomy, and Roux gastrojejunostomy with recording electrodes placed on the Roux limb and a pacing electrode situated at the proximal end of the limb. Electrical recordings were obtained on four separate occasions after each operation. In Group A dogs, orad and disordered propagation of jejunal pacesetter potentials occurred in the Roux limb 56 +/- 5% of the time after limb construction but never before construction. The pattern was not changed with vagotomy. In Group B dogs, electrical dysrhythmias in the Roux limb also occurred and were corrected with electrical pacing. We concluded that electrical dysrhythmias in the canine Roux limb are secondary to the jejunal transection done during Roux limb construction, and are not due to gastrectomy, gastroenterostomy, or vagotomy. The dysrhythmias can be corrected with pacing.

Effect of various prokinetic agents on post Roux-en-Y gastric emptying. Experimental and clinical observations

The effect of various prokinetic drugs was assessed in animals with Roux-en-Y gastrojejunostomy. The agents tested were (1) bethanechol 2.5 mg subcutaneously at 0 min and 30 min postprandially (pp); (2) metoclopramide 20 mg intravenous bolus at 0 min pp; (3) a combination of 1 and 2; (4) oxytocin 5 mg intramuscularly at 0 min and 240 min pp; (5) motilin at 100 ng/kg/hr; or (6) 300 ng/kg/hr continuous intravenous infusion from 0 to 270 min pp. Only bethanechol administration resulted in significantly less gastric retention (65 +/- 6% vs 32 +/- 5% retention at 5 hr). (P less than 0.002). The animal results with parenteral bethanechol were confirmed in humans with chronic delayed gastric emptying following Roux-en-Y gastrojejunostomy, with a decrease in gastric retention on radionuclide scan from 78.5 +/- 5% to 26 +/- 12% at 2 hr pp (P less than 0.01). Initially all patients responded with symptomatic improvement. However, subsequently 3/6 (50%) of patients required total or near total gastrectomy for recurrent symptoms of gastric stasis. Nevertheless, 2/6 (33%) of patients have no further evidence of gastric stasis, and a trial of bethanechol is recommended prior to considering further gastrectomy in patients with the Roux-stasis syndrome.

The effect of increased intracranial pressure (ICP) on gastric motility

This study evaluates the effect of increased intracranial pressure (ICP) on gastric motility. Nine male cats (weight, 4.84 +/- 1.16 kg) were anesthetized with ketamine and underwent laparotomy for placement of bipolar (silver-silver chloride) electrodes on the serosal surface of the gastroesophageal junction (GEJ), antrum, and prepyloric areas of the stomach. At 1 week frontoparietal burr holes were performed with placement of an epidural Fogarty catheter. Migrating myoelectric complexes (MMCs) were evaluated at the GEJ, antrum, and prepyloric areas at varying levels of ICP (baseline and 20, 40, and 60 mm Hg) using balloon inflation. MMCs at the GEJ were triphasic with a period of 4 sec (+/- 1 sec) at baseline levels. At ICP levels above baseline, periodicity and waveforms at the GEJ became irregular. Waveforms became multiphasic with 1- to 2-sec periods and variable amplitudes. In the antral and prepyloric areas, duration and amplitude of the triphasic MMCs was unchanged from baseline. At 60 mm Hg ICP periodicity was significantly altered at both 1 and 2 weeks. MMCs returned to baseline levels with balloon deflation. The data indicate that elevated ICP (to 60 mm Hg) results in consistent and reproducible alterations of MMC periodicity, suggesting that such alterations may influence gastric motility.