Effect of transection and pacing on human jejunal pacesetter potentials

High-energy pacing inhibits slow-wave dysrhythmias in the small intestine

The motility of the gastrointestinal tract is coordinated in part by rhythmic slow waves, and disrupted slow-wave patterns are linked to functional motility disorders. At present, there are no treatment strategies that primarily target slow-wave activity. This study assessed the use of pacing to suppress glucagon-induced slow-wave dysrhythmias in the small intestine. Slow waves in the jejunum were mapped in vivo using a high-resolution surface-contact electrode array in pigs (n = 7). Glucagon was intravenously administered to induce hyperglycemia. Slow-wave propagation patterns were categorized into antegrade, retrograde, collision, pacemaker, and uncoupled activity. Slow-wave characteristics such as period, amplitude, and speed were also quantified. Postglucagon infusion, pacing was applied at 4 mA and 8 mA and the resulting slow waves were quantified spatiotemporally. Antegrade propagation was dominant throughout all stages with a prevalence of 55 ± 38% at baseline. However, glucagon infusion resulted in a substantial and significant increase in uncoupled slow waves from 10 ± 8% to 30 ± 12% (P = 0.004) without significantly altering the prevalence of other slow-wave patterns. Slow-wave frequency, amplitude, and speed remained unchanged. Pacing, particularly at 8 mA, significantly suppressed dysrhythmic slow-wave patterns and achieved more effective spatial entrainment (85%) compared with 4 mA (46%, P = 0.039). This study defined the effect of glucagon on jejunal slow waves and identified uncoupling as a key dysrhythmia signature. Pacing effectively entrained rhythmic activity and suppressed dysrhythmias, highlighting the potential of pacing for gastrointestinal disorders associated with slow-wave abnormalities.NEW & NOTEWORTHY Glucagon was infused in pigs to induce hyperglycemia and the resulting slow-wave response in the intact jejunum was defined in high resolution for the first time. Subsequently, with pacing, the glucagon-induced dysrhythmias were suppressed and spatially entrained for the first time with a success rate of 85%. The ability to suppress slow-wave dysrhythmias through pacing is promising in treating motility disorders that are associated with intestinal dysrhythmias.

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.

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.

Functional reentry and circus movement arrhythmias in the small intestine of normal and diabetic rats

In a few recent studies, the presence of arrhythmias based on reentry and circus movement of the slow wave have been shown to occur in normal and diseased stomachs. To date, however, reentry has not been demonstrated before in any other part of the gastrointestinal system. No animals had to be killed for this study. Use was made of materials obtained during the course of another study in which 11 rats were treated with streptozotocin and housed with age-matched controls. After 3 and 7 mo, segments of duodenum, jejunum, and ileum were isolated and positioned in a tissue bath. Slow wave propagation was recorded with 121 extracellular electrodes. After the experiment, the propagation of the slow waves was reconstructed. In 10 of a total of 66 intestinal segments (15%), a circus movement of the slow wave was detected. These reentries were seen in control (n = 2) as well as in 3-mo (n = 2) and 7-mo (n = 6) diabetic rats. Local conduction velocities and beat-to-beat intervals during the reentries were measured (0.42 ± 0.15 and 3.03 ± 0.67 cm/s, respectively) leading to a wavelength of 1.3 ± 0.5 cm and a circuit diameter of 4.1 ± 1.5 mm. This is the first demonstration of a reentrant arrhythmia in the small intestine of control and diabetic rats. Calculations of the size of the circuits indicate that they are small enough to fit inside the intestinal wall. Extrapolation based on measured velocities and rates indicate that reentrant arrhythmias are also possible in the distal small intestine of larger animals including humans.

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.

Roles of interstitial cells of Cajal in regulating gastrointestinal motility: in vitro versus in vivo studies

The aim of this article is to provide a better understanding of the roles of interstitial cells of Cajal (ICC) in regulating gastrointestinal motility by reviewing in vitro and in vivo physiological motility studies. Based on the in vitro studies, ICC are proposed to have the following functions: to generate slow waves, to mediate neurotransmission between the enteric nerves and the gastrointestinal muscles and to act as mechanoreceptors. However, there is limited evidence available for these hypotheses from the in vivo motility studies. In this review, we first introduce the major subtypes of ICC and their established functions. Three Kit mutant mouse and rodent models are presented and the loss of ICC subtypes in these mutants is reviewed. The physiological motility findings from various in vitroand in vivo experiments are discussed to give a critical review on the roles of ICC in generating slow waves, regulating gastrointestinal motility, mediating neural transmission and serving as mechanoreceptors. It is concluded that the role of ICC as pacemakers may be well established, but other cells may also be involved in the generation of slow waves; the theory that ICC are mediators of neurotransmission is challenged by the majority of the in vivo motility studies; the hypothesis that ICC are mechanoreceptors has not found supportive evidence from the in vivo studies yet. More studies are needed to explain discrepancies in motility findings between the in vitro and in vivo experiments.

Roles of interstitial cells of Cajal in regulating gastrointestinal motility: in vitro versus in vivo studies

The aim of this article is to provide a better understanding of the roles of interstitial cells of Cajal (ICC) in regulating gastrointestinal motility by reviewing in vitro and in vivo physiological motility studies. Based on the in vitro studies, ICC are proposed to have the following functions: to generate slow waves, to mediate neurotransmission between the enteric nerves and the gastrointestinal muscles and to act as mechanoreceptors. However, there is limited evidence available for these hypotheses from the in vivo motility studies. In this review, we first introduce the major subtypes of ICC and their established functions. Three Kit mutant mouse and rodent models are presented and the loss of ICC subtypes in these mutants is reviewed. The physiological motility findings from various in vitro and in vivo experiments are discussed to give a critical review on the roles of ICC in generating slow waves, regulating gastrointestinal motility, mediating neural transmission and serving as mechanoreceptors. It is concluded that the role of ICC as pacemakers may be well established, but other cells may also be involved in the generation of slow waves; the theory that ICC are mediators of neurotransmission is challenged by the majority of the in vivo motility studies; the hypothesis that ICC are mechanoreceptors has not found supportive evidence from the in vivo studies yet. More studies are needed to explain discrepancies in motility findings between the in vitro and in vivo experiments.

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.

Systematic review: applications and future of gastric electrical stimulation

BACKGROUND

Over the past 20 years, gastric electrical stimulation has received increasing attention among researchers and clinicians.

AIM

To give a systematic review on the effects, mechanisms and applications of gastric electrical stimulation.

METHODS

Medline was used to identify the articles to be included in this review. Key words used for the search included gastric electrical stimulation, gastric pacing, electrical stimulation, stomach, gastrointestinal motility, central nervous system, gastroparesis, nausea and vomiting; obesity and weight loss. Combinational uses of these keywords were made to identify relevant articles. Most of the articles included in this review ranged from 1985 to 2006.

RESULTS

Based on the general search, the review was structured as follows: (i) peripheral and central effects and mechanisms of gastric electrical stimulation; (ii) clinical applications of gastric electrical stimulation for gastroparesis and obesity and (iii) future development of gastric electrical stimulation.

CONCLUSIONS

Great progress has been made during the past decades. Gastric electrical stimulation has been shown to be effective in normalizing gastric dysrhythmia, accelerating gastric emptying and improving nausea and vomiting. Implantable device has been made available for treating gastroparesis as well as obesity. However, development of a new device and controlled clinical studies are required to further prove clinical efficacy of gastric electrical stimulation.

Efficacy and efficiency of gastric electrical stimulation with short pulses in the treatment of vasopressin-induced emetic responses in dogs

The aim of this study was to determine the most effective and efficient anti-emetic parameters of short-pulse gastric electrical stimulation (GES) in dogs. Seven female beagle dogs implanted with four pairs of gastric electrodes were studied in eight randomized sessions (saline, vasopressin, and six GES sessions with different parameters). Each session consisted of four 20-min recordings of gastric slow waves and symptoms. In sessions 1 and 2, saline and vasopressin, respectively, were infused during the second 20-min period. The protocol of the other six sessions was the same as session 2 except that GES was continuously applied. It was found that: (1) vasopressin induced gastric dysrhythmia and emetic response (P < 0.01, anova); (2) short-pulse GES with a frequency of 14 or 40 Hz and pulse width of 0.1 or 0.3 ms, but not 0.6 ms was able to reduce symptoms induced by vasopressin; (3) short-pulse GES with a pulse width of 0.3 ms was the most effective in preventing vasopressin-induced symptoms; (4) none of the tested GES methods improved vasopressin-induced gastric dysrhythmia. We conclude that vasopressin induces gastric dysrhythmia and symptoms. Short-pulse GES with a pulse width of 0.3 ms and frequency of 14 Hz is most effective and efficient in preventing vasopressin-induced emetic responses in dogs.

Comparison of hepaticoantrostomy and hepaticojejunostomy for biliary reconstruction after resection of a choledochal cyst

Twelve infants operated upon for choledochal cyst (CC) are reviewed with emphasis on the operative technique of biliary tract reconstruction, incidence of cholangitis, postoperative hypergastrinemia, biliary excretion, and upper gastrointestinal (GI) motility in a follow-up of 24 to 35 months. In 7 patients biliary reconstruction was performed with a Roux-en-Y hepaticojejunostomy (HJ), and in 5 with a hepaticoantrostomy (HAST). In the HJ group 4 patients had recurrent episodes of cholangitis and intermittent diarrhea and serum gastrin levels were significantly elevated in 5. Hepatobiliary scintigraphy showed unobstructed excretion of labelled bile through bile ducts into the Roux-en-Y loop, but with significantly delayed emptying of bile into the distal jejunum in all patients. Gastric emptying and upper intestinal passage were normal. In the HAST group no episode of cholangitis occurred and serum gastrin levels were within the normal range. Scintigraphically, hepatobiliary excretion, and duodenojejunal passage of labelled bile was normal, except in 1 patient who developed a postoperative stenosis of the left hepatic duct. Upper GI contrast studies demonstrated normal gastric emptying without reflux into the biliary system. These results suggest that biliary reconstruction with HAST can be performed safely with a low incidence of complications HAST offers a more physiologic method of biliary reconstruction after resection of a CC that allows bile to drain directly into the duodenum.

Magnetoenterography (MENG): noninvasive measurement of bioelectric activity in human small intestine

The basic electrical rhythm (BER) of the gastrointestinal tract creates minute magnetic fields that have been measured in animals using a Superconducting QUantum Interference Device (SQUID) gradiometer. The aim of this study was to measure noninvasively the biomagnetic fields of human stomach and small intestine. Twenty-one human volunteers were studied using a 37-channel SQUID gradiometer positioned over the epigastrium and umbilicus. In one volunteer additional biomagnetic recordings were performed in order to map the spatial variation of the biomagnetic fields. Cyclical waveforms consistent with gastric BER [3.0+/-0.5 cycles per minute (cpm)] and small intestine BER (10.26+/-1.74 cpm) were seen in the epigastrium and umbilicus, respectively. The mapping study identified the expected frequency gradient (12.0 cpm in duodenum, 11.3 cpm in jejunum, to 9.7 cpm in ileum) within the small intestine. Noninvasive recordings of human gastric and small intestinal BER can be obtained using a SQUID gradiometer.

The involvement of muscarinic receptors in gastric liquid emptying in the conscious rat following Roux-en-Y-antrectomy

The gastric emptying of liquid test meals is dependent on resistance to flow at the pylorus and on pressure gradients between the duodenum and the body of the stomach. In the present study, we investigated the role and subtypes of muscarinic receptors during gastric emptying of various liquid test meals in conscious rats with gastric fistula after Roux-en-Y antrectomy. In the control rats with gastric fistula but with intact reflex pathways and pylorus, the non-selective muscarinic antagonist atropine (7 mg/kg i.p.) and M1-selective pirenzepine (7 mg/kg i.p.), acting possibly on M1 receptors, delayed saline emptying by suppressing cholinergic tone and thus relaxing the body of the stomach and contracting the pyloric sphincter. On the other hand, in Roux-rats saline and hyperosmolal saline emptying were not significantly affected, while the inhibitory effect of HCl was completely reversed. Furthermore, peptone-induced delay of gastric emptying in control rats was also reduced in Roux-rats. Pirenzepine abolished the facilitating effects of Roux-en-Y operation on acid and peptone emptying and M2-selective antagonist AF DX-116 (7 mg/kg i.p.) did not have any inhibitory effect in this regard. In conclusion, Roux-en-Y gastrectomy without vagotomy does not slow gastric emptying of liquids, and it reverses the inhibitory effects of peptone and acid through an atropine- and pirenzepine-sensitive pathway.

Diagnosing intestinal ischemia using a noncontact superconducting quantum interference device

Intestinal ischemia is associated with changes of the basic electric rhythm (BER) of the small intestine. We hypothesized that these changes can be measured noninvasively using a superconducting quantum interference device (SQUID). After general anesthesia, a laparotomy was performed on 10 animals and the jejunum was placed in a nonmagnetic recording chamber containing Krebs' solution at 38 degrees C. Five animals had electrodes placed while five others were placed under the SQUID. Injection of thrombin into the mesenteric artery decreased blood flow (measured with a laser doppler flow-meter) 95% within 5 minutes. SQUID measurements showed significant decreases (P < 0.01 for all changes) in the frequency (15.5 +/- 0.3 to 8.9 +/- 0.2 cycles/min) and the propagation velocity of slow waves (3.5 +/- 0.2 to 1.9 +/- 0.3 sec). The changes in intestinal biomagnetic activity after ischemia were similar to the changes in electrical activity. The SQUID magnetometer is a reliable noncontact device that can detect early intestinal ischemia in animal models. We have recently recorded human small bowel biomagnetic activity using a SQUID magnetometer and believe further technical developments will permit the noninvasive diagnosis of mesenteric ischemia.

Gastric motor physiology and pathophysiology

The stomach has two distinct physiologic motor areas: the proximal stomach and the distal stomach. The proximal stomach, with its slow, sustained contractions, has a key role in regulating intragastric pressure and gastric emptying of liquids, while the distal stomach, with its peristaltic contractions, has a major role in mixing, trituration, and emptying of solids. Diseases and operations that disturb the motility of these two areas can result in unique adverse motor sequelae. For example, operations that impair proximal gastric motility, such as proximal gastric resection, may cause rapid gastric emptying of liquids and subsequent dumping and diarrhea. In contrast, operations that impair distal gastric contractions, such as truncal vagotomy, may cause slow gastric emptying of solids and chronic gastric atony. Knowledge of the physiology of the stomach in health and of the pathophysiology with disease and after operation provides a basis for the successful treatment and prevention of these disorders.

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.

Relation between slow-wave frequency and spiking activity during the migrating myoelectric complex in dogs

The quantitative relation between slow-wave periods and spiking activity was evaluated in vivo in canine small intestine during the fasted state. Experiments were performed in three conscious dogs with three bipolar electrodes, implanted respectively 10, 25 and 40 cm beyond the ligament of Treitz. Digitized electrical recordings were automatically processed for the individual slow-wave periods and spike-burst intensities using a set of computer programs developed in our laboratory. A linear correlation existed between the degree of spiking activity and the average length of the preceding slow-wave period. The slopes of the regression lines were less steep for more distal electrodes. A second series of experiments showed that an increase in the slow-wave period precedes the onset of phase 3 of the migrating myoelectric complex and that a fall in slow-wave period precedes the end of phase 3. These data show that a low slow-wave frequency is accompanied by a facilitation of spiking activity, whereas shortening of the slow-wave period is accompanied by a decrease in spike burst intensity. This relation between slow-wave period and spiking activity shows an aboral trend that may be related to intrinsic slow-wave frequency.

Postgastrectomy syndromes

Anatomic and physiological changes introduced by gastric surgery result in postgastrectomy syndromes in approximately 20% of patients. Most of these disorders are caused by operation-induced abnormalities in the motor functions of the stomach, including disturbances in the gastric reservoir function, the mechanical-digestive function, and the transporting function. Division of the vagal innervation to the stomach and ablation or bypass of the pylorus are the most significant factors contributing to postgastrectomy syndromes. Either rapid or slow emptying may result, depending on the relative importance of lack of a compliant gastric reservoir, loss of an effective contractile force, and loss of controlling factors that slow or speed gastric emptying and result in duodenal-gastric reflux. Clearly defining which syndrome is present in a given patient is critical to developing a rational treatment plan. In syndromes with slow gastric emptying, bilious vomiting, or alkaline reflux gastritis, the use of endoscopy is essential to rule out mechanical causes of the syndrome. Contrast radiography and scintigraphic gastric emptying studies are useful to document rapid or delayed gastric emptying. Postgastrectomy syndromes often abate with time. Conservative measures, including medical, dietary, and behavioral therapy, should be given at least a 1-year trial. If these nonoperative measures fail, surgical therapy is recommended. The Roux-en-Y gastrojejunostomy is useful for patients with dumping, because it slows gastric emptying and the transit of chyme through the Roux limb. The same operation helps patients with alkaline reflux gastritis, because it diverts pancreaticobiliary secretions away from the gastric remnant. Near-total gastrectomy, which reduces the size of a flaccid gastric reservoir, can be used to treat delayed gastric emptying. This operation should be combined with the Roux procedure to prevent postoperative reflux gastritis and esophagitis. Newer techniques, such as gastrointestinal pacing and the uncut Roux operation, may improve the treatment of the postgastrectomy syndromes in the future.

Gastric emptying and myoelectric activity following Roux-en-Y gastrojejunostomy

The purpose of this study was to compare gastric emptying and Roux myoelectric activity in a canine model. Four dogs underwent truncal vagotomy, antrectomy, and 40 cm Roux-en-Y gastrojejunostomy, with placement of serosal electrodes. Following recovery, gastric emptying was determined scintigraphically with a radiolabeled solid meal, and fasting and fed small-bowel myoelectric activity was obtained. Gastric emptying was markedly slowed compared to control unoperated animals (202 +/- 91 versus 46 +/- 12 min; P less than 0.05). Slow wave frequency declined in the Roux limb compared to the duodenum (14.2 +/- 0.4 versus 18.0 +/- .06 counts per minute; P less than 0.01). No gradient in slow wave frequency was observed in the Roux limb, although one animal was noted to have reversed propagation of slow waves in the proximal Roux limb. Migrating myoelectric complexes (MMCs) were coordinated between the Roux limb and jejunum distal to the enteroenterostomy, but not with the duodenum. Periodicity of the MMCs was different in the Roux limb and duodenum (98.6 +/- 6.3 versus 138 +/- 17.5 min; P less than 0.05). None of the animals converted to the fed myoelectric pattern with a 272 kcal meal (MMC periodicity in the Roux limb = 99 +/- 10 min postprandially, P = N.S.). These quantitative and qualitative alterations in myoelectric activity may contribute to the observed delay in gastric emptying following Roux-en-Y gastrojejunostomy.

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.

Postoperative ileus

Postoperative ileus follows any operation. Although worsened if the peritoneum is entered, the length and duration of surgery does not influence the severity of postoperative ileus. Inhibitory alpha 2-adrenergic reflexes with peptidergic afferents contribute to postoperative ileus. Clinically, treatment of ileus centers around symptomatic relief with nasogastric suction. Trials of adrenergic blockade combined with cholinergic stimulation have met with limited success. Prokinetic drugs have not been proved effective in the treatment of this disorder. Two types of ileus exist: postoperative and paralytic. Postoperative ileus resolves spontaneously after two to three days, and probably reflects inhibition of colonic motility. Paralytic ileus is more severe, last more than three days, and seems to represent inhibition of small bowel activity. No discrete structural changes cause postoperative ileus and the role of peptidergic neuronal systems of the enteric nervous system has not been elucidated. Possible central or humoral mechanisms have not been studied extensively. The possible direct inhibition of enteric or spinal nerves by anesthetic agents not cleared from these tissues remains to be studied. Also in need of study is the potential alteration of neurotransmitter receptor activity within the enteric nervous plexus after manipulation of the bowel.

Chronic intestinal pseudo-obstruction: diagnosis and treatment

Chronic intestinal pseudo-obstruction is a rare syndrome characterized by recurrent episodes of small bowel obstruction without evidence of a structural obstructing lesion. The two pathophysiologic types of this motility disorder are myopathic and neuropathic. The latter may affect extrinsic or intrinsic neural control of gut motility. Diagnosis is based on (1) recognition of the clinical syndrome and exclusion of mechanical obstruction by endoscopy, radiologic studies, or laparotomy and (2) manometric studies of the stomach and small bowel. Full-thickness biopsy specimens for histologic analysis may not be essential for the diagnosis in the future. The goals of treatment are the restoration of normal gut peristalsis and the correction of nutritional deficiencies. Prokinetic medications, surgical excision in cases of localized disease, and parenteral nutrition are frequently necessary. Management is difficult because of the lack of efficacious medications, extension of the disease to other regions, and complications of central parenteral nutrition. Prokinetic agents, venting enterostomies for relief of symptoms, and enteral supplementation are being evaluated in this intractable and serious condition.

Total gastrectomy for benign disease

Among 37 patients who underwent total gastrectomy for nonmalignant disease, operative mortality was 4 per cent after 27 elective operations and 10 per cent after 10 emergency operations. Three other patients died 1 to 6 months after operation. Major postoperative complications occurred in 24 per cent. Long-term follow-up of 26 patients (81 per cent of survivors) after a mean +/- SEM of 8.4 +/- 1.1 years showed that 73 per cent of patients had no or only occasional, easily controlled, mild abdominal symptoms and good enough health to enable them to work or carry out normal activities for their age. The patients lost a mean of 15 per cent of their body weight, however, and about one third of them had weakness and diarrhea. A quarter of them had anemia despite iron and vitamin B12 therapy. Our conclusion was that total gastrectomy is a reasonable operation for benign diseases. Nonetheless, in view of the substantial postoperative mortality and morbidity, the operation should be used only when less extensive operations will not suffice.