Effect of atropine on the frequency of reflux and transient lower esophageal sphincter relaxation in normal subjects

Recovery of lower oesophageal barrier function: a pilot study comparing a mixture of atropine and neostigmine and sugammadex: A randomised controlled pilot study

BACKGROUND

The lower oesophageal sphincter (LOS) barrier serves to prevent regurgitation of gastric contents. Although general anaesthesia depresses its function, its recovery process during emergence from anaesthesia has not been systematically examined.

OBJECTIVE

To explore whether recovery of lower oesophageal barrier function differed between patients receiving a mixture of 1 mg atropine and 2 mg neostigmine and those receiving 2 mg kg-1 sugammadex during emergence from anaesthesia.

DESIGN

An unblinded randomised controlled pilot study.

SETTING

A single university hospital from January 2016 to December 2018.

PATIENTS

A total of 20 non-obese adult females undergoing minor surgery.

INTERVENTION

The patients were randomly assigned to a group either receiving atropine and neostigmine or sugammadex for reversal of rocuronium.

MAIN OUTCOME MEASURES

Through use of the high-resolution manometry technique, the lower oesophageal barrier pressure (PBAR: primary variable) defined as a pressure difference between pressures at the LOS and the stomach was measured at five distinguishable time points during emergence from total intravenous anaesthesia. A mixed effects model for repeated measures was used to test the hypothesis.

RESULTS

In all patients baseline PBAR values were positive even under muscle paralysis and general anaesthesia before administration of reversal agents, and did not differ between the groups (P = 0.299). During recovery from muscle paralysis and general anaesthesia, PBAR (mean ± SD) significantly increased (P = 0.004) from 17.0 ± 2.9 to 21.0 ± 5.0 mmHg in the atropine and neostigmine group (n = 8) and from 19.1 ± 9.0 to 24.5 ± 12.7 mmHg in the sugammadex group (n = 11). PBAR significantly increased immediately after return of consciousness in both groups, whereas return of muscle tone, lightening of anaesthesia and tracheal extubation did not change it.

CONCLUSION

Recovery of the lower oesophageal barrier function does not differ between patients receiving either atropine and neostigmine or sugammadex and is completed after recovery of consciousness from general anaesthesia.

TRIAL REGISTRATION

UMIN Clinical Trials Registry: UMIN000020500: https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr.cgi?function=brows&action=brows&recptno=R000023594&type=summary&language=E.

Repetitive Antegrade Contractions: A novel response to sustained esophageal distension is modulated by cholinergic influence

BACKGROUND & AIMS

A unique motor response to sustained esophageal distension, repetitive antegrade contractions (RACs), is observed using functional luminal imaging probe (FLIP) panometry. However, physiologic mechanisms related to this response are unexplored. This study aimed to evaluate the impact of cholinergic inhibition with atropine on the esophageal contractile response to sustained distention, including RACs, among healthy volunteers.

METHODS

8 asymptomatic volunteers (ages 22-45) were evaluated in a crossover study design with 16-cm FLIP positioned across the esophagogastric junction and distal esophagus during sedated upper endoscopy. The FLIP study involving stepwise volumetric distension was performed twice in each subject, at baseline and again after atropine (15 mcg/kg) was administered intravenously. FLIP panometry was analyzed to assess the contractile response to distension.

RESULTS

Antegrade contractions, lumen-occluding contractions, and a RAC pattern were observed in 8/8, 8/8, and 7/8(88%) subjects, respectively, at baseline and in 5/8 (63%), 2/8 (25%) and 2/8 (25%) subjects after atropine. The rate of contractions in the RAC pattern was similar (6-7 contractions per minute) before and after atropine. Compared with the baseline study, distension-induced contractility was triggered at higher fill volumes after atropine. FLIP pressures were lower in response to volumetric filling after atropine than at baseline.

CONCLUSIONS

The vigor and triggering of the esophageal contractile response to distension is reduced by cholinergic inhibition in asymptomatic controls. The observation that the rate of contractions did not change when patients developed repetitive contractile responses suggests that this rate is not modified by cholinergic inhibition once contractility is triggered.

Association between Reflux Esophagitis Incidence and Palmar Hyperhidrosis

The autonomic dysfunction in palmar hyperhidrosis (PH) includes not only sympathetic overactivity but also parasympathetic impairment. A decrease of parasympathetic tone has been noted in gastroesophageal reflux disease of neonates and adults. Patients with reflux esophagitis have a defective anti-reflux barrier. The association between reflux esophagitis and PH is deliberated in this article. The National Health Insurance Database in Taiwan was used. At first-time visits, PH patients were identified by the International Classification of Disease, 9th Revision, Clinical Modification disease code of 780.8 without endoscopic thoracic sympathectomy. Patients were matched by age and gender as control groups. The reflux esophagitis incidence was assessed using disease codes 530.11, 530.81, and 530.85. The factors related to reflux esophagitis were established by the Cox proportional regression model. The risk of reflux esophagitis in PH patients had a hazard ratio of 3.457 (95% confidence interval: 3.043-3.928) after adjustment of the other factors. We confirmed the association between reflux esophagitis and PH. Health care providers must be alerted to this relationship and other risk factors of reflux esophagitis to support suitable treatments to improve the quality of life of patients.

Popular Remedies for Esophageal Symptoms: a Critical Appraisal

PURPOSE OF REVIEW

Popular remedies are of ongoing interest to patients experiencing common esophageal symptoms, particularly as typical pharmacologic interventions have been subject to increased scrutiny. Herein we summarize the available data regarding potential risks and benefits of several such remedies.

RECENT FINDINGS

With emphasis on reflux and non-cardiac chest pain, research is ongoing into the clinical utility and diverse physiologic mechanisms underlying a variety of complementary and alternative modalities, including dietary manipulation, apple cider vinegar, melatonin, acupuncture, and various herbal products (rikkunshito, STW 5, slippery elm, licorice, and peppermint oil, among others). A substantial gap persists between anecdotal and empirical understandings of the majority of non-pharmacologic remedies for esophageal symptoms. This landscape of popular treatments nevertheless raises several interesting mechanistic hypotheses and compelling opportunities for future research.

Survey of findings in patients having persistent heartburn on proton pump inhibitor therapy

In patients with refractory heartburn while on proton pump inhibitor (PPI) therapy, changing drugs or increasing treatment to a twice a day (b.i.d.) dose has become a common practice. This study aims to study patients with persistent heartburn while on PPI therapy and to determine if persistent symptom indicates the need for more aggressive or different therapy. A retrospective review of impedance-pH tracings on PPI therapy (q.d. or b.i.d.) for patients with persistent heartburn was performed. DeMeester score, impedance, and symptom sensitive index (SSI) were used as indices. Statistical analyses were performed using chi-squared test with Yates correction and paired t-test. One hundred consecutive patients, (female 50%, male 50%, mean age 54 [range 16-83] years) were studied on q.d. (n = 45) or b.i.d. PPI (n = 55). Only 20% of the patients had abnormal DeMeester score; 41% had an abnormal impedance score and 56% had abnormal SSI; 29% had all indices normal. There was no difference between patients taking q.d. versus b.i.d. PPI for abnormal DeMeester score (22 vs. 18%), impedance (38 vs. 44%) and SSI (53 vs. 58%); P = 0.80, 0.69, and 0.77, respectively. In 56 patients with positive SSI, symptoms were due to acid reflux in 8 (14%) patients, nonacid reflux in 31 (55%) patients, and combined acid and nonacid reflux in 17 (30%) patients. Patients with persistent heartburn on PPI therapy show a variety of disorders: (i) acid reflux (20%); (ii) nonacid reflux (26%); (iii) positive SSI (56%); (iv) all normal indices (29%). These studies indicate that persistent heartburn on PPI therapy is a complex problem that may not respond to simply increasing acid inhibition.

Treatment of GORD: Three decades of progress and disappointments

The treatment of GORD has been revolutionized by the introduction, in the 1980s, of proton-pump inhibitors as the mainstay of medical therapy and by the development of laparoscopic antireflux surgery which has definitively replaced open surgery. However, despite these major advances, many unmet therapeutic needs still persist and justify novel therapeutic approaches. The aim of this historical review is to recall the main discoveries in the treatment of GORD that have occurred during the last three decades and to discuss why some initially promising drugs or techniques have not translated into clinical applications. A careful analysis of these previous disappointing experiences should help to identify high priorities and better research programmes on the management of GORD.

Involvement of autonomic nervous activity changes in gastroesophageal reflux in neonates during sleep and wakefulness

BACKGROUND

It has been suggested that disturbed activity of the autonomic nervous system is one of the factors involved in gastroesophageal reflux (GER) in adults. We sought to establish whether transient ANS dysfunction (as assessed by heart rate variability) is associated with the occurrence of GER events in neonates during sleep and wakefulness.

METHODS

Nineteen neonates with suspected GER underwent simultaneous, synchronized 12-hour polysomnography and esophageal multichannel impedance-pH monitoring. We compared changes in HRV parameters during three types of periods (control and prior to and during reflux) with respect to the vigilance state.

RESULTS

The vigilance state influenced the distribution of GER events (P<0.001), with 53.4% observed during wakefulness, 37.6% observed during active sleep and only 9% observed during quiet sleep. A significant increase in the sympathovagal ratio (+32%, P=0.013) was observed in the period immediately prior to reflux (due to a 15% reduction in parasympathetic activity (P=0.017)), relative to the control period. This phenomenon was observed during both wakefulness and active sleep.

CONCLUSION

Our results showed that GER events were preceded by a vigilance-state-independent decrease in parasympathetic tone. This suggests that a pre-reflux change in ANS activity is one of the factors contributing to the mechanism of reflux in neonates.

[Updated guidelines 2012 for gastroesophageal reflux disease]

In 2010, a Korean guideline for the management of gastroesophageal reflux disease (GERD) was made by the Korean Society of Neurogastroenterology and Motility, in which the definition and diagnosis of GERD were not included. The aim of this guideline was to update the clinical approach to the diagnosis and management of GERD in adult patients. This guideline was developed by the adaptation process of the ADAPTE framework. Twelve guidelines were retrieved from initial queries through the Appraisal of Guidelines for Research & Evaluation II process. Twenty-seven statements were made as a draft and revised by modified Delphi method. Finally, 24 consensus statements for the definition (n=4), diagnosis (n=7) and management (n=13) of GERD were developed. Multidisciplinary experts participated in the development of the guideline, and the external review of the guideline was conducted at the finalization phase.

Characterization of the distal esophagus high-pressure zone with manometry, ultrasound and micro-computed tomography

BACKGROUND

We sought to determine how the individual components of the distal esophagus and proximal stomach form the gastroesophageal junction high-pressure zone (GEJHPZ) antireflux barrier.

METHODS

An endoscopic ultrasound/manometry catheter was pulled through the proximal stomach and distal esophagus in 20 normal subjects. The axial length and width of individual structures on endoscopic ultrasound were measured. The anatomic orientation of gastroesophageal junction (GEJ) components was examined in two organ donor specimens using micro-computed tomography (micro-CT).

KEY RESULTS

The three distinct structures identified within the GEJHPZ, from distal to proximal, were as follows: the gastric clasp and sling muscle fiber complex, crural diaphragm, and lower esophageal circular smooth muscle fibers (LEC). The LEC was statistically significantly thicker than adjacent esophageal muscles. These structures were associated with three pressure peaks. The pressure peak produced by the clasp/sling fiber complex often overlapped with the pressure peak from the crural diaphragm. The most proximal peak, associated with the LEC, was significantly greater and bimodal in nine of 20 subjects. This bimodal LEC pressure peak correlated with two areas of thickened muscle observed with ultrasound. Micro-CT of GEJ from organ donors confirmed the two areas of thickened muscle.

CONCLUSIONS & INFERENCES

Three distinct anatomic structures, the clasp and sling muscle fibers, crural diaphragm, and LEC combine to form the antireflux barrier of the proximal stomach and distal esophagus. The clasp and sling muscle fibers combine with the crural diaphragm to form a distal pressure profile. The more proximal LEC has a bimodal pressure profile in some patients.

Physiology of the LES

The purpose of this review is to consider the neuromuscular mechanism of LES contractility both by itself and in relation to the esophagogastric junction (EGJ) complex in order to appreciate the intricacies of EGJ valvular function.

[Guidelines for the treatment of gastroesophageal reflux disease]

Gastroesophageal reflux disease (GERD) is defined as a condition that develops when the reflux of stomach contents causes troublesome symptoms and/or complications. In the last decade, GERD has been increasing in Korea. Seventeen consensus statements for the treatment of GERD were developed using the modified Delphi approach. Acid suppression treatments, such as proton pump inhibitors (PPIs), histmine-2 receptor antagonists and antacids are effective in the control of GERD-related symptoms. Among them, PPIs are the most effective medication. Standard dose PPI is recommended as the initial treatment of erosive esophagitis (for 8 weeks) and non-erosive reflux disease (at least for 4 weeks). Long-term continuous PPI or on-demand therapy is required for the majority of GERD patients after the initial treatment. Anti-reflux surgery can be considered in well selected patients. Prokinetic agents and mucosal protective drugs have limited roles. Twice daily PPI therapy can be tried to control extra-esophageal symptoms of GERD. For symptomatic patients with Barrett's esophagus, long-term treatment with PPI is required. Further studies are strongly needed to develop better treatment strategies for Korean patients with GERD.

A missing sphincteric component of the gastro-oesophageal junction in patients with GORD

It was recently shown that the tonic pressure contribution to the high-pressure zone of the oesophago-gastric segment (OGS) contains the contributions from three distinct components, two of which are smooth muscle intrinsic sphincter components, a proximal and a distal component [J Physiol 2007; 580.3: 961]. The aim of this study was to compare the pressure contributions from the three sphincteric components in normal subjects with those in gastro-oesophageal reflux disease (GORD) patients. A simultaneous endoluminal ultrasound and manometry catheter was pulled through the OGS in 15 healthy volunteers and seven patients with symptomatic GORD, before and after administration of atropine. Pre-atropine (complete muscle tone), postatropine (non-muscarinic muscle tone plus residual muscarinic tone) and subtracted (pure muscarinic muscle tone) pressure contributions to the sphincter were averaged after referencing spatially to the right crural diaphragm and the pull-through start position. In the normal group, the atropine-resistant and atropine-attenuated pressures identified the crural and two smooth muscle sphincteric components respectively. The subtraction pressure curve contained proximal and distal peaks. The proximal component moved with the crural sling between full inspiration and full expiration and the distal component coincided with the gastric sling-clasp fibre muscle complex. The subtraction curve in the GORD patients contained only a single pressure peak that moved with the crural sphincter, while the distal pressure peak of the intrinsic muscle component, which was previously recognized in the normal subjects, was absent. We hypothesize that the distal muscarinic smooth muscle pressure component (gastric sling/clasp muscle fibre component) is defective in GORD patients.

Age and gender affect likely manometric diagnosis: Audit of a tertiary referral hospital clinical esophageal manometry service

BACKGROUND AND AIM

Awareness of patient demographics, common diagnoses and associations between these may improve the use and interpretation of manometric investigations. The aim of the present study therefore was to determine whether age and/or gender affect manometric diagnosis in a clinical motility service.

METHODS

An audit of all 452 clinical manometry reports issued from December 2003 to July 2005 with respect to age, gender and diagnosis was carried out. Patients were divided by age (17-24 years n = 14, 25-44 years n = 87, 45-64 years n = 216 and >or=65 years n = 135), and gender and data compared using contingency tables.

RESULTS

Women were more commonly referred overall (59%) and in each age bracket except <25 years (64% male). Men were more likely to have 'hypotensive' motor problems P = 0.01. With aging, normal motor function became less common (P = 0.013), with non-specific motor disorder, ineffective/hypotensive peristalsis and 'achalasia-like' conditions each more common (individual P = NS). Increasing age showed a trend for increased spastic motor disorders (P = 0.06). Gender did not, however, influence whether motility was abnormal (P = 0.5), spastic (P = 0.7) or whether a non-specific motor disorder was present (P = 0.1). In the total cohort, the principal manometric diagnoses were: non-specific motor disorder 33%, normal motility 29%, low basal lower esophageal sphincter pressure 18%, hypotensive/ineffective peristalsis 10%, achalasia/achalasia-like 6%, diffuse esophageal spasm 3% and other 1%.

CONCLUSIONS

Aging leads to increasing esophageal motor abnormalities. Men and women have similar rates of dysfunction, although 'low-pressure problems' were more common in men.

Effect of baclofen on oesophageal motility and transient lower oesophageal sphincter relaxations in GORD patients: a 48-h manometric study

Little is known about prolonged effect of baclofen on oesophageal and lower oesophageal sphincter (LOS) motility. We aimed at investigating the oesophageal motility in gastro-oesophageal reflux disease (GORD) patients 24 h before and after the administration of multiple doses of baclofen. Twenty-one GORD patients underwent a 48-h manometry recording the swallows, the oesophageal and the LOS motility. During the second 24-h period, patients received baclofen 10 mg or placebo four times per day in a double-blind randomized fashion. Baclofen increased the LOS basal tone in comparison with baseline (P = 0.02), with a concomitant reduction in the number of transient LOS relaxations (TLOSRs) (P = 0.01). Moreover, baclofen induced a decrease of the swallows (P = 0.02) and of primary oesophageal body waves (P = 0.04) with no changes in the amplitude. Multiple doses of baclofen determine a reduction in the number of TLOSRs and an increase in the LOS tone throughout the 24 h. The concomitant decreased number of swallows and of primary peristalsis could depend on the well-known lower amount of reflux episodes induced by the drug. The potential therapeutic effect of baclofen could be expressed not only postprandially, but also in the fasting state when reflux episodes are present as well.

Pathogenesis of gastro-oesophageal reflux disease and novel options for its therapy

Better understanding of the mechanisms that lead to reflux disease is an important area for future research, given the very high prevalence of this problem. During the lifetime of this journal, much has been learnt about the pathophysiology of reflux disease. Abnormally, frequent acid reflux plays a key role in pathogenesis: this reflux occurs predominantly during transient lower oesophageal sphincter relaxations. Analysis of the literature suggests that the importance of transient relaxations as the major permissive event for occurrence of acid reflux is currently substantially underestimated. 'Transient relaxation' is an inexact descriptor, as this motor programme includes inhibition of the diaphragmatic hiatus and distal oesophageal body circular muscle and contraction of the oesophageal longitudinal muscle. Laxity of the diaphragmatic hiatus and hiatus hernia are probably important factors that increase the probability for acid reflux to occur during transient relaxations and in allowing strain-induced reflux episodes. The importance of straining and low basal tone of the lower oesophageal sphincter in causing abnormal reflux has probably been overestimated, but these need more investigation. High resolution manometry is the key method for acquisition of important new insights into the normal and disordered mechanics of the antireflux function of the gastro-oesophageal junction, but as yet, the potential of this technique has been tapped relatively little. In the future, improved understanding of the mechanics of the gastro-oesophageal junction should lead to improved physical antireflux procedures. Much progress has been made in defining the control of transient relaxations and this has been translated into several promising options for a new class of drug that treats reflux disease by inhibition of transient relaxations. Clinical trials on these agents appear imminent.

Swallowing disorder and inhibition of cough reflex induced by atropine sulfate in conscious dogs

In this study, the effects of atropine sulfate (atropine) on swallowing and cough reflex were evaluated in the two experimental models in conscious dogs. To evaluate the effects of atropine on swallowing, 1 mL of marker (contrast medium) was injected into the pharynx under X-ray exposure to induce swallowing. Baclofen, used as a positive control, caused marker congestion in the upper esophagus. In our experimental model, atropine (0.02 and 0.1 mg/kg, i.v.) dose-dependently increased not only the number of marker congestions but also that of the swallows. In addition, atropine significantly shortened the onset of first swallowing. In the evaluation of atropine effects on electrically evoked cough reflex induced by two electrodes implanted into the trachea, atropine strongly inhibited the number of coughs at 0.01 or 0.05 mg/kg accompanied with 0.01 or 0.05 mg/kg per hour (i.v.), respectively. These findings indicate that atropine has the potential of causing aspiration pneumonia through induction of swallowing disorder and inhibition of the cough reflex.

Tricyclic antidepressants and the risk of reflux esophagitis

OBJECTIVE

Incompetence of the lower esophageal sphincter (LES) is a key factor in the pathogenesis of gastroesophageal reflux disease (GERD). Drugs with anticholinergic properties, such as tricyclic antidepressants (TCAs), may facilitate GERD by a relaxing effect on the LES.

AIM

To investigate whether the use of TCAs is associated with an increased risk of reflux esophagitis (RE).

METHOD

A population-based case-control study was conducted within a large Dutch primary care database over the period 1996-2005. Cases with endoscopy-confirmed RE were identified and matched with up to 10 controls on gender, age, GP practice, and calendar time. Exposure to TCAs was assessed in the year prior to diagnosis and categorized as current (last prescription covered or ended within one month prior to the index date), past, and no use. The relative risk of RE was estimated by odds ratios (OR) with 95% confidence intervals (95% CI) using multivariate conditional logistic regression analysis.

RESULTS

During the study period, 1,462 cases with endoscopy-confirmed RE were identified. The risk of RE was increased in current TCA users (OR(adj) 1.61, 95% CI 1.04-2.50). Drug-specific analyses revealed that only clomipramine was associated with an increased risk of RE (OR(adj) 4.6, 95% CI 2.0-10.6) in a duration- and dose-dependent manner (OR(adj) 7.1, 95% CI 2.7-19.2 for use >180 days and OR(adj) 9.2, 95% CI 1.6-51.5 for >1 DDD equivalent/day).

CONCLUSION

No association was observed between the risk of RE and the use of TCAs other than clomipramine. The association between RE and clomipramine might be drug-related or a result of the underlying indication.

New observations on the gastroesophageal antireflux barrier

The use of high-frequency ultrasound transducers combined with manometry in the gastrointestinal (GI) tract has yielded important findings concerning the anatomy, physiology, and pathophysiology of the high-pressure zone of the gastroesophageal junction and the sphincteric muscles within. These transducers have made previously invisible portions of the GI tract accessible to investigation. Three distinct high-pressure zones have been identified and correlated with anatomic structures: the extrinsic sphincter (crural diaphragm) and the two components of the intrinsic sphincter (an upper LES and a lower LES [the gastric sling fiber/clasp fiber complex]). This article discusses the possible underlying pathophysiology of gastroesophageal reflux disease; the biomechanics of the gastroesophageal junction high-pressure zone; and the mechanism of action of standard surgical and newer endoscopic therapies for gastroesophageal reflux disease.

Review article: the pathophysiology of gastro-oesophageal reflux disease

BACKGROUND

Gastro-oesophageal reflux disease (GERD) is a common condition that develops when the reflux of stomach contents causes troublesome symptoms and/or complications.

AIM

To review the current knowledge on the underlying factors contributing to GERD, with particular emphasis on the most recent research.

METHODS

Literature searches were conducted in Medline and EMBASE. The abstracts from recent large congresses were also reviewed to ensure coverage of the latest findings.

RESULTS

The pathophysiological factors causing GERD can be split into those inducing greater exposure of the oesophagus to stomach contents, and those that provide increased perception of reflux or increased mucosal damage. Transient lower oesophageal sphincter relaxations, which are likely to be triggered by gastric distension, appear to be a key physiological cause of GERD. Excessive reflux may also be provoked by impaired oesophageal or gastric clearance mechanisms. Pre-epithelial, epithelial and post-epithelial defences all normally protect the oesophagus from injury, and may be compromised in individuals with GERD. Heartburn could also be caused by oesophageal hypersensitivity as a result of visceral neural pathway dysfunction.

CONCLUSION

The pathophysiology of GERD is multifactorial, and abnormalities in the gastro-oesophageal junction, the stomach, the oesophagus and the nervous system may all contribute to this disease state.

A case of hyoscine-related oesophagitis

We describe a previously unreported association between hyoscine hydrobromide and severe oesophagitis, with ulceration visible almost to the submucosa in the distal oesophagus. The condition resolved with cessation of tablets and 2 months' treatment with a proton-pump inhibitor.

Theophylline improves esophageal chest pain--a randomized, placebo-controlled study

BACKGROUND/AIM

The treatment of esophageal (noncardiac) chest pain is unsatisfactory and there is no approved therapy. A previous uncontrolled study suggested that theophylline may be useful. Our aims were to investigate the effects of theophylline on esophageal sensorimotor function and chest pain.

METHODS

In a double-blind study, sensory and biomechanical properties of the esophagus were assessed using impedance planimetry in 16 patients with esophageal hypersensitivity, after intravenous theophylline or placebo. In a second, randomized 4-wk crossover study, oral theophylline and placebo were administered to 24 patients with esophageal hypersensitivity. Frequency, intensity, and duration of chest pain episodes were evaluated.

RESULTS

After IV theophylline, chest pain thresholds (P=0.027) and esophageal cross-sectional area (P=0.03) increased and the esophageal wall became more distensible (P=0.04) compared with placebo. After oral theophylline, the number of painful days (P=0.03) and chest pain episodes (P=0.025), pain duration (P=0.002), and its severity (P=0.031) decreased. Overall symptoms improved in 58% on theophylline and 6% on placebo (P<0.02). There was no order effect.

CONCLUSIONS

Theophylline relaxed the esophageal wall, decreased hypersensitivity, and improved chest pain. Theophylline is effective in the treatment of functional chest pain.

Pharmacological dissection of the human gastro-oesophageal segment into three sphincteric components

Quantifications of gastro-oesophageal anatomy in cadavers have led some to identify the lower oesophageal sphincter (LOS) with the anatomical gastric sling-clasp fibres at the oesophago-cardiac junction (OCJ). However, in vivo studies have led others to argue for two overlapping components proximally displaced from the OCJ: an extrinsic crural sphincter of skeletal muscle and an intrinsic physiological sphincter of circular smooth-muscle fibres within the abdominal oesophagus. Our aims were to separate and quantify in vivo the skeletal and smooth muscle sphincteric components pharmacologically and clarify the description of the LOS. In two protocols an endoluminal ultrasound-manometry assembly was drawn through the human gastro-oesophageal segment to correlate sphincteric pressure with the anatomic crus. In protocol I, fifteen normal subjects maintained the costal diaphragm at inferior/superior positions by full inspiration/expiration (FI/FE) during pull-throughs. These were repeated after administering atropine to suppress the cholinergic smooth-muscle sphincter. The cholinergic component was reconstructed by subtracting the atropine-resistant pressures from the full pressures, referenced to the anatomic crus. To evaluate the extent to which the cholinergic contribution approximated the full smooth-muscle sphincter, in protocol II seven patients undergoing general anaesthesia for non-oesophageal pathology were administered cisatracurium to paralyse the crus. The smooth-muscle sphincter pressures were measured after lung inflation to approximate FI. The cholinergic smooth-muscle pressure profile in protocol I (FI) matched closely the post-cisatracurium smooth-muscle pressure profile in protocol II, and the atropine-resistant pressure profiles correlated spatially with the crural sling during diaphragmatic displacement. Thus, the atropine-resistant and cholinergic pressure contributions in protocol I approximated the skeletal and smooth muscle sphincteric components. The smooth-muscle pressures had well-defined upper and lower peaks. The upper peak overlapped and displaced rigidly with the crural sling, while the distal peak separated from the crus/upper-peak by 1.1 cm between FI and FE. These results suggest the existence of separate upper and lower intrinsic smooth-muscle components. The 'upper LOS' overlaps and displaces with the crural sling consistent with a physiological LOS. The distal smooth-muscle pressure peak defines a 'lower LOS' that likely reflects the gastric sling/clasp muscle fibres at the OCJ. The distinct physiology of these three components may underlie aspects of normal sphincteric function, and complexity of sphincter dysfunction.

Effect of dietary sodium chloride on gastro-oesophageal reflux: a randomized controlled trial

OBJECTIVE

It has been suggested that a high consumption of sodium chloride (NaCl) is associated with reflux symptoms. The objective of this study was to investigate the effect of increased dietary NaCl intake on gastro-oesophageal reflux and reflux mechanisms.

MATERIAL AND METHODS

In this double-blind, placebo-controlled, crossover study 10 healthy male subjects received 5 g NaCl or placebo in capsules per day for one week, after which concurrent manometric, pH and impedance monitoring was carried out for 4.5 h.

RESULTS

Oesophageal acid exposure time (pH < 4) was similar for placebo (median 11% (25th 3-75th 36)) and NaCl (9% (1-36)). No differences in the numbers of reflux episodes were found for NaCl (16 (13.5-22)) and placebo (23 (14.8-27)). Furthermore, similar numbers of liquid acid reflux episodes (placebo 12 (6.5-17.3); NaCl 10 (2.3-14.3)), liquid weakly acidic reflux episodes (placebo 5.5 (4-12.3); NaCl 6.5 (3-10.8)) and gaseous reflux episodes (placebo 1 (0-1.8); NaCl 2 (0-3)) were seen. In both conditions transient lower oesophageal sphincter relaxations (TLOSRs) were the most common reflux mechanism, followed by swallow-induced reflux. High salt intake lowered LOS pressure overall and in the first postprandial hour (p<0.01).

CONCLUSIONS

High dietary sodium intake does not increase gastro-oesophageal reflux in healthy volunteers, despite a decrease in LOS pressure.

Gastro-oesophageal reflux of liquids and gas during transient lower oesophageal sphincter relaxations

Some transient lower oesophageal sphincter relaxations (TLOSRs) are accompanied by gastro-oesophageal reflux and others are not. We aimed to investigate what factors determine the occurrence and type of reflux during TLOSRs. In 12 healthy subjects prolonged high-resolution manometry was performed. Reflux was detected using pH-impedance monitoring. A total of 219 TLOSRs were detected; no differences were observed between the duration of TLOSRs with liquid-containing reflux (20.2 +/- 1.0 s), gas reflux (17.0 +/- 1.0 s) and no reflux (19.0 +/- 1.0 s). Trans-sphincteric pressure gradient was similar in TLOSRs with liquid reflux (1.6 +/- 0.1 kPa), gas reflux (1.5 +/- 0.1 kPa) and no reflux (1.7 +/- 0.3 kPa). Prevalence, duration and amplitude of oesophageal pre-contractions and sphincteric after-contractions were not different for TLOSRs with and without reflux. The total number of TLOSRs decreased significantly from 8.2 +/- 0.8 in the first to 5.7 +/- 0.5 in the second and 4.4 +/- 0.6 in the third 70-min recording period. The number of TLOSRs accompanied by liquid-containing reflux decreased from 4.7 +/- 0.9 to 3.0 +/- 0.4 to 1.6 +/- 0.4, while the numbers of TLOSRs with gas reflux remained unchanged (2.1 +/- 0.6-2.1 +/- 0.7-2.2 +/- 0.6). Besides, time after the meal, no differences were observed in the characteristics of TLOSRs with and without gastro-oesophageal reflux. We conclude that factors, other than TLOSR characteristics, are important of whether or not a TLOSR is reflux-related.

Effect of an acute intraluminal administration of capsaicin on oesophageal motor pattern in GORD patients with ineffective oesophageal motility

Ineffective oesophageal motility (IOM) is a functional disorder affecting about 50% of gastro-oesophageal reflux disease (GORD) patients. This disease in a severe form limits the clearing ability of the oesophagus and is considered one of the predictive factors for poorer GORD resolution. Capsaicin, the active compound of red pepper, exerts a prokinetic effect on oesophageal motility in healthy subjects by increasing the amplitude of body waves, even if no evidence exists on its possible role in situations of reduced motility. The aim of the study was to evaluate the effect of an acute administration of capsaicin on the oesophageal motor pattern in a group of GORD patients affected by severe IOM. Twelve GORD patients with severe IOM received an intra-oesophageal administration of 2 mL of a red pepper-olive oil mixture and 2 mL of olive oil alone serving as a control during a stationary manometry. The motor patterns of the oesophageal body and lower oesophageal sphincter (LOS) were analysed at baseline and after the infusion of the two stimuli. The administration of capsaicin induced a significant improvement in oesophageal body contractility when compared with baseline. The velocity of propagation of waves and the LOS basal tone remained unchanged. The motor pattern was unaltered by the administration of olive oil alone. An acute administration of capsaicin seems to improve the motor performance of the oesophageal body in patients with ineffective motility. Whether this could represent the basis for further therapeutic approaches of GORD patients needs further study.

Transient lower esophageal sphincter relaxations do not result from passive opening of the cardia by gastric distention

BACKGROUND & AIMS

Transient lower esophageal sphincter relaxation is the main mechanism for gastroesophageal reflux. Although there is evidence that transient lower esophageal sphincter relaxations are neurally mediated, another school of thought is that transient lower esophageal sphincter relaxations result from gastric distention, which shortens the sphincter to the point where it opens and the pressure decreases. We assessed the relationship of transient lower esophageal sphincter relaxation to gastroesophageal junction opening in an unsedated human model.

METHODS

Seven healthy volunteers (6 men and 1 woman, aged 18-53 years) were studied while they were sitting. Manometry was performed by using a sleeve catheter passed through 1 nostril. A 5.3-mm endoscope was placed through the other nostril to obtain a retroflexed view of the cardia. The biopsy channel was connected to a barostat to distend the stomach with air at 15 mm Hg for 30 minutes. Manometric and endoscopic video-recording times were synchronized but scored independently.

RESULTS

The transient lower esophageal sphincter relaxation onset invariably preceded gastroesophageal junction opening (median, 5.0 seconds; range, 0.5-20.7 seconds; P < .001). The transient lower esophageal sphincter relaxation nadir also typically occurred before gastroesophageal junction opening (median, 2.1 seconds; range, -4.2 to +19.5 seconds; P < .001). Once open, the gastroesophageal junction moved proximally for the duration of the transient lower esophageal sphincter relaxation. Termination of transient lower esophageal sphincter relaxations occurred about the time the time of gastroesophageal junction closure.

CONCLUSIONS

These data refute the hypothesis that transient lower esophageal sphincter relaxations result from passive mechanical distraction of the gastroesophageal junction. Rather, transient lower esophageal sphincter relaxations must occur before the gastroesophageal junction can open.

Transient lower esophageal sphincter relaxations in dogs are inhibited by a metabotropic glutamate receptor 5 antagonist

Transient lower esophageal sphincter relaxation is the major mechanism for gastroesophageal reflux. The present study was initiated to investigate the potential effect of the metabotropic glutamate 5 (mGlu5) receptor antagonist, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), on transient lower esophageal sphincter relaxations in the conscious dog. MPEP (1.4-8.7 micromol/kg i.v.) produced a dose-dependent inhibition of transient lower esophageal sphincter relaxations (59+/-11% inhibition at 8.7 micromol/kg). In addition, there was a reduction of the number of reflux episodes and an increase in latency time to the occurrence of the first transient lower esophageal sphincter relaxation. No effect was seen on basal lower esophageal sphincter pressure or on swallowing. It is concluded that the mGlu5 receptor antagonist MPEP potently inhibits transient lower esophageal sphincter relaxations and that the mGlu5 receptor is a potential target for treatment of gastroesophageal reflux disease.

Inhibition of transient lower esophageal sphincter relaxation and gastroesophageal reflux by metabotropic glutamate receptor ligands

BACKGROUND & AIMS

Transient lower esophageal sphincter relaxation (TLESR) is the major mechanism of gastroesophageal acid reflux. TLESR is mediated via vagal pathways, which may be modulated by metabotropic glutamate receptors (mGluRs). Group I mGluRs (mGluR1 and 5) have excitatory effects on neurons, whereas group II (mGluR2 and 3) and group III (mGluR4, 6, 7, and 8) are inhibitory. This study determined the effect of mGluRs on triggering of TLESR and reflux in an established conscious ferret model.

METHODS

Esophageal manometric/pH studies were performed in ferrets with chronic esophagostomies. TLESR were induced by a gastric load of 25 mL glucose (pH 3.5) and 30 mL air.

RESULTS

In control treated animals, gastric load induced 3.52 +/- 0.46 TLESRs per 47-minute study, 89.7% of which were associated with reflux episodes (n = 16). The mGluR5 antagonist MPEP inhibited TLESR dose dependently, with maximal 71% +/- 7% inhibition at 35 micromol/kg (n = 9; P < .0001). MPEP also significantly reduced reflux episodes (P < .001) and increased basal lower esophageal sphincter pressure (P < .05). MPEP inhibited swallowing dose dependently, suggesting a common action on trigger mechanisms for swallowing and TLESR. The more selective analogue, MTEP, had more potent effects (90% +/- 6% inhibition TLESR at 40 micromol/kg; n = 8; P < .0001). In contrast, the group I agonist DHPG tended to increase TLESR. The group II agonist (2R, 4R)-APDC was ineffective, whereas the group III agonist L-(AP4 slightly reduced TLESR (33% at 11 micromol/kg; P < .05). The selective mGluR8 agonist (S)-3, 4-DCPG inhibited TLESR by 54% at 15 micromol/kg (P < .01).

CONCLUSIONS

mGluR5 antagonists potently inhibit TLESR and reflux in ferrets, implicating mGluR5 in the mechanism of TLESR. mGluR5 antagonists are therefore promising as therapy for patients with GERD.

New Investigational Therapies for Gastroesophageal Reflux Disease

Although PPI have revolutionized the treatment of GERD and its complications, many patients continue to have breakthrough symptoms and take antacids and H2RA. Furthermore, acid reflux actually is the innocent bystander, with few drugs available to target the true culprit, a dysfunctional LES. Future development of treatments, such as the GABA(B) agonists, which reduce TLESR, may prove an important advance in the therapy of GERD by controlling acid and nonacid reflux better. The chemical, pharmacodynamic, and clinical limitations of PPI may be addressed by the development of innovative drugs, such as the P-CAB or gastrin vaccine, to control acid secretion. Which of these drugs, if any, will be the new GERD drug for the millennium is unknown. There is no question, however, that improved drug treatments will parallel a better understanding of the complicated pathophysiology of GERD.

The lower oesophageal sphincter

The lower oesophageal sphincter (LOS) is a specialized segment of the circular muscle layer of the distal oesophagus, accounting for approximately 90% of the basal pressure at the oesophago-gastric junction. Together with the crural diaphragm, it functions as an antireflux barrier protecting the oesophagus from the caustic gastric content. During swallowing or belching, the LOS muscle must relax briefly in order to allow passage of food or intragastric air. These swallow-induced and prolonged transient lower oesophageal sphincter relaxations (TLOSRs) respectively result from activation of the inhibitory motor innervation of the sphincter. Both in man and animals, the main neurotransmitter released by the inhibitory neurones is nitric oxide. The two typical examples of dysfunction of the LOS are achalasia and gastro-oesophageal reflux disease (GORD). Achalasia is characterized by reduction or even absence of the inhibitory innervation to the LOS, leading to impaired LOS relaxation with dysphagia and stasis of food in the oesophagus. On the contrary, GORD results from failure of the antireflux barrier, with increased exposure of the oesophagus to gastric acid. This leads to symptoms such as heartburn and regurgitation, and in more severe cases to oesophagitis, Barrett's oesophagus and even carcinoma. To date, TLOSRs are recognized as the main underlying mechanism, and may represent an important target for treatment. More insight in the pathogenesis of both diseases will undoubtedly lead to new treatments in the near future.

Transient lower esophageal sphincter relaxations (TLESRs) are the major mechanism of gastroesophageal reflux but are not the cause of reflux disease

In healthy subjects, the rate of acid reflux during transient lower esophageal sphincter relaxations (TLESRs) is more frequent at the proximal margin of the LES. In this study, we investigated the hypothesis that the rate of acid reflux at the proximal margin of LES during TLESRs is similar in reflux disease to that in healthy subjects. Concurrent esophageal manometry and pH monitoring were performed in the sitting position for 3 hr after a standard meal in 10 patients with reflux disease and 10 age-matched healthy controls. The rate of TLESRs in patients with reflux disease (5.0/hr [3.3-6.7]; median [interquartile range]) was similar to that of controls (4.5/hr [3.7-5.7]). The incidence of acid reflux 7 cm above the LES during TLESRs in patients (48.1% [27.2-71.4%]) was significantly higher than that in controls (10.9% [0.0-18.8%]) but there was no difference 2 cm above the LES (75.0 [69.2-87.5] vs. 74.3 [55.5-90.0%]). The rate of TLESRs and the incidence of acid reflux during TLESRs are not increased in reflux disease. These findings, therefore, indicate that reflux disease is not a disorder of TLESRs and relates more to the proximal extent of the refluxate.

Flow across the gastro-esophageal junction: lessons from the sleeve sensor on the nature of anti-reflux barrier

The principles of fluid flow are critical to the understanding of flow across the gastro-esophageal (GE) junction or gastro-esophageal reflux. The mechanism by which sleeve sensor measures lower esophageal sphincter (LES) pressure is also based on the principle of fluid flow across the GE junction and can provide important insights into the nature of anti-reflux barrier. We present arguments regarding the role of the length of LES, intra-abdominal length of the LES, flap valve at the GE junction and the angle of His on the strength of anti-reflux barrier. Our conclusion is that in the presence of normal anatomy of the GE junction (absence of hiatus hernia) the pressure at the GE junction is the most important determinant of the strength of anti-reflux barrier.

Gastroesophageal reflux: a potential asthma trigger

Gastroesophageal reflux (GER) is a potential trigger of asthma. Approximately 77% of asthmatics report heartburn. GER is a risk factor for asthma-related hospitalization and oral steroid burst use. Asthmatics may be predisposed to GER development because of a high prevalence of hiatal hernia and autonomic dysregulation and an increased pressure gradient between the abdominal cavity and the thorax, over-riding the lower esophageal sphincter pressure barrier. Asthma medications may potentiate GER. Potential mechanisms of esophageal acid-induced bronchoconstriction include a vagally mediated reflex, local axonal reflexes, heightened bronchial reactivity, and microaspiration, all resulting in neurogenic inflammation. Anti-reflux therapy improves asthma symptoms in approximately 70% of asthmatics with GER. A 3-month empiric trial of twice-daily proton pump inhibitor given 30 to 60 minutes before breakfast and dinner can identify asthmatics who have GER as a trigger of their asthma.

Mechanisms of gastroesophageal reflux in critically ill mechanically ventilated patients

BACKGROUND & AIMS

Gastroesophageal reflux is a major problem in mechanically ventilated patients and may lead to pulmonary aspiration and erosive esophagitis. Transient lower esophageal sphincter relaxations are the most common mechanism underlying reflux in nonventilated patients. The mechanisms that underlie reflux in critically ill ventilated patients have not been studied. The aim of this study was to determine the mechanisms underlying gastroesophageal reflux in mechanically ventilated patients in the intensive care unit.

METHODS

In 15 mechanically ventilated intensive care unit patients, esophageal motility, pH, and intraluminal impedance (11/15 patients) were recorded for 1 hour before and 5 hours during continuous nasogastric feeding.

RESULTS

Basal lower esophageal sphincter pressure was uniformly low (2.2 +/- 0.4 mmHg). The median (interquartile range) acid exposure (pH <4) was 39.4% (0%-100%) fasting and 32% (7.5%-94.2%) fed. Acid reflux occurred in 10 patients, but slow drifts in esophageal pH were also an important contributor to acid exposure. If esophageal pH decreased to pH <4, it tended to remain so for prolonged periods. A total of 46 acid reflux events were identified. Most (55%) occurred because of absent lower esophageal sphincter pressure alone; 45% occurred during straining or coughing.

CONCLUSIONS

Gastroesophageal reflux in mechanically ventilated patients is predominantly due to very low or absent lower esophageal sphincter pressure, often with a superimposed cough or strain. These data suggest that measures that increase basal LES pressure may be useful to prevent reflux in ventilated patients.

Effect of lower esophageal sphincter tone and crural diaphragm contraction on distensibility of the gastroesophageal junction in humans

Previous studies of distensibility of the gastroesophageal junction (GEJ) in humans have not tried to distinguish between the effects of muscle action and passive elastic tissue properties of the GEJ. We studied 15 healthy subjects (ages 23-67 yr, 11 men/4 women) by using a catheter with a highly complaint bag positioned manometrically at the GEJ. The bag was distended with air at a rate of 20 ml/min while intrabag pressure was recorded. Distensions were performed during normal breathing, with breath held at maximum inspiration (MI) to activate the diaphragmatic crura, and with midesophageal balloon distension (BD) to relax the lower esophageal sphincter. In 10 subjects, distensions were performed after atropine injection (12 microg/kg iv). Pressure-volume curves and incremental distensibility values were calculated and compared among the different conditions. Both MI and BD significantly altered the slopes of the pressure-volume curves, whereas no effect was seen with atropine. Maximum distensibility was seen at the volume increment of 5-10 ml and was reduced with larger volumes. Distensibility measurements for the various test conditions tended to converge at the largest volume increment, suggesting that distensibility at this degree of distension was more related to the passive elastic properties of the GEJ. On the basis of these findings, we conclude that there can be significant active muscular contributions to recordings of distensibility at the GEJ, variations that must be controlled for during different study conditions.

The role of hiatus hernia in gastro-oesophageal reflux disease

This article gives an overview of the role of sliding hiatus hernia in gastro-oesophageal reflux disease (GORD). The crural diaphragm acts as an external sphincter of the anti-reflux barrier. Contractions of the crural diaphragm increase lower-oesophageal-sphincter (LOS) pressure during each inspiration and in situations of increased abdominal pressure, whereas these contractions are inhibited when gas and/or a bolus has to pass the gastro-oesophageal junction. A hiatus hernia is associated with GORD symptoms, increased oesophageal acid exposure, and oesophagitis and its severity. In patients with hiatus hernia, the incidence of reflux episodes is increased during periods with low LOS pressure, straining and swallowing. These findings underline the importance of the crural diaphragm, which, when surrounding the LOS, protects against gastro-oesophageal reflux.

The effect of total and anterior partial fundoplication on antireflux mechanisms of the gastroesophageal junction

BACKGROUND

The effect of total (Nissen) and anterior partial fundoplication (APF) for the surgical treatment of gastroesophageal reflux disease (GERD) on the motor behavior of the esophagogastric axis has not been fully assessed. The purpose of this study was to assess any alterations in lower esophageal sphincter (LES) and gastric fundus motor parameters in GERD patients after Nissen or APF fundoplication.

METHODS

Twenty four patients with documented GERD underwent either laparoscopic Nissen fundoplication (n = 12) or laparoscopic APF (n = 12). Preoperative and postoperative stationary esophageal manometry included assessment of LES resting and postdeglutition relaxation pressures, intragastric pressure, and LES transient relaxations in the left lateral and upright positions and after gastric distension.

RESULTS

Both types of fundoplication resulted in significant increases in LES resting (P <0.001) and postdeglutition relaxation pressure (P <0.001) in both positions and after gastric distention. Intragastric pressure increased only after Nissen fundoplication in the postgastric distention state (P = 0.01). Transient LES relaxations were equally abolished after both procedures. All postoperative changes were to a similar level after either procedure with the exception of intragastric pressure after gastric distention, which was significantly higher after total than after partial fundoplication (P = 0.04).

CONCLUSIONS

Both procedures equally increase LES resting and postdeglutition relaxation pressures and abolish transient LES relaxations at all states. The significantly higher intragastric pressure at the postgastric distention state after Nissen fundoplication could possibly explain the higher incidence of epigastric fullness and discomfort after this type of antireflux surgery.

Different responsiveness of excitatory and inhibitory enteric motor neurons in the human esophagus to electrical field stimulation and to nicotine

To compare electrical field stimulation (EFS) with nicotine in the stimulation of excitatory and inhibitory enteric motoneurons (EMN) in the human esophagus, circular lower esophageal sphincter (LES), and circular and longitudinal esophageal body (EB) strips from 20 humans were studied in organ baths. Responses to EFS or nicotine (100 microM) were compared in basal conditions, after N(G)-nitro-l-arginine (l-NNA; 100 microM), and after l-NNA and apamin (1 microM). LES strips developed myogenic tone enhanced by TTX (5 microM) or l-NNA. EFS-LES relaxation was abolished by TTX, unaffected by hexamethonium (100 microM), and enhanced by atropine (3 microM). Nicotine-LES relaxation was higher than EFS relaxation, reduced by TTX or atropine, and blocked by hexamethonium. After l-NNA, EFS elicited a strong cholinergic contraction in circular LES and EB, and nicotine elicited a small relaxation in LES and no contractile effect in EB. After l-NNA and apamin, EFS elicited a strong cholinergic contraction in LES and EB, and nicotine elicited a weak contraction amounting to 6.64 +/- 3.19 and 9.20 +/- 5.51% of that induced by EFS. EFS elicited a contraction in longitudinal strips; after l-NNA and apamin, nicotine did not induce any response. Inhibitory EMN tonically inhibit myogenic LES tone and are efficiently stimulated both by EFS and nicotinic acetylcholine receptors (nAChRs) located in somatodendritic regions and nerve terminals, releasing nitric oxide and an apamin-sensitive neurotransmitter. In contrast, although esophageal excitatory EMN are efficiently stimulated by EFS, their stimulation through nAChRs is difficult and causes weak responses, suggesting the participation of nonnicotinic mechanisms in neurotransmission to excitatory EMN in human esophagus.

Progress with novel pharmacological strategies for gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GORD) is a chronic disorder characterised by an increased exposure of the oesophagus to intragastric contents. Currently, GORD symptoms are maintained under control with antisecretory agents, mainly gastric proton pump inhibitors (PPIs). Although impaired oesophageal motility may partly underlie the pathophysiology of GORD, the use of prokinetic agents has been found to be unsatisfactory. To date, novel pharmacological approaches for GORD are mainly related to the control of transient lower oesophageal sphincter (LOS) relaxations (TLOSRs). The majority of patients with GORD have reflux episodes during TLOSRs, which are evoked by gastric distension, mainly occurring after ingestion of a meal. Patients with reflux disease with normal peristalsis and without or with mild erosive disease could potentially benefit from anti-TLOSR therapy. This therapy might also be of value to treat some severe forms of esophagitis in combination with PPIs. GABA-B-receptor agonists are the most promising class of agents identified so far for TLOSR control. The GABA-B-receptor agonist, baclofen, is the most effective compound in inhibiting TLOSRs in humans. Since baclofen has several CNS adverse effects, novel orally available GABA-B agonists are needed for effective and well tolerated treatment of GORD. Endogenous or exogenous cholecystokinin (CCK) causes a reduction in LOS pressure, an increase in TLOSR frequency and a reduction in gastric emptying. In healthy volunteers and patients with GORD, loxiglumide, a selective CCK1-receptor antagonist, was found to reduce the rate of TLOSRs, although its effect on postprandial acid reflux may be modest. Orally effective CCK antagonists are not marketed to date. The anticholinergic agent atropine, given to healthy volunteers and patients with GORD, markedly reduced the rate of TLOSRs. Because of severe gastrointestinal (and other) adverse effects of anticholinergics, including worsening of supine acid clearance and constipation, it is unlikely that this class of drugs will have a future as anti-TLOSR agents on a routine basis. In spite of their effectiveness in reducing TLOSR rate, untoward adverse effects, such as addiction and severe constipation, currently limit the use of morphine and other opioid mu-receptor agonists. The same applies to nitric oxide synthase inhibitors, which are associated with marked gastrointestinal, cardiovascular, urinary and respiratory adverse effects. Animal studies provide promising evidence for the use of cannabinoid receptor 1 agonists, by showing potent inhibition of TLOSRs in the dog, thus opening a new route for clinical investigation in humans. A better understanding of TLOSR pathophysiology is a necessary step for the further development of novel drugs effective for anti-reflux therapy.

Gastroesophageal reflux disease and baclofen: is there a light at the end of the tunnel?

Transient lower esophageal sphincter relaxations (TLESRs) are rapid and prolonged relaxations of the lower esophageal sphincter (LES) that are not associated with swallowing. They are the mechanism by which most gastroesophageal reflux episodes occur in normal people and in patients with esophagitis. Transient LES relaxations appear to be mediated by a vagovagal reflex initiated by gastric distention. Baclofen is a g-aminobutyric acid (GABA) derivative that inhibits the production of TLESRs by acting as a GABA(B) receptor agonist at one or more loci along the vagovagal reflex arc. Animal and human studies suggest that baclofen decreases the number of reflux events and amount of esophageal acid exposure. Baclofen or another GABA(B) receptor agonist may be clinically useful in treatment of gastroesophageal reflux disease.

An experimental model for the study of transient lower oesophageal sphincter relaxation and motor function of the proximal stomach in humans

A simple and reliable experimental model would be useful in human research on new drugs which target transient lower oesophageal sphincter (LOS) relaxation. The aim was to investigate the effect of repeated distensions on the rate of transient LOS relaxation, LOS pressure and motor function of the proximal stomach. Twelve healthy subjects were studied with a multilumen manometric assembly incorporating a sleeve sensor for the LOS and a bag positioned in the proximal stomach and connected to a barostat. Intrabag volume was set at 75% of the threshold for gastric discomfort and maintained for two 30-min distension periods separated by a 45-min washout with the bag deflated. The studies lasted 145 +/- 2 min. The rate of transient LOS relaxations was similar during the two distensions, 3.5;2-4 vs 3;2.5-4 (median;interquartile range) and so was LOS pressure. Baseline intrabag pressure, as a measure of gastric tone, and the number of pressure waves, as a measure of phasic contractions, were also similar, 11.3;9.3-12.3 mmHg vs 10.8;9.3-12.5 mmHg and 16;13-28 mmHg vs 19;15-29 mmHg, respectively. Our model allows to perform 1-day studies which can assess two experimental conditions on transient LOS relaxations and motor function of the proximal stomach within an acceptable time span.

Effect of baclofen on emesis and 24-hour esophageal pH in neurologically impaired children with gastroesophageal reflux disease

OBJECTIVES

Gastroesophageal reflux disease (GERD) is difficult to control with medical therapy in neurologically impaired children. The gamma-aminobutyric acid type B receptor agonist baclofen was recently reported to reduce reflux in adult patients with GERD by reducing the incidence of transient lower esophageal sphincter relaxations. The current study was undertaken to investigate the effects of baclofen on GERD in neurologically impaired children.

METHODS

Eight neurologically impaired children with GERD between 2 months and 16 years were studied. Baclofen (0.7 mg/kg/day) was administered orally or via nasogastric tube in three divided doses 30 minutes before meals for 7 days. The frequency of emesis on and off baclofen were recorded as a measure of clinical impact. Twenty-four-hour esophageal pH monitoring was conducted before and on the seventh day of the administration of baclofen.

RESULTS

The frequency of emesis was significantly decreased (P = 0.03). The total number of acid refluxes was significantly decreased both during the entire 24-hour period (P = 0.01) and during the postprandial period (P = 0.049). The number of acid refluxes longer than 5 minutes was significantly decreased during the 24-hour period (P = 0.02). The percentage total time of esophageal pH <4.0 and esophageal acid clearance time were not significantly different during the 24-hour period or during the postprandial period. No adverse effects were observed, except for a slight reduction in muscle tone in one subject.

CONCLUSIONS

In this 1-week trial, repetitive administration of baclofen reduced the frequency of emesis and the total number of acid refluxes in neurologically impaired children with GERD.