Antropyloric modulation of transpyloric flow of liquids in pigs

Effect of endoscopic sleeve gastroplasty on gastric emptying, motility and hormones: a comparative prospective study

OBJECTIVE

Endoscopic sleeve gastroplasty (ESG) has gained global adoption but our understanding of its mechanism(s) of action and durability of efficacy is limited. We sought to determine changes in gastric emptying (GE), gastric motility (GM), hormones and eating behaviours after ESG.

DESIGN

A priori-designed single-centre substudy of a large US randomised clinical trial, adults with obesity were randomised to ESG or lifestyle interventions (LS) alone. We measured GE, hormones and weight loss and assessed eating behaviours. In a subset of ESG patients, we assessed GM. The primary outcome was the change in T1/2 (min) at 3 months, and secondary outcomes were changes in weight, GE, GM, hormones and eating behaviours. We used t-test analyses and regression to determine the association between GE and weight loss.

RESULTS

36 (ESG=18; LS=18) participated in this substudy. Baseline characteristics were similar between the two groups. At 3 months, T1/2 was delayed in the ESG group (n=17) compared with the LS group (n=17) (152.3±47.3 vs 89.1±27.9; p<0.001). At 12 months, T1/2 remained delayed in the ESG group (n=16) vs control group (n=14) (137±37.4 vs 90.1±23.4; p<0.001). Greater delays in GE at 3 months were associated with greater weight loss. GM was preserved and fasting ghrelin, glucagon-like peptide 1 and polypeptide YY significantly increased 18 months after ESG.

CONCLUSION

ESG promotes weight loss through several key mechanistic pathways involving GE and hormones while preserving GM. These findings further support clinical adoption of this technique for the management of obesity.

TRIAL REGISTRATION NUMBER

NCT03406975.

Transpyloric propagation and liquid gastric emptying in children with foregut dysmotility

BACKGROUND/OBJECTIVES

Gastric emptying (GE) requires precise antropyloroduodenal coordination for effective transpyloric flow, the mechanisms of which are still unclear. We aimed to correlate gastric antral function assessed by antroduodenal manometry (ADM) with GE scintigraphy (GES) for liquid feeds in children with suspected gastrointestinal dysmotility.

METHODS

Children who underwent both ADM and GES over a five-year period were reviewed. ADM tracings were re-analyzed to assess antral frequency, amplitude, and motility index (MI) pre-prandially and postprandially. Transpyloric propagation (TPP) was defined as antegrade propagated antral activity preceding duodenal phase III of the migrating motor complex (MMC). TPP was defined as "poor" if occurring in <50% of all presented duodenal phases III. For GES, regions of interest over the whole stomach, fundus, and antrum were drawn to calculate GE half-time (GE-T_1/2 ) and retention rate (RR) in each region at 1 and 2 h.

RESULTS

Forty-seven children (median age: 7.0 years) were included. Twenty-two had PIPO, 14 functional GI disorders, and 11 gastroparesis. Children with poor TPP had longer GE-T_1/2 (113.0 vs 66.5 min, p = 0.028), higher RR of the whole stomach and fundus at 1 h (79.5% vs 63.5%, p = 0.038; 60.0% vs 41.0%, p = 0.022, respectively) and 2 h (51.0% vs 10.5%, p = 0.005; 36.0% vs 6.5%, p = 0.004, respectively). The pre-prandial antral amplitude of contractions inversely correlated with GE-T_1/2 , RR of the whole stomach, and fundus at 2 h.

CONCLUSIONS

TPP during phase III of the MMC correlated with gastric emptying of liquid and its assessment on ADM might predict abnormalities in postprandial gastric function.

Vagally Mediated Gut-Brain Relationships in Appetite Control-Insights from Porcine Studies

Signals arising from the upper part of the gut are essential for the regulation of food intake, particularly satiation. This information is supplied to the brain partly by vagal nervous afferents. The porcine model, because of its sizeable gyrencephalic brain, omnivorous regimen, and comparative anatomy of the proximal part of the gut to that of humans, has provided several important insights relating to the relevance of vagally mediated gut-brain relationships to the regulation of food intake. Furthermore, its large size combined with the capacity to become obese while overeating a western diet makes it a pivotal addition to existing murine models, especially for translational studies relating to obesity. How gastric, proximal intestinal, and portal information relating to meal arrival and transit are encoded by vagal afferents and their further processing by primary and secondary brain projections are reviewed. Their peripheral and central plasticities in the context of obesity are emphasized. We also present recent insights derived from chronic stimulation of the abdominal vagi with specific reference to the modulation of mesolimbic structures and their role in the restoration of insulin sensitivity in the obese miniature pig model.

Pathophysiology and pharmacotherapy of gastroparesis: current and future perspectives

INTRODUCTION

Gastroparesis is an important clinical disorder characterised by delayed gastric emptying in the absence of mechanical outlet obstruction. Idiopathic, diabetes and postsurgical causes represent the most common aetiologies. The condition commonly manifests as upper gastrointestinal symptoms, including nausea, vomiting, postprandial fullness, early satiety, abdominal pain and bloating.

AREAS COVERED

This paper provides a review of the prevalence, pathophysiology and clinical features associated with gastroparesis, with a particular focus on current pharmacological management options and novel and emerging therapies. A literature search was undertaken using the search terms: gastroparesis, diabetic gastroparesis, idiopathic gastroparesis, gastric emptying, prokinetic, metoclopramide, domperidone, erythromycin, motilin, alemcinal, KC11458, mitemcinal, ghrelin, TZP-101, TZP-102, RM-131, tegaserod, prucalopride, naronapride, velusetrag, levosulpiride, itopride, botulinum toxin, gastric electrical stimulation, Enterra.

EXPERT OPINION

Strategies for the management of gastroparesis include correction of malnutrition, dehydration and electrolyte imbalance, relief of symptoms by appropriate use of prokinetic and antiemetic agents and, in patients with gastroparesis associated with diabetes or critical illness-induced hyperglycaemia, optimisation of glycaemic control. Conventional prokinetic agents form the mainstay of treatment. While novel pharmacotherapies are in development, compelling evidence for their efficacy, particularly in symptom relief, remains to be established.

Quantification of the effects of the volume and viscosity of gastric contents on antral and fundic activity in the rat stomach maintained ex vivo

AIMS

The aim of this study was to examine the effect of varying the rheological properties of perfusate on the volume and muscular activity of the various compartments of the rat stomach.

METHODS

Image analysis was used to quantify the activity of the ex vivo stomach preparations when perfused according to a ramp profile.

RESULTS

The area of the fundus increased to a greater extent than that of the body when watery or viscous material was perfused. However, initial distension of the corpus was greater and occurred more rapidly when viscous material was perfused. Only the fundus expanded when perfusion followed the administration of verapamil. The frequency of antrocorporal contractions decreased significantly and the amplitude of antrocorporal contractions increased significantly with increase in gastric volume. The velocity of antrocorporal contractions did not vary with gastric volume but varied regionally in some preparations being faster distally than proximally. Neither the frequency, amplitude or velocity of antrocorporal contractions differed when pseudoplastic rather than watery fluid was perfused. However, the characteristics of antrocorporal contractions changed significantly when the stomach was perfused with material with rheological characteristics that induce different patterns of wall tension to those normally encountered. Hence, the mean frequency and speed of propagation of antrocorporal contractions increased and their direction of propagation became inconstant.

Manipulating digestion with foods designed to change the physical characteristics of digesta

We explore how foods can be designed to modulate digestion and to promote health by changing the physical properties of digesta. The physical characteristics of digesta are discussed along with their impact on the physiology of digestion with special reference to sites where these characteristics are likely to influence digestive efficiency. Evidence is reviewed regarding the effects of supplementation with viscoactive agents on the flow and mixing of digesta in particular segments of the human gut that, by changing the rheology and liquid permeability of digesta in that segment, influence specific aspects of digestion and absorption.

Comparative effects of oral and intraduodenal glucose on blood pressure, heart rate, and splanchnic blood flow in healthy older subjects

Postprandial hypotension occurs frequently, particularly in the elderly. The magnitude of the fall in blood pressure (BP) and rise in heart rate (HR) in response to enteral glucose are greater when gastric emptying (GE) or small intestinal infusion are more rapid. Meal ingestion is associated with an increase in splanchnic blood flow. In contrast, gastric distension may attenuate the postprandial fall in BP. The aims of this study were to evaluate, in older subjects, the comparative effects of intraduodenal glucose infusion, at a rate similar to GE of oral glucose, on BP, HR, superior mesenteric artery (SMA) flow, and blood glucose. Eight healthy subjects (5 men, 3 women, age 66-75 yr) were studied on two occasions. On day 1, each subject ingested 300 ml of water containing 75 g glucose. GE was quantified by three-dimensional ultrasonography between time t = 0-120 min, and the rate of emptying (kcal/min) was calculated. On day 2, glucose was infused intraduodenally at the same rate as that on day 1. On both days, BP, HR, SMA flow, and blood glucose were measured. The mean GE of oral glucose was 1.3 +/- 0.1 kcal/min. Systolic BP (P < 0.01), SMA flow (P < 0.05), and blood glucose (P < 0.01) were greater and HR less (P < 0.01) after oral, compared with intraduodenal, glucose. There were comparable falls in diastolic BP during the study days (P < 0.01 for both). We conclude that the magnitude of the fall in systolic BP and rise in HR are less after oral, compared with intraduodenal, glucose, presumably reflecting the "protective" effect of gastric distension.

Quantification of distal antral contractile motility in healthy human stomach with magnetic resonance imaging

PURPOSE

To quantify healthy postprandial: 1) propagation, periodicity, geometry, and percentage occlusion by distal antral contraction waves (ACWs); and 2) changes in ACW activity in relationship to gastric emptying (GE).

MATERIALS AND METHODS

Using 1.5-T MR scanner, nine healthy fasted volunteers were examined in the right decubitus position after ingestion of 500 mL of 10% glucose (200 kcal) with 500 microM Gd-DOTA. Total gastric (TGV) and meal volumes (MV) were assessed every five minutes for 90 minutes, in and interspersed with dynamic scan sequences (duration: 2.78 minutes) providing detailed images of distal ACWs.

RESULTS

TGV increased by 738+/-38 mL after ingestion (t0), subsequently decreasing in parallel to GE. The mean GE rate and half-emptying time were 24+/-3 mL/5 minutes and 71+/-6 minutes, respectively. Accompanying ACWs reached a periodicity of 23+/-2 seconds at t35 and propagated at an unvarying speed of 0.27+/-0.01 cm/second. Their amplitude of 0.70+/-0.08 cm was constant, but the width decreased along the antral wall by 6+/-2%/cm (P=0.003). ACWs were nonocclusive (percentage occlusion 58.1+/-5.9%, t0 at the pylorus) with a reduction in occlusion away from the pylorus (P<0.001). No propagation and geometry characteristics of ACWs correlated with the changes of MV (mL/5 minutes; R2<0.05).

CONCLUSION

Our results indicate that ACWs are not imperative for emptying of liquids. This study provides a detailed quantitative reference for MRI inquiries into pharmacologically- and pathologically-altered gastric motility.

Measurements of gastric emptying of low- and high-nutrient liquids using 3D ultrasonography and scintigraphy in healthy subjects

Scintigraphy represents the 'gold standard' for the measurement of gastric emptying. Recent studies suggest that three-dimensional (3D) ultrasonography may allow a precise measure of gastric emptying, given the capacity for accurate volume calculations of the stomach. The aim of this study was to compare measurements of gastric emptying of both low- and high-nutrient drinks by 3D ultrasonography with scintigraphy. Ten healthy young subjects (6M, 4F, age 23.5 +/- 1.5 years) were studied on 2 days. Concurrent measurements of gastric emptying by scintigraphy and 3D ultrasonography were performed after ingestion of 500 mL beef soup (12 kcal) or 300 ml dextrose (25% w/v) (314 kcal) labelled with 20 MBq (99m)Tc-sulphur colloid. There was no significant difference between scintigraphic and ultrasonographic 50% emptying times (T50s) (soup: 27.7 +/- 4.8 min vs 23.8. +/- 4.8 min; dextrose: 122.2 +/- 13.3 min vs 131.9 +/- 10.2 min). There was a close correlation between scintigraphic and ultrasonographic T50s for both soup (r = 0.92, P = 0.0005) and dextrose (r = 0.88, P = 0.0007). For the T50s, the limits of agreement were -15.2 min and +8.1 min for the soup (mean difference -3.6 min) and -35.3 min and +47.6 min for dextrose (mean difference +6.2 min). 3D ultrasonography provides a valid measure of gastric emptying of liquid meals in healthy subjects.

Effects of posture on gastric emptying, transpyloric flow, and hunger after a glucose drink in healthy humans

Previous studies suggest that posture has relatively little effect on gastric emptying of high-nutrient liquids; these studies have, however, only assessed overall rates of gastric emptying, whereas gastric emptying is known to be predominantly a pulsatile phenomenon. In healthy subjects perceptions of appetite, such as hunger, are inversely related to antral area and content; hence, changes in intragastric meal distribution induced by posture may affect appetite. Gastric emptying is a major determinant of postprandial glycemia. The aims of this study were to evaluate the effects of posture on patterns of transpyloric flow (TF), gastric emptying (GE), antral area (AA), hunger, and the glycemic response to oral glucose. Eight healthy young subjects (five males, three females; mean age, 24.0 +/- 2.4 years; BMI, 21.2 +/- 0.6 kg/m2) were studied twice in random order, once in the sitting position and once in the lying (supine) position. After consuming 600 ml water with 75 g glucose, labeled with 20 MBq 99mTc-sulfur colloid, subjects had simultaneous measurements of (i) TF during consumption of the drink by Doppler ultrasonography, (ii) GE with scintigraphy, (iii) AA at t = -5 and t = 30 min by ultrasonography, and (iv) perceptions of appetite with a visual analogue scale. During drink ingestion TF was greater in the sitting, compared with the lying, position (586 +/- 170 vs. 177 +/- 65 [cm/sec] x sec; P < 0.05). Posture affected intragastric distribution; more of the drink was retained in the distal stomach in the sitting position (e.g., at 30 min: sitting, 29 +/- 3%, vs. lying, 12 +/- 3%; P < 0.0001) but had no effect on the overall rate of GE or the blood glucose response. AA at t = 30 min (P < 0.005) was greater in the sitting position; there was an inverse relationship between hunger and AA at 30 min (r = -0.53, P < 0.05). We conclude that posture influences initial TF and intragastric distribution, but not the overall rate of GE of, or the glycemic response to, a large-volume nutrient liquid. The increases in AA and content in the sitting position are associated with a reduction in hunger.

Lack of pyloric interstitial cells of Cajal explains distinct peristaltic motor patterns in stomach and small intestine

The frequency and propagation velocity of distension-induced peristaltic contractions in the antrum and duodenum are distinctly different and depend on activation of intrinsic excitatory motoneurons as well as pacemaker cells, the interstitial cells of Cajal associated with Auerbach's plexus (ICC-AP). Because ICC are critical for coordination of motor activities along the long axis of many regions in the gut, the role of ICC in antroduodenal coordination was investigated. We used immunohistochemistry, electron microscopy, simultaneous multiple electrical recordings in vitro, and videofluoroscopy in vivo in mice and rats. A strongly reduced number of ICC-AP with loss of network characteristics was observed in a 4-mm area in the rat and a 1-mm area in the mouse pyloric region. The pyloric region showed a slow wave-free gap of 4.1 mm in rats and 1.3 mm in mice. Between antrum and duodenum, there was no interaction of electrical activities and in the absence of gastric emptying, there was no coordination of motor activities. When the pyloric sphincter opened, 2.4 s before the front of the antral wave reached the pylorus, the duodenum distended after receiving gastric content and aboral duodenal peristalsis was initiated, often disrupting other motor patterns. The absence of ICC-AP and slow wave activity in the pyloric region allows the antrum and duodenum to have distinct uncoordinated motor activities. Coordination of aborally propagating peristaltic antral and duodenal activity is initiated by opening of the pylorus, which is followed by distention-induced duodenal peristalsis. Throughout this coordinated motor activity, the pacemaker systems in antrum and duodenum remain independent.

Effect of aging on transpyloric flow, gastric emptying, and intragastric distribution in healthy humans--impact on glycemia

The aims of this study were to evaluate (i) the relationship between transpyloric flow (TF) assessed by Doppler ultrasonography and scintigraphy, (ii) the effects of healthy aging on TF and gastric emptying (GE), and (iii) the relationship between the glycemic response to oral glucose and TF. Ten healthy "young" (7 M, 3 F) and 8 "older" (4 M, 4 F), subjects had simultaneous measurements of TF, GE, and blood glucose after a 600-ml drink (75 g glucose labeled with 20 MBq 99mTc-sulfur colloid) while seated. TF measured by ultrasound was measured during drink ingestion and for 30 min thereafter. GE was measured scintigraphically for 180 min after drink ingestion. Blood glucose was measured before the drink and at regular intervals until 180 min. During drink ingestion, TF was greater (P < 0.05) and GE faster (retention at 60 min: 70.8+/-3.3 vs. 83.8+/-4.6%; P < 0.05) in young compared to older subjects. There was no difference in fasting blood glucose between the two groups but the magnitude of the rise in blood glucose was greater in the young compared to the older subjects; (at 15 min 2.4+/-0.3 vs. 1.5+/-0.5 mmol/L; P < 0.05). In contrast, after 90 min blood glucose concentrations were higher in the older subjects. There were significant relationships between the early blood glucose concentration and both TF (e.g., at 15 min: r = 0.56, P < 0.05) and GE (e.g., at 15 min: r = -0.51, P < 0.05). In conclusion, the results of this study indicate that (i) TF is initially less, and GE slower, in older compared to young subjects; (ii) the initial glycemic response to oral glucose is related to TF; and (iii) measurements of TF by ultrasound and scintigraphy correlate significantly.

Involvement of NO in gastric emptying of semi-solid meal in conscious pigs

The influence of non-selective nitric oxide synthase (NOS) inhibition on gastric emptying of a semi-solid meal was studied in conscious pigs. Antroduodenal motility and fundic compliance were also assessed to evaluate the mechanisms at the origin of potential alteration in gastric emptying pattern. N(G)-nitro-L-arginine methyl ester (L-NAME; 20 mg kg(-1) i.v.) delayed gastric emptying (half-emptying time of 128.98 +/- 16.86 min vs 73.74 +/- 7.73 min after saline, P < 0.05, n = 6) as a result of decreased proximal gastric emptying. No changes were observed for distal gastric emptying as a result of unchanged antral motility. Similarly, no changes were noted on duodenal motor patterns either in the fasted or in the fed state. L-NAME decreased fundic compliance in fasted state (49 +/- 11 mL mmHg(-1) vs 118 +/- 15 mL mmHg(-1) after saline, P < 0.05, n = 6). As this phenomenon is expected to increase emptying rate, the gastroparesis induced by NOS inhibition is thus likely to originate from distal resistive forces. It is concluded that NO positively modulates gastric emptying.

Gastric scintigraphy with a liquid-solid radiolabelled meal: performances of solid and liquid parameters

AIM

To assess the clinical performance of parameters of liquid-solid gastric emptying (GE) scintigraphy.

METHODS

Fifty-three controls and 476 patients underwent GE scintigraphy using a liquid-solid test meal (non-ulcer dyspepsia, n=180; gastro-oesophageal reflux disease, n=123; dyspepsia after anti-reflux surgery, n=29; diabetes mellitus, n=96; cystic fibrosis prior to heart-lung transplantation, n=48). Time-activity curves were fitted by a power exponential function and half-emptying times (T1/2) were computed. The lag phase (Tlag) and constant emptying (TRE) times of solid emptying were also calculated using a mathematical method (maximum slope tangent method).

RESULTS

TRE and T1/2 of solids were higher in each subgroup of patients vs. controls (P=0.0001) and in cystic fibrosis patients vs. gastro-oesophageal reflux patients (P=0.0001). Tlag was significantly higher only in non-ulcer dyspepsia patients vs. controls (P=0.001). There was no significant difference for liquid parameters. Using the mean+/-1.96 SD of the solid and liquid T1/2 values obtained in controls, GE was normal (n=251; 53%), delayed (n=183; 38%), accelerated (n=33; 7%) or mixed (n=9; 2%). Delayed solid T1/2 was the most prominent alteration (n=189), and alterations of liquid GE alone were present in only 24 (5%) patients. A good correlation was found between solid T1/2 and TRE (r=0.88), but no correlation between Tlag and TRE, suggesting that these estimates represent independent phases of GE. In 26 patients, all GE parameters of solids and liquids were normal except Tlag (n=8) or TRE (n=18). The lack of significant differences between the different patient subgroups did not allow emptying profiles to be drawn according to patient pathology.

CONCLUSION

Liquid GE scintigraphy provided poor and unreliable information in terms of patient discrimination and the drawing of pathophysiological profiles of abnormal GE. Tlag and TRE may confirm GE alteration, especially when solid T1/2 values are at the superior limit of normality, and may improve the performance of GE scintigraphy, rather than using liquid parameters.

Inter-digestive and post-prandial antro-pyloro-duodenal motor activity in humans: effect of 5-hydroxytryptamine 1 receptor agonism

BACKGROUND

Little is known about the effect of 5-hydroxytryptamine 1 (5-HT(1)) receptor agonism on the co-ordinated motor activity of the gastric antrum, pylorus and duodenum under fasting and fed conditions.

AIM

To evaluate the effect of sumatriptan, a 5-HT(1) agonist, on fasting and fed antro-pyloro-duodenal motility.

METHODS

In study 1, antro-pyloro-duodenal motility was recorded for two phase IIIs of the migrating motor complex and then, following either a subcutaneous injection of sumatriptan 6 mg or saline control, for at least one additional phase III in 11 healthy volunteers (21-36 years). In study 2, the post-prandial motility was recorded for 3 h after either a subcutaneous injection of sumatriptan 6 mg or saline control in 10 healthy volunteers (18-36 years).

RESULTS

Sumatriptan prolonged the migrating motor complex cycle (P = 0.009) by increasing the duration of phase II (P = 0.02) but not phases I and III. Post-prandially, sumatriptan reduced the activity index (P = 0.017) by reducing the frequency of co-ordinated motor activity involving the antrum and/or the duodenum (P < 0.05).

CONCLUSION

5-HT(1) receptor agonism increases the periodicity of the migrating motor complex and reduces the occurrence of post-prandial co-ordinated motor activity involving the gastric antrum, pylorus and duodenum.

Determinants of transpyloric fluid transport: a study using combined real-time ultrasound, manometry, and impedance recording

Intraluminal impedance recording has made it possible to record fluid transport across the pylorus during the interdigestive state without filling the stomach. During antral phase II, fluid transport occurs with and without manometrically detectable antral contraction. Our aim was to investigate the relationships between ultrasonographic patterns of antral contraction, manometric pressure waves, and transpyloric fluid transport during antral phase II. Antral wall movements were recorded by real-time ultrasound (US) in eight healthy volunteers (mean age 24 +/- 7 yr) during 17 +/- 5 min of antral phase II. Concomitantly, a catheter positioned across the pylorus, monitored by transmucosal potential difference measurement, recorded five impedance signals (1 antral, 1 pyloric, and 3 duodenal) and six manometric signals (2 antral, 1 pyloric, and 3 duodenal). Antral contractions detected by US at the level of the two antral impedance electrodes were classified according to their association with a pyloric opening or a duodenal contraction. Transpyloric liquid transport events (impedance drop of >40% of the baseline with an antegrade or retrograde propagation) and manometric pressure waves (amplitude and duration) were identified during the whole study and especially during each period of US antral contraction. A total of 110 antral contractions was detected by US. Of these, 79 were also recorded by manometry. Fluid transport across the pylorus was observed in 70.9% of the US-detected antral contractions. Pyloric opening was observed in 98.6% of the contractions associated with fluid transport compared with 50% in the absence of fluid transport (P < 0.05). Antral contractions associated with fluid transport were significantly (P < 0.05) more often propagated to the duodenum (92%) than those without fluid transport (53%). Pressure waves associated with fluid transport were of higher amplitude (208 mmHg, range 22-493) and longer duration (7 s, range 2.5-13.5 s) than those not associated with fluid transport (102 mmHg, range 18-329 mmHg, and 4.1 s, range 2-8.5 s; P < 0.05). The propagation of the antral contractions in the duodenum in US was always associated with a pyloric opening, whereas only 8 of the 25 contractions without duodenal propagation were associated with a pyloric opening (P < 0.05). The presence of duodenal contractile activity before the onset of an antral contraction in US was always accompanied by pyloric opening and with fluid transport in 93.3%, compared with 56.8% in its absence (P < 0.05). In antral phase II, US is the most sensitive technique to detect antral contractions. Transpyloric fluid transport observed in relation to antral contractions occurs mainly in association with contractions of high amplitude and long duration and is associated with pyloric opening and/or duodenal propagation.

Effect of Helicobacter pylori eradicated therapy on water gastric emptying in patients with active duodenal ulcer

BACKGROUND AND AIMS

It remains debatable if duodenal ulcer (DU) or Helicobacter pylori infection has a definite impact on human gastric emptying (GE). We explored the nature of water GE in active DU patients before and after ulcer healing and the influence of H. pylori eradication on GE.

METHODS

A home made applied potential tomography (APT) was used to measure liquid GE. Twelve electrodes were placed in a circular array around the upper abdomen of studied subjects. After drinking 500 mL of ion-free water, paired electrodes injected electrical current and the remaining 10 electrodes recorded signals, one-by-one in a rotating order. Based on tomographical calculation, the serial changes of averaged signals from altered resistivities were constructed to display GE. Initially, 64 H. pylori infected active DU patients were enrolled. After APT measurement, one-week triple therapy (omeprazole, amoxicillin and clarithromycin) was dispensed. Patients were asked back to determine ulcer/H. pylori status and GE on a scheduled date 3 months later. Finally, 58 patients finished the trial with valid and readable GE data obtained.

RESULTS

The ulcer healing and H. pylori eradicated rates were 91.4% and 82.8%, respectively. In general, liquid GE was prolonged in all DU patients at follow up. Of 48 eradicated patients, 35.4% manifested either enhanced or delayed GE before treatment, whereas only five (10.4%) had abnormal GE after treatment (P < 0.0001). In contrast, this characteristically normalized GE was not found in non-eradicated patients.

CONCLUSIONS

Water GE of active DU patients ranges from enhanced to delayed, while an effective H. pylori triple therapy is useful not only for healing ulcers, but also for restoring abnormal GE.

Interdigestive transpyloric fluid transport assessed by intraluminal impedance recording

Our aim was to explore the use of intraluminal impedance recording for assessment of interdigestive transpyloric fluid movements. Twenty healthy volunteers were studied with a catheter allowing the recording of five antropyloroduodenal impedance signals simultaneously with six pressure signals. Patterns induced by air were verified by standard ultrasound. Transpyloric Doppler ultrasound was used to validate impedance patterns associated with transpyloric fluid transports. Impedance changes caused by air (short-lived increases) occupied 14 +/- 12% of the time in the antrum and 0.8 +/- 0.5% in the duodenum (P < 0.005). All fluid transport events lasting >4 s were recorded by both Doppler and impedance techniques. Transpyloric fluid transport was observed in all three phases of the antral migrating motor complex. The total number of transport events was significantly higher (P < 0.05) in phase II (18 +/- 7) than in phases I (2.6 +/- 2) and III (6.1 +/- 3). Retrograde transport was observed mainly in antral phase I (54% of fluid movements, compared with 2.5% in phase II and 18.5% in phase III, P < 0.05). During phase II, 80 +/- 13% of the impedance changes were associated with manometric events and 72 +/- 9% of the antral contractions were associated with transpyloric fluid transport. Prolonged assessment of interdigestive transpyloric fluid transport events using intraluminal measurement of impedance is possible. Manometrically detectable contractions are the most frequent, but not the only, driving forces of these events.

Physiology of the aerodigestive system and aberrations in that system resulting in aspiration

BACKGROUND

Aspiration pneumonia remains a significant and often devastating problem in critically ill patients. It is unclear whether aspiration pneumonia occurs because of problems in the handling of oropharyngeal secretions or if the reflux of gastric contents is the major etiological factor. Additionally, the obvious breakdown of upper aerodigestive protective mechanisms in the critically ill patient population is largely unstudied. Finally, the impact and contribution of tubes, both endotracheal and nasoenteral, on aspiration pneumonia is unclear.

METHODS

A Medline literature search on scientific and review articles concerning the normal physiology of the aerodigestive tract and factors that compromised normal physiology was undertaken. Readings were supplemented by expert outside opinion from researchers in these fields and from the combined expertise from a multidisciplinary panel of experts assembled at a recent summit on aspiration pneumonia.

RESULTS

Changes in the normal physiology of the aerodigestive tract are vast and varied and dependent on the response to injury, iatrogenic interventions, and the use of nasoenteral and endotracheal tubes. The effects on gastric and esophageal motility are likely dynamic and represent an ongoing but changing risk of reflux for the patient. Nasoenteral and endotracheal tubes likely compromise upper aerodigestive protective mechanisms.

CONCLUSIONS

More research is needed on the functioning of the aerodigestive protective mechanisms in critically ill patients. Understanding of the dynamic changes in gastrointestinal motility will also be an important factor to decrease the incidence of aspiration pneumonia in this patient population.

Postprandial hypotension in response to duodenal glucose delivery in healthy older subjects

Postprandial hypotension occurs frequently in older people and may lead to syncope and falls. Some recent studies suggest that the magnitude of the postprandial fall in blood pressure (BP) is influenced by the rate of gastric emptying. The aim of this study was, therefore, to determine whether the fall in blood pressure induced by intraduodenal glucose is influenced by the rate of nutrient delivery into the small intestine, bypassing the effects of gastric emptying. Eight healthy elderly subjects (four male and four female, age 70.3 +/- 3.4 years) were studied on two separate days, in double-blind, randomised order. Glucose was infused intraduodenally at a rate of either 1 or 3 kcal min(-1), for 60 min, (0-60 min) followed by 0.9 % saline for a further 60 min (60-120 min). Blood pressure and heart rate were recorded at baseline and every 3 min during the study. Blood glucose and plasma insulin were also determined. Only the 3 kcal min(-1) infusion caused a significant fall in systolic (P < 0.001) and diastolic (P < 0.0001) blood pressure and an increase in the heart rate (P < 0.0001). The rises in blood glucose (P < 0.01) and plasma insulin (P < 0.05) concentrations were greater during the 3 kcal min(-1) infusion. We conclude that in healthy older subjects, the magnitude of the fall in blood pressure and increase in heart rate induced by intraduodenal glucose infusion is dependent on the rate of nutrient delivery into the small intestine. These results may have relevance to the treatment of postprandial hypotension.

Gastric emptying in diabetes: clinical significance and treatment

The outcome of recent studies has led to redefinition of concepts relating to the prevalence, pathogenesis and clinical significance of disordered gastric emptying in patients with diabetes mellitus. The use of scintigraphic techniques has established that gastric emptying is abnormally slow in approx. 30-50% of outpatients with long-standing Type 1 or Type 2 diabetes, although the magnitude of this delay is modest in many cases. Upper gastrointestinal symptoms occur frequently and affect quality of life adversely in patients with diabetes, although the relationship between symptoms and the rate of gastric emptying is weak. Acute changes in blood glucose concentration affect both gastric motor function and upper gastrointestinal symptoms. Gastric emptying is slower during hyperglycaemia when compared with euglycaemia and accelerated during hypoglycaemia. The blood glucose concentration may influence the response to prokinetic drugs. Conversely, the rate of gastric emptying is a major determinant of post-prandial glycaemic excursions in healthy subjects, as well as in Type 1 and Type 2 patients. A number of therapies currently in development are designed to improve post-prandial glycaemic control by modulating the rate of delivery of nutrients to the small intestine.

Low antroduodenal pressure gradients are responsible for gastric emptying of a low-caloric liquid meal in humans

The motor mechanisms responsible for transpyloric flow of gastric contents are still poorly understood. The aim of our study was to investigate the relationship between luminal pressures and gastric wall motion and between gastroduodenal pressure gradients and pressure waves, and ante- and retro-grade transpyloric flow. In eight healthy volunteers, intraluminal pressures were recorded from the antrum and proximal duodenum. Transpyloric flow was monitored simultaneously using duplex ultrasonography, before, during and after ingestion of 300 mL meat soup. Transpyloric emptying occurred as sequences of alternating periods of emptying-reflux-emptying. Approximately one-third of the sequences were not associated with peristalsis. The antroduodenal pressure gradients were significantly lower during nonperistaltic-related emptying than during peristaltic-related emptying (0.15 (0-0.3) kPa, and 1.7 (0.2-2.0) kPa, respectively [mean plus minus (range)], P < 0.005). The duration of emptying episodes not associated with peristalsis were significantly longer than those associated with peristalsis at (6.5 (3-8.7) s and 4.4 (2-6) s, respectively, P=0.059). Manometry detected only 56% of the antral contractions seen on ultrasound. We concluded that gastric emptying of a low-calorie liquid meal occurs both during peristaltic and nonperistaltic antral activity. In spite of lower antroduodenal pressure gradients, the emptying episodes were longer for nonperistaltic emptying, which is likely to be caused by low pyloric resistance. Considerable flow seems to occur without peristalsis during gastric emptying of a low-calorie, liquid meal in humans.

Antropyloroduodenal, cholecystokinin and feeding responses to pulsatile and non-pulsatile intraduodenal lipid infusion

The contribution of the pulsatile nature of gastric emptying to small intestinal feedback mechanisms modulating antropyloroduodenal motility and appetite is unknown. On separate days, eight healthy male volunteers (18-34 years) received randomized, single-blind, intraduodenal (ID) infusions of 10% Intralipid (2 kcal min(-1)), either continuously [CID], or in a pulsatile manner [PID] (5 s on/15 s off) and 0.9% saline (control) administered continuously, each at a rate of 1.8 mL min(-1) for 3 h. During each infusion, subjective ratings of appetite were assessed and antropyloroduodenal pressures recorded with a 16-lumen manometric assembly incorporating a pyloric sleeve sensor. Plasma cholecystokinin was measured from blood collected at regular intervals throughout the infusion. At the end of each infusion the manometric assembly was removed, subjects were offered a buffet meal and the energy and macronutrient content of the meal was measured. Both ID lipid infusions stimulated isolated pyloric pressure waves (IPPWs) (P < 0.001) and basal pyloric pressure (P < 0.01) and suppressed antral (P < 0.05) and duodenal (P < 0.05) pressure waves when compared to controls; there was no difference in the effects of CID and PID lipid on antropyloroduodenal pressures. Infusions of lipid significantly increased plasma CCK concentrations (P < 0.05) compared with saline, but concentrations were not different between the two modes of lipid delivery (P > 0.05, CID vs. PID). Both intraduodenal lipid infusions decreased hunger (P < 0.05), increased fullness (P < 0.05) and reduced energy intake (P < 0.05) when compared with controls; again there was no difference between CID and PID lipid. We conclude that at the infusion rate of similar 2 kcal min(-1), the acute effects of intraduodenal lipid on antropyloroduodenal pressures, plasma CCK concentration and appetite are not modified by a pulsatile mode of lipid delivery into the duodenum.

Pressure-geometry relationship in the antroduodenal region in humans

Understanding of the control mechanisms underlying gastric motor function is still limited. The aim of the present study was to evaluate antral pressure-geometry relationships during gastric emptying slowed by intraduodenal nutrient infusion and enhanced by erythromycin. In seven healthy subjects, antral contractile activity was assessed by combined dynamic magnetic resonance imaging and antroduodenal high-resolution manometry. After intragastric administration of a 20% glucose solution (750 ml), gastric motility and emptying were recorded during intraduodenal nutrient infusion alone and, subsequently, combined with intravenous erythromycin. Before erythromycin, contraction waves were antegrade (propagation speed: 2.7 +/- 1.7 mm/s; lumen occlusion: 47 +/- 14%). Eighty-two percent (51/62) of contraction waves were detected manometrically. Fifty-four percent of contractile events (254/473) were associated with a detectable pressure event. Pressure and the degree of lumen occlusion were only weakly correlated (r(2) = 0.02; P = 0.026). After erythromycin, episodes of strong antroduodenal contractions were observed. In conclusion, antral contractions alone do not reliably predict gastric emptying. Erythromycin induces strong antroduodenal contractions not necessarily associated with fast emptying. Finally, manometry reliably detects ~80% of contraction waves, but conclusions from manometry regarding actual contractile activity must be made with care.

Quantification of gastric emptying and duodenogastric reflux stroke volumes using three-dimensional guided digital color Doppler imaging

OBJECTIVE

To develop a non-invasive method for evaluating gastric emptying and duodenogastric reflux stroke volumes using three-dimensional (3D) guided digital color Doppler imaging.

METHODS

The technique involved color Doppler digital images of transpyloric flow in which the 3D position and orientation of the images were known by using a magnetic location system.

RESULTS

In vitro, the system was found to slightly underestimate the reference flow (by average 8.8%). In vivo (five volunteers), stroke volume of gastric emptying episodes lasted on average only 0.69 s with a volume on average of 4.3 ml (range 1.1-7.4 ml), and duodenogastric reflux episodes on average 1.4 s with a volume of 8.3 ml (range 1.3-14.1 ml).

CONCLUSION

With the appropriate instrument settings, orientation determined color Doppler can be used for stroke volume quantification of gastric emptying and duodenogastric reflux episodes.

Duodenal vs. gastric administration of labeled leucine for the study of splanchnic metabolism in humans

Low-rate (6 ml/h) intragastric infusion of stable, isotope-labeled amino acids is commonly used to assess the splanchnic handling of amino acids in humans. However, when used in the postabsorptive state, this method yields unreliable plasma isotopic enrichments, with a coefficient of variation >10%. In this metabolic condition, we confirmed in six subjects that an intragastric infusion of L-[(2)H(3)]leucine at 6 ml/h yields an unreliable isotopic steady state in plasma amino acids with a coefficient of variation of 43 +/- 12% (mean +/- SD). In five additional subjects, we assessed the effects of 1) increasing the rate of delivery of a leucine tracer in an isotonic plasmalike solution at 240 ml/h into the gastric site, and 2) changing the site of infusion from gastric to duodenal with this same high rate of delivery. In contrast to the gastric route, and regardless of the rate of delivery, only the intraduodenal route allowed 1) isotopic plasma steady state (i.e., coefficients of variation were <10%: 5 +/- 3%), and 2) reproducible leucine extraction coefficients (22 +/- 5%). We conclude that an infusion site that bypasses the gastric emptying process, i.e., the duodenal route, along with delivery of a plasmalike solution, is necessary to reach isotopic steady state in plasma when labeled leucine is infused into the gastrointestinal tract in the postabsorptive state.

Metabolic acidosis and respiratory acidosis impair gastro-pyloric motility in anesthetized pigs

Acidosis impairs smooth muscle function in various organs. However, the effects of acidosis on the gastroduodenal tract are unknown while its dysfunction has potential perioperative harmful consequences. We investigated the effects of metabolic (MA) and respiratory acidosis (RA) on upper gut motility in tracheally ventilated pigs whose anesthesia was induced with halothane and maintained with alpha-chloralose-urethane administration (IV). Increased dead space and perfusion of hydrochloric acid 1 N (150 mL over 30 min) were used to induce RA and MA, respectively. Measurements of fundic tone using an electronic barostat, antro-pyloroduodenal phasic motility with perfused manometry and antro-duodenal electric control activity by electromyography were used to evaluate gastroduodenal function. Acidosis increased the fundic tone as reflected by a decrease in barostat volumes from 275+/-83 to 194+/-88 mL for MA and from 278+/-93 to 236+/-106 mL for RA. Pyloric and duodenal basal tones were not affected by either acidosis. A decrease in pyloric contraction amplitude from 95+/-24 to 62+/-26 mm Hg during MA and from 94+/-26 to 64+/-20 mm Hg during RA was observed. Both acidosis altered antral control activity that became dysrhythmic. Acidosis could be implicated in perioperative complications, such as gastroparesis, emesis, and regurgitation of gastric contents.

IMPLICATIONS

Metabolic and respiratory acidosis mainly affects gastric antral rhythms and has a major effect on fundic tone. Acidosis could be implicated in perioperative complications, such as gastroparesis, emesis, and regurgitation of gastric contents.

Long-term effects of pyloromyotomy on pyloric motility and gastric emptying in humans

OBJECTIVE

The aim of this study was to determine the long term effects of pyloromyotomy for infantile hypertrophic pyloric stenosis (IHPS) on gastric emptying and pyloric motility.

METHODS

Concurrent measurements of gastric emptying and antropyloroduodenal pressures were performed in six volunteers (aged 24-26 yr) who had had pyloromyotomy performed in infancy because of IHPS, and in six normal subjects. Subjects were studied on 2 days, once sitting and once in the left lateral position. Gastric emptying of 300 ml 25% dextrose labeled with 20 MBq 99mTc sulfur colloid was measured. Antropyloroduodenal motility was evaluated with a sleeve/multiple sidehole manometric assembly, which was also used to deliver an intraduodenal triglyceride infusion at 1.1 kcal/min for 60 min, starting 30 min after ingestion of the dextrose.

RESULTS

In both body positions, gastric emptying and intragastric distribution of the drink did not differ between the two groups. In both groups and postures, the amount emptied was less during intraduodenal lipid infusion. The number (p<0.01) and amplitude (p<0.02) of isolated pyloric pressure waves (IPPWs) was greater in the control subjects, whereas basal pyloric pressure was greater in the pyloromyotomy subjects (p<0.02). In both groups, the rate of gastric emptying in the sitting position was related to the number of IPPWs (r> or =0.40, p<0.05), but not to basal pyloric pressure.

CONCLUSIONS

These results indicate that, in adults who have had pyloromyotomy for IHPS in infancy, patterns of pyloric motility are abnormal; pyloric tone is higher, whereas the number and amplitude of phasic pyloric pressure waves are less. In contrast, the overall rate of gastric emptying of a nutrient liquid meal is normal. These observations are consistent with the concept that the stomach has the capacity to compensate for changes in pyloric motility to minimize effects on gastric emptying.

Effects of promethazine on porcine gastroduodenal function: a sonographic study

This sonographic study was aimed at examining the effect of sedation with promethazine (1.5 mg x kg(-1)), on gastroduodenal function in neonatal piglets. On 3 consecutive days, observations of gastroduodenal motility during the first 3 postprandial h were made in 13 animals (3 to 5 days old; 7 sleeping naturally and 6 sedated 2 h prior to feeding). Promethazine significantly reduced both the closures per min of the terminal part of the pyloric antrum and pyloric canal and the percentage of gastric contractions that were followed by closure of the terminal pyloric antrum and canal. Such actions of promethazine on motility of the gastroduodenal junction could lead to a delay in gastric emptying of ingesta with a consequent increased risk of reflux of gastric contents into the esophagus. Because gastroesophageal reflux has been associated with the pathogenesis of sudden infant death syndrome (SIDS), care should be taken if promethazine is to be used as a sedative in neonates.

Antro-pyloric contractile patterns and transpyloric flow after meal ingestion in humans

OBJECTIVE

The present study aimed to evaluate the patterns of antral contractility and pylorus opening and closure in relation to transpyloric flow of a nutrient liquid meal.

METHODS

Ultrasound images of the antro-pyloro-duodenal tract were continuously tape-recorded in healthy volunteers for 1 h postprandially and were reviewed twice later by independent observers. Episodes and patterns of pylorus opening and closure, antral-wall contractions, and transpyloric flow were assessed separately and their time relations were identified.

RESULTS

Transpyloric flow (forward, 56%+/-13%; retrograde, 19%+/-11%; and to and fro, 25%+/-14%) occurred essentially during episodes of prolonged pylorus opening not associated with occlusive antral or duodenal proximal contraction, which represented the antro-pyloro-duodenal common chamber. The antro-pyloro-duodenal common chamber lasted on average 36+/-12 s and represented 41%+/-12% of the total observation period. Different patterns of antral contractions were identified according to whether they reached or occluded the terminal antrum and pylorus. Preterminal antral contractions (46%+/-12%) did not propagate beyond the proximal two thirds of the antrum. Terminal antral contractions (54%+/-12%) propagated along the entire antrum and could either occlude (20%+/-9%) or not occlude (42%+/-17%) the lumen. Pyloric opening independent of antral contractions and related to nonocclusive antral contractions could occur equally at the onset of the antro-pyloro-duodenal common chamber. Pyloric closure independent of antral contractions put an end to transpyloric flow in 73%+/-6% of the antro-pyloro-duodenal common chamber.

CONCLUSIONS

The final passage of contents from the stomach to the duodenum after the ingestion of a caloric liquid meal is the result of one or more episodes of uni- or bi-directional transpyloric flow, which are regulated by several motor events. The contractile states of the antrum and pylorus show specific features that variably interrelate to provide mixing and to regulate the transpyloric flow of ingesta. A crucial regulator of transpyloric flow appears to be the spatio-temporal relation between antral contractions and pyloric closure rather than the contractile events per se. An equal number of pyloric openings related, and unrelated, to antral contractions appears to determine the onset of the antro-pyloro-duodenal common chamber and, thus, of transpyloric flow. Pyloric closure unrelated to antral contractions appears to be the main mechanism that interrupts transpyloric flow. In conclusion, it appears that the antro-pyloro-duodenal tract acts as a functional unit in the digestion of a liquid caloric meal.

Effects of nitroglycerin on liquid gastric emptying and antropyloroduodenal motility

The effects of the nitric oxide donor nitroglycerin on gastric emptying and antropyloroduodenal motility were evaluated in nine healthy male subjects (ages 19-36 yr). Antropyloroduodenal pressures were recorded with a manometric assembly that had nine side holes spanning the antrum and proximal duodenum and a pyloric sleeve sensor; gastric emptying was quantified scintigraphically. In each subject, the emptying of 300 ml of 25% glucose labeled with 99mTc was assessed on two separate days during intravenous infusion of either nitroglycerin (5 micrograms/min in 5% dextrose) or 5% dextrose (control). Studies were performed with the subject in the supine position; blood pressure and heart rate were monitored. Nitroglycerin had no significant effect on blood pressure or heart rate. Nitroglycerin slowed gastric emptying (P < 0.02), and this was associated with greater retention of the drink in the proximal stomach (P < 0.05). In both nitroglycerin and control studies, ingestion of the drink was associated with an increase in the number of isolated pyloric pressure waves (P < 0.05) and antral pressure wave sequences (P < 0.05). Nitroglycerin reduced the number of isolated pyloric pressure waves (P < 0.05), basal pyloric pressure (P < 0.05), and the number of antral pressure wave sequences (P < 0. 05), but not the total number of antral pressure waves. The rate of gastric emptying and the number of isolated pyloric pressure waves were inversely related during control (P = 0.03) and nitroglycerin (P < 0.05) infusions. We conclude that in normal subjects, 1) gastric emptying of 300 ml of 25% glucose is inversely related to the frequency of phasic pyloric pressure waves, and 2) nitroglycerin in a dose of 5 micrograms/min inhibits pyloric motility, alters the organization but not the number of antral pressure waves, and slows gastric emptying and intragastric distribution of 25% glucose.

Sonographic observations of the gastroduodenal junction in neonatal piglets

Knowledge of the function of the gastroduodenal junction is important, as changes in its motility are associated with gastrointestinal disorders. Sonographic observations were made of the stomach and duodenum of 19 neonatal piglets, 2-6 d of age. Contractions of the stomach and duodenum were identified clearly; the overall rate of gastric contractions was about 4 min-1. The percentage of contractions in which there was a closure of the terminal pyloric antrum and pyloric canal varied, being 57.2% +/- 4.6% in the first postprandial hour and 43.1% +/- 3.0% in the third. Antegrade flow of digesta principally occurred preceding a closure of the pyloric antrum and canal. During contractions of the pyloric antrum, the torus pyloricus moved caudally to fill the lumen of the pyloric canal. Our sonographic method provided a noninvasive technique for studying the form and function of gastroduodenal motility in the neonate, suitable for investigating factors that alter gastric emptying.

Changes in pyloric resistance induced by erythromycin

Erythromycin increases gastric emptying but the characteristics of transpyloric flow and the contribution of pyloric resistance to the mechanisms of increased flow are unknown. Transpyloric outflow and gastroduodenal pressures were studied in eight anaesthetized pigs during intravenous infusion of erythromycin (10 mg kg-1). Erythromycin increased emptying of saline through an increased stroke volume of individual flow pulses (13.7 +/- 1.24 vs. 3.6 +/- 1.30 mL) rather than by decreasing the interval between flow pulses (3.9 +/- 0.55 vs. 3.2 +/- 0.30 pulse.min-1). This flow pattern was associated with more frequent antral contractions of larger amplitude originating from the upper part of the gastric antrum, suppression of isolated pyloric pressure waves and significant reduction of the pyloric resistance to flow (2.3 +/- 0.21 vs. 4.6 +/- 0.46 mmHg mL-1 s-1). The decreased resistance originated from a different temporal relationship between antropyloric pressure event and flow pulses that occurred almost simultaneously during erythromycin.

Erythromycin gastrokinetic activity is partially vagally mediated

Erythromycin overcomes postvagotomy gastroparesia in patients without a distal stomach and functional pylorus. We investigate the role of the vagus in gastric emptying increased by erythromycin, using a model that preserves the physiology of the distal stomach and pylorus. The effects of erythromycin lactobionate (10 mg/kg) on transpyloric flow pattern and pyloric resistance were evaluated during repetitive bilateral vagal cooling in anesthetized pigs. Vagal cooling during erythromycin infusion produced a marked decreased of pyloric outflow (23 +/- 1.1 vs 50 +/- 2.6 ml/min) related to a reduced stroke volume of the flow pulses (7.8 +/- 3.31 vs. 14.1 +/- 2.44 ml). The amplitude and frequency of gastric and duodenal pressure events were unchanged or slightly reduced during vagal cooling. The smaller stroke volume of flow pulse was the consequence of increased pyloric resistance (6.2 +/- 1.98 vs. 2.3 +/- 0.21 mmHg.ml-1.s), which is associated with changes in the temporal relationship between a pyloric pressure event and flow pulse. In conclusion, erythromycin activity on the pylorus requires the integrity of vagal pathways. Enhancement of gastric outflow by erythromycin is also modulated by the vagus, since pyloric resistance was able to overcome increased gastric motility.

Interstitial cells of Cajal as targets for pharmacological intervention in gastrointestinal motor disorders

Interstitial cells of Cajal (ICCs) have recently been identified as the pacemaker cells for contractile activity of the gastrointestinal tract. These cells generate the electrical 'slow-wave' activity that determines the characteristic frequency of phasic contractions of the stomach, intestine and colon. Slow waves also determine the direction and velocity of propagation of peristaltic activity, in concert with the enteric nervous system. Characterization of receptors and ion channels in the ICC membrane is under way, and manipulation of slow-wave activity markedly alters movement of contents through the gut organs. Here Jan Huizinga, Lars Thuneberg, Jean-Marie Vanderwinden and Jüri Rumessen, suggest that, as ICCs are unique to the gut, they might be ideal targets for pharmacological intervention in gastrointestinal motility disorders, which are very common and costly.

Spatial patterns of fasting and fed antropyloric pressure waves in humans

1. Gastric mechanics were investigated by categorizing the temporal and spatial patterning of pressure waves associated with individual gastric contractions. 2. In twelve healthy volunteers, intraluminal pressures were monitored from nine side hole recording points spaced at 1.5 cm intervals along the antrum, pylorus and duodenum. 3. Pressure wave sequences that occurred during phase II fasting contractions (n = 221) and after food (n = 778) were evaluated. 4. The most common pattern of pressure wave onset along the antrum was a variable combination of antegrade, synchronous and retrograde propagation between side hole pairs. This variable pattern accounted for 42% of sequences after food, and 34% during fasting (P < 0.05). Other common pressure wave sequence patterns were: purely antegrade-29% after food and 42% during fasting (P < 0.05); purely synchronous-23% fed and 17% fasting; and purely retrograde-6% fed and 8% fasting. The length of sequences was shorter after food (P < 0.05). Some sequences 'skipped' individual recording points. 5. The spatial patterning of gastric pressure wave sequences is diverse, and may explain the differing mechanical outcomes among individual gastric contractions. 6. Better understanding of gastric mechanics may be gained from temporally precise correlations of luminal flows and pressures and gastric wall motion during individual gastric contraction sequences.

Scintigraphic measurement of gastric emptying and ultrasonographic assessment of antral area: relation to appetite

BACKGROUND

Ultrasound measurement of gastric emptying has potential advantages over scintigraphy, but there is little information about its accuracy.

AIMS

The relation between ultrasonographic measurements of antral area and (a) scintigraphic measurements of gastric emptying and intragastric distribution of liquids (b) postprandial satiation, were evaluated.

SUBJECTS

Seven normal volunteers were studied.

METHOD

Each subject drank 75 g dextrose dissolved in 350 ml of water (300 kcal) or beef soup (20 kcal), both labelled with technetium-99m sulphur colloid on separate days and had measurement of gastric emptying by scintigraphy and ultrasound.

RESULTS

Scintigraphic and ultrasound 50% emptying times (T50s) were comparable and longer (p < 0.001) for dextrose than soup mean (SEM) (dextrose 107 (16) min v 108 (18) min, soup 24 (4) min v 23 (5) min). There were close correlations between scintigraphic and ultrasound T50s (dextrose r = 0.94, p < 0.005, soup r = 0.97, p < 0.001) and between the time at which the distal stomach content decreased from its maximum value by 50% (measured scintigraphically) and the ultrasound T50 (dextrose r = 0.95, p < 0.005, soup r = 0.99, p < 0.0001). In contrast, there was no significant relation between the distal stomach content when expressed as a percentage of the maximum content in the total stomach and the ultrasound T50. After dextrose, fullness was related (r = 0.92, p < 0.01) to the postprandial increase in antral area measured by ultrasound.

CONCLUSIONS

Ultrasound measurements of gastric emptying are: (a) of comparable sensitivity to scintigraphy in quantifying emptying of both low and high nutrient liquids (b) correlate with postprandial satiation, suggesting that the latter may be mediated by antral distension.

Effects of cisapride on gastric emptying of oil and aqueous meal components, hunger, and fullness

To evaluate the effects of cisapride on gastric emptying of extracellular fat and hunger and fullness 10 volunteers consumed a meal consisting of 60 ml technectium-99m (99mTc)-V-thiocyanate labelled olive oil and 290 ml indium-113m (113mIn) labelled soup after taking cisapride (10 mg four times daily orally) and placebo, each for four days, in randomised, double blind fashion. Gastric emptying was quantified scintigraphically. Hunger and fullness before and after the meal were evaluated using visual analogue scales. Cisapride accelerated gastric emptying of oil and aqueous components by reducing the lag phase mean (SEM) (20.3 (7.0) min v 40.7 (4.1) min (p < 0.05) for oil and 4.1 (2.5) min v 10.0 (3.1) min (p < 0.05) for aqueous). Cisapride had no effect on the post-lag emptying rate of oil. Treatment with cisapride was associated with reduced retention of oil in the proximal stomach (p < 0.05). Subjects were more hungry before ingestion of the meal while receiving cisapride (6.7 (0.9) v 3.9 (0.7), p < 0.001). The scores for hunger at 120 and 180 minutes were inversely related to gastric emptying of oil on both cisapride (r > -0.62, p < 0.05) and placebo (r > -0.86, p < 0.001). Fullness increased after the meal while receiving placebo (p < 0.01), but not cisapride and postprandial fullness was less with cisapride at (30 min; 0.4 (0.3) v 3.3 (1.0), p < 0.05). With placebo, but not cisapride, the score for fullness at 15 minutes was inversely related to emptying of the aqueous phase (r = 0.68, p < 0.05). These results show that in normal volunteers after ingestion of an oil/aqueous meal: (a) postprandial hunger is inversely related to gastric emptying of oil, while fullness is inversely related to gastric emptying of the aqueous phase, (b) cisapride affects the intragastric distribution and accelerates gastric emptying of both oil and aqueous meal components, and (c) cisapride increases preprandial hunger and reduces postprandial fullness.

Evaluation of antral motility in humans using manometry and scintigraphy

Recent studies suggest that scintigraphy can be used to evaluate non-invasively antral motility in humans, although scintigraphic techniques have not yet been compared with more conventional measurements of intraluminal pressures by manometry. Simultaneous scintigraphic and manometric measurements of antral motility were performed in nine healthy volunteers. After intubation with a sleeve/sidehole catheter which incorporated five pressure sideholes located at 1.5 cm intervals spanning the antrum, each subject ingested 100 g minced beef labelled with 100 MBq 99mTc-chicken liver and 150 ml water. Between 40-43, 60-63, 80-83, and 100-103 minutes after meal ingestion, radioisotopic data were acquired in two second frames. Time-activity curves showing antral 'contractions' resulting from wall motion were derived by drawing small regions of interest over the antrum to coincide with the position of the antral manometric sideholes. Scintigraphic contraction rates approximated 3/minute, whereas antral pressure waves that occluded the lumen were less frequent (p < 0.01 for all), particularly in the proximal antrum. The amplitude of wall motion, evaluated scintigraphically, and the amplitude of pressure waves were both inversely related to the distance from the pylorus (r > -0.32, p < 0.05) and antral volume r > -0.29 (p < 0.05). There were significant relationships between the amplitude of contractions assessed scintigraphically and the number of lumen-occlusive antral pressure waves in the distal antrum (r -0.48, p < 0.05) but not in the more proximal antral regions. It is concluded that scintigraphy can detect antral wall motion with greater sensitivity than manometry, particularly in the proximal antrum. As manometry gives information on the amplitude as well as the temporal and spatial organisation of those contractions which result in lumen occlusion, the combination of scintigraphic and manometric techniques in the evaluation of antral motility shows considerable promise.