Effects of posture on gastric emptying and satiety ratings after a nutritive liquid and solid meal

Bridging the Gap between Food Effects under Clinical Trial Conditions and Real Life: Modeling Delayed Gastric Emptying of Drug Substances and Gastric Content Volume Based on Meal Characteristics

Delayed gastric emptying is known to have a major impact on drug absorption. While the test meal recommended by the FDA and EMA to study food effects represents a worst-case scenario, it does not reflect the reality of the patients. Physiologically based pharmacokinetic (PBPK) models could bridge the gap between clinical settings of food effect studies and the diverse nonclinical situations by simulating the effect of meals with different compositions and volumes. A mathematical equation based on a stretched exponential function was reparameterized to describe the gastric emptying process of mixed solid meals. The model was fitted to literature data including the gastric emptying data of 23 meals from 15 studies. Using a multiple linear regression model, we were able to predict the two function parameters from the meal characteristics caloric content and the percentage of calories derived from fat. After implementation into the PBPK software PK-Sim, the model, together with a separate compartment for liquid gastric contents, was compared to commercially available software. The model is able to simulate the gastric emptying of mixed solid meals containing drugs based on specific meal characteristics. A second compartment allows for distribution between liquid and solid components and rapid gastric emptying along the Magenstrasse.

Study on the effects of different postprandial positions on blood pressure and heart rate in older adults with primary hypertension and postprandial hypotension

This randomized controlled trial explored the effects of a supine position or a semi-fowler position on postprandial blood pressure (BP) of older adults with primary hypertension and postprandial hypotension (PPH). Ninety-six participants were divided into the supine group, the semi-fowler group, and the control group with block-randomization. After a meal, the patients were placed in a supine position, a 45° semi-fowler position, or allowed daily activities, respectively. BP, heart rate and PPH symptoms were measured 5 times in 120 minutes after the meal. Repeated measurement analysis showed no statistical difference in BP, heart rate and PPH symptom scores among the three groups. BP in all groups decreased rapidly at the 30-minute point, and then moved steadily downward. Taking a supine position or semi-fowler position after meals had no effect on postprandial BP and heart rate after meals in older adults with hypertension and PPH.

Formulation strategies to improve the efficacy of intestinal permeation enhancers. Adv Drug Deliv Rev 2021;177:113925. [PMID: 34418495 DOI: 10.1016/j.addr.2021.113925]

The use of chemical permeation enhancers (PEs) is the most widely tested approach to improve oral absorption of low permeability active agents, as represented by peptides. Several hundred PEs increase intestinal permeability in preclinical bioassays, yet few have progressed to clinical testing and, of those, only incremental increases in oral bioavailability (BA) have been observed. Still, average BA values of ~1% were sufficient for two recent FDA approvals of semaglutide and octreotide oral formulations. PEs are typically screened in static in vitro and ex-vivo models where co-presentation of active agent and PE in high concentrations allows the PE to alter barrier integrity with sufficient contact time to promote flux across the intestinal epithelium. The capacity to maintain high concentrations of co-presented agents at the epithelium is not reached by standard oral dosage forms in the upper GI tract in vivo due to dilution, interference from luminal components, fast intestinal transit, and possible absorption of the PE per se. The PE-based formulations that have been assessed in clinical trials in either immediate-release or enteric-coated solid dosage forms produce low and variable oral BA due to these uncontrollable physiological factors. For PEs to appreciably increase intestinal permeability from oral dosage forms in vivo, strategies must facilitate co-presentation of PE and active agent at the epithelium for a sustained period at the required concentrations. Focusing on peptides as examples of a macromolecule class, we review physiological impediments to optimal luminal presentation, discuss the efficacy of current PE-based oral dosage forms, and suggest strategies that might be used to improve them.

Gastric Emptying and Intragastric Behavior of Breast Milk and Infant Formula in Lactating Mothers

BACKGROUND

When sufficient breast milk is not available, infant formula is often used as an alternative. As for digestion, gastric behavior of infant formula and breast milk have not been studied in detail.

OBJECTIVE

This study aimed to compare gastric emptying and intragastric behavior between breast milk and infant formula in vivo using MRI.

METHODS

In this randomized crossover study, 16 lactating mothers (age: 31.7 ± 2.9 y; time since giving birth: 9.3 ± 2 mo), underwent gastric MRI scans before and after consumption of 200 mL of infant formula or their own breast milk. MRI scans were performed after an overnight fast (baseline) and every 10 min up until 60 min following ingestion. Primary outcomes were gastric emptying measures and the secondary outcome was gastric layer volume over time. Differences between infant formula and breast milk in total gastric volume and layering volume were tested using linear mixed models.

RESULTS

Gastric emptying half-time was 5.1 min faster for breast milk than for infant formula (95% CI: -19.0 to 29.2) (n = 14). Within a subgroup (n = 12) with similar initial gastric volume (<20 mL difference), gastric emptying half-time was 20 min faster for breast milk (95% CI: 1.23-43.1). Top layer volume (n = 16) was 6.4 mL greater for infant formula than for breast milk (95% CI: 1.9-10.8). This effect is driven by t = 10 and t = 20 min postingestion.

CONCLUSIONS

When taking initial gastric volume into account, breast milk emptied faster than infant formula in women, which is in line with previous findings in infants. Infant formula showed a significantly larger top layer volume in the first 20 min after ingestion. MRI in adults may find application in studies assessing gastric behavior of infant formula.

Non-uniform gastric wall kinematics revealed by 4D Cine magnetic resonance imaging in humans

BACKGROUND

Assessment of gastric function in humans has relied on modalities with varying degrees of invasiveness, which are usually limited to the evaluation of single aspects of gastric function, thus requiring patients to undergo a number of often invasive tests for a full clinical understanding. Therefore, the development of a non-invasive tool able to concurrently assess multiple aspects of gastric function is highly desirable for both research and clinical assessments of gastrointestinal (GI) function. Recently, technological advances in magnetic resonance imaging (MRI) have provided new tools for dynamic (or "cine") body imaging. Such approaches can be extended to GI applications.

METHODS

In the present work, we propose a non-invasive assessment of gastric function using a four-dimensional (4D, volumetric cine imaging), free-breathing MRI sequence with gadolinium-free contrast enhancement achieved through a food-based meal. In healthy subjects, we successfully estimated multiple parameters describing gastric emptying, motility, and peristalsis propagation patterns.

KEY RESULTS

Our data demonstrated non-uniform kinematics of the gastric wall during peristaltic contraction, highlighting the importance of using volumetric data to derive motility measures.

CONCLUSIONS & INFERENCES

MRI has the potential of becoming an important clinical and gastric physiology research tool, providing objective parameters for the evaluation of impaired gastric function.

Men and Women Differ in Gastric Fluid Retention and Neural Activation after Consumption of Carbonated Beverages

Background

The most commonly consumed carbonated beverages are soda and beer. Carbon dioxide increases gastric volume, which can lead to epigastric discomfort. Women are more susceptible to this; however, correlations with neural activity and gastric distention are unknown.

Objective

This study sought to determine the subjective, gastric, and neural correlates of epigastric discomfort in men and women.

Methods

Thirty-four healthy, normal-weight adults [17 women; mean ± SD body mass index (BMI; kg/m2): 22.3 ± 1.9; 17 men; BMI: 22.8 ± 1.8] participated in a randomized crossover study with 2 treatments: ingestion of 500 mL beer or soda. Before and after consumption, gastric content and brain activity were measured with magnetic resonance imaging (MRI). Participants rated fullness, bloating, hunger, and nausea at baseline and at t = 0, 10, 20, and 30 min together with gastric MRI. Brain activity [cerebral blood flow (CBF)] was measured at baseline and at t = 5 and 35 min. Liquid, gas, and total gastric volume (TGV) were segmented from gastric MRI. Ratings and gastric content areas under the curve (AUCs) were tested with a mixed model with sex and drink as factors.

Results

For subjective ratings, only nausea in the beer condition scored significantly greater for women (9.4-point increase; P = 0.045). Liquid stomach content was significantly greater for women (2525 mL × min increase; P = 0.019). In both men and women, the strongest correlation for bloating was with TGV (r = 0.45, P < 0.01) and for nausea was with the liquid fraction AUC (r = 0.45, P < 0.01). CBF changes did not differ between the drinks. Men showed greater CBF than women in the left precentral and postcentral gyri at t = 5 min.

Conclusions

There are differences between sexes when it comes to appetite ratings, gastric fluid retention, and neural activation. Discomfort in women may be related to fluid rather than gas in the stomach, because they retain more fluid than men. Differences between men and women should be considered when studying digestion. This study was registered with the Dutch Trial Registry as NTR5418 (http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5418).

Empty calories and phantom fullness: a randomized trial studying the relative effects of energy density and viscosity on gastric emptying determined by MRI and satiety

BACKGROUND

Stomach fullness is a determinant of satiety. Although both the viscosity and energy content have been shown to delay gastric emptying, their relative importance is not well understood.

OBJECTIVE

We compared the relative effects of and interactions between the viscosity and energy density on gastric emptying and perceived satiety.

DESIGN

A total of 15 healthy men [mean ± SD age: 22.6 ± 2.4 y; body mass index (in kg/m(2)): 22.6 ± 1.8] participated in an experiment with a randomized 2 × 2 crossover design. Participants received dairy-based shakes (500 mL; 50% carbohydrate, 20% protein, and 30% fat) that differed in viscosity (thin and thick) and energy density [100 kcal (corresponding to 0.2 kcal/mL) compared with 500 kcal (corresponding to 1 kcal/mL)]. After ingestion, participants entered an MRI scanner where abdominal scans and oral appetite ratings on a 100-point scale were obtained every 10 min until 90 min after ingestion. From the scans, gastric content volumes were determined.

RESULTS

Overall, the gastric emptying half-time (GE t50) was 54.7 ± 3.8 min. The thin 100-kcal shake had the lowest GE t50 of 26.5 ± 3.0 min, followed by the thick 100-kcal shake with a GE t50 of 41 ± 3.9 min and the thin 500-kcal shake with a GE t50 of 69.5 ± 5.9 min, and the thick 500-kcal shake had the highest GE t50 of 81.9 ± 8.3 min. With respect to appetite, the thick 100-kcal shake led to higher fullness (58 points at 40 min) than the thin 500-kcal shake (48 points at 40 min).

CONCLUSIONS

Our results show that increasing the viscosity is less effective than increasing the energy density in slowing gastric emptying. However, the viscosity is more important to increase the perceived fullness. These results underscore the lack of the satiating efficiency of empty calories in quickly ingested drinks such as sodas. The increase in perceived fullness that is due solely to the increased viscosity, which is a phenomenon that we refer to as phantom fullness, may be useful in lowering energy intake. This trial was registered at www.trialregister.nl as NTR4573.

The role of alginates in regulation of food intake and glycemia: a gastroenterological perspective

Regulation of food intake through modulation of gastrointestinal responses to ingested foods is an ever-growing component of the therapeutic approaches targeting the obesity epidemic. Alginates, viscous and gel-forming soluble fibers isolated from the cell wall of brown seaweeds and some bacteria, are recently receiving considerable attention because of their potential role in satiation, satiety, and food intake regulation in the short term. Enhancement of gastric distension, delay of gastric emptying, and attenuation of postprandial glucose responses may constitute the basis of their physiological benefits. Offering physical, chemical, sensorial, and physiological advantages over other viscous and gel-forming fibers, alginates constitute promising functional food ingredients for the food industry. Therefore, the current review explores the role of alginates in food intake and glycemic regulation, their underlying modes of action and their potential in food applications.

Assessment of gastric emptying in children: Establishment of control values utilizing a standardized vegetarian meal

BACKGROUND AND AIM

Disorders of gastric emptying constitute an important group of conditions in children. The diagnostic gold standard is scintigraphy, and recommendations for standardization have been published with adult normative data. Pediatric literature lacks standardized age specific normative values. Our aim was to establish normal values of solid phase gastric emptying utilizing scintigraphy in children (5-18 years) using the recommended imaging protocol and standardized meal.

METHODS

Gastric emptying was assessed by scintigraphy of a (99m) Tc-labeled vegetarian meal. Image acquisition was dynamic for first hour and static at 2, 3, and 4 h. Results were reported as percent intragastric retention; lag phase defined as time to 5% emptying.

RESULTS

Thirty (17 boys) healthy children, mean ages of 9.5 ± 3.1 (range 5 to 16) years, were enrolled. Median values (5th and 95th percentiles) for percent gastric retention at 30 min, 1, 2, 3 and 4 h were 90% (76 and 100%), 77% (56 and 96%), 33% (10 and 71%), 16% (3 and 44%), and 7% (0.5 and 22%). The median (5th and 95th percentiles) lag phase was 18 min (6 and 60 min). Lag phase had no correlation with gastric retention at 4 h.

CONCLUSIONS

This study provides valuable normative ranges for solid phase gastric emptying in children. Using adult normative data in children may be inappropriate.

Fat emulsion intragastric stability and droplet size modulate gastrointestinal responses and subsequent food intake in young adults

BACKGROUND

Intragastric creaming and droplet size of fat emulsions may affect intragastric behavior and gastrointestinal and satiety responses.

OBJECTIVES

We tested the hypotheses that gastrointestinal physiologic responses and satiety will be increased by an increase in intragastric stability and by a decrease in fat droplet size of a fat emulsion.

METHODS

This was a double-blind, randomized crossover study in 11 healthy persons [8 men and 3 women, aged 24 ± 1 y; body mass index (in kg/m(2)): 24.4 ± 0.9] who consumed meals containing 300-g 20% oil and water emulsion (2220 kJ) with 1) larger, 6-μm mean droplet size (Coarse treatment) expected to cream in the stomach; 2) larger, 6-μm mean droplet size with 0.5% locust bean gum (LBG; Coarse+LBG treatment) to prevent creaming; or 3) smaller, 0.4-μm mean droplet size with LBG (Fine+LBG treatment). The participants were imaged hourly by using MRI and food intake was assessed by using a meal that participants consumed ad libitum.

RESULTS

The Coarse+LBG treatment (preventing creaming in the stomach) slowed gastric emptying, resulting in 12% higher gastric volume over time (P < 0.001), increased small bowel water content (SBWC) by 11% (P < 0.01), slowed appearance of the (13)C label in the breath by 17% (P < 0.01), and reduced food intake by 9% (P < 0.05) compared with the Coarse treatment. The Fine+LBG treatment (smaller droplet size) slowed gastric emptying, resulting in 18% higher gastric volume (P < 0.001), increased SBWC content by 15% (P < 0.01), and significantly reduced food intake by 11% (P < 0.05, equivalent to an average of 411 kJ less energy consumed) compared with the Coarse+LBG treatment. These high-fat meals stimulated substantial increases in SBWC, which increased to a peak at 4 h at 568 mL (range: 150-854 mL; P < 0.01) for the Fine+LBG treatment.

CONCLUSION

Manipulating intragastric stability and fat emulsion droplet size can influence human gastrointestinal physiology and food intake.

Does age affect gastric emptying time? A model-based meta-analysis of data from premature neonates through to adults

Purpose. Gastric emptying (GE) is often reported to be slower and more irregular in premature neonates than in older children and adults. The aim of this study was to investigate the impact of age and other covariates on the rate of GE. Methods. The effect of age on the mean gastric residence times (MGRT) of liquid and solid food was assessed by analysing 49 published studies of 1457 individuals, aged from 28 weeks gestation to adults. The data were modelled using the nonlinear mixed‐effects approach within NONMEM version 7.2 (ICON, Dublin, Ireland), with evaluation of postnatal age, gestational age and meal type as covariates. A double Weibull function was selected as a suitable model since it could account for the typical biphasic nature of GE. Results. Age was not a significant covariate for GE but meal type was. Aqueous solutions were associated with the fastest emptying time (mean simulated gastric residence time of 45 min) and solid food was associated with the slowest (98 min). Conclusions. These findings challenge the assertion that GE is different in neonates, as compared with older children and adults due to age, and they reinforce the significance of food type in modulating GE. © 2015 The Authors. Biopharmaceutics & Drug Disposition Published by John Wiley & Sons Ltd.

Preventing gastric sieving by blending a solid/water meal enhances satiation in healthy humans

Separation of solids and liquids within the stomach allows faster gastric emptying of liquids compared with solids, a phenomenon known as sieving. We tested the hypothesis that blending a solid and water meal would abolish sieving, preventing the early rapid decrease in gastric volume and thereby enhancing satiety. We carried out 2 separate studies. Study 1 was a 2-way, crossover, satiety study of 22 healthy volunteers who consumed roasted chicken and vegetables with a glass of water (1008 kJ) or the same blended to a soup. They completed satiety visual analogue scales at intervals for 3 h. Study 2 was a 2-way, crossover, mechanistic study of 18 volunteers who consumed the same meals and underwent an MRI to assess gastric emptying, gallbladder contraction, and small bowel water content (SBWC) at intervals for 3 h. In Study 1, the soup meal was associated with reduced hunger (P = 0.02). In Study 2, the volume of the gastric contents after the soup meal decreased more slowly than after the solid/liquid meal (P = 0.0003). The soup meal caused greater gallbladder contraction (P < 0.04). SBWC showed a biphasic response with an initial "gastric" phase during which SBWC was greater when the solid/liquid meal was consumed (P < 0.001) and a later "small bowel" phase when SBWC was greater when the soup meal was consumed (P < 0.01). Blending the solid/liquid meal to a soup delayed gastric emptying and increased the hormonal response to feeding, which may contribute to enhanced postprandial satiety.

Gastrointestinal targets of appetite regulation in humans

The aim of this paper is to describe and discuss relevant aspects of the assessment of physiological functions - and related biomarkers - implicated in the regulation of appetite in humans. A short introduction provides the background and the present state of biomarker research as related to satiety and appetite. The main focus of the paper is on the gastrointestinal tract and its functions and biomarkers related to appetite for which sufficient data are available in human studies. The first section describes how gastric emptying, stomach distension and gut motility influence appetite; the second part describes how selected gastrointestinal peptides are involved in the control of satiety and appetite (ghrelin, cholecystokinin, glucagon-like peptide, peptide tyrosin-tyrosin) and can be used as potential biomarkers. For both sections, methodological aspects (adequacy, accuracy and limitation of the methods) are described. The last section focuses on new developments in techniques and methods for the assessment of physiological targets involved in appetite regulation (including brain imaging, interesting new experimental approaches, targets and markers). The conclusion estimates the relevance of selected biomarkers as representative markers of appetite regulation, in view of the current state of the art.

Gastrointestinal transit, appetite, and energy balance in gastrectomized patients

BACKGROUND

Alterations in gastrointestinal tract physiology after gastrectomy may affect appetite and energy balance.

OBJECTIVE

The objective of this study was to examine energy balance, appetite, and gastrointestinal transit in subjects with gastrectomy.

DESIGN

Seven subjects with total gastrectomy (TG) and 14 subjects with partial gastrectomy (PG), who were free from signs of recurrent disease, and 10 healthy control subjects were studied. Resting energy expenditure (REE) was measured by indirect calorimetry and compared with REE predicted by the Harris-Benedict equation (mREE/pREE%). Gastrointestinal transit was measured by scintigraphy. Habitual food intake was assessed, and appetite was measured during scintigraphy after ingestion of a test meal (361 kcal).

RESULTS

Body mass index was not different among the groups. mREE/pREE% was higher in patients with PG (P < 0.01) than in control subjects. The TG group showed higher energy intake (P < 0.05) than the PG group and control subjects. Gastric emptying was faster in the PG group than in control subjects, and gastrointestinal transit was accelerated in both PG and TG groups. An intense, precocious postprandial fullness and a relatively early recovery of hunger and prospective consumption sensations were seen in these patients.

CONCLUSIONS

Patients with PG or TG have higher than predicted energy expenditure, which in TG seems to be compensated for by increased energy intake. These patients have preserved postprandial appetite responses and precocious postprandial fullness, which seem to be associated with disturbances in gastrointestinal transit of the ingested meal and are likely to be independent of vagal fiber integrity or stomach-released ghrelin.

Influence of posture on pharmacokinetics

INTRODUCTION

Body position may influence physiological characteristics, such as perfusion, gastrointestinal function and plasma volume. These characteristics may interact with key factors determining the pharmacokinetics of drugs (dissolution, absorption, distribution, metabolism, excretion).

OBJECTIVES

Based on a systematic literature search, current data on the effect of posture on physiological characteristics and/or pharmacokinetics are summarized, and the relevance of possible effects, such as those presenting in clinical practice and clinical pharmacokinetic studies, is assessed.

RESULTS

Postures which favour rapid gastric emptying (sitting, standing, recumbent right) accelerate the absorption of orally administered drugs. Consequently, these postures favour a shorter time to reach peak plasma drug concentration (t(max)) and a higher maximum plasma drug concentration (C(max)) and--in the case of transient saturation of first-pass metabolism--total exposure (area under the concentration-time curve, AUC) in comparison to recumbent left and supine positions (e.g. nifedipine: AUC 30 and 38% higher in standing and right lateral position vs. left lateral position; C(max) 149 and 80% higher, respectively). The magnitude of these postural effects depends strongly on the nature and amount of liquids and food ingested before drug administration and is most pronounced in the fasting state and after administration with a nonnutrient liquid. Changes in splanchnic-hepatic blood flow (e.g. reduction of estimated hepatic perfusion by 37% in standing vs. supine position) may substantially affect the metabolism of orally administered drugs, especially of those with a high/saturable first-pass metabolism. For highly protein-bound drugs (e.g. phenytoin, imipramine), the total plasma concentration has been found to be approximately 10% higher in standing than lying subjects due to changes in plasma volume.

CONCLUSIONS

Positioning of a patient may be an effective method of enhancing or retarding absorption of some drugs in appropriate clinical situations (e.g. toxic ingestions, bedridden patients). In clinical pharmacokinetic trials, such as bioequivalence studies, defining and maintaining posture precisely is a useful approach for reducing within- and between-subject variability.

Effects of posture on the physiology of gastric emptying: a magnetic resonance imaging study

OBJECTIVE

Gastric contents empty from the stomach despite frequent changes in body position. The mechanism that maintains gastric emptying independent of position is poorly understood. The aim of this study was to determine the effects of body position on gastric emptying and motor function.

MATERIAL AND METHODS

Twelve volunteers were investigated in seated position (SP) and upside-down position (UDP) after ingestion of 300 ml water. Magnetic resonance imaging provided a non-invasive assessment of gastric emptying and volumes, intragastric distribution and peristaltic function.

RESULTS

A marked difference in distal/proximal intragastric distribution between UDP and SP was present (7% versus 40%; p < 0.01). Gastric-emptying time was similar but emptying pattern was linear in UDP and exponential in SP. Peristalsis was slower in UDP than SP (2.75 versus 2.96 min-1; p < 0.01), but no correlation was found between peristaltic frequency and the rate of gastric emptying in either position. Postprandial volume response (gastric relaxation) was greater in UDP than SP (280 versus 250 ml; p < 0.05). A correlation was found between gastric relaxation and gastric-emptying time in SP (r2=0.46) but not in UDP.

CONCLUSIONS

The stomach maintains the rate of gastric emptying despite radical changes in body position and intragastric distribution of gastric contents. In SP, hydrostatic pressure (modulated by gastric tone) dictates the gastric emptying. In UDP, gastric emptying also appears to be mediated by continuous adaptation of gastric tone. These findings provide support for the hypothesis that the mechanism of gastric emptying resembles a "pressure pump" rather than a "peristaltic pump".

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.

Gastric motor function and emptying in the right decubitus and seated body position as assessed by magnetic resonance imaging

PURPOSE

To determine the effect of the right decubitus lying body position (RP) on relevant parameters of human gastric motor function in healthy volunteers.

MATERIALS AND METHODS

Postprandial gastric function after ingestion of a solid/liquid meal (150 g/150 mL) was assessed over 90 minutes in volunteers in the RP and seated position (SP). Ten healthy volunteers were imaged using two MRI systems that differed in architecture and field strength. Stomach and intragastric air volume, intragastric meal distribution, gastric emptying, and gastric peristalsis were compared between the RP and SP.

RESULTS

Body position did not affect gastric relaxation (RP, 372 mL vs. SP, 384 mL) and initial gastric volumes (stomach: RP, 458 mL vs. SP, 462 mL; meal: RP, 377 mL vs. SP, 399 mL; intragastric air: RP, 110 mL vs. SP, 98 mL). Postprandial stomach volume and gastric activity (RP and SP, 3.1 minute(-1)) were also similar. Meal emptying showed different characteristics, resulting in a significant but small difference in meal volume of -43 mL at t = 90 minutes (P < 0.05).

CONCLUSION

Gastric MRI in RP is feasible for clinical research assessing gastric motor function. The subtle difference in meal emptying may be induced by posture-dependent vagal activity. This study confirms that MRI is a highly sensitive imaging technique for assessing gastrointestinal function in humans.

Funktionelle Magnetresonanzbildgebung des Verdauungstrakts

Magnetic resonance imaging (MRI) is a versatile medical imaging tool for which several new applications have been developed. Beside its broad clinical use for the detection of anatomical structures and pathologies MRI has been successfully applied for the non-invasive imaging of human organ functions, including the brain and the cardiovascular system. The use of MRI for the assessment and analysis of gastrointestinal (GI) function is a new approach that is currently performed in only a few research sites. Several characteristics make MRI an ideal technique for the direct assessment of GI physiology: MRI acquires high resolution images with excellent soft tissue contrast, it does not expose subjects to ionizing radiation, is non-invasive, and the acquisition and analysis of the images can be independently verified. In this article we summarize recent developments of MRI techniques in GI research. We will also discuss the advantages and limitations of MRI for this purpose in relation to established medical imaging tools and investigations.

The delay of gastric emptying induced by remifentanil is not influenced by posture

Posture has an effect on gastric emptying. In this study, we investigated whether posture influences the delay in gastric emptying induced by opioid analgesics. Ten healthy male subjects underwent 4 gastric emptying studies with the acetaminophen method. On two occasions the subjects were given a continuous infusion of remifentanil (0.2 microg. kg(-1). min(-1)) while lying either on the right lateral side in a 20 degrees head-up position or on the left lateral side in a 20 degrees head-down position. On two other occasions no infusion was given, and the subjects were studied lying in the two positions. When remifentanil was given, there were no significant differences between the two postures in maximal acetaminophen concentration (right side, 34 micromol. L(-1); versus left side, 16 micromol. L(-1)), time taken to reach the maximal concentration (94 versus 109 min), or area under the serum acetaminophen concentration time curve from 0 to 60 min (962 versus 197 min. micromol. L(-1)). In the control situation, there were differences between the postures in maximal acetaminophen concentration (138 versus 94 micromol. L(-1); P < 0.0001) and area under the serum acetaminophen concentration time curves from 0 to 60 min (5092 versus 3793 min. micromol. L(-1); P < 0.0001), but there was no significant difference in time taken to reach the maximal concentration (25 versus 47 min). Compared with the control situation, remifentanil delayed gastric emptying in both postures. We conclude that remifentanil delays gastric emptying and that this delay is not influenced by posture.

Gastroduodenal motility

PURPOSE OF REVIEW

The neuromuscular function of the stomach and duodenum provides the mechanical forces that drive digestion and are responsible for sensations of satiety and of dyspepsia. This article reviews (1) the neuroendocrine factors controlling upper gastrointestinal motility, (2) noninvasive techniques to evaluate gastroduodenal motility, and (3) the pathophysiology and treatment of gastroparesis.

RECENT FINDINGS

Nutrients in the duodenum inhibit gastric emptying via a feedback pathway that involves release of cholecystokinin and serotonin (5-HT) from neuroendocrine cells; both act peripherally, cholecystokinin via cholecystokinin A receptors and serotonin via 5-HT3 receptors. The dorsal vagal complex plays a central role in the gastric inhibition mediated by tumor necrosis factor-alpha. The construction of maps that define intestinal movements in time and space has now been extended to the stomach. MRI compares favorably with the barostat in assessing gastric volume accommodation to meals and drugs and has the advantage of being noninvasive and showing contractions. Gastroparesis is increasingly recognized as a complication of end-stage liver disease; ascites plays no role in this, but portal hypertension stiffens the gastric walls and creates hypoxic conditions that may interfere with the neuromuscular functions of the stomach. Promising for the treatment of gastroparesis are clonidine, sildenafil, and intrapyloric botulinum toxin. Electrical stimulation triggers a vagally mediated relaxation of the stomach.

SUMMARY

Drugs may be designed that specifically act on 5-HT3, cholecystokinin, or TNF-alpha receptors. Spatiotemporal maps should boost the diagnostic yield from dynamic imaging of motility using ultrasound, computed axial tomography scan, or MRI and the understanding of the mechanical forces driving digestion. Symptomatic benefit in gastroparesis may derive more from improved accommodation than gastric emptying.

The Effect of Meals at Different Mealtimes on Blood Pressure and Symptoms in Geriatric Patients With Postprandial Hypotension

BACKGROUND

The variability of postprandial hypotension (PPH) during the day in elderly patients is unknown. We examined the effect of meals administered at different mealtimes on postprandial blood pressure (BP) responses in geriatric patients.

METHODS

In 14 geriatric patients (6 men and 8 women, aged 66-97) previously diagnosed with PPH, standardized liquid test meals were given in random order at breakfast, lunchtime, or dinnertime on 3 separate days. Systolic BP (SBP), diastolic BP (DBP), and heart rate (HR) were measured with an ambulatory BP device every 10 minutes from 20 minutes before until 90 minutes after each meal. Postprandial symptoms were observed continuously.

RESULTS

Significant decreases in SBP and DBP were present after each meal (p <.050). The maximum SBP decrease was significantly smaller at dinnertime (-18 +/- 3 mmHg) than at breakfast (-29 +/- 2 mmHg) or lunchtime (-34 +/- 4 mmHg) (p <.005 between groups). Eight patients showed no PPH in the evening, whereas all patients had PPH after breakfast and lunch. The duration of PPH was significantly shorter (p <.001), and postprandial symptoms were less frequent and less severe after dinner compared to breakfast and lunch.

CONCLUSIONS

In geriatric patients, postprandial BP responses show a variation during the day, with significantly less PPH and fewer symptoms in the evening. Clinical implication is that, in the diagnostic process and management of PPH, the variation of the occurrence of PPH during the day should be taken into account. Through adjustment of BP decreasing activities to the time PPH is least prevalent, the risk of developing symptomatic PPH can be reduced.