Gastric Microcirculation Research Articles

Sub-therapeutic vasopressin but not therapeutic vasopressin improves gastrointestinal microcirculation in septic rats: A randomized, placebo-controlled, blinded trial.

IntroductionSepsis impairs gastrointestinal microcirculation and it is hypothesized that this might increase patient’s mortality. Sub-therapeutic vasopressin improves gastric microcirculation under physiologic conditions whereas a therapeutic dosing regimen seems to be rather detrimental. However, the effects of sub-therapeutic vasopressin on gastrointestinal microcirculation in sepsis are largely unknown. Therefore, we conducted this trial to investigate the effect of sub-therapeutic as well as therapeutic vasopressin on gastrointestinal microcirculation in sepsis.Methods40 male Wistar rats were randomized into 4 groups. Colon ascendens stent peritonitis (CASP)-surgery was performed to establish mild or moderate sepsis. 24 hours after surgery, animals received either vasopressin with increasing dosages every 30 min (6.75, 13.5 (sub-therapeutic), 27 mU · kg-1 · h-1 (therapeutic)) or vehicle. Microcirculatory oxygenation (μHBO2) of the colon was recorded for 90 min using tissue reflectance spectrophotometry. Intestinal microcirculatory perfusion (total vessel density (TVD; mm/mm2) and perfused vessel density (PVD; mm/mm2)) were measured using incident dark field-Imaging at baseline and after 60 min.ResultsIn mild as well as in moderate septic animals with vehicle-infusion intestinal μHbO2, TVD and PVD remained constant. In contrast, in moderate sepsis, sub-therapeutic vasopressin with 13.5 mU · kg-1 · h-1 elevated intestinal μHBO2 (+ 6.1 ± 5.3%; p < 0.05 vs. baseline) and TVD (+ 5.2 ± 3.0 mm/mm2; p < 0.05 vs. baseline). μHBO2, TVD and PVD were significantly increased compared to moderate sepsis alone. However, therapeutic vasopressin did not change intestinal microcirculation. In mild septic animals sub-therapeutic as well as therapeutic vasopressin had no relevant effect on gastrointestinal microcirculation. Systemic blood pressure remained constant in all groups.ConclusionSub-therapeutic vasopressin improves gastrointestinal microcirculatory oxygenation in moderate sepsis without altering systemic blood pressure. This protective effect seems to be mediated by an enhanced microcirculatory perfusion and thereby increased oxygen supply. In contrast, therapeutic vasopressin did not show this beneficial effect.

Novel Hydrogen Sulfide (H2S)-Releasing BW-HS-101 and Its Non-H2S Releasing Derivative in Modulation of Microscopic and Molecular Parameters of Gastric Mucosal Barrier.

Hydrogen sulfide (H2S) is an endogenously produced molecule with anti-inflammatory and cytoprotective properties. We aimed to investigate for the first time if a novel, esterase-sensitive H2S-prodrug, BW-HS-101 with the ability to release H2S in a controllable manner, prevents gastric mucosa against acetylsalicylic acid-induced gastropathy on microscopic and molecular levels. Wistar rats were pretreated intragastrically with vehicle, BW-HS-101 (0.5–50 μmol/kg) or its analogue without the ability to release H2S, BW-iHS-101 prior to ASA administration (125 mg/kg, intragastrically). BW-HS-101 was administered alone or in combination with nitroarginine (L-NNA, 20 mg/kg, intraperitoneally) or zinc protoporphyrin IX (10 mg/kg, intraperitoneally). Gastroprotective effects of BW-HS-101 were additionally evaluated against necrotic damage induced by intragastrical administration of 75% ethanol. Gastric mucosal damage was assessed microscopically, and gastric blood flow was determined by laser flowmetry. Gastric mucosal DNA oxidation and PGE2 concentration were assessed by ELISA. Serum and/or gastric protein concentrations of IL-1α, IL-1β, IL-2, IL-4, IL-6, IL-10, IL-13, VEGF, GM-CSF, IFN-γ, TNF-α, and EGF were determined by a microbeads/fluorescent-based multiplex assay. Changes in gastric mucosal iNOS, HMOX-1, SOCS3, IL1-R1, IL1-R2, TNF-R2, COX-1, and COX-2 mRNA were assessed by real-time PCR. BW-HS-101 or BW-iHS-101 applied at a dose of 50 μmol/kg protected gastric mucosa against ASA-induced gastric damage and prevented a decrease in the gastric blood flow level. H2S prodrug decreased DNA oxidation, systemic and gastric mucosal inflammation with accompanied upregulation of SOCS3, and EGF and HMOX-1 expression. Pharmacological inhibition of nitric oxide (NO) synthase but not carbon monoxide (CO)/heme oxygenase (HMOX) activity by L-NNA or ZnPP, respectively, reversed the gastroprotective effect of BW-HS-101. BW-HS-101 also protected against ethanol-induced gastric injury formation. We conclude that BW-HS-101, due to its ability to release H2S in a controllable manner, prevents gastric mucosa against drugs-induced gastropathy, inflammation and DNA oxidation, and upregulate gastric microcirculation. Gastroprotective effects of this H2S prodrug involves endogenous NO but not CO activity and could be mediated by cytoprotective and anti-inflammatory SOCS3 and EGF pathways.

Topical Melatonin Improves Gastric Microcirculatory Oxygenation During Hemorrhagic Shock in Dogs but Does Not Alter Barrier Integrity of Caco-2 Monolayers

Systemic administration of melatonin exerts tissue protective effects in the context of hemorrhagic shock. Intravenous application of melatonin prior to hemorrhage improves gastric microcirculatory perfusion and maintains intestinal barrier function in dogs. The aim of the present study was to analyze the effects of a topical mucosal melatonin application on gastric microcirculation during hemorrhagic shock in vivo and on mucosal barrier function in vitro. In a randomized cross-over study, six anesthetized female foxhounds received 3.3 mg melatonin or the vehicle as a bolus to the gastric and oral mucosa during physiological and hemorrhagic (−20% blood volume) conditions. Microcirculation was analyzed with reflectance spectrometry and laser doppler flowmetry. Systemic hemodynamic variables were measured with transpulmonary thermodilution. For analysis of intestinal mucosal barrier function in vitro Caco-2 monolayers were used. The transepithelial electrical resistance (TEER) and the passage of Lucifer Yellow (LY) from the apical to the basolateral compartment of Transwell chambers were measured. Potential barrier protective effects of melatonin against oxidative stress were investigated in the presence of the oxidant H2O2. During physiologic conditions topical application of melatonin had no effect on gastric and oral microcirculation in vivo. During hemorrhagic shock, gastric microcirculatory oxygenation (μHbO2) was decreased from 81 ± 8% to 50 ± 15%. Topical treatment with melatonin led to a significant increase in μHbO2 to 60 ± 13%. Topical melatonin treatment had no effect on gastric microcirculatory perfusion, oral microcirculation or systemic hemodynamics. Incubation of H2O2 stressed Caco-2 monolayers with melatonin did neither influence transepithelial electrical resistance nor LY translocation. Topical treatment of the gastric mucosa with melatonin attenuates the shock induced decrease in microcirculatory oxygenation. As no effects on local microcirculatory and systemic perfusion were recorded, the improved μHbO2 is most likely caused by a modulation of local oxygen consumption. In vitro melatonin treatment did not improve intestinal barrier integrity in the context of oxidative stress. These results extend the current knowledge on melatonin's protective effects during hemorrhage in vivo. Topical application of melatonin exerts differential effects on local microcirculation compared to systemic pretreatment and might be suitable as an adjunct for resuscitation of hemorrhagic shock.

Protective Effects of Wheat Peptides against Ethanol-Induced Gastric Mucosal Lesions in Rats: Vasodilation and Anti-Inflammation.

Alcohol consumption increases the risk of gastritis and gastric ulcer. Nutritional alternatives are considered for relieving the progression of gastric mucosal lesions instead of conventional drugs that produce side effects. This study was designed to evaluate the gastroprotective effects and investigate the defensive mechanisms of wheat peptides against ethanol-induced acute gastric mucosal injury in rats. Sixty male Sprague–Dawley rats were divided into six groups and orally treated with wheat peptides (0.1, 0.2, 0.4 g/kgbw) and omeprazole (20 mg/kgbw) for 4 weeks, following absolute ethanol administration for 1 h. Pretreatment with wheat peptides obviously enhanced the vasodilation of gastric mucosal blood vessels via improving the gastric mucosal blood flow and elevating the defensive factors nitric oxide (NO) and prostaglandin E2 (PGE2), and lowering the level of vasoconstrictor factor endothelin (ET)-1. Wheat peptides exhibited anti-inflammatory reaction through decreasing inducible nitric oxide synthase (iNOS) and pro-inflammatory cytokines tumor necrosis factor α (TNF-α), interleukin (IL)-1β, IL-6, and increasing trefoil factor 1 (TFF1) levels. Moreover, wheat peptides significantly down-regulated the expression of phosphorylated nuclear factor kappa-B (p-NF-κB) p65 proteins in the NF-κB signaling pathway. Altogether, wheat peptides protect gastric mucosa from ethanol-induced lesions in rats via improving the gastric microcirculation and inhibiting inflammation mediated by the NF-κB signaling transduction pathway.

Regional hypothermia improves gastric microcirculatory oxygenation during hemorrhage in dogs.

Mild systemic hypothermia increases gastric mucosal oxygenation (μHbO2) during hemorrhagic shock in dogs. In the context of critical blood loss hypothermia might be fatal due to adverse side effects. Selective regional hypothermia might overcome these limitations. The aim of our study was to analyze the effects of regional gastric and oral mucosal hypothermia on μHbO2 and perfusion (μflow). In a cross-over study six anesthetized dogs were subjected to local oral and gastric mucosal hypothermia (34°C), or maintenance of local normothermia during normovolemia and hemorrhage (-20% blood volume). Macro- and microcirculatory variables were recorded continuously. During normovolemia, local hypothermia increased gastric microcirculatory flow (μflow) without affecting oxygenation (μHbO2) or oral microcirculation. During mild hemorrhagic shock gastric μHbO2 decreased from 72±2% to 38±3% in the normothermic group. This was attenuated by local hypothermia, where μHbO2 was reduced from 74±3% to 52±4%. Local perfusion, oral microcirculation and macrocirculatory variables were not affected. Selective local hypothermia improves gastric μHbO2 during hemorrhagic shock without relevant side effects. In contrast to systemic hypothermia, regional mucosal hypothermia did not affect perfusion and oxygen supply during hemorrhage. Thus, the increased μHbO2 during local hypothermia rather indicates reduced mucosal oxygen demand.

Exogenous vasopressin dose-dependently modulates gastric microcirculatory oxygenation in dogs via V1A receptor

BackgroundHypercapnia improves gastric microcirculatory oxygenation (μHbO2) and increases vasopressin plasma levels, whereas V1A receptor blockade abolishes the increase of μHbO2. The aim of this study was to evaluate the effect of exogenous vasopressin (AVP) in increasing doses on microcirculatory perfusion and oxygenation and systemic hemodynamic variables. Furthermore, we evaluated the role of the vasopressin V1A receptor in mediating the effects.MethodsIn repetitive experiments, six anesthetized dogs received a selective vasopressin V1A receptor inhibitor ([Pmp1, Tyr (Me)2]-Arg8-Vasopressin) or sodium chloride (control groups). Thereafter, a continuous infusion of AVP was started with dose escalation every 30 min (0.001 ng/kg/min–1 ng/kg/min). Microcirculatory variables of the oral and gastric mucosa were measured with reflectance spectrometry, laser Doppler flowmetry, and incident dark field imaging. Transpulmonary thermodilution was used to measure systemic hemodynamic variables. AVP plasma concentrations were measured during baseline conditions and 30 min after each dose escalation.ResultsDuring control conditions, gastric μHbO2 did not change during the course of experiments. Infusion of 0.001 ng/kg/min and 0.01 ng/kg/min AVP increased gastric μHbO2 to 87 ± 4% and 87 ± 6%, respectively, compared to baseline values (80 ± 7%), whereas application of 1 ng/kg/min AVP strongly reduced gastric μHbO2 (59 ± 16%). V1A receptor blockade prior to AVP treatment abolished these effects on μHbO2. AVP dose-dependently enhanced systemic vascular resistance (SVR) and decreased cardiac output (CO). After prior V1A receptor blockade, SVR was reduced and CO increased (0.1 ng/kg/min + 1 ng/kg/min AVP).ConclusionsExogenous AVP dose-dependently modulates gastric μHbO2, with an increased μHbO2 with ultra-low dose AVP. The effects of AVP on μHbO2 are abolished by V1A receptor inhibition. These effects are independent of a modulation of systemic hemodynamic variables.

Photodynamic diagnostics of early gastric cancer: Complexity measures of gastric microcirculation and new model of metastatic adenocarcinoma of rat stomach

The detection of early gastric cancer that often develops asymptomatically is crucial for improving patient survival. The photodynamic diagnosis (PDD) of gastric cancer using 5-aminolevulinic acid/protoporphyrin IX (5-ALA/PpIX) has been reported in several studies. However, the selectivity of PDD of gastric tumor is poor with often false-positive results that require the development of new methods to improve PDD for early gastric cancer. Therefore, a measure of the complexity of gastric microcirculation (multi-scale entropy, MSE) and the detrended fluctuation analysis (DFA) were applied as additional tools to detect early gastric cancer in rats.In this experimental study, we used our original model of metastatic adenocarcinoma in the stomach of a rat. To induce a gastric tumor, we used a long-term combination (for 9 months, which is 1/2 of the life of rats) of two natural factors, such as chronic stress (overpopulation being typical for modern cities) and the daily presence of nitrites in food and drinks, which are common ingredients added to processed meat and fish to help preserve food. Our results clearly show that both methods, namely, PDD using 5-ALA/PpIX and complexity/correlation analysis, can detect early gastric cancer, which was confirmed by histological analysis. Pre-cancerous areas in the stomach were detected as an intermediate fluorescent signal or MSE level between normal and malignant lesions of the stomach. However, in some cases, PDD with 5-ALA/PpIX produced a false-positive fluorescence of exogenous fluorophores due to its accumulation in benign and inflammatory areas of the mucosa. This fact indicates that the PDD itself is not sufficient for the correct diagnosis of gastric cancer, and the use of additional characteristics, e.g., complexity measures or scaling exponents, can significantly improve the diagnostic accuracy of PDD of gastric cancer that should be confirmed in further clinical studies and applications.

Stenosis of the celiac trunk is associated with anastomotic leak after Ivor-Lewis esophagectomy.

Transthoracic esophagectomy with gastric tube formation is the surgical treatment of choice for esophageal cancer. The surgical reconstruction induces changes of gastric microcirculation, which are recognized as potential risk factors of anastomotic leak. This prospective observational study investigates the association of celiac trunk (TC) stenosis with postoperative anastomotic leak. One hundred fifty-four consecutive patients with esophageal cancer scheduled for Ivor-Lewis esophagectomy were included. Preoperative staging computed tomography (CT) was used to identify TC stenosis. Any narrowing of the lumen due to atherosclerotic changes was classified as stenosis. Percentage of stenotic changes was calculated using the North American Symptomatic Carotid Endarterectomy Trial formula. Multivariable analysis was used to identify possible risk factors for leak. The overall incidence of TC stenosis was 40.9%. Anastomotic leak was identified in 15 patients (9.7%). Incidence of anastomotic leak in patients with stenosis was 19.4% compared to 2.3% in patients without stenosis. Incidence of stenosis in patients with leak was 86.7% (13 of 15 patients) and significantly higher than 38.8% (54 of 139 patients) in patients without leak (P<0.001). There was a significant difference in median degree of TC stenosis (50.0% vs 39.4%; P=0.032) in patients with and without leak. In the multivariable model, TC stenosis was an independent risk factor for anastomotic leak (odds ratio: 5.98, 95% CI: 1.58-22.61). TC stenosis is associated with postoperative anastomotic leak after Ivor-Lewis esophagectomy. Routine assessment of TC for possible stenosis is recommended to identify patients at risk.

Alterations in Gastric Mucosal Expression of Calcitonin Gene-Related Peptides, Vanilloid Receptors, and Heme Oxygenase-1 Mediate Gastroprotective Action of Carbon Monoxide against Ethanol-Induced Gastric Mucosal Lesions.

Carbon monoxide (CO) has been reported to contribute to the maintenance of gastric mucosal integrity, gastroprotection, and ulcer healing. However, involvement of transient receptor potential vanilloid receptor type 1 (TRPV1) located on afferent sensory fibers endings and sensory neuropeptide calcitonin gene-related peptide (CGRP) in CO-mediated gastroprotection against ethanol-induced gastric damage has not been explored. Male Wistar rats with and without denervation of afferent sensory neurons induced by capsaicin (total dose 125 mg/kg within 3 days) were pretreated with vehicle, CO donor tricarbonyldichlororuthenium (II) dimer (CORM-2, 5 mg/kg i.g.), administered alone or with CGRP-α (10 μg/kg i.p.) or TRPV1 antagonist capsazepine (5 mg/kg i.g.), followed 30 min later by intragastric (i.g.) administration of 75% ethanol. The area of gastric damage and gastric blood flow (GBF) were assessed planimetrically and by laser flowmetry, respectively. Microscopic evaluation of ethanol-induced gastric lesions was performed after haematoxylin/eosin (H&E) or alcian blue/periodic acid-Schiff/alcian blue (AB/PAS) staining. Gastric mucosal mRNA fold change for heme oxygenase (HMOX)-1, HMOX-2, CGRP-α, CGRP-β, inducible nitric oxide synthase (iNOS), endothelial (e)NOS, neuronal (n)NOS, cyclooxygenase (COX)-1, COX-2, and protein expression for HMOX-1 and TRPV1 was determined by real-time PCR or Western blot, respectively. Pretreatment with CORM-2 combined or not with CGRP reduced ethanol-induced gastric lesions and elevated GBF. Capsaicin-denervation or co-treatment with capsazepine or CGRP and CORM-2 in capsaicin-denervated animals failed to affect these beneficial effects of CO donor. In rats with intact sensory nerves, CORM-2 increased gastric mRNA level for HMOX-1 and CGRP-α. In capsaicin-denervated rats, CORM-2 increased eNOS mRNA fold change and TRPV1 protein expression while capsaicin denervation itself decreased HMOX-1 protein expression and eNOS mRNA level. We conclude that CO prevents gastric mucosa from ethanol-induced lesions due to activation of TRPV1/CGRP-α system and accompanying increase in gastric microcirculation but independently on afferent sensory nerve activity despite the stimulation of TRPV1 protein and CGRP-α mRNA expression.

VS03.01: QUANTITATIVE IMAGING OF CHANGE IN MICROCIRCULATION BY SIDESTREAM DARK FIELD MICROSCOPY (SDF) AFTER ESOPHAGECTOMY

Abstract Description Anastomotic leakage is one of the most severe complications after esophageal resection with gastric tube reconstruction. Impaired perfusion of the gastric fundus is seen as the main contributing factor for this complication. Transection of the left gastric and gastro-epiploic artery and veins results in compromised perfusion in the fundus area which can result in anastomotic dehiscence (5–20%), relating to high morbidity and mortality (3–4%). The main objective of this observational study is to evaluation gastric tube microcirculation with Sidestream Darkfield Microscopy (SDF). Method This study included 22 patients (October 2015 - June 2016). Intra-operative microscopic images of gastric tube microcirculation were obtained with SDF directly after reconstruction. Using software (AVA2.0), the following parameters were evaluated: average velocity (μm/sec), Microvascular Flow Index (MFI), Total Vessel Density (TVD), Perfusion Vessel Density (PVD), Proportion of Perfused Vessels (PPV) and the De Backer Score (DBS), to assess change in perfusion. Results SDF accurately visualized and evaluated microcirculation in all patients. A SDF-stabilizer was used to create stable images. The average velocity decreased significantly towards the fundus (P = 0.001). Also, MFI, PVD and PPV were significantly lower towards the fundus, compared to the base of the gastric tube (P = 0.0002). No differences in TVD and DBS were observed, which was associated to the observed vessel dilation in the fundus-area. This vessel dilation proposes that compromised venous return may play an important role in the development of necrosis and leakage. Three patients developed anastomotic leakage. Conclusion This is the first study presenting quantitative microcirculation imaging with SDF of the gastric tube. Velocity, MFI, TVD and PPV were accurate parameters to observe change in perfusion after reconstruction. Also, vessel dilation in the fundus suggests a role for venous return in the development of ischemia. Quantitative microcirculation with SDF could allow for intra-operative early risk stratification, and, potentially, can result in a reduction of anastomotic leakage. Disclosure All authors have declared no conflicts of interest.

FA05.03: EFFECT OF EPHEDRINE ON GASTRIC CONDUIT PERFUSION MEASURED BY LASER SPECKLE CONTRAST IMAGING (LSCO) AFTER ESOPHAGECTOMY: A PROSPECTIVE IN-VIVO COHORT STUDY

Abstract Background Compromised perfusion due to ligation of arteries and veins in esophagectomy with gastric tube reconstruction often (5–20%) results in necrosis and anastomotic leakage, which relate to high morbidity and mortality (3–4%). Ephedrine is used widely in anesthesia to treat intra-operative hypotension and may improve perfusion by the increase of cardiac output (CO) and mean arterial pressure (MAP). This study tests the effect of ephedrine on perfusion of the future anastomotic site of the gastric conduit, measured by Laser Speckle Contrast Imaging (LSCI). Methods This prospective, observational, in-vivo pilot study includes 26 patients undergoing esophagectomy with gastric tube reconstruction from October 2015 to June 2016 in the Academic Medical Center (Amsterdam). Perfusion of the gastric conduit was measured with LSCI directly after reconstruction and after an increase of MAP by ephedrine 5 mg. Perfusion was quantified in flux (LSPU) in four perfusion locations, from good perfusion (base of the gastric tube) towards decreased perfusion (fundus). Intra-patient differences before and after ephedrine in terms flux were statistically tested for significance with a paired t-test. Results LSCI was feasible to image gastric microcirculation in all patients. Flux (LSPU) was significantly higher in the base of the gastric tube (791 ± 442) compared to the fundus (328 ± 187) (P &lt; 0.001). After administration of ephedrine, flux increased significantly in the fundus (P &lt; 0·05) measured intra-patients. Three patients developed anastomotic leakage. In these patients, the difference between measured flux in the fundus compared to the base of the gastric tube was high. Conclusion This study presents the effect of ephedrine on perfusion of the gastric tissue measured with LSCI in terms of flux (LSPU) after esophagectomy with gastric tube reconstruction. We show a small but significant difference between flux measured before and after administration of ephedrine in the future anastomotic tissue (313 ± 178 vs. 397 ± 290). We also show a significant decrease of flux towards the fundus. Disclosure All authors have declared no conflicts of interest.

Feasibility of Optical Coherence Tomography (OCT) for Intra-Operative Detection of Blood Flow during Gastric Tube Reconstruction.

In this study; an OCT-based intra-operative imaging method for blood flow detection during esophagectomy with gastric tube reconstruction is investigated. Change in perfusion of the gastric tube tissue can lead to ischemia; with a high morbidity and mortality as a result. Anastomotic leakage (incidence 5–20%) is one of the most severe complications after esophagectomy with gastric tube reconstruction. Optical imaging techniques provide for minimal-invasive and real-time visualization tools that can be used in intraoperative settings. By implementing an optical technique for blood flow detection during surgery; perfusion can be imaged and quantified and; if needed; perfusion can be improved by either a surgical intervention or the administration of medication. The feasibility of imaging gastric microcirculation in vivo using optical coherence tomography (OCT) during surgery of patients with esophageal cancer by visualizing blood flow based on the speckle contrast from M-mode OCT images is studied. The percentage of pixels exhibiting a speckle contrast value indicative of flow was quantified to serve as an objective parameter to assess blood flow at 4 locations on the reconstructed gastric tube. Here; it was shown that OCT can be used for direct blood flow imaging during surgery and may therefore aid in improving surgical outcomes for patients.

Effect of ephedrine on gastric conduit perfusion measured by laser speckle contrast imaging after esophagectomy: a prospective in vivo cohort study.

Compromised perfusion due to ligation of arteries and veins in esophagectomy with gastric tube reconstruction often (5-20%) results in necrosis and anastomotic leakage, which relate to high morbidity and mortality (3-4%). Ephedrine is used widely in anesthesia to treat intraoperative hypotension and may improve perfusion by the increase of cardiac output and mean arterial pressure (MAP). This study tests the effect of ephedrine on perfusion of the future anastomotic site of the gastric conduit, measured by laser speckle contrast imaging (LSCI). This prospective, observational, in vivo pilot study includes 26 patients undergoing esophagectomy with gastric tube reconstruction from October 2015 to June 2016 in the Academic Medical Center (Amsterdam). Perfusion of the gastric conduit was measured with LSCI directly after reconstruction and after an increase of MAP by ephedrine 5 mg. Perfusion was quantified in flux (laser speckle perfusion units, LSPU) in four perfusion locations, from good perfusion (base of the gastric tube) toward decreased perfusion (fundus). Intrapatient differences before and after ephedrine in terms flux were statistically tested for significance with a paired t-test. LSCI was feasible to image gastric microcirculation in all patients. Flux (LSPU) was significantly higher in the base of the gastric tube (791±442) compared to the fundus (328±187) (P<0.001). After administration of ephedrine, flux increased significantly in the fundus (P<0.05) measured intrapatients. Three patients developed anastomotic leakage. In these patients, the difference between measured flux in the fundus compared to the base of the gastric tube was high. This study presents the effect of ephedrine on perfusion of the gastric tissue measured with LSCI in terms of flux (LSPU) after esophagectomy with gastric tube reconstruction. We show a small but significant difference between flux measured before and after administration of ephedrine in the future anastomotic tissue (313±178 vs. 397±290). We also show a significant decrease of flux toward the fundus.

Recent Advances in the Gastric Mucosal Protection Against Stress-induced Gastric Lesions. Importance of Renin-angiotensin Vasoactive Metabolites, Gaseous Mediators and Appetite Peptides.

Stress is known to cause severe adverse effects in the human gastrointestinal tract including mucosal microbleedings and erosions or even gastric ulceration but the mechanism of these complications has not been fully elucidated. The pathogenesis of stress-induced gastric damage involves the fall in Gastric Blood Flow (GBF), an increase in gastric acid secretion and gastric motility, enhanced adrenergic and cholinergic nerve activity and the rise in gastric mucosal generation of reactive oxygen species. The gastric mucosal defense mechanisms against the deleterious effect of stress include the activation of the hypothalamic-pituitary-adrenal axis which has been linked with glucocorticoids release capable of counteracting of stress-induced gastric lesions. Here we summarize the novel gastroprotective mechanisms against stress damage exhibited by angiotensin-(1-7), the newly discovered metabolite of Renin-Angiotensin System (RAS), the gaseous mediators such as nitric oxide (NO), hydrogen sulfide (H2S) or Carbon Monoxide (CO), and the food intake controlling peptides ghrelin, nesfatin- 1 and apelin possibly acting via brain-gut axis. These bioactive molecules such as RAS vasoactive metabolite angiotensin-(1-7) and appetite peptides have been shown to afford gastroprotective effect against stressinduced gastric lesions mainly mediated by an increase in gastric microcirculation. Gaseous mediators protect the gastric mucosa against stress lesions by mechanism involving the activation of PG/COX and CO/HO-1 biosynthetic pathways, and their anti-inflammatory and anti-oxidizing properties. Thus, these new components add new mechanistic aspects to the common cooperation of NO/NO-synthase, PG/COX systems and vasoactive sensory neuropeptides including CGRP but their gastroprotective efficacy against experimental stress ulcerogenesis requires the confirmation in human clinical trials.

Evaluation of Gastric Microcirculation by Laser Speckle Contrast Imaging During Esophagectomy

Thoracic epidural anesthesia (TEA) may provoke hypotension, and that, as well as the use of vasopressors and the surgical technique, could affect splanchnic microcirculation, in which the surgical target organ is of particular interest. This study used laser speckle contrast imaging (LSCI) to monitor gastric microcirculation during esophagectomy. Forty-five patients undergoing open esophagectomy were randomized to primary activation (EA; 25 patients) or no intraoperative activation (LA; 20 patients) of TEA. Phenylephrine managed intraoperative hypotension and gastric microcirculation was assessed at antrum and corpus area by LSCI. Antrum microcirculation (mean ± SD) was lower in the EA group at baseline (1,150 ± 189 laser speckle perfusion units [LSPU] vs LA group: 1,265 ± 163 LSPU; p= 0.036). In both groups, antrum microcirculation tended to decrease in response to anesthesia, TEA, and surgical procedure (LA: 1,265 ± 163 to 1,097 ± 184 LSPU, p= 0.021; EA: 1,150 ± 189 to 1,064 ± 177 LSPU, p= 0.093), with no difference between groups during the remaining laparotomy. Corpus microcirculation decreased in both groups from baseline to gastric pull-up in response to anesthesia, TEA, and surgery (LA: 1,081 ± 236 to 649 ± 165 LSPU, p < 0.001; EA: 1,011 ± 208 to 675 ± 178 LSPU, p < 0.001), but recovered after gastric continuity was re-established (EA to 795 ± 162 LSPU, p= 0.027; LA to 815 ± 166 LSPU, p= 0.014), with no significant differences between groups (p > 0.05). The EA group needed continued phenylephrine support to maintain blood pressure (216 ± 86 vs 58 ± 91 minutes; p < 0.001). During esophagectomy, gastric microcirculation can be followed in real-time by LSCI. Flow changes in the stomach seemed related more to surgery than to TEA/vasopressor support. Laser speckle contrast imaging could form basis for directing procedures to maintain the microcirculation.

Effect of Topical Iloprost and Nitroglycerin on Gastric Microcirculation and Barrier Function during Hemorrhagic Shock in Dogs

Background: Topical drug application is used to avoid systemic side effects. The aim of this study was to analyze whether locally applied iloprost or nitroglycerin influence gastric mucosal perfusion, oxygenation, and barrier function during physiological and hemorrhagic conditions. Methods: In repeated experiments, 5 anesthetized dogs received iloprost, nitroglycerin, or normal saline during physiological and hemorrhagic (-20% blood volume) conditions. Macro- and microcirculatory variables were recorded continuously. Gastric barrier function was assessed via translocation of sucrose into the blood. Results: During hemorrhage, gastric mucosal oxygenation decreased from 77 ± 4 to 37 ± 7%. This effect was attenuated by nitroglycerin (78 ± 6 to 47 ± 13%) and iloprost (82 ± 4 to 54 ± 9%). Sucrose plasma levels increased during hemorrhage from 7 ± 4 to 55 ± 15 relative amounts. This was alleviated by nitroglycerin (5 ± 8 to 29 ± 38 relative amounts). These effects were independent of systemic hemodynamic variables. Conclusions: During hemorrhage, topical nitroglycerin and iloprost improve regional gastric oxygenation without affecting perfusion. Nitroglycerin attenuated the shock-induced impairment of the mucosal barrier integrity. Thus, local drug application improves gastric microcirculation without compromising systemic hemodynamic variables, and it may also protect mucosal barrier function.

Exogenous and Endogenous Hydrogen Sulfide Protects Gastric Mucosa against the Formation and Time-Dependent Development of Ischemia/Reperfusion-Induced Acute Lesions Progressing into Deeper Ulcerations.

Hydrogen sulfide (H2S) is an endogenous mediator, synthesized from l-cysteine by cystathionine γ-lyase (CSE), cystathionine β-synthase (CBS) or 3-mercaptopyruvate sulfurtransferase (3-MST). The mechanism(s) involved in H2S-gastroprotection against ischemia/reperfusion (I/R) lesions and their time-dependent progression into deeper gastric ulcerations have been little studied. We determined the effect of l-cysteine, H2S-releasing NaHS or slow H2S releasing compound GYY4137 on gastric blood flow (GBF) and gastric lesions induced by 30 min of I followed by 3, 6, 24 and 48 h of R. Role of endogenous prostaglandins (PGs), afferent sensory nerves releasing calcitonin gene-related peptide (CGRP), the gastric expression of hypoxia inducible factor (HIF)-1α and anti-oxidative enzymes were examined. Rats with or without capsaicin deactivation of sensory nerves were pretreated i.g. with vehicle, NaHS (18–180 μmol/kg) GYY4137 (90 μmol/kg) or l-cysteine (0.8–80 μmol/kg) alone or in combination with (1) indomethacin (14 μmol/kg i.p.), SC-560 (14 μmol/kg), celecoxib (26 μmol/kg); (2) capsazepine (13 μmol/kg i.p.); and (3) CGRP (2.5 nmol/kg i.p.). The area of I/R-induced gastric lesions and GBF were measured by planimetry and H2-gas clearance, respectively. Expression of mRNA for CSE, CBS, 3-MST, HIF-1α, glutathione peroxidase (GPx)-1, superoxide dismutase (SOD)-2 and sulfide production in gastric mucosa compromised by I/R were determined by real-time PCR and methylene blue method, respectively. NaHS and l-cysteine dose-dependently attenuated I/R-induced lesions while increasing the GBF, similarly to GYY4137 (90 μmol/kg). Capsaicin denervation and capsazepine but not COX-1 and COX-2 inhibitors reduced NaHS- and l-cysteine-induced protection and hyperemia. NaHS increased mRNA expression for SOD-2 and GPx-1 but not that for HIF-1α. NaHS which increased gastric mucosal sulfide release, prevented further progression of acute I/R injury into deeper gastric ulcers at 6, 24 and 48 h of R. We conclude that H2S-induced gastroprotection against I/R-injury is due to increase in gastric microcirculation, anti-oxidative properties and afferent sensory nerves activity but independent on endogenous prostaglandins.

A reduced gastric corpus microvascular blood flow during Ivor-Lewis esophagectomy detected by laser speckle contrast imaging technique

Background: Reduced microvascular blood flow is related to anastomotic insufficiency following esophagectomy, emphasizing a need for intraoperative monitoring of the microcirculation. This study evaluated if laser speckle contrast imaging (LSCI) was able to detect intraoperative changes in gastric microcirculation.Methods: Gastric microcirculation was assessed prior to and after reconstruction of gastric continuity in 25 consecutive patients operated for adenocarcinoma with open Ivor-Lewis esophagectomy while hemodynamic variables were recorded.Results: During upper laparotomy, microcirculation at the corpus decreased by 25% from baseline to mobilization of the stomach (p = .008) and decreased further (to a total decrease of 40%) following gastric pull to the thorax (p = .013). On the other hand, microcirculation at the antrum did not change significantly after gastric mobilization (p = .091). The decrease in corpus microcirculation took place unrelated to central cardiovascular variables.Conclusion: Using LSCI technique, we identified a reduced microcirculation at the corpus area during open Ivor-Lewis esophagectomy. LSCI provides an option for real-time assessment of gastric microcirculation and could form basis for intraoperative stabilization of the microcirculation.

Interaction between endogenous carbon monoxide and hydrogen sulfide in the mechanism of gastroprotection against acute aspirin-induced gastric damage

Acetylsalicylic acid (ASA) is mainly recognized as painkiller or anti-inflammatory drug. However, ASA causes serious side effects towards gastrointestinal (GI) tract which limits its usefulness. Carbon monoxide (CO) and hydrogen sulfide (H2S) have been described to act as important endogenous messengers and mediators of gastroprotection but whether they can interact in gastroprotection against acute ASA-induced gastric damage remains unknown.In this study male Wistar rats were pretreated with 1) vehicle (saline, i.g.), 2) tricarbonyldichlororuthenium (II) dimer (CORM-2, 5mg/kg i.g.), 3) sodium hydrosulfide (NaHS, 5mg/kg i.g.), 4) zinc protoporphyrin (ZnPP, 10mg/kg i.p.), 5) D,L-propargylglycine (PAG, 30mg/kg i.g.), 6) ZnPP combined with NaHS, 7) PAG combined with CORM-2 or 8) 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10mg/kg i.p.) combined with CORM-2 or NaHS and 30min later ASA was administered i.g. in a single dose of 125mg/kg. After 1h, gastric blood flow (GBF) was determined by H2 gas clearance technique and gastric lesions were assessed by planimetry and histology. CO content in gastric mucosa and COHb concentration in blood were determined by gas chromatography and H2S production was assessed in gastric mucosa using methylene blue method. Protein and/or mRNA expression for cystathionine-γ-lyase (CSE), cystathionine-β-synthase (CBS), 3-mercaptopyruvate sulfurtransferase (3-MST), heme oxygenase (HO)-1, HO-2, hypoxia inducible factor-alpha (HIF)-1α, nuclear factor (erythroid-derived 2)-like 2 (Nrf-2), cyclooxygenase (COX)-1 and COX-2, inducible nitric oxide synthase (iNOS) and interleukin (IL)-1β were determined by Western blot or real-time PCR, respectively.ASA caused hemorrhagic gastric mucosal damage and significantly decreased GBF, H2S production, CO content, mRNA or protein expression for CSE, 3-MST, HO-2 and increased mRNA and/or protein expression for CBS, HO-1, Nrf-2, HIF-1α, iNOS, IL-1β, COX-2 in gastric mucosa and COHb concentration in blood. Pretreatment with CORM-2 or NaHS but not with PAG decreased ASA-damage and increased GBF. ZnPP reversed protective and hyperemic effect of NaHS but PAG failed to affect CORM-2-induced gastroprotection. CORM-2 elevated CO content, mRNA or protein expression for HO-1, Nrf-2, and decreased expression of CBS, HIF-1α, COX-2, IL-1β, iNOS, the H2S production in gastric mucosa and COHb concentration in blood. NaHS raised mRNA or protein expression for CSE, COX-1 and decreased mRNA expression for IL-1β and COHb level in blood.We conclude that CO is involved in gastroprotection induced by H2S while beneficial protective action of CO released from CORM-2 in gastric mucosa seems to be H2S-independent. In contrast to H2S, CO ameliorates hypoxia, regulates Nrf-2 expression but similarly to H2S acts on sGC-dependent manner to restore gastric microcirculation and exhibit anti-inflammatory activity in gastric mucosa compromised by ASA.

The spectrum of gastric pathology in portal hypertension—An endoscopic and pathologic study of 550 cases

One of the main tasks for pathologists when evaluating gastric biopsies from patients with portal hypertensive gastropathy (PHG) is to examine whether there is increased mucosal vasculature as suggested by endoscopy. However, the full spectrum of pathology findings in patients with portal hypertension (pHTN) is largely unknown. We systematically characterized the endoscopic and pathologic features in gastric biopsies from pHTN patients (study group) and compared with those from patients without pHTN (control group). The study group consisted of 550 consecutive surveillance esophagogastroduodenoscopic (EGD) biopsies, whereas the control group included 281 consecutive EGD biopsies for a variety of indications. As expected, the endoscopic prevalence of PHG was 28%, among which two-thirds showed corresponding histopathologic evidence of increased vasculature. However, non-Helicobacter pylori gastritis was the most common finding in pHTN patients on histology (40%). In addition, hyperplastic polyp was also more common in pHTN patients than in controls (6% vs 3%; P=0.0314). In contrast, pathology findings of nonspecific reactive changes (29% vs 51%; P<0.0001), proton pump inhibitor-related changes (16% vs 30%; P<0.0001), and malignancy (1% vs 3%; P=0.0138) were less common in pHTN patients. Our results show a spectrum of gastric endoscopic and pathologic findings in pHTN patients. The predominant gastric pathology in pHTN patients may be associated with pHTN-induced gastric microcirculation impairment.