Pravastatin Improves Colonic and Hepatic Microcirculatory Oxygenation during Sepsis without Affecting Mitochondrial Function and ROS Production in Rats.

Microcirculatory and mitochondrial dysfunction are considered the main mechanisms of septic shock. Studies suggest that statins modulate inflammatory response, microcirculation, and mitochondrial function, possibly through their action on peroxisome proliferator-activated receptor alpha (PPAR-α). The aim of this study was to examine the effects of pravastatin on microcirculation and mitochondrial function in the liver and colon and the role of PPAR-α under septic conditions. This study was performed with the approval of the local animal care and use committee. Forty Wistar rats were randomly divided into 4 groups: sepsis (colon ascendens stent peritonitis, CASP) without treatment as control, sepsis + pravastatin, sepsis + PPAR-α-blocker GW6471, and sepsis + pravastatin + GW6471. Pravastatin (200 µg/kg s.c.) and GW6471 (1 mg/kg) were applied 18 h before CASP-operation. 24 h after initial surgery, a relaparotomy was performed, followed by a 90 min observation period for assessment of microcirculatory oxygenation (µHbO2) of the liver and colon. At the end of the experiments, animals were euthanized, and the colon and liver were harvested. Mitochondrial function was measured in tissue homogenates using oximetry. The ADP/O ratio and respiratory control index (RCI) for complexes I and II were calculated. Reactive oxygen species (ROS) production was assessed using the malondialdehyde (MDA)-Assay. Statistics: two-way analysis of variance (ANOVA) + Tukey's/Dunnett's post hoc test for microcirculatory data, Kruskal-Wallis test + Dunn's post hoc test for all other data. In control septic animals µHbO2 in liver and colon deteriorated over time (µHbO2: -9.8 ± 7.5%* and -7.6 ± 3.3%* vs. baseline, respectively), whereas after pravastatin and pravastatin + GW6471 treatment µHbO2 remained constant (liver: µHbO2 pravastatin: -4.21 ± 11.7%, pravastatin + GW6471: -0.08 ± 10.3%; colon: µHbO2 pravastatin: -0.13 ± 7.6%, pravastatin + GW6471: -3.00 ± 11.24%). In both organs, RCI and ADP/O were similar across all groups. The MDA concentration remained unchanged in all groups. Therefore, we conclude that under septic conditions pravastatin improves microcirculation in the colon and liver, and this seems independent of PPAR-α and without affecting mitochondrial function.

Gemfibrozil Improves Microcirculatory Oxygenation of Colon and Liver without Affecting Mitochondrial Function in a Model of Abdominal Sepsis in Rats.

Recent studies observed, despite an anti-hyperlipidaemic effect, a positive impact of fibrates on septic conditions. This study evaluates the effects of gemfibrozil on microcirculatory variables, mitochondrial function, and lipid peroxidation levels with regard to its potential role as an indicator for oxidative stress in the colon and liver under control and septic conditions and dependencies on PPARα-mediated mechanisms of action. With the approval of the local ethics committee, 120 Wistar rats were randomly divided into 12 groups. Sham and septic animals were treated with a vehicle, gemfibrozil (30 and 100 mg/kg BW), GW 6471 (1 mg/kg BW, PPARα inhibitor), or a combination of both drugs. Sepsis was induced via the colon ascendens stent peritonitis (CASP) model. Then, 24 h post sham or CASP surgery, a re-laparotomy was performed. Measures of vital parameters (heart rate (HR), mean arterial pressure (MAP), and microcirculation (µHbO2)) were recorded for 90 min. Mitochondrial respirometry and assessment of lipid peroxidation via a malondialdehyde (MDA) assay were performed on colon and liver tissues. In the untreated sham animals, microcirculation remained stable, while pre-treatment with gemfibrozil showed significant decreases in the microcirculatory oxygenation of the colon. In the CASP animals, µHbO2 levels in the colon and the liver were significantly decreased 90 min after laparotomy. Pre-treatment with gemfibrozil prevented the microcirculatory aberrations in both organs. Gemfibrozil did not affect mitochondrial function and lipid peroxidation levels in the sham or CASP animals. Gemfibrozil treatment influences microcirculation depending on the underlying condition. Gemfibrozil prevents sepsis-induced microcirculatory aberrances in the colon and liver PPARα-independently. In non-septic animals, gemfibrozil impairs the microcirculatory variables in the colon without affecting those in the liver.

[Evaluation of the project for the introduction of bystander resuscitation in schools in North Rhine-Westphalia]. / Evaluation des Projekts zur Einführung von Laienreanimation an Schulen in Nordrhein-Westfalen.

BACKGROUND: Teaching of resuscitation measures is not mandatory in all schools in Germany. It is currently limited to individual, partly mandatory projects despite a low bystander resuscitation rate. For this reason, the Ministry for Schools and Education of North Rhine-Westphalia initiated the project "Bystander resuscitation at schools in NRW" in March 2017. OBJECTIVE: The aim of this work was to evaluate this project. MATERIAL AND METHODS: All secondary schools in North Rhine-Westphalia were invited to participate in the project. Medical partners from each administrative district took part, who carried out resuscitation training with existing concepts for teacher or student training. After a 3-year period, the evaluation was carried out using standardized questionnaires for school headmasters, teachers and students. RESULTS: In total, more than 40,000 pupils from 249 schools in NRW could be trained in resuscitation within the project with 6 different concepts. Of the students 85% answered the questions regarding resuscitation correctly and overall felt safe in resuscitation measures. The one-off investment requirement for all schools is roughly 4-6.5 million € and around 340,000 € in each budget year. CONCLUSION: A legal constitution and funding are necessary for a nationwide introduction of resuscitation in schools. All established concepts are effective, therefore each school can use them exactly according to their needs, optimally in a stepped form. Training for teachers should focus on resuscitation.

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

BACKGROUND: Hypercapnia 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. METHODS: In 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. RESULTS: During 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). CONCLUSIONS: Exogenous 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.

Melatonin pretreatment improves gastric mucosal blood flow and maintains intestinal barrier function during hemorrhagic shock in dogs.

OBJECTIVE: Melatonin improves hepatic perfusion after hemorrhagic shock and may reduce stress-induced gastric lesions. This study was designed to investigate whether pretreatment with melatonin may influence gastric mucosal microcirculatory perfusion (µflow), oxygenation (µHbO2 ), or intestinal barrier function during physiological and hemorrhagic conditions in dogs. METHODS: In a randomized crossover study, five anesthetized foxhounds received melatonin 100 µg kg-1 or vehicle (ethanol 5%) intravenously in the absence or presence of hemorrhagic shock (60 minutes, -20% blood volume). Systemic hemodynamic variables, gastric mucosal perfusion, and oxygenation were recorded continuously; intestinal barrier function was assessed intermittently via xylose absorption. RESULTS: During hemorrhagic shock, melatonin significantly attenuated the decrease in µflow, compared with vehicle (-19±9 vs -43±10 aU, P<.05), without influence on µHbO2 . A significant increase in xylose absorption was detected during hemorrhage in vehicle-treated dogs, compared with sham-operated animals (13±2 vs 8±1 relative amounts, P<.05); this was absent in melatonin-treated animals (6±1 relative amounts). Melatonin did not influence macrocirculation. CONCLUSIONS: Melatonin improves regional blood flow suggesting improved oxygen delivery in gastric mucosa during hemorrhagic shock. This could provide a mechanism for the observed protection of intestinal barrier function in dogs.

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.

Vasopressin V1A receptors mediate the stabilization of intestinal mucosal oxygenation during hypercapnia in septic rats.

BACKGROUND: Microvascular oxygen saturation (µHBO2) plays an essential role in the development and outcome of sepsis. Hypercapnia (HC) improves the microvascular oxygenation of the mucosa in both healthy and septic animals. Vasopressin V1A receptor blockade prevents this positive effect under otherwise physiological conditions. The aim of this study was to investigate the effects and mechanisms of the vasopressin system during hypercapnia under septic conditions. METHODS: 80 rats were randomized into 8 groups (N=10). Colon ascendens stent peritonitis (CASP) or sham surgery was performed on 40 animals each to establish a moderate polymicrobial sepsis or sham control, respectively. 24h after sepsis induction the animals were subjected to 120min of volume-controlled and pressure-limited ventilation with either normocapnic (pCO2 35-45mmHg) or moderate hypercapnic (pCO2 of 65-75mmHg) ventilation targets. Animals received either vasopressin V1A receptor blockade (SR 49059, 1mgkg(-1) i.v.) or vehicle solution (dimethyl sulfoxide, 1%). Blood pressure, heart rate, pO2 and pCO2 were measured and microcirculatory oxygenation (µHBO2) and microcirculatory flow (µflow) were recorded using tissue reflectance spectrophotometry. Oxygen supply (µDO2) and consumption (µVO2) were calculated from intermittent blood gas analysis. RESULTS: In septic animals, µHBO2 declined during normocapnia (-11±10.3) but remained unchanged during hypercapnia. µHBO2 declined with vasopressin V1A receptor blockade both during normocapnia (-7.4±10.6) and hypercapnia (-9.2±9.8). Microcirculatory oxygen consumption was significantly reduced by hypercapnia in septic animals (-2.4·10(5) [AU]±2.4·10(5) [AU]). In sham animals, µHBO2 and µVO2 did not change. CONCLUSION: Vasopressin V1A receptors mediate the beneficial effects of hypercapnia on microcirculatory oxygenation during sepsis. The effects of vasopressin on µHBO2 might be related to decreased oxygen consumption during hypercapnia.

The beneficial effects of acute hypercapnia on microcirculatory oxygenation in an animal model of sepsis are independent of K(+)ATP channels.

BACKGROUND: Acute hypercapnia maintains the microcirculatory oxygenation of the splanchnic region during sepsis. The first aim of this study was to characterize the role of K(+)ATP channels on the microcirculatory flow and oxygenation during acute moderate hypercapnia. The second aim was to investigate whether a short period of hypercapnia induces detrimental effects in an otherwise undamaged rodent lung. METHODS: Experiments were performed on 60 male Wistar rats. A moderate polymicrobial sepsis was induced by colon ascendens stent peritonitis (CASP) surgery. 24h after induction of sepsis volume-controlled and pressure-limited ventilation was established for 120 min, with either normocapnic (pCO2 35-45 mmHg) or moderate hypercapnic ventilation targets (pCO2 65-75 mmHg) and with or without non-selective K(+)ATP channel blockade with glibenclamide. Microcirculatory blood flow of the colonic wall as well as oxygen delivery and consumption were assessed with tissue laser Doppler and reflectance spectrophotometry. Hemodynamic variables were recorded and plasma cytokine levels and myeloperoxidase levels of the lungs were analyzed. RESULTS: In septic animals microcirculatory oxygenation deteriorated progressively with normocapnia (-11.7 ± 11.8%) but was maintained (-2.9 ± 5.6%) with hypercapnia. This effect was associated with an increased microcirculatory oxygen consumption in septic animals with normocapnia (+25.7 ± 37.1%) that was decreased in the hypercapnia groups (-7.2 ± 28.1%). The effect of hypercapnia in septic animals was not altered by additional K(+)ATP channel blockade (-5.7 ± 32.7%). Hypercapnia neither induced an inflammatory response in lungs nor altered the systemic cytokine response. CONCLUSIONS: The observed beneficial effect of hypercapnia on microvascular oxygenation of the colon in sepsis does not seem to be mediated via K(+)ATP channels.

[Development of violence-associated penetrating trauma in the Düsseldorf metropolitan region over a 5-year period (GewPen study)]. / Entwicklung gewaltassoziierter penetrierender Traumata in der Metropolregion Düsseldorf über einen fünfjährigen Zeitraum (GewPen-Studie).

INTRODUCTION: Penetrating injuries are a rare but recurring emergency situation in the out-of-hospital and in-hospital emergency settings. The purpose of this study was to determine the incidence and characteristics of injuries associated with penetrating violence across a German metropolitan region over a 5-year period. MATERIAL AND METHODS: In the retrospective study, a database query of the control center of the Düsseldorf rescue service area was used to identify and descriptively analyze all rescue service operations with penetrating violence-associated injuries in the years 2015, 2017, and 2019. For those patients who were transferred to the major trauma center, a further analysis of the in-hospital course was performed. RESULTS: In the 3 years 2015, 2017 and 2019 a total of 266 patients (age: 33 ± 14 years, male: 79%) could be recorded (2015 vs. 2017 vs. 2019: n = 81 vs. n = 93 vs. n = 92, respectively). The most common age group involved had an age range of 15-34 years. A particularly higher frequency of emergency calls was found for the areas of Old Town, City Center, and one other district (Oberbilk). A high frequency of rescue missions was found in the nights from Saturday to Sunday between 20.00 p.m. and 04.00 a.m. Rescue missions with emergency physicians on board increased over the years (2015 vs. 2019: 27 vs. 42%, p = 0.04). The primary weapons used were knives (56%), broken glass bottles (18%) and broken glasses (6%). Out of all patients 71 (27%, injury severity score 11 ± 14) were admitted to the major trauma center. Among these patients, the proportion of immediate surgical care (2015 vs. 2019: 20% vs. 35%, p < 0.05) and positive alcohol detection increased over the years (2015 vs. 2019: 10% vs. 43%, p < 0.05). The 30-day mortality in the 3 years studied was 1.1% (n = 3). CONCLUSION: Penetrating injuries associated with violence are relevant but rare rescue missions. Future care strategies should focus on deployment of rescue resources close to the scene of the incident ("old town guard", central station), and prevention strategies should focus on weapon prohibition zones. A control of alcohol consumption should be discussed.

Local carbachol application induces oral microvascular recruitment and improves gastric tissue oxygenation during hemorrhagic shock in dogs.

Introduction: Hemorrhagic shock is characterized by derangements of the gastrointestinal microcirculation. Topical therapy with nitroglycerine or iloprost improves gastric tissue oxygenation but not regional perfusion, probably due to precapillary adrenergic innervation. Therefore, this study was designed to investigate the local effect of the parasympathomimetic carbachol alone and in combination with either nitroglycerine or iloprost on gastric and oral microcirculation during hemorrhagic shock. Methods: In a cross-over design five female foxhounds were repeatedly randomized into six experimental groups. Carbachol, or carbachol in combination with either nitroglycerine or iloprost were applied topically to the oral and gastric mucosa. Saline, nitroglycerine, or iloprost application alone served as control groups. Then, a fixed-volume hemorrhage was induced by arterial blood withdrawal followed by blood retransfusion after 1h of shock. Gastric and oral microcirculation was determined using reflectance spectrophotometry and laser Doppler flowmetry. Oral microcirculation was visualized with videomicroscopy. Statistics: 2-way-ANOVA for repeated measurements and Bonferroni post-hoc analysis (mean ± SEM; p < 0.05). Results: The induction of hemorrhage led to a decrease of gastric and oral tissue oxygenation, that was ameliorated by local carbachol and nitroglycerine application at the gastric mucosa. The sole use of local iloprost did not improve gastric tissue oxygenation but could be supplemented by local carbachol treatment. Adding carbachol to nitroglycerine did not further increase gastric tissue oxygenation. Gastric microvascular blood flow remained unchanged in all experimental groups. Oral microvascular blood flow, microvascular flow index and total vessel density decreased during shock. Local carbachol supply improved oral vessel density during shock and oral microvascular flow index in the late course of hemorrhage. Conclusion: The specific effect of shifting the autonomous balance by local carbachol treatment on microcirculatory variables varies between parts of the gastrointestinal tract. Contrary to our expectations, the improvement of gastric tissue oxygenation by local carbachol or nitroglycerine application was not related to increased microvascular perfusion. When carbachol is used in combination with local vasodilators, the additional effect on gastric tissue oxygenation depends on the specific drug combination. Therefore, modulation of tissue oxygen consumption, mitochondrial function or alterations in regional blood flow distribution should be investigated.

Effects of remote ischemic preconditioning on early markers of intestinal injury in experimental hemorrhage in rats.

The maintenance of intestinal integrity and barrier function under conditions of restricted oxygen availability is crucial to avoid bacterial translocation and local inflammation. Both lead to secondary diseases after hemorrhagic shock and might increase morbidity and mortality after surviving the initial event. Monitoring of the intestinal integrity especially in the early course of critical illness remains challenging. Since microcirculation and mitochondrial respiration are main components of the terminal stretch of tissue oxygenation, the evaluation of microcirculatory and mitochondrial variables could identify tissues at risk during hypoxic challenges, indicate an increase of intestinal injury, and improve our understanding of regional pathophysiology during acute hemorrhage. Furthermore, improving intestinal microcirculation or mitochondrial respiration, e.g. by remote ischemic preconditioning (RIPC) that was reported to exert a sufficient tissue protection in various tissues and was linked to mediators with vasoactive properties could maintain intestinal integrity. In this study, postcapillary oxygen saturation (µHbO2), microvascular flow index (MFI) and plasmatic D-lactate concentration revealed to be early markers of intestinal injury in a rodent model of experimental hemorrhagic shock. Mitochondrial function was not impaired in this experimental model of acute hemorrhage. Remote ischemic preconditioning (RIPC) failed to improve intestinal microcirculation and intestinal damage during hemorrhagic shock.

Acute, short-term hypercapnia improves microvascular oxygenation of the colon in an animal model of sepsis.

INTRODUCTION: The deterioration of microcirculatory oxygenation of the gut plays a vital role in the development of sepsis. Acute hypercapnia enhances the microcirculatory oxygenation of the splanchnic region under physiological conditions, while the effect of hypercapnia under sepsis is unknown. The aim of this study was to investigate the effects of acute hypercapnia and hypercapnic acidosis on the colonic microcirculation and early cytokine response in polymicrobial sepsis. METHODS: Experiments were performed on 103 male Wistar rats. Colon ascendens stent peritonitis (CASP) surgery with varying stent diameters was conducted to establish a moderate polymicrobial sepsis model. In a second series, 24h of sepsis development induced by CASP surgery was followed by 120min of volume-controlled and pressure-limited ventilation with either normocapnic (pCO2 45±5mmHg) or moderate hypercapnic ventilation targets (pCO2 75±5mmHg) via exogenous carbon dioxide application. The effect of acidosis was investigated by metabolically buffering the hypercapnic acidosis with tromethamine. Microcirculatory oxygenation of the colon wall (tissue reflectance spectrophotometry) and hemodynamic variables were recorded continuously and arterial blood gas and cytokine (TNF-α, IL-6, IL-10) levels were analyzed intermittently. RESULTS: In septic animals the microcirculatory oxygenation of the colon deteriorated under normocapnia (-7.0±7.6% at 90min) but was maintained under hypercapnic acidosis (+3.6±7.6%) and buffered hypercapnia (+1.5±4.4%). Cytokine levels were significantly higher in septic animals as opposed to sham animals but did not differ between normocapnic and hypercapnic groups. CONCLUSIONS: Acute hypercapnic acidosis and buffered hypercapnia both improve splanchnic microcirculatory oxygenation in a septic animal model, thereby counteracting the adverse effect induced by sepsis. The circulating pro- and anti-inflammatory cytokine levels are not modulated after 120min of hypercapnia.

Neither inhalative nor intravenous application of carbon monoxide modifies gastric mucosal oxygenation.

This study was designed to compare the effects of different ways of administering carbon monoxide (intravenous and inhalative) on gastric mucosal oxygenation in a canine model of hemorrhage. Six chronically instrumented dogs were repeatedly anesthetized and randomized to each of the following protocols: In a first series the animals were ventilated either with 100 ppm carbon monoxide (CO) or without followed by hemorrhage and re-transfusion. In a second series a saturated CO solution was infused, compared to normal saline, again followed by hemorrhage and re-transfusion. In a control series, animals received either CO-saline or saline without any further intervention. Microvascular oxygenation of the gastric mucosa (µHbO2) was assessed continuously by tissue reflectance spectrophotometry. Cardiac output was measured intermittently and oxygen delivery (DO2) was calculated. The application of CO, inhalative and intravenous, increased carboxyhemoglobin levels without effect on µHbO2. Hemorrhage reduced µHbO2 in all groups, paralleled by a reduction in DO2 without any differences between groups related to the application of CO. Neither intravenous nor inhalative application of CO alters µHbO2 during physiological conditions or during hemorrhage. Thus, independent of the application way, low dose CO does not seem to modulate regional mucosal oxygenation in cytoprotective concentrations.

Local Mucosal CO2 but Not O2 Insufflation Improves Gastric and Oral Microcirculatory Oxygenation in a Canine Model of Mild Hemorrhagic Shock.

Introduction: Acute hemorrhage results in perfusion deficit and regional hypoxia. Since failure of intestinal integrity seem to be the linking element between hemorrhage, delayed multi organ failure, and mortality, it is crucial to maintain intestinal microcirculation in acute hemorrhage. During critical bleeding physicians increase FiO2 to raise total blood oxygen content. Likewise, a systemic hypercapnia was reported to maintain microvascular oxygenation (µHbO2). Both, O2 and CO2, may have adverse effects when applied systemically that might be prevented by local application. Therefore, we investigated the effects of local hyperoxia and hypercapnia on the gastric and oral microcirculation. Methods: Six female foxhounds were anaesthetized, randomized into eight groups and tested in a cross-over design. The dogs received a local CO2-, O2-, or N2-administration to their oral and gastric mucosa. Hemorrhagic shock was induced through a withdrawal of 20% of estimated blood volume followed by retransfusion 60 min later. In control groups no shock was induced. Reflectance spectrophotometry and laser Doppler were performed at the gastric and oral surface. Oral microcirculation was visualized by incident dark field imaging. Systemic hemodynamic parameters were recorded continuously. Statistics were performed using a two-way-ANOVA for repeated measurements and post hoc analysis was conducted by Bonferroni testing (p < 0.05). Results: The gastric µHbO2 decreased from 76 ± 3% to 38 ± 4% during hemorrhage in normocapnic animals. Local hypercapnia ameliorated the decrease of µHbO2 from 78 ± 4% to 51 ± 8%. Similarly, the oral µHbO2 decreased from 81 ± 1% to 36 ± 4% under hemorrhagic conditions and was diminished by local hypercapnia (54 ± 4%). The oral microvascular flow quality but not the total microvascular blood flow was significantly improved by local hypercapnia. Local O2-application failed to change microvascular oxygenation, perfusion or flow quality. Neither CO2 nor O2 changed microcirculatory parameters and macrocirculatory hemodynamics under physiological conditions. Discussion: Local hypercapnia improved microvascular oxygenation and was associated with a continuous blood flow in hypercapnic individuals undergoing hemorrhagic shock. Local O2 application did not change microvascular oxygenation, perfusion and blood flow profiles in hemorrhage. Local gas application and change of microcirculation has no side effects on macrocirculatory parameters.

A Toolbox to Investigate the Impact of Impaired Oxygen Delivery in Experimental Disease Models.

Impaired oxygen utilization is the underlying pathophysiological process in different shock states. Clinically most important are septic and hemorrhagic shock, which comprise more than 75% of all clinical cases of shock. Both forms lead to severe dysfunction of the microcirculation and the mitochondria that can cause or further aggravate tissue damage and inflammation. However, the detailed mechanisms of acute and long-term effects of impaired oxygen utilization are still elusive. Importantly, a defective oxygen exploitation can impact multiple organs simultaneously and organ damage can be aggravated due to intense organ cross-talk or the presence of a systemic inflammatory response. Complexity is further increased through a large heterogeneity in the human population, differences in genetics, age and gender, comorbidities or disease history. To gain a deeper understanding of the principles, mechanisms, interconnections and consequences of impaired oxygen delivery and utilization, interdisciplinary preclinical as well as clinical research is required. In this review, we provide a "tool-box" that covers widely used animal disease models for septic and hemorrhagic shock and methods to determine the structure and function of the microcirculation as well as mitochondrial function. Furthermore, we suggest magnetic resonance imaging as a multimodal imaging platform to noninvasively assess the consequences of impaired oxygen delivery on organ function, cell metabolism, alterations in tissue textures or inflammation. Combining structural and functional analyses of oxygen delivery and utilization in animal models with additional data obtained by multiparametric MRI-based techniques can help to unravel mechanisms underlying immediate effects as well as long-term consequences of impaired oxygen delivery on multiple organs and may narrow the gap between experimental preclinical research and the human patient.

Tissue Damage, Not Infection, Triggers Hepatic Unfolded Protein Response in an Experimental Rat Peritonitis Model.

Background: Abdominal surgery is an efficient treatment of intra-abdominal sepsis. Surgical trauma and peritoneal infection lead to the activation of multiple pathological pathways. The liver is particularly susceptible to injury under septic conditions. Liver function is impaired when pathological conditions induce endoplasmic reticulum (ER) stress. ER stress triggers the unfolded protein response (UPR), aiming at restoring ER homeostasis, or inducing cell death. In order to translate basic knowledge on ER function into the clinical setting, we aimed at dissecting the effect of surgery and peritoneal infection on the progression of ER stress/UPR and inflammatory markers in the liver in a clinically relevant experimental animal model. Methods: Wistar rats underwent laparotomy followed by colon ascendens stent peritonitis (CASP) or surgery (sham) only. Liver damage (aspartate aminotransferase (AST), alanine aminotransferase (ALT) and De Ritis values), inflammatory and UPR markers were assessed in livers at 24, 48, 72, and 96 h postsurgery. Levels of inflammatory (IL-6, TNF-α, iNOS, and HO-1), UPR (XBP1, GRP78, CHOP), and apoptosis (BAX/Bcl-XL) mRNA were determined by qPCR. Splicing of XBP1 (XBP1s) was analyzed by gel electrophoresis, p-eIF2α and GRP78 protein levels using the western blots. Results: Aspartate aminotransferase levels were elevated 24 h after surgery and thereafter declined with different kinetics in sham and CASP groups. Compared with sham De Ritis ratios were significantly higher in the CASP group, at 48 and 96 h. CASP induced an inflammatory response after 48 h, evidenced by elevated levels of IL-6, TNF-α, iNOS, and HO-1. In contrast, UPR markers XBP1s, p-eIF2α, GRP78, XBP1, and CHOP did not increase in response to infection but paralleled the kinetics of AST and De Ritis ratios. We found that inflammatory markers were predominantly associated with CASP, while UPR markers were associated with surgery. However, in the CASP group, we found a stronger correlation between XBP1s, XBP1 and GRP78 with damage markers, suggesting a synergistic influence of inflammation on UPR in our model. Conclusion: Our results indicate that independent mechanisms induce ER stress/UPR and the inflammatory response in the liver. While peritoneal infection predominantly triggers inflammatory responses, the conditions associated with organ damage are predominant triggers of the hepatic UPR.

Colon Ascendens Stent Peritonitis (CASP ).

Colon ascendens stent peritonitis (CASP) is one of the well-established models of experimental abdominal sepsis. In CASP surgery, an open link between the gut lumen and the abdominal cavity is created by placing a stent into the colon ascendens. This mimics well the insufficient intestinal anastomosis. It causes a continuous leakage of the gut contents into the peritoneum and leads therefore to peritonitis and sepsis. The abdominal cavity is opened under general anesthesia and a plastic stent is located through and sutured to the colonic wall. The septic severity in CASP models can be titrated by altering the size of the stent catheter. Therefore, CASP models with small stents sizes are suitable for long-term studies and studies with mild/moderate sepsis severity. Within 24 h, animals develop clinical signs of sepsis. Monitoring of the clinical state, sufficient analgesia, appropriate antibiotics and fluid resuscitation should be performed postoperatively.

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

INTRODUCTION: Sepsis 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. METHODS: 40 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. RESULTS: In 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. CONCLUSION: Sub-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.

Sodium Thiosulfate Improves Intestinal and Hepatic Microcirculation Without Affecting Mitochondrial Function in Experimental Sepsis.

Introduction: In the immunology of sepsis microcirculatory and mitochondrial dysfunction in the gastrointestinal system are important contributors to mortality. Hydrogen sulfide (H2S) optimizes gastrointestinal oxygen supply and mitochondrial respiration predominantly via K(ATP)-channels. Therefore, we tested the hypothesis that sodium thiosulfate (STS), an inducer of endogenous H2S, improves intestinal and hepatic microcirculation and mitochondrial function via K(ATP)-channels in sepsis. Methods: In 40 male Wistar rats colon ascendens stent peritonitis (CASP) surgery was performed to establish sepsis. Animals were randomized into 4 groups (1: STS 1 g â€¢ kg-1 i.p., 2: glibenclamide (GL) 5 mg • kg-1 i.p., 3: STS + GL, 4: vehicle (VE) i.p.). Treatment was given directly after CASP-surgery and 24 hours later. Microcirculatory oxygenation (µHBO2) and flow (µflow) of the colon and the liver were continuously recorded over 90 min using tissue reflectance spectrophotometry. Mitochondrial oxygen consumption in tissue homogenates was determined with respirometry. Statistic: two-way ANOVA + Dunnett´s and Tukey post - hoc test (microcirculation) and Kruskal-Wallis test + Dunn's multiple comparison test (mitochondria). p < 0.05 was considered significant. Results: STS increased µHbO2 (colon: 90 min: + 10.4 ± 18.3%; liver: 90 min: + 5.8 ± 9.1%; p < 0.05 vs. baseline). Furthermore, STS ameliorated µflow (colon: 60 min: + 51.9 ± 71.1 aU; liver: 90 min: + 22.5 ± 20.0 aU; p < 0.05 vs. baseline). In both organs, µHbO2 and µflow were significantly higher after STS compared to VE. The combination of STS and GL increased colonic µHbO2 and µflow (µHbO2 90 min: + 8.7 ± 11.5%; µflow: 90 min: + 41.8 ± 63.3 aU; p < 0.05 vs. baseline), with significantly higher values compared to VE. Liver µHbO2 and µflow did not change after STS and GL. GL alone did not change colonic or hepatic µHbO2 or µflow. Mitochondrial oxygen consumption and macrohemodynamic remained unaltered. Conclusion: The beneficial effect of STS on intestinal and hepatic microcirculatory oxygenation in sepsis seems to be mediated by an increased microcirculatory perfusion and not by mitochondrial respiratory or macrohemodynamic changes. Furthermore, the effect of STS on hepatic but not on intestinal microcirculation seems to be K(ATP)-channel-dependent.

Perioperative liver protection.

PURPOSE OF REVIEW: This review presents important pathophysiological alterations associated with impaired liver function and discusses protective perioperative strategies and the various anaesthetic agents recommended. RECENT FINDINGS: Perioperative liver impairment is a serious complication of anaesthesia and surgery. Unfortunately, clinicians are provided with only crude macrohaemodynamic monitoring devices to optimize their therapy. Technical improvements have revealed some complex mysteries of perioperative microcirculatory alterations and have disclosed a large heterogeneity between different vascular beds. The present review will critically discuss current clinical concepts of optimizing global haemodynamic variables and the often contrasting effects of vasoactive agents on the microcirculatory nutritional blood flow. Finally, promising protective experimental interventions of pharmacological or ischaemic preconditioning are presented and their often disillusioning transition into recent clinical trials is highlighted. SUMMARY: Targeted perioperative liver protection still lacks adequate monitoring tools and is currently based on optimization of global haemodynamic variables. While there is currently no evidence suggesting a positive effect of ischaemic preconditioning, promising experimental results of pharmacological preconditioning and therapeutic hypothermia require further evaluation in larger randomized clinical trials.