BACKGROUND:Hypotension and bradycardia are known side effects of general anesthesia, while little is known about further macro- and microhemodynamic changes during induction. Intriguing is furthermore, why some patients require no vasopressor medication to uphold mean arterial pressure, while others need vasopressor support.OBJECTIVE:Determination of macro- and microhemodynamic changes during induction of general anesthesia.METHODS:We enrolled 150 female adults scheduled for gynaecological surgery into this prospective observational, single-blinded trial. Besides routinely measuring heart rate (HR) and mean arterial blood pressure (MAP), the non-invasive technique of thoracic electrical bioimpedance was applied to measure cardiac output (CO), cardiac index (CI), stroke volume (SV), stroke volume variability (SVV) and index of myocardial contractility (ICON) before induction of anesthesia, 7 times during induction, and, finally, after surgery in the recovery room. Changes in microcirculation were assessed using sidestream dark field imaging to establish the perfused boundary region (PBR), a validated gauge of glycocalyx health. Comparisons were made with Friedman's or Wilcoxon test for paired data, and with Mann-Whitney-U test for unpaired data, with post-hoc corrections for multiple measurements by the Holm-Bonferroni method.RESULTS:83 patients did not need vasopressor support, whereas 67 patients required therapy (norepinephrine, atropine or cafedrine/theodrenaline) to elevate MAP values to ≥70mmHg during induction, 54 of these receiving norepinephrine (NE) alone. Pre-interventional (basal) values of CO, CI, ICON, SV and SVV were all significantly lower in the group of patients later requiring NE (p < 0.04), whereas HR and MAP were identical for both groups. HR, MAP and CO decreased from baseline to 12 min after induction of general anesthesia in both the patients without and those with NE support. Heart rate decreased significantly by about 25% in both groups (-19 to -21 bpm). The median individual decrease of MAP amounted to -26.7% (19.7/33.3, p < 0.001) and -26.1% (11.6/33.2, p < 0.001), respectively, whereas for CO it was -40.7% (34.1/50.1, p < 0.001) and -43.5% (34.8/48.7). While these relative changes did not differ between the two groups, in absolute values there were significantly greater decreases in CO, CI, SV and ICON in the group requiring NE. Noteably, NE did not restore ICON or the other cardiac parameters to levels approaching those of the group without NE. PBR was measured in a total of 84 patients compiled from both groups, there being no intergroup differences. It increased 6.4% (p < 0.001) from pre-induction to the end of the operation, indicative of damage to microvascular glycocalyx.CONCLUSION:Non-invasive determination of CO provides additional hemodynamic information during anesthesia, showing that induction results in a significant decrease not only of MAP but also of CO and other cardiac factors at all timepoints compared to baseline values. The decrease of CO was greater than that of MAP and, in contrast to MAP, did not respond to NE. There was also no sign of a positive inotropic effect of NE in this situation. Support of MAP by NE must consequently result from an increase in peripheral arterial resistance, posing a risk for oxygen supply to tissue. In addition, general anesthesia and the operative stimulus lead to an impairment of the microcirculation.

The endothelial glycocalyx (EG) is the most luminal layer of the blood vessel, growing on and within the vascular wall. Shedding of the EG plays a central role in many critical illnesses. Degradation of the EG is associated with increased morbidity and mortality. Certain illnesses and iatrogenic interventions can cause degradation of the EG. It is not known whether restitution of the EG promotes the survival of the patient. First trials that focus on the reorganization and/or restitution of the EG seem promising. Nevertheless, the step “from bench to bedside” is still a big one.

BACKGROUND:Patients undergoing cardiac surgery commonly develop systemic inflammation associated with tissue edema, which impairs outcome. One main pathomechanism leading to the edema is the deterioration of the endothelial glycocalyx, a key component of the vascular barrier. In animal models hydro cortisone has proved to be protective for the glycocalyx. OBJECTIVE:This trial evaluates the effect of hydrocortisone on glycocalyx integrity in patients undergoing cardiac surgery with cardiopulmonary bypass. METHODS:In a prospective, randomized interventional pilot trial, 30 patients received either hydrocortisone (100 mg over 10 min) or placebo (saline control) before surgery. Plasma concentrations of glycocalyx constituents (syndecan-1, heparan sulfate) and various clinical parameters (respiratory and renal function, inflammatory markers, use of vasopressors, length of stay at the intensive care unit) were measured. Primary endpoint was a significant difference of glycocalyx constituents in plasma. Comparisons were made with Friedman's and Wilcoxon tests (paired data), or the Kruskal-Wallis and Mann-Whitney U tests (unpaired data). Holm-Bonferroni method was used for post-hoc corrections. RESULTS:Heparan sulfate and syndecan-1 increased significantly during and after cardiac surgery with cardiopulmonary bypass in both groups. Whereas the maximum increase of heparan sulfate was 12.3-fold in the control vs. 3.8-fold in the pretreated group (p < 0.05), syndecan-1 values showed no significant difference between the groups (maximal increase 3-fold). The inflammatory markers C-reactive protein and interleukin-6 were also higher in the control than in the hydrocortisone group, but there was no difference in patient mortality (zero), or in any clinical parameters. CONCLUSIONS:Pretreatment with hydrocortisone ameliorated shedding of heparan sulfate, a major constituent of the endothelial glycocalyx, in patients undergoing cardiac surgery with cardiopulmonary bypass, but had no relevant influence on various clinical parameters or patient mortality. The relatively small number of patients in this pilot study probably precluded detection of positive outcome differences.

BACKGROUND: The endothelial glycocalyx plays a decisive role in maintaining vascular homeostasis. Previous animal models have mainly focused on in-vitro experiments or the isolated beating guinea pig heart. To further evaluate underlying mechanisms of up-and down regulation, knock-out animals seem to be a promising option. OBJECTIVE: Aim of the present study was to evaluate if an isolated mouse-heart model is suitable for glycocalyx research. METHODS: Isolated beating mouse hearts (C57/Bl6J) underwent warm, no-flow ischemia and successive reperfusion. Coronary effluent was analyzed by ELISA and Western blot for the glycocalyx core protein: syndecan-1. Hearts were prepared for either immunofluorescence or electron microscopy and lysed for Western blot analysis. RESULTS: An endothelial glycocalyx covering the total capillary circumference and syndecan-1 were detected by electron and immunofluorescence microscopy. Ischemia/reperfusion seriously deteriorated both findings. Confoundingly, syndecan-1 was not detectable either in the coronary effluent or in the lysates of blood-free hearts by ELISA or Western blot technique. CONCLUSIONS: Blood vessels of mouse hearts contain an endothelial glycocalyx comparable to that of other animals also with respect to its core protein syndecan-1. But, for studies including quantification of intravascular soluble glycocalyx constituents, the amount of syndecan-1 in mouse hearts seems to be too low.

Background: Cardiac surgery often causes ischemia and development of a systemic inflammatory response syndrome, which impairs vascular barrier function, normally maintained by the endothelial cell line and the endothelial glycocalyx (EG). The EG normally covers and protects healthy endothelial cells throughout the vasculature. The aim of the present study was to assess the disruption of the cellular part of the microvascular barrier by determining parameters of endothelial cell activation known to influence and reflect cell-cell junctional integrity. Particular attention was placed on angiopoietins and their important effects on endothelial gap junctions. Furthermore, comparative measurements were undertaken in patients undergoing on- and off-pump cardiac surgery, the latter group presumably experiencing less ischemic stress. Methods: 30 patients undergoing elective coronary artery bypass surgery were assigned to the conventional coronary artery bypass (CCAB) group (n = 15) or the off-pump coronary artery bypass grafting (OPCAB) group (n = 15). Blood samples were obtained for measuring angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), vascular endothelial (VE)-cadherin, and endocan at various time points. Results: There were significant increases in all measured parameters in both study groups versus the respective basal values. Maximal increases were as follows: Ang-1: CCAB +220%, OPCAB +166%, p < 0.05 each; Ang-2: CCAB +150%, OPCAB +20%, p < 0.05 each; VE-cadherin: CCAB +87%, OPCAB +66%, p < 0.05 each; endocan: CCAB +323%, OPCAB +72%, p < 0.05 each. Conclusion: The present study demonstrates the activation of endothelial cells, shedding of cell-cell contacts and a potential intrinsic counterregulation by Ang-1 and endocan in patients undergoing major cardiac surgery. Quantitatively greater deviations of parameters in the CCAB than in the OPCAB group suggest a relation between the occurrence of ischemia/reperfusion and the extent of endothelial activation.

Oxygen delivery to cells is the basic prerequisite of life. Within the human body, an ingenious oxygen delivery system, comprising steps of convection and diffusion from the upper airways via the lungs and the cardiovascular system to the microvascular area, bridges the gap between oxygen in the outside airspace and the interstitial space around the cells. However, the complexity of this evolutionary development makes us prone to pathophysiological problems. While those problems related to respiration and macrohemodynamics have already been successfully addressed by modern medicine, the pathophysiology of the microcirculation is still often a closed book in daily practice. Nevertheless, here as well, profound physiological understanding is the only key to rational therapeutic decisions. The prime guarantor of tissue oxygenation is tissue blood flow. Therefore, on the premise of intact macrohemodynamics, the microcirculation has three major responsibilities: 1) providing access for oxygenated blood to the tissues and appropriate return of volume; 2) maintaining global tissue flood flow, even in the face of changes in central blood pressure; and 3) linking local blood flow to local metabolic needs. It is an intriguing concept of nature to do this mainly by local regulatory mechanisms, impacting primarily on flow resistance, be this via endothelial or direct smooth muscle actions. The final goal of microvascular blood flow per unit of time is to ensure the needed exchange of substances between tissue and blood compartments. The two principle means of accomplishing this are diffusion and filtration. While simple diffusion is the quantitatively most important form of capillary exchange activity for the respiratory gases, water flux across the blood-brain barrier is facilitated via preformed specialized channels, the aquaporines. Beyond that, the vascular barrier is practically nowhere completely tight for water, with paracellular filtration giving rise to generally low but permanent fluid flux outwards into the interstitial space at the microvascular high pressure segment. At the more leaky venular aspect, both filtration and diffusion allow for bidirectional passage of water, nutrients, and waste products. We are just beginning to appreciate that a major factor for maintaining tissue fluid homeostasis appears to be the integrity of the endothelial glycocalyx.

Glycosaminoglycan hyaluronan (HA), a major constituent of the endothelial glycocalyx, helps to maintain vascular integrity. Preconditioning the heart with volatile anesthetic agents protects against ischemia/reperfusion injury. We investigated a possible protective effect of sevoflurane on the glycocalyx, especially on HA. The effect of pre-ischemic treatment with sevoflurane (15 minutes at 2% vol/vol gas) on shedding of HA was evaluated in 28 isolated, beating guinea pig hearts, subjected to warm ischemia (20 minutes at 37°C) followed by reperfusion (40 minutes), half with and half without preconditioning by sevoflurane. HA concentration was measured in the coronary effluent. Over the last 20 minutes of reperfusion hydroxyethyl starch (1 g%) was continuously infused and the epicardial transudate collected over the last 5 minutes for measuring the colloid extravasation. Additional hearts were fixed by perfusion after the end of reperfusion for immunohistology and electron microscopy. Sevoflurane did not significantly affect post-ischemic oxidative stress, but strongly inhibited shedding of HA during the whole period, surprisingly even prior to ischemia. Immunohistology demonstrated that heparan sulfates and SDC1 of the glycocalyx were also preserved by sevoflurane. Electron microscopy revealed shedding of glycocalyx caused by ischemia and a mostly intact glycocalyx in hearts exposed to sevoflurane. Coronary vascular permeability of the colloid hydroxyethyl starch was significantly decreased by sevoflurane vs the control. We conclude that application of sevoflurane preserves the coronary endothelial glycocalyx, especially HA, sustaining the vascular barrier against ischemic damage. This may explain beneficial effects associated with clinical use of volatile anesthetics against ischemia/reperfusion injury.

BACKGROUND:There is no doubt today about the existence of the endothelial glycocalyx (EG) and its decisive role in maintaining vascular homeostasis in adult humans. Shedding of the EG has been demonstrated in adults with sepsis or trauma, in patients undergoing major operations, and after ischemia/reperfusion. The aim of the present study was to demonstrate whether shedding of the EG also occurs in infants undergoing heart operations. METHODS:Two major constituents of the EG (syndecan-1 and hyaluronan) were measured in the arterial serum of 42 infants during cardiac operations in a prospective observational study. The groups were defined according to the ischemic impact: cardiac operations with cardiopulmonary bypass under beating heart conditions (CPB group, regional ischemia of lungs, n = 10), operations with cardiopulmonary bypass and aortic clamping (CPB+AC group, regional ischemia of heart and lungs, n = 24), and cardiac operations with deep hypothermic circulatory arrest (CPB+AC+DHCA group, whole-body ischemia, n = 8). RESULTS:Syndecan-1 and hyaluronan were detected in all infants, providing an indication for the presence of a glycocalyx. During the operations, no significant difference in syndecan-1 concentration was observed in the CPB group, but levels increased significantly in both other groups (maximum increases: CPB+AC 3.0-fold, CPB+AC+DHCA 3.7-fold, p < 0.05). Hyaluronan increased significantly in the course of the operation in all groups (maximum increases: CPB 1.2-fold, CPB+AC 1.4-fold, CPB+AC+DHCA 1.7-fold, p < 0.05). CONCLUSIONS:The present data provides the first evidence for basal turnover of vascular EG in infants. Similarly to the process in adults, the shedding of this structure increases with ischemia/reperfusion, the extent being dependent on the degree of ischemic challenge.

The endothelial glycocalyx has a profound influence at the vascular wall on the transmission of shear stress, on the maintenance of a selective permeability barrier and a low hydraulic conductivity, and on attenuating firm adhesion of blood leukocytes and platelets. Major constituents of the glycocalyx, including syndecans, heparan sulphates and hyaluronan, are shed from the endothelial surface under various acute and chronic clinical conditions, the best characterized being ischaemia and hypoxia, sepsis and inflammation, atherosclerosis, diabetes, renal disease and haemorrhagic viral infections. Damage has also been detected by in vivo microscopic techniques. Matrix metalloproteases may shed syndecans and heparanase, released from activated mast cells, cleaves heparan sulphates from core proteins. According to new data, not only hyaluronidase but also the serine proteases thrombin, elastase, proteinase 3 and plasminogen, as well as cathepsin B lead to loss of hyaluronan from the endothelial surface layer, suggesting a wide array of potentially destructive conditions. Appropriately, pharmacological agents such as inhibitors of inflammation, antithrombin and inhibitors of metalloproteases display potential to attenuate shedding of the glycocalyx in various experimental models. Also, plasma components, especially albumin, stabilize the glycocalyx and contribute to the endothelial surface layer. Though symptoms of the above listed diseases and conditions correlate with sequelae expected from disturbance of the endothelial glycocalyx (oedema, inflammation, leukocyte and platelet adhesion, low reflow), therapeutic studies to prove a causal connection have yet to be designed. With respect to studies on humans, some clinical evidence exists for benefits from application of sulodexide, a preparation delivering precursors of the glycocalyx constituent heparan sulphate. At present, the simplest option for protecting the glycocalyx seems to be to ensure an adequate level of albumin. However, also in this case, definite proof of causality needs to be delivered.

BACKGROUND Strategies targeting the protection of the vascular barrier, in particular the endothelial glycocalyx, are subjects of current research. Antithrombin III and hydrocortisone have been shown to reduce shedding of the glycocalyx following ischaemia/reperfusion. Platelet adhesion to endothelial cells is one consequence of ischaemia/reperfusion.OBJECTIVE Our goal was to evaluate the effect of pharmacological protection of the glycocalyx on platelet adhesion.DESIGN An experimental interventional animal study.SETTING The study was carried out in a basic science laboratory at the University of Munich.ANIMALS Eighty male guinea pigs (250 to 300 g) were used for the experiment.MAIN OUTCOME MEASURES The effect of preischaemic treatment with hydrocortisone 10 mu g ml(-1) or antithrombin 1 IU ml(-1) on adherence of platelets was evaluated in isolated, beating guinea pig hearts (Langendorff model). Hearts were subjected to warm ischaemia (20 min at 378 degrees C) and consecutive reperfusion. Platelets were injected at the beginning of reperfusion via the aortic cannula and platelet concentration was measured in the effluent (after passing through the coronary vascular system).RESULTS Ischaemia and reperfusion led to significant shedding of the endothelial glycocalyx. Coronary venous release of syndecan-1 increased nine-fold, and heparan sulphate showed a 20.3-fold increase after ischaemia/reperfusion (both P<0.01). Pretreatment with hydrocortisone or antithrombin III reduced endothelial glycocalyx shedding significantly (P<0.05). Adherence of platelets to the coronary vascular bed increased more than 2.5-fold when they were injected during reperfusion. About 40% of this increase was blocked by pretreatment of hearts with hydrocortisone or antithrombin.CONCLUSION Pretreatment with hydrocortisone or antithrombin III can reduce platelet adhesion during reperfusion after warm ischaemia by protection of the endothelial glycocalyx.

INTRODUCTION:Acute normovolemic hemodilution (ANH) and volume loading (VL) are standard blood-sparing procedures. However, VL is associated with hypervolemia, which may cause tissue edema, cardiopulmonary complications and a prolonged hospital stay. The body reacts to hypervolemia with release of atrial natriuretic peptide (ANP) from the heart. ANP has been shown to deteriorate the endothelial glycocalyx, a vital part of the vascular permeability barrier. The aim of the present study was to evaluate and compare ANP release and damage to the glycocalyx during ANH and VL.METHODS:ANH or VL with 6% hydroxyethyl starch 130/0.4 was administered prior to elective surgery in patients of good cardiopulmonary health (n =9 in each group). We measured concentrations of ANP in plasma and of three main constituent parts of the glycocalyx (hyaluronan, heparan sulfate and syndecan 1) in serum before and after ANH or VL. Heparan sulfate and syndecan 1 levels in urine were also determined.RESULTS:In contrast to ANH, VL (20 ml/kg) induced a significant release of ANP (approximately +100%, P <0.05) and increased the serum concentration of two glycocalyx constituents, hyaluronan and syndecan 1 (both by about 80%, P <0.05). Elevation of syndecan 1 was also detected in the urine of patients undergoing VL, but no increase was found in patients undergoing ANH. Heparan sulfate levels were not influenced by either procedure.CONCLUSION:These data suggest that hypervolemia increases the release of ANP and causes enhanced shedding of the endothelial glycocalyx. This perturbation must be expected to impair the vascular barrier, implying that VL may not be as safe as generally assumed and that it should be critically evaluated.

Recent studies showed that considerable amounts of glycosaminoglycans are released into maternal blood during normal pregnancy and in hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome. Maternal endothelia and the syncytiotrophoblast layer have been discussed as a possible origin of these glycocalyx components. Our study aimed to visualize the glycocalyx on the syncytiotrophoblast by electron microscopy, to analyze its structure and composition by immunohistochemistry, and to determine potential differences between healthy women and women with HELLP syndrome. For electron microscopy, a cotyledon was fixed by perfusion of the intervillous space with a 2% lanthanum–nitrate glutaraldehyde solution followed by immersion fixation in the same fixative. For immunohistochemistry, sections of 16 placentas (HELLP patients/healthy women, n = 8 each) were stained with monoclonal antibodies against the main glycocalyx constituents syndecan 1, hyaluronic acid, and heparan sulfate. Semiquantitative evaluation of staining intensity focused on the apical surface of the syncytiotrophoblast and fetal intravillous endothelia as possible localizations of a placental glycocalyx. Electron microscopy revealed a glycocalyx of approximately 250 nm, covering the syncytiotrophoblast layer. This was found to contain large amounts of syndecan 1, but neither hyaluronic acid nor heparan sulfate as major components. Intravillous fetal endothelium did not express any of the investigated glycosaminoglycans. Healthy women and patients with HELLP showed no differences concerning glycocalyx composition and thickness of the syncytiotrophoblast. The composition of the “placental” glycocalyx differs from the adult and fetal vascular glycocalyx. Obviously, the human placental syncytiotrophoblast maintains a special kind of glycocalyx at the fetomaternal interface.

Recent studies showed that considerable amounts of glycosaminoglycans are released into maternal blood during normal pregnancy and in hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome. Maternal endothelia and the syncytiotrophoblast layer have been discussed as a possible origin of these glycocalyx components. Our study aimed to visualize the glycocalyx on the syncytiotrophoblast by electron microscopy, to analyze its structure and composition by immunohistochemistry, and to determine potential differences between healthy women and women with HELLP syndrome. For electron microscopy, a cotyledon was fixed by perfusion of the intervillous space with a 2% lanthanum–nitrate glutaraldehyde solution followed by immersion fixation in the same fixative. For immunohistochemistry, sections of 16 placentas (HELLP patients/healthy women, n = 8 each) were stained with monoclonal antibodies against the main glycocalyx constituents syndecan 1, hyaluronic acid, and heparan sulfate. Semiquantitative evaluation of staining intensity focused on the apical surface of the syncytiotrophoblast and fetal intravillous endothelia as possible localizations of a placental glycocalyx. Electron microscopy revealed a glycocalyx of approximately 250 nm, covering the syncytiotrophoblast layer. This was found to contain large amounts of syndecan 1, but neither hyaluronic acid nor heparan sulfate as major components. Intravillous fetal endothelium did not express any of the investigated glycosaminoglycans. Healthy women and patients with HELLP showed no differences concerning glycocalyx composition and thickness of the syncytiotrophoblast. The composition of the “placental” glycocalyx differs from the adult and fetal vascular glycocalyx. Obviously, the human placental syncytiotrophoblast maintains a special kind of glycocalyx at the fetomaternal interface.

Severe inflammation has been shown to induce a shedding of the endothelial glycocalyx (EGX). Inflammatory cytokines, such as tumor necrosis factor α (TNF-α), impede the thickness of the EGX. While a controlled inflammatory reaction occurs already in normal pregnancy, women with hemolysis, elevated liver enzymes and low platelets (HELLP) syndrome had an exaggerated inflammatory response. This study investigates the shedding of the glycocalyx during normal pregnancy and in women with HELLP syndrome. Glycocalyx components (syndecan 1, heparan sulfate, and hyaluronic acid) were measured in serum of healthy women throughout pregnancy (4 time points, n = 26), in women with HELLP syndrome (n = 17) before delivery and in nonpregnant volunteers (n = 10). Serum concentrations of TNF-α and soluble TNF-α receptors (sTNF-Rs) were assessed once in all 3 groups. Syndecan 1 serum concentrations constantly rose throughout normal pregnancy. Immediately before delivery, a 159-fold increase was measured compared to nonpregnant controls (P < .01). Even higher amounts were observed in patients with HELLP prior to delivery (median 12 252 ng/mL) compared to healthy women matched by gestational age (median 5943 ng/mL; P < .01). Relevantly, increased serum levels of heparan sulfate, hyaluronic acid, and sTNF-Rs were only detected in patients with HELLP (P < .01). These findings suggest that considerable amounts of syndecan 1 are released into maternal blood during uncomplicated pregnancy. The HELLP syndrome is associated with an even more pronounced shedding of glycocalyx components. The maternal vasculature as well as the placenta has to be discussed as a possible origin of circulating glycocalyx components.

INTRODUCTION:Recent data suggested an interaction between plasma constituents and the endothelial glycocalyx to be relevant for vascular barrier function. This might be negatively influenced by infusion solutions, depending on ionic composition, pH and binding properties. The present study evaluated such an influence of current artificial preparations.METHODS:Isolated guinea pig hearts were prepared in a modified Langendorff mode and perfused with Krebs-Henseleit buffer augmented with 1g% human albumin. After equilibration the perfusion was switched to replacement of one half buffer by either isotonic saline (NaCl), ringer's acetate (Ri-Ac), 6% and 10% hydroxyethyl starch (6% and 10% HES, resp.), or 4% gelatine (Gel), the artificial colloids having been prepared in balanced solution. We analysed glycocalyx shedding, functional integrity of the vascular barrier and heart performance.RESULTS:While glycocalyx shedding was not observed, diluting albumin concentration towards 0.5g% by artificial solutions was associated with a marked functional breakdown of vascular barrier competence. This effect was biggest with isotonic saline and significantly attenuated with artificial colloids, the difference in the pressure dependent transvascular fluid filtration (basal vs. during infusion in groups NaCl, Ri-Ac, 6% HES, 10% HES and Gel, n = 6 each) being 0.31 ± 0.03 vs. 1.00 ± 0.04; 0.27 ± 0.03 vs. 0.81 ± 0.03; 0.29 ± 0.03 vs. 0.68 ± 0.02; 0.32 ± 0.03 vs. 0.59 ± 0.08 and 0.31 ± 0.04 vs. 0.61 ± 0.03 g/5min, respectively. Heart performance was directly related to pH value (7.38 ± 0.06, 7.33 ± 0.03, 7.14 ± 0.04, 7.08 ± 0.04, 7.25 ± 0.03), the change in the rate pressure product being 21,702 ± 1969 vs. 21,291 ± 2,552; 22,098 ± 2,115 vs. 14,114 ± 3,386; 20,897 ± 2,083 vs. 10,671 ± 1,948; 21,822 ± 2,470 vs. 10,047 ± 2,320 and 20,955 ± 2,296 vs. 15,951 ± 2,755 mmHg × bpm, respectively.CONCLUSIONS:It appears important to maintain the pH value within a physiological range to maintain optimal myocardial contractility. Using colloids prepared in calcium-containing, balanced solutions for volume replacement therapy may attenuate the breakdown of vascular barrier competence in the critically ill.

Atrial natriuretic peptide (ANP) is a peptide hormone released from the cardiac atria during hypervolemia. Though named for its well-known renal effect, ANP has been demonstrated to acutely increase vascular permeability in vivo. Experimentally, this phenomenon was associated with a marked shedding of the endothelial glycocalyx, at least for supraphysiological intravascular concentrations. This study investigates the impact and mechanism of action of physiological doses of ANP and related peptides on the vascular barrier. In isolated guinea pig hearts, prepared and perfused in a modified Langendorff mode with and without the intravascular presence of the colloid hydroxyethyl starch (HES), we measured functional changes in vascular permeability and glycocalyx shedding related to intracoronary infusion of physiological concentrations of A-, B- and C-type natriuretic peptide (ANP, BNP and CNP). Significant coronary venous washout of glycocalyx constituents (syndecan-1 and heparan sulfate) was observed. As tested for ANP, this effect was positively related to the intracoronary concentration. Intravascular shedding of the glycocalyx was morphologically confirmed by electron microscopy. Also, functional vascular barrier competence decreased, as indicated by significant increases in transudate formation and HES extravasation. Ortho-phenanthroline, a non-specific inhibitor of matrix metalloproteases, was able to reduce ANP-induced glycocalyx shedding. These findings suggest participation of natriuretic peptides in pathophysiological processes like heart failure, inflammation or sepsis. Inhibition of metalloproteases might serve as a basis for future therapeutical options.

Introduction: Vascular leakage after ischemia-reperfusion (IR) is largely attributed to the destruction of the endothelial barrier and its associated negatively charged glycocalyx. In vitro, sevoflurane attenuates these changes. Therefore, we compared sevoflurane with propofol with regard to the protection of the glycocalyx and the release of negatively charged substances in vivo. Methods: After surgical preparation under midazolam-fentanyl, nine pigs each received either propofol or sevoflurane. Ischemia of 90 min was induced by a balloon catheter in the thoracic aorta. After 120 min of reperfusion, the anesthetics were changed back to midazolam-fentanyl. Five animals, each without aortic occlusion, served as time controls. Blood electrolyte parameters were measured, from which the strong ion gap (SIG) was calculated. Serum heparan sulfate concentrations and immunohistology served as a marker of glycocalyx destruction. Results: Immediately after reperfusion, SIG increased significantly only in the propofol group (+6.7 mEq/l versus baseline; p < .05), remaining stable in sevoflurane and both time-controlled groups. Initially, heparan sulfate concentration increased comparably in both experimental groups, but after 120 min, it became stable in sevoflurane-anesthetized animals, while increasing further in the propofol group (p < .05). Conclusions: Unmeasured anions, predictive of negative outcome in previous studies, did not increase significantly in sevoflurane-anesthetized animals. Additionally, there was less heparan sulfate shedding over time, signaling less destruction of the glycocalyx. Therefore, in this in-vivo situation, sevoflurane proves to be superior to propofol in protecting the endothelium from IR injury.

Personalized tumor chemotherapy depends on reliable assay methods, either based on molecular “predictive biomarkers” or on a direct, functional ex vivo assessment of cellular chemosensitivity. As a member of the latter category, a novel high-content platform is described monitoring human mamma carcinoma explants in real time and label-free before, during and after an ex vivo modeled chemotherapy. Tissue explants are sliced with a vibratome and laid into the microreaction chambers of a 24-well sensor test plate. Within these ≈23 μl volume chambers, sensors for pH and dissolved oxygen record rates of cellular oxygen uptake and extracellular acidification. Robot-controlled fluid system and incubation are parts of the tissue culture maintenance system while an integrated microscope is used for process surveillance. Sliced surgical explants from breast cancerous tissue generate well-detectable ex vivo metabolic activity. Metabolic rates, in particular oxygen consumption rates have a tendency to decrease over time. Nonetheless, the impact of added drugs (doxorubicin, chloroacetaldehyde) is discriminable. Sensor-based platforms should be evaluated in explorative clinical studies for their suitability to support targeted systemic cancer therapy. Throughput is sufficient for testing various drugs in a range of concentrations while the information content obtained from multiparametric real-time analysis is superior to conventional endpoint assays.