Endothelial damage during early endotoxemia has been shown to be leukocyte independent. Platelet-activating factor and serotonin receptor antagonism has been shown to reduce leukocyte-independent macromolecular leakage significantly. Nevertheless, the exact mechanisms involved in leukocyte-independent endothelial dysfunction are unknown. Therefore, it was the aim of the study to investigate the effects of nitric oxide (NO) on leukocyte-independent endothelial damage during endotoxemia. In male Wistar rats, venular wall shear rate, macromolecular efflux, and leukocyte-endothelial interaction were determined in mesenteric postcapillary venules using intravital microscopy at baseline and at 60 and 120 min after start of the experiment. The animals received fucoidin to prevent leukocyte-endothelial interaction. The experiments were divided into three parts. In part 1, we investigated the effects of the NO-inhibitor L-NAME on leukocyte-independent endothelial damage during endotoxemic and nonendotoxemic conditions. The efficiency of the NO-donor (SIN-1) used, part 2, was investigated by the inhibitory properties of SIN-1 on NO-inhibition-induced macromolecular efflux. Finally, part 3, we analyzed the effects of the NO-donor SIN-1 on endothelial damage during endotoxemia. Both the combined challenge of the animals with L-NAME and endotoxin and the challenge with L-NAME alone resulted in a strong increase in macromolecular efflux, showing significant differences to control groups at an earlier time point than endotoxin challenge alone. Interestingly, combined L-NAME and endotoxin challenge, L-NAME challenge alone, and endotoxin challenge alone showed a similar macromolecular efflux at the end of the experiment. SIN-1 prevented both the increase in macromolecular efflux seen after L-NAME challenge (part 2) and was highly effective in preventing significantly the increase in macromolecular leakage that is seen during leukocyte-independent endotoxemia (part 3). In conclusion, our data indicate that during early states of endotoxemia endogenous NO preserves endothelial integrity in a leukocyte-independent setting. Exogenous NO prevents endothelial damage during early leukocyte-independent endotoxemia. Summarizing these data, endothelial integrity during leukocyte-independent endotoxemia is a NO-mediated event.

A new adjunctive system to obtain higher PaO 2 with nasal cannula or catheter: double trunk mask

ObjectiveTo test the effects of dobutamine and dopexamine on hepatic portal and sinusoidal blood flow in a model of normodynamic endotoxemia. DesignRandomized, controlled trial. SettingExperimental laboratory. SubjectsMale Wistar rats (250–350 g). InterventionsA total of 40 male Wistar rats were randomized into four groups: a control group, which only received Ringer’s solution; an endotoxin group, which received a continuous infusion of 2 mg/kg body weight (bw)/hr of endotoxin; a dobutamine group, which received endotoxin and a continuous infusion of dobutamine (3 &mgr;g/kg bw/min); and a dopexamine group, which received endotoxin and dopexamine (2 &mgr;g/kg bw/min). The experimental period was 120 min. Measurements and Main Results Mean arterial blood pressure (MAP), heart rate (HR), and cardiac output (CO) were detected. Portal blood flow was measured using an ultrasonic flow probe positioned around the portal vein, and sinusoidal blood flow was detected in the left liver lobe using intravital microscopy. All detected variables remained stable in the control group. In the endotoxin group, HR increased significantly and MAP decreased significantly from 111 ± 10 mm Hg to 95 ± 8 mm Hg at 120 mins, whereas CO remained unchanged. Both in the dobutamine and the dopexamine group HR increased and MAP decreased more than in the endotoxin group. CO increased in both groups significantly. Portal blood flow (23 ± 4 mL/min to 16 ± 3 mL/min) and sinusoidal blood flow (38.6 ± 2.5 to 22.8 ± 1.2 103 &mgr;m3/sec) decreased significantly in the endotoxin group. In the dobutamine and the dopexamine group portal and sinusoidal blood flow remained at baseline values. ConclusionsIn our model of endotoxemia, dobutamine and dopexamine preserved systemic and hepatic blood flow. These preservations of hepatic blood flow during endotoxemia could portend beneficial effects but need to be studied further.

PURPOSE:The purpose of this study was to investigate the role of histamine in mediating leukocyte-independent microvascular permeability and mast cell activation during endotoxemia. Microvascular permeability and mast cell activity were determined after inhibition of the L-selectin mediated leukocyte-adherence by fucoidin and after inhibition of histamine effects by the histamine H1-receptor antagonist diphenhydramine.MATERIALS AND METHODS:In male Wistar rats, leukocyte rolling, leukocyte adherence, microvascular permeability, and mast cell activity were determined in mesenteric postcapillary venules using intravital microscopy. After pretreatment with the histamine H1-receptor antagonist diphenhydramine, animals in the ETX/H1-ANT group received a continuous infusion of endotoxin. Animals in the ETX group underwent the same procedure, but received saline 0.9% instead of diphenhydramine. In both groups, leukocyte adherence was prevented by administration of fucoidin. Animals in the control group received volume-equivalent saline 0.9%.RESULTS:In the endotoxin-challenged groups, fucoidin prevented leukocyte rolling and reduced leukocyte adherence to values comparable to control group. In the ETX group and the ETX/H1-ANT group both microvascular permeability and mast cell activity increased significantly, starting at 60 minutes. Differences in mast cell activity between the ETX group and the ETX/H1-ANT group were significant at 60 minutes and at 120 minutes. Differences in microvascular permeability between the ETX/H1-ANT group and the ETX group were not significant.CONCLUSIONS:The leukocyte-independent microvascular damage during early endotoxemia cannot be inhibited efficiently by the H1-receptor antagonist diphenhydramine, indicating that histamine seems to play only a minor role in that pathophysiology. Furthermore, mast cells do not seem to be involved in the development of leukocyte-independent plasma extravasation during endotoxemia.

BACKGROUND:The objective of this study was to determine the effects of a continuous infusion of the phosphodiesterase inhibitor enoximone on mucosal villus blood flow in a normotensive model of endotoxemia.METHODS:Twenty-four anesthetized and ventilated rats underwent laparotomy and a ileal portion was exteriorized and opened by an antimesenteric incision. The ileal segment was fixed on a plexiglass stage with the mucosal surface upward. Microcirculatory parameters were assessed by intravital videomicroscopy. The animals were randomly assigned to receive one of three treatments: infusion of Escherichia coli lipopolysaccharides (LPS, 2 mg/kg/h) without phosphodiesterase inhibitor pretreatment (LPS group); or infusion of LPS with enoximone pretreatment (10 microg x kg(-1) x min(-1), start 30 min before LPS infusion, enoximone group), or infusion of an eqivalent volume of NaCl 0.9% (control group). Macrohemodynamic parameters (MAP, HR) and microhemodynamic parameters of ileal mucosa (mean diameter of central arterioles = DA, and mean erythrocyte velocity within the arterioles = VE) were measured 30 min before and at 0, 60, and 120 min after induction of endotoxemia. Mucosal villus blood flow was calculated from DA and VE.RESULTS:In this normotensive endotoxemia model MAP remained stable in the control and the LPS group but significantly decreased in the enoximone group. The endotoxin-induced decrease of VE and DE of central arterioles of mucosal villi could be prevented. Thus, mucosal villus blood flow did not decrease compared to the LPS group.CONCLUSIONS:Our results indicate that enoximone during an early stage of sepsis contributes to systemic hypotension but prevents mucosal hypoperfusion.

Purpose: To determine whether the compromised intestinal villus blood flow in a rat model of endotoxemia could be improved by continuous infusion of the phosphodiesterase (PDE) inhibitor milrinone.

This study was conducted to quantify the effect of systemic Catalase, a hydrogen peroxide scavenger, on villous microcirculation in the inflamed small intestine of the rat. Intestinal inflammation was induced with s.c. application of Indomethacin. Intravital fluorescence microscopy and FITC-labeled erythrocytes were used to quantify erythrocyte velocity and arteriolar diameter in the main arteriole of the villi in the terminal ileum following i.v. application of Catalase in the inflamed intestine, and the blood flow was calculated. Control groups were formed for Ringer's lactate, Catalase and Indomethacin, respectively. We found that villous blood flow was significantly increased in the in the inflamed intestine. Application of Catalase led to a significant decrease in villous perfusion, but had no effect in the control group. The increase in villous blood flow was accompanied by changes in the diameter of the main arteriole. This effect on arteriolar diameter was reversed by i.v. Catalase. Our results provide evidence that systemic application of Indomethacin leads to vasodilatation of the main arteriole of the villus in the rat ileum and hyperemia in the mucosa. Hyperemia and the vascular diameter of the main arteriole were significantly reduced by H2O2-scavenger Catalase, suggesting that endogenous H2O2 may be one of the mediators of hyperemia in the mucosa in this animal model of intestinal inflammation.

Purpose: The objective of this study was to determine the effects of a continuous infusion of the phosphodiesterase (PDE) inhibitor amrinone on mucosal villus blood flow in a normotensive model of endotoxemia. Materials and Methods: Twenty-four anesthetized and ventilated rats underwent laparotomy, and an ileal portion was exteriorized and opened by an antimesenteric incision. The ileal segment was fixed on a plexiglass stage with the mucosal surface upward. Microcirculatory parameters were assessed by intravital videomicroscopy. The animals were randomly assigned to receive one of three treatments: infusion of Escherichia coli lipopolysaccharides (LPS, 2 mg/kg/h) without phosphodiesterase inhibitor pretreatment (LPS group); or infusion of LPS with amrinone pretreatment (40 μg/kg/min, start 30 minutes before LPS infusion) (amrinone group), or infusion of eqivalent volumes of NaCl 0.9% (control group). Macrohemodynamic parameters (MAP, HR) and microhemodynamic parameters of ileal mucosa (mean diameter of central arterioles = DA and mean erythrocyte velocity within the arterioles = VE) were measured 30 minutes before and at 0, 60, and 120 minutes after induction of endotoxemia. Mucosal villus blood flow was calculated from DA and VE.Results: In this normotensive endotoxemia model, MAP remained stable in the control and the LPS group but significantly decreased in the amrinone group. The endotoxin-induced decrease of VE and DA of central arterioles of mucosal villi could be attenuated and prevented, respectively. Thus, the endotoxin-induced decrease of mucosal villus blood flow was diminished but not fully restored by amrinone infusion. Conclusion: Our results indicate that amrinone during an early stage of sepsis is of limited value. It attenuates mucosal hypoperfusion but contributes to systemic hypotension. Copyright © 2000 by W.B. Saunders Company

Purpose: The objective of this study was to determine the effects of epinephrine and norepinephrine on mucosal villous blood flow in a normotensive model of endotoxemia.Materials and Methods: Thirty-two anesthetized rats were laparotomized, and a jejunal portion was exteriorized and opened by an antimesenteric incision. The jejunal segment was fixed on a plexiglass stage with the mucosal surface upward. Microcirculatory parameters were assessed by intravital videomicroscopy. The animals were randomly assigned to receive one of four treatments: infusion of Escherichia coli lipopolysaccharides (LPS, 2 mg/kg/h) without catecholamine pretreatment (LPS group); or infusion of LPS with epinephrine pretreatment (0.2 mu g/kg/min, start 30 minutes before LPS infusion) (E group), or infusion of LPS with norepinephrine pretreatment (0.2 mu g/kg/min, start 30 minutes before LPS infusion) (IUE group). The control group did not receive either catecholamines or LPS, Mean diameter of central arterioles (D-A) and mean erythrocyte velocity within the arterioles (V-E) were measured 30 minutes before and at 0, 60, and 120 minutes after induction of endotoxemia, Mucosal villous blood flow was calculated from D-A and V-E Results: LPS infusion alone and norepinephrine plus LPS infusion led to a significant vasoconstriction of central arterioles, which was associated with a similar decrease in mucosal villous blood flow. Epinephrine infusion alone led to a vasodilation and an increase in villous blood flow within the first 30 minutes. After induction of endotoxemia, D-A returned to baseline values and villous blood flow was as low as in the LPS and the norepinephrine group after 120 minutes.Conclusion: In this experimental rat model, the catecholamines epinephrine and norepinephrine in a dosage of 0.2 mu g.kg(-1).min(-1) neither diminish nor improve mucosal villous blood flow during the early phase of endotoxemia. Copyright (C) 1999 by W.B, Saunders Company.

A decrease in liver blood flow leads to dysfunction of hepatocytes and Kupffer cells, with subsequent local and systemic liberation of proinflammatory mediators that may maintain systemic inflammatory response syndrome (SIRS) and may lead to multiple organ dysfunction syndrome (MODS). There is only limited knowledge on the hepatic micro- and macrocirculation during sepsis or endotoxemia. Therefore, the aim of our study was to investigate alterations in hepatic portal blood flow (PBF) and sinusoidal blood flow (SBF) during endotoxemia. In male Wistar rats endotoxemia was induced by continuous infusion of 2 mg/kg/h lipopolysaccharides from Escherichia coli 026:B6 immediately after baseline measurements (n = 8). The control group (n = 8) received an equivalent volume of Ringer's solution. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), PBF, and SBF were measured at baseline and 60 and 120 min after induction of endotoxemia. PBF was measured using an ultrasonic flow probe that was positioned around the portal vein. SBF was detected by in vivo videomicroscopy of the left liver lobe. In the LPS group MAP decreased, but CO remained at baseline values. During endotoxemia PBF decreased significantly from 23 ± 3 to 15 ± 4 mL/min (60 min) and 16 ± 3 mL/min (120 min). SBF also significantly decreased to 68.5% (60 min) and 57.1% (120 min) of baseline value. Our results demonstrate that during early endotoxemia hepatic macro- and microcirculatory perfusion is significantly decreased despite unchanged CO. This early reduction of hepatic perfusion might be caused by an increased hepatic vessel resistance as a consequence of liberation of vasoconstrictive mediators or/and by a decrease in intestinal perfusion.

Changes of blood flow in the intestine occur under various pathological conditions. The mucosa of the intestine is especially sensitive to tissue damage resulting in swelling, loss of tissue integrity, and ulceration. Changes of blood supply to the mucosa may contribute to local tissue damage. Therefore, the quantification of the perfusion of the intestinal mucosa in an animal model may help to elucidate the involved pathophysiological mechanisms. In our study, autologous erythrocytes were labeled with fluorescein-isothiocyanate and used for the evaluation of erythrocyte velocity in the main arteriole of the villi in the distal part of the ileum using intravital microscopy. In addition, the arteriolar diameter was determined, and the arteriolar blood flow was calculated. Under stable cardiovascular and respiratory conditions, blood flow ranged between 6.6 +/- 0.3 and 5.9 +/- 0.3 nl/min (means +/- SEM) during the observation period of 120 min. Our results suggest that this approach is a feasible method to quantify blood flow in the main arteriole of the villi and is therefore a suitable method for further investigating changes of mucosal blood flow in acute and chronic states of bowel disease.

optimize the screening efficiency and to detect those patients with milder histopathological abnormalities compatible with CD.The small bowel biopsy remains mandatory to diagnose celiac disease.

Purpose: The gut plays a pivotal role in sepsis. Intestinal hypoperfusion with subsequent ischemia leads to translocation of endotoxin, Dobutamine has been demonstrated to increase mesenteric blood flow during endotoxic shock; however, its effects on mucosal blood flow especially in intestinal villi is not known. Therefore, we investigated its influence on the blood flow and the arteriolar diameters in intestinal villi in a model of normotensive endotoxemia.Materials and Methods: Twenty-one male Wistar rats were divided into three groups: (1) control, saline; (2) endotoxin, endotoxin 1.5 mg/kg during 60 minutes; and (3) dobutamine, endotoxin 1.5 mg/kg (60 minutes) and dobutamine 2.5 mu g/kg/min during 120 minutes. Villus blood flow and arteriolar diameters were determined at 0 minutes, 60 minutes, and 120 minutes in each group using intravital microscopy.Results: Villus blood flow was constant in the control group, significantly reduced at 120 minutes in the endotoxin group (120 minutes, 55.1 +/- 7.4%), and remained at baseline values in the dobutamine group. The arteriolar diameters remained constant in the control and the dobutamine groups, but they were significantly reduced in the endotoxin group at 120 minutes (7.8 +/- 0.2 to 6.5 +/- 0.7 mu m)Conclusion: Our results indicate that in rats with normotensive endotoxemia, arteriolar diameters and blood flow in intestinal villi were reduced. Dobutamine prevented arteriolar constriction and maintained villus blood flow at preendotoxemic values. Copyright (C) 1997 by W.B. Saunders Company.

Die Bestimmung des Blutflusses in der Darmschleimhaut ist von Bedeutung, da bei Sepsis, Ischämie/Reperfusion, im Rahmen von entzündlichen Darmerkrankungen und durch die Einnahme von Medikamenten wie zum Beispiel nichtsteroidaler Antiphlogistika Störungen der Schleimhautintegrität des Magen-Darm-Traktes auftreten. Welchen ursächlichen Beitrag Veränderungen der Schleimhautdurchblutung an einer Schädigungen der Mukosabarriere haben, ist unzureichend definiert. Zur Untersuchung der Schleimhautdurchblutung des Dünndarmes etablierten wir ein Modell zur Quantifizierung der Erythrozytengeschwindigkeit und des Durchmessers in der Arteriole der Schleimhautzotten des Dünndarms der Ratte.

Hypoperfusion of the gut mucosa is thought to be a factor in the development of gut barrier failure during sepsis and septic shock. Dopamine stimulates DA-1 receptors which mediate regional vasodilatation in the gut. Therefore, we have investigated the effect of low-dose dopamine (3 micrograms kg-1 min-1) on the intestinal villus microcirculation during endotoxaemia in a rat model of normotensive endotoxaemia, using in vivo videomicroscopy. Blood flow in and the diameters of central villus arterioles were measured before, immediately after and 60 min after a 1-h continuous infusion of endotoxin 1.5 mg/kg body weight. After baseline measurements were obtained, rats received either an infusion of 0.9% saline (group A; n = 7) or a volume-equivalent infusion of dopamine 3 micrograms kg-1 min-1 (group B; n = 7) throughout the study. Control animals (group C; n = 7) received no endotoxin or dopamine. In group A, villus blood flow (mean baseline 8.4 (SEM 0.9) nl min-1) decreased by 29.7 (8.9)% to 5.9 (0.9) nl min-1 immediately after endotoxin challenge and by a total of 43.1 (7.3)% to 4.7 (0.7) nl min-1 after another 60 min. Simultaneously, villus arteriolar diameters decreased from 7.8 (0.2) to 6.9 (0.3) microns and to 6.5 (0.3) microns, respectively. In group B, villus blood flow (baseline 8.7 (0.4) nl min-1) was unchanged immediately after the 1-h infusion of endotoxin (8.3 (0.4) nl min-1). However, another 60 min later blood flow decreased by 28.8 (8.0)% to 6.1 (0.7) nl min-1. In contrast with group A, the diameters of the central villus arterioles were unchanged despite administration of endotoxin (7.9 (0.2) microns; 8.1 (0.4) microns; 8.2 (0.5) microns). In group C, there were no changes in villus blood flow or arteriolar diameters throughout the study. Our results indicated that low-dose dopamine did not prevent, but delayed and attenuated, the decrease in intestinal villus blood during normotensive endotoxaemia.

OBJECTIVE:To determine the influence of dopexamine, a synthetic catecholamine ligand for dopaminergic and beta 2-adrenergic receptors, on alterations of the intestinal villus microcirculation in a model of normotensive endotoxemia.DESIGN:Randomized, controlled trial.SETTING:Experimental laboratory.SUBJECTS:Twenty-one male Wistar rats.INTERVENTIONS:Rats were treated with a continuous infusion of dopexamine (2.5 micrograms/kg/min; N = 7; group A) or 0.9% saline (n = 7; group B) during a study period of 120 mins. Both groups were given endotoxin (Escherichia coli lipopolysaccharide; 1.5 mg/kg Iv) over 60 mins. Animals in the control group (n = 7; group C) received a volume-equivalent infusion of 0.9% saline. Total volume substitution in all groups was 15 mL/kg/hr.MEASUREMENTS AND MAIN RESULTS:Blood flow in the intestinal villi of the distal ileum was determined using in vivo videomicroscopy at baseline, and 60 and 120 mins after the endotoxin challenge. These blood flow determinations were done by an observer who was unaware of the previous treatment of the animals. In addition, mean arterial pressure was monitored at baseline, and 15, 30, 45, 60, 75, 90, 105, and 120 mins later. The administration of 1.5 mg/kg endotoxin alone (group B) resulted in a reduction of the intestinal villus blood flow to 74.8 +/- 9.5% of baseline after 60 mins, and to 61.1 +/- 8.5% of baseline after 120 mins (baseline: 7.4 +/- 0.6 nL/min; 60 mins: 5.3 +/- 0.8 nL/min; 120 mins: 4.4 +/- 0.5 nL/min; p < .05). This reduction of blood flow was associated with a decrease in the arteriolar diameters by 13.8 +/- 2.5% after 60 mins, and by 17.1 +/- 4.3% after 120 mins (p < .05 vs. baseline). In contrast, villus blood flow in the dopexamine group (group A) did not show statistically significant changes during the entire study period, despite the administration of endotoxin (baseline: 8.2 +/- 0.6 nL/min; 60 mins: 7.3 +/- 0.8 nL/min; 120 mins: 7.8 +/- 0.5 nL/min). No vasoconstriction of the villus arterioles was noted in this group. In control animals (group C), the blood flow (baseline: 8.1 +/- 1.6 nL/min; 60 mins: 7.6 +/- 1.4 nL/min: 120 mins: 7.8 +/- 1.4 nL/min) and the arteriolar diameters remained unchanged throughout the observation period. Mean arterial pressure did not differ between groups: it remained unaltered in all groups during the entire study period.CONCLUSIONS:Dopexamine maintains intestinal villus arterial perfusion and prevents the vasoconstriction in villus arterioles during early normotensive endotoxemia. Therefore, further studies in critically ill patients will have to determine whether the early prophylactic use of dopexamine can limit ischemia and prevent the development of multiple organ failure.

Intestinal mucosal hypoperfusion with subsequent ischemia during endotoxemia might cause a breakdown of the gut barrier with translocation of bacteria and their toxins into the systemic circulation, thus maintaining a "gut-derived" septic state. The aim of this study was to investigate the influence of endotoxin on the microcirculation of intestinal villi, which represent the most vulnerable part of the mucosa. The changes in blood flow and in the diameters of the central villus arterioles located in the distal ileum were monitored in control rats without lipopolysaccharide (LPS) exposure (n=7), and in rats receiving 1.5 mg/kg b.w. LPS (n=7) or 15 mg/kg b.w. LPS (n=7) over 60 min. The blood flow and the arteriolar diameters were determined using in vivo videomicroscopy at baseline, and 60 min and 120 min later. In control animals, no change in blood flow and arteriolar diameters were observed during the entire experiment. Administration of 1.5 mg/kg b.w. LPS reduced the blood flow to 69.5 +/- 9.0% of the baseline value at the end of the study period. This decrease in blood flow was associated with a decrease in the villus arteriolar diameters by 17.4 +/- 2.5% from the baseline values. In animals exposed to 15 mg/kg b.w. LPS, the decrease in villus blood flow at 60 min was 64.8 +/- 10.9% of baseline, and at 120 min 66.9 +/- 12.6% of baseline. The diameters of the villus arterioles were reduced by 11.5 +/- 2.4% and 15.1 +/- 1.7%, respectively. In the control group and in the 1.5-mg/kg LPS group, the mean arterial blood pressure did not change during the entire study period. In the 15-mg/kg LPS group, the mean arterial pressure tended to decrease after 60 min. These data suggest a reduction of villus blood flow due to vasoconstriction in the central villus arterioles during normotensive endotoxmia, which might represent the mechanism for the mucosal ischemia observed in critically ill patients.