Microvascular responses to sepsis: clinical significance

Sedation with propofol and isoflurane differs in terms of microcirculatory parameters: A randomized animal study using dorsal skinfold chamber mouse model

OBJECTIVE

This study aimed to explore the effects of sedative doses of propofol and isoflurane on microcirculation in septic mice compared to controls. Isoflurane, known for its potential as a sedation drug in bedside applications, lacks clarity regarding its impact on the microcirculation system. The hypothesis was that propofol would exert a more pronounced influence on the microvascular flow index, particularly amplified in septic conditions.

MATERIAL AND METHODS

Randomized study was conducted from December 2020 to October 2021 involved 60 BALB/c mice, with 52 mice analyzed. Dorsal skinfold chambers were implanted, followed by intraperitoneal injections of either sterile 0.9 % saline or lipopolysaccharide for the control and sepsis groups, respectively. Both groups received propofol or isoflurane treatment for 120 min. Microcirculatory parameters were obtained via incident dark-field microscopy videos, along with the mean blood pressure and heart rate at three time points: before sedation (T0), 30 min after sedation (T30), and 120 min after sedation (T120). Endothelial glycocalyx thickness and syndecan-1 concentration were also analyzed.

RESULTS

In healthy controls, both anesthetics reduced blood pressure. However, propofol maintained microvascular flow, differing significantly from isoflurane at T120 (propofol, 2.8 ± 0.3 vs. isoflurane, 1.6 ± 0.9; P < 0.001). In the sepsis group, a similar pattern occurred at T120 without statistical significance (propofol, 1.8 ± 1.1 vs. isoflurane, 1.2 ± 0.7; P = 0.023). Syndecan-1 levels did not differ between agents, but glycocalyx thickness index was significantly lower in the isoflurane-sepsis group than propofol (P = 0.001).

CONCLUSIONS

Propofol potentially offers protective action against microvascular flow deterioration compared to isoflurane, observed in control mice. Furthermore, a lower degree of sepsis-induced glycocalyx degradation was evident with propofol compared to isoflurane.

Effects of endotoxin adsorber hemoperfusion on sublingual microcirculation in patients with septic shock: a randomized controlled trial

Background

Endotoxins can induce an excessive inflammatory response and result in microcirculatory dysfunction. Polymyxin-B hemoperfusion (PMX-HP) has been recognized to effectively remove endotoxins in patients with sepsis and septic shock, and a rat sepsis model revealed that PMX-HP treatment can maintain a better microcirculation. The primary aim of this study was to investigate the effect of PMX-HP on microcirculation in patients with septic shock.

Methods

Patients with septic shock were enrolled and randomized to control and PMX-HP groups. In the PMX-HP group, patients received the first session of PMX-HP in addition to conventional septic shock management within 24 h after the onset of septic shock; the second session of PMX-HP was provided after another 24 h as needed.

Results

Overall, 28 patients finished the trial and were analyzed. The mean arterial pressure and norepinephrine infusion dose did not differ significantly between the control and PMX-HP groups after PMX-HP treatment. At 48 h after enrollment, total vessel density (TVD) and perfused vessel density (PVD) were higher in the PMX-HP group than in the control group [TVD 24.2 (22.1–24.9) vs. 21.1 (19.9–22.9) mm/mm²; p = 0.007; PVD 22.9 (20.9–24.9) vs. 20.0 (18.9–21.6) mm/mm², p = 0.008].

Conclusions

This preliminary study observed that PMX-HP treatment improved microcirculation but not clinical outcomes in patients with septic shock at a low risk of mortality. Nevertheless, larger multicenter trials are needed to confirm the effect of PMX-HP treatment on microcirculation in patients with septic shock at intermediate- and high-risk of mortality.

Trial registration ClinicalTrials.gov protocol registration ID: NCT01756755. Date of registration: December 27, 2012. First enrollment: October 6, 2013. https://clinicaltrials.gov/ct2/show/NCT01756755

Inflammasomes: Pandora's box for sepsis

Sepsis was known to ancient Greeks since the time of great physician Hippocrates (460-377 BC) without exact information regarding its pathogenesis. With time and medical advances, it is now considered as a condition associated with organ dysfunction occurring in the presence of systemic infection as a result of dysregulation of the immune response. Still with this advancement, we are struggling for the development of target-based therapeutic approach for the management of sepsis. The advancement in understanding the immune system and its working has led to novel discoveries in the last 50 years, including different pattern recognition receptors. Inflammasomes are also part of these novel discoveries in the field of immunology which are <20 years old in terms of their first identification. They serve as important cytosolic pattern recognition receptors required for recognizing cytosolic pathogens, and their pathogen-associated molecular patterns play an important role in the pathogenesis of sepsis. The activation of both canonical and non-canonical inflammasome signaling pathways is involved in mounting a proinflammatory immune response via regulating the generation of IL-1β, IL-18, IL-33 cytokines and pyroptosis. In addition to pathogens and their pathogen-associated molecular patterns, death/damage-associated molecular patterns and other proinflammatory molecules involved in the pathogenesis of sepsis affect inflammasomes and vice versa. Thus, the present review is mainly focused on the inflammasomes, their role in the regulation of immune response associated with sepsis, and their targeting as a novel therapeutic approach.

Misdirected Sympathy: The Role of Sympatholysis in Sepsis and Septic Shock

The spectrum of sepsis and septic shock remains a highly prevalent disease state, carrying a high risk of morbidity and mortality. The sympathetic nervous system (SNS) plays an important role in this initial cascade, enabling the host to respond to invading pathogens; however, prolonged activation can become pathological. The potential for unregulated sympathetic tone to become of detriment in patients with sepsis has fueled interest in the role and impact of sympatholysis, the selective inhibition of sympathetic tone. The cornerstone of septic shock therapy for decades has been the supplementation of catecholamines and thus potential further perpetuation of this sympathetic dysregulation. Although the theory of sympatholysis circulates around cardiovascular effects and stroke volume optimization, the impact of augmenting the SNS may extend well beyond this, including the impacts on the immune system, inflammatory cascade, and even gene transcription. Presently, the most robust clinical evidence involves the use of the cardioselective β-blocker esmolol in patients with septic shock with persistent tachycardia secondary to catecholamine use. Evidence is isolated only to animal models with α-agonists. Future evidence stands to elucidate the balance of sympathetic and autonomic tone as well as the potential role of redirecting and maximizing sympathetic activity.

Disseminated intravascular coagulation in a novel porcine model of severe Staphylococcus aureus sepsis fulfills human clinical criteria

Sepsis is a common and often fatal complication in human patients in intensive care units. Relevant and well characterized animal models of sepsis may provide valuable information on pathophysiological mechanisms and be a mean of testing new therapeutic strategies. Large animal models of Staphylococcus aureus sepsis are rare, even though S. aureus increasingly affects human patients. Sepsis changes the haemostatic balance and leads to endothelial cell (EC) activation, coagulopathy and, in severe cases, disseminated intravascular coagulation (DIC). The aim of this study was to characterize the haemostatic and vascular alterations in a novel porcine model of severe S. aureus sepsis, investigating whether the changes fulfill the human clinical criteria for DIC. Five pigs were inoculated intravenously with S. aureus and two control animals were sham-inoculated. Blood samples were collected for thromboelastography (TEG) and assessment of plasma-based haemostatic parameters. Tissue was collected for histopathology and reverse transcriptase quantitative real-time polymerase chain reaction for measurement of mRNA encoding EC markers. All infected animals developed DIC; including procoagulant activation represented by hypercoagulable TEG profiles and prolonged clotting time. Histologically, numerous pulmonary thrombi were present in one pig. Inhibitor consumption was represented by decreasing antithrombin levels in infected pigs. Hyaline globules were found in three infected pigs, confirming fibrinolytic activation. EC activation was identified by expression of von Willebrand factor in small vessels together with elevated mRNA encoding activated EC markers. Severe haemostatic and vascular changes fulfilling the human criteria for DIC were therefore seen in all infected pigs. A tendency towards uncompensated DIC was seen in two animals.

Serum heparan sulfate levels are elevated in endotoxemia

BACKGROUND

Increased vascular permeability is a characteristic feature of sepsis which, in the past, has been ascribed exclusively to a malfunction of endothelial cells. However, recently it has become evident that the endothelial glycocalyx is of considerable importance concerning various aspects of vascular physiology, e.g. the vascular barrier and inflammation. Heparan sulfate, one of its essential components is characteristically traceable in blood, in case the endothelial glycocalyx is damaged or destroyed.

METHODS

In 15 pigs we investigated whether the administration of endotoxin from gram-negative bacteria (Escherichia coli) results in increased serum levels of heparan sulfate, signalizing a shedding of the glycocalyx. In addition, markers of inflammation (white blood cell count, platelet count, tumour necrosis factor-α and interleukin-6) were evaluated over an observation period of 6 hours.

RESULTS

Serum heparan sulfate concentrations significantly increased over time in the endotoxin group and were significantly elevated in comparison to the control group 6 hours after administration of endotoxin (p<0.001). In the endotoxin group all markers of inflammation significantly changed during the time course.

CONCLUSIONS

The administration of bacterial endotoxin induced a significant rise in degradation products of the endothelial glycocalyx.

Effects of eritoran tetrasodium, a toll-like receptor 4 antagonist, on intestinal microcirculation in endotoxemic rats

Lipopolysaccharide (LPS) or endotoxin can induce Toll-like receptor 4 signaling and cause microcirculatory dysfunction, which can lead to multiple organ dysfunction. The goal of this study was to investigate whether Toll-like receptor 4 antagonist, eritoran tetrasodium, can attenuate microcirculatory dysfunction in endotoxemic rats. Seventy-two male Wistar rats were divided into three groups as follows: control, LPS, and eritoran + LPS. These rats received laparotomy to exteriorize a segment of terminal ileum for microcirculation examination on intestinal mucosa, muscle, and Peyer patch. The rats in the eritoran + LPS group received 10 mg kg⁻¹ eritoran intravenously. The rats in the LPS and eritoran + LPS groups received 15 mg kg⁻¹ LPS intravenously. Microcirculatory blood flow intensity was measured by full-field laser perfusion imager. Total and perfused small-vessel densities, microvascular flow index, and heterogeneity index were investigated by sidestream dark-field video microscope. Our results revealed that eritoran restored the mean arterial pressure. At 240 min, the microcirculatory blood flow intensity was higher in the eritoran + LPS group than in the LPS group as follows: mucosa (1,094 [SD, 398] vs. 543 [SD, 163] perfusion unit [PU]; P < 0.001), muscle (752 [SD, 124] vs. 357 [SD, 208] PU; P < 0.001), and Peyer patch (961 [SD, 162] vs. 480 [SD, 201] PU; P < 0.001). Eritoran also attenuated endotoxin-induced elevation in the serum level of D-dimer. In conclusion, we have established a promising rat protocol to investigate the intestinal microcirculation in endotoxemia. Our data indicate that eritoran can reduce microcirculatory dysfunction in endotoxemic rats.

Effects of Crude Rhubarb on Intestinal Permeability in Septic Patients

The therapeutic effect of crude rhubarb on intestinal permeability was investigated in septic patients. Forty septic patients were enrolled in this study and randomly divided into two groups: the crude rhubarb treatment group ( n = 18) and the control group ( n = 22). The same treatments were given to both groups except that the crude rhubarb treatment group was administrated with crude rhubarb powders (3 g, tid, p.o). The levels of procalcitonin, D-lactate in plasma and lactulose/mannitol (L/M) ratio in the urine were determined on the first day and the sixth day after treatment with or without crude rhubarb. There were no significant differences in procalcitonin, L/M ratio and D-lactate on the first day between the crude rhubarb treatment group and the control group ( p > 0.05). However, the ratio of L/M on the sixth day for the control group was 0.167 ± 0.036, while that of the crude rhubarb treatment group was 0.062 ± 0.013 ( p < 0.05). Moreover, the levels of procalcitonin and D-lactate in the crude rhubarb treatment group were obviously lower than those in the control group on the sixth day (procalcitonin: 4.11 ± 1.40 μg/L vs. 2.21 ± 0.61 μg/L ; D-lactate: 0.24 ± 0.06 ng/L vs. 0.09 ± 0.03 ng/L , p < 0.05, both). These data confirmed that crude rhubarb's effects on septic patients of ameliorating intestinal permeability.

Protein kinase C δ (PKCδ)-extracellular signal-regulated kinase 1/2 (ERK1/2) signaling cascade regulates glycogen synthase kinase-3 (GSK-3) inhibition-mediated interleukin-10 (IL-10) expression in lipopolysaccharide (LPS)-induced endotoxemia

Glycogen synthase kinase-3 (GSK-3) modulates a wide array of cellular processes, including embryonic development, cell differentiation, survival, and apoptosis. Recently, it was reported that a GSK-3 inhibitor attenuates lipopolysaccharide (LPS)-induced septic shock and regulates the mortality of endotoxemic mice. However, the detailed mechanism of reduced mortality via GSK-3 inhibition is not well defined. Herein, we showed that GSK-3 inhibition induces extracellular signal-regulated kinase 1/2 (ERK1/2) activation under LPS-stressed conditions via protein kinase C δ (PKCδ) activation. Furthermore, PKCδ-induced ERK1/2 activation by the inhibition of GSK-3 provoked the production of interleukin (IL)-10, playing a crucial role in regulating endotoxemia. Using a mitogen-activated protein kinase kinase-1 (MEK-1) and PKCδ inhibitor, we confirmed that GSK-3 inhibition induces PKCδ and subsequent ERK1/2 activation, resulting in increased IL-10 expression under LPS-treated conditions. We verified that septic shock caused by LPS is attenuated by GSK-3 inhibition using a GSK-3 inhibitor. This relieved endotoxemia induced by GSK-3 inhibition was restored in an ERK1/2-dependent manner. Taken together, IL-10 expression produced by GSK-3 inhibition-induced ERK1/2 activation via PKCδ relieved LPS-mediated endotoxemia. This finding suggests that IL-10 hyperexpression resulting from GSK-3 inhibition-induced ERK activation could be a new therapeutic pathway for endotoxemia.

Adrenergic support in septic shock: a critical review

The definition of septic shock includes sepsis-induced hypotension despite adequate fluid resuscitation, along with the presence of organ perfusion abnormalities, and ultimately cell dysfunction. To restore adequate organ perfusion and cell homeostasis, cardiac output should be restored with volume infusion plus vasopressor agents as indicated. Appropriate arterial pressure for each individual patient and proper arterial oxygen content are key elements to restoring perfusion. Tissue perfusion can be monitored by markers of organ and mitochondrial function, namely urine output, level of consciousness, peripheral skin perfusion, central or mixed venous oxygen saturation, and lactate. The hemodynamic effects of the different vasopressor agents depend on the relative affinity to adrenergic receptors. Those with predominant alpha-agonist activity produce more vasoconstriction (inoconstrictors) while those with predominant beta-agonist stimulation increase cardiac performance (inodilators). The debate about whether one vasopressor agent is superior to another is still ongoing. The Surviving Sepsis Campaign guidelines refer to either norepinephrine or dopamine as the first-choice vasopressor agent to correct hypotension in septic shock. However, recent data from observational and controlled trials have challenged these recommendations concerning different adrenergic agents. As a result, our view on the prescription of vasopressors has changed from a probably oversimplified "one-size-fits-all" approach to a multimodal approach in vasopressor selection.

Obesity Exacerbates Sepsis-Induced Inflammation and Microvascular Dysfunction in Mouse Brain

OBJECTIVE

Obese patients with sepsis have higher morbidity and mortality than lean counterparts, but the mechanisms involved are unknown. The authors examined the inflammatory and thrombogenic responses of the cerebral microvasculature to sepsis induced by cecal ligation and perforation in obese and lean wild-type mice.

METHODS

Leukocyte and platelet adhesion in cerebral microvasculature and behavioral responses were measured in wild-type and obese mice 4 h postperforation. P-selectin expression in different vascular beds was assessed 6 h postperforation. The effects of immunoblockade of P-selectin, ICAM-1, and CD18 on leukocyte and platelet recruitment were evaluated in obese septic animals.

RESULTS

Cerebral venules of obese and wild-type mice assumed a proinflammatory and prothrombogenic phenotype 4 h post-perforation, with greatly exaggerated responses in obese mice compared to the lean counterparts. These enhanced responses were attenuated by blocking P-selectin, CD18, or ICAM-1. Obese mice also exhibited a more profound behavioral deficit after sepsis, which appears to be unrelated to the recruitment of leukocytes and platelets. Cecal ligation and perforation-induced P-selectin expression was greater in obese mice compared with lean counterparts.

CONCLUSIONS

These findings suggest that the increased morbidity to sepsis in obesity may result from exaggerated microvascular inflammatory and thrombogenic responses that include the activation of endothelial cells with subsequent expression of adhesion molecules, such as P-selectin.

Bradykinin protects against brain microvascular endothelial cell death induced by pathophysiological stimuli

The morphological and functional integrity of the microcirculation is compromised in many cardiovascular diseases such as hypertension, diabetes, stroke, and sepsis. Angiotensin converting enzyme inhibitors (ACEi), which are known to favor bradykinin (BK) bioactivity by reducing its metabolism, may have a positive impact on preventing the microvascular structural rarefaction that occurs in these diseases. Our study was designed to test the hypothesis that BK, via B2 receptors (B2R), protects the viability of the microvascular endothelium exposed to the necrotic and apoptotic cell death inducers H(2)O(2) and LPS independently of hemodynamics. Expression (RT-PCR and radioligand binding) and functional (calcium mobilization with fura-2AM, and p42/p44MAPK and Akt phosphorylation assays) experiments revealed the presence of functional B2R in pig cerebral microvascular endothelial cells (pCMVEC). In vitro results showed that the cytocidal effects of H(2)O(2) and LPS on pCMVEC were significantly decreased by a BK pretreatment (MTT and crystal violet tests, annexin-V staining/FACS analysis), which was countered by the B2R antagonist HOE 140. BK treatment coincided with enhanced expression of the cytoprotective proteins COX-2, Bcl-2, and (Cu/Zn)SOD. Ex vivo assays on rat brain explants showed that BK impeded (by approximately 40%) H(2)O(2)-induced microvascular degeneration (lectin-FITC staining). The present study proposes a novel role for BK in microvascular endothelial protection, which may be pertinent to the complex mechanism of action of ACEi explaining their long-term beneficial effects in maintaining vascular integrity.

[Microcirculation of intensive care patients. From the physiology to the bedside]

The microcirculation is unique in its anatomy and physiology and is a self-contained organ system within the human body. It is the site where gas exchange and nutrient supply takes place, but it is also the site which experiences pathological alterations during various shock states and therefore compromises the oxygen supply to tissues and organs. Systemic inflammation for example leads amongst others to increased heterogeneous blood flow, formation of interstitial edema, altered viscosity, leukocyte activation, disturbances in the coagulation system, and to a breakdown of the endothelial barrier function. These alterations inevitably lead to limitations of the oxygen supply to tissues. Without interruption of these pathomechanisms, the dysfunction of the microcirculation will consequently result in organ dysfunction. In this review article a short description of the microcirculatory physiology, the interaction between the macrocirculation and the microcirculation, as well as microcirculatory alterations generated by a systemic inflammatory response will be given. Finally, various therapy options will be described, which, experimentally, can lead to an improvement in microcirculatory dysfunction.

Pathogenetic and prognostic significance of altered coagulation and fibrinolysis in acute lung injury/acute respiratory distress syndrome

OBJECTIVE

The coagulation and inflammatory cascades may be linked in the pathogenesis of acute lung injury and acute respiratory distress syndrome. However, direct evidence for the contribution of abnormalities in coagulation and fibrinolysis proteins to outcomes in patients with acute lung injury/acute respiratory distress syndrome is lacking.

DESIGN

Retrospective measurement of plasma levels of protein C and plasminogen activator inhibitor-1 in plasma samples that were collected prospectively as part of a large multicenter clinical trial. The primary outcome was hospital mortality. To evaluate the potential additive value of abnormalities of these biomarkers, the excess relative risk of death was calculated for each combination of quartiles of protein-C and plasminogen activator inhibitor-1 levels.

SETTING

Ten university medical centers.

PATIENTS

The study included 779 patients from a multicenter clinical trial of a protective ventilatory strategy in acute lung injury/acute respiratory distress syndrome and 99 patients with acute cardiogenic pulmonary edema, as well as ten normal controls.

MEASUREMENTS AND MAIN RESULTS

Compared with plasma from controls and patients with acute cardiogenic pulmonary edema, baseline protein-C levels were low and baseline plasminogen activator inhibitor-1 levels were elevated in acute lung injury/acute respiratory distress syndrome. By multivariate analysis, lower protein C and higher plasminogen activator inhibitor-1 were strong independent predictors of mortality, and ventilator-free and organ-failure-free days. Plasminogen activator inhibitor-1 and protein C had a synergistic interaction for the risk of death.

CONCLUSIONS

Early acute lung injury/acute respiratory distress syndrome is characterized by decreased plasma levels of protein C and increased plasma levels of plasminogen activator inhibitor-1 that are independent risk factors for mortality and adverse clinical outcomes. Measurement of plasminogen activator inhibitor-1 and protein-C levels may be useful to identify those at highest risk of adverse clinical outcomes for the development of new therapies.

EF6265, a novel plasma carboxypeptidase B inhibitor, protects against renal dysfunction in rat thrombotic glomerulonephritis through enhancing fibrinolysis

BACKGROUND/AIM

Plasma carboxypeptidase B is a physiological fibrinolysis inhibitor. In the present study, the effects of EF6265, a novel specific plasma carboxypeptidase B inhibitor, on renal dysfunction in a rat thrombotic glomerulonephritis model were examined.

METHODS

The model was induced by injection of anti-glomerular basement membrane serum and lipopolysaccharide to rats. Renal microthrombosis was histologically evaluated by phosphotungstic acid-hematoxylin staining for fibrin thrombi. Renal dysfunction was evaluated on the basis of plasma levels of blood urea nitrogen as well as renal edemas and urine volume.

RESULTS

The glomerular microthrombi observed in a positive control group were significantly reduced after a short-term treatment (4 h) with EF6265 at a dose which enhanced fibrinolysis. The elevation of blood urea nitrogen and renal edema formation decreased, and the reduction of the urine volume improved after a long-term treatment (21 h) with EF6265. In addition, EF6265 had a protective activity against multiple organ dysfunction, because it reduced plasma lactate dehydrogenase and alanine aminotransferase levels and mortality in this model.

CONCLUSION

EF6265, which inhibits plasma carboxypeptidase B, showed a protective effect on thrombotic renal dysfunction in thrombotic glomerulonephritis through enhancing the fibrinolysis.

Prostacyclin in sepsis: A systematic review

According to current literature, infective processes greatly modify both vascular hemodynamics and anti-oxidant properties of affected tissues, causing a change in homeostasis that regulates the correct functioning of all cells responsible for the physiological and metabolic balance of various organs. As a consequence, the response to the infection that has caused the change is also likely to be weaker and, in the case of septic shock, ineffective. In this review, we will take into consideration these mechanisms and then focus on a group of vasodilator drugs (prostacyclin and its analogs) which, though have been used for over 20 years mainly to treat obstructive vascular diseases, have such hemodynamic and anti-inflammatory properties which prevent homeostatic changes. It is obvious that prostacyclin does not definitively have anti-infective characteristics; however, in association with anti-infective drugs (antibiotics, etc.), the effectiveness of the latter appears improved, at least in some circumstances. Similarly, the fact that prostacyclin and its analogs have a cytoprotective effect on the liver and reduce the ischemia-reperfusion damage following liver transplant is not a novelty and evidence that they improve hepatic hemodynamics suggests their use in those pathologies characterized by possible reduced perfusion or ascertained ischemia of the liver.

Role of Antithrombin and Factor XIII In Leukocyte-Independent Plasma Extravasation During Endotoxemia: An Intravital-Microscopic Study in the Rat

BACKGROUND

Platelet-endothelial interactions have been shown to be main mediators of leukocyte-independent endothelial damage. Besides altering platelet-endothelial interactions, both antithrombin and factor XIII reduce microvascular permeability in leukocyte-dependent experimental models. Thus, it was our aim to investigate the effects of antithrombin and factor XIII on microvascular permeability during leukocyte-independent endotoxemia.

MATERIAL AND METHODS

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, 60, and 120 min after the start of the experiment. Fucoidin and a continuous infusion of lipopolysaccharides were used to generate leukocyte-independent endotoxemia. The experiment was divided into two parts 1) an antithrombin study and 2) a factor XIII study.

RESULTS

No differences between groups in leukocyte rolling and venular wall shear rate could be observed in both parts of the experiment. Pretreatment with antithrombin reduced microvascular permeability significantly compared with control subjects (120 min: Fuco [untreated]: 0.14 +/- 0.03; Fuco/ETX [control]: 0.37 +/- 0.06; Fuco + ATIII/ETX: 0.15 +/- 0.02; P < 0.05). Factor XIII reduced microvascular permeability significantly after 60 min (Fuco [untreated]: 0.10 +/- 0.03; Fuco/ETX [control]: 0.36 +/- 0.07; Fuco + FXIII/ETX: 0.13 +/- 0.04; P < 0.05). This effect diminished after 120 min (Fuco [untreated]: 0.12 +/- 0.03; Fuco/ETX [control]: 0.5 +/- 0.08; Fuco + FXIII/ETX: 0.29 +/- 0.05; P < 0.05).

CONCLUSIONS

Antithrombin and factor XIII reduce leukocyte-independent microvascular permeability. Yet, factor XIII also shows a nonprotective effect on a long-term basis. These data emphasize the central role of platelets in leukocyte-independent endotoxemia.

High-dose antithrombin III in the treatment of severe sepsis in patients with a high risk of death: efficacy and safety

OBJECTIVE

To explore if patients with severe sepsis and with a predicted high risk of death (according to the Simplified Acute Physiology Score II) might have a treatment benefit from high-dose antithrombin III.

DESIGN

Subgroup analysis of a randomized, placebo-controlled, double-blind, prospective phase III study.

SETTING

Unifactorial and multifactorial reanalysis of prospectively defined populations from the KyberSept trial.

PATIENTS

We studied 1,008 patients (43.6% of the overall intention-to-treat population, n = 2,314) with a predicted mortality rate of 30-60% at study entry as defined by the Simplified Acute Physiology Score II.

INTERVENTIONS

Patients were randomized in a 1:1 fashion to receive either high-dose antithrombin III (30,000 IU intravenously over the period of 4 days) or placebo.

MEASUREMENTS AND MAIN RESULTS

In a Kaplan-Meier analysis of patients with a predicted mortality of 30-60%, the survival time when followed up for 90 days after admission was increased in the high-dose antithrombin III group compared with placebo (p = .04). If heparin was avoided during the 4-day treatment phase with high-dose antithrombin III (n = 140) or placebo (n = 162), the treatment effect appeared to be even more pronounced: 28-day mortality rate, 35.7% vs. 44.4% (risk ratio, 0.804; 95% confidence interval, 0.607-1.064); 56-day mortality rate, 39.9% vs. 52.2% (risk ratio, 0.764; 95% confidence interval, 0.593-0.984); 90-day mortality rate, 42.8% vs. 55.1% (risk ratio, 0.776; 95% confidence interval, 0.614-0.986). Like in the overall population, the percentage with any bleeding was increased in patients receiving high-dose antithrombin III compared with placebo. Survival rates were in favor of high-dose antithrombin III in patients both with and without bleeding complications.

CONCLUSIONS

Treatment with high-dose antithrombin III may increase survival time up to 90 days in patients with severe sepsis and high risk of death. This benefit may even be stronger when concomitant heparin is avoided.

Elasticity and adhesion of resting and lipopolysaccharide-stimulated macrophages

Colloidal Force Microscopy was employed to study the viscoelastic and adhesive properties of macrophages upon stimulation with lipopolysaccharide (LPS). Force vs. distance measurements were performed. The adhesion of LPS-stimulated cells (separation force=37+/-3 nN) was almost twice as high as that of resting macrophages (16+/-1 nN). Upon retraction pulling of membrane tethers was observed. Tether lengths and forces at which rupture take place did not depend on stimulation. The reduced Young's modulus K, a measure of cytoskeleton elasticity, was three times lower than that of the control. The data show that LPS has profound effects on cytomechanical and adhesion properties of macrophages.

Microvascular dysfunction and skeletal muscle oxygenation assessed by phase-modulation near-infrared spectroscopy in patients with septic shock

OBJECTIVE

Sepsis is now considered a disease of the microcirculation. Little is known about the various sepsis-induced changes responsible for microvascular dysfunction. We investigated human microvascular function, regulation, oxygenation, and cellular metabolism during subacute septic shock.

DESIGN AND SETTING

Prospective case-control study in a nine-bed polyvalent surgical ICU of a university hospital.

PATIENTS AND PARTICIPANTS

A prospectively enrolled group of 26 patients (13 with septic shock, 13 nonseptic postsurgical patients) and 15 healthy volunteer controls.

MEASUREMENTS AND RESULTS

The absolute tissue hemoglobin concentrations (oxygenated hemoglobin and deoxyhemoglobin) were measured noninvasively in arterioles, capillaries, and venules by phase-modulation near-infrared spectroscopy in the human brachioradial muscle during a series of venous occlusions and an arterial occlusion (ischemia) induced by applying a pneumatic cuff. These measurements were used to calculate tissue blood volume, postischemic hemoglobin resaturation time, microvascular compliance, and O2 consumption. Patients with sepsis had significantly higher tissue blood volume values and lower compliance than healthy controls. They also had longer postischemic hemoglobin resaturation times than the other two groups and blunted resaturation curves. O2 consumption was lower in patients with sepsis than in healthy controls. In patients with septic shock cuff-induced ischemia left O2 consumption unchanged, whereas in healthy volunteers it reduced O2 consumption to values almost matching those of patients with septic shock.

CONCLUSIONS

These findings show that septic shock alters microvascular muscle function and regulation. Diminished local VO2 presumably reflects maldistribution and faulty autoregulation of local blood flow.

The endothelium in intensive care

This article reviews the major role that the vascular endothelium plays in pathophysiological processes related to metabolism, vascular function, and blood coagulation. Normally an antithrombotic surface, inflammation activates endothelium to become a prothrombotic and pro-inflammatory interface that is critically involved in multi-organ failure in patients with severe systemic diseases including sepsis. Improving endothelial functions in sepsis is a major therapeutic challenge.

Antithrombin ameliorates endotoxin-induced organ dysfunction more efficiently when combined with danaparoid sodium than with unfractionated heparin

OBJECTIVE

This study investigated the potential benefits of combination therapy using antithrombin (AT) with danaparoid sodium (DA) compared with the use of AT with unfractionated heparin (UFH) in the treatment of sepsis.

METHODS

Rats infused with lipopolysaccharide were treated with either DA alone, AT alone, AT plus DA, AT plus UFH, or human serum albumin as controls. AT (125 U/kg) was injected into the AT group immediately after lipopolysaccharide infusion. The AT/DA and AT/UFH groups received the same dose of AT in conjunction with either DA (400 U/kg) or UFH (400 U/kg). The status of the mesenteric microcirculation was examined by intra-vital microscopy and the laboratory indices of coagulation, inflammation, and organ dysfunction were measured.

RESULTS

The coagulation markers were improved following the administration of DA or UFH. The decreases in the WBC counts were significantly suppressed in the AT/DA group. The elevation of IL-6 decreased in the AT, DA, and AT/DA groups (all p<0.01) but not in the AT/UFH group. The prostaglandin I2 levels were significantly elevated only in the AT/DA group (p<0.05). The WBC adhesion was significantly suppressed in the DA, AT/UFH, and AT/DA groups (p<0.05), and the RBC velocity was best maintained in the AT/DA group with no associated increase in capillary hemorrhage. The elevation of ALT and BUN significantly improved only in the AT/DA group. ONCLUSION: Organ dysfunction can thus be alleviated by even moderate doses of AT replacement when co-administered with DA.

Cyclic AMP alleviates endoplasmic stress and programmed cell death induced by lipopolysaccharides in human endothelial cells

The possible protection provided by enhancement of the cAMP signal in the process of lipopolysaccharide (LPS)-induced endothelial cell death has been addressed, with special emphasis on the endoplasmic initiation of caspase-12-mediated apoptosis. Human umbilical vein endothelial cells were challenged with LPS to reduce viability after 12 h to less than 20% that of the control. Cell death was preceded by ultrastructural disintegration at the endoplasmic reticulum, PERK-phosphorylation, degradation of caspase-12-like protein and cleavage of caspase 9, resulting in apoptosis through the activation of caspase 3. Treatment with a cell-permeable cAMP analogue led to a dose-dependent reduction of cell death over time, mitigated endoplasmic reticulum disturbances, reduced phosphorylation of PERK, and the degradation of caspases 12, 9 and 3. The selective inhibition of caspase 9 completely supplanted the anti-apoptotic effects obtained by cAMP, while being without any influence on caspase 12 degradation. The data suggest that cAMP positively modulates early endoplasmic alterations and caspase activation in LPS-induced apoptosis.

Post-traumatic inflammatory response: perhaps a succession of phases with a nutritional purpose

Post-traumatic inflammatory response, whether this be local or systemic, is considered to be the succession of three functional phases called nervous, immune and endocrine, that could have a nutritional significance. In the nervous phase, ischemia-reperfusion, which causes interstitial and cellular edema, is produced. Both types of edema could represent an ancestral mechanism to feed the cells by diffusion. During the immune phase, the tissues are infiltrated by inflammatory cells and bacteria. Then, extracellular digestion, by enzyme release (fermentation), and intracellular digestion by phagocytosis could be associated with a hypothetical trophic capacity for the neighbouring cells. Finally, in the late or endocrine phase nutrition mediated by the blood capillaries is established. In these three successive phases the inflammatory response goes on from an anaerobic metabolism (ischemia) through a metabolism characterized by a defective oxygen use (reperfusion, oxidative burst and heat hyperproduction) to an oxidative metabolism (oxidative phosphorilation) with a correct use of oxygen to produce usable energy. This type of metabolism is characterized by a large production of ATP, which is used to drive specialized multiple cellular processes. Since the nervous, immune and endocrine phases of the inflammatory response go from ischemia to the development of an oxidative metabolism, It is also tempting to speculate on whether the body reproduces the successive stages by which life passes from its origin without oxygen until it develops an effective, although costly, system for the use of oxygen every time we suffer post-traumatic acute inflammation.

Posttraumatic inflammation is a complex response based on the pathological expression of the nervous, immune, and endocrine functional systems

The successive phases that make up both the local and systemic posttraumatic acute inflammatory response could represent the expression of three concatenated pathological or "primitive" functional systems with trophic properties: the nervous, immune, and endocrine ones. The nervous functional system would play an important role in the phenomenon of ischemia-reperfusion, which would be represented by nutrition by diffusion that is either anaerobic (ischemia) or with defective use of oxygen (reperfusion) and, thus, with a limited energy requirement. The immune functional system would be represented by the infiltration of the tissues by inflammatory cells and bacteria, which would become mediators in providing nutrition to the injured tissues. Although the use of oxygen would still be defective, hypermetabolism and fever would occur. In these inflammatory response phases, the lymphatic is the most important circulation. The endocrine functional system would be the most specialized and would have high energy requirements because it would be represented by the blood capillary-mediated nutrition. Highly specialized epithelial cells would already possess a perfected oxidative metabolism. The successive expression of these three functional systems during embryonic development and also during the evolutionary development of our species could explain why the inflammatory response is a ubiquitous mechanism that is common to multiple diseases, because it is an integrator of the ontogeny and phylogeny.

Rôle de la dysfonction endothéliale dans la mortalité liée au sepsis

During the past decade, a unifying hypothesis has been developed to explain the vascular changes that occur in septic shock on the basis of the effect of inflammatory mediators on the vascular endothelium. The vascular endothelium plays a central role in the control of microvascular flow, and it has been proposed that widespread vascular endothelial activation, dysfunction and eventually injury occur in septic shock, ultimately resulting in multiorgan failure. This has been characterised in various models of experimental septic shock. Now, direct and indirect evidence for endothelial cell alteration in humans during septic shock is emerging. The present review details recently published literature on this rapidly evolving topic.

Modulation of endotoxin-induced endothelial function by calcium/calmodulin-dependent protein kinase

Endothelial cells facilitate sepsis-induced neutrophil adherence through the production of adhesion molecules and proinflammatory cytokines. The production of these factors requires coordinated intracellular inflammatory signaling. Recently, patients prone to sepsis-induced complications have been shown to have derangements in intracellular calcium and potentially calcium/calmodulin-dependent protein kinase (CaMK) activity, but the impact of these impairments is unknown. Human umbilical vein endothelial vein endothelial cells (HUVECs) were exposed to lipopolysaccharide (LPS) for various periods of time. Select HUVECs were pretreated with an inhibitor of CaMK II, KN62. Total cellular and nuclear proteins were extracted and analyzed for various components of the Toll-mediated signal cascade. Neutrophil adhesion was assayed fluorometrically using calcein-labeled neutrophils on treated HUVECs. LPS stimulation led to mitogen-activated protein kinase activation and translocation of activator protein-1 (AP-1) and nuclear factor (NF)-kappaB. CaMK blockade inhibited LPS induced ERK 1/2 and JNK but enhanced p38 activity. This selective MAPK inhibition was associated with a reduction in AP-1 activity, with no affect on NF-kappaB activity. Associated with this altered cell signaling was increased ICAM-1 production and enhanced neutrophil adhesion. Altered CaMK activity resulted in dysregulated mitogen-activated protein kinase signaling, demonstrated by reduced ERK 1/2 and JNK activity but enhanced p38 activity. This altered signaling is associated with reduced AP-1 activation and unaffected NF-kappaB activation. Neutrophil adhesion, however, is enhanced presumably through increased ICAM-1 production. Therefore, CaMK inhibition of endothelial cells, characteristic of sustained increases in intracellular calcium, appears to result in a dysregulated proadhesive phenotype.

Drotrecogin alfa (activated) in the treatment of severe sepsis patients with multiple-organ dysfunction: data from the PROWESS trial

OBJECTIVE

Based on the results of the PROWESS trial the European Agency for the Evaluation of Medicinal Products has recently approved drotrecogin alfa (activated) for treatment of adult patients with severe sepsis and multiple-organ failure. We report study's data on efficacy and safety in patients with multiple-organ dysfunction.

DESIGN AND SETTING

Randomized, double-blind, placebo-controlled, multicenter trial in 164 medical centers.

PATIENTS

1271 patients (75.2% of the intention-to-treat population, n=1690) with multiple-organ dysfunction at study entry.

INTERVENTIONS

Drotrecogin alfa (activated) n=634, 24 micro g/kg per hour for 96 h or placebo ( n=637).

RESULTS

Observed 28-day mortality was significantly lower with drug treatment than with placebo (26.5%vs. 33.9%), cardiovascular and respiratory organ dysfunction resolved more rapidly over the first 7 days, and serious bleeding events were more frequent (2.4% vs. 1.3%).

CONCLUSIONS

Treatment with drotrecogin alfa (activated) significantly reduced 28-day mortality and more quickly resolved cardiovascular and respiratory organ dysfunction. The difference in serious bleeding event rates may be clinically significant; however, the overall benefit-risk profile appears favorable.

Bench-to-bedside review: endothelial cell dysfunction in severe sepsis: a role in organ dysfunction?

During the past decade a unifying hypothesis has been developed to explain the vascular changes that occur in septic shock on the basis of the effect of inflammatory mediators on the vascular endothelium. The vascular endothelium plays a central role in the control of microvascular flow, and it has been proposed that widespread vascular endothelial activation, dysfunction and eventually injury occurs in septic shock, ultimately resulting in multiorgan failure. This has been characterized in various models of experimental septic shock. Now, direct and indirect evidence for endothelial cell alteration in humans during septic shock is emerging. The present review details recently published literature on this rapidly evolving topic.