Prevention and treatment of acute renal failure in sepsis

Sepsis-Associated Acute Kidney Injury: Pathophysiology and Treatment Modalities

Sepsis-associated acute kidney injury (S-AKI) is a critical complication that significantly contributes to the morbidity and mortality of sepsis patients. This narrative review explores the complex and multifactorial pathophysiology of S-AKI, which involves hemodynamic alterations, microcirculatory dysfunction, endothelial damage, inflammatory responses, oxidative stress, and direct tubular injury. Conventional perspectives linking S-AKI primarily to reduced renal blood flow are now being reconsidered, with growing insights highlighting the significance of microcirculatory dysfunction and endothelial activation as key contributors. The review also discusses the current diagnostic approaches for S-AKI, emphasizing the limitations of existing biomarkers and the need for earlier and more accurate detection methods. Standard treatment strategies focus on supportive care, including fluid management, vasopressor therapy, and renal replacement therapy. However, these approaches often fail to address the underlying mechanisms of S-AKI, resulting in persistently high mortality rates. Emerging therapies, including the use of antioxidants, anti-inflammatory agents, and stem cell-based treatments, offer the potential for improved outcomes. These innovative approaches aim to target the pathophysiological processes at the molecular level, offering hope for better management of S-AKI. The review highlights the need for ongoing research to further understand the mechanisms driving S-AKI and to develop more effective therapeutic strategies.

Acute superior mesenteric artery syndrome complicated by severe gastric, pancreatic and renal ischaemia

Superior mesenteric artery syndrome (SMAS) is a rare and potentially life-threatening cause of small bowel obstruction in which the superior mesenteric artery impinges on the third portion of the duodenum. SMAS is typically encountered in patients with low body fat and a history of rapid weight loss and is often diagnosed as a chronic or subacute condition. Here, we describe a case of a healthy adolescent boy without typical SMAS prodromal symptoms presenting with a severe, hyperacute proximal small bowel obstruction due to SMAS. Complications arising from massive gastric and duodenal distension, including gastric, pancreatic and renal ischaemia, necessitated emergent surgical intervention consisting of the duodenojejunostomy bypass with partial gastric resection. The patient recovered without significant lasting consequences.

Disseminated intravascular coagulation is strongly associated with severe acute kidney injury in patients with septic shock

BACKGROUND

Disseminated intravascular coagulation (DIC) worsens the prognosis of septic shock and contributes to multiple organ failure. To date, no data linking DIC and acute kidney injury (AKI) occurrence, severity, and evolution in this setting are available. We aimed at analyzing the association between AKI occurrence, severity and evolution in patients with septic shock-induced DIC. In a prospective monocentric cohort study, consecutive patients, 18 years and older, admitted in the ICU of Strasbourg University Hospital in the setting of systemic hypotension requiring vasopressor related to an infection, without history of terminal chronic kidney disease were eligible. AKI was defined according to the KDIGO classification. DIC diagnosis was based on the International Society on Thrombosis and Haemostasis (ISTH) score. Evolution of AKI was evaluated through the composite endpoint of major adverse kidney events. Only patients with DIC that occurred before or at the time of AKI diagnosis were considered. Univariate and multivariate analysis were performed to determine factors associated with renal outcomes.

RESULTS

350 patients were included, of whom 129 experienced DIC. Patients with DIC were more seriously ill (median SAPS II 64 vs. 56, p < 0.001), and had higher 28-day mortality (43.3% vs. 26.2%, p < 0.001). AKI was more frequent in patients with DIC (86.8% vs. 74.2%, p < 0.005), particularly for the more severe stage of AKI [KDIGO 3 in 58.1% of patients with DIC vs. 30.8% of patients without DIC, p < 0.001, AKI requiring renal replacement therapy (RRT) in 47.3% of patients with DIC vs. 21.3% of patients without DIC, p < 0.001]. After adjustment for confounding factors, DIC occurrence remained associated with the risk of having the more severe stage of AKI with an odds ratio (OR) of 2.74 [IC 95% (1.53-4.91), p < 0.001], and with the risk of requiring RRT during the ICU stay [OR 2.82 (1.53-5.2), p < 0.001].

CONCLUSION

DIC appears to be strongly associated with the risk of developing the more severe form of AKI (stage 3 of the KDIGO classification, RRT requirement), even after adjustment for severity and other relevant factors.

NEPHROPROTECTIVE EFFECT OF GAMMA-SECRETASE INHIBITOR ON SEPSIS- INDUCED RENAL INJURY IN MOUSE MODEL OF CLP

OBJECTIVE

The aim: This study was set out to assess the potential protective impact of MK0752 (a gamma secretase inhibitor) on sepsis-induced renal injury through modulation of inflammatory and oxidative stress pathways.

PATIENTS AND METHODS

Materials and methods: Twenty-four Swiss-albino mice aged between eight and twelve week and weighted twenty to thirty-seven grams were randomly allocated into four groups (n=6 in each group). Sham group (laparotomy without cecal ligation and puncture (CLP), sepsis group (laparotomy with CLP), vehicle-treated group (equivalent volume of DMSO before the CLP), MK0752 treated group (5 mg/kg) single daily dose for three days before the CLP. Blood samples were used to assess the serum levels of urea and creatinine. The kidneys were used to assess tissue levels of the TNF-α, IL-10, IL-6, TNFR1, VEGF, notch1, jagged1 and tissue damage by histopathological analysis.

RESULTS

Results: The current study shows that pretreatment with MK0752 ameliorates the renal damage by significantly reducing the proinflammatory cytokines and notch1 signaling.

CONCLUSION

Conclusions: Taken together, these results suggest that MK0752 could be protective against the renal injury induced by sepsis through its ameliorative impact on renal architecture and modulating cytokines and Notch1 singling pathway. Further studies regarding the role of Notch signaling pathways would be worthwhile.

Correlation between thrombopoietin and inflammatory factors, platelet indices, and thrombosis in patients with sepsis: A retrospective study

BACKGROUND

Thrombopoietin (TPO) is a primary regulator of thrombopoiesis in physiological conditions. TPO, in combination with its specific cytokine receptor c-Mpl, drives platelet production by inducing the proliferation and differentiation of megakaryocytes. However, the role of TPO in sepsis is not well determined. The elevated levels of TPO are often accompanied by a decrease of platelet count (PLT) in systemic infected conditions, which is contrary to the view that TPO promotes platelet production under physiological conditions. In addition, whether TPO mediates organ damage in sepsis remains controversial.

AIM

To explore the relationships between TPO and inflammatory factors, platelet indices, and thrombotic indicators in sepsis.

METHODS

A total of 90 patients with sepsis diagnosed and treated at the emergency medicine department of The First People’s Hospital of Foshan between January 2020 and March 2021 were enrolled in this study. In addition, 110 patients without sepsis who came to the emergency medicine department were included as controls. Clinical and laboratory parameters including age, gender, TPO, blood cell count in peripheral blood, platelet indices, inflammatory factors such as high-sensitivity C-reactive protein (hs-CRP), interleukin (IL)-21, and IL-6, organ damage indicators, and thrombotic indicators were collected and analyzed by using various statistical approaches.

RESULTS

The results showed that the TPO levels were higher in the sepsis group than in controls [86.45 (30.55, 193.1) vs 12.45 (0.64, 46.09) pg/mL, P < 0.001], but PLT was lower (P < 0.001). Multivariable analysis showed that white blood cell count (WBC) [odds ratio (OR) = 1.32; 95% confidence interval (CI): 1.01-1.722; P = 0.044], TPO (OR = 1.02; 95%CI: 1.01-1.04; P = 0.009), IL-21 (OR = 1.02; 95%CI: 1.00-1.03; P = 0.019), troponin I (OR = 55.20; 95%CI: 5.69-535.90; P = 0.001), and prothrombin time (PT) (OR = 2.24; 95%CI: 1.10-4.55; P = 0.027) were independent risk factors associated with sepsis. TPO levels were positively correlated with IL-21, IL-6, hs-CRP, creatinine, D-dimer, PT, activated prothrombin time, international normalized ratio, fibrinogen, WBC count, and neutrophil count, and negatively correlated with PLT, thrombin time, red blood cell count, and hemoglobin concentration (P < 0.05). Receiver operating characteristic analysis showed that TPO had fair predictive value in distinguishing septic patients and non-septic patients (the area under the curve: 0.788; 95%CI: 0.723-0.852; P < 0.001). With an optimized cutoff value (28.51 pg/mL), TPO had the highest sensitivity (79%) and specificity (65%).

CONCLUSION

TPO levels are independently associated with sepsis. High TPO levels and low PLT suggest that TPO might be an acute-phase response protein in patients with infection.

Detecting Novel Ototoxins and Potentiation of Ototoxicity by Disease Settings

Over 100 drugs and chemicals are associated with permanent hearing loss, tinnitus, and vestibular deficits, collectively known as ototoxicity. The ototoxic potential of drugs is rarely assessed in pre-clinical drug development or during clinical trials, so this debilitating side-effect is often discovered as patients begin to report hearing loss. Furthermore, drug-induced ototoxicity in adults, and particularly in elderly patients, may go unrecognized due to hearing loss from a variety of etiologies because of a lack of baseline assessments immediately prior to novel therapeutic treatment. During the current pandemic, there is an intense effort to identify new drugs or repurpose FDA-approved drugs to treat COVID-19. Several potential COVID-19 therapeutics are known ototoxins, including chloroquine (CQ) and lopinavir-ritonavir, demonstrating the necessity to identify ototoxic potential in existing and novel medicines. Furthermore, several factors are emerging as potentiators of ototoxicity, such as inflammation (a hallmark of COVID-19), genetic polymorphisms, and ototoxic synergy with co-therapeutics, increasing the necessity to evaluate a drug's potential to induce ototoxicity under varying conditions. Here, we review the potential of COVID-19 therapies to induce ototoxicity and factors that may compound their ototoxic effects. We then discuss two models for rapidly detecting the potential for ototoxicity: mammalian auditory cell lines and the larval zebrafish lateral line. These models offer considerable value for pre-clinical drug development, including development of COVID-19 therapies. Finally, we show the validity of in silico screening for ototoxic potential using a computational model that compares structural similarity of compounds of interest with a database of known ototoxins and non-ototoxins. Preclinical screening at in silico, in vitro, and in vivo levels can provide an earlier indication of the potential for ototoxicity and identify the subset of candidate therapeutics for treating COVID-19 that need to be monitored for ototoxicity as for other widely-used clinical therapeutics, like aminoglycosides and cisplatin.

Venous thromboembolism and COVID-19: a single center experience from an academic tertiary referral hospital of Northern Italy

Preliminary evidence supports the notion that COVID-19 patients may have an increased susceptibility to develop venous thromboembolism (VTE). However, the magnitude of this association still needs to be defined. Furthermore, clinical predictors of thrombogenesis, and the relationship with the inflammatory status are currently unknown. On this basis, we conducted a retrospective, observational study on 259 consecutive COVID-19 patients admitted to an academic tertiary referral hospital in Northern Italy between March 19th and April 6th, 2020. Records of COVID-19 patients with a definite VTE event were reviewed for demographic information, co-morbidities, risk factors for VTE, laboratory tests, and anticoagulation treatment. Twenty-five cases among 259 COVID-19 patients developed VTE (9.6%), all of them having a Padua score > 4, although being under standard anticoagulation prophylaxis since hospital admission. In the VTE subcohort, we found a significant positive correlation between platelet count (PLT) and either C reactive protein (CRP) (p < 0.0001) or lactate dehydrogenase (LDH) (p = 0.0013), while a significant inverse correlation was observed between PLT and mean platelet volume (p < 0.0001). Platelet-to-lymphocyte ratio significantly correlated with CRP (p < 0.0001). The majority of VTE patients was male and younger compared to non-VTE patients (p = 0.002 and p = 0.005, respectively). No significant difference was found in D-dimer levels between VTE and non VTE patients, while significantly higher levels of LDH (p = 0.04) and IL-6 (p = 0.04) were observed in VTE patients in comparison to non-VTE patients. In conclusion, our findings showed a quite high prevalence of VTE in COVID-19 patients. Raised inflammatory indexes and increased serum levels of pro-inflammatory cytokines should raise the clinical suspicion of VTE.

The John F. Maher Recipient Lecture 2004: Rage in the Peritoneum

Several conditions in the peritoneal membrane of peritoneal dialysis (PD) patients promote the accumulation of advanced glycation end-products (AGEs), that is, the uremic state, exposure to high glucose concentrations, and exposure to glucose degradation products (GDPs). AGEs exert some of their biologic actions through binding with a cell surface receptor, termed RAGE. Interaction of AGEs with RAGE induces sustained cellular activation, including the production of the fibrogenic growth factor, transforming growth factor-beta (TGF-β). TGF-β is pivotal in the process of epithelial-to-mesenchymal transition, through which cells of epithelial origin acquire myofibroblastic characteristics. Myofibroblasts are involved in virtually all conditions of pathological fibrosis. Submesothelial fibrosis is an important feature in peritoneal biopsies of PD patients, especially of those with clinical problems. We therefore examined the role of RAGE in peritoneal fibrosis, in an animal model of uremia, of high glucose exposure, and of peritoneal dialysate exposure.

All three models were characterized by accumulation of AGEs, upregulation of RAGE, and fibrosis. Antagonism of RAGE prevented the upregulation of TGF-β and fibrosis in the peritoneal membrane. We further examined the underlying mechanism of peritoneal fibrosis in the uremic model. Prominent myofibroblast transdifferentiation of mesothelial cells was identified by co-localization of cytokeratin and α-smooth muscle actin in submesothelial and interstitial fibrotic tissue. Antagonism of RAGE prevented conversion of mesothelial cells to myofibroblasts in uremia.

In conclusion, we hypothesize that accumulation of AGEs in the peritoneal membrane, as a consequence of the uremic environment, chronic exposure to high glucose, and exposure to GDPs, results in an increased expression of RAGE. The interaction of AGEs with RAGE induces peritoneal fibrosis by virtue of upregulation of TGF-β and subsequent conversion of mesothelial cells into myofibroblasts.

Encapsulating Peritoneal Sclerosis—A Clinician's Approach to Diagnosis and Medical Treatment

Encapsulating peritoneal sclerosis (EPS) is recognized as a serious complication of continuous peritoneal dialysis. A preliminary diagnosis of EPS is usually based on clinical signs and symptoms, which commonly include abdominal pain, nausea, vomiting, anorexia, abdominal fullness, an abdominal mass, bowel obstruction, and radiologic findings, including abdominal roentgenogram, contrast studies, ultrasound studies, and computed tomography. The diagnosis is confirmed by laparoscopy or laparotomy showing the characteristic gross thickening of the peritoneum enclosing some or all of the small intestine in a cocoon of opaque tissue.

A variety of therapeutic approaches to EPS have been reported. This review discusses medical treatment of EPS and includes an overview of the clinical features and diagnostic aspects of the condition.

Antibiotic Prophylaxis in an Animal Model of Chronic Peritoneal Exposure

Objectives

Acute infection in an animal model of chronic peritoneal dialysis (PD) induces structural changes in the peritoneum and alters functional characteristics of transport. These changes may compromise observations of the chronic effects of dialysis solutions. To test the hypothesis that antibiotics would prevent acute infection without affecting transport and structural properties, we characterized the frequency of infection in our rat model of PD and examined whether the inclusion of antibiotics in the dialysis solution altered the transport and structural properties of the peritoneum.

Design

Female Sprague–Dawley rats were aseptically injected daily under gas anesthesia with 30 – 40 mL of a sterile solution for 2 months via a peritoneal catheter tunneled to a subcutaneous port. Solutions used were Krebs–Ringer bicarbonate (KRB) alone, KRB with antibiotics (cefazolin 200 mg/L and gentamicin 2 mg/L), KRB with 4% glucose, and KRB with both glucose and antibiotics. After 2 months, osmotic filtration and solute transport were assessed in each animal and peritoneal fluid was collected for bacterial culture. Angiogenesis was evaluated by quantitative image analysis of tissue sections stained with CD31. Tissue content of collagen, hyaluronic acid, and sulfated glycosaminoglycan was determined.

Results

Technique survival (successful PD for 2 months) and infection rate were comparable among all treated groups. There were no differences between the groups in transport properties. Structural changes were comparable between groups, with or without antibiotics.

Conclusions

Addition of antibiotics to the dialysis solution did not affect the transport characteristics of the peritoneum or the pathologic reaction of the tissue to the PD solution.

ImprovedIn VitroBiocompatibility of Bicarbonate-Buffered Peritoneal Dialysis Fluid

Background

Conventional peritoneal dialysis fluids (PDFs) have been shown to damage the mesothelial layer and are associated with the development of peritoneal fibrosis and neoangiogenesis. New-generation PDFs have therefore been developed with physiological pH and reduced levels of glucose degradation products (GDPs), precursors of advanced glycation end products (AGEs). In this work, we evaluated and compared the improved biocompatibility of two new-generation PDFs (Balance and bicaVera) using mesothelial cell biology; we also compared them to a standard PDF (stay·safe) (all PDFs by Fresenius Medical Care, Fresnes, France).

Methods

stay·safe, Balance, and bicaVera were tested for their effect on human peritoneal mesothelial cell (HPMC) viability by measuring cell proliferation and apoptosis, and oncosis induction. The formation of AGEs was evaluated by immunoassay. Transforming growth factor beta-1 and vascular endothelial growth factor (VEGF) were immunoassayed in HPMC supernatants exposed to the above PDFs.

Results

At 15 g/L glucose concentration, HPMC exposure to bicaVera resulted in higher cell proliferation compared to Balance ( p < 0.001) and stay·safe ( p < 0.001). Compared to the lactate-buffered PDFs (Balance and stay·safe), oncosis was significantly lower in cells exposed to bicaVera ( p < 0.05). bicaVera, containing lower amounts of GDPs, generated less AGE formation ( p < 0.05) and VEGF production ( p < 0.05) than either Balance or stay·safe.

Conclusions

New-generation PDFs with physiological pH and lower GDP levels, especially if bicarbonate-buffered (bicaVera), have fewer in vitro toxic effects on mesothelial cells and may contribute to peritoneal preservation, thus improving long-term treatment of PD patients.

A Review on The Protective Effects of Metformin in Sepsis-Induced Organ Failure

Despite advances in sepsis management, it remains a major intensive-care-unit (ICU) concern. From new prospective, positive effects of metformin, such as anti-oxidant and anti-inflammatory properties are considered potentially beneficial properties for management of septic patients. This article reviewed the potential ameliorative effects of metformin in sepsis-induced organ failure. Information were retrieved from PubMed, Scopus, Embase, and Google Scholar. Multi-organ damage, oxidative stress, inflammatory cytokine stimulation, and altered circulation are hallmarks of sepsis. Metformin exerts its effect via adenosine monophosphate-activated protein kinase (AMPK) activation. It improves sepsis-induced organ failure by inhibiting the production of reactive oxygen species (ROS) and pro-inflammatory cytokines, preventing the activation of transcription factors related to inflammation, decreasing neutrophil accumulation/infiltration, and also maintaining mitochondrial membrane potential. Studies reported the safety of metformin therapeutic doses, with no evidence of lactic acidosis, in septic patients.

Empirical systemic anticoagulation is associated with decreased venous thromboembolism in critically ill influenza A H1N1 acute respiratory distress syndrome patients

BACKGROUND

An association between increased venous thromboembolism (VTE) events and influenza A H1N1 (H1N1) was noted in the first 10 patients with severe acute respiratory distress syndrome (ARDS). An empirical systemic anticoagulation protocol (heparin intravenous infusion) was initiated when autopsy of patients with severe hypoxemia confirmed multiple primary pulmonary thrombi and emboli. The purpose of this study was to examine the relationship between H1N1 and VTE events and to assess the efficacy of empirical systemic heparin anticoagulation in preventing VTE and death in H1N1 severe ARDS patients.

METHODS

An observational cohort study of critically ill severe ARDS patients with possible H1N1 viral pneumonia was performed in a surgical intensive care unit in a single 990-bed academic tertiary care center. Early empirical systemic heparin anticoagulation for all severe ARDS patients with possible H1N1 viral pneumonia was initiated as a VTE preventive strategy.

RESULTS

Univariate comparisons and multivariate logistic regression were used to identify risk factors for VTE. Independent risk factors for VTE included H1N1, culture-positive bacterial pneumonia, and vasopressor requirement. Independent risk factors for pulmonary embolism included H1N1, culture-positive bacterial pneumonia, and male sex. H1N1 ARDS patients had 23.3-fold higher risk for pulmonary embolism and 17.9-fold increased risk for VTE. Kaplan-Meier analysis and log-rank test confirmed that empirical systemic heparin anticoagulation provided significant protection from thrombotic events in the H1N1-positive but not in the H1N1-negative critically ill ARDs patients. In multivariate analysis, adjusting for H1N1 status, patients without empirical systemic anticoagulation were 33 times more likely to have any VTE compared with those treated with empirical systemic heparin anticoagulation (P = .01).

CONCLUSIONS

Critically ill patients with H1N1 ARDS have increased risk of venous thrombotic complications, particularly pulmonary thromboembolism. Empirical systemic heparin anticoagulation in this cohort of patients significantly reduced VTE incidence without increased hemorrhagic complications.

Pathogenesis of Peritoneal Sclerosis

Peritoneal sclerosis is an almost invariable consequence of peritoneal dialysis. In most circumstances it is “simple” sclerosis, manifesting clinically with an increasing peritoneal transport rate and loss of ultrafiltration capacity. In contrast, encapsulating peritoneal sclerosis is a life threatening and usually irreversible condition, associated with bowel obstruction, malnutrition and death. It is unknown whether common etiological factors underlie the development of these 2 clinically and pathologically distinct forms of peritoneal sclerosis. The majority of studies to date have investigated factors that contribute to “simple” sclerosis, although it remains possible that similar mechanisms are amplified in patients who develop encapsulated peritoneal sclerosis. The cellular elements that promote peritoneal sclerosis include the mesothelial cells, peritoneal fibroblasts and inflammatory cells. Factors that stimulate these cells to promote peritoneal fibrosis and neoangiogenesis, both inherent in the development of peritoneal sclerosis, include cytokines that are induced by exposure of the peritoneal membrane to high concentrations of glucose, advanced glycation of the peritoneal membrane and oxidative stress. The cumulative exposure to bioincompatible dialysate is likely to have an etiological role as the duration of dialysis correlates with the likelihood of developing peritoneal sclerosis. Indeed peritoneal dialysis using more biocompatible fluids has been shown to reduce the development of peritoneal sclerosis. The individual contribution of the factors implicated in the development of peritoneal sclerosis will only be determined by large scale peritoneal biopsy registries, which will be able to prospectively incorporate clinical and histological data and support clinical decision making.

Theoretical Morphological Approach to Simple Peritoneal Sclerosis

The term peritoneal sclerosis can be applied to a vast range of peritoneal alterations. At one end of the range we have the slight peritoneal sclerosis constantly associated with peritoneal dialysis, which may be defined as simple sclerosis. Its clinical impact is slight.

The role of glucose in determining peritoneal sclerosis is supported by morphological studies and therefore backed by much biochemical and immunological data.

Structure and Function of the Kidney in Septic Shock. A Prospective Controlled Experimental Study

RATIONALE

It is unclear how septic shock causes acute kidney injury (AKI) and whether this is associated with histological change.

OBJECTIVES

We aimed to determine the nature and extent of changes in renal structure and function over time in an ovine model of septic shock.

METHODS

Fifteen sheep were instrumented with a renal artery flow probe and renal vein cannula. Ten were given intravenous Escherichia coli to induce septic shock, and five acted as controls. Animals were mechanically ventilated for 48 hours, while receiving protocol-guided parenteral fluids and a norepinephrine infusion to maintain mean arterial pressure. Renal biopsies were taken every 24 hours or whenever animals were oliguric for 2 hours. A renal pathologist, blinded to tissue source, systematically quantified histological appearance by light and electron microscopy for 31 prespecified structural changes.

MEASUREMENTS AND MAIN RESULTS

Sheep given E. coli developed septic shock, oliguria, increased serum creatinine, and reduced creatinine clearance (AKI), but there were no changes over time in renal blood flow between groups (P > 0.30) or over time within groups (P > 0.50). Renal oxygen consumption increased only in nonseptic animals (P = 0.01), but there was no between-group difference in renal lactate flux (P > 0.50). There was little structural disturbance in all biopsies and, although some cellular appearances changed over time, the only difference between septic and nonseptic animals was mesangial expansion on electron microscopy.

CONCLUSIONS

In an intensive care-supported model of gram-negative septic shock, early AKI was not associated with changes in renal blood flow, oxygen delivery, or histological appearance. Other mechanisms must contribute to septic AKI.

Variations of renal tissue oxygenation during abdominal compartment syndrome and sepsis

PURPOSE

This experimental study was designed to evaluate the renal tissue oxygenation under the coexistence of abdominal compartment syndrome and sepsis.

MATERIAL AND METHODS

Fourteen non-breed dogs were divided into two groups: the control group (8) and the study group (6). Sepsis was established with intravenous endotoxin infusion at 100μg/kg for over 30min. Insufflation of CO2 in the peritoneal cavity was used for the increase in intra-abdominal pressure (IAP). A special catheter placed and fixed in the renal cortex at a depth of 3mm from the renal capsule was used for the measurement of renal tissue oxygenation.

RESULTS

Study parameters were recorded at the starting phase, at IAP of 15mmHg and 30mmHg and after decompression of the abdomen in the control group, and at the same intervals plus the induction of sepsis, prior to increasing abdominal pressure, in the study group. With the elevation of the IAP a reduction of renal tissue oxygenation presents itself, which is more pronounced in the presence of sepsis, especially for IAP over 15mmHg. Like other parameters, after abdominal decompression the renal tissue oxygenation returns to the initial levels, independently of sepsis.

CONCLUSIONS

The afferent arterioles vasoconstriction, which takes place during sepsis, and the intra-renal shunt, which occurs and leads to blood diversion to the medulla from the renal cortex due to the combination of intra-abdominal hypertension (IAH) and sepsis, seem to explain this finding.

Neutrophil gelatinase-associated lipocalin attenuates injury in the rat cecal ligation and puncture model of sepsis via apoptosis inhibition

AIM

The aim of this study was to investigate the effect of neutrophil gelatinase-associated lipocalin (NGAL) on the rat cecal ligation and puncture (CLP)-induced sepsis and the possible mechanism.

METHODS

Thirty male Sprague-Dawley rats underwent CLP as sepsis models and were randomized into three groups including the sham-operated group (sham, n = 10), which only underwent a laparotomy; the sepsis group (sepsis, n = 10), which underwent CLP and subcutaneous injection of normal saline; and the sepsis + NGAL group (sepsis + NGAL, n = 10), which underwent CLP and subcutaneous injection of NGAL. Urine, blood and kidney tissue samples were collected for the determination of urine NGAL (uNGAL), plasma NGAL (pNGAL), serum creatinine (Scr), blood urea nitrogen (BUN), histomorphological and immunohistochemical examination, lipid peroxidation product malondialdehyde (MDA) and superoxide dismutase (SOD), and expression of heme oxygenase-1 (HO)-1.

RESULTS

The levels of uNGAL, pNGAL, Scr, BUN, kidney injury score, positive TUNEL staining, activated Caspase-3 and Bax, and kidney tissue MDA levels in the sepsis group were significantly increased compared with those in the sham-operated group and the sepsis + NGAL group (P < 0.05). SOD level and HO-1 expression in sepsis + NGAL group were significantly higher than those in the sham-operated group and the sepsis group (P < 0.05).

CONCLUSION

NGAL can attenuate kidney injury and apoptosis in the rat CLP model of sepsis. And the protective effect of NGAL was probably due to the inhibition of apoptosis and lipid peroxidation, and increased expression of HO-1.

Infectious Diseases and the Kidney in Children

The kidney is involved in a wide range of bacterial, viral, fungal, and parasitic diseases. In most systemic infections, renal involvement is a minor component of the illness, but in some, renal failure may be the presenting feature and the major problem in management. Although individual infectious processes may have a predilection to involve the renal vasculature, glomeruli, interstitium, or collecting systems, a purely anatomic approach to the classification of infectious diseases affecting the kidney is rarely helpful because most infections may involve several different aspects of renal function. In this chapter, a microbiological classification of the organisms affecting the kidney is adopted. Although they are important causes of renal dysfunction in infectious diseases, urinary tract infections and hemolytic uremic syndrome (HUS) are not discussed in detail because they are considered separately in chapters XX and XX, respectively.

Renal haemodynamic response to amino acids infusion in an experimental porcine model of septic shock

BACKGROUND

Acute kidney injury (AKI) is common in sepsis. Treatments allowing maintenance of renal blood flow (RBF) could help to prevent AKI associated with renal hypoperfusion. Amino acids (AA) have been associated with an increase of RBF and glomerular filtration rate (GFR) in several species. The aim of this study was to evaluate the effects of an AA infusion on RBF and GFR in a porcine model of septic shock.

METHODS

A total of 17 piglets were randomly assigned into three groups: Sham (Sham, n = 5), sepsis without AA (S-NAA, n = 6), sepsis treated with AA (S-AA, n = 6). Piglets preparation included the placement of ultrasonic transit time flow probes around left renal artery for continuous RBF measurement; ureteral catheters for GFR and urine output evaluation; pulmonary artery catheter for cardiac output (CO) and pulmonary arterial pressure measurements. Mean arterial pressure (MAP) and renal vascular resistance (RVR) were also determined. Septic shock was induced with a live Pseudomonas aeruginosa infusion. Crystalloids, colloids and epinephrine infusion were used to maintain and restore MAP > 60 mmHg and CO > 80% from baseline.

RESULTS

Renal haemodynamic did not change significantly in the Sham group, whereas RBF increased slightly in the S-NAA group. Conversely, a significant increase in RVR and a decrease in RBF and GFR were observed in the S-AA group. AA infusion was associated with a higher requirement of epinephrine [340.0 (141.2; 542.5) mg vs. 32.5 (3.8; 65.0) mg in the S-NAA group P = 0.044].

CONCLUSION

An infusion of amino acids impaired renal haemodynamics in this experimental model of septic shock.

A novel conditional platelet depletion mouse model reveals the importance of platelets in protection against Staphylococcus aureus bacteremia

BACKGROUND

Platelets are critical cells for maintaining vascular hemostasis, but their activities in other processes are becoming apparent. Specifically, the ability of platelets to recognize and respond to infectious agents is an important area of investigation. To understand the physiologic roles of platelets in vivo, most researchers have used antibody-mediated platelet depletion, which has certain limitations.

OBJECTIVE

To develop an optimal system with which to study the contribution of platelets to protection against S. aureus blood infection.

METHODS

Here, we describe a novel experimental model of conditional platelet depletion based on the Cre-recombinase cell ablation system. With this technology, the simian diphtheria toxin receptor was expressed in platelet factor 4-positive cells (megakaryocytes and platelets).

RESULTS

Systemic administration of diphtheria toxin every 48 h resulted in reduced platelet numbers that became undetectable after 6 days. Although platelets were depleted, no other blood cells were affected. With this newly developed model, the functional contributions of platelets to protection against Staphylococcus aureus bacteremia was examined. Platelet-depleted mice succumbed to infection more rapidly than wild-type mice, and had a significantly higher bacterial burden in kidneys, elevated levels of serum markers of kidney damage, and increased levels of cytokines indicative of septic shock.

CONCLUSIONS

Here, we illustrate a new mouse model for conditional platelet depletion, and implicate platelets as important participants in the immune response to bacterial blood infections.

Effects of ghrelin on sepsis-induced acute kidney injury: one step forward

BACKGROUND

Among the several disorders induced by sepsis, acute kidney injury (AKI) represents the most important economic burden problem that is associated with high mortality and morbidity rates. The aim of this study was to investigate the anti-inflammatory effects of ghrelin in sepsis-induced AKI and the possible role of vagus nerve.

METHODS

Five groups were included: sham, cecal ligation and puncture (CLP), CLP-ghrelin, CLP-vagotomy and CLP-vagotomy-ghrelin group.

RESULTS

Ghrelin treatment immediately after induction of CLP, significantly improved renal Glomerular filtration rate (GFR), serum creatinine, BUN and renal necrosis score as compared to the unprotected CLP group. In addition, ghrelin significantly decreased renal TNF alpha (111.5 ± 10.35 vs. 291.8 ± 15.8 pg/mg ptn), VCAM1 (6.28 ± 1.7 vs. 12.9 ± 1.2 µ/g ptn) and MPO (0.95 ± 0.13 vs. 2.5 ± 0.4 µ/g ptn) without significant increase in renal IL-10. Those effects were abolished by vagotomy.

CONCLUSION

We concluded that ghrelin could represent new therapeutic window in early treatment of sepsis-induced AKI and this could be mainly due to its anti-inflammatory effects.

How to choose the ideal renal replacement therapy in sepsis?

Sepsis is the main cause of acute kidney injury (AKI) among individuals hospitalized in intensive care units. Acute kidney injury is an independent risk factor for mortality, and its occurrence increases the complexity and cost of treatment. However, the pathophysiological mechanisms of AKI remain unclear. Hemodynamic, vascular, tubular, cellular, inflammatory, and oxidative processes are involved. Individuals with AKI generally have various comorbidities and are elderly and hypercatabolic and on vasopressors and mechanical ventilation. Dialysis is the main treatment for AKI. Although there is no clear benefit of any specific dialysis modality, these patients are initially instructed to use continuous dialysis methods, especially for the most severe cases with multiple organ system dysfunctions and for those who display signs of hemodynamic instability. Recent studies demonstrate that patients should receive a dialysis dose of at least 25 mL · kg · h.

Rhabdomyolysis and acute renal failure in a sickle cell trait athlete: a case study

This case study reports the clinical details and pathologic mechanisms of a nonfatal case of rhabdomyolysis secondary to heat exhaustion and sickle cell trait (SCT) resulting in acute renal failure. A 19-year-old African American male college football player collapsed after running 5 intervals of 300 m during a preseason conditioning test. After 17 days of treatment, the athlete was released from the hospital to a short-term noncritical care facility for further treatment and dialysis. Scientific literature reports that at least 15 college football players with SCT have died as a result of a sickling crisis after intense physical exertion. This case study presents the clinical importance of prompt medical treatment and sustained low-efficiency dialysis in treating rhabdomyolysis and its sequelae after collapse in an SCT athlete.

Cannabinoid receptors as therapeutic targets for dialysis-induced peritoneal fibrosis

BACKGROUND

Long-term exposure to bioincompatible peritoneal dialysis solutions is frequently complicated with peritoneal fibrosis and ultrafiltration failure. As cannabinoid receptor (CBR) ligands have been reported to be beneficial to ameliorate the process of liver fibrosis, we strove to investigate their therapeutic potential to prevent peritoneal fibrosis.

METHODS

We used the rat model of peritoneal fibrosis induced by intraperitoneal injection of methylglyoxal and in vitro mesothelial cell culture to test the effects of CBR ligands, including the type 1 CBR (CB(1)R) antagonist and the type 2 CBR (CB(2)R) agonist.

RESULTS

In the methylglyoxal model, both intraperitoneal CB(1)R antagonist (AM281) and CB(2)R agonist (AM1241) treatment significantly ameliorated peritoneal fibrosis. In addition, CB(1)R antagonist was able to alleviate TGF-β(1)-induced dedifferentiation of mesothelial cells and to maintain epithelial integrity in vitro.

CONCLUSIONS

Intraperitoneal administration of CBR ligands (CB(1)R antagonist and CB(2)R agonist) offers a potential therapeutic strategy to reduce dialysis-induced peritoneal fibrosis and to prolong the peritoneal survival in peritoneal dialysis patients.

Microparticles and acute renal dysfunction in septic patients

PURPOSE

The role of microparticles (MPs) in the pathogenesis of sepsis is not completely elucidated. We aimed to assess changes in the number of MPs during severe sepsis to follow the effect of sepsis-related organ failures, particularly renal impairment, an independent mortality factor of sepsis.

MATERIALS AND METHODS

Thirty-seven severe septic patients and 20 controls were enrolled. Patient status as well as organ failure-related laboratory markers was followed up to 5 consecutive days. Microparticles (annexin V+ events in MP size gate) of platelet (CD41, CD42a, and PAC1), monocyte (CD14), and myeloid cell line (CD13) origin were measured using flow cytometry.

RESULTS

Significantly increased total MP and CD41-, CD42a-, and PAC1-positive particle numbers were found in septic patients compared with controls. Actual number of organ dysfunctions on sample collection showed no correlation with MP numbers. Septic patients with renal dysfunction showed an increase in total MP, CD41(+), and CD13(+) particle numbers on admission. Amounts of platelet-derived CD42a(+) particles from patients with sepsis-related renal injury correlated negatively with actual blood urea nitrogen and creatinine concentrations.

CONCLUSION

The increased numbers of platelet-derived MPs in severe septic patients emphasize the possible contribution of the hemostasis system in the development of sepsis-related renal impairments.

Protecting the peritoneal membrane: factors beyond peritoneal dialysis solutions

Functional deterioration of the peritoneal membrane in patients on peritoneal dialysis has been described as being the result of a combination of neoangiogenesis and fibrosis. Glucose, glucose degradation products, and the unphysiological pH of the dialysate solution contribute to these changes. Although newer solutions clearly perform better in terms of their biocompatibility in an in vitro setting and in animal models, the benefit of such solutions over older solutions in the clinical setting is so far unproven. The difficulties in showing a benefit of the newer, more biocompatible solutions in the clinical setting can be explained by the fact that other factors also affect the properties of the peritoneal membrane. These factors are often neglected in clinical studies, which results in unnoticed differences in case-mix and blurs the potential impact of the novel solutions. However, many of these factors are modifiable, and attention should be paid to them in clinical practice to maintain the integrity of the peritoneal membrane. This Review focuses on factors that potentially influence the integrity of the peritoneal membrane, other than those associated with the peritoneal dialysis fluid itself.

Nicotinic acetylcholine receptor agonists attenuate septic acute kidney injury in mice by suppressing inflammation and proteasome activity

Sepsis is one of the leading causes of acute kidney injury (AKI). Septic patients who develop acute kidney injury (AKI) are at increased risk of death. To date there is no effective treatment for AKI or septic AKI. Based on their anti-inflammatory properties, we examined the effects of nicotinic acetylcholine receptor agonists on renal damage using a mouse model of lipopolysaccharide (LPS)-induced AKI where localized LPS promotes inflammation-mediated kidney damage. Administration of nicotine (1 mg/kg) or GTS-21 (4 mg/kg) significantly abrogated renal leukocyte infiltration (by 40%) and attenuated kidney injury. These renoprotective effects were accompanied by reduced systemic and localized kidney inflammation during LPS-induced AKI. Consistent with these observations, nicotinic agonist treatment significantly decreased renal IκBα degradation and NFκB activation during LPS-induced AKI. Treatment of human kidney cells with nicotinic agonists, an NFκB inhibitor (Bay11), or a proteasome inhibitor (MG132) effectively inhibited their inflammatory responses following stimulation with LPS or TNFα. Renal proteasome activity, a major regulator of NFκB-mediated inflammation, was enhanced by approximately 50% during LPS-induced AKI and elevated proteasome activity was significantly blunted by nicotinic agonist administration in vivo. Taken together, our results identify enhanced renal proteasome activity during LPS-induced AKI and the suppression of both proteasome activity and inflammation by nicotinic agonists to attenuate LPS-induced kidney injury.

Alkaline phosphatase for treatment of sepsis-induced acute kidney injury: a prospective randomized double-blind placebo-controlled trial

Introduction

To evaluate whether alkaline phosphatase (AP) treatment improves renal function in sepsis-induced acute kidney injury (AKI), a prospective, double-blind, randomized, placebo-controlled study in critically ill patients with severe sepsis or septic shock with evidence of AKI was performed.

Methods

Thirty-six adult patients with severe sepsis or septic shock according to Systemic Inflammatory Response Syndrome criteria and renal injury defined according to the AKI Network criteria were included. Dialysis intervention was standardized according to Acute Dialysis Quality Initiative consensus. Intravenous infusion of alkaline phosphatase (bolus injection of 67.5 U/kg body weight followed by continuous infusion of 132.5 U/kg/24 h for 48 hours, or placebo) starting within 48 hours of AKI onset and followed up to 28 days post-treatment. The primary outcome variable was progress in renal function variables (endogenous creatinine clearance, requirement and duration of renal replacement therapy, RRT) after 28 days. The secondary outcome variables included changes in circulating inflammatory mediators, urinary excretion of biomarkers of tubular injury, and safety.

Results

There was a significant (P = 0.02) difference in favor of AP treatment relative to controls for the primary outcome variable. Individual renal parameters showed that endogenous creatinine clearance (baseline to Day 28) was significantly higher in the treated group relative to placebo (from 50 ± 27 to 108 ± 73 mL/minute (mean ± SEM) for the AP group; and from 40 ± 37 to 65 ± 30 mL/minute for placebo; P = 0.01). Reductions in RRT requirement and duration did not reach significance. The results in renal parameters were supported by significantly more pronounced reductions in the systemic markers C-reactive protein, Interleukin-6, LPS-binding protein and in the urinary excretion of Kidney Injury Molecule-1 and Interleukin-18 in AP-treated patients relative to placebo. The Drug Safety Monitoring Board did not raise any issues throughout the trial.

Conclusions

The improvements in renal function suggest alkaline phosphatase is a promising new treatment for patients with severe sepsis or septic shock with AKI.

Trial Registration

www.clinicaltrials.gov: NCTNCT00511186

Glutamine administration ameliorates sepsis-induced kidney injury by downregulating the high-mobility group box protein-1-mediated pathway in mice

Acute kidney injury (AKI) is a severe complication of sepsis. High-mobility group box (HMGB)-1 was implicated as a late mediator of lethal systemic inflammation in sepsis. Since glutamine (GLN) was shown to have anti-inflammatory and antioxidant properties, we hypothesized that GLN administration may downregulate an HMGB-1-mediated pathway and thus ameliorate sepsis-induced AKI. Mice were randomly assigned to a normal group (NC), a septic saline group (SS), or a septic GLN group (SG). Sepsis was induced by cecal ligation and puncture (CLP). The SS group was injected with saline, and the SG group was given 0.75 g GLN/kg body wt once via a tail vein 1 h after CLP. Mice were killed 2, 6, and 24 h after CLP, and blood and kidneys of the animals were harvested for further analysis. The results showed that sepsis resulted in higher mRNA and/or protein expressions of kidney HMGB-1, toll-like receptor (TLR) 4, myeloid differentiation primary-response protein (MyD) 88, and receptor of advanced glycation end products (RAGE) compared with normal mice. Septic mice with GLN administration exhibited decreased HMGB-1, TLR4, RAGE, and phosphorylated NF-κB p65 protein expressions and reduced nitrotyrosine levels in kidney tissues. The histological findings showed that damage to the kidneys was less severe, and survival improved in the SG group. These results indicated that a single dose of GLN administered after the initiation of sepsis plays a prophylactic role in downregulating the expressions of HMGB-1-related mediators and decreasing oxidative stress in the kidneys, which may consequently have ameliorated AKI induced by sepsis.

Hepatorenal syndrome in the intensive care unit

Hepatorenal syndrome (HRS) is a functional form of acute kidney injury (AKI) associated with advanced liver cirrhosis or fulminant hepatic failure. Various new concepts have emerged since the initial diagnostic criteria and definition of HRS was initially published. These include better understanding of the pathophysiological mechanisms involved in HRS, identification of bacterial infection (especially spontaneous bacterial peritonitis) as the most important HRS-precipitating event, recognition that insufficient cardiac output plays a role in the occurrence of HRS, and evidence that renal failure reverses with pharmacotherapy. Patients with HRS are often critically ill and, by definition, have multiorgan failure. The purpose of this review is to provide an update on novel advances in HRS, with emphasis on the different aspects of management of these patients in the intensive care unit.

The association of receptor of advanced glycated end products and inflammatory mediators contributes to endothelial dysfunction in a prospective study of acute kidney injury patients with sepsis

The pathogenesis of acute kidney injury (AKI) occurring due to sepsis is incompletely understood. Endothelial activation, defined as up-regulation of adhesion molecules by proinflammatory cytokines, may be central to the development of sepsis-induced AKI. Our aim was to determine levels of circulating adhesion molecules endothelial (E)-selectin, intercellular adhesion molecule (ICAM), and vascular cell adhesion molecule (VCAM), inflammatory mediators; tumor necrosis factor-α (TNF-α) and transforming growth factor-β (TGF-β), vasoactive mediators; endothelin-1 (ET-1) and nitric oxide (NO), soluble receptor for advanced glycated end products (sRAGE) and serum fetuin-A in septic AKI patients before and after antibiotic therapy. Nineteen AKI patients with sepsis and fifteen healthy controls were enrolled in this prospective study. Results revealed that 12 weeks of therapy caused amelioration of endothelial and inflammatory injuries as well as renal function markers. Moreover, the positive correlations between levels of RAGE and E-selectin (r=0.88), ET-1 (r=0.90), and TNF-α (r=0.94) and negative with NO (r=-0.75-0.95) suggest that possible interaction of RAGE and inflammation may contribute to endothelial dysfunction in septic AKI patients.

Encapsulating peritoneal sclerosis: the state of affairs

Encapsulating peritoneal sclerosis (EPS) is a severe complication of long-term peritoneal dialysis (PD) with a 50% mortality rate. EPS is characterized by progressive and excessive fibrotic thickening of the peritoneum, leading to encapsulation of the bowels and intestinal obstruction. At present, EPS cannot be detected with certainty during its early stages; however, a progressive loss of ultrafiltration capacity often precedes its development. Studies that attempted to elucidate the pathogenesis of EPS have shown that the duration of exposure to PD fluids is the most important risk factor for EPS, and that young age and possibly the effects of peritonitis are additional contributory factors. The pathophysiology of EPS is probably best described as a multiple-hit process with a central role for transforming growth factor β. A form of EPS that develops shortly after kidney transplantation has also been recognized as a distinct clinical entity, and may be a common form of EPS in countries with a high transplantation rate. Criteria have been developed to identify EPS by abdominal CT scan at the symptomatic stage, but further clinical research is needed to identify early EPS in asymptomatic patients, to clarify additional risk factors for EPS and to define optimal treatment strategies.

Angiogenesis in peritoneal dialysis

Long-term exposure to peritoneal dialysis fluid induces morphological alterations, including angiogenesis, leading to a loss of ultrafiltration (UF) capacity. We discuss the effect of different factors in peritoneal dialysis (PD) on angiogenesis. In addition, we describe the process of angiogenesis and the possible role of different cell types in the peritoneum upon PD contributing to new blood vessel formation. Furthermore, we review several interventions used in our rat PD exposure model to decrease angiogenesis in PD. Moreover, we show new data on the use of sunitinib to inhibit angiogenesis in this rat model. Although various interventions seem to be promising, well-randomised clinical trials showing absolute prevention of angiogenesis and UF failure are, yet, still missing. To make real progress in PD treatment, the aim should be to prevent angiogenesis as well as peritoneal fibrosis and PD-induced inflammation.

Selective iNOS inhibition for the treatment of sepsis-induced acute kidney injury

The incidence and mortality of sepsis and the associated development of acute kidney injury (AKI) remain high, despite intense research into potential treatments. Targeting the inflammatory response and/or sepsis-induced alterations in the (micro)circulation are two therapeutic strategies. Another approach could involve modulating the downstream mechanisms that are responsible for organ system dysfunction. Activation of inducible nitric oxide (NO) synthase (iNOS) during sepsis leads to elevated NO levels that influence renal hemodynamics and cause peroxynitrite-related tubular injury through the local generation of reactive nitrogen species. In many organs iNOS is not constitutively expressed; however, it is constitutively expressed in the kidney and, in humans, a relationship between the upregulation of renal iNOS and proximal tubular injury during systemic inflammation has been demonstrated. For these reasons, the selective inhibition of renal iNOS might have important implications for the treatment of sepsis-induced AKI. Various animal studies have demonstrated that selective iNOS inhibition-in contrast to nonselective NOS inhibition-attenuates sepsis-induced renal dysfunction and improves survival, a finding that warrants investigation in clinical trials. In this Review, the selective inhibition of iNOS as a potential novel treatment for sepsis-induced AKI is discussed.

Renal replacement therapy in the liver transplant candidate

Since the implementation of the model of end-stage liver disease score to prioritize patients for orthotopic liver transplantation (OLT), the number of liver transplant candidates with renal failure and on renal replacement therapy (RRT) has dramatically increased. This review is intended to discuss the indications and implications of RRT initiation, the different RRT modalities, and special problems encountered with RRT in OLT candidates.

Production of endothelin-1 and reduced blood flow in the rat kidney during lung-injurious mechanical ventilation

INTRODUCTION

The mechanisms by which mechanical ventilation (MV) can injure remote organs, such as the kidney, remain poorly understood. We hypothesized that upregulation of systemic inflammation, as reflected by plasma interleukin-6 (IL-6) levels, in response to a lung-injurious ventilatory strategy, ultimately results in kidney dysfunction mediated by local endothelin-1 (ET-1) production and renal vasoconstriction.

METHODS

Healthy, male Wistar rats were randomized to 1 of 2 MV settings (n=9 per group) and ventilated for 4 h. One group had a lung-protective setting using peak inspiratory pressure of 14 cm H2O and a positive end-expiratory pressure of 5 cm H2O; the other had a lung-injurious strategy using a peak inspiratory pressure of 20 cm H2O and positive end-expiratory pressure of 2 cm H2O. Nine randomly assigned rats served as nonventilated controls. We measured venous and arterial blood pressure and cardiac output (thermodilution method), renal blood flow (RBF) using fluorescent microspheres, and calculated creatinine clearance, urine flow, and fractional sodium excretion. Histological lung damage was assessed using hematoxylin-eosin staining. Renal ET-1 and plasma ET-1 and IL-6 concentrations were measured using enzyme-linked immunosorbent assays.

RESULTS

Lung injury scores were higher after lung-injurious MV than after lung-protective ventilation or in sham controls. Lung-injurious MV resulted in significant production of renal ET-1 compared with the lung-protective and control groups. Simultaneously, RBF in the lung-injurious MV group was approximately 40% lower (P<0.05) than in the control group and 28% lower (P<0.05) than in the lung-protective group. Plasma ET-1 and IL-6 levels did not differ among the groups and systemic hemodynamics, such as cardiac output, were comparable. There was no effect on creatinine clearance, fractional sodium excretion, urine output, or kidney histology.

CONCLUSIONS

Lung-injurious MV for 4 h in healthy rats results in significant production of renal ET-1 and in decreased RBF, independent of IL-6. Decreased RBF has no observable effect on kidney function or histology.

Pathways of renal injury in systemic gram-negative sepsis

Acute renal failure is a grave complication of systemic gram-negative sepsis. The pathophysiological mechanisms of sepsis leading to kidney injury result in part from systemic inflammatory and haemodynamic alterations. These are triggered by the interaction of endotoxin with Toll-like receptor 4 (TLR4) on cells of the immune system. Recently, TLR4 and other co-effector molecules were identified on renal tubular and vascular cells. Furthermore, it was demonstrated that systemic endotoxin has direct access to renal sites where these receptors are expressed. Therefore, we review data in support of this novel pathway of renal injury in sepsis, whereby systemic endotoxin causes direct injury through interactions with local epithelial and endothelial TLR4.