[Regional citrate anticoagulation in renal replacement therapy in the intensive care station : Recommendations from the renal section of the DGIIN, ÖGIAIN and DIVI]

BACKGROUND

Regional citrate anticoagulation (RCA) in continuous renal replacement therapy can effectively anticoagulate dialysis circuits without having adverse effects on systemic heparin application. In particular, in continuous renal replacement therapy RCA is well established and represents a safe procedure with longer filter lifetimes and fewer bleeding complications.

OBJECTIVES

To provide guidance on the indications, advantages and disadvantages, and use of RCA, current recommendations from the renal section of the DGIIN (Deutschen Gesellschaft für Internistische Intensivmedizin und Notfallmedizin), ÖGIAIN (Österreichischen Gesellschaft für Internistische und Allgemeine Intensivmedizin und Notfallmedizin) and DIVI (Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin) are stated.

MATERIALS AND METHODS

The recommendations in this paper are based on the current KDIGO (Kidney Disease: Improving Global Outcomes) guidelines, other published guidelines and protocols as well as the expert knowledge and clinical experience of the authors.

RESULTS

The use of commercially available machines with coupled pumps and integrated safety features, effective personal training and standardized protocols for clinical usage (SOP) is particularly important for the safe clinical use of RCA in renal replacement therapy. Contrary to previous recommendations, even liver failure or shock with lactic acidosis may no longer be an absolute contra-indication for RCA. However, these particular patients have to be carefully monitored for signs of citrate accumulation.

[Metabolic management and nutrition in critically ill patients with renal dysfunction : Recommendations from the renal section of the DGIIN, ÖGIAIN, and DIVI]

BACKGROUND

Intensive care patients with renal failure or insufficiency comprise a heterogeneous group of subjects with widely differing metabolic patterns and nutritional requirements. They include subjects with various stages of acute kidney injury (AKI), acute-on-chronic renal failure (A-CKD), without/with renal replacement therapy (RRT), chronic kidney disease (CKD), and subjects on regular hemodialysis or peritoneal dialysis therapy (HD/PD).

GOALS

Development of recommendations by the renal section of DGIIN (Deutsche Gesellschaft für Internistische Intensivmedizin und Notfallmedizin), ÖGIAIN (Österreichische Gesellschaft für Internistische und Allgemeine Intensivmedizin und Notfallmedizin) and DIVI (Deutsche Interdisziplinäre Vereinigung für Intensiv- und Notfallmedizin) for the metabolic management and the planning, indication, implementation, and monitoring of nutrition therapy in this heterogeneous group of patients.

MATERIALS AND METHODS

The recommendations are based on recent evidence and current recommendations of DGEM (Deutsche Gesellschaft für Ernährungsmedizin), ASPEN (American Society for Parenteral and Enteral Nutrition) and ESPEN (European Society for Clinical Nutrition and Metabolism) and also the KDGIO (Kidney Disease: Improving Global Outcomes) clinical practice guidelines for AKI and the expert knowledge and clinical experience of the authors.

RESULTS

Nutrition support in these patient groups is not fundamentally different from that in other disease states but must consider the multiple variations in metabolism and nutrient requirements. Nutrition therapy must be adapted to the stage of disease and especially, in those patients on RRT. Nutritional needs can differ widely between patients but also in the same patient during the course of the disease.

CONCLUSIONS

Thus, the patient with renal failure requires an individualized approach in nutrition support and because of the altered metabolism of many nutrients and intolerances for electrolytes and fluids, the nutrition support in patients with renal insufficiency requires close clinical and laboratory monitoring.

Side Effects of Hybrid Liver Support Therapy: TNF-α Liberation in Pigs, Associated with Extracorporeal Bioreactors

During acute liver failure, hybrid liver support therapy could serve as a bridge to liver transplantation. In this desired temporary use, immune competent cell responses, such as the production of cytokines, might be of limiting relevance. We have investigated the Tumor Necrosis Factor-α (TNF) liberation in two models using pigs, connected with an extracorporeal bioreactor with homologous hepatocytes: TNF liberation was measured in arterial plasma during a 4 day perfusion time in untreated animals, model (i), and during short term perfusion of hepatectomized pigs in model (ii). Animals four days after catheter implantation in model (i) had TNF values of < 5 pg/ml. After connecting the system without hepatocytes, TNF rose to 9.7 ± 2 within 120 min and rose further to 32.6 ± 6 pg/ml within 4 hours after filling the system with the homologous hepatocytes. After 24 hours of continuous perfusion and during four days of perfusion, the TNF levels were lowered to baseline levels. In model (ii), TNF rose to 220 ± 130 pg/ml within 180 min and decreased to 110 ± 10 pg/ml within six hours, whereas controls without hepatocytes showed mean levels with a maximum of 120 ± 20 pg/ml. In both models, there was no correlation between TNF levels and clinical abnormalities such as fever or shock symptoms. There is evidence for an activation of blood cells during experimental extracorporeal hybrid support. No typical side effects were, however, observed. Thus, TNF mediated extracorporeal cell activation does not appear to limit the application of homologous hybrid liver support therapy.

[Prevention of acute kidney injury in critically ill patients : Recommendations from the renal section of the DGIIN, ÖGIAIN and DIVI]

BACKGROUND

Acute kidney injury (AKI) has both high mortality and morbidity.

OBJECTIVES

To prevent the occurrence of AKI, current recommendations from the renal section of the DGIIN (Deutschen Gesellschaft für Internistische Intensivmedizin und Notfallmedizin), ÖGIAIN (Österreichischen Gesellschaft für Internistische und Allgemeine Intensivmedizin und Notfallmedizin) and DIVI (Deutschen Interdisziplinären Vereinigung für Intensiv- und Notfallmedizin) are stated.

MATERIALS AND METHODS

The recommendations stated in this paper are based on the current Kidney Disease Improving Global Outcomes (KDIGO) guidelines, the published statements of the "Working Group on Prevention, AKI section of the European Society of Intensive Care Medicine" and the expert knowledge and clinical experience of the authors.

RESULTS

Currently there are no approved clinically effective drugs for the prevention of AKI. Therefore the mainstay of prevention is the optimization of renal perfusion by improving the mean arterial pressure (>65 mm Hg, higher target may be considered in hypertensive patients). This can be done by vasopressors, preferably norepinephrine and achieving or maintaining euvolemia. Hyperhydration that can lead to AKI itself should be avoided. In patients with maintained diuresis this can be done by diuretics that are per se no preventive drug for AKI. Radiocontrast enhanced imaging should not be withheld from patients at risk for AKI; if indicated, however, the contrast media should be limited to the smallest possible volume.

Variables Associated with the Assessment of Systemic Tumor Necrosis Factor Alpha Levels during Hemodialysis

Conflicting results have been published concerning the systemic induction of the cytokine tumor necrosis factor alpha (TNFα) during hemodialysis (HD). We therefore evaluated in vitro TNFα production in whole blood as well as in vivo variability of TNFα levels in patients on long-term HD. Whole blood was incubated at room temperature (RT) with or without exogenously added endotoxin (ET), and plasma-TNFα was measured after 5, 30, 120, 240, and 960 min by specific enzyme immunoassay. Additionally, plasma-TNFα before and after 120 and 240 min HD was studied longitudinally once a week over a period of 4 weeks in 36 patients on Cuprophan® (CU, n=23) or polysulfone-F60 (PSu, n=13) HD. Mean plasma TNFα levels in vitro rose from (mean) 8 pg/ml after 5 min to 12 pg/ml (120′) and 32 pg/ml (960′) even without ET addition, and to 18 pg/ml (after 120′) and 88 pg/ml (after 960′) when 0.1 μg/ml ET were added. Pre-dialytic as well as intradialytic TNFα levels in patients showed high intra-individual variability. A substantial (> 100%) increase in plasma TNFα was observed during only 14 out of 84 treatments with CU and 20 out of 47 with PSu, however, the increase in TNFα was not statistically significant in either group. We conclude that the sampling procedure, if not carefully standardized, is a potential source of artifacts with regard to “systemic” TNFα levels. The high intra and inter-individual variability of plasma TNFα suggests that results of cross-sectional studies are questionable.

Leukotriene Release from Neutrophils of Patients on Hemodialysis with Cellulose Membranes

The role of cytokines in patients with chronic renal failure is currently under investigation. We therefore studied the release of leukotriene B4 (LTB4) from polymorphonuclear leukocytes (PMN) in stable dialysis patients treated with two different cellulose membranes, Cuprophan and Hemophan®, a modified cellulose with less complement activation. Six patients were treated for four weeks with Cuprophan then switched to Hemophan® for another four weeks. Before and after the last treatment of each period, PMN were separated from 20 ml heparinized blood by FICOLL density gradient centrifugation. Portions of 5x106 PMN were resuspended in Hanks' buffer and stimulated for 5 minutes with calcium ionophore A23187 (5 /μg/ml). LTB4 in cell supernatants was determined by specific radioimmunoassay. PMN from dialysis patients before HD released significantly (p<0.01) more LTB4 than healthy donors. No significant difference between pre- and post-dialysis values was observed with Cuprophan or Hemophan® dialyzers. Our data suggest that the acute effects of blood membrane interaction with either complement activating or non-activating dialyzers do not lead to changes in post-dialysis leukotriene metabolism, but leukotriene production is enhanced chronically in dialysis patients.

Uremic Toxicity: Present State of the Art

The uremic syndrome is a complex mixture of organ dysfunctions, which is attributed to the retention of a myriad of compounds that under normal condition are excreted by the healthy kidneys (uremic toxins). In the area of identification and characterization of uremic toxins and in the knowledge of their pathophysiologic importance, major steps forward have been made during recent years. The present article is a review of several of these steps, especially in the area of information about the compounds that could play a role in the development of cardiovascular complications. It is written by those members of the Uremic Toxins Group, which has been created by the European Society for Artificial Organs (ESAO). Each of the 16 authors has written a state of the art in his/her major area of interest.

Correlation between HSP-72 Expression and IL-8 Secretion in Human Mesothelial Cells

Background

Cytotoxicity of peritoneal dialysis fluid (PDF) and peritoneal inflammation are currently regarded as the two major culprits for chronic mesothelial injury and peritoneal membrane failure. In this study, we correlated induction of HSP-72, as a marker of the cellular stress response, to secretion of IL-8, as a marker for pro-inflammatory cytokines, in mesothelial cells upon sublethal PDF exposure.

Methods

Primary omental cell cultures of human mesothelial cells were subjected to sublethal PDF exposure times (CAPD2, Fresenius, Germany). At the end of a 24 hour recovery period, induction of HSP-72 in the cell homogenate and IL-8 secretion in the supernatant was assessed by immunodensitometry and ELISA, respectively.

Results

PDF exposure times from 15 min to 60 min resulted in progressively increased HSP-72 expression levels (267 vs 320 vs 419% of controls, p<0.05 vs controls) as well as increased IL-8 secretion (323 vs 528 vs 549% of controls, p<0.05 vs controls) with full cell viability (MTT unchanged to control). HSP-72 expression was statistically significantly correlated with IL-8 secretion. Conclusions: The significant correlation between HSP-72 expression and IL-8 secretion suggests that the regulation of pro-inflammatory pathways in mesothelial cells exposed to PDF may represent an integral part of their stress response. Future studies to investigate the cellular regulatory mechanism involved are warranted.

[New KDIGO guidelines on acute kidney injury. Practical recommendations]

The incidence of acute kidney injury (AKI) in critically ill patients is very high and is associated with an increased morbidity and mortality. In 2012 the Kidney Disease: Improving Global Outcome (KDIGO) guidelines were published in which evidence-based practical recommendations are given for the evaluation and management of patients with AKI. The first section of the KDIGO guidelines deals with the unification of earlier consensus definitions and staging criteria for AKI. The subsequent sections of the guidelines cover the prevention and treatment of AKI as well as the management of renal replacement therapy (RRT) in patients with AKI. In each section the existing evidence is discussed and a specific treatment recommendation is given. The guidelines appreciates that there is insufficient evidence for many of the recommendations. As a specific pharmacological therapy is missing, an early diagnosis, aggressive hemodynamic optimization, tight volume control, and avoidance of nephrotoxic drugs are the only interventions to prevent AKI. If renal replacement therapy is required different modalities are available to provide an effective therapy with a low rate of adverse effects.

[Treatment of acute renal failure in Germany: Analysis of current practice]

BACKGROUND AND OBJECTIVES

There are currently no reliable data on the differential use of renal replacement therapy (RRT) options for critically ill patients with acute renal failure in Germany.

PATIENTS AND METHODS

A questionnaire-based survey was delivered to 2265 German intensive care units. The questionnaire contained 19 questions regarding RRT.

RESULTS

A total of 423 German intensive care units participated in the survey. The offered modalities of RRT varied significantly: the smaller the facility, the fewer different RRT options were available. Intermittent dialysis procedures were available in only 35% of hospitals with up to 400 beds. In university hospitals, hemodynamically unstable patients were exclusively treated by continuous RRT, whereas in hospitals with up to 400 beds, intermittent RRT was also used. In addition, treatment practice was also dependent on the specialization of the treating physicians: Isolated acute renal failure was treated more often intermittently by nephrologists compared to anesthesiologists (79.7 vs. 43.3%). Nephrologists also used extracorporeal RRT more often in cardiorenal syndrome (54.3 vs. 35.8%), whereas anesthesiologists preferred them in sepsis (37.3 vs. 23.1%). The choice of anticoagulant varied as well: Hospitals with up to 400 beds offered regional citrate anticoagulation in only 50% compared to 90% of university hospitals.

CONCLUSIONS

Currently, RRT treatment in acute renal failure on German intensive care units seems to be dependent on the size, local structures, and education of the intensivists rather than patient needs. Our results demonstrate the necessity to establish cross-disciplinary standards for the treatment of acute renal failure in German intensive care units.

[Adsorption therapy in sepsis]

BACKGROUND

The activation of multiple pro- and anti-inflammatory mediators is a key feature in the pathophysiology of sepsis. Many of these mediators may directly contribute to organ dysfunction and determine disease severity. So far our ability to modulate these upregulated mediator pathways is very limited. Therefore the adsorption of such mediators via an extracorporeal circuit may be a beneficial intervention during sepsis.

OBJECTIVES

Recent technical innovations have made this intervention feasible. Both systems for exclusive mediator adsorption and for adsorption beside a conventional renal replacement therapy are now available. Some of the membranes can adsorb a broad range of mediators by rather unspecific binding, whereas others specifically adsorb endotoxin or mediators.

DISCUSSION

Whilst biochemical efficacy could be demonstrated by some of the systems, controlled and randomized studies demonstrating improved clinical endpoints are still lacking. Therefore the use of such therapies outside clinical studies cannot yet be recommended.

[Treatment of acute renal failure in Germany: a structural analysis]

INTRODUCTION

There are no reliable data on the structure and practice of the care of critically ill patients with acute renal failure in Germany.

METHODS

We carried out a detailed survey by sending a questionnaire to 2265 German Intensive Care Units. The questionnaire contained 19 questions regarding renal replacement therapy.

RESULTS

423 German intensive care units participated in the survey. Most of the ICUs are headed interdisciplinary (47%) or by anesthesiologists (30%), with significant differences depending on the size of the clinic, with primarily interdisciplinary management in smaller clinics. The offered type of renal replacement therapy varies significantly, the smaller the house the fewer methods are available. Thus, intermittent dialysis procedures are offered only in 35% of hospitals with up to 400 beds. The indication for the initiation of acute renal replacement therapy in intensive care is provided predominantly (53%) by an anesthesiologist. A nephrologist is only involved in 22% of all intensive care units. The indication is based primarily on a "clinical criteria", but these are poorly defined.

CONCLUSION

Our results demonstrate the need for cross-disciplinary standards for the treatment of acute renal failure in German intensive care units.

Comparison of icodextrin- and glucose-based peritoneal dialysis fluids in their acute and chronic effects on human peritoneal mesothelial cells

BACKGROUND

Icodextrin-based peritoneal dialysis fluids (PDFs) display several features that may potentially improve their biocompatibility compared to conventional glucose-containing solutions. So far, however, the studies assessing the biocompatibility profile of icodextrin toward human peritoneal mesothelial cells (HPMC) has produced mixed results. The present study was performed to examine the acute and chronic impact of icodextrin on HPMC in vitro in comparison with standard glucose-based PDF.

METHODS

Omentum-derived HPMC were either acutely pre-exposed to or incubated chronically (for up to 10 days) in the presence of icodextrin-PDF. Parallel cultures were treated with conventional PDFs containing either 1.5% or 4.25% glucose. All fluids were tested at neutral pH. HPMC were assessed for viability, proliferation, IL-6 secretion and generation of reactive oxygen species (ROS).

RESULTS

Incubation in the presence of icodextrin-PDF significantly reduced HPMC proliferation in a manner similar to that of 1.5% glucose-PDF. In addition, exposure to icodextrin-PDF impaired viability and IL-6 release from HPMC. This effect occurred both after the short pre-treatment with neat icodextrin-PDF for 1-4 hours and after prolonged incubation (up to 10 days) in media supplemented with icodextrin-PDF (1:1). The dysfunction of icodextrin-treated HPMC was of the magnitude that was between the effects exerted by 1.5%- and 4.25%-glucose PDF. Furthermore, exposure of HPMC to icodextrin-PDF induced a dose-dependent increase in ROS generation which was comparable to that produced by 1.5%-glucose PDF.

CONCLUSION

Exposure to icodextrin-PDF may impair viability and function of HPMC. The detrimental effects of icodextrin-PDF are at least as serious as those produced by conventional heat-sterilized low glucose-based PDF.

PD and loss of peritoneal function

During long-term treatment with peritoneal dialysis both peritoneal membrane structure and function undergo significant changes that not only correlate with the time under treatment, but also with the frequency and severity of infections. In addition, peritoneal dialysis fluid bio-incompatibility may constitute a hazard for the longevity of the peritoneum as the dialysis membrane. In particular, the presence of glucose degradation products may lead to impaired peritoneal cell function as well as to increased protein glycation and peritoneal AGE deposition. Results from recent prospective randomised studies suggest that treatment with new GDP-depleted PD fluids may lead to a significant improvement of clinical outcomes in PD patients.

Role of mesothelial cell-derived granulocyte colony-stimulating factor in interleukin-17-induced neutrophil accumulation in the peritoneum

Recent studies suggest that peritoneal CD4(+) T lymphocytes may control recruitment of polymorphonuclear leukocytes (PMN) during peritonitis by an interleukin-17 (IL-17)-dependent mechanism. IL-17 and granulocyte colony-stimulating factor (G-CSF) have been proposed to form an axis that regulates PMN transmigration. Here we report on the role of G-CSF released by human peritoneal mesothelial cells (HPMCs) in IL-17A-mediated peritoneal PMN accumulation. In vitro exposure of HPMCs to IL-17A resulted in a time- and dose-dependent release of G-CSF. This effect was related to the induction of G-CSF mRNA and mediated through the nuclear factor-kappaB (NF-kappaB) pathway. The novel observation was that IL-17A-stimulated NF-kappaB activation in HPMCs followed a biphasic profile, with an early induction (45 min), followed by the return to basal levels (90 min), and a delayed induction (3 h). Tumor necrosis factor alpha synergistically amplified IL-17A-induced G-CSF production by enhanced NF-kappaB activation and through stabilization of G-CSF mRNA. Intraperitoneal (i.p.) administration of IL-17A in Balb/c mice resulted in increased local levels of G-CSF and selective PMN accumulation. Administration of anti-G-CSF blocking antibody before IL-17A injection significantly reduced the IL-17A-triggered PMN infiltration. This effect occurred despite increased i.p. levels of PMN-specific chemokines KC and macrophage inflammatory protein-2 seen in animals treated with anti-G-CSF antibody. These data demonstrate that the mesothelium-derived G-CSF plays an important role in IL-17A-induced PMN recruitment into the peritoneum.

Interleukin-17: a mediator of inflammatory responses

Interleukin-17 (IL-17) is a prototype member of a new cytokine family with six species identified to date. IL-17 is secreted mainly by activated CD4(+) and CD8(+) T lymphocytes, while its receptor is distributed ubiquitously. IL-17 has been classified as a proinflammatory cytokine because of its ability to induce the expression of many mediators of inflammation, most strikingly those that are involved in the proliferation, maturation and chemotaxis of neutrophils. Increased levels of IL-17 have been associated with several conditions, including airway inflammation, rheumatoid arthritis, intraperitoneal abscesses and adhesions, inflammatory bowel disease, allograft rejection, psoriasis, cancer and multiple sclerosis. This review provides an overview of IL-17 activities, concentrating on those that lead to neutrophil recruitment.

Acute renal failure. Extracorporeal treatment strategies

The mortality for acute renal failure remains to be high (around 50-70%) despite manifold improvements in terms of techniques and equipment for renal replacement therapies as well as patient monitoring and intensive care support. At present, it is not clear if the method chosen for renal replacement therapy, i.e. intermittent hemodialysis or continuous hemofiltration, might impact significantly on the outcome of these patients. Whilst earlier retrospective studies suggested that CVVH might result in better survival and renal recovery in acute patients, recent prospective studies were unable to confirm these findings. These studies were, however, not evenly randomised in terms of severity of illness or too small to produce conclusive results. In clinical routine CVVH is typically chosen for treating patients with hemodynamic instability and volume overload. If one decides to perform CVVH, however, a filtrate volume of at least 35 ml/kg body weight and hour should be used as this was shown to be associated with better survival as compared to smaller filtrate volumes. A second controversy exists to date whether the choice of the dialyzer membrane might be of significant relevance for the outcome of patients with acute renal failure. Earlier studies indicated that the use of biocompatible membranes in these patients may result in improved patient survival and renal recovery. More recently, however, these results could not be confirmed by larger randomized, prospective clinical studies. Thus, the choice of the dialyzer membrane should be based on individual assessment rather than treatment bias.

Extracorporeal treatment strategy in acute renal failure

The mortality of acute renal failure remains high (around 50-70%) despite manifold improvements in terms of techniques and equipment for renal replacement therapies as well as patient monitoring and intensive care support. At present, it is not clear if the method chosen for renal replacement therapy, i.e. intermittent hemodialysis or continuous hemofiltration, might impact on the outcome of these patients. Whilst earlier retrospective studies suggested that CVVH might result in better survival and renal recovery in acute patients, recent prospective studies indicated that this may not be the case or, conversely, outcomes may be better with IHD. These studies were, however, not evenly randomised in terms of illness severity or were too small to produce conclusive results. In addition, a meta-analysis of 9 published prospective studies in 692 pts. indicated a similar mortality with CVVH vs. IHD. Some of the studies enrolled for this meta-analysis, however, suffered from methodological and/or randomisation problems, thus this important question remains to date unanswered. Typically, CVVH is chosen for treating patients with hemodynamic instability and volume overload. In such cases, however, CVVH should be performed with a filtrate volume of at least 35 ml/kg body weight per hour as this was shown to be associated with better survival as compared to smaller filtrate volumes. A second controversy exists to date whether the choice of the dialyzer membrane might be of relevance for the outcome of patients with acute renal failure. Earlier studies indicated that the use of biocompatible membranes in these patients may result in improved patient survival and renal recovery. More recently, however, similar studies could not confirm these results. Another meta-analysis of controlled prospective trials (671 patients in 7 separate studies) calculated a relative mortality risk of 1.01 for cuprophan vs. biocompatible membranes. Thus, the choice of the dialyzer membrane should be based on individual assessment rather than treatment bias.

Continuous flow peritoneal dialysis: solution formulation and biocompatibility

When peritoneal dialysis was introduced several years ago an important alternative dialysis therapy to hemodialysis was made available for the treatment of end-stage chronic disease. However, a continuous search for new developments and technologies is necessary to find the optimal peritoneal dialysis fluid (PDF) to preserve peritoneal membrane function as long as possible. Conventional PDFs are known to compromise the functional integrity of the peritoneal membrane as a consequence of their acidic pH in combination with their high lactate content, as well as the high concentrations of glucose and glucose degradation products (GDPs) present in currently used conventional solutions. Novel solutions such as bicarbonate-buffered PDF (at neutral pH) display improved in vitro biocompatibility as compared to conventional, acidic lactate-buffered PDF. Since these novel solutions are manufactured in dual-chambered bags they also contain fewer GDPs, thus further reducing their potential toxicity and protein glycation. Clinically the novel solutions reduce inflow pain and improve peritoneal membrane transport characteristics, ultrafiltration capacity, and effluent markers of peritoneal membrane integrity. The concept of continuous flow peritoneal dialysis (CFPD) is another approach to optimize PDF. The technique of CFPD not only enables the individualization of acid-base correction by variable concentrations of HCO3- but may also help to restore peritoneal cell functions by neutral pH, reduced glucose load, diminished GDP content, and reduced advanced glycation end product (AGE) formation, thereby potentially contributing to the improved preservation of peritoneal membrane function.

Fatal acute diclofenac-induced immune hemolytic anemia

We report the case of a 72-year-old woman who developed fatal immune hemolytic anemia with multisystem organ failure and shock caused by diclofenac-dependent red blood cell autoantibodies. The patient described dramatically illustrates the potential severity of this adverse reaction and emphasizes the need for increased awareness of this complication of drug therapy.

Innovative approaches to the preservation of the peritoneal membrane: from bench to bedside

The functional integrity of the peritoneal membrane is of critical importance for the long-term success of peritoneal dialysis therapy. In addition to water and solute transport properties, the function of the membrane encompasses complex interactions with immune cells, invading microorganisms, and dialysis fluid components. During chronic peritoneal dialysis, intraperitoneal homeostasis is threatened by the repeated exposure to an unphysiologic environment that is created by the instilled solutions. Whereas their acidic pH and hyperosmolality were shown to primarily induce alterations of acute cell function, long-term peritoneal function might be affected by the repeated exposure to high concentrations of glucose and glucose degradation products. In addition to their intrinsic toxicity, these might induce or accelerate glycation processes, such as formation and deposition of advanced glycation end products in the peritoneal membrane. Presently, a new generation of dual-chambered peritoneal dialysis solutions combining the advantages of neutral pH and reduced glucose degradation products content is being introduced into clinical practice. In addition to an improved in vitro biocompatibility profile, emerging clinical trials of these novel solutions indicate that they might also improve the host defense status, membrane transport characteristics, ultrafiltration capacity, and effluent markers of peritoneal membrane integrity, while being safe and effective in correcting uremic acidosis and providing relief of inflow pain. Overall, these findings suggest that these new dialysis solutions might constitute an important step toward better preservation of long-term peritoneal membrane function during peritoneal dialysis.

Glucose degradation products and the peritoneal mesothelium

Conventional heat-sterilized, glucose-based peritoneal dialysis (PD) fluids contain significant amounts of glucose degradation products (GDPs) such as aldehydes and dicarbonyl compounds (glyoxal, methylglyoxal). These GDPs have been shown to impair cell functions in various in vitro experimental models. In peritoneal mesothelial cells, GDPs dose-dependently inhibit cell proliferation and mediator synthesis. In addition, some GDPs potently promote generation of advanced glycation end-products (AGEs). Immunohistochemistry finds AGEs in the peritoneal membrane of chronic continuous ambulatory peritoneal dialysis (CAPD) patients, suggesting that peritoneal AGE accumulation may be involved in chronic peritoneal fibrosis. The formation of GDPs might be prevented by filter-sterilization of PD fluids. Another option is to separate the glucose and the buffer system in dual-chambered or multi-chambered containers. In these systems, the glucose is kept in a separate compartment at high concentration and very low pH-both conditions being known to minimize the degree of glucose decomposition during autoclaving. Initial experimental evidence suggests that these novel, multi-chambered fluids significantly improve in vitro biocompatibility; however, the clinical relevance of these results remains to be established in clinical trials.

First in vitro and in vivo experiences with Stay-Safe Balance, a pH-neutral solution in a dual-chambered bag

In addition to low pH and high osmolarity, glucose degradation products (GDPs) are considered to play a major role in the bioincompatibility of peritoneal dialysis fluids (PDFs). The formation of GDPs can be reduced by separating the glucose component of the solution (kept at very low pH) from the lactate component of the solution (kept at alkaline pH) during sterilization and storage. This development has been achieved by the use of a dual-chambered bag. Immediately before infusion, the seam between the two chambers is opened, and the contents are mixed. The result is a fluid with a more physiologic pH in the range 6.8 - 7.4. Concentrations of 3-deoxyglucosone (3-DG), methylglyoxal (MG), acetaldehyde (AA), and formaldehyde (FA) in Stay-Safe Balance (Fresenius Medical Care, Bad Homburg, Germany) were remarkably reduced when compared to conventional PD solution [conventional PDF (1.5% glucose): 172 micromol/L, 6 microLmol/L, 152 micromol/L, and 7 micromol/L respectively; Stay-Safe Balance (1.5% glucose): 42 micromolL, < 1 micromol/L, < 2 micromol/L, and < 3 micromol/L respectively; conventional PDF (4.25% glucose): 324 micromol/L, 10 micromol/L, 182 micromol/L, and 13 micromol/L respectively; Stay-Safe Balance (4.25% glucose): 60 micromol/L, < 1 micromol/L, < 2 micromol/L, and < 3 micromol/L respectively). Human peritoneal mesothelial cells (HPMCs) were exposed to a control solution, a conventional PDF [CAPD 2, 1.5% glucose (Fresenius Medical Care, Bad Homburg, Germany)], and Stay-Safe Balance, either in a co-incubation model (24-hour PDF exposure) or in a pre-incubation model (30-min PDF exposure), followed by 24-hour recovery in culture medium. Interleukin-1beta (IL-1beta)-stimulated (1 ng/mL) IL-6 secretion from HPMCs was assessed by ELISA. Exposure of HPMCs to conventional PDF resulted in a significant reduction in IL-6 release, which was fully restored following exposure to Stay-Safe Balance. In addition to the short-term investigations, long-term in vitro studies were also carried out. All fluids had near-neutral pH and were changed every second day. After 1, 3, 5, 7, 10, and 13 days of exposure, cell viability was assessed. Whereas exposure to conventional PDF resulted in a significant reduction in HPMC viability after just 3 - 5 days, no significant toxicity of filter-sterilized or dual-chambered fluid was observed for up to 13 days. An observational study with 9 patients suggested that the efficacy of Stay-Safe Balance is equivalent to that of conventional solution. However, even short-term treatment (8+/-1 weeks) with this more biocompatible solution seems to improve mesothelial cell mass as indicated by a rise in cancer antigen 125 (CA125) from a baseline of 47+/-37 U/min to 172+/-90 U/min. Our data indicate that Stay-Safe Balance may help to better preserve peritoneal membrane cell function. An ongoing European multicenter study is expected to confirm these results.

Synthesis of C-X-C and C-C chemokines by human peritoneal fibroblasts: induction by macrophage-derived cytokines

Leukocyte accumulation during peritonitis is believed to be controlled by chemotactic factors released by resident peritoneal macrophages or mesothelial cells. Recent data indicate, however, that in many tissues fibroblasts play a key role in mediating leukocyte recruitment. We have therefore examined human peritoneal fibroblasts (HPFBs) for the expression and regulation of C-X-C and C-C chemokines. Quiescent HPFBs secreted monocyte chemoattractant protein (MCP)-1 and interleukin (IL)-8 constitutively. This release could be dose-dependently augmented with the pro-inflammatory cytokines IL-1beta and tumor necrosis factor-alpha. Stimulated IL-8 production reached a plateau within 48 hours while MCP-1 continued to accumulate throughout 96 hours. Induction of IL-8 and MCP-1 synthesis by HPFBs was also triggered by peritoneal macrophage-conditioned medium. This effect was partly related to the presence of IL-1beta as demonstrated by IL-1 receptor antagonist inhibition. Pretreatment of HPFBs with actinomycin D or puromycin dose-dependently reduced cytokine-stimulated IL-8 and MCP-1 secretion, which suggested de novo chemokine synthesis. Indeed, exposure of HPFBs to IL-1beta and tumor necrosis factor-alpha produced a significant up-regulation of IL-8 and MCP-1 mRNA. This effect was associated with the rapid induction of nuclear factor-kappaB binding activity mediated through p65 and p50 subunits, and with a transient increase in the mRNA expression for RelB and inhibitory protein kappaB-alpha proteins. These data indicate that peritoneal fibroblasts are capable of generating large quantities of chemokines under a tight control of nuclear factor-kappaB/Rel transcription factors. Thus, peritoneal fibroblast-derived chemokines may contribute to the intraperitoneal recruitment of leukocytes during peritonitis.

Glucose degradation products and peritoneal membrane function

BACKGROUND

The bioincompatibility of peritoneal dialysis fluids (PDF) in current use has been partially attributed to the presence of glucose degradation products (GDPs), which are generated during heat sterilization of PDF. Several of the GDPs have been identified and we have recently demonstrated that these GDPs per se may impair the viability and function of human peritoneal mesothelial cells (HPMC) in vitro. It is also possible that GDP-related toxicity is further exacerbated by the milieu of PDF. We review the current literature on GDP and present the results of experiments comparing the impact of heat- and filter-sterilized PDF on the viability and function of HPMC.

METHODS

Peritoneal dialysis fluids with low (1.5%) and high (4.25%) glucose concentrations were laboratory prepared according to the standard formula and sterilized either by heat (H-PDF; 121 degrees C, 0.2 MPa, 20 minutes) or filtration (F-PDF; 0.2 microns). The buildup of GDP was confirmed by UV absorbance at 284 nm. Confluent HPMC monolayers were exposed to these solutions mixed 1:1 with standard M199 culture medium. After 24 hours, cell viability was assessed with the MTT assay, and interleukin-1beta-stimulated monocyte chemotactic protein-1 (MCP-1) release with specific immunoassay.

RESULTS

Exposure of HPMC to H-PDF resulted in a significant decrease in cell viability, with solutions containing 4.25% glucose being more toxic than 1.5% glucose-based PDF (27.4% +/- 3.4% and 53.4% +/- 11.0% of control values, respectively). In contrast, viability of HPMC exposed to F-PDF was not different from that of control cells. Moreover, treatment with H-PDF impaired the release of MCP-1 from HPMC to a significantly greater degree compared to F-PDF (17.4% and 24.9% difference for low and high glucose PDF, respectively).

CONCLUSIONS

Exposure of HPMC to H-PDF significantly impairs cell viability and the capacity for generating MCP-1 compared to F-PDF. This effect is likely to be mediated by GDPs present in H-PDF but not in F-PDF.

Nightly intermittent peritoneal dialysis: targets and prescriptions

Adequate peritoneal dialysis can be achieved in most ESRD patients, provided that the prescription is individualized according to body surface area, body weight, residual renal function, and peritoneal transport characteristics. NIPD is particularly indicated in patients with significant residual renal function or those with a high-transport peritoneal membrane (accounting for about 10% of the PD patient population). "Dry day" NIPD reduces small-solute clearance by at least 10%-15% and middle-molecule clearance by almost 50%. Thus, most NIPD patients without residual renal function are at risk of inadequate treatment. The target dose of NIPD should be a weekly Kt/V of at least 2.2 and a weekly total creatinine clearance of 66 L/1.73 m2. However, the periodic clinical evaluation of patients should have priority over the mere achievement of a numerical clearance target.

IL-17 stimulates intraperitoneal neutrophil infiltration through the release of GRO alpha chemokine from mesothelial cells

IL-17 is a newly discovered cytokine implicated in the regulation of hemopoiesis and inflammation. Because IL-17 production is restricted to activated T lymphocytes, the effects exerted by IL-17 may help one to understand the contribution of T cells to the inflammatory response. We investigated the role of IL-17 in leukocyte recruitment into the peritoneal cavity. Leukocyte infiltration in vivo was assessed in BALB/Cj mice. Effects of IL-17 on chemokine generation in vitro were examined in human peritoneal mesothelial cells (HPMC). Administration of IL-17 i.p. resulted in a selective recruitment of neutrophils into the peritoneum and increased levels of KC chemokine (murine homologue of human growth-related oncogene alpha (GROalpha). Pretreatment with anti-KC Ab significantly reduced the IL-17-driven neutrophil accumulation. Primary cultures of HPMC expressed IL-17 receptor mRNA. Exposure of HPMC to IL-17 led to a dose- and time-dependent induction of GROalpha mRNA and protein. Combination of IL-17 together with TNF-alpha resulted in an increased stability of GROalpha mRNA and synergistic release of GROalpha protein. Anti-IL-17 Ab blocked the effects of IL-17 in vitro and in vivo. IL-17 is capable of selectively recruiting neutrophils into the peritoneal cavity via the release of neutrophil-specific chemokines from the peritoneal mesothelium.

Patients' expressions of complaints as a predictor of the course of acute hepatitis A

OBJECTIVE

Physical complaints, emotional states, liver, and immune parameters were investigated as possible indicators of the course of hepatitis A.

METHODS

Forty-seven patients with hepatitis A were studied by means of the Giessen-Complaint-Inventory (GBB) and the Berlin Mood Questionnaire (BSF), as well as by taking into account their typical liver parameters and the following immune parameters: alphaInterferon (alphaIFN), soluble Interleukin 2 receptor (sIL-2R), Interleukin 6 (IL-6), Interleukin 1 receptor antagonist (IL-1Ra), and Immunoglobulin M or G (IgM, IgG). Two hundred twenty-nine medical students and a representative German sample (n = 1557, Braehler et al.) served as controls.

RESULTS

We found that the initial degree of change in permeability of the liver cells, complaints about abdominal symptoms, and extent of depressive mood were able to predict the length of hospital stay. Patients with the initial, more pronounced liver damage, as well as patients who articulated less subjective impairment proved to have a longer course of illness. Those patients who needed a significantly longer time for recovery report, at admission, very few complaints-fewer than even the normal population. We were not, however, able to demonstrate a significant difference in the investigated immune parameters.

CONCLUSION

A certain denial tendency seems to be harmful with respect to the recovery process and the immunological competence in the course of hepatitis A.

Administration of prostacyclin after liver transplantation: a placebo controlled randomized trial

The shortage of suitable organs for liver grafts is responsible for the use of marginal donors for liver transplantation (OLT). If these liver grafts function poorly initially after OLT, a supportive therapy is necessary. The purpose of this study was to evaluate the effects of prostacyclin (PGI2) on postoperative liver graft function after OLT. A total of 30 adult recipients of primary OLT were randomized to either receive PGI2 (4 ng/kg per min body weight, n = 15) or a placebo for 6 d. To evaluate regional splanchnic oxygenation a fiberoptic pulmonary-artery catheter was inserted into a hepatic vein and the difference between mixed venous oxygen content and hepatic venous oxygen content was determined (deltaO2). Measurements were performed directly after transplantation and at 6, 12, 24 and 48 h postoperatively. A significant correlation between deltaO2 and the level of transaminases (ALT/AST) was observed 24 and 48 h after transplantation (p < 0.05). PGI2 treatment induced a significant decrease in deltaO2 after 24 and 48 h after reperfusion (p < 0.05). Peak AST levels tended to be lower in the PGI2 treatment group (418 +/- 99 vs. 638 +/- 156 U/L, p < 0.1). These results suggest that administration of PGI2 after OLT improves hepatic-splanchnic oxygenation and may thereby reduce reperfusion injury after OLT.

Haemodialysis-membrane biocompatibility and mortality of patients with dialysis-dependent acute renal failure: a prospective randomised multicentre trial. International Multicentre Study Group

BACKGROUND

There is controversy as to whether haemodialysis-membrane biocompatibility (ie, the potential to activate complement and neutrophils) influences mortality of patients with acute renal failure. We did a prospective randomised multicentre trial in patients with dialysis-dependent acute renal failure treated with two different types of low-flux membrane.

METHODS

180 patients with acute renal failure were randomly assigned bioincompatible Cuprophan (n=90) or polymethyl-methacrylate (n=90) membranes. The main outcome was survival 14 days after the end of therapy (treatment success). Odds ratios for survival were calculated and the two groups were compared by Fisher's exact test. Analyses were based on patients treated according to protocol (76 Cuprophan, 84 polymethyl methacrylate).

FINDINGS

At the start of dialysis, the groups did not differ significantly in age, sex, severity of illness (as calculated by APACHE II scores), prevalence of oliguria, or biochemical measures of acute renal failure. 44 patients (58% [95% CI 46-69]) assigned Cuprophan membranes and 50 patients (60% [48-70]) assigned polymethyl-methacrylate membranes survived. The odds ratio for treatment failure on Cuprophan compared with polymethyl-methacrylate membranes was 1.07 (0.54-2.11; p=0.87). No difference between Cuprophan and polymethyl-methacrylate membranes was detected when the analysis was adjusted for age and APACHE II score. 18 patients in the Cuprophan group and 20 in the polymethyl-methacrylate group had clinical complications of therapy (mainly hypotension).

INTERPRETATION

There were no differences in outcome for patients with dialysis-dependent acute renal failure between those treated with Cuprophan membranes and those treated with polymethyl-methacrylate membranes.

The prevalence of incipient tubular dysfunction, but not of glomerular dysfunction, is increased in patients with diabetes onset in childhood

The study investigated the prevalence of incipient renal dysfunction in two cohorts with identical duration of type I diabetes but with childhood or adult onset of the disease. The pattern of glomerular (albumin, alb) and tubular (alpha(1)-microglobulin, alpha(1)-m, and N-acetyl-beta-D-glucosaminidase, NAG) urinary protein excretion was studied in 97 patients with diabetes onset before the age of 16 years and in 53 patients with manifestation of the disease after this age. Diabetes duration was comparable in both groups [9.0 years (1.5-40.0) versus 9.0 (1.0-34.0), p 30 microg/g creatinine), patients with diabetes onset in childhood showed significantly higher excretion of NAG compared to those with diabetes onset after the age of 16. The excretion of both tubular markers (alpha(1)-m and NAG) correlated significantly with HbA(1c)-values in both groups. In multiple regression analysis, tubular proteinuria (alpha(1)-m) and diabetes duration correlated significantly to microabuminuria (multiple R = 0.60, p < 0.001). These data suggest that there is no difference concerning the prevalence of incipient diabetic glomerulopathy between patients with an early or a late onset of diabetes. However, a more frequent impairment of tubular function was found in young patients with diabetes onset in childhood, which might be due to a non-optimal glycemic control in this population.

Local liberation of cytokines during liver preservation

In order to investigate locally produced mediators during the process of organ storage in liver transplantation, we collected the liver preservation solution effluent of 15 transplanted livers and compared it with serum samples taken preoperatively from donor and recipient, as well as 60 min after reperfusion. The mean ischemia time +/- SEM was 10 h 10 min +/- 53 min. Mean concentrations in University of Wisconsin preservation solution effluent were: interleukin-(IL-)1beta 154 +/- 77 pg/ml; IL-1 receptor antagonist (IL-1 ra) 1281 +/- 309 pg/ml; IL-6 412 +/- 90 pg/ml; and for tumor necrosis factor-(TNF-)alpha 74 +/- 21 pg/ml. Cytokine levels in the donors were lower than those detected in the effluent. All measured cytokines showed higher concentrations in the effluent compared to those of the recipient prior to the operation. With respect to a comparison of donor and recipient values, no correlation is evident. Likewise, the ischemic time does not correlate with effluent values. Further development of liver preservation concepts requires information about the state of the graft before reperfusion. Data on cytokine liberation may serve as a helpful tool for the further development of preservation concepts because they enable an estimation of cell activation during preservation.

Effect of peritoneal dialysis on peritoneal cell biology: peritoneal fibroblasts

Despite the fact that the characterization of human peritoneal fibroblast biology and function is, at present, only in its early stages, the evidence available to date clearly indicates that direct interactions of peritoneal macrophages and fibroblasts may significantly contribute to the production of chemotactic and pro-inflammatory factors within the peritoneal cavity. In vitro models studying human peritoneal fibroblasts in two-dimensional or three-dimensional culture systems will further contribute to our understanding of the regulatory processes involved in peritoneal inflammation and fibrosis. In addition, the development of novel peritoneal dialysis solutions will have not only to examine the effect of these solutions on immune cells and the peritoneal mesothelium, but also to take into consideration the potential impact on peritoneal fibroblast function.

Biocompatibility and buffers: effect of bicarbonate-buffered peritoneal dialysis fluids on peritoneal cell function

BACKGROUND

Conventional peritoneal dialysis fluids (PDF) have been shown to compromise the function of both leukocytes and human peritoneal mesothelial cells (HPMC). Various in vitro studies have identified the low initial pH in combination with high lactate content, as well as the hyperosmolality and high glucose concentration present in currently used solutions as the primary determinants of their bioincompatibility. Bicarbonate buffered PDF (at neutral pH) display improved in vitro biocompatibility as compared to conventional, lactate buffered PDF. However, little information is currently available regarding the potential impact of PDF on the function of human peritoneal fibroblasts (HPFB), the major cell population present in peritoneal interstitium.

METHODS

The current study compares the effect of bicarbonate and lactate buffered PDF in a model system of resting peritoneal mesothelial cells and fibroblasts cultured from human omentum. Interleukin-1 beta-stimulated IL-6 release from HPMC and HPFB was used as the cell functional parameter.

RESULTS

While short (30 min) pre-exposure to lactate buffered PDF significantly reduced the IL-1 beta-stimulated IL-6 release from HPMC during a subsequent recovery period (24 hr), a significant decrease in HPMC IL-6 secretion with bicarbonate buffered PDF was only observed after prolonged (> or = 60 min) exposure. In contrast, no significant IL-6 inhibition was detected with HPFB pre-exposed to PDF for up to 90 minutes. A significant suppression of HPFB IL-6 secretion was only observed in coincubation experiments (24 hr) with dilutions of both types of PDF.

CONCLUSIONS

These results indicate that (i) bicarbonate buffered PDF are less inhibitory to peritoneal cell function as compared to conventional, lactate buffered PDF; and (ii) HPFB may be more resistant than HPMC to bioincompatible PDF.

In vitro biocompatibility evaluation of a novel bicarbonate-buffered amino-acid solution for peritoneal dialysis

BACKGROUND

Conventional lactate-buffered peritoneal dialysis fluids containing glucose as the osmotic agent have been shown to compromise important peritoneal host defence functions. The current study employed an in vitro model using activated peripheral blood mononuclear leukocytes (PBMC) for the preclinical biocompatibility assessment of a novel bicarbonate-buffered peritoneal dialysis fluid containing 1.0% amino acids as the osmotic agent.

METHODS

PBMC (5 x 10(6)/ml) were pre-exposed (10-30 mm, 37 degrees C) to bicarbonate-buffered 1% amino-acid solution, bicarbonate- or lactate-buffered 1.5% glucose fluid, or control medium (RPMI). The cells were then washed and stimulated for 2 h at 37 degrees C in RPMI containing 100 ng/ml E.coli endotoxin from strain O55:B5. The cytokines IL-6 and TNF alpha in cell supernatants were assessed using specific enzyme immunoassays, cytokine mRNA expression by reverse transcription polymerase chain reaction.

RESULTS

Short, i.e. 10 min, exposure to conventional, lactate-buffered glucose fluid resulted in a significant and time-dependent inhibition of cytokine release and mRNA expression by activated PBMC, whereas the cytokine response was improved even following prolonged (up to 2 h) exposure to bicarbonate-buffered 1% amino-acid solution or bicarbonate-buffered 1.5% glucose fluid.

CONCLUSIONS

Our results suggest that very short, i.e. potentially clinically relevant, exposure to conventional dialysis fluid impairs the cytokine response by activated leukocytes. In this respect, the use of bicarbonate-buffered solutions containing 1.0% amino acids or 1.5% glucose may result in improved biocompatibility properties.

Inhibition of tumour necrosis factor production in endotoxin-stimulated human mononuclear leukocytes by the prostacyclin analogue iloprost: cellular mechanisms

The prostacyclin analogue iloprost has been shown to inhibit effectively TNF-alpha production in human peripheral blood mononuclear leukocytes (PBMC) stimulated with bacterial lipopolysaccharide (LPS). The current paper set out to analyse further the possible mechanisms involved in the regulation of TNF-alpha synthesis by iloprost. Healthy human PBMC were challenged with Escherichia coli LPS and assessed for TNF-alpha gene transcription, mRNA stability and protein secretion. Iloprost reduced both steady-state TNF-alpha mRNA expression and protein release as assessed by Northern blot analysis, polymerase chain reaction and enzyme immunoassay. This effect was related both to a reduction of TNF-alpha transcriptional activity (as evaluated by nuclear run-on transcription analysis) and a decrease in TNF-alpha mRNA stability (as assessed by serial Northern blot analysis of TNF-alpha mRNA content in PBMC blocked with actinomycin D). When collectively assessed, these data demonstrate that iloprost regulates TNF-alpha synthesis at both transcriptional and post-transcriptional level.

Systemic liberation of interleukin-8 in the perioperative phase of liver transplantation

Serum levels of interleukin-8 (IL-8) were investigated in the perioperative phase of liver transplantation (LTx) in order to help determine whether this cytokine might serve as a parameter for preservation injury. In a study of 45 patients undergoing LTx, systemic IL-8 was estimated at the end of the anhepatic phase, at 30, 60, and 120 min after reperfusion of the graft, and 24 h and 7 days after LTx. A maximum mean concentration of 665 +/- 135 pg/ml was seen 60 min after LTx. The minimum was found on the 1st postoperative day (POD 1): 328 +/- 33 pg/ml. Significant changes were found between 60 min and PODs 1 and 7, as well as between 120 min and POD 1. Differences in cold ischemia time were not found to be significant. We conclude that monitoring of systemic IL-8 levels is not useful in the development of new liver preservation concepts.