Peritoneal dialysis fluids

There have been significant advances in the understanding of peritoneal dialysis (PD) in the last 40 years, and uptake of PD as a modality of kidney replacement therapy is increasing worldwide. PD fluids, therefore, remains the lifeline for patients on this treatment. Developing these fluids to be efficacious in solute clearance and ultrafiltration, with minimal adverse consequences to peritoneal membrane health and systemic effects is a key requirement. Since the first PD fluid produced in 1959, modifications to PD fluids have been made. Nonetheless, the search for that ideal PD fluid remains elusive. Understanding the components of PD fluids is a key aspect of optimizing the successful delivery of PD, allowing for individualized PD prescription. Glucose remains an integral component of PD fluids; however, its deleterious effects continue to be the impetus for the search of an alternative osmotic agent, and icodextrin remains the main alternative. More biocompatible PD fluids have been developed and have shown benefits in preserving residual kidney function. However, high cost and reduced accessibility remain deterrents to its widespread clinical use in many countries. Large-scale clinical trials are necessary and very much awaited to improve the narrow spectrum of PD fluids available for clinical use.

Incremental peritoneal dialysis is a safe and feasible prescription in incident patients with preserved residual kidney function

BACKGROUND

Incremental peritoneal dialysis (PD) is recommended as a component of high-quality care by the international society for PD; however, its feasibility and clinical outcomes have not been widely reported. The aim of this study is to describe our experience with incremental PD.

METHODS

This was a retrospective cohort study of incident PD patients at Eastern Health between 2015 and 2019. Patients who stopped PD within 30 days were excluded. Incremental PD was defined in CAPD as using <8 L/day of exchange volume and in automated PD as dialysing without a last fill. Dialysis modality accorded with patient and physician preferences.

RESULTS

The 96 patients were included in this study; 54 with incremental PD. Compared to full-dose PD, incremental PD patients were more likely to be female, had less comorbid diabetes (28% vs. 52%) and higher residual kidney function (RKF) (Kt/V 2.0 ± 0.7 vs. 1.4 ± 0.7). Age, BMI and starting eGFR did not differ between groups. Incremental PD exposed patients to lower exchange volumes (4.4 ± 2.1 vs. 8.5 ± 1.1 L/day), glucose load (46 ± 41 g/day vs. 119 ± 46) and was associated with a longer peritonitis-free survival. PD technique survival, rates of peritonitis or hospitalization were comparable between groups. Predictors for longer incremental PD use included older age and higher starting eGFR.

CONCLUSIONS

Incremental PD is a feasible, goal-directed initial prescription in patients with RKF with comparable peritonitis rates and technique survival. Validation of this prescription in prospective studies is warranted.

Agents that Modulate Peritoneal Membrane Structure and Function

Extensive experience with chronic peritoneal dialysis has identified a series of functional and anatomical pathologic changes in the peritoneal membrane thought to be the result of repeated insults from bioincompatible solutions. Laboratory and clinical findings from recent investigations often conflict and are difficult to interpret due to variations in methodologies, animal models, study designs, and data analyses. The principal pathophysiologic mechanisms identified thus far are oxidative stress, inflammation, and their consequences. Many substances used to neutralize the action of these insults, prevent formation of toxic compounds, or directly alter solute and water transport to improve peritoneal membrane performance have been studied. We herein review the most promising of these substances or those that deserve attention because their use has contributed to better understanding of peritoneal pathophysiology. Most peritoneal solution additives have proved useless due to their toxicity and undesirable effects, ineffectiveness, or manufacturing limitations. A few substances deserve more attention, particularly those capable of restoring negatively charged membrane sites, those that somehow improve permselectivity, scavengers of oxidants, and advanced glycation end-product inhibitors and breakers. Recent publications on clinical experience with neutral pH, low glucose degradation product (GDP) peritoneal solutions, although few and preliminary, are most encouraging. The virtual elimination of GDPs in these novel solutions will probably preclude the need for GDP scavengers and inhibitors. Nonetheless, there is room for further significant improvement in solution biocompatibility and for compounds that may restore peritoneal function.

The effect of high glucose-based peritoneal dialysis fluids on thioredoxin-interacting protein expression in human peritoneal mesothelial cells

BACKGROUND

It has been demonstrated that thioredoxin-interacting protein (TXNIP) interacted with NACHT, LRR and PYD domains-containing protein 3 (NLRP3) and participated in the NLRP3 inflammasome activation. Our previous study has demonstrated that in human peritoneal mesothelial cells (HPMCs), exposure to high glucose-based peritoneal dialysis (PD) solutions induced mitochondrial reactive oxygen species (ROS) production, activation of NLRP3 inflammasome and IL-1β expression. This study aimed to investigate the effect of high glucose-based PD fluids on the TXNIP expression and the underlying mechanisms by which TXNIP-NLRP3 interaction mediates the inflammatory injury to HPMCs in high glucose-based PD fluids conditions.

METHODS

TXNIP gene and protein expression was detected by real-time polymerase chain reaction (RT-PCR) and immunoblot. Immunoprecipitation was used to evaluate the interaction between TRX1 and TXNIP, TXNIP and NLRP3. ROS production and IL-1β expression was examined by flow cytometry and immunoblot and enzyme-linked immunosorbent assay (ELISA) respectively.

RESULTS

It was identified that high glucose-based PD solutions enhance the level of TXNIP gene and protein in cultured HPMCs and a rat-based PD model. We also found that ROS generation induced by high glucose-based PD solutions disrupts the TRX1-TXNIP association, while promoting the binding of TXNIP to NLRP3 in HPMCs. Furthermore, the application of a ROS inhibitor (APDC) to HPMCs blocked the high glucose-based PD solution-induced TXNIP-NLRP3 binding, in addition to ROS production and IL-1β expression.

CONCLUSION

The results of the present study revealed a novel mechanism underlying high glucose-containing PD-mediated peritoneal inflammatory injury, supporting the attenuation of ROS generation as a potential therapeutic strategy to alleviate such pathology.

Complement Activation in Peritoneal Dialysis-Induced Arteriolopathy

Cardiovascular disease (CVD) is the leading cause of increased mortality in patients with CKD and is further aggravated by peritoneal dialysis (PD). Children are devoid of preexisting CVD and provide unique insight into specific uremia- and PD-induced pathomechanisms of CVD. We obtained peritoneal specimens from children with stage 5 CKD at time of PD catheter insertion (CKD5 group), children with established PD (PD group), and age-matched nonuremic controls (n=6/group). We microdissected omental arterioles from tissue layers not directly exposed to PD fluid and used adjacent sections of four arterioles per patient for transcriptomic and proteomic analyses. Findings were validated in omental and parietal arterioles from independent pediatric control (n=5), CKD5 (n=15), and PD (n=15) cohorts. Transcriptomic analysis revealed differential gene expression in control versus CKD5 arterioles and in CKD5 versus PD arterioles. Gene ontology analyses revealed activation of metabolic processes in CKD5 arterioles and of inflammatory, immunologic, and stress-response cascades in PD arterioles. PD arterioles exhibited particular upregulation of the complement system and respective regulatory pathways, with concordant findings at the proteomic level. In the validation cohorts, PD specimens had the highest abundance of omental and parietal arteriolar C1q, C3d, terminal complement complex, and phosphorylated SMAD2/3, a downstream effector of TGF-β Furthermore, in the PD parietal arterioles, C1q and terminal complement complex abundance correlated with the level of dialytic glucose exposure, abundance of phosphorylated SMAD2/3, and degree of vasculopathy. We conclude that PD fluids activate arteriolar complement and TGF-β signaling, which quantitatively correlate with the severity of arteriolar vasculopathy.

Is there such a thing as biocompatible peritoneal dialysis fluid?

Introduction of the so-called biocompatible peritoneal dialysis (PD) fluids was based on a large body of experimental evidence and various clinical trials suggesting important clinical benefits. Of these, until now, only preservation of residual renal function-likely due to lower glucose degradation product load and, in case of icodextrin, improved fluid and blood pressure control-have consistently been proven, whereas the impact on important clinical endpoints such as infectious complications, preservation of PD membrane transport function, and patient outcome, are still debated. In view of the high morbidity and mortality rates of PD patients, novel approaches are warranted and comprise the search for alternative osmotic agents and enrichment of PD fluids with specific pharmacologic agents, such as alanyl-glutamine, potentially counteracting local but also systemic sequelae of uremia and PD.

Risk factors for drainage-requiring ascites after refractory peritonitis in peritoneal dialysis patients

PURPOSE

Refractory peritonitis remains a thorny issue for patients with chronic peritoneal dialysis (PD). Shortly after catheter removal, some patients develop persistent peritoneal inflammation and ascites formation, which require percutaneous drainage for symptom relief. Our study aimed at finding the risk factors for this kind of event.

METHODS

A total of 47 PD patients complicated with refractory peritonitis who underwent catheter removal between January 2009 and December 2011 were enrolled in this study. Data were compared between patients with and without the development of symptomatic ascites requiring drainage during hospitalization.

RESULTS

Among the 47 refractory peritonitis patients, 15 patients developed symptomatic ascites that needed further drainage shortly after catheter removal during hospitalization. The following factors were associated with an increased risk: longer dialysis duration, higher peritoneal Kt/V urea, and a significant rise in serum C-reactive protein (CRP) level after catheter removal. These patients had a prolonged hospital stay (62 vs 21 days, P < 0.001) and a significantly higher risk of recurrent loculated ascites during subsequent 6 months of follow-up (33.3 vs 6.2 %, P = 0.022) compared with patients who did not develop ascites requiring drainage during hospitalization.

CONCLUSION

A significant portion of patients with refractory PD peritonitis experienced ascites requiring drainage shortly after catheter removal, which led to a prolonged hospitalization. Whether routine drain placement at the time of catheter removal for this high-risk group would be of benefit warrants further prospective studies.

The Association Between Glucose Exposure and the Risk of Peritonitis in Peritoneal Dialysis Patients

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BACKGROUND AND OBJECTIVE

Little or no clinical evidence is available on the association between glucose exposure and peritoneal host defense in peritoneal dialysis (PD) patients. The objective of the present study was to quantify the exposure to glucose during the first year on PD and investigate the association with subsequent peritonitis. ♦

METHODS

We analyzed prospectively collected demographic and peritonitis data from incident adult PD patients between 1990 and 2010. For the present study, we conducted a review of both in- and outpatient medical records of all patients to obtain their day-to-day dialysis schemes during the first year on PD. From these data, the average exposure to glucose was quantified. The exposure was stratified into low- and high-glucose groups based on the median, analyzed per standard deviation and in quartiles. Cox proportional hazard models were used to calculate crude and adjusted hazard ratios (HRs) and 95% confidence intervals for the association between glucose exposure and peritonitis. Adjustments were made for age, sex, primary kidney disease, diabetes mellitus, Davies comorbidity score and the treatment period. ♦

RESULTS

In total, 230 patients were included in the study of whom 151 (66%) experienced a first peritonitis episode. The median follow-up time was 2.6 years (interquartile range [IQR]: 1.9 - 3.8) in the low-glucose group and 3.1 (IQR: 2.1 - 4.2) in the high-glucose group. After adjustment for confounding factors, no association between high glucose exposure and the risk of peritonitis was found (HR: 0.81; 0.55 - 1.17). No association was present when glucose exposure was analyzed per standard deviation (SD) (HR: 0.98; 0.79 - 1.21) or patient quartiles were applied. No association was identified between glucose exposure and severe peritonitis, Staphylococcus aureus peritonitis, or a peritonitis episode that lasted more than 14 days. ♦

CONCLUSIONS

Exposure to glucose is not associated with an increased risk of peritonitis. The equilibrium between glycemic harm to peritoneal host defense and detrimental effects of glucose on invading microorganisms may determine the susceptibility to peritoneal infection.

Baseline serum interleukin-6 predicts cardiovascular events in incident peritoneal dialysis patients

BACKGROUND

The utility of local and systemic interleukin 6 (IL-6) as a prognostic marker in incident peritoneal dialysis (PD) patients remains to be fully defined. The present study aimed to explore the capacity of systemic IL-6 concentrations to predict cardiovascular events (CVEs) and mortality in PD patients, and to evaluate the influence of neutral-pH PD solutions low in glucose degradation products (GDPs) on systemic IL-6.

METHODS

The study included 175 incident participants from the balANZ trial with at least one stored serum sample. A composite CVE score was used as the primary clinical outcome measure. Multilevel linear regression and Poisson regression models were fitted to describe, respectively, the trend of serum IL-6 over time and its ability to predict composite CVE.

RESULTS

A significant increase in serum IL-6 from baseline to 24 months was observed in the study population (mean difference: 1.68 pg/mL; p = 0.006). The type of PD solution received by patients exerted no significant effect on serum IL-6 (p = 0.12). Composite CVE was significantly and independently associated with baseline serum IL-6 (incidence rate ratio per picogram per milliliter: 1.06; 95% confidence interval: 1.02 to 1.10; p = 0.003).

CONCLUSIONS

Baseline serum IL-6 was a significant independent predictor of composite CVE. Serum IL-6 concentrations increased with increasing PD duration and were not significantly modified with the use of biocompatible fluid over the study period. The present study is the first to link systemic IL-6 concentrations with CVE outcomes in incident PD patients.

Biocompatible dialysis fluids for peritoneal dialysis

BACKGROUND

The longevity of peritoneal dialysis (PD) is limited by high rates of technique failure, some of which stem from peritoneal membrane injury. 'Biocompatible' PD solutions have been developed to reduce damage to the peritoneal membrane.

OBJECTIVES

This review aimed to look at the benefits and harms of biocompatible PD solutions in comparison to standard PD solutions in patients receiving PD.

SEARCH METHODS

We searched the Cochrane Renal Group's Specialised Register (28 February 2013), through contact with the Trials Search Co-ordinator using search terms relevant to this review. Studies contained in the Specialised Register are identified through search strategies specifically designed for CENTRAL, MEDLINE and EMBASE, and handsearching conference proceedings.

SELECTION CRITERIA

All randomised controlled trials (RCTs) and quasi-RCTs in adults and children comparing the effects of biocompatible PD solutions (neutral pH, lactate-buffered, low glucose degradation product (GDP); neutral pH, bicarbonate (± lactate)-buffered, low GDP; glucose polymer (icodextrin)) in PD were included. Studies of amino acid-based PD solutions were excluded.

DATA COLLECTION AND ANALYSIS

Two authors extracted data on study quality and outcomes (including adverse effects). The authors contacted investigators to obtain missing information. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for categorical variables, and mean difference (MD) or standardised mean difference (SMD) and 95% CI for continuous variables.

MAIN RESULTS

Thirty-six eligible studies (2719 patients) were identified: Neutral pH, lactate-buffered/bicarbonate (± lactate)-buffered, low GDP PD solution (24); icodextrin (12). Allocation methods and concealment were generally incompletely reported, and adequate in only ten studies (27.8%). Patients lost to follow-up ranged from 0% to 83.4%. Neutral pH, low GDP versus conventional glucose PD solutionBased on generally sub-optimal quality evidence, the use of neutral pH, low GDP PD solutions was associated with larger urine volumes at the end of the studies, up to three years of therapy duration (7 studies, 520 patients: MD 126.39 mL/d, 95% CI 26.73 to 226.05). Improved preservation of residual renal function was evident in studies with greater than 12 month follow-up (6 studies, 360 patients: SMD 0.31, 95% CI 0.10 to 0.52). There was no significant effect on peritonitis, technique failure or adverse events with the use of neutral pH, low GDP PD solutions. Glucose polymer (icodextrin) versus conventional glucose PD solutionThere was a significant reduction in episodes of uncontrolled fluid overload (2 studies, 100 patients: RR 0.30, 95% CI 0.15 to 0.59) and improvement in peritoneal ultrafiltration (4 studies, 102 patients, MD 448.54 mL/d, 95% CI 289.28 to 607.80) without compromising residual renal function (4 studies, 114 patients: SMD 0.12, 95% CI -0.26 to 0.49) or urine output (3 studies, 69 patients: MD -88.88 mL/d, 95% CI -356.88 to 179.12) with icodextrin use. A comparable incidence of adverse events with the icodextrin (four studies) was reported.

AUTHORS' CONCLUSIONS

Based on generally sub-optimal quality studies, use of neutral pH, low GDP PD solution led to greater urine output and higher residual renal function after use exceeded 12 months. Icodextrin prescription improved peritoneal ultrafiltration and mitigated uncontrolled fluid overload. There were no significant effects on peritonitis, technique survival, patient survival or harms identified with their use. Based on the best available evidence, the use of these 'biocompatible' PD solutions resulted in clinically relevant benefits without added risks of harm.

The impact of neutral-pH peritoneal dialysates with reduced glucose degradation products on clinical outcomes in peritoneal dialysis patients

Neutral-pH peritoneal dialysates, with reduced glucose degradation products (GDPs), have been developed to reduce peritoneal membrane damage. Here our review evaluated the impact of these solutions on clinical outcomes using data from The Cochrane CENTRAL Registry, MEDLINE, Embase, and reference lists for randomized trials of biocompatible solutions. Summary estimates of effect were obtained using a random-effects model of 20 eligible trials encompassing 1383 patients. The quality of studies was generally poor, such that 13 studies had greater than a 20% loss to follow-up and only 3 trials reported adequate concealment of allocation. Use of neutral-pH dialysates with reduced GDPs resulted in larger urine volumes (7 trials; 520 patients; mean difference 126 ml/day, 95% CI 27-226), improved residual renal function after 12 months (6 trials; 360 patients; standardized mean difference 0.31, 95% confidence interval 0.10-0.52), and a trend to reduced inflow pain (1 trial; 58 patients; relative risk 0.51, 95% CI 0.24-1.08). However, there was no significant effect on body weight, hospitalization, peritoneal solute transport rate, peritoneal small-solute clearance, peritonitis, technique failure, patient survival, or adverse events. No significant harms were identified. Thus, based on generally poor quality trials, the use of neutral-pH peritoneal dialysates with reduced GDPs resulted in greater urine volumes and residual renal function after 12 months, but without other clinical benefits. Larger, better-quality studies are needed for accurate evaluation of the impact of these newer dialysates on patient-level hard outcomes.

Biocompatible peritoneal dialysis fluids: clinical outcomes

Peritoneal dialysis (PD) is a preferred home dialysis modality and has a number of added advantages including improved initial patient survival and cost effectiveness over haemodialysis. Despite these benefits, uptake of PD remains relatively low, especially in developed countries. Wider implementation of PD is compromised by higher technique failure from infections (e.g., PD peritonitis) and ultrafiltration failure. These are inevitable consequences of peritoneal injury, which is thought to result primarily from continuous exposure to PD fluids that are characterised by their "unphysiologic" composition. In order to overcome these barriers, a number of more biocompatible PD fluids, with neutral pH, low glucose degradation product content, and bicarbonate buffer have been manufactured over the past two decades. Several preclinical studies have demonstrated their benefit in terms of improvement in host cell defence, peritoneal membrane integrity, and cytokine profile. This paper aims to review randomised controlled trials assessing the use of biocompatible PD fluids and their effect on clinical outcomes.

Pathophysiological changes to the peritoneal membrane during PD-related peritonitis: the role of mesothelial cells

The success of peritoneal dialysis (PD) is dependent on the structural and functional integrity of the peritoneal membrane. The mesothelium lines the peritoneal membrane and is the first line of defense against chemical and/or bacterial insult. Peritonitis remains a major complication of PD and is a predominant cause of technique failure, morbidity and mortality amongst PD patients. With appropriate antibiotic treatment, peritonitis resolves without further complications, but in some PD patients excessive peritoneal inflammatory responses lead to mesothelial cell exfoliation and thickening of the submesothelium, resulting in peritoneal fibrosis and sclerosis. The detrimental changes in the peritoneal membrane structure and function correlate with the number and severity of peritonitis episodes and the need for catheter removal. There is evidence that despite clinical resolution of peritonitis, increased levels of inflammatory and fibrotic mediators may persist in the peritoneal cavity, signifying persistent injury to the mesothelial cells. This review will describe the structural and functional changes that occur in the peritoneal membrane during peritonitis and how mesothelial cells contribute to these changes and respond to infection. The latter part of the review discusses the potential of mesothelial cell transplantation and genetic manipulation in the preservation of the peritoneal membrane.

Solutions for peritoneal dialysis in children: recommendations by the European Pediatric Dialysis Working Group

The purpose of this article is to provide recommendations on the choice of peritoneal dialysis (PD) fluids in children by the European Pediatric Dialysis Working Group. The literature on experimental and clinical studies with PD solutions in children and adults was analyzed together with consensus discussions within the group. A grading was performed based on the international KDIGO nomenclature and methods. The lowest glucose concentration possible should be used. Icodextrin may be applied once daily during the long dwell, in particular in children with insufficient ultrafiltration. Infants on PD are at risk of ultrafiltration-associated sodium depletion, while anuric adolescents may have water and salt overload. Hence, the sodium chloride balance needs to be closely monitored. In growing children, the calcium balance should be positive and dialysate calcium adapted according to individual needs. Limited clinical experience with amino acid-based PD fluids in children suggests good tolerability. The anabolic effect, however, is small; adequate enteral nutrition is preferred. CPD fluids with reduced glucose degradation products (GDP) content reduce local and systemic toxicity and should be preferred whenever possible. Correction of metabolic acidosis is superior with pH neutral bicarbonate-based fluids compared with single-chamber, acidic, lactate-based solutions. Prospective comparisons of low GDP solutions with different buffer compositions are still few, and firm recommendations cannot yet be given, except when hepatic lactate metabolism is severely compromised.

Peritoneal dialysis in infants: the experience of the Italian Registry of Paediatric Chronic Dialysis

BACKGROUND

Although chronic peritoneal dialysis (CPD) is considered the replacement therapy of choice for infants with end-stage renal failure, many questions persist about treatment risks and outcomes.

METHODS

We present data on 84 infants who started CPD at <1 year of age; these patients represent 12% of the total population of the Italian Registry of Paediatric Chronic Dialysis. We analysed patient records from all children consecutively treated with CPD between 1995 and 2007 in Italy. Growth data analysis was performed only in infants with complete auxological parameters at 0, 6 and 12 months of follow-up.

RESULTS

Median age at the start of CPD was 6.9 months, weight was 6.1 kg and length 63.6 cm. In one-half of the study population diagnosis leading to renal failure was congenital nephrouropathy. Twenty-eight per cent of the children had at least one pre-existing comorbidity. The mean height standard deviation score was -1.65 at the start of CPD, -1.82 after 12 months and -1.53 after 24 months. Catch-up growth was documented in 50% of patients during dialysis. A positive correlation was observed between longitudinal growth and both exchange volume (R(2) = 0.36) and dialysis session length (R(2) = 0.35), while a negative association was found with the number of peritonitis cases (P = 0.003). Peritonitis incidence was 1:20.7 episode:CPD-months (1:28.3 in the older children from the same registry) and was significantly higher in children with oligoanuria (1:15.5 episode:CPD-months) compared to infants with residual renal function (1:37.4 episode:CPD-months). Catheter survival rate was 70% at 12 months and 51% at 24 months. Catheter-related complications were similar in infants and older children (1:20.5 versus 1:19.8 episode:CPD-months), while clinical complications were more frequent in children under 1 year of age (1:18.3 versus 1:25.2 episode:CPD-months; P < 0.05). During the follow-up period, 33 patients were transplanted (39.3%), 18 were shifted to haemodialysis (21.4%) and 8 died (9.5%). The mortality rate was 4-fold greater than in older children (2.3%).

CONCLUSIONS

Our data confirm that infants on CPD represent a high-risk group; however, our experience demonstrated that growth was acceptable and a large portion was successfully transplanted. Increased efforts should be aimed at optimizing dialysis efficiency and preventing peritonitis. The higher mortality rate in infants was largely caused by comorbidities.

Peritoneal dialysis tailored to pediatric needs

Consideration of specific pediatric aspects is essential to achieve adequate peritoneal dialysis (PD) treatment in children. These are first of all the rapid growth, in particular during infancy and puberty, which must be accompanied by a positive calcium balance, and the age dependent changes in body composition. The high total body water content and the high ultrafiltration rates required in anuric infants for adequate nutrition predispose to overshooting convective sodium losses and severe hypotension. Tissue fragility and rapid increases in intraabdominal fat mass predispose to hernia and dialysate leaks. Peritoneal equilibration tests should repeatedly been performed to optimize individual dwell time. Intraperitoneal pressure measurements give an objective measure of intraperitoneal filling, which allow for an optimized dwell volume, that is, increased dialysis efficiency without increasing the risk of hernias, leaks, and retrofiltration. We present the concept of adapted PD, that is, the combination of short dwells with low fill volume to promote ultrafiltration and long dwells with a high fill volume to improve purification within one PD session. The use of PD solutions with low glucose degradation product content is recommended in children, but unfortunately still not feasible in many countries.

Glucose-based peritoneal dialysis fluids downregulate toll-like receptors and trigger hyporesponsiveness to pathogen-associated molecular patterns in human peritoneal mesothelial cells

The objective of this study was to investigate the effects of glucose-based peritoneal dialysis (PD) fluids and icodextrin-based PD fluids on the expression of Toll-like receptor 2 (TLR2)/TLR4 and subsequent ligand-induced mitogen-activated protein kinase (MAPK) and NF-kappaB signaling and tumor necrosis factor alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mRNA expression in human peritoneal mesothelial cells (HPMCs). A human peritoneal mesothelial cell line (HMrSV5) was stimulated with glucose-based and icodextrin-based peritoneal dialysis fluids. Cell viability was assessed using MTT [3-(4,5-dimethylthiazolyl)-2,5-diphenyl-2H-tetrazolium bromide]. TLR2/TLR4 expression was determined by real-time PCR, Western blotting, and an immunofluorescence assay. In addition, cells were pretreated with different PD solutions and then incubated with Pam3CSK4 or lipopolysaccharide (LPS), and the degrees of MAPK and NF-kappaB activation were reflected by detecting the phosphorylation levels of extracellular signal-regulated kinase 1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), p38, and p65, using a Western blot method. TNF-alpha and IL-1beta mRNA expression was measured by real-time PCR. Glucose-based peritoneal dialysis fluids suppressed the expression of TLR2 and TLR4 proteins in HPMCs. Challenge of cells with either Pam3CSK4 or LPS resulted in impaired TNF-alpha and IL-1beta production. Moreover, reduced TLR2 and TLR4 levels in glucose-based peritoneal dialysis solution-treated mesothelial cells were accompanied by reduced p42/44 (ERK1/2), JNK, p38 MAPK, and NF-kappaB p65 phosphorylation upon TLR ligand engagement. No significant changes in MAPK and NF-kappaB signaling and TNF-alpha and IL-1beta mRNA expression were observed in icodextrin-based PD solution-treated mesothelial cells. Glucose-based PD solution, but not icodextrin-based PD solution, downregulates expression of TLR2/TLR4 by human peritoneal mesothelial cells and triggers hyporesponsiveness to pathogen-associated molecular patterns.

Peritoneal inflammation after twenty-week exposure to dialysis solution: effect of solution versus catheter-foreign body reaction

BACKGROUND

We hypothesized that both sterile solutions and foreign body reaction to the peritoneal dialysis catheter are associated with inflammatory changes in rats exposed to hypertonic solution.

METHODS

Four hypertonic solutions (30 - 40 mL) were injected daily via needle and syringe over 20 weeks in 4 groups of rats: 4.25% standard clinical solution (LAC), LAC plus pyridoxamine (PYR), LAC plus ethyl pyruvate (EP), and a biocompatible 4% dextrose solution (BIC). Two groups received catheters: a non-injected 4-week catheter group (C4) and a group injected for 20 weeks with the BIC solution (CI). Control animals (CON) were not injected. In the C4 group, adherent cells were separated from the catheter and examined by culture and electron microscopy to ensure that animals were bacteria free prior to exposure to solution. Animals underwent transport experiments to determine mass transfer coefficients of mannitol (MTC(M)) and albumin (MTC(A)), osmotic filtration flux (J(osm)), and hydrostatic pressure-driven flux (J(p)). After euthanasia, tissues were examined for submesothelial thickness, vascular density, and immunohistochemistry for various cytokines.

RESULTS

The catheter cell layer was free of bacteria and consisted of macrophages, lymphocytes, mesothelial cells, and fibroblastic cells. Marked differences in angiogenesis and submesothelial thickening were noted for the catheter groups. Transport differences were mixed: MTC(M) was significantly less for the CI group and MTC(A) was variable among the groups. There were no differences among groups for J(osm) or J(p). Inflammatory markers in the catheter-adherent cells correlated with inflammatory changes in the tissue. These data demonstrate significant changes in submesothelial thickness, angiogenesis, transport function, and inflammatory markers between animals injected with sterile solutions over 20 weeks with and without catheters.

CONCLUSION

An indwelling catheter amplifies peritoneal inflammation from dialysis solutions through a foreign body reaction. Our data also suggest that additives to existing solutions may have limited the effect on inflammatory response to non-biocompatible solutions.

Inhibition of superoxide anion production by extracellular acidification in neutrophils

Extracellular acidification inhibited formyl-Met-Leu-Phe- or C5a-induced superoxide anion (O(2)(-)) production in differentiated HL-60 neutrophil-like cells and human neutrophils. A cAMP-increasing agonist, prostaglandin E(1), also inhibited the formyl peptide-induced O(2)(-) production. The inhibitory action on the O(2)(-) production by extracellular acidic pH was associated with cAMP accumulation and partly attenuated by H89, a protein kinase A inhibitor. A significant amount of mRNAs for T-cell death-associated gene 8 (TDAG8) and other proton-sensing ovarian cancer G-protein-coupled receptor 1 (OGR1)-family receptors is expressed in these cells. These results suggest that cAMP/protein kinase A, possibly through proton-sensing G-protein-coupled receptors, may be involved in extracellular acidic pH-induced inhibition of O(2)(-) production.

Cytotoxicity of Mononuclear Cells as Induced by Peritoneal Dialysis Fluids: Insight into Mechanisms that Regulate Osmotic Stress-Related Apoptosis

Objective

High glucose content of peritoneal dialysis fluids (PDFs) has been shown to contribute to loss of peritoneal function during long-term peritoneal dialysis. However, hyperosmolality and hypertonicity of PDF are usually seen as similar stress events inducing osmotic stress-induced programmed cell death. In this study, we examined the impact of various osmotic agents on apoptosis induced by hyperosmolar PDFs, focusing on the mechanisms underlying the lethal effects of PDFs on peripheral blood mono-nuclear cells (PBMCs).

Methods

We assessed apoptosis and necrosis by annexin V–propidium iodide (PI) labeling, and caspase-3 activity by fluorescence assay. F-actin remodeling was measured using fluorescent phalloidin labeling.

Results

Hyperosmolality does not cause the cytotoxicity observed with PDF, but exposure to agents incapable of permeating cell membranes results in a significant increase in the percentage of apoptotic PBMCs by annexin V–PI labeling, which is confirmed by the increase in caspase-3 activity. Interestingly, inhibition of caspase-3 by Z-VAD-FMK did not suppress apoptosis. Extracellular hypertonicity produced polymerization of filamentous actin and cell shrinkage, which displayed similar time courses. Cell shrinkage was blocked by cytochalasin D, indicating an active role for actin cytoskeleton in hypertonicity-induced cell shrinkage. F-actin polymerization was related to an increase in intra-cellular ionic strength. Finally, we excluded a direct role for actin remodeling in osmotic stress-induced programmed cell death.

Conclusions

Exposure to osmolytes that cannot penetrate cell membranes results in a hypertonicity-induced apoptosis that cannot be blocked by the broad-spectrum caspase inhibitor Z-VAD-FMK. In addition, extracellular hypertonicity induced by impermeant solutes produces F-actin polymerization through an increase in intracellular ionic strength. The remodeling of the cytoskeleton does not modulate apoptosis but participates in cell shrinkage.

Future technologies and techniques in peritoneal dialysis-opportunities and challenges ahead

In the last 5 years, we have started to witness the emergence of new technologies and techniques that offer the potential for improved patient outcomes but which often still lack clinical demonstration and/or confirmation in well-designed, multicentre studies. These include biocompatible solutions, glucose sparing regimens, low-sodium solutions, bimodal solution formulations and continuous flow peritoneal dialysis (CFPD). This review discusses the potential benefits ascribable to each of these technologies and an analysis of the challenges that have to be surmounted before anyone of these candidate technologies can be declared as established. The demonstration of either hard clinical endpoints or validated surrogate endpoints is very feasible in terms of sample size requirements for some outcome measures, such as preservation of RRF, but will be much more challenging for other endpoints such as preservation of UF capacity.

Risk Factors for Adverse Outcomes after Peritonitis-Related Technique Failure

Background

Peritonitis is the leading cause of technique failure in peritoneal dialysis (PD) patients. Some patients experience recurrent ascites, encapsulating peritoneal sclerosis (EPS), and even death after catheter removal. Little is known, however, about the risk factors for such complications.

Methods

The study subjects were 117 patients that had their PD catheter removed due to peritonitis between January 2000 and June 2006. Biochemical and clinical data were reviewed retrospectively. Serum C-reactive protein (CRP) and blood and effluent white blood cell counts (WBC) were measured at baseline and at 72 hours of peritonitis. Based on adverse outcomes, patients were classified into 4 groups: non-complication (NC; n = 73), recurrent ascites (A; n = 26), EPS (E; n = 10), and death directly related to peritonitis (D; n = 8).

Results

Age at PD catheter removal was significantly higher in D group compared to NC group (62.0 ± 10.6 vs 51.2 ± 11.5 years, p < 0.05). In addition, mean PD duration was significantly longer in E group compared to NC and A groups (130.5 ± 48.1 vs 58.8 ± 42.4 vs 74.8 ± 47.4 months, p < 0.01). Compared to baseline, effluent WBC was significantly decreased in NC group after 72 hours of peritonitis. In addition, serum CRP level was significantly decreased in NC and A groups, whereas it was significantly increased in D group. Multivariate analyses adjusted for age, PD duration, blood and effluent WBC, serum CRP, and micro-organisms revealed that serum CRP level at 72 hours predicted significantly the development of EPS [odds ratio (OR) 1.15, p < 0.05] and peritonitis-related death (OR 1.18, p < 0.01). In addition, PD duration (per 1 month increase: OR 1.03, p < 0.05) and age at PD catheter removal (per 1 year increase: OR 1.11, p < 0.05) were identified as significant determinants of EPS and peritonitis-related death respectively. Only effluent WBC at 72 hours was significantly associated with the development of ascites (OR 1.27, p < 0.05).

Conclusion

Older patients with long PD duration and those with persistently elevated serum CRP levels were likely to develop complications after peritonitis-related technique failure. Our study suggests that serial measurement of CRP may be helpful in predicting the development of complications after PD catheter removal.

Glucotoxicity in peritoneal dialysis--solutions for the solution!

Glucose has served well as the prototypical osmotic agent in peritoneal dialysis for more than 2 decades, because it affords many of the characteristics required of a safe and effective osmotic agent. The disadvantages of glucose include its rapid dissipation from the peritoneum and its resulting limited UF efficiency capacity in high and high-average transporters, the associated metabolic response to absorbed glucose in all patients, and the local effects of glucose, glucose degradation products, and hyperosmolality on peritoneal membrane structure and function. This paper briefly reviews the salient elements of glucotoxicity associated with conventional glucose-based peritoneal dialysis (PD) solution use, and then discusses emerging clinical benefits of newer nonglucose PD solutions. Potential future strategies designed to abrogate glucose-associated toxicity are then reviewed. These approaches include bimodal long-dwell solutions, nonglucose crystalloid osmotic agent mixtures, and administration of pharmacologically active agents.

Peritoneal changes after exposure to sterile solutions by catheter

Most current animal models that are used to study effects of long-term peritoneal exposure to dialysis solutions use an indwelling catheter for daily injections. It was hypothesized that the presence of a foreign body in the peritoneal cavity (PC) might alter the inflammatory response to the solutions and that the response would depend on exposure duration. For addressing these, long-term injections were carried out for 2 to 8 wk in 90 Sprague-Dawley rats: 40 via a subcutaneous port connected to a silicone catheter tunneled to the PC, 40 via direct needle injection, and 10 noninjected, age-control rats. Daily volumes were 30 to 40 ml of filter-sterilized, bicarbonate-buffered solutions that contained 4% dextrose. After 2, 4, 6, and 8 wk, anesthetized rats underwent transport experiments with a chamber affixed to the abdominal wall to determine mass transfer coefficients of mannitol (MTC(mannitol)) and albumin (MTC(BSA)), osmotic filtration flux (J(osm)), and hydrostatic pressure-driven flux. After the rats were killed, tissues were collected for measurement of peritoneal thickness, vascular density, and immunohistochemical staining. ANOVA demonstrated significant (P < 0.01) differences in thickness, vessel density, MTC(mannitol), and MTC(BSA) among the groups at the various time intervals and in overall means. Differences among the groups were less pronounced for hydrostatic pressure-driven flux and J(osm). Vessel density, MTC(mannitol), MTC(BSA), and J(osm) were dependent on injection duration (P < 0.01). There were marked differences between the needle injection and catheter injection groups at various intervals in the expression of three cytokines. It is concluded that the histologic and functional response depends on the duration of injection with animals that are exposed for as little as 2 wk demonstrating alterations. These findings confirm the hypothesis that the presence of a PC catheter increases inflammatory response to sterile solutions as evidenced by the structural and functional changes in the peritoneal barrier.

Similitude of transperitoneal permeability in different rodent species

Transgenic mice facilitate mechanistic studies of altered peritoneal transport, but the majority of transport studies have been carried out in rats. We hypothesized that mouse transport parameters, normalized to the peritoneal contact area, would be similar to those of the rat. To address this, we affixed small (∼10-mm diameter) plastic chambers to the serosa of the abdominal wall of anesthetized CD1 and C57BL mice. The chamber constrained transfer across the area of the chamber base and facilitated mixing, volumetric, and concentration measurements vs. time for mannitol, serum albumin, and osmotic and hydrostatic pressure-driven convection. The mass transfer coefficient of mannitol (MTCM) and of serum albumin (MTCBSA), hydrostatic pressure-driven flux ( JP), and osmotic filtration ( Josm) were calculated from the time-dependent volume and concentration data. The units of all parameters (μl·min−1·cm−2) were compared with previously derived parameters from SD rats with a one-way ANOVA. Results indicated small but significant differences in MTCBSA(x102): CD1, 9.72 ± 1.97, n = 6; C57BL, 7.13 ± 1.52, n = 10; rat, 12.5 ± 1.6, n = 17 ( P = 0.03). ANOVAs of all other parameters were not significant and confirmed our hypothesis: MTCM(CD1, 3.20 ± 0.38, n = 7; C57BL, 2.34 ± 0.41, n = 6; rat, 2.72 ± 0.23 n = 19), JP(CD1, 0.77 ± 0.15, n = 10; C57BL, 0.33 ± 0.13, n = 15; rat, 0.51 ± 0.16, n = 9), or Josm(CD1, 0.92 ± 0.35, n = 6; C57BL, 0.49 ± 0.35, n = 6; rat 1.72 ± 0.35, n = 6). We conclude that elimination of the variable peritoneal transfer area normalizes calculated transport characteristics and facilitates comparison between species.

Peroxisome proliferator-activated receptor-gamma is expressed by rat peritoneal mesothelial cells: its potential role in peritoneal cavity local defense

BACKGROUND/AIMS

Peritoneal mesothelial cells (PMCs) play an important role in peritoneal inflammatory and immune response. It was reported that the peroxisomal proliferator-activated receptor-gamma (PPARgamma) ligand could effectively reduce inflammatory processes. However, the expression and function of PPARgamma in PMCs has not been reported. This study was to investigate the expression of PPARgamma in rat PMCs and the effect of PPARgamma activation on the production of CD40 and ICAM-1 induced by lipopolysaccharide (LPS).

METHODS

Rat PMCs (RPMCs) were harvested from the peritoneal cavity of Sprague-Dawley rats and maintained under defined in vitro conditions. The cells were treated separately with LPS, 15d-PGJ(2), and ciglitazone at different time points. The mRNA and protein expression of PPARgamma, CD40 and ICAM-1 were detected by RT-PCR and Western blot, respectively. The intracellular distribution of PPARgamma was detected by immunocytochemistry.

RESULTS

RPMCs expressed PPARgamma both at the mRNA and protein level. The specific signals for PPARgamma were mainly localized in the nucleus with weak staining in the cytoplasm. Stimulation of RPMCs with LPS resulted in a time-dependent increase in the expression of PPARgamma with the peak of mRNA at 3 h and protein at 12 h. Thereafter the expression of PPARgamma gradually attenuated. The mRNA expressions for CD40, ICAM-1 and protein expression of ICAM-1 were significantly upregulated following stimulation with LPS. Both 15d-PGJ(2) and ciglitazone decreased the expression of CD40 mRNA and ICAM-1 protein. However, ciglitazone was less effective than 15d-PGJ(2).

CONCLUSIONS

There is constitutive expression of PPARgamma in cultured RPMCs and PPARgamma ligands which strongly inhibit LPS-induced CD40 and ICAM-1 production in RPMCs. It suggested that PPARgamma might play a part in the local defense of the peritoneal cavity by downregulating inflammatory mediators, which may play a potential role in preventing peritoneal fibrosis induced by peritonitis. Further in vivo study is needed to demonstrate the long-term effects.

Effects of new peritoneal dialysis solutions on leukocyte recruitment in the rat peritoneal membrane

OBJECTIVES

Peritonitis remains a principal cause of dropout in peritoneal dialysis (PD). The physiological host response to a peritoneal infection involves a rise in numbers of circulating leukocytes to the peritoneal cavity. We evaluated the effects of (1) conventional peritoneal dialysis fluid (PDF), (2) bicarbonate-based PDF, low in glucose degradation products, and (3) non-glucose PDF on peritoneal leukocyte recruitment in response to an inflammatory stimulus using intravital microscopy.

METHODS

The visceral peritoneum was exposed to EBSS, conventional lactate-buffered and bicarbonate/lactate-buffered glucose-based PDF and three lactate-buffered non-glucose PDF-icodextrin, amino acid-based PDF and amino acid/glycerol-based PDF. The number of rolling, adhering and extravasated leukocytes and leukocyte rolling velocity was assessed at different time intervals after stimulation with lipopolysaccharide (LPS).

RESULTS

Exposure to LPS dissolved in EBSS dramatically increased the number of rolling, adhering and extravasated leukocytes and decreased leukocyte rolling velocity. Conventional PDF completely abolished LPS-induced leukocyte recruitment. Bicarbonate/lactate-buffered PDF only minimally affected the process of leukocyte recruitment, whereas icodextrin PDF resulted in partial inhibition of the immune response. The amino acid-based and the amino acid/glycerol-based PDF inhibited leukocyte recruitment to a similar extent as conventional PDF.

CONCLUSIONS

Bicarbonate/lactate-buffered PDF has superior biocompatibility towards peritoneal host defense, in spite of its high glucose concentrations. Lactate-buffered non-glucose containing PDF has substantial inhibitory effects on leukocyte recruitment, indicating that the bioincompatibility of high lactate concentrations and/or low pH may not be underestimated.

Correlating structure with solute and water transport in a chronic model of peritoneal inflammation

To study the process of chronic peritoneal inflammation from sterile solutions, we established an animal model to link structural changes with solute and water transport. Filtered solutions containing 4% N-acetylglucosamine (NAG) or 4% glucose (G) were injected intraperitoneally daily in 200- to 300-g rats and compared with controls (C). After 2 mo, each animal underwent transport studies using a chamber affixed to the parietal peritoneum to determine small-solute and protein mass transfer, osmotic filtration, and hydraulic flow. After euthanasia, parietal tissues were sampled for histological analysis, which demonstrated significant differences in peritoneal thickness (microm; C, 42.6 +/- 7.5; G, 80.4 +/- 22.3; NAG, 450 +/- 104; P < 0.05). Staining for VEGF correlated with CD-31 vessel counts (no./mm2: C, 53.1 +/- 16.1; G, 166 +/- 32; NAG, 183 +/- 32; P < 0.05). Tissue analysis showed treatment effects on tissue hyaluronan (micro/g: C, 962 +/- 73; G, 1,169 +/- 69; NAG, 1,428 +/- 69; P < 0.05) and collagen (microg/g: C, 56.9 +/- 12.0; G, 107 +/- 12; NAG, 97.6 +/- 11.4; P < 0.05) but not sulfated glycosaminoglycan. Transport experiments revealed no significant differences in mannitol transfer or osmotic flow. Changes were seen in hydrostatic pressure-driven flux (microl x min(-1) x cm(-2): C, 0.676 +/- 0.133; G, 0.317 +/- 0.124; NAG, 0.284 +/- 0.117; P < 0.05) and albumin transfer (microl x min(-1) x cm(-2): C, 0.331 +/- 0.028; G, 0.286 +/- 0.026; NAG, 0.229 +/- 0.025; P < 0.04). We conclude that alteration of the interstitial matrix correlates with diminished hydraulic conductivity and macromolecular transport.

Expanded-spectrum beta-lactamase producing Klebsiella pneumoniae-related peritonitis in a patient on peritoneal dialysis

While hospitalized for pneumonia with ventilator-dependent respiratory failure, a 45-year-old man on continuous ambulatory peritoneal dialysis (CAPD) had nosocomial peritonitis secondary to infection by expanded spectrum beta-lactamase producing Klebsiella pneumoniae (ESBL-Kp). He was treated successfully with a 3-week course of intraperitoneal (IP) flomoxef therapy without subsequent relapse, loss of peritoneal catheter, ultrafiltration failure, or dialysis inadequacy. The International Consensus Panel recommends IP ceftazidime as the treatment of choice for CAPD patients suffering Klebsiella species-related peritonitis. However, the most appropriate form of IP antibiotic therapy and the outcomes for expanded-spectrum beta-lactamase (ESBL)-producing bacteria-related peritonitis for CAPD patients have not been established yet. Further, the ability to correctly report minimal inhibitory concentrations (MICs) of ceftazidime for ESBL bacteria in the resistant range varies between laboratories, making the diagnosis of ESBL-Kp-related CAPD peritonitis more complex and difficult. Thus, it appears reasonable to suggest that its incidence is probably underestimated and its significance ignored. The authors suggest that a 3-week IP treatment with flomoxef, a synthesized oxacephem, with loading and maintenance doses of 250 and 125 mg/L, respectively, is effective and safe for ESBL-Kp-related peritonitis in these patients. ESBL producing bacterial infection should be considered as a possible cause of overt CAPD-related peritonitis. Early detection of ESBLB pathogens and institution of effective antibiotic treatment may improve the prognosis.

La biocompatibilité des solutions de dialyse péritonéale

Repeated and long-term exposure to conventional glucose-based peritoneal dialysis fluids (PDFs) with poor biocompatibility plays a central role in the pathogenesis of the functional and structural changes of the peritoneal membrane. We have used immortalized human peritoneal mesothelial cells in culture to assess in vitro the biocompatibility of PDFs. Low pH, high glucose concentration and heat sterilization represent major factors of low biocompatibility. Two recent groups of glucose derivatives have been described. Glucose degradation products (GDPs) are formed during heat sterilization (glycoxidation) and storage. GDPs can bind protein and form AGEs (Advanced Glycation End-products), which can also result from the binding of glucose to free NH2 residues of proteins (glycation). The physiological pH, and the separation of glucose during heat sterilization (low GDP content) in the most recent PDFs dramatically increase the biocompatibility. The choice of PD programs with high biocompatibility PDFs allows preserving the function of the peritoneal membrane. Improvement of PDF biocompatibility may limit the occurrence of chronic chemical peritonitis and may allow long-term PD treatment.