Effects of conventional and new peritoneal dialysis fluids on leukocyte recruitment in the rat peritoneal membrane

Peritoneal Dialysis Fluid Supplementation with Alanyl-Glutamine Attenuates Conventional Dialysis Fluid-Mediated Endothelial Cell Injury by Restoring Perturbed Cytoprotective Responses

Long-term clinical outcome of peritoneal dialysis (PD) depends on adequate removal of small solutes and water. The peritoneal endothelium represents the key barrier and peritoneal transport dysfunction is associated with vascular changes. Alanyl-glutamine (AlaGln) has been shown to counteract PD-induced deteriorations but the effect on vascular changes has not yet been elucidated. Using multiplexed proteomic and bioinformatic analyses we investigated the molecular mechanisms of vascular pathology in-vitro (primary human umbilical vein endothelial cells, HUVEC) and ex-vivo (arterioles of patients undergoing PD) following exposure to PD-fluid. An overlap of 1813 proteins (40%) of over 3100 proteins was identified in both sample types. PD-fluid treatment significantly altered 378 in endothelial cells and 192 in arterioles. The HUVEC proteome resembles the arteriolar proteome with expected sample specific differences of mainly immune system processes only present in arterioles and extracellular region proteins primarily found in HUVEC. AlaGln-addition to PD-fluid revealed 359 differentially abundant proteins and restored the molecular process landscape altered by PD fluid. This study provides evidence on validity and inherent limitations of studying endothelial pathomechanisms in-vitro compared to vascular ex-vivo findings. AlaGln could reduce PD-associated vasculopathy by reducing endothelial cellular damage, restoring perturbed abundances of pathologically important proteins and enriching protective processes.

Superior Patient Survival for Continuous Ambulatory Peritoneal Dialysis Patients Treated with a Peritoneal Dialysis Fluid with Neutral pH and Low Glucose Degradation Product Concentration (Balance)

Background

In recent years, laboratory and clinical research has suggested the need for peritoneal dialysis fluids (PDFs) that are more biocompatible than the conventional PDFs commonly used today. Bioincompatibility of PDF has been attributed to low pH, lactate, glucose, glucose degradation products (GDPs), and osmolality. PDFs with neutral pH and low GDPs are now available commercially. In vitro and early clinical studies suggest that these solutions are indeed more biocompatible but, as of now, there is no evidence that their use improves patient outcome.

Methods

Using a dedicated database of over 2000 patients treated with PD in Korea, we were able to conduct a retrospective observational study comparing outcomes for incident continuous ambulatory PD patients treated with a standard, conventional, heat-sterilized PDF to the outcomes for patients treated with a novel, low GDP, neutral-pH PDF prepared in a dual-compartment, double-bag PD system (Balance; Fresenius Medical Care, St. Wendel, Germany). In an intention-to-treat analysis, patient and technique survival, peritonitis-free survival, and peritonitis rates were compared in 611 patients treated with Balance for up to 30 months and 551 patients with a standard PDF (stay·safe; Fresenius Medical Care) treated in the same era and with equivalent follow-up.

Results

The patients were well matched for most relevant characteristics except older age distribution for the patients treated with the standard PDF. Patients treated with Balance had significantly superior survival compared to those treated with the standard PDF (74% vs 62% at 28 months, p = 0.0032). In a multivariate Cox regression model including age, diabetes, and gender, the survival advantage persisted (relative risk of death for Balance 0.75, 95% confidence interval 0.56 – 0.99, p = 0.0465). Modality technique survival was similar in Kaplan–Meier analysis for both PDFs. No differences were detected in peritonitis-free survival or in peritonitis rates between the two solutions.

Conclusion

This study, for the first time, suggests that treatment with a novel biocompatible PDF with low GDP concentration and neutral pH confers a significant survival advantage. The exact mechanisms for such a survival advantage cannot be determined from this study. The usual criticisms of observational studies apply and the results reported here strongly warrant the undertaking of appropriately designed, randomized, controlled clinical trials.

Animal Models in Peritoneal Dialysis Research: A Need for Consensus

The development of an adequate animal model for peritoneal research remains an object of concern. In vivo peritoneal dialysis (PD) research is hampered by the large variety of available models that make interpretation of results and comparison of studies very difficult. Species and strain of experimental animals, method of peritoneal access, study duration, measures of solute transport and ultrafiltration, and sampling for histology differ substantially among the various research groups. A collective effort to discuss the shortcomings and merits of the different experimental models may lead to a consensus on a standardized animal model of PD.

The Effects of Peritoneal Dialysis Solutions on Peritoneal Host Defense

Conventional peritoneal dialysis fluid (PDF) is a bioincompatible solution owing to the acidic pH, the high glucose concentrations and the associated hyperosmolarity, the high lactate concentrations, and the presence of glucose degradation products (GDPs). This unphysiologic composition adversely affects peritoneal host defense and may thus contribute to the development of PD-related peritonitis. The viability of polymorphonuclear leukocytes, monocytes, peritoneal macrophages, and mesothelial cells is severely depressed in the presence of conventional PDF. In addition, the production of inflammatory cytokines and chemoattractants by these cells is markedly affected by conventional PDF. Further, conventional PDF hampers the recruitment of circulating leukocytes in response to an infectious stimulus. Finally, phagocytosis, respiratory burst, and bacterial killing are markedly lower when polymorphonuclear leukocytes, monocytes, and peritoneal macrophages are exposed to conventional PDF. Although there are a few discrepant results, all major PDF components have been implicated as causative factors. Generally, novel PDF with alternative osmotic agents or with alternative buffers, neutral pH, and low GDP content have much milder inhibitory effects on peritoneal host defense. Clinical studies, however, still need to demonstrate their superiority with respect to the incidence of PD-related peritonitis.

Better Preservation of the Peritoneum in Rats Exposed to Amino Acid-Based Peritoneal Dialysis Fluid

Background

Glucose-containing peritoneal dialysis fluids (PDF) show impaired biocompatibility, which is related partly to their high glucose content, presence of glucose degradation products, low pH, and lactate buffer, or a combination of these factors. In a rat chronic peritoneal exposure model, we compared effects of an amino acid-based PDF (AA-PDF) with a glucose-containing PDF on the peritoneal microcirculation and morphology.

Method

Two groups of rats received 10 mL of either fluid daily for 5 weeks via peritoneal catheters connected to implanted subcutaneous mini vascular access ports. Leukocyte–endothelium interactions in the mesenteric venules were investigated by intravital microscopy. Quantification of angiogenesis and fibrosis and inspection of the mesothelial cell layer were performed by light and electron microscopy.

Results

Daily exposure to glucose-containing PDF resulted in a significant increase in the number of rolling leukocytes in mesenteric venules, whereas instillation of AA-PDF did not change the level of leukocyte rolling. Glucose-containing PDF evoked a significantly higher number of milky spots in the omentum, whereas this response was significantly reduced in animals exposed to the AA-PDF ( p < 0.02). Chronic instillation of glucose-containing PDF induced angiogenesis in various peritoneal tissues, accompanied by fibrosis in the mesentery and parietal peritoneum. Quantitative morphometric evaluation of omentum and mesentery showed a clear trend toward less angiogenesis after treatment with the AA-PDF compared to the glucose-containing PDF, which reached statistical significance in the parietal peritoneum ( p < 0.04). Instillation of AA-PDF resulted in approximately 50% reduction of fibrosis in the mesentery ( p < 0.04) and approximately 25% reduction in the parietal peritoneum ( p < 0.009) compared to glucose-containing PDF. Glucose-containing PDF damaged the mesothelial cell layer, whereas the mesothelium was intact after AA-PDF treatment, as evidenced by electron microscopy.

Conclusion

Our data in a rat chronic peritoneal exposure model clearly demonstrate reduced immune activation (evidenced by decreased number of rolling leukocytes and decreased induction of omental milky spots) and reduced neoangiogenesis, fibrosis, and mesothelial damage of the peritoneal membrane after treatment with AA-PDF compared to glucose-containing PDF.

Evidence for Less Irritation to the Peritoneal Membrane in Rats Dialyzed with Solutions Low in Glucose Degradation Products

Background

Acidic pH and the presence of glucose degradation products (GDP) are believed to compromise the biocompatibility of peritoneal dialysis fluids (PDF). The present study examines the effects of long-term exposure to GDP and low pH by comparing conventional PDF and a new, neutral pH, low GDP solution.

Methods

All experiments were performed using a chronic infusion model of dialysis in nonuremic rats. The animals were treated for 6 weeks with 2 daily injections of 4.25% glucose-containing PDF. The following PDF were tested: CAPD3 (single-chamber bag, low pH, high GDP), CAPD3 pH 7.4 (single-chamber bag, neutral pH, high GDP), CAPD3-Balance (double-chamber bag, neutral pH, low GDP). All test solutions were obtained from Fresenius Medical Care, Bad Homburg, Germany.

Results

After 6 weeks of exposure, peritoneal permeability to water, urea, creatinine, glucose, and sodium, assessed by peritoneal equilibration test, was similar in all groups. However, compared to other PDF, dialysis with CAPD3-Balance was associated with reduced concentrations of protein and hyaluronan in the dialysate, decreased peritoneal eosinophilia, and reduced dialysate levels of chemokines CCL2/MCP-1 and CCL5/RANTES. Morphologic changes in the peritoneal membrane of CAPD3-Balance-treated animals were much less pronounced and included reduced vascular density, preservation of the mesothelial monolayer and intercellular junction, and no reduplication of the submesothelial basement membrane.

Conclusions

A new generation of PDF with physiologic pH and low GDP level produce less irritation to the peritoneal membrane and better preserve its structural integrity. This effect seems to be related predominantly to minimized GDP concentrations.

Short-Term Effects of a New Bicarbonate/Lactate-Buffered and Conventional Peritoneal Dialysis Fluid on Peritoneal and Systemic Inflammation in CAPD Patients: A Randomized Controlled Study

Objectives

This study was designed to compare the local peritoneal and systemic inflammatory effects of a conventional lactate-based (Lac) peritoneal dialysis (PD) solution and a new biocompatible bicarbonate/lactate-based (Bic/ Lac) solution having low concentration of glucose degradation products.

Methods

26 stable, prevalent PD patients were enrolled in this prospective study. They sequentially underwent 3 months of therapy with the Lac solution and 3 months with the Bic/Lac solution in a randomized order. Flow cytometry was used to measure the expression of inflammatory molecules on peritoneal cells in overnight effluent collected at the end of each study period.

Results

21 patients successfully completed the study. Mean fluorescence intensity of human leukocyte antigen (HLA)-DR and CD14 expression by macrophages were not different between Lac and Bic/Lac. The peritoneal appearance rate of cancer antigen 125 (kU/minute) was 68 ± 37 with Lac and 133 ± 66 with Bic/Lac ( p < 0.001), and of interleukin (IL)-6 (ng/minute), 0.28 ± 0.2 with Lac and 0.18 ± 0.16 with Bic/Lac ( p = 0.014). HLA-DR macrophage expression and IL-6 peritoneal appearance rates did not correlate. Serum concentrations with Lac and Bic/Lac were, for IL-6, 3.49 ± 2.28 and 3.72 ± 2.46 ng/L ( p = 0.17), and for high-sensitivity C-reactive protein, 2.31 ± 2.98 and 2.71 ± 3.31 mg/L ( p = 0.32) respectively. The concentration of effluent macrophages (x106/L) with Lac was 1.6 ± 1.6 and with Bic/Lac 2.6 ± 3.3 ( p = 0.07).

Conclusions

We conclude that, although there was a significant reduction in peritoneal IL-6 in patients using Bic/ Lac solution, systemic levels of inflammatory markers did not differ between the two solutions and no changes were present in macrophage surface activation markers, suggesting perhaps a less important role of peritoneal macrophages in the intraperitoneal chronic inflammatory process. The number of effluent macrophages tended to be higher in patients using the Bic/Lac solution, possibly contributing to improved intraperitoneal defense.

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.

No Significant Differences in Peritoneal Fluid Handling in Children Using pH-Neutral or Acidic Solutions

Objectives

Differences in peritoneal fluid handling in the acute setting can be expected if children are converted to pH-neutral dialysis solutions because conventional acidic solutions exert toxic effects on peritoneal mesothelial cells and microcirculation. Peritoneal fluid kinetics was therefore investigated with both types of solutions in a group of children.

Design

Peritoneal equilibration tests (PETs) were performed in 12 patients [mean age 70 months, mean time on peritoneal dialysis (PD) 18 months] using a pH-neutral PD fluid (Physioneal 3.86%; Baxter Ltd, Castlebar, Ireland) and dextran 70 as a volume marker. The results of these PETs were compared to those of a historic group of 12 children (mean age 75 months, mean time on PD 17 months).

Setting

Pediatric dialysis unit in a tertiary institute.

Patients

Stable pediatric PD patients.

Main Outcome Measures

Transcapillary ultrafiltration (TCUF) and marker clearance, dialysate-to-plasma (D/P) ratios for urea and creatinine, and Dt/D0ratio for glucose.

Results

TCUF and lymphatic absorption were not different between the two groups. There was also no significant difference in small solute clearance measured by D/P ratio for urea and creatinine and Dt/D0ratio for glucose.

Conclusion

Peritoneal fluid kinetics is not significantly altered if pH-neutral dialysis solutions are applied compared to acidic solutions. An altered TCUF, as is hypothetically possible using an acidic solution, was not established.

Association of Staphylococcus nasal colonization and HIV in end-stage renal failure patients undergoing peritoneal dialysis

INTRODUCTION

Staphylococcal infections can cause significant morbidity in patients undergoing dialysis. This study evaluated the effects of HIV infection on nasal carriage of Staphylococcus aureus, staphylococcal peritonitis, and catheter infection rates in patients with end-stage renal failure managed with continuous ambulatory peritoneal dialysis (CAPD).

METHODS

Sixty HIV-positive and 59 HIV-negative CAPD patients were enrolled and followed up for up to 18 months. S. aureus nasal carriage (detected by nasal swab culture), Staphylococcal peritonitis (diagnosed by clinical presentation, and CAPD effluent Staphylococcal culture and white blood cell count ≥100 cells/µL), and catheter infections (including exit site and tunnel infections) were assessed monthly.

RESULTS

At 18 months, S. aureus nasal carriage rates were 43.3% and 30.5% (p = 0.147) and the methicillin-resistant S. aureus (MRSA) nasal carriage rates were 31.7% and 13.6% (p = 0.018) for the HIV-positive and HIV-negative cohorts, respectively. The HIV-positive cohort was associated with increased hazards for staphylococcal peritonitis, (adjusted hazard ratio [AHR] 2.85, 95% confidence interval [CI] 1.19-6.84, p = 0.019) due to increased coagulase-negative staphylococcal (CNS) peritonitis rate in the HIV-positive cohort compared with the HIV-negative cohort (0.435 vs. 0.089 episodes/person-years; AHR 7.64, CI 2.18-26.82, p = 0.001). On multivariable analysis, CD4+ cell count <200 cells/µL, diabetes, and S. aureus nasal carriage were found to be independent predictors of S. aureus peritonitis.

CONCLUSIONS

These findings suggest that HIV infection may be a risk factor for MRSA nasal colonization and may increase the risks of CNS peritonitis, while a CD4+ cell count <200 cells/µL and S. aureus nasal carriage may be important predictors of S. aureus peritonitis.

Peritoneal Dialysis Vintage and Glucose Exposure but Not Peritonitis Episodes Drive Peritoneal Membrane Transformation During the First Years of PD

The impact of peritoneal dialysis (PD) associated peritonitis on peritoneal membrane integrity is incompletely understood. Children are particularly suited to address this question, since they are largely devoid of preexisting tissue damage and life-style related alterations. Within the International Peritoneal Biobank, 85 standardized parietal peritoneal tissue samples were obtained from 82 children on neutral pH PD fluids with low glucose degradation product (GDP) content. 37 patients had a history of peritonitis and 16 of the 37 had two or more episodes. Time interval between tissue sampling and the last peritonitis episode was 9 (4, 36) weeks. Tissue specimen underwent digital imaging and molecular analyses. Patients with and without peritonitis were on PD for 21.0 (12.0, 36.0) and 12.8 (7.3, 27.0) months (p = 0.053), respectively. They did not differ in anthropometric or histomorphometric parameters [mesothelial coverage, submesothelial fibrosis, blood, and lymphatic vascularization, leukocyte, macrophage and activated fibroblast counts, epithelial-mesenchymal transition (EMT), podoplanin positivity and vasculopathy]. VEGF and TGF-ß induced pSMAD abundance were similar. Similar findings were also obtained after matching for age and PD vintage and a subgroup analysis according to time since last peritonitis (<3, <6, >6 months). In patients with more than 24 months of PD vintage, submesothelial thickness, vessel number per mmm section length and ASMA fibroblast positivity were higher in patients with peritonitis history; only the difference in ASMA positivity persisted in multivariable analyses. While PD duration and EMT were independently associated with submesothelial thickness, and glucose exposure and EMT with peritoneal vessel density in the combined groups, submesothelial thickness was independently associated with EMT in the peritonitis free patients, and with duration of PD in patients with previous peritonitis. This detailed analysis of the peritoneal membrane in pediatric patients on PD with neutral pH, low GDP fluids, does not support the notion of a consistent long-term impact of peritonitis episodes on peritoneal membrane ultrastructure, on inflammatory and fibrotic cell activity and EMT. Peritoneal alterations are mainly driven by PD duration, dialytic glucose exposure, and associated EMT.

Biocompatible Peritoneal Dialysis: The Target Is Still Way Off

Peritoneal dialysis (PD) is a cost-effective, home-based therapy for patients with end-stage renal disease achieving similar outcome as compared to hemodialysis. Still, a minority of patients only receive PD. To a significant extend, this discrepancy is explained by major limitations regarding PD efficiency and sustainability. Due to highly unphysiological composition of PD fluids, the peritoneal membrane undergoes rapid morphological and long-term functional alterations, which limit the treatment and contribute to adverse patient outcome. This review is focused on the peritoneal membrane ultrastructure and its transformation in patients with kidney disease and chronic PD, underlying molecular mechanisms, and potential systemic sequelae. Current knowledge on the impact of conventional and second-generation PD fluids is described; novel strategies and innovative PD fluid types are discussed.

Biocompatible dialysis fluids for peritoneal dialysis

BACKGROUND

Biocompatible peritoneal dialysis (PD) solutions, including neutral pH, low glucose degradation product (GDP) solutions and icodextrin, have previously been shown to favourably influence some patient-level outcomes, albeit based on generally sub-optimal quality studies. Several additional randomised controlled trials (RCT) evaluating biocompatible solutions in PD patients have been published recently. This is an update of a review first published in 2014.

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

The Cochrane Kidney and Transplant Specialised Register was searched up to 12 February 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Specialised Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

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

DATA COLLECTION AND ANALYSIS

Two authors extracted data on study quality and outcomes. Summary effect estimates were obtained using a random-effects model, and results were expressed as risk ratios and 95% confidence intervals (CI) for categorical variables, and mean differences (MD) or standardised mean differences (SMD) and 95% CI for continuous variables.

MAIN RESULTS

This review update included 42 eligible studies (3262 participants), including six new studies (543 participants). Overall, 29 studies (1971 participants) compared neutral pH, low GDP PD solution with conventional PD solution, and 13 studies (1291 participants) compared icodextrin with conventional PD solution. Risk of bias was assessed as high for sequence generation in three studies, allocation concealment in three studies, attrition bias in 21 studies, and selective outcome reporting bias in 16 studies.Neutral pH, low GDP versus conventional glucose PD solutionUse of neutral pH, low GDP PD solutions improved residual renal function (RRF) preservation (15 studies, 835 participants: SMD 0.19, 95% CI 0.05 to 0.33; high certainty evidence). This approximated to a mean difference in glomerular filtration rate of 0.54 mL/min/1.73 m² (95% CI 0.14 to 0.93). Better preservation of RRF was evident at all follow-up durations with progressively greater preservation observed with increasing follow up duration. Neutral pH, low GDP PD solution use also improved residual urine volume preservation (11 studies, 791 participants: MD 114.37 mL/day, 95% CI 47.09 to 181.65; high certainty evidence). In low certainty evidence, neutral pH, low GDP solutions may make little or no difference to 4-hour peritoneal ultrafiltration (9 studies, 414 participants: SMD -0.42, 95% CI -0.74 to -0.10) which approximated to a mean difference in peritoneal ultrafiltration of 69.72 mL (16.60 to 122.00 mL) lower, and may increase dialysate:plasma creatinine ratio (10 studies, 746 participants: MD 0.01, 95% CI 0.00 to 0.03), technique failure or death compared with conventional PD solutions. It is uncertain whether neutral pH, low GDP PD solution use led to any differences in peritonitis occurrence, hospitalisation, adverse events (6 studies, 519 participants) or inflow pain (1 study, 58 participants: RR 0.51, 95% CI 0.24 to 1.08).Glucose polymer (icodextrin) versus conventional glucose PD solutionIn moderate certainty evidence, icodextrin probably reduced episodes of uncontrolled fluid overload (2 studies, 100 participants: RR 0.30, 95% CI 0.15 to 0.59) and augmented peritoneal ultrafiltration (4 studies, 102 participants: MD 448.54 mL/d, 95% CI 289.28 to 607.80) without compromising RRF (4 studies, 114 participants: SMD 0.12, 95% CI -0.26 to 0.49; low certainty evidence) which approximated to a mean creatinine clearance of 0.30 mL/min/1.73m² higher (0.65 lower to 1.23 higher) or urine output (3 studies, 69 participants: MD -88.88 mL/d, 95% CI -356.88 to 179.12; low certainty evidence). It is uncertain whether icodextrin use led to any differences in adverse events (5 studies, 816 participants) technique failure or death.

AUTHORS' CONCLUSIONS

This updated review strengthens evidence that neutral pH, low GDP PD solution improves RRF and urine volume preservation with high certainty. These effects may be related to increased peritoneal solute transport and reduced peritoneal ultrafiltration, although the evidence for these outcomes is of low certainty due to significant heterogeneity and suboptimal methodological quality. Icodextrin prescription increased peritoneal ultrafiltration and mitigated uncontrolled fluid overload with moderate certainty. The effects of either neutral pH, low GDP solution or icodextrin on peritonitis, technique survival and patient survival remain uncertain and require further high quality, adequately powered RCTs.

Low GDP Solution and Glucose-Sparing Strategies for Peritoneal Dialysis

Long-term exposure to a high glucose concentration in conventional peritoneal dialysis (PD) solution has a number of direct and indirect (via glucose degradation products [GDP]) detrimental effects on the peritoneal membrane, as well as systemic metabolism. Glucose- or GDP-sparing strategies often are hypothesized to confer clinical benefits to PD patients. Icodextrin (glucose polymer) solution improves peritoneal ultrafiltration and reduces the risk of fluid overload, but these beneficial effects are probably the result of better fluid removal rather than being glucose sparing. Although frequently used for glucose sparing, the role of amino acid-based solution in this regard has not been tested thoroughly. When glucose-free solutions are used in a combination regimen, published studies showed that glycemic control was improved significantly in diabetic PD patients, and there probably are beneficial effects on peritoneal function. However, the long-term effects of glucose-free solutions, used either alone or as a combination regimen, require further studies. On the other hand, neutral pH-low GDP fluids have been shown convincingly to preserve residual renal function and urine volume. The cost effectiveness of these solutions supports the regular use of neutral pH-low GDP solutions. Nevertheless, further studies are required to determine whether neutral pH-low GDP solutions exert beneficial effects on patient-level outcomes, such as peritonitis, technique survival, and patient survival.

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.

Peritoneal Dialysis Catheter Increases Leukocyte Recruitment in the Mouse Parietal Peritoneum Microcirculation and Causes Fibrosis

♦

BACKGROUND

The objective of this study was to examine the effects of a conventional dialysis solution and peritoneal catheter on leukocyte-endothelial cell interactions in the microcirculation of the parietal peritoneum in a subacute peritoneal dialysis (PD) mouse model. ♦

METHODS

An intraperitoneal (IP) catheter with a subcutaneous injection port was implanted into mice and, after a 2-week healing period, the animals were injected daily for 6 weeks with a 2.5% dextrose solution. Intravital microscopy (IVM) of the parietal peritoneum microcirculation was performed 4 hours after the last injection of the dialysis solution. Leukocyte-endothelial cell interactions were quantified and compared with catheterized controls without dialysis treatment and naïve mice. ♦

RESULTS

The number of rolling and extravascular leukocytes along with peritoneal fibrosis and neovascularization were significantly increased in the catheterized animals compared with naïve mice but did not significantly differ between the 2 groups of catheterized animals with sham injections or dialysis solution treatment. ♦

CONCLUSION

The peritoneal catheter implant increased leukocyte rolling and extravasation, peritoneal fibrosis and vascularization in the parietal peritoneum independently from the dialysis solution treatment.

High Peritoneal Glucose Exposure Is Associated with Increased Incidence of Relapsing and Recurrent Bacterial Peritonitis in Patients Undergoing Peritoneal Dialysis

Aim: We investigated the association of peritoneal glucose exposure and dialysis exchange number with peritonitis outcome in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Methods: The first episodes of bacterial peritonitis were retrospectively analyzed in 187 CAPD patients. Peritoneal glucose exposure was calculated based on PD prescription at the onset of peritonitis. Results: Patients with peritoneal glucose exposure ≤140 g/day showed a higher and complete cure rate of peritonitis (66 vs. 51.7%, p = 0.047), lower occurrence of relapsing/recurrent peritonitis (10.0 vs. 21.8%, p = 0.026) and catheter removal (14.0 vs. 26.4%, p = 0.033). Patients who exchanged more than three times every day demonstrated marginally higher catheter removal rate (24.1 vs. 13.0%, p = 0.085). Logistic analysis indicated that peritoneal glucose exposure >140 g/day was an independent predictor for relapsing/recurrent peritonitis (RR: 1.959, p = 0.042). Conclusion: High peritoneal glucose exposure is associated with increased incidence of relapsing/recurrent peritonitis in CAPD patients.

Associations between the duration of dialysis, endotoxemia, monocyte chemoattractant protein-1, and the effects of a short-dwell exchange in patients requiring continuous ambulatory peritoneal dialysis

Background

Endotoxemia is exaggerated and contributes to systemic inflammation and atherosclerosis in patients requiring continuous ambulatory peritoneal dialysis (CAPD). The risk of mortality is substantially increased in patients requiring CAPD for >2 years. However, little is known about the effects of long-term CAPD on circulating endotoxin and cytokine levels. Therefore, the present study evaluated the associations between plasma endotoxin levels, cytokine levels, and clinical parameters with the effects of a short-dwell exchange on endotoxemia and cytokine levels in patients on long-term CAPD.

Methods

A total of 26 patients were enrolled and divided into two groups (short-term or long-term CAPD) according to the 2-year duration of CAPD. Plasma endotoxin and cytokine levels were measured before and after a short-dwell exchange (4-h dwell) during a peritoneal equilibration test (a standardized method to evaluate the solute transport function of peritoneal membrane). These data were analyzed to determine the relationship of circulating endotoxemia, cytokines and clinical characteristics between the two groups.

Results

Plasma endotoxin and monocyte chemotactic protein-1 (MCP-1) levels were significantly elevated in the long-term group. PD duration was significantly correlated with plasma endotoxin (r = 0.479, P = 0.016) and MCP-1 (r = 0.486, P = 0.012). PD duration was also independently associated with plasma MCP-1 levels in multivariate regression. Plasma MCP-1 levels tended to decrease (13.3% reduction, P = 0.077) though endotoxin levels did not decrease in the long-term PD group after the 4-h short-dwell exchange.

Conclusion

Long-term PD may result in exaggerated endotoxemia and elevated plasma MCP-1 levels. The duration of PD was significantly correlated with circulating endotoxin and MCP-1 levels, and was an independent predictor of plasma MCP-1 levels. Short-dwell exchange seemed to have favorable effects on circulating MCP-1 levels in patients on long-term PD.

Paricalcitol reduces peritoneal fibrosis in mice through the activation of regulatory T cells and reduction in IL-17 production

Fibrosis is a significant health problem associated with a chronic inflammatory reaction. The precise mechanisms involved in the fibrotic process are still poorly understood. However, given that inflammation is a major causative factor, immunomodulation is a possible therapeutic approach to reduce fibrosis. The vitamin D receptor (VDR) that is present in all hematopoietic cells has been associated with immunomodulation. We investigated whether the intraperitoneal administration of paricalcitol, a specific activator of the VDR, modulates peritoneal dialysis fluid (PDF)-induced peritoneal fibrosis. We characterized the inflammatory process in the peritoneal cavity of mice treated or not treated with paricalcitol and analyzed the ensuing fibrosis. The treatment reduced peritoneal IL-17 levels, which strongly correlated with a significantly lower peritoneal fibrotic response. In vitro studies demonstrate that both CD4⁺ and CD8⁺ regulatory T cells appear to impact the regulation of IL-17. Paricalcitol treatment resulted in a significantly increased frequency of CD8⁺ T cells showing a regulatory phenotype. The frequency of CD4⁺ Tregs tends to be increased, but it did not achieve statistical significance. However, paricalcitol treatment increased the number of CD4⁺ and CD8⁺ Treg cells in vivo. In conclusion, the activation of immunological regulatory mechanisms by VDR signaling could prevent or reduce fibrosis, as shown in peritoneal fibrosis induced by PDF exposure in mice.

The effect of biocompatible peritoneal dialysis solutions on neutrophil to lymphocyte ratio

INTRODUCTION

Long-term exposure to dialysis solutions is an important contributor to the ongoing inflammatory process in peritoneal dialysis (PD) patients. Some studies have shown amelioration of this adverse effect with biocompatible solutions. We aimed to compare the neutrophil-to-lymphocyte (N/L) ratio in PD patients using biocompatible and standard solutions and to find out the association between N/L ratio and peritonitis indices.

MATERIALS AND METHODS

This was a cross-sectional, multicenter study involving 120 prevalent PD patients. Seventy-one patients (59%) were using biocompatible solutions and 49 patients (41%) were using standard solutions. From blood samples, N/L ratio and platelet-to-lymphocyte ratio were calculated and mean platelet volume, erythrocyte sedimentation rate and hs-CRP values were detected. Data regarding the peritonitis rate and time to first peritonitis episode were also recorded.

RESULTS

Biocompatible and standard groups were similar regarding age and gender. N/L ratio and hs-CRP levels have been found significantly higher in patients using biocompatible solutions (3.75 ± 1.50 vs. 3.27 ± 1.3, p = 0.04 and 3.2 ± 2.5 vs. 1.8 ± 2.0, p < 0.01, respectively). Peritonitis rates and time to the first peritonitis episode were found similar in patients using both types of solutions (0.23 ± 0.35 vs. 0.27 ± 0.32, p = 0.36 and 32.8 ± 35.8 vs. 21.5 ± 26.9 months, p = 0.16, respectively).

DISCUSSION

N/L ratio was significantly higher in biocompatible solution users in parallel to hs-CRP levels, so biocompatible solutions seem to be related with increased inflammation in PD patients. Although we cannot make a certain explanation, we assume that there may be an association between acidity of the peritoneal content and virulence of microorganisms.

Clinical causes of inflammation in peritoneal dialysis patients

Inflammation at both systemic and local intraperitoneal levels commonly affects peritoneal dialysis (PD) patients. Interest in inflammatory markers as targets of therapeutic intervention has been considerable as they are recognised as predictors of poor clinical outcomes. However, prior to embarking on strategies to reduce inflammatory burden, it is of paramount importance to define the underlying processes that drive the chronic active inflammatory status. The present review aims to comprehensively describe clinical causes of inflammation in PD patients to which potential future strategies may be targeted.

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.

Dialysate interleukin-6 predicts increasing peritoneal solute transport rate in incident peritoneal dialysis patients

Background

Repeated exposure to peritoneal dialysis (PD) solutions contributes to cumulative intraperitoneal inflammation and peritoneal injury. The present study aimed to explore the capacity of dialysate interleukin-6(IL-6) to a) predict peritoneal membrane function and peritonitis in incident PD patients, and b) to evaluate the influence of neutral pH, low glucose degradation product (GDP) PD solution on dialysate IL-6 levels.

Methods

The study included 88 incident participants from the balANZ trial who had completed 24-months of follow-up. Change in peritoneal solute transport rate (PSTR) and peritonitis were primary outcome measures, and the utility of IL-6 and IL-6 appearance rate (IL-6 AR) in predicting these outcomes was analyzed using multilevel linear regression and Cox proportional hazards models, respectively. Sensitivity analyses were performed by analyzing outcomes in a peritonitis-free cohort (n = 56).

Results

Dialysate IL-6 concentration significantly increased from baseline to 24 months (mean difference 19.07 pg/mL; P < 0.001) but was not affected by the type of PD solution received (P = 0.68). An increase in PSTR from baseline was associated with higher levels of IL-6 (P = 0.004), the use of standard solutions (P = 0.005) and longer PD duration (P < 0.001). Baseline IL-6 level was not associated with a shorter time to first peritonitis (adjusted hazard ratio 1.00, 95% CI 0.99-1.00, P = 0.74). Analysis of IL-6 AR as well as sensitivity analyses in a peritonitis-free cohort yielded comparable results.

Conclusion

Dialysate IL-6 concentration increased with longer PD duration and was a significant, independent predictor of PSTR. The use of biocompatible PD solutions exerted no significant effect on dialysate IL-6 levels but did abrogate the increase in PSTR associated with standard PD solutions. This is the first study to examine the impact of biocompatible solutions on the utility of IL-6 in predicting PSTR and peritonitis.

Downregulation of nuclear-encoded genes of oxidative metabolism in dialyzed chronic kidney disease patients

Background

Mitochondria, essential eukaryotic cells organelles defined as the “powerhouse of the cell” because of their ability to produce the vast majority of energy necessary for cellular metabolism, may have a primary role in the oxidative stress-related intracellular machinery associated to chronic kidney disease (CKD).

Methods

To better assess this research assumption, we decided to study the key factors regulating mitochondrial oxidative metabolism in CKD patients in peritoneal dialysis (PD, n = 15) using several bio-molecular methodologies.

Results

RT-PCR experiments demonstrate that the expression level of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α) and nuclear respiratory factor-1 (NRF-1), two genes primarily involved in mitochondrial biogenesis and functions, were significantly hypo-expressed in peripheral blood mononuclear cells of PD patients compared to healthy subjects (HS, n = 15). Additionally, mRNA levels of several PGC1-α downstream target genes (TFAM, COX6C,COX7C, UQCRH and MCAD) were profoundly down-regulated in PD cells. TFAM protein analysis confirmed gene-expression results. High plasmatic concentration of Malondialdehyde found in PD patients, confirmed the contribution of the oxidative stress to these biological effects. Finally, Nuclear factor erythroid-derived 2-like 2 (NRF2 or NFE2L2), a transcription factor for numerous antioxidant/detoxifying enzymes and one of its target genes, superoxide dismutase-2 mitochondrial (SOD2) were up-regulated in PD compared to HS.

Conclusions

Our results revealed, for the first time, that CKD-PD patients’ PBMC, through a complex intracellular biochemical machinery, are able to modulate their mitochondrial functions probably in the attempt to reduce oxidative metabolic damage and to turn on a valuable defense cellular strategy against oxidative stress.

Association of biocompatible peritoneal dialysis solutions with peritonitis risk, treatment, and outcomes

BACKGROUND AND OBJECTIVES

The effect of biocompatible peritoneal dialysis (PD) solutions on PD-related peritonitis is unclear. This study sought to evaluate the relationship between use of biocompatible solutions and the probability of occurrence or clinical outcomes of peritonitis.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study included all incident Australian patients receiving PD between January 1, 2007, and December 31, 2010, using Australia and New Zealand Dialysis and Transplant Registry data. All multicompartment PD solutions of neutral pH were categorized as biocompatible solutions. The independent predictors of peritonitis and the use of biocompatible solutions were determined by multivariable, multilevel mixed-effects Poisson and logistic regression analysis, respectively. Sensitivity analyses, including propensity score matching, were performed.

RESULTS

Use of biocompatible solutions gradually declined (from 7.5% in 2007 to 4.2% in 2010), with preferential use among smaller units and among younger patients without diabetes mellitus. Treatment with biocompatible solution was associated with significantly greater overall rate of peritonitis (0.67 versus 0.47 episode per patient-year; incidence rate ratio, 1.49; 95% confidence interval [CI], 1.19 to 1.89) and with shorter time to first peritonitis (hazard ratio [HR], 1.48; 95% CI, 1.17 to 1.87), a finding replicated in propensity score-matched cohorts (HR, 1.36; 95% CI, 1.09 to 1.71).

CONCLUSIONS

In an observational registry study, use of biocompatible PD solutions was associated with higher overall peritonitis rates and shorter time to first peritonitis. Further randomized studies adequately powered for a primary peritonitis outcome are warranted.

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.

The effects of biocompatible compared with standard peritoneal dialysis solutions on peritonitis microbiology, treatment, and outcomes: the balANZ trial

BACKGROUND

A multicenter, multi-country randomized controlled trial (the balANZ study) recently reported that peritonitis rates significantly improved with the use of neutral-pH peritoneal dialysis (PD) solutions low in glucose degradation products ("biocompatible") compared with standard solutions. The present paper reports a secondary outcome analysis of the balANZ trial with respect to peritonitis microbiology, treatment, and outcomes.

METHODS

Adult incident PD patients with residual renal function were randomized to receive either biocompatible or conventional (control) PD solutions for 2 years.

RESULTS

The safety population analysis for peritonitis included 91 patients in each group. The unadjusted geometric mean peritonitis rates in those groups were 0.30 [95% confidence interval (CI): 0.22 to 0.41] episodes per patient-year for the biocompatible group and 0.49 (95% CI: 0.39 to 0.62) episodes per patient-year for the control group [incidence rate ratio (IRR): 0.61; 95% CI: 0.41 to 0.90; p = 0.01]. When specific causative organisms were examined, the rates of culture-negative, gram-positive, gram-negative, and polymicrobial peritonitis episodes were not significantly different between the biocompatible and control groups, although the biocompatible group did experience a significantly lower rate of non-pseudomonal gram-negative peritonitis (IRR: 0.41; 95% CI: 0.18 to 0.92; p = 0.03). Initial empiric antibiotic regimens were comparable between the groups. Biocompatible fluid use did not significantly reduce the risk of peritonitis-associated hospitalization (adjusted odds ratio: 0.80; 95% CI: 0.48 to 1.34), but did result in a shorter median duration of peritonitis-associated hospitalization (6 days vs 11 days, p = 0.05). Peritonitis severity was more likely to be rated as mild in the biocompatible group (37% vs 10%, p = 0.001). Overall peritonitis-associated technique failures and peritonitis-related deaths were comparable in the two groups.

CONCLUSIONS

Biocompatible PD fluid use was associated with a broad reduction in gram-positive, gram-negative, and culture-negative peritonitis that reached statistical significance for non-pseudomonal gram-negative organisms. Peritonitis hospitalization duration was shorter, and peritonitis severity was more commonly rated as mild in patients receiving biocompatible PD fluids, although other peritonitis outcomes were comparable between the groups.

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.

Influence of bicarbonate/low-GDP peritoneal dialysis fluid (BicaVera) on in vitro and ex vivo epithelial-to-mesenchymal transition of mesothelial cells

BACKGROUND

Peritoneal membrane damage induced by peritoneal dialysis (PD) is largely associated with epithelial-to-mesenchymal transition (EMT) of mesothelial cells (MCs), which is believed to be a result mainly of the glucose degradation products (GDPs) present in PD solutions.

OBJECTIVES

This study investigated the impact of bicarbonate-buffered, low-GDP PD solution (BicaVera: Fresenius Medical Care, Bad Homburg, Germany) on EMT of MCs in vitro and ex vivo.

METHODS

IN VITRO STUDIES

Omentum-derived MCs were incubated with lactate-buffered standard PD fluid or BicaVera fluid diluted 1:1 with culture medium. Ex vivo studies: From 31 patients randomly distributed to either standard or BicaVera solution and followed for 24 months, effluents were collected every 6 months for determination of EMT markers in effluent MCs.

RESULTS

Culturing of MCs with standard fluid in vitro resulted in morphology change to a non-epithelioid shape, with downregulation of E-cadherin (indicative of EMT) and strong induction of vascular endothelial growth factor (VEGF) expression. By contrast, in vitro exposure of MCs to bicarbonate/low-GDP solution had less impact on both EMT parameters. Ex vivo studies partially confirmed the foregoing results. The BicaVera group, with a higher prevalence of the non-epithelioid MC phenotype at baseline (for unknown reasons), showed a clear and significant trend to gain and maintain an epithelioid phenotype at medium- and longer-term and to show fewer fibrogenic characteristics. By contrast, the standard solution group demonstrated a progressive and significantly higher presence of the non-epithelioid phenotype. Compared with effluent MCs having an epithelioid phenotype, MCs with non-epithelioid morphology showed significantly lower levels of E-cadherin and greater levels of fibronectin and VEGF. In comparing the BicaVera and standard solution groups, MCs from the standard solution group showed significantly higher secretion of interleukin 8 and lower secretion of collagen I, but no differences in the levels of other EMT-associated molecules, including fibronectin, VEGF, E-cadherin, and transforming growth factor β1. Peritonitis incidence was similar in both groups. Functionally, the use of BicaVera fluid was associated with higher transport of small molecules and lower ultrafiltration capacity.

CONCLUSIONS

Effluent MCs grown ex vivo from patients treated with bicarbonate/low-GDP BicaVera fluid showed a trend to acquire an epithelial phenotype, with lower production of proinflammatory cytokines and chemokines (such as interleukin 8) than was seen with MCs from patients treated with a lactate-buffered standard PD solution.

Prevention of peritoneal dialysis-related infections

Despite substantial advances in peritoneal dialysis (PD) as a renal replacement modality, PD-related infection remains an important cause of morbidity, technique failure, and mortality. This review describes the microbiology and outcomes of PD peritonitis and catheter infection, followed by a discussion of several strategies that may reduce the risk of PD-related infections. Strategies that are reviewed include use of antibiotics at the time of PD catheter insertion, selection of PD catheter design and insertion technique, patient training, PD connectology, exit site prophylaxis, periprocedural prophylaxis, fungal prophylaxis, and choice of PD solutions.

Protective measures against ultrafiltration failure in peritoneal dialysis patients

Ultrafiltration failure in patients undergoing peritoneal dialysis is a condition with an incidence that increases over time. It is related to increased cardiovascular morbidity and mortality and is a major cause of the abandonment of the treatment technique. Because the number of patients undergoing renal replacement therapy is increasing with society aging and because approximately 10% of this population is treated with peritoneal dialysis, this matter is becoming more common in everyday practice for clinicians involved in the care of patients with chronic renal failure. In this review, we summarize the available measures used to prevent and treat ultrafiltration failure and the current state of research in the field, both in the experimental and clinical settings, focusing on the possible clinical applications of recent findings.

Peritoneal dialysis fluid bioincompatibility and new vessel formation promote leukocyte-endothelium interactions in a chronic rat model for peritoneal dialysis

Peritoneal dialysis (PD)-induced peritonitis leads to dysfunction of the peritoneal membrane. During peritonitis, neutrophils are recruited to the inflammation site by rolling along the endothelium, adhesion, and transmigration through vessel walls. In a rat PD-model, long-term effects of PD-fluids (PDF) on leukocyte-endothelium interactions and neutrophil migration were studied under baseline and inflammatory conditions. Rats received daily conventional-lactate-buffered PDF (Dianeal), bicarbonate/lactate-buffered PDF (Physioneal) or bicarbonate/lactate buffer (Buffer) during five weeks. Untreated rats served as control. Baseline leukocyte rolling and N-formylmethionyl-leucyl-phenylalanine (fMLP) induced levels of transmigration in the mesentery were evaluated and quantified by intra-vital videomicroscopy and immunohistochemistry. Baseline leukocyte rolling was unaffected by buffer treatment, approximately 2-fold increased after Physioneal and 4-7-fold after Dianeal treatment. After starting fMLP superfusion, transmigrated leukocytes appeared outside the venules firstly after Dianeal treatment (15 minutes), thereafter in Physioneal and Buffer groups (20-22 minutes), and finally in control rats (>25 minutes). Newly formed vessels and total number of transmigrated neutrophils were highest in Dianeal-treated animals, followed by Physioneal and Buffer, and lowest in control rats and correlated for all groups to baseline leukocyte rolling (r = 0.78, P < 0.003). This study indicates that the start of inflammatory neutrophil transmigration is related to PDF bio(in)compatibility, whereas over time neutrophil transmigration is determined by the degree of neo-angiogenesis.

Low immunogenicity allows Staphylococcus epidermidis to cause PD peritonitis

BACKGROUND

Peritonitis is a common and serious complication of peritoneal dialysis (PD). Coagulase-negative staphylococci from the patient's own skin flora are the most commonly found micro-organisms.

OBJECTIVE

In the present study we aim to elucidate the immune response in the early stage of infection and to clarify the importance of bacterial attachment to fibrinogen.

METHODS

Clinical Staphylococcus epidermidis isolates collected from PD peritonitis or the residential skin flora of healthy individuals were used to infect monocytes, macrophages, and peripheral blood mononuclear cells (PBMC) in the presence or absence of fibrinogen. The S. epidermidis strain HB (fbe(+)), expressing the fibrinogen-binding protein Fbe, and its isogenic mutant ST056 (fbe(-)) were used to study the impact of Fbe during cell infection. Immune induction was measured as interleukin-8 (IL-8) production determined by ELISA. Modulation of CD11b/CD18 expression in neutrophils incubated in conditioned medium from these experiments was analyzed in order to judge the cellular response.

RESULTS

S. epidermidis causing peritonitis was less immunogenic compared to strains belonging to the residential skin flora, as measured by IL-8 induction in monocytes and CD11b/CD18 expression in neutrophils. At low bacterial concentrations, attachment to fibrinogen was a prerequisite for an IL-8 induction in monocytes and PBMC. The fibrinogen-binding protein Fbe did not, however, influence immune induction under this condition.

CONCLUSIONS

We suggest that S. epidermidis strains may be able to cause clinical infection by evoking an inadequate immunological response in the early stage of infection. Bacterial attachment to fibrinogen is a relevant event during this phase but independent of the fibrinogen-binding protein Fbe.

Biocompatibility and Tolerability of a Purely Bicarbonate-Buffered Peritoneal Dialysis Solution

Background

Novel peritoneal dialysis solutions are characterized by a minimal content of glucose degradation products and a neutral pH. Many studies have shown the biocompatibility of neutral lactate-buffered solutions; however, until now, the effect of purely bicarbonate-buffered solutions has not been intensively studied in vivo.

Methods

This study was an open label, prospective, crossover multicenter trial to investigate the biocompatibility of a purely bicarbonate-buffered solution (bicPDF) by measuring biocompatibility parameters such as cancer antigen 125 (CA125) in peritoneal effluent. 55 patients were enrolled in the study. After a 2-week run-in phase, 53 patients could be randomized into 2 groups, starting with either standard lactate-buffered peritoneal dialysis fluid (SPDF) for 12 weeks (phase 1) and then switching to bicPDF for 12 weeks (phase 2), or vice versa. Overnight peritoneal effluents were collected at baseline and at the end of phases 1 and 2 and were tested for CA125, hyaluronic acid, vascular endothelial growth factor (VEGF), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), interferon gamma (IFNγ), and transforming growth factor-beta1 (TGF-β1). Total ultrafiltration and residual renal function were also assessed. At the end of the study, pain during fluid exchange and dwell was evaluated using special questionnaires.

Results

34 patients completed the study; 27 of them provided data for analysis of the biocompatibility parameters. CA125 levels in overnight effluent were significantly higher with bicPDF (61.9 ± 33.2 U/L) than with SPDF (18.6 ± 18.2 U/L, p < 0.001). Hyaluronic acid levels were significantly lower after the use of bicPDF (185.0 ± 119.6 ng/mL) than after SPDF (257.4 ± 174.0 ng/mL, p = 0.013). Both TNF-α and TGF-β1 showed higher levels with the use of bicPDF than with SPDF. No differences were observed for IL-6, VEGF, or IFNγ levels. We observed an improvement in the glomerular filtration rate with the use of bicPDF but no differences were observed for total fluid loss. Pain scores could be analyzed in 23 patients: there was no difference between the solutions.

Conclusions

The use of a purely bicarbonate-buffered low-glucose degradation product solution significantly changes most of the peritoneal effluent markers measured, suggesting an improvement in peritoneal membrane integrity. Additionally, it seems to have a positive effect on residual renal function.

Mortality and technique failure in peritoneal dialysis patients using advanced peritoneal dialysis solutions

BACKGROUND

Despite the theoretical benefits of biocompatible physiological-pH bicarbonate/lactate-buffered (B/L) peritoneal dialysis solution, there is only limited evidence supporting a superior clinical outcome associated with its use.

STUDY DESIGN

Observational study.

SETTINGS & PARTICIPANTS

2,163 patients starting peritoneal dialysis therapy between July 2003 and December 2006 from 54 centers in Korea were enrolled.

PREDICTORS

B/L solution and icodextrin use.

OUTCOMES

All-cause mortality and technique failure.

MEASUREMENTS

Patient outcomes were compared between patients prescribed B/L and conventional solutions by using propensity score and intention-to-treat analyses.

RESULTS

542 patients initiated peritoneal dialysis therapy with B/L solution, and 1,621, with conventional solution. Fifteen patients prescribed B/L solution switched to conventional solution, and 386 of those initially using conventional solution switched to B/L solution during follow-up. Propensity score matching yielded 542 matched pairs of patients. In the matched cohort, there were no significant differences in age, diabetes, cardiovascular comorbidity, socioeconomic status, icodextrin use, or center experience between the 2 groups. All-cause deaths occurred in 52 (9.6%) patients in the B/L-solution group compared with 102 (18.9%) in the conventional-solution group (hazard ratio [HR], 0.70; 95% confidence interval [CI], 0.50 to 0.98; P = 0.04). In addition, icodextrin use was significantly associated with a reduced risk of death (HR, 0.40; 95% CI, 0.28 to 0.58; P < 0.001). Thirty-three (6.1%) and 48 (8.9%) technique failures occurred in the B/L- and conventional-solution groups, respectively (HR, 0.91; 95% CI, 0.58 to 1.43; P = 0.7). The survival benefit of B/L solution persisted in the unmatched cohort (HR, 0.69; 95% CI, 0.52 to 0.93; P = 0.02).

LIMITATIONS

Retrospective analysis, lack of laboratory data, and unknown indications for use of B/L solution.

CONCLUSION

Use of a biocompatible B/L peritoneal dialysis solution with physiological pH is associated with improved survival compared with conventional solution. Large randomized clinical trials are warranted to confirm this finding.

Acute effects of peritoneal dialysis solutions in the mesenteric microcirculation

Long-term peritoneal dialysis induces morphological changes that may lead to gradual functional impairment of the peritoneal membrane. These changes are characterized by progressive reduction in solute transport or ultrafiltration failure. The mechanism of the peritoneal response to dialysis fluids has not yet been fully elucidated. We used video-microscopy for in vivo evaluation of microhemodynamics and peritoneal microvascular inflammatory response, after a single intraperitoneal exposure of rats to commercial PD fluids: (1) glucose 1.5 % PD solution; (2) lactate buffered glucose 4.25% PD solution; (3) Icodextrin 7%; (4) bicarbonate buffered glucose 3.86% PD fluid; and 5) Hanks solution. Sham-control groups were not injected. A 5-h exposure of the peritoneal membrane to glucose 1.5% PD solution or to Hanks solution did not induce a significant change in leukocyte rolling and adhesion. In contrast, PD solutions containing glucose 4.25% or Icodextrin 7.5% caused a significant 2-3-fold increase in leukocyte rolling (P < 0.001) and adhesion (P < 0.001) and a significant increase in venular blood flow velocity (P < 0.01) and shear rates (P < 0.05 for glucose 4.25%, and P < 0.01 for Icodextrin). Exposure to glucose 3.86% bicarbonate buffered (Physioneal) solution was associated with the lowest values of leukocyte rolling and adhesion among the PD solutions and with extremely higher venular flow velocities and shear rates. A single exposure to conventional PD solutions with a high concentration of glucose (4.25%) or polyglucose (Icodextrin 7.5%) induces changes consistent with an early peritoneal inflammatory response that may be attenuated by the use of bicarbonate-based fluids.

Conventional versus biocompatible peritoneal dialysis fluids: more questions than answers?

The most important challenge in peritoneal dialysis (PD) is long-term preservation of peritoneal membrane structure and function. Introduction of dialysis fluids into the peritoneal cavity induces changes. These changes are related to duration of dialysis, occurrence of peritonitis and components of the dialysis solution. Bioincompatibility is considered to be the major cause of the development of morphological changes of the peritoneal membrane. pH neutral PD fluids that are low in glucose degradation products (GDP) seem to better preserve the peritoneal membrane and have less systemic effects than the conventional ones. However, the long-term effects are not clear. An overview of the effects of conventional PD fluids and glucose-based PD fluids with neutral pH in ex vivo and in vivo animal and clinical studies is presented.

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.

Evolution of Antibiotic Resistance Mechanisms and their Relevance to Dialysis-Related Infections

As the survival of patients with end-stage renal failure has improved, their exposure to antibiotics has also increased. Infections, especially peritoneal dialysis–related peritonitis, are unavoidable because of lapses in technique and the slow worsening of systemic and peritoneal defense associated with aging and dialysis. The selective pressure inherent in the use of antibiotics shapes the pattern of antibiotic resistance in the bacteria causing peritonitis and extraperitoneal infections, and vice versa.

Renal function–preserving and non-ototoxic regimens that incorporate double β-lactams (first- and third-generation cephalosporins) for peritonitis have increased the selective pressure in favor of methicillin-resistant staphylococci (MRS) and extended-spectrum β-lactamase (ESBL)–producing Enterobacteriaceae. Attempts to use the fluoroquinolones as alternatives to β-lactams was met with rocketing quinolone resistance. The high incidence of MRS led many nephrologists to use empiric vancomycin—until the début of vancomycin-resistant enterococci. The recent emergence of heterogeneous and high-level vancomycin resistance in staphylococci (which are especially prevalent in patients on dialysis) calls for further prudence in the use of vancomycin.

The coming challenges are ESBL-producing Enterobacteriaceae with carbapenemase, multi-resistant Pseudomonas, and highly virulent community-acquired methicillin-resistant Staphylococcus aureus with Panton–Valentine leukocidin. Antibiotic auditing programs and meticulous patient training by nurses are the only available defense at the moment. Novel approaches such as antibiotic-impregnated Tenckhoff catheters, biocompatible dialysis fluid, and peritoneal immuno-augmentation strategies are eagerly awaited.

Impact of new dialysis solutions on peritonitis rates

Peritonitis remains a major cause of morbidity among patients on peritoneal dialysis (PD), yet there is little information about the effect of new biocompatible dialysis solutions on peritonitis rates and treatment. In our unit, information on each peritonitis episode is prospectively collected. Since 2003, bicarbonate/lactate dialysate has been gradually introduced for new patients and for patients experiencing abdominal pain with conventional lactate solutions. From 2002 to 2005, data from 121 episodes of peritonitis (71 automated PD and 50 continuous ambulatory PD) were analyzed; 107 episodes occurred in patients using standard lactate dialysate and 14 episodes in patients using bicarbonate/lactate solution. Patients using bicarbonate/lactate had a significantly lower peritonitis rate of 1 per 52.5 patient-months compared to those using standard lactate dialysate (1 per 26.9 patient-months) (P=0.0179). Response to treatment, however, was not affected by the type of dialysate; cure rates (71.4 and 69.1%, respectively) and recurrence rates (21.4 and 15.8%, respectively) were not significantly different. Catheter removal was required in three (21.4%) patients using bicarbonate/lactate and 23 (22.4%) patients using lactate solution. Use of biocompatible dialysate appears to reduce the peritonitis rate by 50%, although this has to be confirmed in a randomized study. The type of dialysate, on the other hand, does not affect response to treatment.

Decreased leukocyte recruitment in the mesenteric microcirculation of rats with cirrhosis is partially restored by treatment with peginterferon: an in vivo study

BACKGROUND/AIMS

Patients with liver cirrhosis are predisposed to develop bacterial infections. An essential process in inflammatory responses is the recruitment of circulating leukocytes through the activation of adhesion molecules. Interferon-alpha2a is a cytokine reported to influence the expression of adhesion molecules. We investigated the effect of peginterferon-alpha2a (PegIFN-alpha(2a)) in vivo on the leukocyte recruitment in the mesenteric microcirculation of cirrhotic rats after lipopolysaccharide exposure.

METHODS

Leukocyte rolling, adhesion and extravasation were visualized by intravital microscopy in sham-operated and common bile duct ligated (CBDL) rats. PegIFN-alpha(2a) was administered to influence leukocyte recruitment. Endothelial P-selectin, E-selectin and ICAM-1 expression were studied by immunohistochemistry.

RESULTS

CBDL placebo rats showed significantly impaired rolling, adhesion and extravasation of leukocytes compared to Sham-operated placebo rats. Endothelial P-selectin, E-selectin and ICAM-1 expressions in CBDL placebo rats were significantly reduced compared to Sham-operated placebo rats. PegIFN-alpha(2a) 18 microg normalized number of rolling leukocytes in CBDL rats, without influencing on adhering and extravasated leukocytes. PegIFN-alpha(2a) upregulates the expression of P-selectin and E-selectin in CBDL rats, but ICAM-1 expression remained significantly lower than in Sham rats.

CONCLUSIONS

Leukocyte recruitment is significantly impaired in the mesenteric microcirculation of cirrhotic rats. This deficiency appears to result from a reduced endothelial P-selectin, E-selectin and ICAM-1 expression. Peginterferon-alpha(2a) treatment normalizes rolling of leukocytes in cirrhotic rats by upregulation of P-selectin and E-selectin expressions, but has no influence on adhesion and extravasation possibly due to the absence of effect on ICAM-1 expression.

Peritoneal mast cells in peritoneal dialysis patients, particularly in encapsulating peritoneal sclerosis patients

BACKGROUND

We assumed that increased mast cell numbers contribute substantially to the fibrosis often seen in the peritoneum of peritoneal dialysis (PD) patients, particularly those with encapsulating peritoneal fibrosis (EPS). Therefore, we investigated mast cells in different pathological conditions of the peritoneum.

METHODS

One hundred fifteen tissue probes with different peritoneal pathological states were selected (normal, n = 20; chronic appendicitis, n = 25; herniotomy, n = 24; fibrosis, n = 11; PD, n = 26; and EPS, n = 9). For staining of mast cells, we used alpha-naphtol-AS-d-chloracetate-esterase and mast cell tryptase. Next, we counted numbers of mast cells per square millimeter. Tryptase was measured by using image analysis.

RESULTS

Measurements by means of both methods correlated well (r = 0.812). Numbers of mast cells per square millimeter were as follows: normal, 26 +/- 16; chronic appendicitis, 241 +/- 217; herniotomy, 115 +/- 88; fibrosis, 99 +/- 66; PD, 81 +/- 64, and EPS, 24 +/- 23 (P = 0.00006). Amounts of tryptase present were 2.900 +/- 0.118, 2.871 +/- 0.150, 2.733 +/- 0.183, 3.041 +/- 0.176, 2.780 +/- 0.184, and 2.609 +/- 0.234, respectively (P = 0.00002).

CONCLUSION

We found upregulation of mast cells in specimens of chronic inflammatory diseases of the peritoneum. This also was true for PD patients, with the exclusion of patients with EPS. Therefore, loss-of-control functions of mast cells may contribute to the ill-understood disease entity of EPS.