Treatment of malnutrition with 1.1% amino acid peritoneal dialysis solution: results of a multicenter outpatient study

Rationale and design of ELIXIR, a randomized, controlled trial to evaluate efficacy and safety of XyloCore, a glucose-sparing solution for peritoneal dialysis

Peritoneal dialysis adoption and technique survival is affected by limitations related to peritoneal membrane longevity and metabolic alterations. Indeed, almost all peritoneal dialysis fluids exploit glucose as an osmotic agent that rapidly diffuses across the peritoneal membrane, potentially resulting in metabolic abnormalities such as hyperglycemia, hyperinsulinemia, obesity, and hyperlipidemia. Moreover, glucose-degradation products generated during heat sterilization, other than glucose itself, induce significant morphological and functional changes in the peritoneum leading to ultrafiltration failure. The partial substitution of glucose with osmotic agents characterized by a better local and systemic biocompatibility has been suggested as a potential strategy to innovate peritoneal dialysis fluids. The approach aims to minimize glucose-associated toxicity, preserving the peritoneal membrane welfare and counteracting common comorbidities. In this work, we report the clinical trial design of ELIXIR, a phase III randomized, controlled, blinded outcome assessment study comparing Xylocore®, an innovative formulation based on Xylitol and l-carnitine, to standard glucose-based regimens, in end-stage kidney disease patients treated with continuous ambulatory peritoneal dialysis; 170 patients will be randomized (1:1) to receive XyloCore® or to continue their pre-randomization peritoneal dialysis (PD) therapy with glucose-only PD solutions, for 6 months. The primary study's objective is to demonstrate the noninferiority of XyloCore® in terms of Kt/V urea, for which a clinically acceptable noninferiority margin of -0.25 has been determined, assuming that all patients will be treated aiming to a minimum target of 1.7 and an optimal target of 2.0.

Characteristics and outcomes of hospital-acquired and community-acquired peritonitis in patients on peritoneal dialysis: a retrospective cohort study

BACKGROUND

Peritonitis remains a significant complication of peritoneal dialysis. However, there is limited information on the clinical characteristics and outcomes of hospital-acquired peritonitis compared to community-acquired peritonitis in patients undergoing peritoneal dialysis. Furthermore, the microbiology and outcomes of community-acquired peritonitis may vary from hospital-acquired peritonitis. Therefore, the aim was to gather and analyse data to address this gap.

METHODS

Retrospective review of the medical records of all adult patients on peritoneal dialysis within the peritoneal dialysis units in four university teaching hospitals in Sydney, Australia, who developed peritonitis between January 2010 and November 2020. We compared the clinical characteristics, microbiology and outcomes of community-acquired peritonitis and hospital-acquired peritonitis. Community acquired peritonitis was defined as the development of peritonitis in the outpatient setting. Hospital-acquired peritonitis was defined as: (1) developed peritonitis anytime during hospitalisation for any medical condition other than peritonitis, (2) diagnosed with peritonitis within 7 days of hospital discharge and developed symptoms of peritonitis within 3 days of the hospital discharge.

RESULTS

Overall, 904 episodes of peritoneal dialysis-associated peritonitis were identified in 472 patients, of which 84 (9.3%) episodes were hospital-acquired. Patients with hospital-acquired peritonitis had lower mean serum albumin levels compared to those with community-acquired peritonitis(22.95 g/L vs. 25.76 g/L, p = 0.002). At the time of diagnosis, lower median peritoneal effluent leucocyte and polymorph counts were observed with hospital-acquired peritonitis compared to community-acquired peritonitis (1236.00/mm3 vs. 3183.50/mm3, p < 0.01 and 1037.00/mm3 vs. 2800.00/mm3, p < 0.01, respectively). Higher proportions of peritonitis due to Pseudomonas spp. (9.5% vs. 3.7%, p = 0.020) and vancomycin-resistant Enterococcus (2.4% vs. 0.0%, p = 0.009), lower rates of complete cure (39.3% vs. 61.7%, p < 0.001), higher rates of refractory peritonitis (39.3% vs. 16.4%, p < 0.001) and higher all-cause mortality within 30 days of peritonitis diagnosis (28.6% vs. 3.3%, p < 0.001) were observed in the hospital-acquired peritonitis group compared to the community-acquired peritonitis group, respectively.

CONCLUSIONS

Despite having lower peritoneal dialysis effluent leucocyte counts at the time of diagnosis, patients with hospital-acquired peritonitis had poorer outcomes, including lower rates of complete cure, higher rates of refractory peritonitis and higher rates of all-cause mortality within 30 days of diagnosis, compared to those with community-acquired peritonitis.

The impact of amino acid dialysate on anthropometric measures in adult patients on peritoneal dialysis: A systematic review and meta-analysis

BACKGROUND

Glucose-containing dialysate underpins peritoneal dialysis (PD) therapy. However, its use is associated with amino acid loss in the dialysis effluent, a risk factor for protein-energy wasting (PEW) in PD patients. Amino acid-based dialysis solutions (AAD) may ameliorate this loss. However, the evidence of clinical benefit in preventing PEW is unclear. The aim of this review was to assess the effect of AAD versus standard dialysis solutions (STD) on anthropometric measures and serum albumin.

METHODS

Studies up until 30 September 2020 were identified from databases including MEDLINE and Embase, using a prespecified protocol (PROSPERO - CRD42020209581). Studies evaluating adults on PD were included. Data pertaining to muscle mass (primary outcome), other anthropometric measures and serum albumin were extracted. A meta-analysis of the eligible studies was conducted.

RESULTS

A total of 6945 abstracts were reviewed, from which 14 studies (9 randomised and 5 non-randomised) were included. There was no significant difference in any of the anthropometric measures, between AAD and STD during follow-up. Serum albumin at 6 months was statistically lower with AAD compared to STD [mean difference = -0.89 (95%CI -1.77 to -0.01, p = 0.046)]. The quality of evidence was graded low for each outcome.

CONCLUSIONS

AAD may not alter anthropometric measures when compared to STD. The impact on serum albumin is uncertain, with an estimated difference that is unlikely to be of clinical value. These findings should be cautiously interpreted due to low quality of the evidence. Robust studies are needed to address the limitations in evidence.

Fibrosis of Peritoneal Membrane as Target of New Therapies in Peritoneal Dialysis

Peritoneal dialysis (PD) is an efficient renal replacement therapy for patients with end-stage renal disease. Even if it ensures an outcome equivalent to hemodialysis and a better quality of life, in the long-term, PD is associated with the development of peritoneal fibrosis and the consequents patient morbidity and PD technique failure. This unfavorable effect is mostly due to the bio-incompatibility of PD solution (mainly based on high glucose concentration). In the present review, we described the mechanisms and the signaling pathway that governs peritoneal fibrosis, epithelial to mesenchymal transition of mesothelial cells, and angiogenesis. Lastly, we summarize the present and future strategies for developing more biocompatible PD solutions.

How to Improve the Biocompatibility of Peritoneal Dialysis Solutions (without Jeopardizing the Patient's Health)

Peritoneal dialysis (PD) is an important, if underprescribed, modality for the treatment of patients with end-stage kidney disease. Among the barriers to its wider use are the deleterious effects of currently commercially available glucose-based PD solutions on the morphological integrity and function of the peritoneal membrane due to fibrosis. This is primarily driven by hyperglycaemia due to its effects, through multiple cytokine and transcription factor signalling-and their metabolic sequelae-on the synthesis of collagen and other extracellular membrane components. In this review, we outline these interactions and explore how novel PD solution formulations are aimed at utilizing this knowledge to minimise the complications associated with fibrosis, while maintaining adequate rates of ultrafiltration across the peritoneal membrane and preservation of patient urinary volumes. We discuss the development of a new generation of reduced-glucose PD solutions that employ a variety of osmotically active constituents and highlight the biochemical rationale underlying optimization of oxidative metabolism within the peritoneal membrane. They are aimed at achieving optimal clinical outcomes and improving the whole-body metabolic profile of patients, particularly those who are glucose-intolerant, insulin-resistant, or diabetic, and for whom daily exposure to high doses of glucose is contraindicated.

Chronic Kidney Disease and Nutrition Support

Individuals with chronic kidney disease (CKD), particularly those undergoing maintenance dialysis, are prone to protein-energy wasting (PEW), the latter of which can be ameliorated with different methods of nutrition support. Dietary counseling guided by dietitians is the key for preventing and managing PEW in CKD. If dietary counseling per se fails to meet the recommended energy and protein requirements, the addition of oral nutrition supplements (ONSs) would be necessary. When these initial measures cannot attain the recommended energy and protein requirements, nutrition support, including enteral tube feeding or parenteral nutrition (PN), should be considered as a viable option to improve nutrition status. Partial PN, comprising intraperitoneal PN (IPPN) and intradialytic PN (IDPN) therapies, may be attempted as supplemental nutrition support in patients with PEW requiring peritoneal dialysis and hemodialysis, respectively. Despite the debatable effectiveness of IPPN for patients undergoing peritoneal dialysis, it remains a feasible means in these patients. The indications for IPPN in patients undergoing peritoneal dialysis include inadequate dietary intake of energy and protein, and barriers of oral intake and other forms of enteral supplementation such as issues with suitability, tolerance, and compliance. Nonetheless, in the case of spontaneous dietary consumption of energy and protein meeting the difference between the IDPN provision and the nutrition targets, the use of IDPN is rational. In patients with PEW and malfunctioning gastrointestinal tract, as well as those whose enteral intake (with or without partial PN) is below the recommended nutrient requirements, total PN becomes a relevant nutrition intervention.

A New Peritoneal Dialysis Solution Containing L-Carnitine and Xylitol for Patients on Continuous Ambulatory Peritoneal Dialysis: First Clinical Experience

Peritoneal dialysis (PD) is a feasible and effective renal replacement therapy (RRT) thanks to the dialytic properties of the peritoneal membrane (PM). Preservation of PM integrity and transport function is the key to the success of PD therapy, particularly in the long term, since the prolonged exposure to unphysiological hypertonic glucose-based PD solutions in current use is detrimental to the PM, with progressive loss of peritoneal ultrafiltration capacity causing technique failure. Moreover, absorbing too much glucose intraperitoneally from the dialysate may give rise to a number of systemic metabolic effects. Here we report the preliminary results of the first clinical experience based on the use in continuous ambulatory PD (CAPD) patients of novel PD solutions obtained through partly replacing the glucose load with other osmotically active metabolites, such as L-carnitine and xylitol. Ten CAPD patients were treated for four weeks with the new solutions. There was good tolerance to the experimental PD solutions, and no adverse safety signals were observed. Parameters of dialysis efficiency including creatinine clearance and urea Kt/V proved to be stable as well as fluid status, diuresis, and total peritoneal ultrafiltration. The promising tolerance and local/systemic advantages of using L-carnitine and xylitol in the PD solution merit further research.

KDOQI US Commentary on the 2020 ISPD Practice Recommendations for Prescribing High-Quality Goal-Directed Peritoneal Dialysis

The recently published 2020 International Society for Peritoneal Dialysis (ISPD) practice recommendations regarding prescription of high-quality goal-directed peritoneal dialysis differ fundamentally from previous guidelines that focused on "adequacy" of dialysis. The new ISPD publication emphasizes the need for a person-centered approach with shared decision making between the individual performing peritoneal dialysis and the clinical care team while taking a broader view of the various issues faced by that individual. Cognizant of the lack of strong evidence for the recommendations made, they are labeled as "practice points" rather than being graded numerically. This commentary presents the views of a work group convened by the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) to assess these recommendations and assist clinical providers in the United States in interpreting and implementing them. This will require changes to the current clinical paradigm, including greater resource allocation to allow for enhanced services that provide a more holistic and person-centered assessment of the quality of dialysis delivered.

Treatment Targets for Diabetic Patients on Peritoneal Dialysis: Any Evidence?

Diabetic patients are often affected by comorbid conditions that influence clinical outcome. Taking care of diabetic peritoneal dialysis (PD) patients is a challenge for nephrologists, not only because these patients have more complications and comorbidities, but also because of their difficulties in maintaining glycemic control with the use of current glucose-containing dialysis solutions. In addition, the increased transport of small molecules and proteins by the peritoneal membrane in diabetic patients adds the further problems of ultrafiltration deficit and malnutrition. The present article reviews pertinent evidence toward establishing the best strategy for the care of diabetic PD patients. With better glycemic control, improved nutrition, improved fluid balance, and optimal preservation of residual renal function, there is hope for improving the survival of diabetic PD patients.

Studying the Effects of New Peritoneal Dialysis Solutions on the Peritoneum

♦ Background

Compelling data underscore the bioincompatible nature of glucose-based peritoneal dialysis (PD) solutions and their detrimental effects on peritoneal physiology and morphology. New PD solutions have been formulated to tackle common clinical problems such as inadequate ultrafiltration or malnutrition, and to improve biocompatibility—the latter aimed at preserving the structural and functional integrity of the peritoneum and reducing adverse systemic effects on the patient.

♦ Methods

This article reviews the factors in PD fluids that alter normal peritoneal anatomy and physiology, and the data that illustrate approaches to investigating the local and systemic biocompatibility of new PD solutions.

♦ Results

Chronic exposure of the peritoneal membrane to glucose-based PD solutions results in denudation of the mesothelium, thickened submesothelium, and hyalinization of the vasculature, often resulting in reduced or lost solute and water clearance. Data from in vitro or animal experiments and clinical studies have shown improved bio-compatibility profiles with new PD solutions that are glucose-free (that is, dialysates with amino acids or icodextrin), bicarbonate-buffered, or compartmentalized during heat sterilization to reduce levels of glucose degradation products. Improved biocompatibility is denoted by reduced induction of proinflammatory, profibrotic, or angiogenic growth factors in mesothelial cells and macrophages, or by less perturbation of leukocyte phagocytic function.

♦ Conclusions

Data from in vitro and animal experiments show more favorable biocompatibility profiles with new PD fluids than with glucose-based dialysates. Clinical studies are ongoing to assess the impact of the new PD fluids on peritoneal function, morbidity, and mortality.

Identifying and Managing Malnutrition Stemming from Different Causes

Protein–energy malnutrition (PEM) is highly prevalent among peritoneal dialysis (PD) patients and is a strong predictor of morbidity and mortality. A wide range of factors can lead to PEM and associated wasting (PEM/W) in PD patients, but persistent inflammation and the presence of diabetes have been identified as the two main reasons. An important body of literature has been reporting studies of methods suitable for detecting malnutrition in its early phase so that appropriate intervention can be provided. Although assessment of nutrition status has been substantially improved, no definitive single method of assessing nutrition status has been decided. Rather, several different markers of nutrition should be evaluated together. Because of the complexity of treating malnutrition in PD patients, nontraditional strategies such as appetite stimulants, anti-inflammatory diets, and anti-inflammatory pharmacologic agents are recommended to be combined with more traditional forms of nutritional support, so as to provide a better chance of recovery. The present review briefly discusses the causes of PEM/W, the methods most commonly used to identify the condition, and the new management strategies available.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Risk Factors Responsible for Ultrafiltration Failure in Early Stages of Peritoneal Dialysis

Objective

To define risk factors for ultrafiltration failure (UFF) during early stages of peritoneal dialysis (PD).

Design

Retrospective analysis of a group of patients whose peritoneal function was prospectively followed.

Setting

A tertiary-care public university hospital.

Patients

Nineteen of 90 long-term PD patients required a peritoneal resting period to recover UF capacity: 8 had this requirement before the third year on PD (early, EUFF group) and 11 had a late requirement (LUFF group). The remaining 71 patients, those with stable peritoneal function over time, constituted the control group.

Main Outcome Measures

Peritoneal UF capacity under standard conditions (monthly) and small solute peritoneal transport (yearly).

Results

None of the conditions appearing at the start of PD or during the observation period could be definitely identified as the cause of UFF. There were no differences in characteristics between the EUFF group and the other two groups, except for the higher prevalence of diabetes in the EUFF group. Residual renal function (RRF) declined in all three groups during the first 2 years, with rapid loss during the third year in the EUFF group. This rapid loss in RRF was coincident with UFF. Peritoneal solute and water transport at baseline was similar in the three groups. After 2 years on PD, individuals in the EUFF group showed a significantly lower UF and higher creatinine mass transfer coefficient values than those in the LUFF group. Diabetic patients in the control group showed remarkable stability in UF capacity over time. During the second year on PD, requirement for increases in dialysate glucose concentration was 3.4 ± 0.5% in the LUFF group, but as high as 25.5 ± 24.2% in the EUFF group. The accumulated days of active peritonitis (APID, days with cloudy effluent) were similar for the three groups after 1, 2, and 3 years on PD. Interestingly, diabetic patients in the control group showed an APID index significantly lower than the overall EUFF group. Diabetics in the control group also had significantly lower APID versus nondiabetics in the control group ( p = 0.016).

Conclusions

Our findings suggest that certain patients develop early UFF type I. Diabetic state and a higher glucose requirement to obtain adequate UF suggest that glucose on both sides of the peritoneal membrane could be responsible. The mechanisms for this higher requirement remain to be elucidated. The identification of a larger cohort of these early UFF patients should lead to a better exploration of the primary pathogenic mechanisms.

Effects of Conventional and New Peritoneal Dialysis Solutions on Human Peritoneal Mesothelial Cell Viability and Proliferation

Objective

To investigate the biocompatibility of “new” peritoneal dialysis (PD) solutions with bicarbonate/lactate buffer, non glucose osmotic agents (icodextrin or amino acids), neutral pH, and low levels of glucose degradation products (GDPs).

Design

Using M199 culture medium as a control, we compared conventional and new PD solutions with respect to their effects on the viability of human peritoneal mesothelial cells (HPMCs) [using lactate dehydrogenase (LDH) release], on DNA damage in HPMCs [using single-cell gel electrophoresis (Comet assay)], and on HPMC proliferation (using [3H]-thymidine incorporation). The experiments were performed after cell growth was synchronized by incubation with serum-free media for 24 hours. The PD solutions tested included commercial 1.5% glucose and 4.25% glucose solutions with 40 mmol/L lactate (D 1.5 and D 4.25, respectively), 7.5% icodextrin (E), 1.1% amino acid (N), 1.5% glucose solution in a triple-chambered bag (Bio 1.5), 1.5% glucose solution in a dual-chambered bag with neutral pH (Bal 1.5), and 1.5% glucose and 4.25% glucose solution containing 25 mmol/L bicarbonate and 15 mmol/L lactate (P 1.5 and P 4.25, respectively).

Results

When HPMCs were continuously exposed to undiluted PD solutions, D 1.5, D 4.25, P 4.25, and E increased LDH release by more than 60% at 24 hours. All PD solutions tested increased LDH release by more than 75% at 96 hours. With 2-fold diluted PD solutions, only D 4.25 significantly increased LDH release at 96 hours, though not at 24 hours. When cells were exposed to undiluted PD solutions for 60 min and allowed to recover in M199 for up to 96 hours, LDH release was significantly higher at 24 – 96 hours in E (55% – 69%) and D 1.5 (48% –72%) as compared with control [M199 (18%)]. Release of LDH was significantly lower with PD solutions containing lower levels of GDPs than those in D 1.5, suggesting that GDPs may have a role in cell viability. The D solutions (D 1.5 and D 4.25) and E solution also induced significant DNA damage. Both LDH release and DNA damage by D and E were significantly attenuated by adjusting the solution pH to 7.4, suggesting that low pH may be implicated in PD solution–induced DNA damage and cell death. When diluted 2-fold, D 1.5, D 4.25, and P 4.25 decreased [3H]-thymidine incorporation to 43%, 34%, and 41% of control, respectively, at 24 hours and to 45%, 26%, and 35% of control, respectively, at 96 hours. When cells were exposed to undiluted PD solutions for 5 minutes and allowed to recover in M199 for up to 96 hours, D 1.5 and P 4.25—but not D 4.25—significantly inhibited cell proliferation at 24 hours. This effect was sustained up to 96 hours.

Conclusions

The present in vitro data demonstrate that PD solutions with low pH, or high levels of GDPs, or both, promote HPMC death and DNA damage, and that PD solutions with high osmolality inhibit cell proliferation. Solutions with neutral pH, amino acids, and “low GDPs” appear to be more biocompatible than conventional PD solutions. These results require confirmation in in vivo animal and clinical studies.

The Choice of Dialysis Solutions in Pediatric Chronic Peritoneal Dialysis: Guidelines by AnAD HOCEuropean Committee

Objective

To provide guidelines on choosing dialysis solutions for children on chronic peritoneal dialysis (PD).

Setting

European Paediatric Peritoneal Dialysis Working Group.

Data Source

Literature on the application of PD solutions in children ( Evidence), and discussions within the group ( Opinion).

Conclusions

Glucose is the standard osmotic agent for PD in children ( Evidence). The lowest glucose concentration needed should be used ( Opinion). Low calcium solution (1.25 mmol/L) should be applied, wherever possible, with careful monitoring of parathyroid hormone levels ( Opinion). The use of amino acid-containing dialysis fluids can be considered in malnourished children, although aggressive enteral nutrition is preferred ( Opinion). There is insufficient evidence documenting the efficacy of intraperitoneally administered amino acids ( Evidence). When ultrafiltration and/or solute removal are insufficient, poly-glucose solutions are a welcome addition to the treatment of children on nocturnal intermittent PD ( Evidence). However, in the absence of any reported long-term experience with children, their use must be closely monitored ( Opinion). Bicarbonate would appear to be the preferred buffer for PD in children, but more in vivo studies are required before it replaces the present lactate-containing solutions ( Evidence/Opinion).

Preventing Peritoneal Fibrosis—Insights from the Laboratory

Objective

Peritoneal fibrosis is one of the most serious complications of peritoneal dialysis (PD). Peritoneal fibrosis is characterized by activation of the peritoneal resident cells, accumulation and deposition of excess matrix proteins within the interstitium, and neoangiogenesis and vasculopathy of the peritoneal microvasculature. Compelling evidence now exists to show that elevated glucose concentrations present as the osmotic agent in PD solutions are, per se, responsible for those detrimental changes. Until alternative osmotic agents can fully replace glucose in PD solutions, novel therapeutic strategies are essential to preserve the structural and functional properties of the peritoneum. This review highlights recent experimental data that may offer potential strategies for preservation of the peritoneal structure and improvement of clinical outcome.

Method

Literature review.

Results

Compelling evidence now exists to show that the bioincompatible nature of PD solutions—in particular, elevated glucose concentrations and glucose byproducts—play a pivotal role in the initiation of peritoneal fibrosis. Animal and in vitro studies provide some insight into methods that can potentially be employed to alleviate or retard peritoneal fibrosis. Those methods include use of alterative osmotic agents (polyglucose or amino acids), administration of TGFβ1 antagonists, gene therapy, and pharmacologic interventions.

Conclusions

Knowledge of the pathogenesis of peritoneal fibrosis has allowed independent researchers to design therapeutic strategies that abrogate excess matrix synthesis and deposition in cultured peritoneal cells and in animal models of experimental peritoneal fibrosis alike. Encouraging results have been obtained in those studies, but it remains to be determined whether the studied strategies can alleviate clinical disease. Future studies will enable us to establish specific molecules that can be targeted clinically to restrict the progressive deterioration of the peritoneal membrane as a biologic dialyzing organ.

Biocompatibility of New Peritoneal Dialysis Solutions: What Can We Hope to Achieve?

Despite the bioincompatibility of the “old”, standard, high glucose, lactate-buffered peritoneal dialysis (PD) solutions, PD is itself a highly successful dialysis modality with patient survival equivalent to that of hemodialysis (HD) during the initial 3 – 5 years of dialysis therapy. Nevertheless, PD technique survival is often limited by infectious complications and alterations in the structure and function of the peritoneal membrane. These local changes also have a negative impact on patient survival owing to systemic effects such as those often seen in patients with high peritoneal transport rate and loss of ultrafiltration (UF) capacity.

Patient mortality remains unacceptably high in both HD and PD patients, with most premature deaths being associated with signs of malnutrition, inflammation, and atherosclerotic cardiovascular disease (MIA syndrome). These systemic signs are likely to be influenced by PD solutions both directly and indirectly (via changes in the peritoneal membrane). New, biocompatible PD solutions may have favorable local effects (viability and function of the peritoneal membrane) and systemic effects (for example, on MIA syndrome). Amino acid–based solution [Nutrineal (N): Baxter Healthcare Corporation, Deerfield, IL, U.S.A.] may improve nutritional status as well as peritoneal membrane viability. Bicarbonate/lactate–buffered solution [Physioneal (P): Baxter Healthcare Corporation] may ameliorate local and systemic effects of low pH, high lactate, and high glucose degradation products. Icodextrin-based solution [Extraneal (E): Baxter Healthcare SA, Castlebar, Ireland] may improve hypertension and cardiovascular problems associated with fluid overload and may extend time on therapy in patients with loss of UF capacity.

The positive effects of each of these new, biocompatible solutions have been demonstrated in several studies. It is likely that the combined use of N, P, and E solutions will produce favorable synergies in regard to both local effects (peritoneal viability) and systemic effects (less malnutrition, inflammation, and fluid overload). Solution combination is an exciting area for clinical study in the coming years. Furthermore, dialysis fluid additives such as hyaluronan, which protects and improves the function of the peritoneal membrane, may further improve PD solutions. The new, biocompatible PD solutions represent an entirely new era in the evolution of the PD therapy; they are likely to have markedly positive effects on both PD technique and PD patient survival in coming years.

A Randomized Clinical Trial with a 0.6% Amino Acid/1.4% Glycerol Peritoneal Dialysis Solution

Background

Glucose is an accepted osmotic agent for peritoneal dialysis (PD) although it has several drawbacks. Some of these drawbacks have been addressed by the introduction of solutions with low glucose degradation products and physiological pH in dual-chambered bags. Despite this achievement, there is a need for alternative osmotic agents. This randomized clinical trial analyzes 3-month's clinical experience with a mixture of 0.6% amino acids and 1.4% glycerol.

Methods

The study was performed at the renal units of the University Hospitals Ghent, Belgium, and Utrecht, The Netherlands. Stable PD patients were randomized for either protocol A (test solution, n = 5) or protocol B (control regimen, n = 5). In both protocols, there was a run-in phase of 1 month with a dialysis regimen of 2 × 2 L 2.27% glucose solution (Dianeal; Baxter, Nivelles, Belgium), 1 × 2 L Extraneal (Baxter), and 1 × 2 L glucose solution (Dianeal). After this month-long run-in period, patients in group A received during 3 months 2 × 2 L amino acid/glycerol solution, 1 × 2 L Extraneal, and at least 1 × 2 L of a classic glucose solution.

Results

Glucose absorption decreased in the test group during the test phase (from 84.2 ± 8.7 to 11.7 ± 11.6 g/24 hours, p = 0.001). Dialysate levels of cancer antigen 125 (CA125) increased in the test group, from 17.5 ± 11.0 to 32.4 ± 4.6 units/L ( p = 0.04), whereas, in the control group, the levels remained stable (15.5 ± 8.7 and 14.9 ± 9.8 units/L respectively, p = 0.4). There were no differences in serum urea, serum bicarbonate, serum osmolarity, serum albumin, or parameters related to skin-fold thickness or serum glycerol levels between control and test solutions. No differences were observed in obtained ultrafiltration after a 4-hour dwell with 2.27% glucose or the test solution, both measured at week 4 of the run-in period and week 12 of the test period.

Conclusion

This study demonstrated that the use of a new 0.6% amino acid/1.4% glycerol-containing dialysis solution is safe and well tolerated. Glucose load was reduced significantly and dialysate CA125 levels improved significantly. Ultrafiltration was comparable with that of a 2.27% glucose solution. All these factors, in combination with the potential nutritional benefits, can contribute to a beneficial impact on the success of the PD technique. Further long-term studies in larger patient groups are warranted to explore the potential of this promising new solution.

Biocompatibility of New Peritoneal Dialysis Solutions: Clinical Experience

The successful development of peritoneal dialysis (PD) during the last two decades has been made possible by using well-established glucose-based solutions with lactate as buffer. On the other hand, awareness has been increasing about the potentially negative effects of the high concentrations of glucose and lactate, and the low pH of conventional PD solutions. This awareness has prompted an intensive effort to search for and test alternative solutions.

As a result, three new, more biocompatible solutions— containing either less glucose or less lactate—are available. Amino acid–based solution uses amino acids instead of glucose as the osmotic agent; it is indicated for treatment of malnutrition. The higher pH and absence of glucose in this solution may prevent alterations of the peritoneal membrane caused by acidity and high glucose concentrations. Bicarbonate/lactate–buffered solution contains a physiologic concentration of bicarbonate and a reduced concentration of lactate; it also has a physiologic pH and markedly reduced levels of glucose degradation products (GDPs). Icodextrin-based solution contains icodextrin as the osmotic agent; it is indicated for long dwells, delivering sustained ultrafiltration for more than 16 hours. This iso-osmolar glucose-free solution may reduce peritoneal membrane alterations caused by glucose or the hyperosmolality (or both) of conventional solutions.

Clinical experience of the new solutions is now extensive, and their efficacy and safety are well documented. It therefore seems appropriate to state that we have entered a new era of PD therapy. Each of the new solutions may be less damaging to the peritoneal membrane than conventional solution. In addition, they permit better management of malnutrition and fluid status, and may thus help to improve PD patient survival.

Although the effects of each of these new solutions have been well described, clinical documentation of the combined use of these new biocompatible PD solutions is still insufficient. However, the results of studies are expected, during the coming years, to support the combined use of the new solutions as the preferred standard practice for PD.

Prescribing high-quality peritoneal dialysis: Moving beyond urea clearance

Urea removal in peritoneal dialysis (PD) has been a primary measure of dialysis adequacy, but its utility remains limited due to its poor correlation with the clearance of other important uraemic retention solutes and the low certainty of evidence relating peritoneal urea clearance and survival of individuals doing PD. Indeed, clearances of other uraemic solutes, electrolyte imbalances, hypoalbuminaemia and nutritional status, may provide a more holistic measure of dialysis adequacy when evaluating individuals on PD in addition to focusing on person-centred outcomes. Here, we review the history of the urea and creatinine-centric approach to dialysis adequacy and explore the potential importance of other uraemic retention solutes, electrolyte disturbances, phosphorus control, peritoneal protein losses and hypoalbuminaemia, as well as nutritional management to promote a broader multidimensional concept of clearance for PD.

Prevalence of Carnitine Deficiency and Decreased Carnitine Levels in Patients on Peritoneal Dialysis

Background: Carnitine deficiency is common in patients on dialysis. Serum free carnitine concentration is significantly lower in patients on hemodialysis (HD) than in healthy individuals. However, there are few reports on serum free carnitine concentration in patients on peritoneal dialysis (PD). Methods: We examined serum concentrations of total, free, and acylcarnitine and the acylcarnitine/free carnitine ratio in 34 PD and 34 age-, sex-, and dialysis duration-matched HD patients. We investigated the prevalence of carnitine deficiency and clinical factors associated with carnitine deficiency in the PD group. Results: Prevalence of carnitine deficiency was 8.8% in the PD group and 17.7% in the HD group (p = 0.283). High risk of carnitine deficiency was found in 73.5% of the PD group and 76.4% of the HD group (p = 0.604). Carnitine insufficiency was found in 82.3% of the PD group and 88.2% of HD group (p = 0.733). Multivariate analysis revealed that duration of dialysis and age were independent predictors of serum free carnitine level in the PD group. Conclusions: The prevalence of carnitine deficiency, high risk of carnitine deficiency, and carnitine insufficiency in PD patients was 8.8%, 73.5%, and 82.3%, respectively. These rates were comparable to those in patients on HD.

Current Opinion on Usage of L-Carnitine in End-Stage Renal Disease Patients on Peritoneal Dialysis

The advantages of peritoneal dialysis (PD) over hemodialysis (HD) are well-documented. Notwithstanding, only a small proportion of patients with end-stage renal disease (ESRD) are managed with PD. This may be related to the high glucose load that PD solutions in current use have on the patient. The effects of such excess glucose include the relatively early limitation of the ultrafiltration capacity of the peritoneal membrane, and the metabolic effects associated with hyperglycemia, e.g., decreased insulin sensitivity. This article describes the advantages that may be realized by the glucose-sparing effects of substituting part of the glucose load with other osmotically active metabolites, particularly L-carnitine. The latter is anticipated to have metabolic advantages of its own, especially as in PD patients, high plasma concentrations can be achieved in the absence of renal clearance. Besides its better biocompatibility, L-carnitine demonstrates anti-anemia action due to its effects on erythropoiesis, and positive effects on the longevity and deformability of erythrocytes. Observations from our trials on the use of carnitine-enriched PD solutions have demonstrated the effectiveness of L-carnitine as an efficient osmolyte in PD, and its favorable effect on the insulin sensitivity of the patients. The significance of these findings for future developments in the use of PD in the management of patients with ESRD is discussed.

Risk factors for peritoneal dialysis–associated peritonitis

The purpose of this study was to summarize the pathogens that cause peritoneal dialysis (PD)-associated peritonitis and to identify risk factors for PD-associated peritonitis. This retrospective study included 115 end-stage renal disease (ESRD) patients receiving PD therapy. Patients were categorized into two groups: peritonitis group (n = 41) and non-peritonitis group (n = 74). Clinical data and laboratory tests were collected from medical records. The multivariate logistic regression model was used to evaluate associations between PD-associated peritonitis and potential risk factors. PD-associated peritonitis occurred 54 times in 41 patients. The most frequently identified pathogen was Gram-positive cocci (57.78%). Multivariate logistic regression analysis showed that serum albumin (β = –0.208, P < 0.001), blood phosphorus concentration (β = –1.732, P = 0.001), gastrointestinal disorders (β = 1.624, P = 0.043), and use of calcitriol (β = –2.239, P = 0.048) were significantly correlated with PD-associated peritonitis. Receiver operating characteristic (ROC) curves showed that the areas under the curve were 0.832 for serum albumin and 0.700 for blood phosphorus concentration with optimal cut-off values of 29.1 g/L for serum albumin and 1.795 mmol/L for blood phosphorus concentration. Gram-positive coccus is the major pathogen responsible for PD-associated peritonitis. Serum albumin <29.1 g/L, blood phosphorus concentration <1.795 mmol/L, and intestinal disorders are risk factors for PD-associated peritonitis, whereas the use of calcitriol can reduce the risk of PD-associated peritonitis.

Comparison of Kinetic Characteristics of Amino Acid-Based and Dipeptide-Based Peritoneal Dialysis Solutions

A mixture of dipeptides (DP) has been proposed as alternatives (to glucose and amino acids, (AA)) osmotic agent in peritoneal dialysis (PD) solutions. DP based solutions may have metabolic and nutritional advantages compared to AA based solutions, as some sources of AA (such as tyrosine) are poorly soluble in water. In a previous study, we compared the kinetic characteristics of DP and AA based solutions; however, the amount of AA differed substantially. The aim of the present study was to compare solutions with almost equal amounts of AA.

Methods

The following solutions were used: (1) amino acid (AA) solution containing leucine, valine, lysine, isoleucine, threonine, phenylalanine and histidine (tyrosine was omitted because of its poor solubility), (2) dipeptide (DP) solution containing leucyl-valine, lysyl-isoleucine, threonyl-phenylalanine and histidyl-tyrosine. Sixteen Sprague-Dawley rats were divided in two groups and were subjected to intraperitoneal injection of either 25 mL of AA (n=8) or DP solution. Dialysate and blood samples were taken frequently postinfusion for measurement of AA and DP concentrations as well as AA from DP.

Results

Kinetic models were developed for estimation of diffusive mass transport coefficient between peritoneal cavity and blood (KBD), DP hydrolysis rate coefficient (KH) and AA clearance in the body (KC). Calculations showed that KH is about ten times lower than KBD. Thus, hydrolysis rate in peritoneal cavity is much lower than the diffusive transport rate of DP. KBD for AA appeared to be similar to KBD for dipeptides. KC was much higher than KBD for AA. This finding explains the rapid clearance of amino acids from blood. Nevertheless, the AA-based solution resulted in much higher peak concentrations of AA in blood after 120 min of the dwell than AA concentrations achieved following the use of the DP-based solution.

Conclusions

Peritoneal transport characteristics of AA and DP were similar; however their kinetics in blood differs substantially. The DP solution resulted in a less pronounced increase in AA concentrations in blood, suggesting that DP solution could provide AA in a more physiological way.

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.

Renal Association Clinical Practice Guideline on peritoneal dialysis in adults and children

These guidelines cover all aspects of the care of patients who are treated with peritoneal dialysis. This includes equipment and resources, preparation for peritoneal dialysis, and adequacy of dialysis (both in terms of removing waste products and fluid), preventing and treating infections. There is also a section on diagnosis and treatment of encapsulating peritoneal sclerosis, a rare but serious complication of peritoneal dialysis where fibrotic (scar) tissue forms around the intestine. The guidelines include recommendations for infants and children, for whom peritoneal dialysis is recommended over haemodialysis.Immediately after the introduction there is a statement of all the recommendations. These recommendations are written in a language that we think should be understandable by many patients, relatives, carers and other interested people. Consequently we have not reworded or restated them in this lay summary. They are graded 1 or 2 depending on the strength of the recommendation by the authors, and A-D depending on the quality of the evidence that the recommendation is based on.

Dialysis Procedures Alter Metabolic Conditions

A progressive chronic kidney disease results in retention of various substances that more or less contribute to dysfunction of various metabolic systems. The accumulated substances are denominated uremic toxins. Although many toxins remain undetected, numerous newly defined toxins participate in the disturbance of food breakdown. In addition, toxic effects may downregulate other pathways, resulting in a reduced ability of free fatty acid breakdown by lipoprotein lipase (LPL) and hepatic lipase (HL). Dialysis may even worsen metabolic functions. For LPL and HL, the use of heparin and low molecular weight heparin as anticoagulation during hemodialysis (HD) initiate a loss of these enzymes from their binding sites and degradation, causing a temporary dysregulation in triglyceride breakdown. This lack of function will cause retention of the triglyceride containing lipids for at least 8 h. In parallel, the breakdown into free fatty acids is limited, as is the energy supply by them. This is repeated thrice a week for a normal HD patient. In addition, dialysis will cause a loss of amino acids and disturb glucose metabolism depending on the dialysates used. The addition of glucose in the dialysate may support oxidation of carbohydrate and the retention of Amadori products and subsequent tissue alterations. To avoid these effects, it seems necessary to further study the effects of anticoagulation in HD, the extent of use of glucose in the dialysate, and the supplementation of amino acids.

Innovations in Treatment Delivery, Risk of Peritonitis, and Patient Retention on Peritoneal Dialysis

Early innovations in the delivery of peritoneal dialysis (PD) markedly improved its acceptability and lowered peritonitis rates. The standard osmotic agent was, and continues to be dextrose, an agent that is not ideal as it is readily absorbed. The development of icodextrin-containing dialysis fluid has allowed a long dwell time to provide more effective ultrafiltration. The development of a smaller, more easily used automated cycler, led to an increase in the proportion of patients on the cycler as opposed to CAPD. Recently, new cyclers with better teaching tools and ease of use and communication with the training team have come on the market; data on outcomes using these cyclers are not yet available. Peritonitis continues to be a serious complication of PD although improvements in connectology and research on Staphylococcus aureus carriage have decreased peritonitis risk. Peritonitis rates continue to vary tremendously from one program to another, which may be in part due to failure to follow best demonstrated practices in training, care of the l catheter exit site, and prevention of peritonitis. Peritonitis rates should be expressed as episodes per year at risk and as organism-specific rates to allow comparisons from one program to another, from one period to another and from a program to the published literature. The term technique failure is misused in PD. Patients leave PD for a host of reasons including transplantation. Transfer from PD to hemodialysis can be planned and have an excellent outcome or can be delayed or done emergently and have a less optimal outcome. The life plan of the patient with ESRD needs to be not only considered but also periodically revised as circumstances and patient wishes change.

Effect of peritoneal dialysis fluid containing osmo-metabolic agents on human endothelial cells

Background

The use of glucose as the only osmotic agent in peritoneal dialysis (PD) solutions (PDSs) is believed to exert local (peritoneal) and systemic detrimental actions, particularly in diabetic PD patients. To improve peritoneal biocompatibility, we have developed more biocompatible PDSs containing xylitol and carnitine along with significantly less amounts of glucose and have tested them in cultured Human Vein Endothelial Cells (HUVECs) obtained from the umbilical cords of healthy (C) and gestational diabetic (GD) mothers.

Methods

Primary C- and GD-HUVECs were treated for 72 hours with our PDSs (xylitol 0.7% and 1.5%, whereas carnitine and glucose were fixed at 0.02% and 0.5%, respectively) and two glucose-based PDSs (glucose 1.36% or 2.27%). We examined their effects on endothelial cell proliferation (cell count), viability (3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay), intracellular nitro-oxidative stress (peroxynitrite levels), Vascular Cell Adhesion Molecule-1 and Intercellular Adhesion Molecule-1 membrane exposure (flow cytometry), and HUVEC-monocyte interactions (U937 adhesion assay).

Results

Compared to glucose-based PDSs, our in vitro studies demonstrated that the tested PDSs did not change the proliferative potential both in C- and GD-HUVECs. Moreover, our PDSs significantly improved endothelial cell viability, compared to glucose-based PDSs and basal condition. Notably, glucose-based PDSs significantly increased the intracellular peroxynitrite levels, Vascular Cell Adhesion Molecule-1 and Intercellular Adhesion Molecule-1 membrane exposure, and endothelial cell–monocyte interactions in both C- and GD-HUVECs, as compared with our experimental PDSs.

Conclusion

Present results show that in control and diabetic human endothelial cell models, xylitol–carnitine-based PDSs do not cause cytotoxicity, nitro-oxidative stress, and inflammation as caused by hypertonic glucose-based PDSs. Since xylitol and carnitine are also known to favorably affect glucose homeostasis, these findings suggest that our PDSs may represent a desirable hypertonic solution even for diabetic patients in PD.

Peritoneal Dialysis in Western Countries

BACKGROUND

Peritoneal dialysis (PD) for the treatment of end-stage renal failure was introduced in the 1960s. Nowadays it has evolved to an established therapy that is complementary to hemodialysis (HD), representing 11% of all patients treated worldwide with dialysis. Despite good clinical outcomes and similar results in patient survival between PD and HD, the penetration of PD is decreasing in the Western world.

SUMMARY

First the major events in the history of the development of PD are described. Then important insights into the physiology of peritoneal transport are discussed and linked to the changes in time observed in biopsies of the peritoneal membrane. Furthermore, the developments in peritoneal access, more biocompatible dialysate solutions, automated PD at home, the establishment of parameters for dialysis adequacy and strategies to prevent infectious complications are mentioned. Finally non-medical issues responsible for the declining penetration in the Western world are analyzed.

KEY MESSAGES

Only after introduction of the concept of continuous ambulatory PD by Moncrief and Popovich has this treatment evolved in time to a renal replacement therapy. Of all structures present in the peritoneal membrane, the capillary endothelium offers the rate-limiting hindrance for solute and water transport for the diffusive and convective transport of solutes and osmosis. The functional and anatomical changes in the peritoneal membrane in time can be monitored by the peritoneal equilibrium test. Peritonitis incidence decreased by introduction of the Y-set and prophylaxis using mupirocin on the exit site. The decrease in the proportion of patients treated with PD in the Western world can be explained by non-medical issues such as inadequate predialysis patient education, physician experience and training, ease of HD initiation, overcapacity of in-center HD, lack of adequate infrastructure for PD treatment, costs and reimbursement issues of the treatment.

FACTS FROM EAST AND WEST

(1) PD is cheaper than HD and provides a better quality of life worldwide, but its prevalence is significantly lower than that of HD in all countries, with the exception of Hong Kong. Allowing reimbursement of PD but not HD has permitted to increase the use of PD over HD in many Asian countries like Hong Kong, Vietnam, Taiwan, Thailand, as well as in New Zealand and Australia over the last years. In the Western world, however, HD is still promoted, and the proportion of patients treated with PD decreases. Japan remains an exception in Asia where PD penetration is very low. Lack of adequate education of practitioners and information of patients might as well be reasons for the low penetration of PD in both the East and West. (2) Patient survival of PD varies between and within countries but is globally similar to HD. (3) Peritonitis remains the main cause of morbidity in PD patients. South Asian countries face specific issues such as high tuberculosis and mycobacterial infections, which are rare in developed Asian and Western countries. The infection rate is affected by climatic and socio-economic factors and is higher in hot, humid and rural areas. (4) Nevertheless, the promotion of a PD-first policy might be beneficial particularly for remote populations in emerging countries where the end-stage renal disease rate is increasing dramatically.

Pharmacologic targets and peritoneal membrane remodeling

Peritoneal dialysis (PD) is associated with functional and structural changes of the peritoneal membrane, also known as peritoneal remodeling. The peritoneal membrane is affected by many endogenous and exogenous factors such as cytokines, PD fluids, and therapeutic interventions. Here, we present an overview of various studies that have investigated pharmacologic interventions aimed at regression of peritoneal damage and prolongation of PD treatment.

Nutritional issues in peritoneal dialysis patients: how do they differ from that of patients undergoing hemodialysis?

It is important to understand the unique aspects vis-à-vis protein-energy wasting for patients undergoing PD. As a result of obligatory protein losses with the therapy, the serum albumin levels of patients undergoing PD are lower, as is the threshold serum albumin at which the risk for death is increased. Consequently, it is prudent to consider a lower threshold for serum albumin for the diagnosis of protein-energy wasting for patients undergoing PD. Likewise, it is important to consider the energy intake from obligatory nutrient absorption in the form of carbohydrates when estimating total energy intake (diet and dialysate) when evaluating patients for protein-energy wasting. The continuous nature of PD also has important therapeutic implications for protein-energy wasting. Such patients are more likely to have a complete correction of metabolic acidosis, and glucose absorption from the peritoneal dialysate has a protein-sparing effect, allowing some patients to maintain neutral nitrogen balances in the face of suboptimal protein intake. In contrast, clinical trials of amino-acid-based PD solutions have not met expectations and cannot be recommended for routine use for treatment of protein-energy wasting. In conclusion, it is important to consider these unique nutritional considerations when providing care to patients undergoing PD.

Effects of peritoneal dialysis on protein metabolism

Protein-energy wasting is relatively common in renal patients treated with haemodialysis or peritoneal dialysis (PD) and is associated with worse outcome. In this article, we review the current state of our knowledge regarding the effects of PD on protein metabolism and the possible interactions between PD-induced changes in protein turnover and the uraemia-induced alterations in protein metabolism. Available evidence shows that PD induces a new state in muscle protein dynamics, which is characterized by decreased turnover rates and a reduced efficiency of protein turnover, a condition which may be harmful in stress conditions, when nutrient intake is diminished or during superimposed catabolic illnesses. There is a need to develop more effective treatments to enhance the nutritional status of PD patients. New approaches include the use of amino acid/keto acids-containing supplements combined with physical exercise, incremental doses of intraperitoneal amino acids, vitamin D and myostatin antagonism for malnourished patients refractory to standard nutritional therapy.

Current techniques in peritoneal dialysis

OBJECTIVE

To provide a current overview of the technique of peritoneal dialysis in dogs and cats.

CLINICAL IMPLICATION

Peritoneal dialysis is the process by which water and solutes move between blood in the peritoneal capillaries and fluid (dialysate) instilled into the peritoneal cavity, across the semipermeable membrane of the peritoneum. The primary indication for peritoneal dialysis (PD) in animals is for treatment of renal failure to correct water, solute, and acid-base abnormalities and to remove uremic toxins.

SUMMARY

Peritoneal dialysis is a modality of renal replacement therapy commonly used in human medicine for the treatment of chronic kidney disease and end-stage kidney failure. Peritoneal dialysis utilizes the peritoneum as a membrane across which fluids and uremic solutes are exchanged. Dialysate is instilled into the peritoneal cavity and, through the process of diffusion and osmosis, water, toxins, electrolytes, and other small molecules are allowed to equilibrate.

A patient with CKD and poor nutritional status

Protein energy wasting is common in patients with CKD and ESRD and is associated with adverse clinical outcomes, such as increased rates of hospitalization and death, in these patients. A multitude of factors can affect the nutritional and metabolic status of patients with CKD, including decreased dietary nutrient intake, catabolic effects of renal replacement therapy, systemic inflammation, metabolic and hormonal derangements, and comorbid conditions (such as diabetes and depression). Unique aspects of CKD also confound reliable assessment of nutritional status, further complicating management of this comorbid condition. In patients in whom preventive measures and oral dietary intake from regular meals cannot help them maintain adequate nutritional status, nutritional supplementation, administered orally, enterally, or parenterally, is effective in replenishing protein and energy stores. The advantages of oral nutritional supplements include proven efficacy, safety, and compliance. Anabolic steroids and exercise, with nutritional supplementation or alone, improve protein stores and represent potential additional approaches for the treatment of PEW. There are several emerging novel therapies, such as appetite stimulants, anti-inflammatory interventions, and anabolic agents.

Prevention and treatment of protein energy wasting in chronic kidney disease patients: a consensus statement by the International Society of Renal Nutrition and Metabolism

Protein energy wasting (PEW) is common in patients with chronic kidney disease (CKD) and is associated with adverse clinical outcomes, especially in individuals receiving maintenance dialysis therapy. A multitude of factors can affect the nutritional and metabolic status of CKD patients requiring a combination of therapeutic maneuvers to prevent or reverse protein and energy depletion. These include optimizing dietary nutrient intake, appropriate treatment of metabolic disturbances such as metabolic acidosis, systemic inflammation, and hormonal deficiencies, and prescribing optimized dialytic regimens. In patients where oral dietary intake from regular meals cannot maintain adequate nutritional status, nutritional supplementation, administered orally, enterally, or parenterally, is shown to be effective in replenishing protein and energy stores. In clinical practice, the advantages of oral nutritional supplements include proven efficacy, safety, and compliance. Anabolic strategies such as anabolic steroids, growth hormone, and exercise, in combination with nutritional supplementation or alone, have been shown to improve protein stores and represent potential additional approaches for the treatment of PEW. Appetite stimulants, anti-inflammatory interventions, and newer anabolic agents are emerging as novel therapies. While numerous epidemiological data suggest that an improvement in biomarkers of nutritional status is associated with improved survival, there are no large randomized clinical trials that have tested the effectiveness of nutritional interventions on mortality and morbidity.

Nutrition and the kidney: recommendations for peritoneal dialysis

Protein energy wasting (PEW) is highly prevalent in peritoneal dialysis (PD) and is associated with poor outcomes, including hospitalization and mortality. Recognizing and diagnosing PEW in PD is important; although studies are limited, there are interventions that may be associated with improved outcomes. In this review of nutritional aspects of PD, we highlight some of the important causes of PEW and explore the current diagnostic tools that are used to assess PEW. Finally, we discuss the established and experimental therapies for PEW in PD.

Nutrition in patients on peritoneal dialysis

Protein-energy wasting (PEW) is prevalent among patients on dialysis and has emerged as an important risk factor for morbidity and mortality in these patients. Numerous factors, including inflammation, inadequate dialysis, insufficient nutrient intake, loss of protein during dialysis, chronic acidosis, hypercatabolic illness and comorbid conditions, are involved in the development of PEW. The causes and clinical features of PEW in patients on peritoneal dialysis and hemodialysis are comparable; assessment of the factors that lead to PEW in patients receiving peritoneal dialysis is important to ensure that PEW is managed correctly in these patients. For the past 20 years, much progress has been made in the prevention and treatment of PEW. However, the results of most nutritional intervention studies are inconclusive. In addition, the multifactorial and complicated pathogenesis of PEW makes it difficult to assess and treat. This Review summarizes the nutritional issues regarding the causes, assessment and treatment of PEW, with a focus on patients receiving peritoneal dialysis. In addition, an in-depth overview of the results of nutritional intervention studies is provided.

A clinical review of peritoneal dialysis

OBJECTIVE

To review the principles and practice of peritoneal dialysis in veterinary medicine.

DATA SOURCES

Clinical and experimental studies and current guideline recommendations from the human literature; and original case studies, case reports, and previous reviews in the veterinary literature.

SUMMARY

Peritoneal dialysis involves the exchange of solutes and fluid between the peritoneal capillary blood and the dialysis solution across the peritoneal membrane. It requires placement of a peritoneal dialysis catheter for repeated dialysate exchange. The ideal catheter provides reliable, rapid dialysate flow rates without leaks or infections. Catheter selection and placement are reviewed along with dialysate selection, exchange prescriptions, and overall patient management. PD does not require specific or complex equipment, and it can achieve effective control of uremia and electrolyte imbalances.

CONCLUSIONS

Peritoneal dialysis is a potential life-saving measure for patients with acute renal failure. Peritoneal dialysis results in gradual decline in uremic toxins. Previously low success rates have been reported. Improved success rates have been noted in dogs with acute kidney injury (AKI) secondary to leptospirosis. Cats also have a good success rate when PD is elected in patients with a potentially reversible underlying disease. Overall, PD remains a viable intervention for patients with AKI unresponsive to medical management. In select patients a favorable outcome is attained whereby PD provides temporary support until return of effective renal function is attained.

L-carnitine is an osmotic agent suitable for peritoneal dialysis

Excessive intraperitoneal absorption of glucose during peritoneal dialysis has both local cytotoxic and systemic metabolic effects. Here we evaluate peritoneal dialysis solutions containing L-carnitine, an osmotically active compound that induces fluid flow across the peritoneum. In rats, L-carnitine in the peritoneal cavity had a dose-dependent osmotic effect similar to glucose. Analogous ultrafiltration and small solute transport characteristics were found for dialysates containing 3.86% glucose, equimolar L-carnitine, or combinations of both osmotic agents in mice. About half of the ultrafiltration generated by L-carnitine reflected facilitated water transport by aquaporin-1 (AQP1) water channels of endothelial cells. Nocturnal exchanges with 1.5% glucose and 0.25% L-carnitine in four patients receiving continuous ambulatory peritoneal dialysis were well tolerated and associated with higher net ultrafiltration than that achieved with 2.5% glucose solutions, despite the lower osmolarity of the carnitine-containing solution. Addition of L-carnitine to endothelial cells in culture increased the expression of AQP1, significantly improved viability, and prevented glucose-induced apoptosis. In a standard toxicity test, the addition of L-carnitine to peritoneal dialysis solution improved the viability of L929 fibroblasts. Thus, our studies support the use of L-carnitine as an alternative osmotic agent in peritoneal dialysis.