Peritoneal dialysis fluids

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

Assessment of the size selectivity of peritoneal permeability by the restriction coefficient to protein transport

Transport of serum proteins from the circulation to peritoneal dialysate in peritoneal dialysis patients mainly focused on total protein. Individual proteins have hardly been studied. We determined serum and effluent concentrations of four individual proteins with a wide molecular weight range routinely in the standardised peritoneal permeability analysis performed yearly in all participating patients. These include β2-microglobulin, albumin, immunoglobulin G and α2-macroglobulin. The dependency of transport of these proteins on their molecular weight and diffusion coefficient led to the development of the peritoneal protein restriction coefficient (PPRC), which is the slope of the relation between the peritoneal clearances of these proteins and their free diffusion coefficients in water, when plotted on a double logarithmic scale. The higher the PPRC, the more size restriction to transport. In this review, we discuss the results obtained on the PPRC under various conditions, such as effects of various osmotic agents, vasoactive drugs, peritonitis and the hydrostatic pressure gradient. Long-term follow-up of patients shows an increase of the PPRC, the possible causes of which are discussed. Venous vasculopathy of the peritoneal microcirculation is the most likely explanation.

A Comparison between 1.36% and 3.86% Glucose Dialysis Solution for the Assessment of Peritoneal Membrane Function

Objective

To assess peritoneal membrane function with respect to fluid transport, parameters of low molecular weight solute transport, and estimations of the function of peritoneal water channels, comparing the results from a 1.36%/1.5% glucose solution with those from a 3.86%/4.25% solution in standardized peritoneal function tests.

Design

The study was performed in 40 stable continuous ambulatory peritoneal dialysis (CAPD) patients [median age 50 years (range: 22 – 74 years); duration of CAPD 9 months (range: 2 – 45 months)] who underwent two standard peritoneal permeability analyses (SPAs) within 1 month. One SPA used 1.36% glucose; the other, 3.86% glucose. Mass transfer area coefficients (MTACs) and dialysate-to-plasma (D/P) ratios were compared for the two solutions. Also, two different methods of estimating aquaporin-mediated water transport were compared: the sieving of sodium (3.86% glucose) and the difference in net ultrafiltration (ΔNUF), calculated as NUF 3.86% SPA – NUF 1.36% SPA.

Results

Median NUF in the 1.36% glucose SPA was –46 mL (range: –582 mL to 238 mL); in the 3.86% SPA, it was 554 mL (range: –274 mL to 1126 mL). The median difference in NUF for the two SPAs was 597 mL (range: 90 – 1320 mL). No difference between the two solutions was seen for the MTAC of creatinine (11.4 mL/min for 1.36% vs 12.0 mL/min for 3.86%) and absorption of glucose (64% vs 65%, respectively). Also, D/P creatinine was not different: 0.77 (1.36%) and 0.78 (3.86%). However, the ratio of dialysate glucose at 240 minutes and at 0 minutes (Dt/D0) was 0.34 (1.36%) and 0.24 (3.86%), p < 0.01. Values of D/P creatinine from the two glucose solutions were strongly correlated. The intra-individual differences were small and showed a random distribution. Patient transport category was minimally influenced by the tonicity of the dialysate. The minimum D/P Na+(3.86%) was 0.884, and it was reached after 60 minutes. After correction for Na+diffusion, D/P Na+decreased to 0.849 after 120 minutes. The correlation coefficient between the diffusion-corrected D/P Na+and the ΔNUF was 0.49, p < 0.01. An inverse relationship was present between MTAC creatinine and D/P Na+( p < 0.01) This correlation can be explained by the rapid disappearance of the osmotic gradient owing to a large vascular surface area. Such a correlation was not present between MTAC creatinine and ΔNUF.

Conclusions

We conclude that a standardized 4-hour peritoneal permeability test using 3.86%/4.25% glucose is the preferred method to assess peritoneal membrane function, including aquaporin-mediated water transport. The D/P Na+after correction for Na+diffusion is probably more useful for the assessment of aquaporin-mediated water transport than is ΔNUF obtained with 3.86%/ 4.25% and 1.36%/1.5% glucose-based dialysis solutions.

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).

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.

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.

Analysis of the Prevalence and Causes of Ultrafiltration Failure during Long-Term Peritoneal Dialysis: A Cross-Sectional Study

Background

Ultrafiltration failure (UFF) is a major complication of peritoneal dialysis (PD). It can occur at any stage of PD, but develops in time and is, therefore, especially important in long-term treatment. To investigate its prevalence and to identify possible causes, we performed a multicenter study in The Netherlands, where patients treated with PD for more than 4 years were studied using a peritoneal function test (standard peritoneal permeability analysis) with 3.86% glucose. UFF was defined as net UF < 400 mL after a 4-hour dwell.

Results

55 patients unselected for the presence or absence of UFF were analyzed. Mean age was 48 years (range 18 – 74 years); duration of PD ranged from 48 to 144 months (median 61 months); UFF was present in 20 patients (36%). Patients with and without UFF did not differ in age or duration of PD. Median values for patients with normal UF compared to patients with UFF were, for net UF 659 mL versus 120 mL ( p < 0.01), transcapillary UF rate 3.8 versus 2.1 mL/minute ( p < 0.01), effective lymphatic absorption 1.0 versus 1.6 mL/min ( p < 0.05), mass transfer area coefficient (MTAC) for creatinine 9.0 versus 12.9 mL/min ( p < 0.01), dialysate-to-plasma ratio (D/P) for creatinine 0.71 versus 0.86 ( p < 0.01), glucose absorption 60% versus 73% ( p < 0.01), maximum dip in D/P sodium (as a measure of free water transport) 0.109 versus 0.032 ( p < 0.01), and osmotic conductance to glucose 3.0 versus 2.1 μL/min/mmHg ( p < 0.05). As causes for UFF, high MTAC creatinine, defined as > 12.5 mL/min, or a glucose absorption > 72%, both reflecting a large vascular surface, a lymphatic absorption rate (LAR) of > 2.14 mL/min, and a decreased dip in D/P sodium of < 0.046 were identified. Most patients had a combination of causes (12 patients), whereas there was only a decreased dip in D/P sodium in 3 patients, only high MTAC creatinine in 1 patient, and only high LAR in 2 patients. We could not identify a cause in 2 patients. Both groups had similar clearances of serum proteins and peritoneal restriction coefficients. However, dialysate cancer antigen 125 concentrations, reflecting mesothelial cell mass, were lower in the UFF patients (2.79 vs 5.38 U/L).

Conclusion

The prevalence of UFF is high in long-term PD. It is caused mainly by a large vascular surface area and by impaired channel-mediated water transport. In addition, these patients also had signs of a reduced mesothelial cell mass, indicating damage of the peritoneum on both vascular and mesothelial sites.

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.

Treatment of severe ultrafiltration failure with nonglucose dialysis solutions in patients with and without peritoneal sclerosis

Introduction. Ultrafiltration failure (UFF) in peritoneal dialysis (PD) patients is a reflection of changes in the peritoneal membrane, which can include mesothelial damage, neoangiogenesis, and occasionally, peritoneal fibrosis. These structural changes are probably induced by the use of bioincompatible dialysis solutions. Therefore, we investigated the effects of the treatment with a combination of nonglucose dialysis solutions in patients with severe UFF. Methods. Ten patients with UFF (net ultrafiltration <400 mL/4 h on 3.86% glucose) were treated with a combination of glycerol and icodextrin with or without amino acid-based dialysis solutions for 3 months. Four of them were diagnosed with encapsulating peritoneal sclerosis (PS), proven by peritoneal biopsies. Standard peritoneal permeability analyses (SPA), using 3.86% glucose, were performed, and dialysate CA125 appearance rate (AR-CA125) was analysed at the start, after 6 weeks and after 12 weeks. PS and non-PS patients were compared. Results. One patient underwent transplant after 6 weeks, one was withdrawn from PD because of clinical signs of encapsulating PS before the 3-month period ended. PS patients had been treated with PD for a longer duration than the non-PS patients (102 versus 52 months, P = 0.05), but no differences in baseline transport parameters or AR-CA125 were present. During the study, no differences were observed for transport characteristics when the results of the whole group at 6 and 12 weeks were compared to baseline. For the non-PS patients, however, a significant increase in the transcapillary ultrafiltration rate (from 2.2 mL/min to 2.6 mL/min, P < 0.05) and a decrease in the MTAC creatinine (from 14.3 mL/min to 12.6 mL/min, P < 0.05) were found after 6 weeks of glucose-free treatment. Free-water transport, measured as the maximum dip in the dialysate-to-plasma ratio of sodium and as the transport through the ultrasmall pores in the first minute, tended to improve, but this difference did not reach significance. In addition, the AR-CA125 increased significantly (from 2.8 U/min to 16.1 U/min, P < 0.05). Continued treatment did not reach statistical difference even after 3 months. No changes were observed in the PS patients. Conclusions. In the present study, an improvement of UFF in the non-PS patients was obtained by withdrawal of glucose-based dialysis solutions. The abnormalities in PS patients are probably irreversible. Early withdrawal of glucose-based dialysis solutions or at least a marked reduction in glucose exposure should be considered in UFF patients, but the identification of the patients who would benefit most needs further studies.

Safety aspects and side-effects of ExEm-gel and foam for uterine cavity distension and tubal patency testing

A state-of-the-art overview of the safety and side-effects of ExEm-gel for uterine cavity distension and ExEm-foam for tubal patency testing is presented. A literature search was carried out using PubMed, textbooks, pharmaceutical databases and reports of toxicity tests. Information on clinical use in humans and experiments in animal models was collected and grouped according to the following components: glycerol, hydroxyethyl cellulose and purified water; subjects included toxicity test, influence on sperm cells, oocytes, blastocyst development, uterine cavity distension, tubal patency testing, pain and obstetric applications. No unknown side-effects of gel or foam, or unexpected concerns about safety, were reported. More information than expected was available on the absence of effects of the components on various human tissues. Although it is difficult to prove that the search is complete, and it is possible that side-effects remain unreported, the combination of glycerol, hydroxyethyl cellulose and purified water is considered to be safe for intrauterine application and tubal patency testing, indicating an optimal risk-benefit ratio in clinical use. The safest strategy, however, is to restrict clinical examinations with gel and foam to the pre-ovulatory phase of the menstrual cycle.

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.

Peritoneal dialysis: from bench to bedside

Peritoneal dialysis was first employed in patients with acute renal failure in the 1940s and since the 1960s for those with end-stage renal disease. Its popularity increased enormously after the introduction of continuous ambulatory peritoneal dialysis in the end of 1970s. This stimulated both clinical and basic research. In an ideal situation, this should lead to cross-fertilization between the two. The present review describes two examples of interactions: one where it worked out very well and another where basic science missed the link with clinical findings. Those on fluid transport are examples of how old physiological findings on absorption of saline and glucose solutions were adopted in peritoneal dialysis by the use of glucose as an osmotic agent. The mechanism behind this in patients was first solved mathematically by the assumption of ultrasmall intracellular pores allowing water transport only. At the same time, basic science discovered the water channel aquaporin-1 (AQP-1), and a few years later, studies in transgenic mice confirmed that AQP-1 was the ultrasmall pore. In clinical medicine, this led to its assessment in patients and the notion of its impairment. Drugs for treatment have been developed. Research on biocompatibility is not a success story. Basic science has focussed on dialysis solutions with a low pH and lactate, and effects of glucose degradation products, although the first is irrelevant in patients and effects of continuous exposure to high glucose concentrations were largely neglected. Industry believed the bench more than the bedside, resulting in 'biocompatible' dialysis solutions. These solutions have some beneficial effects, but are evidently not the final answer.

Aquaporin-1 in the peritoneal membrane: implications for peritoneal dialysis and endothelial cell function

PD (peritoneal dialysis) is an established mode of renal replacement therapy, based on the exchange of fluid and solutes between blood in peritoneal capillaries and a dialysate that has been introduced into the peritoneal cavity. The dialysis process involves diffusive and convective transports and osmosis through the PM (peritoneal membrane). Computer simulations predicted that the PM contains ultrasmall pores (radius <3 A, 1 A=10(-10) m), responsible for up to 50% of UF (ultrafiltration), i.e. the osmotically driven water movement during PD. Several lines of evidence suggest that AQP1 (aquaporin-1) is the ultrasmall pore responsible for transcellular water permeability during PD. Treatment with corticosteroids induces the expression of AQP1 in the PM and improves water permeability and UF in rats without affecting the osmotic gradient and permeability for small solutes. Studies in knockout mice provided further evidence that osmotically driven water transport across the PM is mediated by AQP1. AQP1 and eNOS (endothelial nitric oxide synthase) show a distinct regulation within the endothelium lining the peritoneal capillaries. In acute peritonitis, the up-regulation of eNOS and increased release of nitric oxide dissipate the osmotic gradient and prevent UF, whereas AQP1 expression is unchanged. These results illustrate the usefulness of the PM to investigate the role and regulation of AQP1 in the endothelium. The results also emphasize the critical role of AQP1 during PD and suggest that manipulation of AQP1 expression may be used to increase water permeability across the PM.

The effects of a dialysis solution with a combination of glycerol/amino acids/dextrose on the peritoneal membrane in chronic renal failure

BACKGROUND

Long-term peritoneal dialysis (PD) with conventional glucose based, lactate-buffered PD fluids may lead to morphological and functional alterations of the peritoneal membrane. It was hypothesized that long-term exposure to a different buffer and a mixture of osmotic agents would cause less peritoneal abnormality.

OBJECTIVES

To investigate the effects of long-term exposure to a bicarbonate/lactate-buffered dialysis solution with a mixture of osmotic agents: glycerol 1.4%, amino acids 0.5%, and dextrose 1.1% (= 1% glucose) (GLAD) in a rat model with chronic kidney failure.

METHODS

All rats underwent a peritoneal catheter implantation and a 70% nephrectomy. Thereafter, the rats were randomly divided into 3 groups: GLAD, 3.86% Dianeal (Baxter, Nivelles, Belgium), and buffer (Physioneal without glucose, Baxter). All rats were infused daily for 16 weeks with the appropriate PD fluid. Afterwards, a peritoneal permeability analysis (SPARa) was performed using 3.86% Physioneal in all groups. After the SPARa, the rats were sacrificed to obtain tissue samples for morphometric determinations. Omental tissue was stained with picro Sirius red for assessment of fibrosis and with CD31 for vessel density.

RESULTS

GLAD and Dianeal showed faster small solute transport compared to the hypotonic buffer. No differences between the groups were present in ultrafiltration. Dianeal had the lowest value for free water transport and the highest protein clearances. Total triglyceride in plasma was not different between GLAD and the buffer. Vessel density after GLAD exposure (20 V/F) was very similar to the value found for the buffer solution (17 V/F); Dianeal caused a significantly higher value (35 V/F, p < 0.01). Also, the amount of fibrosis was higher in the Dianeal-exposed rats (p < 0.01).

CONCLUSION

Both hypertonic dialysis solutions increased peritoneal solute transport. GLAD exposure was associated with the best preservation of peritoneal morphology. The results of GLAD were very similar to those of the bicarbonate/lactate-buffered solution without osmotic agents. Studies in humans are needed for further assessment of GLAD.

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.

Clinical application of aquaporin research: aquaporin-1 in the peritoneal membrane

Peritoneal dialysis (PD) is an established mode of renal replacement therapy based on the exchange of fluid and solutes between blood and a dialysate that has been instilled in the peritoneal cavity. The dialysis process involves osmosis, as well as diffusive and convective transports through the highly vascularized peritoneal membrane. Computer simulations predicted that the membrane contains ultrasmall pores responsible for the selective transport of water across the capillary endothelium during crystalloid osmosis. The distribution of the water channel aquaporin-1 (AQP1), as well as its molecular structure ensuring an exquisite selectivity for water, fit with the characteristics of the ultrasmall pore. Peritoneal transport studies using AQP1 knockout mice demonstrated that the osmotic water flux across the peritoneal membrane is mediated by AQP1. This water transport accounts for 50% of the ultrafiltration during PD. Treatment with high-dose corticosteroids upregulates the expression of AQP1 in peritoneal capillaries, resulting in increased water transport and ultrafiltration in rats. AQP1 may also play a role during inflammation, as vascular proliferation and leukocyte recruitment are both decreased in mice lacking AQP1. These data illustrate the potential of the peritoneal membrane as an experimental model in the investigation of the role of AQP1 in the endothelium at baseline and during inflammation. They emphasize the critical role of AQP1 during PD and suggest that manipulating AQP1 expression could be clinically useful in PD patients.

Impact of glucose levels on advanced glycation end products in hemodialysis

The current obesity epidemic throughout the western world has resulted in a considerable increase in the condition Type II diabetes mellitus. Recently, the World Health Organization has predicted that the global prevalence of Type II will increase from 175 million patients in 2003 to over 350 million by 2030. One of the major consequences of this disorder is renal failure, which presents itself as chronic kidney disease, and can progress to end-stage renal disease. Once diagnosed, patients are generally treated using dialysis due to a shortage of kidney donors. The fundamental process of dialysis still requires improvement because the survival rate of these patients is relatively poor. This has resulted in considerable research into improvements in hemodialysis membranes, and the challenge to find more suitable marker(s) in assessing the efficacy of the dialysis process. A class of compounds highlighted as a possible accumulative toxin is advanced glycation end products or AGEs. This is an article regarding the impact of hemodialysis and hemodiafiltration on glucose and AGE levels within the body and the consequences of a chronic hyperglycemic condition. It also highlights the negative aspects of using dextrose in conventional dialysis solutions (an area that has already been identified by peritoneal dialysis clinicians as problematic). The review concludes by suggesting several possible topics of future research.

Analysis of fluid transport pathways and their determinants in peritoneal dialysis patients with ultrafiltration failure

Ultrafiltration failure (UFF) is a serious complication of peritoneal dialysis (PD). The aim of the study was to analyze changes in water transport and their determinants in UFF patients over the time on PD. Standard peritoneal permeability analyses of 50 stable PD patients with UFF were analyzed. Fluid transport through small pores (SPT), free water transport (FWT) at 60 min, their contributions on total ultrafiltration (SPTC and FWTC), and their determinants were assessed. Patients were divided in Group I (UFF) treated for less than 24 months, Group II treated 24-60 months, and Group III treated for more than 60 months. Group I (UFF) was compared with Group I (non-UFF) matched for the duration of PD treatment and age. Transcapillary ultrafiltration (TCUF), SPT, FWT, and FWTC were significantly lower in Group III when compared to the other UFF groups. In this group also, negative relationship was present between FWT, the ultrafiltration coefficient LpA, and osmotic conductance to glucose on one hand and PD duration on the other. FWT was positively related to osmotic conductance to glucose in all groups. Group I (UFF) showed significantly higher solute transport, effective lymphatic absorption rate, lower TCUF, and lower FWT than Group I (non-UFF). The patterns of UFF in PD patients are dependent on the duration of treatment.

Aquaporin-1 in the peritoneal membrane: Implications for water transport across capillaries and peritoneal dialysis

Peritoneal dialysis (PD) is an established mode of renal replacement therapy, based on the exchange of fluid and solutes between blood in peritoneal capillaries and a dialysate that has been introduced in the peritoneal cavity. The dialysis involves diffusive and convective transports and osmosis through the highly vascularized peritoneal membrane. Computer simulations predicted that the membrane contains ultrasmall pores (radius < 3 A) responsible for the transport of solute-free water across the capillary endothelium during crystalloid osmosis. The distribution of the water channel aquaporin-1 (AQP1), as well as its molecular structure ensuring an exquisite selectivity for water perfectly fit with the characteristics of the ultrasmall pore. Treatment with corticosteroids induces the expression of AQP1 in peritoneal capillaries and increases water permeability and ultrafiltration in rats, without affecting the osmotic gradient and the permeability for small solutes. Studies in knockout mice provided further evidence that osmotically-driven water transport across the peritoneal membrane is mediated by AQP1. AQP1 and endothelial NO synthase (eNOS) show a distinct regulation within the endothelium lining peritoneal capillaries. In acute peritonitis, the upregulation of eNOS and increased release of NO dissipate the osmotic gradient and result in ultrafiltration failure, despite the unchanged expression of AQP1. These data illustrate the potential of the peritoneal membrane to investigate the role and regulation of AQP1 in the endothelium. They also emphasize the critical role of AQP1 during peritoneal dialysis and suggest that manipulating AQP1 expression may be used to increase water permeability across the peritoneal membrane.

Prevention of postoperative abdominal adhesions by a novel, glycerol/sodium hyaluronate/carboxymethylcellulose-based bioresorbable membrane: a prospective, randomized, evaluator-blinded multicenter study

INTRODUCTION

Postoperative abdominal adhesions are associated with significant morbidity and mortality, placing a substantial burden on healthcare systems worldwide. Development of a bioresorbable membrane containing up to 23 percent glycerol and chemically modified sodium hyaluronate/carboxymethylcellulose offers ease of handling and has been shown to provide significant postoperative adhesion prevention in animals. This study was designed to assess the safety of glycerol hyaluronate/carboxymethylcellulose and to evaluate its efficacy in reducing the incidence, extent, and severity of postoperative adhesion development in surgical patients.

METHODS

Twelve centers enrolled 120 patients with ulcerative colitis or familial polyposis who were scheduled for a restorative proctocolectomy and ileal pouch-anal anastomosis with diverting loop ileostomy. Before surgical closure, patients were randomized to no anti-adhesion treatment (control) or treatment with glycerol hyaluronate/carboxymethylcellulose membrane under the midline incision. At ileostomy closure, laparoscopy was used to evaluate the incidence, extent, and severity of adhesion formation to the midline incision.

RESULTS

Data were analyzed using the intent-to-treat population. Treatment with glycerol hyaluronate/carboxymethylcellulose resulted in 19 of 58 patients (33 percent) with no adhesions compared with 6 of 60 adhesion-free patients (10 percent) in the no treatment control group (P = 0.002). The mean extent of postoperative adhesions to the midline incision was significantly lower among patients treated with glycerol hyaluronate/carboxymethylcellulose compared with patients in the control group (P < 0.001). The severity of postoperative adhesions to the midline incision was significantly less with glycerol hyaluronate/carboxymethylcellulose than with control (P < 0.001). Adverse events were similar between treatment and no treatment control groups with the exception of abscess and incisional wound complications were more frequently observed with glycerol hyaluronate/carboxymethylcellulose.

CONCLUSIONS

Glycerol hyaluronate/carboxymethylcellulose was shown to effectively reduce adhesions to the midline incision and adhesions between the omentum and small bowel after abdominal surgery. Safety profiles for the treatment and no treatment control groups were similar with the exception of more infection complications associated with glycerol hyaluronate/carboxymethylcellulose use. Animal models did not predict these complications.