Mitigating peritoneal membrane characteristics in modern peritoneal dialysis therapy

Peritoneal equilibration testing: Your questions answered

The peritoneal equilibration test (PET), first described in 1987, is a semiquantitative assessment of peritoneal transfer characteristics in patients undergoing peritoneal dialysis. It is typically performed as a 4-h exchange using 2.27/2.5% dextrose dialysate with serial measurements of blood and dialysate creatinine, urea, and glucose concentrations. The percentage absorption of glucose and D/P creatinine ratio are used to determine peritoneal solute transfer rates. It is used to both help guide peritoneal dialysis prescriptions and to prognosticate. There are several derivative tests which have been described in the literature. In this review, we describe the original PET, the various iterations of the PET, the information gleaned, and the use in the setting of poor solute clearance and in the diagnosis of membrane dysfunction, and limitations of the PET.

Comparison of patient survival and technique survival between continuous ambulatory peritoneal dialysis and automated peritoneal dialysis

Background:

This retrospective cohort study compared patient survival and technique survival between patients on continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD) using recent data at a single tertiary medical center in Taiwan.

Methods:

From medical records, we identified incident 459 CAPD patients and 266 APD patients on dialysis for at least 90 days and aged more than 18 years to estimate mortality and technique failure rates, and related hazard ratio (HR) and 95% confidence interval (CI) from 2007 to 2018.

Results:

There were more women (52.3%) in the CAPD group, whereas patients in the APD group were younger. Compared to CAPD patients, APD patients had a lower mortality rate (2.83 vs. 5.79 per 100 person-years) with an adjusted HR of 0.69 (95% CI = 0.47–1.02), and a lower technique failure rate (9.70 vs. 17.52 per 100 person-years) with an adjusted HR of 0.65 (95% CI = 0.51–0.83). Further subgroup analyses revealed that, compared to CAPD, APD was associated with a significant lower risk of technique failure in male patients, patients aged 50–65 years, diabetic patients, patients without cardiovascular disease (CVD), patients with higher peritoneal permeability, or patients initiating PD in an earlier era.

Conclusions:

The mortality risk was not significant between CAPD and APD patients. APD is associated with a lower risk of technique failure than CAPD, particularly for male patients, and patients aged 50–65 years, with diabetes, without CVD, with high or high average peritoneal permeability, or initiating PD in an earlier era.

Dialysate glucose response phenotypes during peritoneal equilibration test and their association with cardiovascular death: A cohort study

Different measures of rates of transfer of glucose during the peritoneal equilibrium test (PET), undertaken during peritoneal dialysis (PD) might provide additional information regarding a patient's risk of future cardiovascular mortality. This study aimed to characterize the heterogeneity of dialysate glucose (DG) response phenotypes during the PET and compare the cardiovascular mortality rates associated with the different phenotypes. Our cohort was derived from Henan peritoneal dialysis registry. A total of 3477 patients initiating PD in 2007 to 2014 had the DG measured at 0, 2-hour and 4-hour (D0, D2, and D4 respectively) during the PET for estimation of D2/D0 and D4/D0. Deaths mainly due to CVD within 2 years since the initiation of PD were defined as the outcome. Latent class mixed-effect models were fitted to identify distinct phenotypes of the DG response during the PET. Multivariable unconditional Logistic regression models with adjustment for cardiometabolic risk factors were used to compare the 2-year risk of cardiovascular mortality among patients in the different latent classes. Three distinct DG response phenotypes during the PET were identified. Those with consistently high D2/D0 and D4/D0 ratios had a 1.22 [95% confidence interval: 1.02, 1.35] excess risk of a cardiovascular death within 2 years of commencing PD compared with patients with the lowest D2/D0 ratio and decreased D4/D0 ratio after adjustment for cardiometabolic risk factors. Consistently elevated D2/D0 and D4/D0 ratios during the PET are associated with an increased risk of 2-year cardiovascular mortality independent of other cardiometabolic risk factors. In view of the potential bias due to unmeasured confounders (eg, Family history of cardiovascular diseases, and dietary patterns), this association should be further validated in other external cohorts.

High Peritoneal Permeability is Not Associated with Higher Mortality or Technique Failure in Patients on Automated Peritoneal Dialysis

Background

Patients on continuous ambulatory peritoneal dialysis (CAPD) who have high small-molecule peritoneal transport have increased mortality.

Objective

To investigate the impact of baseline peritoneal transport characteristics on patient and technique survival in incident peritoneal dialysis (PD) patients, most of whom are on automated PD (APD), with the use of icodextrin.

Design

Retrospective observational cohort study.

Setting

A single PD unit.

Patients and Methods

193 new patients that began PD between January 2000 and September 2004, and had an initial peritoneal equilibration test within 6 months of commencement of PD. Patients were divided into low (L), low average (LA), high average (HA), and high (H) peritoneal transport groups. Death-censored technique failure and patient survival were examined.

Results

Of the 193 patients, 151 (78.1%) were on APD or on APD with icodextrin or on CAPD with icodextrin. At the end of 1, 3, and 5 years, patient survival was 91%, 82%, and 67% in LA group; 95%, 77%, and 69% in HA group; and 96%, 71%, and 71% in H group. Technique survival was 100%, 90%, and 77% in LA group; 96%, 84%, and 72% in HA group; and 92%, 87%, and 77% in H group. High peritoneal permeability did not predict worse patient survival or technique failure, while age, diabetes, a lower glomerular filtration rate, and high body mass index (≥ 30 kg/m2) were independent predictors of death.

Conclusion

This study suggests that higher peritoneal transport is not a significant independent risk factor for either mortality or death-censored technique failure. The favorable outcome for high transporters in this study may be due to improved management of volume status by the increased use of APD and the use of icodextrin-based dialysis fluid.

Icodextrin Versus Glucose Solutions for the Once-Daily Long Dwell in Peritoneal Dialysis: An Enriched Systematic Review and Meta-analysis of Randomized Controlled Trials

RATIONALE & OBJECTIVE

The efficacy and safety of icodextrin versus glucose-only peritoneal dialysis (PD) regimens is unclear. The aim of this study was to compare once-daily long-dwell icodextrin versus glucose among patients with kidney failure undergoing PD.

STUDY DESIGN

Systematic review of randomized controlled trials (RCTs), enriched with unpublished data from investigator-initiated and industry-sponsored studies.

SETTING & STUDY POPULATIONS

Individuals with kidney failure receiving regular PD treatment enrolled in clinical trials of dialysate composition.

SELECTION CRITERIA FOR STUDIES

Medline, Embase, CENTRAL, Ichushi Web, 10 Chinese databases, clinical trials registries, conference proceedings, and citation lists from inception to November 2018. Further data were obtained from principal investigators and industry clinical study reports.

DATA EXTRACTION

2 independent reviewers selected studies and extracted data using a prespecified extraction instrument.

ANALYTIC APPROACH

Qualitative synthesis of demographics, measurement scales, and outcomes. Quantitative synthesis with Mantel-Haenszel risk ratios (RRs), Peto odds ratios (ORs), or (standardized) mean differences (MDs). Risk of bias of included studies at the outcome level was assessed using the Cochrane risk-of-bias tool for RCTs.

RESULTS

19 RCTs that enrolled 1,693 participants were meta-analyzed. Ultrafiltration was improved with icodextrin (medium-term MD, 208.92 [95% CI, 99.69-318.14] mL/24h; high certainty of evidence), reflected also by fewer episodes of fluid overload (RR, 0.43 [95% CI, 0.24-0.78]; high certainty). Icodextrin-containing PD probably decreased mortality risk compared to glucose-only PD (Peto OR, 0.49 [95% CI, 0.24-1.00]; moderate certainty). Despite evidence of lower peritoneal glucose absorption with icodextrin-containing PD (medium-term MD, -40.84 [95% CI, -48.09 to-33.59] g/long dwell; high certainty), this did not directly translate to changes in fasting plasma glucose (-0.50 [95% CI, -1.19 to 0.18] mmol/L; low certainty) and hemoglobin A_1c levels (-0.14% [95% CI, -0.34% to 0.05%]; high certainty). Safety outcomes and residual kidney function were similar in both groups; health-related quality-of-life and pain scores were inconclusive.

LIMITATIONS

Trial quality was variable. The follow-up period was heterogeneous, with a paucity of assessments over the long term. Mortality results are based on just 32 events and were not corroborated using time-to-event analysis of individual patient data.

CONCLUSIONS

Icodextrin for once-daily long-dwell PD has clinical benefit for some patients, including those not meeting ultrafiltration targets and at risk for fluid overload. Future research into patient-centered outcomes and cost-effectiveness associated with icodextrin is needed.

Associations Between Peritoneal Glucose Exposure, Glucose Degradation Product Exposure, and Peritoneal Membrane Transport Characteristics in Peritoneal Dialysis Patients: Secondary Analysis of the balANZ Trial

BACKGROUND

Glucose is the most commonly used osmotic medium in peritoneal dialysis (PD) solutions, and its use has been associated with both local and systemic adverse effects. Previous, single-center, observational cohort studies have reported conflicting findings regarding whether a relationship exists between peritoneal glucose exposure and peritoneal small solute transport rate.

METHODS

In this secondary analysis of the balANZ multicenter, multinational, randomized controlled trial of a neutral pH, ultra-low glucose degradation product (biocompatible) versus conventional PD solutions over a 2-year period, the relationship between time varying peritoneal glucose exposure and change in peritoneal solute transport rate, (measured as dialysate to plasma creatinine ratio at 4 hours [D:PCr_4h]), was evaluated using multivariable, multilevel linear regression. Baseline peritoneal glucose exposure was also assessed as either a continuous or categorical variable.

RESULTS

The study included 165 patients (age 58.1 ± 14.2 years, 55% male, 33% diabetic). Peritoneal glucose exposure increased over time (coefficient 1.49, 95% confidence interval [CI] 1.07 - 1.92 and was not significantly associated with change in D:PCr_4h (coefficient 0.00004, 95% CI -0.0001 - 0.0002, p = 0.68). Similar results were found when peritoneal glucose exposure was examined as a baseline continuous or categorical variable. A significant 2-way interaction was observed with PD solution type, whereby a progressive increase in D:PCr_4h was seen in the patients receiving conventional PD solution, but not in those receiving biocompatible solution.

CONCLUSIONS

Increases in peritoneal solute transport rate in PD patients over time were not associated with peritoneal glucose exposure, although a strong and positive association with PD solution glucose degradation product content was identified. Peritoneal glucose exposure may be a less important consideration than peritoneal glucose degradation product exposure with respect to peritoneal membrane function over time.

Dialysate Creatinine Response Patterns During Peritoneal Equilibration Test and the Association Between Cardiovascular Mortality: Findings from a Prospective Cohort Study

BACKGROUND/AIMS

During peritoneal equilibrium test (PET), intermediate measures of Dt/P (dialysate/plasma creatinine ratio), D0/P, D2/P and D4/P ratios might provide additional information regarding a patient's cardiovascular mortality. We aimed to characterise heterogeneity of dialysate creatinine response patterns based on three ratios and compare cardiovascular mortality risks by response patterns.

METHODS

3,477 patients initialising peritoneal dialysis (PD) between 2007-2015 were measured D0/P, D2/P and D4/P at baseline and 2-year cardiovascular mortality was defined as the primary outcome. Latent class mixed-effect models were fitted to identify distinct patterns of dialysate creatinine response. Multivariable Logistic regression model with adjustment of cardiometabolic factors were used to compare cardiovascular mortality by latent classes.

RESULTS

The 1st latent class including 36% of participants was characterised by consistently increasing and high Dt/P ratios both at 2-hour and 4-hour. The 2nd class including 61% of participants characterised by sharply increased ratio at 2-hour and slightly increased ratio at 4-hour. The 3rd class included 3% of participants with decreased ratio at 2-hour and increased ratio at 4-hour. Comparing the 1st class, the lower cardiovascular mortality risk was identified in the 2nd and 3rd class with adjusted odds ratio 0.65 (95% confidence interval: 0.62-0.69) and 0.48 (0.41-0.57), respectively.

CONCLUSION

Patients with decreased Dt/P ratio between 0-hour and 2-hour and low ratios at 2-hour and 4-hour tend to have low cardiovascular mortality. Latent class analysis seems to be a promising method to reveal unidentified subgroups that do not fit into the risk category defined by Dt/P ratio at 4-hour.

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.

Current trends in European renal epidemiology

The incidence of end-stage renal disease (ESRD) continues to vary substantially between the countries in Europe that contribute data to the ERA-EDTA Registry. Differences can be attributed to socioeconomic factors and prophylaxis programs for patients with chronic kidney disease (CKD) and may also express real differences in CKD incidence. Recently, age-adjusted ESRD incidence has begun to fall in many countries, probably related to improved prophylaxis. However, absolute rates may increase, partly due to socioeconomic advances in countries with a low gross domestic product and partly due to continuing increases in the proportion of elderly patients. Prevalence rates are expected to continue to increase, mainly due to increases in relative transplant prevalence, improved graft survival times and continuing improvements in both dialysis and transplant patient survival. Overall treatment results continue to improve.

Peritoneal Equilibration Test and Patient Outcomes

BACKGROUND AND OBJECTIVES

Although a peritoneal equilibration test yields data on three parameters (4-hour dialysate/plasma creatinine, 4- to 0-hour dialysate glucose, and 4-hour ultrafiltration volume), all studies have focused on the prognostic value of dialysate/plasma creatinine for patients undergoing peritoneal dialysis. Because dialysate 4- to 0-hour glucose and ultrafiltration volume may be superior in predicting daily ultrafiltration, the likely mechanism for the association of peritoneal equilibration test results with outcomes, we hypothesized that they are superior to dialysate/plasma creatinine for risk prediction.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We examined unadjusted and adjusted associations of three peritoneal equilibration test parameters with all-cause mortality, technique failure, and hospitalization rate in 10,142 patients on peritoneal dialysis treated between January 1, 2007 and December 31, 2011 in 764 dialysis facilities operated by a single large dialysis organization in the United States, with a median follow-up period of 15.8 months; 87% were treated with automated peritoneal dialysis.

RESULTS

Demographic and clinical parameters explained only 8% of the variability in dialysate/plasma creatinine. There was a linear association between dialysate/plasma creatinine and mortality (adjusted hazards ratio per 0.1 unit higher, 1.07; 95% confidence interval, 1.02 to 1.13) and hospitalization rate (adjusted incidence rate ratio per 0.1 unit higher, 1.05; 95% confidence interval, 1.03 to 1.06). Dialysate/plasma creatinine and dialysate glucose were highly correlated (r=-0.84) and yielded similar risk prediction. Ultrafiltration volume was inversely related with hospitalization rate but not with all-cause mortality. None of the parameters were associated with technique failure. Adding 4- to 0-hour dialysate glucose, ultrafiltration volume, or both did not result in any improvement in risk prediction with dialysate/plasma creatinine alone.

CONCLUSIONS

This analysis from a large contemporary cohort treated primarily with automated peritoneal dialysis validates dialysate/plasma creatinine as a robust predictor of outcomes in patients treated with peritoneal dialysis.

Measuring peritoneal absorption with the prolonged peritoneal equilibration test from 4 to 8 hours using various glucose concentrations

BACKGROUND

Peritoneal fluid flows such as small-pore ultrafiltration and free water transport can now be calculated by means of the modified peritoneal equilibration test (PET). To calculate peritoneal fluid absorption, volume markers have been used, but that method is not easily applicable in clinical practice. Alternatively, absorption can be estimated using the personal dialysis capacity test. However, a method of measuring overall peritoneal absorption together with the PET is lacking. The aim of the present study was to assess whether overall peritoneal absorption was different when measured from the 4th to 8th hour in a prolonged PET using three different glucose solutions.

METHODS

The study enrolled 32 stable peritoneal dialysis (PD) patients from a tertiary university hospital, who underwent three 8-hour prolonged PETs with 1.36%, 2.27%, and 3.86% glucose solution. The PETs were performed in random order over a period of less than 1 month. During the prolonged PET, the peritoneal volume was emptied and reinfused at 60 and 240 minutes and drained at 480 minutes. Peritoneal absorption was calculated as the volume difference between the 4th and the 8th hour.

RESULTS

The dialysate-to-plasma ratio (D/P) of urea, the D/P creatinine, and the mass transfer area coefficient (MTC) of creatinine at 240 minutes were not significantly different with the three glucose solutions. The end-to-initial (D/D0) glucose, MTC urea, and MTC glucose were significantly different. All water transport parameters were significantly different, except for the 4- to 8-hour absorption volumes and rates. The peritoneal absorption rates were, for 1.36% solution, 1.03 ± 0.58 mL/min [95% confidence interval (CI): 0.83 to 1.24 mL/min]; for 2.27% solution, 0.86 ± 0.71 mL/min (95% CI: 0.61 to 1.11 mL/min); and for 3.86% solution, 1.05 ± 0.78 mL/min (95% CI: 0.77 to 1.33 mL/min). Peritoneal absorption volumes and rates from the 4th to the 8th hour showed good correlations for the various solutions.

CONCLUSIONS

Using any glucose solution, the prolonged PET with voiding and reinfusion at the 4th hour could be a practical method for calculating overall peritoneal absorption from the 4th to the 8th hour in PD patients.

Higher Dialysate Matrix Metalloproteinase-2 Levels Are Associated with Peritoneal Membrane Dysfunction

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BACKGROUND

Peritoneal dialysis (PD) patients develop progressive and cumulative peritoneal injury with longer time spent on PD. The present study aimed to a) describe the trend of peritoneal injury biomarkers, matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-1 (TIMP-1), in incident PD patients, b) to explore the capacity of dialysate MMP-2 to predict peritoneal solute transport rate (PSTR) and peritonitis, and c) to evaluate the influence of neutral pH, low glucose degradation product (GDP) PD solution on these outcomes. ♦

METHODS

The study included 178 participants from the balANZ trial who had at least 1 stored dialysate sample. Changes in PSTR and peritonitis were primary outcome measures, and the utility of MMP-2 in predicting these outcomes was analyzed using multilevel linear regression and multilevel Poisson regression, respectively. ♦

RESULTS

Significant linear increases in dialysate MMP-2 and TIMP-1 concentrations were observed (p < 0.001), but neither was affected by the type of PD solutions received (MMP-2: p = 0.07; TIMP-1: p = 0.63). An increase in PSTR from baseline was associated with higher levels of MMP-2 (p = 0.02), and the use of standard solutions over longer PD duration (p = 0.001). The risk of peritonitis was independently predicted by higher dialysate MMP-2 levels (incidence rate ratio [IRR] per ng/mL 1.01, 95% confidence interval [CI] 1.005 - 1.02, p = 0.002) and use of standard solutions (Biocompatible solution: IRR 0.45, 95% CI 0.24 - 0.85, p = 0.01). ♦

CONCLUSION

Dialysate MMP-2 and TIMP-1 concentrations increased with longer PD duration. Higher MMP-2 levels were associated with faster PSTR and future peritonitis risk. Administration of biocompatible solutions exerted no significant effect on dialysate levels of MMP-2 or TIMP-1, but did counteract the increase in PSTR and the risk of peritonitis associated with the use of standard PD solutions. This is the first longitudinal study to examine the clinical utility of MMP-2 as a predictor of patient-level outcomes.

Automated peritoneal dialysis prescriptions for enhancing sodium and fluid removal: a predictive analysis of optimized, patient-specific dwell times for the day period

BACKGROUND

Remaining edema-free is a challenge for many automated peritoneal dialysis (APD) patients, especially those with fast ("high") transport characteristics. Although increased use of peritoneal dialysis (PD) solutions with high glucose concentrations may improve volume control, frequent use of such solutions is undesirable.

METHODS

We used the 3-pore kinetic model to evaluate 4 alternative therapy prescriptions for the APD day exchange in anuric patients with high, high-average, and low-average transport characteristics. Four prescriptions were modeled: Therapy 1: Optimal, individualized dwell times with a dry period. Therapy 2: Use of a midday exchange. Therapy 3: Use of an icodextrin-containing dialysate during a 14-hour dwell. Therapy 4: Use of optimal, individualized dwell times, followed by an icodextrin dwell to complete the daytime period. The alternative therapies were compared with a reference standard therapy using glucose solution during a 14-hour dwell. The nighttime prescription was identical in all cases (10 L over 10 hours), and all glucose solutions contained 2.27% glucose. Net ultrafiltration (UF), sodium removal (NaR), total carbohydrate (CHO) absorption, and weekly urea Kt/V for a 24-hour period were computed and compared.

RESULTS

The UF and NaR were substantially higher with therapy 1 than with standard therapy (1034 mL vs 621 mL and 96 mmol vs 51 mmol respectively), without significant changes in CHO absorption or urea Kt/V. However, therapy 1 resulted in reduced β2-microglobulin clearance (0.74 mL/min vs 0.89 mL/min with standard therapy). Compared with therapy 1, therapy 2 improved UF and NaR (1062 mL vs 1034 mL and 99 mmol vs 96 mmol); however, that improvement is likely not clinically significant. Therapy 2 also resulted in a higher Kt/V (2.07 vs 1.72), but at the expense of higher glucose absorption (difference: 42 g). The UF and NaR were highest with a long icodextrin-containing daytime dwell either preceded by a short optimized dwell (1426 mL and 155 mmol) or without such a dwell (1327 mL and 148 mmol).

CONCLUSIONS

The 3-pore model predictions revealed that patient-specific optimal dwell times and regimens with a longer day dwell might provide improved UF and NaR options in APD patients with a variety of peritoneal membrane transport characteristics. In patients without access to icodextrin, therapy 1 might enhance UF and NaR and provide a short-term option to increase fluid removal. Although that approach may offer clinicians a therapeutic option for the overhydrated patient who requires increased UF in the short term, APD prescriptions including icodextrin provide a means to augment sodium and fluid removal. Data from clinical trials are needed to confirm the predictions from this study.

Icodextrin Simplifies PD Therapy by Equalizing UF and Sodium Removal Among Patient Transport Types During Long Dwells: A Modeling Study

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BACKGROUND

In recent years, results from clinical studies have changed the focus of peritoneal dialysis (PD) adequacy from small solute clearance to volume control, resulting in continued efforts to improve fluid and sodium removal in PD patients. We used a modified 3-pore model to theoretically predict fluid and solute removal using glucose-based and icodextrin solutions for a wide range of transport characteristics with automated PD (APD) and continuous ambulatory PD (CAPD) therapies. ♦

METHODS

Simulations were performed for the day (APD: 15-hr, 2.27% glucose and 7.5% icodextrin; CAPD: 3x5-hr, 1.36% and 2.27% glucose) and night (APD: 9-hr, 1.36% glucose; CAPD: 9-hr, 2.27% glucose and 7.5% icodextrin) dialysis periods separately. During APD, the number of night exchanges (N) was varied from 3 to 7. Ultrafiltration (UF), sodium removal (NaR), total carbohydrate absorption (CHO), UF efficiency (UFE), and sodium removal efficiency (NaRE) were calculated. Typical patients in fast (i.e. high, H), average (high-average, HA; low-average, LA), and slow (low, L) transport groups with no residual kidney function were considered. ♦

RESULTS

The effective dwell times varied between 1.0 and 14.7 hours depending on the number of exchanges. With glucose-based solutions, differences in UF and NaR between H and L transport patients ranged from 140 mL and 2 mmol (APD night, n = 7) to 778 mL and 56.4 mmol (CAPD day, 2.27%). With icodextrin, differences in UF and NaR ranged from 1 mL and 1.1 mmol (CAPD night) to 59 mL and 6.1 mmol (APD day). The use of icodextrin resulted in greater CHO than 2.27% glucose (APD: 27.1 - 35.6 g more; CAPD: 17.1 - 17.5 g more). The UFE and NaRE were greater for all patients with icodextrin than with glucose-based solution in both therapy modalities, except for slow transport patients in CAPD. ♦

CONCLUSION

This modeling study shows that the dependence of UF and NaR on patient transport type observed with glucose-based solutions can be minimized using icodextrin during the long dwells of APD and CAPD. While this approach simplifies the PD prescription by minimizing the dependencies of ultrafiltration and sodium removal on patient transport type when using icodextrin, it improves fluid and sodium removal efficiencies in fast and average transport patients without any added glucose exposure.

Relative survival of peritoneal dialysis and haemodialysis patients: effect of cohort and mode of dialysis initiation

INTRODUCTION

Epidemiological studies consistently show an initial survival advantage for PD patients compared to HD. It has recently been suggested that this is due to the fact that many HD patients are referred late, and start dialysis on an acute, in-patient basis. The present study was performed to investigate (1) whether, and if so, how, PD and HD prognosis had changed in recent years, (2) whether a potential survival advantage of PD versus HD is constant over dialysis duration, and (3) whether differences in prognosis could be explained by patient age, renal diagnosis of diabetic nephropathy, or mode of dialysis initiation.

PATIENTS AND METHODS

12095 patients starting dialysis therapy between 1990 and 2010 in Denmark were studied. Prognosis was assessed according to initial dialysis modality on an intention-to-treat basis, censored for transplantation. Results were adjusted for age, sex, renal diagnosis, Charlson Comorbidity Index (CCI), and mode of dialysis initiation.

RESULTS

Overall adjusted prognosis improved by 34% (HD 30%, PD 42%). PD prognosis relative to HD improved, and was 16% better at the end of the period. Final PD prognosis improved consistently from 1990-99 to 2000-10 in all subgroups. PD was associated with a significant initial survival advantage, both overall and for all subgroups For the latter cohort, overall PD prognosis was better than HD for the first 4 years, after which it was insignificantly worse. The initial survival advantage was also present in a subgroup analysis of patients with early & routine ESRD initiation.

CONCLUSIONS

Dialysis survival has increased during the past 20 years. PD survival since 2000 has been better than HD, overall and for all subgroups. The difference in survival is not explained by mode of dialysis initiation.

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

Background

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

Methods

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

Results

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

Conclusion

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

Peritoneal dialysis--current status and future challenges

Peritoneal dialysis is now a well established, mature treatment modality for advanced chronic kidney disease. The medium term (at least 5 year) survival of patients on peritoneal dialysis is currently equivalent to that of those on haemodialysis, and is particularly good in patients who are new to renal replacement therapy and have less comorbidity. Nevertheless the modality needs to keep pace with the constantly evolving challenges associated with the provision and delivery of health care. These challenges, which are gradually converging at a global level, include ageing of the population, multimorbidity of patients, containment of cost, increasing self care and environmental issues. In this context, peritoneal dialysis faces particular challenges that include multiple barriers to the therapy and unsatisfactory and poorly defined technique survival as well as limitations relating to intrinsic aspects of the therapy, such as peritoneal membrane longevity and hypoalbuminaemia. To move the therapy forward and favourably influence health-care policy, the peritoneal dialysis community needs to integrate their research effort more effectively by undertaking clinically meaningful studies-with a strong focus on technique survival--that are supported by multidisciplinary expertise in patient-centred outcomes, study design and analysis.

Comparative Role of PET and Kt/V Determination in Pediatric Chronic Peritoneal Dialysis

Introduction

Nutritional state and growth are considered as prognostic markers of chronic peritoneal dialysis (PD) adequacy in pediatric patients. The euvolemia, blood pressure control, and metabolic and electrolytic equilibrium are parameters to be achieved by PD treatment.

Objective

To describe the chronic PD prescription parameters of a cohort of pediatric patients and to compare the obtained hemodynamic, antrophometric and adequacy results with those suggested by the literature.

Methods

Retrospective analysis based on clinical records evaluation of 30 pediatric patients undergoing PD for more than 6 months from January 1998 to May 2005.

Results

In the present study, 17/30 (56.7%) were boys. Chronic kidney disease was secondary to uropathy in 66.7% of the cases. The infusion volume was > 1,000 ml/m2 in 9 patients. The peritoneal membrane was characterized as high (27.8%), high-average (33.3%), low-average (22.2%) and low transporter (16.7%). The weekly urea Kt/V was > 2.1 in all the evaluated patients. Blood pressure parameters above the 95th percentile despite the use of antihypertensive medication were observed in 5/30 patients, four of whom with CKD secondary to glomerulopathy. The initial and final Body Mass Index and weight for height ratio were preserved in 83.3% (25/30) patients.

Conclusion

Elevated indexes of small solutes removal are easily attained in pediatric PD patients and do not imply optimal clinical management do not imply optimal climanagement.

Determinants of peritoneal membrane function over time

Changes to peritoneal membrane function over time result in the development of ultrafiltration failure in a proportion of PD patients and pose a risk for the rarer condition of encapsulating peritoneal sclerosis. These changes are characterized by an increase in the transport rate for small solutes owing to increased vascularity and/or peritoneal blood flow and in more severe cases a reduction in the osmotic conductance of the membrane that likely reflects progressive fibrosis. Both of these processes are preceded by exposure of the membrane to glucose when using conventional dialysis solutions, although this usually is necessitated and likely exacerbated by loss of residual renal function and recurrent peritonitis. Mediators of membrane injury and thus potential biomarkers include inflammatory cytokines, notably local interleukin-6 production, which also appears to determine solute transport characteristics at the start of peritoneal dialysis, local production of vascular endothelial growth factor, and transforming growth factor β-associated epithelial to mesenchymal transition of the mesothelium leading to membrane fibrosis. Low glucose degradation product solutions may ameliorate the mesothelial injury associated with high glucose exposure, but evidence that they prevent or delay changes in membrane function over time is lacking. In the meantime, avoidance of excessive glucose exposure, preservation of residual renal function, and prevention of peritonitis remain the most logical treatment strategies for this problem.

Three-pore model predictions of 24-hour automated peritoneal dialysis therapy using bimodal solutions

BACKGROUND

Recently, bimodal peritoneal dialysis (PD) solutions containing low concentrations of Na have been shown to increase 24-hour ultrafiltration (UF) or UF efficiency (UF volume per gram of carbohydrate or CHO absorbed) and Na removal in high ("fast") transport patients during automated PD therapy. We used computer simulations to compare UF efficiency and Na removal at equivalent 24-hour UF volumes using either a generic bimodal solution (2.27% glucose + 7.5% icodextrin) during the long dwell or an increase in the glucose concentration during the short dwells, with all solutions containing Na at the conventional concentration (132 mEq/L).

METHODS

The 3-pore model has been shown to accurately predict peritoneal transport for PD solutions containing glucose or icodextrin, or both. Here, we used that model to calculate 24-hour UF volume, CHO absorption, and Na removal for high (H), high-average (HA), and low-average (LA) transport patients on automated PD. Nighttime therapy consisted of 1.36% or 2.27% glucose solution (or both), and daytime therapy consisted of either Extraneal (Baxter Healthcare Corporation, Deerfield, IL, USA) or a bimodal solution.

RESULTS

As expected, addition of glucose to either the long dwell or the short dwells resulted in increased UF volume and glucose absorption. The increase in UF was a function of patient transport type (bimodal range: 288 - 490 mL; short-dwell range: 323 - 350 mL), and the increase in CHO absorption was smaller with glucose added to short dwells than with bimodal solution (range: 18 - 30 g vs. 34 - 39 g). The 24-hour UF efficiency was higher when high glucose concentrations were used during short-dwell exchanges than when a bimodal PD solution was used for the long dwell (0.6 to 1.2 mL/g vs. -0.1 to 0.5 mL/g). By contrast, Na removal was lower with the short-dwell exchanges (28.3 - 30.7 mmol vs. 36.2 - 53.3 mmol), likely because of more pronounced Na sieving.

CONCLUSIONS

Our modeling studies predict that generic bimodal PD solutions will provide higher Na removal but not higher 24-hour UF efficiency compared with current automated PD prescriptions using Extraneal for the long dwell and glucose-containing solutions for the short dwells. The modeling predictions from this study require clinical validation.

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.

High peritoneal transport status is not an independent risk factor for high mortality in patients treated with automated peritoneal dialysis

We undertook this study to elucidate whether baseline peritoneal membrane transport characteristics are associated with high mortality in incident automated peritoneal dialysis (APD) patients. This retrospective study includes 117 patients who started APD at Yonsei University Health System from 1996 to 2008 and had a PET within 3 months of APD initiation. High transporters were significantly older and had a higher incidence of cardiovascular disease. Patient survival for years 1, 3, and 5 were 85%, 64%, and 35% for high transporter and 94%, 81%, and 68% for non-high transporter group (P<0.01). Multivariate analysis revealed that age, diabetes, cardiovascular disease, serum albumin level, and residual renal function were independently associated with high mortality in APD patients. In contrast, high transport status was not a significant predictor for mortality in this population when the other covariates were included. Even though high transport was significantly associated with mortality in the univariate analysis, its role seemed to be influenced by other comorbid conditions. These findings suggest that the proper management of these comorbid conditions, as well as appropriate ultrafiltration by use of APD and/or icodextrin, must be considered as protective strategies to improve survival in peritoneal dialysis patients with high transport.

An update on renal replacement therapy in Europe: ERA-EDTA Registry data from 1997 to 2006

BACKGROUND

Recent studies have indicated a stabilization in the incidence rates of renal replacement therapy (RRT) for end-stage renal disease (ESRD) in a number of European countries. The aim of this study was to provide an update on the incidence, prevalence and outcomes of RRT in Europe over the past decade.

METHODS

Nineteen European national or regional renal registries with registry data from 1997 to 2006 participated in the study. Incidence and prevalence trends were analysed with Poisson and Joinpoint regression. Cox regression methods were used to examine patient survival.

RESULTS

The total adjusted incidence rate of RRT for ESRD increased from 109.9 per million population (pmp) in 1997 to 119.7 pmp in 2000, i.e. an average annual percentage change (AAPC) of 2.9% (95% CI 2.1-3.8%). Thereafter, the incidence increased at a much lower rate to 125.4 pmp in 2006 [AAPC 0.6% (95% CI 0.3-0.8%)]. This change in the trend of the incidence of RRT was largely due to a stabilization in the incidence rates of RRT for females aged 65-74 years, males aged 75-84 years and patients receiving RRT for ESRD due to hypertension/renal vascular disease. The overall adjusted prevalence in Europe continued to increase linearly at 2.7% per year. Between the periods 1997-2001 and 2002-2006, the risk of death decreased for all treatment modalities, with the most substantial improvement in patients starting peritoneal dialysis [19% (95% CI 15-22%)] and in patients receiving a kidney transplant [17% (95% CI 11-23%)].

CONCLUSION

This European study shows that the annual rise of the overall incidence rate of RRT for ESRD has diminished and that in several age groups the incidence rates have now stabilized. The survival of dialysis patients and kidney transplant recipients has continued to improve.

A Combined Crystalloid and Colloid PD Solution as a Glucose-Sparing Strategy for Volume Control in High-Transport APD Patients: A Prospective Multicenter Study

Background

Evidence is accumulating that the continuous exposure to high glucose concentrations during peritoneal dialysis (PD) is an important cause of ultrafiltration (UF) failure. The cornerstone of prevention and treatment of UF failure is reduction of glucose exposure, which will also alleviate the systemic impact of significant free glucose absorption. The challenge for the future is to discover new therapeutic strategies to enhance fluid and sodium removal while diminishing glucose load and exposure using combinations of available osmotic agents.

Objectives

To investigate in patients on automated PD (APD) with a fast transport pattern whether there is a glucose-sparing advantage to replacing 7.5% icodextrin (ICO) during the long dwell with a mixed crystalloid and colloid PD fluid (bimodal UF) in an attempt to promote daytime UF and sodium removal while diminishing the glucose strength of the dialysate at night.

Design

A 2 parallel arm, 4 month, prospective nonrandomized study.

Setting

PD units or university hospitals in 4 French and Belgian districts.

Results

During the 4-month intervention period, net UF and peritoneal sodium removal during the long dwell when treated by bimodal UF was about 2-fold higher than baseline (with ICO). The estimated percent change (95% confidence interval) from baseline in net daytime UF for the bimodal solution was 150% (106% – 193%), versus 18% (–7% – 43%) for ICO ( p < 0.001). The estimated percent change from baseline in peritoneal sodium removal for the bimodal solution was 147% (112% – 183%), versus 23% (–2% – 48%) for ICO ( p < 0.001). The estimated percent change from baseline in UF efficiency (24-hour net UF divided by the amount of glucose absorbed) was significantly higher ( p < 0.001) when using the bimodal solution was 71%, versus -5% for ICO.

Conclusion

Prescription of bimodal UF during the day in APD patients offers the opportunity to optimize the long dwell exchange in a complete 24-hour APD cycle. The current study demonstrated that a bimodal solution based on the mixing of glucose (2.6%) and icodextrin (6.8%) achieved the double target of significantly improving UF and peritoneal sodium removal by exploring a new concept of glucose-sparing PD therapy.

The Variability in Ultrafiltration Achieved with Icodextrin, Possibly Explained

Background

A recent study by Jeloka et al. (Perit Dial Int 2006; 26:336–40) highlighted the high variability in maximum ultrafiltered volume (UFmax) and the corresponding dwell time (tmax) obtained using 7.5% icodextrin solution. We aimed to pinpoint the possible sources of this phenomenon by simulating the icodextrin ultrafiltration (UF) profiles according to the three-pore model of peritoneal transport.

Method

The individual UF time courses observed in the study by Jeloka et al. ( n = 29) were first characterized by linear and quadratic regression. We were then able to identify four main patterns. These were then adapted to UF profiles generated by the three-pore model by systematically altering the values of some model parameters, namely, the mass transfer area coefficient (MTAC or PS) for icodextrin/glucose, the peritoneal UF coefficient (LpS), the plasma colloid osmotic pressure gradient (ΔΠ), and the macromolecular clearance out of the peritoneal cavity (ClLF).

Results

Modifications in the PS values caused only marginal variations in UFmax and tmax, while more significant changes were produced by altering LpS and ClLF. However, far more evident was the importance of changes in ΔΠ In fact, lowering ΔΠ to 14 mmHg caused a steady increase in UF with 10 – 14 hour dwells. On the contrary, the UF profiles became nearly “flat” when ΔΠ was increased to 30 mmHg. The parallel shifts induced by altering icodextrin metabolite concentrations did not markedly influence UFmax or tmax.

Conclusion

The UF pattern in icodextrin dwells seem to be mainly determined by the plasma colloid osmotic pressure, while only moderate changes can be seen with alterations in LpS and ClLF. The result is not completely unexpected considering that icodextrin acts by inducing a strong colloid osmotic gradient. A number of clinical studies would be needed, however, in order to prove this hypothesis.

Hydration status does not influence peritoneal equilibration test ultrafiltration volumes

BACKGROUND AND OBJECTIVES

The peritoneal equilibration test (PET) was developed some 25 yr ago and has been used to help prescribe peritoneal dialysis. However, PET is affected by several factors, including diabetes and inflammation. It was speculated that extracellular fluid overload would increase PET ultrafiltration volumes, and therefore the usefulness of the PET in routine clinical practice was audited.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data from 211 consecutive patients attending a university teaching hospital for a standard PET who had multifrequency bioimpedance performance were analyzed to determine which factors affected net PET ultrafiltration volumes.

RESULTS

Net PET ultrafiltration volume was independent of gender, age, diabetes, residual renal function, peritoneal dialysis prescriptions (modes and dialysates), extracellular fluid volume, or C-reactive protein (CRP). There was an inverse regression with serum albumin and sodium on multiple logistical regression analysis (F = 13.4, P < 0.001 and F = 10.1, P = 0.001, respectively) and a positive regression with 24-h net peritoneal ultrafiltration volumes (F = 15.5, P < 0.001). As expected, there was a strong correlation with net sodium losses (r = 0.99, P < 0001).

CONCLUSIONS

It was found that PET test ultrafiltration volume in routine clinical practice was not affected by CRP, hyperglycemia, or extracellular fluid volume overload. Ultrafiltration volumes were increased in those patients with reduced serum sodium and albumin, most likely because of inflammation and protein malnutrition.

Rapid Solute Transport in the Peritoneum: Physiologic and Clinical Consequences

This review focuses on the physiologic and clinical consequences of rapid solute transport in the peritoneum. The concept, the current understanding of related factors, and the possible causes implicated in rapid solute transport are discussed first. Then, the consequences, with particular emphasis on mortality, are highlighted. Finally, based on recent advances and clinical studies, some strategies for the treatment of fast peritoneal transport are reviewed.

The contribution of combined crystalloid and colloid osmosis to fluid and sodium management in peritoneal dialysis

The achievement of euvolemia is essential to the successful management of peritoneal dialysis patients. However, the concern that hypertonic glucose exchanges may have a role in long-term changes to the peritoneal membrane has lead to an alternative strategy to enhance ultrafiltration (UF) over the long dwell by combining crystalloid and colloid osmosis. This review summarizes the experience of mixing glucose or amino acids with polyglucose (icodextrin), with particular focus given to data from studies using glucose/icodextrin in combinations of 1.36%/7.5% and 2.61%/6.8%. Both combinations demonstrate a significant increment of UF volume and sodium removal compared with the component osmotic agents used individually over long dwells, with the 2.61%/6.8% mixture having an effect over dwells extending to 15 h. Hypothetically, the mechanism of the enhanced UF is the attenuation by the colloid osmotic force of the backflow of water through small pores from dialysate to the peritoneal capillary circulation once the crystalloid osmotic force has dissipated. This experience provides promising data that deserves further examination in longer term clinical studies.

Peritoneal membrane structural and functional changes during peritoneal dialysis

Peritoneal dialysis is now utilized as a renal replacement therapy modality in a substantial percentage of patients with end-stage renal disease, with excellent short-term patient and technique survival rates. However, the potential complications associated with longer-term therapy, such as ultrafiltration failure or encapsulating peritoneal sclerosis, have led to raise some concern about peritoneal dialysis as an adequate mode of treatment of end-stage renal disease in the long term. In the last decade, a substantial amount of information has been gathered on the characteristics of the peritoneal membrane at the onset of peritoneal dialysis, and on the anatomical and pathophysiologic changes that occur with long-term peritoneal dialysis. I will review this subject with a special focus on the various strategies that can help protect the peritoneal membrane during peritoneal dialysis so as to allow peritoneal dialysis to succeed as a long-term dialysis modality.

Peritoneal challenge modulates expression of pneumococcal surface protein C during bacteremia in mice

Differential expression of pneumococcal virulence proteins has been demonstrated. We previously demonstrated challenge route-dependent differences in pneumococcal surface protein C (PspC) expression during bacteremia. In this study, we investigated differences in PspC expression during the transition of pneumococci from the peritoneum to the blood. Time course analysis of PspC expression using flow cytometry demonstrated that Streptococcus pneumoniae D39 collected from blood expressed significantly more PspC than did D39 collected from the peritoneum of intraperitoneally (i.p.)-infected mice. Various challenge models were then used to determine whether host responses originating from the peritoneum can influence PspC expressed by pneumococci in the blood. Using heat-inactivated D39 (HI-D39) and sterile peritoneal dialysis fluid (PDF), we investigated whether stimulation of peritoneal responses can influence PspC expression. Injection of mice i.p. with HI-D39 or PDF immediately prior to intravenous (i.v.) infection with D39 caused a significant increase in PspC expressed by D39 in the blood. Finally, we used cytokine array analysis to investigate specific inflammatory mediators that may result in differential PspC expression. Of the 96 inflammatory cytokines assayed, D39 i.p. challenge led to increased expression of 33 cytokines in serum; whereas D39 i.v. challenge led to increased expression of 15 and decreased expression of 11 cytokines relative to serum of the uninfected control. These results indicate that PspC is differentially regulated during growth in vivo and that the level of expression varies depending on the host environment.