Comparison of fast peritoneal equilibration tests with 1.36 and 3.86% dialysis solutions

Influence of peritoneal residual volume on the results of the peritoneal equilibration test. Prospective study

BACKGROUND

Categorization of the capacity of ultrafiltration during a peritoneal equilibration test (PET) is a usual step during the monitoring of peritoneal transport characteristics of Peritoneal Dialysis (PD) patients. Quantifying the peritoneal residual volume (Vr) after the dwell preceding the PET (Vrpre) and at the end of the test (Vrpost) could help to improve the accuracy of the estimation of this variable.

METHOD

Following a prospective design, we calculated Vrpre and Vrpost in 116 patients, incident or prevalent on DP, who underwent one or two (n = 27) PET with 3,86/4,25% glucose-based PD solutions and complete drainage at 60 min. We evaluated the consistency of Vr by comparing Vrpre and Vrpost, as also these two parameters in repeated tests. We scrutinized potential associations between demographic and clinical factors, on one side, and the amount of Vr on the other, as also the impact of correcting ultrafiltration during PET for Vr on the categorization of the capacity of ultrafiltration.

RESULTS

As a mean, Vrpost was larger than Vrpre. Consequently, correction of ultrafiltration for Vr resulted in significantly higher values than those obtained according to the standard procedure (494 vs. 449 mL, p < 0,0005). We disclosed marked inconsistencies for different estimations of Vr in the same patients (Vrpre vs Vrpost and repeated PET studies). Moreover, no demographic or clinical variable was able to predict the amount of Vr. We observed a significant deviation (>200 mL) between both methods of estimation of the capacity of utrafiltration in only 12,9% of the patients. However, 21,1% of the patients categorized as cases of ultrafiltration failure according to the standard procedure did not maintain this condition after correction for Vr.

CONCLUSIONS

Correction for Vr of the capacity of ultrafiltration during a PET carries, as a mean, a minor impact on the categorization of this parameter. However, the results of the test can be significantly affected in 12,9% of the cases. We have been unable to detect demographic or clinical predictors of Vr, which suggests a random component for the mechanics of single peritoneal exchanges. We suggest that Vr should be estimated at the time of categorizing the capacity of ultrafiltration, whenever inconsistencies during serial PET studies are detected.

Traduction des Recommandations de l'ISPD pour l'évaluation du dysfonctionnement de la membrane péritonéale chez l'adulte

Informations concernant cette traductionDans le cadre d’un accord de partenariat entre l’ISPD et le RDPLF, le RDPLF est le traducteur français officiel des recommandations de l’ISPD. La traduction ne donne lieu à aucune compensation financière de la part de chaque société et le RDPLF s’est engagé à traduire fidèlement le texte original sous la responsabilité de deux néphrologues connus pour leur expertise dans le domaine. Avant publication le texte a été soumis à l’accord de l’ISPD. La traduction est disponible sur le site de l’ISPD et dans le Bulletin de la Dialyse à Domicile.Le texte est, comme l’original, libremement téléchargeable sous licence copyright CC By 4.0https://creativecommons.org/licenses/by/4.0/Cette traduction est destinée à aider les professionnels de la communauté francophone à prendre connaissance des recommandations de l’ISPD dans leur langue maternelle. Toute référence dans un article doit se faire au texte original en accès libre :Peritoneal Dialysis International https://doi.org/10.1177/0896860820982218 Dans les articles rédigés pour des revues françaises, conserver la référence à la version originale anglaise ci dessus, mais ajouter «version française  https://doi.org/10.25796/bdd.v4i3.62673"»TraducteursDr Christian Verger, néphrologue, président du RDPLFRDPLF, 30 rue Sere Depoin, 95300 Pontoise – FranceProfesseur Max Dratwa, néphrologueHôpital Universitaire Brugmann – Bruxelles – Belgique

ISPD recommendations for the evaluation of peritoneal membrane dysfunction in adults: Classification, measurement, interpretation and rationale for intervention

Lay summary

Peritoneal dialysis (PD) uses the peritoneal membrane for dialysis. The peritoneal membrane is a thin layer of tissue that lines the abdomen. The lining is used as a filter to help remove extra fluid and poisonous waste from the blood. Everybody is unique. What is normal for one person’s membrane may be very different from another person’s. The kidney care team wants to provide each person with the best dialysis prescription for them and to do this they must evaluate the person’s peritoneal lining. Sometimes dialysis treatment itself can cause the membrane to change after some years. This means more assessments (evaluations) will be needed to determine whether the person’s peritoneal membrane has changed. Changes in the membrane may require changes to the dialysis prescription. This is needed to achieve the best dialysis outcomes. A key tool for these assessments is the peritoneal equilibration test (PET). It is a simple, standardized and reproducible tool. This tool is used to measure the peritoneal function soon after the start of dialysis. The goal is to understand how well the peritoneal membrane works at the start of dialysis. Later on in treatment, the PET helps to monitor changes in peritoneal function. If there are changes between assessments causing problems, the PET data may explain the cause of the dysfunction. This may be used to change the dialysis prescription to achieve the best outcomes. The most common problem with the peritoneal membrane occurs when fluid is not removed as well as it should be. This happens when toxins (poisons) in the blood cross the membrane more quickly than they should. This is referred to as a fast peritoneal solute transfer rate (PSTR). Since more efficient fluid removal is associated with better outcomes, developing a personal PD prescription based on the person’s PSTR is critically important. A less common problem happens when the membrane fails to work properly (also called membrane dysfunction) because the peritoneal membrane is less efficient, either at the start of treatment or developing after some years. If membrane dysfunction gets worse over time, then this is associated with progressive damage, scarring and thickening of the membrane. This problem can be identified through another change of the PET. It is called reduced ‘sodium dip’. Membrane dysfunction of this type is more difficult to treat and has many implications for the individual. If the damage is major, the person may need to stop PD. They would need to begin haemodialysis treatment (also spelled hemodialysis). This is a very important and emotional decision for individuals with kidney failure. Any decision that involves stopping PD therapy or transitioning to haemodialysis therapy should be made jointly between the clinical team, the person on dialysis and a caregiver, if requested. Although evidence is lacking about how often tests should be performed to determine peritoneal function, it seems reasonable to repeat them whenever there is difficulty in removing the amount of fluid necessary for maintaining the health and well-being of the individual. Whether routine evaluation of membrane function is associated with better outcomes has not been studied. Further research is needed to answer this important question as national policies in many parts of the world and the COVID-19 has placed a greater emphasis and new incentives encouraging the greater adoption of home dialysis therapies, especially PD. For Chinese and Spanish Translation of the Lay Summary, see Online Supplement Appendix 1.

Key recommendations

Guideline 1:

A pathophysiological taxonomy: A pathophysiological classification of membrane dysfunction, which provides mechanistic links to functional characteristics, should be used when prescribing individualized dialysis or when planning modality transfer (e.g. to automated peritoneal dialysis (PD) or haemodialysis) in the context of shared and informed decision-making with the person on PD, taking individual circumstances and treatment goals into account. (practice point)

Guideline 2a:

Identification of fast peritoneal solute transfer rate (PSTR): It is recommended that the PSTR is determined from a 4-h peritoneal equilibration test (PET), using either 2.5%/2.27% or 4.25%/3.86% dextrose/glucose concentration and creatinine as the index solute. (practice point) This should be done early in the course dialysis treatment (between 6 weeks and 12 weeks) (GRADE 1A) and subsequently when clinically indicated. (practice point)

Guideline 2b:

Clinical implications and mitigation of fast solute transfer: A faster PSTR is associated with lower survival on PD. (GRADE 1A) This risk is in part due to the lower ultrafiltration (UF) and increased net fluid reabsorption that occurs when the PSTR is above the average value. The resulting lower net UF can be avoided by shortening glucose-based exchanges, using a polyglucose solution (icodextrin), and/or prescribing higher glucose concentrations. (GRADE 1A) Compared to glucose, use of icodextrin can translate into improved fluid status and fewer episodes of fluid overload. (GRADE 1A) Use of automated PD and icodextrin may mitigate the mortality risk associated with fast PSTR. (practice point)

Guideline 3:

Recognizing low UF capacity: This is easy to measure and a valuable screening test. Insufficient UF should be suspected when either (a) the net UF from a 4-h PET is <400 ml (3.86% glucose/4.25% dextrose) or <100 ml (2.27% glucose /2.5% dextrose), (GRADE 1B) and/or (b) the daily UF is insufficient to maintain adequate fluid status. (practice point) Besides membrane dysfunction, low UF capacity can also result from mechanical problems, leaks or increased fluid absorption across the peritoneal membrane not explained by fast PSTR.

Guideline 4a:

Diagnosing intrinsic membrane dysfunction (manifesting as low osmotic conductance to glucose) as a cause of UF insufficiency: When insufficient UF is suspected, the 4-h PET should be supplemented by measurement of the sodium dip at 1 h using a 3.86% glucose/4.25% dextrose exchange for diagnostic purposes. A sodium dip ≤5 mmol/L and/or a sodium sieving ratio ≤0.03 at 1 h indicates UF insufficiency. (GRADE 2B)

Guideline 4b:

Clinical implications of intrinsic membrane dysfunction (de novo or acquired): in the absence of residual kidney function, this is likely to necessitate the use of hypertonic glucose exchanges and possible transfer to haemodialysis. Acquired membrane injury, especially in the context of prolonged time on treatment, should prompt discussions about the risk of encapsulating peritoneal sclerosis. (practice point)

Guideline 5:

Additional membrane function tests: measures of peritoneal protein loss, intraperitoneal pressure and more complex tests that estimate osmotic conductance and ‘lymphatic’ reabsorption are not recommended for routine clinical practice but remain valuable research methods. (practice point)

Guideline 6:

Socioeconomic considerations: When resource constraints prevent the use of routine tests, consideration of membrane function should still be part of the clinical management and may be inferred from the daily UF in response to the prescription. (practice point)

Peritoneal Function and Assessment of Reference Values Using a 3.86% Glucose Solution

Background

The most widely used peritoneal function test, the peritoneal equilibration test (PET), is performed with a 2.27% glucose solution. Recently, the International Society for Peritoneal Dialysis committee on ultrafiltration failure (UFF) advised performing the test with 3.86% glucose solution because it is more sensitive for detecting clinically significant UFF. Because no reference values for this test were available, we analyzed the results of standard peritoneal permeability analyses (SPAs) using 3.86% glucose.

Methods

The tests were performed in our center on 154 clinically stable peritoneal dialysis (PD) patients that were free of peritonitis for at least 4 weeks. For the assessment of reference values, we used two approaches. In approach A, patients with UFF, defined as net ultrafiltration (UF)< 400 mL/4 hours, were excluded. In approach B, only patients within their first 2 years of PD treatment were included, regardless of net UF. Means and 95% confidence intervals (95% CI) were calculated for the transport parameters of the PET and SPA.

Results

Means of normal distribution with 95% CI in approach A were as follows: for 2.0-L exchanges, mass transfer area coefficient (MTAC) for creatinine 8.8 mL/minute (4.7 – 12.7 mL/min), dialysate/plasma ratio (D/P) creatinine 0.70 (0.52 – 0.88), glucose absorption 58% (44% – 72%), dialysate240/initial dialysate ratio of glucose (D t/D0) 0.28 (0.18 – 0.38), net UF 675 mL (375 – 975 mL), and maximal dip in D/P sodium after correction for diffusion from the circulation 0.110 (0.050 – 0.164); for 1.5-L exchanges, MTAC creatinine 7.4 mL/min (3.8 – 11.0 mL/min), D/P creatinine 0.69 (0.52 – 0.86), glucose absorption 62% (52% – 72%), D t/D0 glucose 0.25 (0.17 – 0.32), net UF 551 mL (430 – 670 mL), and maximal dip D/P sodium 0.120 (0.048 – 0.166). In approach B, most of the transport values were similar; however, values for lymphatic absorption were significantly higher [1.52 mL/min (2-L) and 1.40 mL/min (1.5-L), p < 0.01] and values for the maximum dip in D/P sodium were lower [0.101 (2-L) and 0.112 (1.5-L), p > 0.05]. This was probably the result of including patients with UFF in approach B, since these parameters can be causative factors of UFF.

Conclusions

A peritoneal transport function test using 3.86% glucose provides data on various aspects of transport. This study gives normal reference values that can be used for analysis of causes of UFF.

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.

Analysis of Ultrafiltration Failure in Peritoneal Dialysis Patients by Means of Standard Peritoneal Permeability Analysis

Background

Ultrafiltration failure (UFF) is a complication of peritoneal dialysis (PD) treatment that occurs especially in long-term patients. Etiological factors include a large effective peritoneal surface area [measured as high mass transfer area coefficient (MTAC) of creatinine], a high effective lymphatic absorption rate (ELAR), a large residual volume, or combinations.

Objective

The prevalence and etiology of UFF were studied and the contribution of transcellular water transport (TCWT) was analyzed. A new definition of UFF and guidelines for the analysis of its etiology were derived from the results.

Setting

Peritoneal dialysis unit in the Academic Medical Center in Amsterdam.

Design

Cross-sectional study of standard peritoneal permeability analyses (4-hr dwells, dextran 70 as volume marker) with 1.36% glucose in 68 PD patients. Patients with negative net UF (change in intraperitoneal volume, dlPV < 0 mL) were analyzed further using 3.86% glucose, whenever possible.

Results

Among 68 patients (duration of PD 0.3 -178 months), 39 had negative net UF with 1.36% glucose. These patients had greater MTAC creatinine and glucose absorption, and higher ELAR (p < 10–4) than the patients with positive UF. dIPV and transcapillary UF rate (TCUFR) were lower (p < 10–5). Twenty of these patients could be studied using 3.86% glucose. dlPV was greater than 400 mL/4 hr in this test in 12 patients, implying that no clinically important UFF was present. Ultrafiltration failure (dIPV < 400 mL) was found in 8 patients, giving a prevalence of 23%. This last group had been treated with PD for a longer period (p = 0.03), had higher ELAR (p = 0.07), but lower residual volume (p = 0.03), and lower TCUFR (p = 0.01). Ultrafiltration failure was associated with a high MTAC creatinine in 3 patients, a high ELAR in 4 patients, and a combination of factors in one. As an additional possible cause, TCWT was studied, using the sodium gradient in the first hour of the dwell, corrected for diffus ion (dNA). Five patients had dNA > 5 mmol/L, indicating normal TCWT. The 3 patients with dNA < 5 mmol/L tended to be treated longer (p = 0.19) and had lower TCUFR (p = 0.04). A smaller difference was found between dlPV 3.86% and 1.36% (p = 0.04) compared to the dNA > 5 mmol/L group, but no differences were present for MTAC creatinine, ELAR, residual volume, or glucose absorption.

Conclusions

ln addition to known factors, impairment of TCWT can be a cause of UFF. A standardized dwell with 1.36% glucose overestimates UFF. Therefore, 3.86% glucose should be used for identification of patients with UFF, especially because it provides additional information on TCWT. Ultrafiltration failure can be defined as net UF < 400 mL/4 hr with 3.86% glucose during a 4-hour exchange.

Correlation between Peritoneal Equilibration Test and Dialysis Adequacy and Transport Test, for Peritoneal Transport Type Characterization

Objective

The aim of this study was to analyze the correlation between the peritoneal equilibration test (PET) and the dialysis adequacy and transport test (DATT) for peritoneal transport type characterization, and the degree of patients’ acceptance for each test.

Design

Cross-sectional, observational multicenter study.

Setting

Five referral (tertiary) dialysis centers of institutional practice.

Patients

The study included 107 adult continuous ambulatory peritoneal dialysis (CAPD) patients with a prescription of four exchanges of 2 L per day, irrespective of age, gender, cause of end-stage renal disease, time on dialysis, nutritional status, or residual renal function. Patients on immunosuppressive therapy and those with cancer, hepatitis B, or HIV, and those having a peritonitis episode within the previous 30 days, or three or more episodes during the previous 12 months, were excluded.

Main Measures

Peritoneal transport type as classified by creatinine and urea dialysis-to-plasma (D/P) ratios by PET and DATT.

Results

Correlation coefficients between D/P ratios for creatinine and urea, obtained for the PET and the DATT, were 0.73 for D/P creatinine and 0.96 for D/P urea. Patients were classified into high, high-average, low-average, and low transport categories according to the mean and standard deviation of D/P creatinine values obtained from the PET at 4 hours. These values showed excellent concordance with those generated from the DATT data (κ = 0.82, 95% confidence interval 0.67 – 0.93). Nineteen percent of patients showed discordance in their category when classified according to the PET versus the DATT. Patients’ acceptance was better for the DATT than for the PET, as evaluated with a questionnaire.

Conclusion

The DATT is an easy, inexpensive, and reliable test to assess peritoneal transport type, and it also provides information about peritoneal clearance of solutes and ultrafiltration. The DATT has better patient acceptance than the PET. Since the DATT has only been validated for patients on a fixed CAPD daily schedule of 4 x 2 L, the results should be confined only to patients receiving such a prescription.

Fluid Tonicity Affects Peritoneal Characteristics Derived by 3-PORE Model

Background

It is typically assumed that within short time-frames, patient-specific peritoneal membrane characteristics are constant and do not depend on the initial fluid tonicity and dwell duration. The aim of this study was to check whether this assumption holds when membrane properties are estimated using the 3-pore model (3PM).

Methods

Thirty-two stable peritoneal dialysis (PD) patients underwent 3 8-hour peritoneal equilibration tests (PETs) with different glucose-based solutions (1.36%, 2.27%, and 3.86%). Temporary drainage was performed at 1 and 4 hours. Glucose, urea, creatinine, sodium, and phosphate concentrations were measured in dialysate and blood samples. Three-pore model parameters were estimated for each patient and each 8-hour PET separately. In addition, model parameters were estimated using data truncated to the initial 4 hours of peritoneal dwell.

Results

In all cases, model-estimated parameter values were within previously reported ranges. The peritoneal absorption (PA) and diffusive permeability for all solutes except sodium increased with fluid tonicity, with about 18% increase when switching from glucose 2.27% to 3.86%. Glucose peritoneal reflection coefficient and osmotic conductance (OsmCond), and fraction of hydraulic conductance for ultrasmall pores decreased with fluid tonicity (over 40% when switching from glucose 1.36%). Model fitting to the truncated 4-hour data resulted in little change in the parameters, except for PA, peritoneal hydraulic conductance, and OsmCond, for which higher values for the 4-hour dwell were found.

Conclusion

Initial fluid tonicity has a substantial impact on the 3PM-estimated characteristics of the peritoneal membrane, whereas the impact of dwell duration was relatively small and possibly influenced by the change in the patient's activity.

Peritoneal Equilibration Test Reference Values Using A 3.86% Glucose Solution during the First Year of Peritoneal Dialysis: Results of a Multicenter Study of a Large Patient Population

Background

The original peritoneal equilibration test (PET) was used to classify peritoneal dialysis (PD) patients using a 2.27% glucose solution. It has since been suggested that a 3.86% glucose solution be used because this provides better information about ultrafiltration (UF) capacity and the sodium (Na) sieving of the peritoneal membrane.

Objective

The aim of this study was to determine reference values for a PET using a 3.86% glucose solution (PET-3.86%).

Methods

We evaluated the PET-3.86% in a large population of incident PD patients attending 27 Italian dialysis centers.

Results

We evaluated the results of 758 PET-3.86% in 758 incident PD patients (1 test per patient). The mean duration of PD was 5 ± 3 months. The ratio of the concentrations of creatinine in dialysate/plasma (D/PCreat) was 0.73 ± 0.1 (median 0.74). The ratio between the concentrations of glucose at the end/beginning of the test (D/D0) was 0.25 ± 0.08 (median 0.24). Ultrafiltration uncorrected and corrected for bag overfill was respectively 776 ± 295 mL (median 781 mL) and 675 ± 308 mL (median 689 mL). Sodium sieving was 8.4 ± 3.8 mmol/L (median 8.0 mmol/L).

Conclusion

The results of the study provide PET-3.86% reference values for the beginning of PD that can be used to classify PD patients into transport classes and monitor them over time.

Peritoneal function in clinical practice: the importance of follow-up and its measurement in patients. Recommendations for patient information and measurement of peritoneal function

A review is given on peritoneal function, especially ultrafiltration and ultrafiltration failure followed by recommendations on how to translate pathophysiology into clinical practice. The subsequent consequences for management of peritoneal membrane function and for patient information are also included.

Simultaneous measurement of peritoneal glucose and free water osmotic conductances

Ultrafiltration (UF) failure is one of the most important causes of long-term peritoneal dialysis (PD) failure in patients. Osmotic forces acting across small and ultra-small pores generate a UF with solutes through the small pore and free water transport (FWT) through the ultra-small pore. The ability of glucose to exert an osmotic pressure sufficient to cause UF is the so-called 'osmotic conductance to glucose' (OCG) of the peritoneal membrane. Our study proposes a simple method to determine both the OCG and FWT. In 50 patients on PD, a Double Mini-Peritoneal Equilibration Test (Double Mini-PET), consisting of two Mini-PET, was performed consecutively. A solution of 1.36% glucose was used for the first test, whereas a solution of 3.86% glucose was used for the second test. The sodium removal values and the differences in UF between the two tests were used to calculate FWT and the OCG. Patients with UF failure showed significant reductions not only in the OCG and the FWT but also of UF of small pores. The Double Mini-PET is simple, fast, and could become useful to evaluate patients on PD in everyday clinical practice.

Peritoneal transport assessment by peritoneal equilibration test with 3.86% glucose: a long-term prospective evaluation

The peritoneal equilibration test (PET) with 3.86% glucose concentration (3.86%-PET) has been suggested to be more useful than the standard 2.27%-PET in peritoneal dialysis (PD), but no longitudinal data for 3.86%-PET are currently available. A total of 242 3.86%-PETs were performed in 95 incident PD patients, who underwent the first test during the first year of treatment and then once a year. The classical parameters of peritoneal transport, such as peritoneal ultrafiltration (UF), D/D(0), and D/P(Creat), were analyzed. In addition, the absolute dip of dialysate sodium concentration (DeltaD(Na)), as an expression of sodium sieving, was studied. D/D(0) was stable, and a progressive decrease in UF was observed after the second PET, whereas D/P(Creat) firstly increased and then stabilized. DeltaD(Na) was the only parameter showing a progressive decrease over time. On univariate analysis, D/D(0) and DeltaD(Na) were found to be significantly associated with the risk of developing UF failure (risk ratio (RR) 0.987 (0.973-0.999), P=0.04, and RR 0.768 (0.624-0.933), P=0.007, respectively), but on multivariate analysis only DeltaD(Na) showed an independent association with the risk of developing UF failure (RR 0.797 (0.649-0.965), P=0.020). UF, D/D(0), and D/P(Creat) changed only in those patients developing UF failure, reflecting increased membrane permeability, whereas DeltaD(Na) significantly decreased in all patients. The 3.86%-PET allows a more complete study of peritoneal membrane transport than the standard 2.27%-PET. DeltaD(Na) shows a constant and significant reduction over time and is the only factor independently predicting the risk of developing UF failure in PD patients.

Personal dialysis capacity (PDC(TM)) test: a multicentre clinical study

BACKGROUND

The assessment of the peritoneal membrane capacity and physiology of the individual patient is becoming increasingly important. It allows the prescription of an individualized peritoneal dialysis (PD)-regimen, and the monitoring of peritoneal membrane function over time. The PDC(TM) program offers the possibility to evaluate the peritoneal membrane characteristics and to predict solute and water removal by simulation of different treatment regimens.

METHODS

This study evaluates the relevance of the PDC(TM) program when routinely used. The PDC(TM) data of 336 patients from nine different centres in Europe were evaluated.

RESULTS

The area parameter was 20 985+/-7578 cm/1.73 m(2) (mean+/-SD). The reabsorption of fluid after dissipation of glucose, Jv(AR), was 1.97+/-1.00 ml/min/1.73 m(2). The large pore fluid flux, Jv(L), was 0.11+/-0.07 ml/min/1.73 m(2). A multivariate model for prediction of serum albumin included dialysate protein loss, Jv(L), Jv(AR), nPCR, A(0)/deltaX, BMI and gender (R(2)=0.81, P<0.001). Total clearance fell with increasing PD duration (P<0.001). A negative relation between A(0)/deltaX and ultrafiltration (rho=-0.26, P<0.05), a positive relation between A(0)/deltaX and peritoneal creatinine clearance (rho=0.52, P<0.05) and urea clearance (rho=0.36, P<0.05), and a positive relation between measured peritoneal creatinine and urea clearance (rho=0.64, P<0.01) was observed.

CONCLUSIONS

In summary, the present study shows that the PDC(TM) program is a robust, accurate method to describe the peritoneal membrane transport characteristics. Analysis of PDC(TM) data of large groups of patients, especially if followed up over time, can give interesting information on the physiology of the peritoneal membrane and the impact of different parameters on it.

Peritoneal dialysis in anuric patients: concerns and cautions

Most recent studies have found an equivalent survival for patients on peritoneal dialysis (PD) and hemodialysis (HD); evidence even suggests that PD might be the preferred modality during the first 3-4 years of renal replacement therapy. This is probably related to the continuous and minimally invasive character of PD as compared to HD, resulting in better preservation of residual renal function (RRF) and less cardiovascular strain. On the other hand, blood pressure control, fluid balance, and adequacy targets may be difficult to obtain in long-term PD patients. The question arises whether PD is a feasible option in anuric patients. It is clear that the answer depends on the body size and the peritoneal membrane transport characteristics of the patient, so that PD will be feasible in some anuric patients, whereas in others it will not be. Evaluation of the peritoneal transport characteristics and adaptation of the PD prescription is warranted. A constant evaluation of the fluid balance, nutritional, and cardiovascular status is needed. This article reviews the physiologic insights and clinical evidence necessary for a good PD prescription in anuric patients.

Prevention and treatment of peritoneal dialysis membrane failure

A review is given on the definition of peritoneal membrane failure, its pathogenesis, mechanisms of impaired ultrafiltration, and prevention and treatment of membrane failure. In the absence of clinical signs of peritoneal sclerosis and of nonresolving peritonitis, membrane failure is best defined as net ultrafiltration of less than 400 mL/4 hours on a 3.86% glucose-based dialysis solution. Evidence has been accumulating that glucose is a major pathogenetic factor. Reduced exposure to glucose is the most important preventive measurement. Strategies for treatment are discussed. The use of icodextrin-based dialysis solutions is an attractive possibility to reduce glucose exposure.

The standard peritoneal permeability analysis: a tool for the assessment of peritoneal permeability characteristics in CAPD patients

Peritoneal transport characteristics in CAPD patients are often assessed by the peritoneal equilibration test (PET), which uses a four hour dwell with glucose 2.27% dialysate. From the test, the dialysate/plasma ratio of creatinine (D/PCr), the dialysate/initial dialysate ratio of glucose (D/Do) and net ultrafiltration (NUF, drained minus instilled volume) are calculated. The standard peritoneal permeability analysis (SPA) is a modification and extension of the PET: glucose 1.36% dialysate is used, to which dextran 70 (1 g/liter) is added for the calculation of fluid kinetics. Mass transfer area coefficients (MTAC's) of low molecular weight solutes, clearances of proteins and the change in intraperitoneal volume (delta IPV) can be assessed. In this study the SPA was analyzed, and a comparison with the PET was made. A total number of 138 SPA's was analyzed in 86 different clinically stable patients. Normal values were calculated for both SPA and PET parameters in the same tests. Median (ranges) of comparable transport parameters from SPA and PET were: MTACCr, 10.4 ml/min (5.7 to 19.3); glucose absorption, 61% (35 to 87); delta IPV, 9.5 ml (-761 to 310); D/PCr, 0.76 (0.53 to 1.14); D/D0, 0.37 (0.13 to 0.56); NUF, -75 ml (-675 to 450). The agreement between SPA and PET was analyzed using the method of Bland and Altman. A fairly good agreement was present between NUF and delta IPV. Systematic errors were found when D/PCr and MTACCr were compared: D/P overestimated MTAC mainly in the low range, whereas in the high range values were underestimated. A similar pattern was seen for the transport parameters of glucose. In 40 patients negative net ultrafiltration was present, and possible reasons for this were assessed. In 9 patients no reason could be identified. It can be concluded that the SPA provides useful and extensive information on peritoneal transport parameters. Compared to the PET, the SPA has better discriminative power for the transport of glucose and creatinine.

Evaluation of peritoneal membrane permeability

Total removal of fluid and solutes during peritoneal dialysis depends on both the dialysis prescription (ie, the number, length, and timing of the dwells and the volume and contents of the dialysis solution) and the permeability of the peritoneal membrane. Peritoneal membrane permeability determines the rate of solute equilibration between body fluids and the solution within the peritoneal cavity and is, therefore, a significant determinant of the solute removal rate. The relationship between fluid removal during peritoneal dialysis and the properties of the peritoneal membrane is more complex; peritoneal ultrafiltration is inversely related to the permeability of the peritoneal membrane to osmotic solutes but is directly related to the hydraulic conductivity of the peritoneal membrane. The peritoneal equilibration test (PET) is widely used as the standard method for evaluating peritoneal membrane permeability, and results from the PET can be used to determine the type of peritoneal dialysis therapy optimal for the permeability characteristics of the patient's peritoneal membrane. Simple extrapolations from the PET can only provide qualitative estimates of the dialysis dose required for various types of peritoneal dialysis. More accurate estimates of the required dialysis dose can be provided by mathematical models of peritoneal fluid and solute transport, but these models require calculation of the permeability-area product or mass transfer-area coefficient of the peritoneal membrane. Although the latter approach shows promise for improving peritoneal dialysis prescriptions, determination of the delivered dose of peritoneal dialysis can, at present, only be assessed by directly measuring total 24-hour solute and fluid removal.