Baseline hydration status in incident peritoneal dialysis patients: the initiative of patient outcomes in dialysis (IPOD-PD study)†

Transition between peritoneal dialysis modalities: Impact on blood pressure levels and drug prescription in a national multicentric cohort

BACKGROUND

Hypertension is a leading cause of kidney failure, affects most dialysis patients and associates with adverse outcomes. Hypertension can be difficult to control with dialysis modalities having differential effects on sodium and water removal. There are two main types of peritoneal dialysis (PD), automated peritoneal dialysis (APD) and continuous ambulatory peritoneal dialysis (CAPD). It is unknown whether one is superior to the other in controlling blood pressure (BP). Therefore, the aim of our study was to analyse the impact of switching between these two PD modalities on BP levels in a nationally representative cohort.

METHODS

This was a cohort study of patients on PD from 122 dialysis centres in Brazil (BRAZPD II study). Clinical and laboratory data were collected monthly throughout the study duration. We selected all patients who remained on PD at least 6 months and 3 months on each modality at minimum. We compared the changes in mean systolic/diastolic blood pressures (SBP/DBP) before and after modality transition using a multilevel mixed-model where patients were at first level and their clinics at the second level.

RESULTS

We analysed data of 848 patients (814 starting on CAPD and 34 starting on APD). The SBP decreased by 4 (SD 22) mmHg when transitioning from CAPD to APD (p < 0.001) and increased by 4 (SD 21) mmHg when transitioning from APD to CAPD (p = 0.38); consistent findings were seen for DBP. There was no significant change in the number of antihypertensive drugs prescribed before and after transition.

CONCLUSIONS

Transition between PD modalities seems to directly impact on BP levels. Further studies are needed to confirm if switching to APD could be an effective treatment for uncontrolled hypertension among CAPD patients.

Why should we use a low sodium dialysis solution for peritoneal dialysis?

Overhydration is highly prevalent in patients on peritoneal dialysis (PD), with inappropriately high sodium load supposedly playing a central role in the pathophysiology of the conditions. Recent studies have revealed the novel role of the interstitium as a buffer system for sodium ions, and it has been reported that patients on dialysis, including PD, present increased levels of sodium in the interstitium, such as in subcutaneous tissue and muscle. Hence, therapy for correction of overhydration should target the excess extracellular volume and the excess sodium storage in the interstitium. The ultrafiltrate obtained using the currently available PD solutions is hypo- to isonatric as compared to serum, which is disadvantageous for prompt and efficient sodium removal from the body in patients with overhydration. In contrast, use of low sodium PD solutions is characterised by iso- to hypernatric ultrafiltrate, which may beneficial for reducing sodium storage in the interstitium. Trials of low sodium PD solutions have reported possible clinical merits, for example, decreased blood pressure, reduced dryness of mouth and decreased body water content as assessed using bioimpedance methods. Given these observations and the high prevalence of overhydration in current PD populations, it makes medical sense that low sodium solutions be positioned as the new standard solution in the future. However, for medical safety, that is, to avoid hyponatremia and excessive decreases in blood pressure, further studies are needed to establish the appropriate compositions and applications of low sodium solutions.

Effects of Steady Glucose Concentration Peritoneal Dialysis on Ultrafiltration Volume and Sodium Removal: A Pilot Crossover Trial

BACKGROUND

Volume overload is common in patients treated with peritoneal dialysis (PD) and is associated with poor clinical outcome. Steady concentration PD is where a continuous glucose infusion maintains the intraperitoneal glucose concentration and as a result provides continuous ultrafiltration throughout the dwell. The primary objective of this study was to investigate the ultrafiltration rate and glucose ultrafiltration efficiency for steady concentration PD in comparison with a standard continuous ambulatory PD (CAPD) dwell, using the novel Carry Life UF device.

METHODS

Eight stable patients treated with PD (six fast and two fast average transporters) were investigated four times: a standard 4-hour CAPD dwell with 2 L of 2.5% dextrose solution as control and three 5-hour steady concentration PD treatments (glucose dose 11, 14, 20 g/h, initial fill 1.5 L of 1.5% dextrose solution). All investigations were preceded by an overnight 2 L 7.5% icodextrin dwell.

RESULTS

Intraperitoneal glucose concentration increased during the first 1-2 hours of the steady concentration PD treatments and remained stable thereafter. Ultrafiltration rates were significantly higher with steady concentration PD treatments (124±49, 146±63, and 168±78 mL/h with 11, 14, and 20 g/h, respectively, versus 40±60 mL/h with the control dwell). Sodium removal and glucose ultrafiltration efficiency (ultrafiltration volume/gram glucose uptake) were significantly higher with steady concentration PD treatments versus the control dwell, where the 11 g/h glucose dose was most efficient.

CONCLUSIONS

Steady concentration PD performed with the Carry Life UF device resulted in higher ultrafiltration rates, more efficient use of glucose (increased ultrafiltration volume/gram glucose absorbed), and greater sodium removal compared with a standard 2.5% dextrose CAPD dwell.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

A Performance Analysis of the Peritoneal Ultrafiltration (PUF) Achieved With the Carry Life ® UF, NCT03724682 .

Diagnosis and treatment of hypertension in dialysis patients: a systematic review

In patients with end-stage renal disease (ESRD) undergoing dialysis, hypertension is common but often inadequately controlled. The prevalence of hypertension varies widely among studies because of differences in the definition of hypertension and the methods of used to measure blood pressure (BP), i.e., peri-dialysis or ambulatory BP monitoring (ABPM). Recently, ABPM has become the gold standard for diagnosing hypertension in dialysis patients. Home BP monitoring can also be a good alternative to ABPM, emphasizing BP measurement outside the hemodialysis (HD) unit. One thing for sure is pre- and post-dialysis BP measurements should not be used alone to diagnose and manage hypertension in dialysis patients. The exact target of BP and the relationship between BP and all-cause mortality or cause-specific mortality are unclear in this population. Many observational studies with HD cohorts have almost universally reported a U-shaped or even an L-shaped association between BP and all-cause mortality, but most of these data are based on the BP measured in HD units. Some data with ABPM have shown a linear association between BP and mortality even in HD patients, similar to the general population. Supporting this, the results of meta-analysis have shown a clear benefit of BP reduction in HD patients. Therefore, further research is needed to determine the optimal target BP in the dialysis population, and for now, an individualized approach is appropriate, with particular emphasis on avoiding excessively low BP. Maintaining euvolemia is of paramount importance for BP control in dialysis patients. Patient heterogeneity and the lack of comparative evidence preclude the recommendation of one class of medication over another for all patients. Recently, however, β-blockers could be considered as a first-line therapy in dialysis patients, as they can reduce sympathetic overactivity and left ventricular hypertrophy, which contribute to the high incidence of arrhythmias and sudden cardiac death. Several studies with mineralocorticoid receptor antagonists have also reported promising results in reducing mortality in dialysis patients. However, safety issues such as hyperkalemia or hypotension should be further evaluated before their use.

Systolic Blood Pressure and the Risk of Kidney Replacement Therapy and Mortality in Patients with Chronic Kidney Disease Stages 4-5

INTRODUCTION

In patients with chronic kidney disease stages 4 and 5 (CKD stages 4-5) without dialysis and arterial hypertension, it is unknown if the values of systolic blood pressure (SBP) considered in control (<120 mm Hg) are associated with kidney replacement therapy (KRT) and mortality.

METHODS

In this retrospective cohort study, hypertensive CKD stages 4-5 patients attending the Renal Health Clinic at the Hospital Civil de Guadalajara were enrolled. We divided them into those that achieved SBP <120 mm Hg (controlled group) and those who did not (>120 mm Hg), the uncontrolled group. Our primary objective was to analyze the association between the controlled group and KRT; the secondary objective was the mortality risk and if there were subgroups of patients that achieved more benefit. Data were analyzed using Stata software, version 15.1.

RESULTS

During 2017-2022, a total of 275 hypertensive CKD stages 4-5 patients met the inclusion criteria for the analysis: 62 in the controlled group and 213 in the uncontrolled group; mean age 61 years; 49.82% were male; SBP was significantly lower in the controlled group (111 mm Hg) compared to the uncontrolled group (140 mm Hg); eGFR was similar between groups (20.41 mL/min/1.73 m2). There was a tendency to increase the mortality risk in the uncontrolled group (HR 6.47 [0.78-53.27]; p = 0.082) and an association by the Kaplan-Meir analysis (Log-rank p = 0.043). The subgroup analysis for risk of KRT in the controlled group revealed that patients ≥61 years had a lower risk of KRT (HR 0.87 [95% CI, 0-76-0.99]; p = 0.03, p of interaction = 0.005), but no differences were found in the subgroup analysis for mortality. In a follow-up of 1.34 years, no association was found in the risk of KRT according to the controlled or uncontrolled groups in a multivariate Cox analysis.

CONCLUSION

In a retrospective cohort of patients with CKD stages 4-5 and hypertension, SBP >120 mm Hg was not associated with risk of KRT but could be associated with the risk of death. Clinical trials are required in this group of patients to demonstrate the impact of reaching the SBP goals recommended by the KDIGO guidelines.

Comparing Left Ventricular Diastolic Function between Peritoneal Dialysis and Non-Dialysis Patients with Stage 5 Chronic Kidney Disease: A Propensity Score-Matched Analysis

Patients with chronic kidney disease (CKD) have a high incidence of left ventricular diastolic dysfunction (LVDD), which increases the risk of heart failure and mortality. We assessed fluid overload as an independent risk factor for LVDD in patients with decreased kidney function and compared its impact on the E/e' ratio as a parameter for assessing left ventricular diastolic functions between patients undergoing continuous ambulatory peritoneal dialysis (CAPD) and those with non-dialysis CKD stage 5 (CKD5) using propensity score matching (PSM). After PSM, 222 patients (CAPD, n = 111; CKD5, n = 111) were included. Fluid balance was assessed using bio-impedance spectroscopy and LVDD was determined by echocardiography based on an E/e' ratio of >15. The CKD5 group had a significantly higher E/e' ratio (p = 0.002), while fluid overload (OH/ECW) did not differ significantly between the groups. In the CAPD group, there were no significant differences in OH/ECW between patients with and without LVDD (p = 0.517). However, in the CKD5 group, patients with LVDD showed a significantly higher OH/ECW (p = 0.001). In a regression analysis investigating factors associated with the E/e' ratio, OH/ECW was not significantly associated with the E/e' ratio in the CAPD group (p = 0.087), but in the CKD5 group, it was independently correlated (p = 0.047). The factors closely associated with LVDD varied depending on dialysis dependence. While fluid overload independently influenced LVDD in non-dialysis patients, it was not statistically significant in patients with CAPD. Early assessment and management of volume status are crucial in addressing LVDD in patients with advanced-stage CKD.

From MIA to FIFA: The vicious matrix of frailty, inflammation, fluid overload and atherosclerosis in peritoneal dialysis

Cardiovascular disease (CVD) is a major cause of mortality and morbidity in peritoneal dialysis (PD) patients. Two decades ago, the common co-existence of malnutrition and systemic inflammation PD patients with atherosclerosis and CVD led to the proposed terminology of 'malnutrition-inflammation-atherosclerosis (MIA) syndrome'. Although the importance of malnutrition is well accepted, frailty represents a more comprehensive assessment of the physical and functional capability of the patient and encompasses the contributions of sarcopenia (a key component of malnutrition), obesity, cardiopulmonary as well as neuropsychiatric impairment. In recent years, it is also increasingly recognized that fluid overload is not only the consequence but also play an important role in the pathogenesis of CVD. Moreover, fluid overload is closely linked with the systemic inflammatory status, presumably by gut oedema, gastrointestinal epithelial barrier dysfunction and leakage of bacterial fragments to the systemic circulation. There are now a wealth of published evidence to show intricate relations between frailty, inflammation, fluid overload and atherosclerotic disease in patients with chronic kidney disease (CKD) and those on PD, a phenomenon that we propose the term 'FIFA complex'. In this system, frailty and atherosclerotic disease may be regarded as two patient-oriented outcomes, while inflammation and fluid overload are two inter-connected pathogenic processes. However, there remain limited data on how the treatment of one component affect the others. It is also important to define how treatment of fluid overload affect the systemic inflammatory status and to develop effective anti-inflammatory strategies that could alleviate atherosclerotic disease and frailty.

Associations among body composition parameters and quality of life in peritoneal dialysis patients

Health-related quality of life (HRQOL) is an important issue among patients undergoing dialysis treatment. Peritoneal dialysis (PD) is associated with a number of adverse body composition changes. However, whether body composition is associated with HRQOL is uncertain. The purpose of this study was to analyze the effects of body composition on HRQOL in PD patients. We performed a cross-sectional observational study on the association between body composition and HRQOL in PD patients at a single center. Body composition was determined by multifrequency bioimpedance spectroscopy. HRQOL is summarized to three composite scores: kidney disease component summary (KDCS), physical component summary (PCS), and mental component summary (MCS). The relationships between HRQOL and the hydration index, lean tissue index (LTI), and fat tissue index (FTI) were analyzed by regression analysis. One hundred and ninety-seven PD patients were included in the present study. Patients with severe fluid overload showed a lower PCS. The hydration index and FTI showed statistically significant negative associations with PCS. In subgroup analysis, the associations between the hydration index and PCS remained robust after stratifying according to sex, age, and residual urine. Our results indicated that both the hydration index and FTI were negatively associated with HRQOL, especially PCS.

Obesity, Weight Gain, and Fluid Overload in Peritoneal Dialysis

Obesity is a global epidemic that has a complicated pathogenesis as well as impact on the outcome of peritoneal dialysis (PD) patients. In this review, the prevalence of obesity in incident PD patients as well as the phenomenon of new-onset glucose intolerance after PD will be reviewed. Published literature on the effect of obesity on the survival and incidence of cardiovascular disease in PD patients will be discussed. Particular emphasis would be put on literature that compared the impact of obesity on the outcome of hemodialysis and PD, and the confounding effect of dialysis adequacy. Next, the complex concept of obesity and its relevance for PD will be explored. The focus would be put on the methods of assessment and clinical relevance of central versus general obesity, as well as visceral versus subcutaneous adipose tissue. The relation between obesity and systemic inflammation, as well as the biological role of several selected adipokines will be reviewed. The confounding effects of metabolic syndrome and insulin resistance will be discussed, followed by the prevalence and prognostic impact of weight gain during the first few years of PD. The differences between weight gain due to fluid overload and accumulation of adipose tissue will be discussed, followed by the current literature on the change in body composition after patients are put on chronic PD. The methods of body composition will be reviewed, and the clinical relevance of individual body component (fluid, fat, muscle, and bone) will be discussed. The review will conclude by highlighting current gaps of knowledge and further research directions in this area.

The association between office blood pressure and fluid status using bioimpedance spectroscopy in stable continuous ambulatory peritoneal dialysis patients

Background

Hypertension is common in continuous ambulatory peritoneal dialysis (CAPD) patients. It remains to be determined the extent to which fluid overload contributes to uncontrolled blood pressure (BP) in this population. The aim was to determine the association between fluid status as measured using bioimpedance spectroscopy (BIS) and BP in CAPD patients.

Methods

A cross-sectional study was performed involving 50 stable CAPD patients at a single center in Cape Town, South Africa. All participants were known to have hypertension and were divided into two groups based on office BP measurements: an uncontrolled BP group (systolic BP ≥ 140 mmHg or diastolic BP ≥ 90 mmHg) and a controlled BP group. Fluid status was determined using BIS (Body Composition Monitor®, Fresenius Medical Care, Bad Homburg, Germany).

Results

There was a statistically significant difference in overhydration (OH) between the uncontrolled BP group and the controlled BP group (3.0 ± 2.3 L vs. 1.4 ± 1.6 L, respectively, P = 0.01). The uncontrolled BP group was older (37.7 ± 9.5 years vs. 32.0 ± 8.0 years, P = 0.04) and had a shorter dialysis vintage (15 [IQR, 7–22] months vs. 31 [IQR, 12–39] months, P = 0.02). Significant correlations were found between OH and the extracellular water (ECW) (r = 0.557, P < 0.01) and ECW to total body water (TBW) ratio (r = 0.474, P < 0.01). Mixed ancestry, presence of residual kidney function, ECW, and ECW to TBW ratio were identified as predictors of OH on multivariable linear regression.

Conclusions

We found that stable CAPD patients with uncontrolled BP had higher OH compared to patients whose BP was controlled.

The relationship between apelin and carotid intima media thickness, and the presence of plaque in dialysis patients

BACKGROUND

Apelin is a peptide that has important effects on the cardiovascular system due to its anti-atherogenic properties and regulating blood pressure. There is not enough research evaluating the effects of apelin levels on the cardiovascular system in hemodialysis (HD) and peritoneal dialysis (PD) patients concurrently. The aim of this study was to determine apelin levels in dialysis, and control groups and to investigate the relationship between apelin and carotid intima media thickness (CIMT).

MATERIALS AND METHODS

Thirty three HD patients, 35 PD patients, and 15 healthy individuals were included in the study. All laboratory data, N-terminal pro-B-type natriuretic peptide (NT-proBNP), IL-6, and apelin-13 levels were analyzed. To prevent interobserver errors in CIMT measurement, the analyses were performed by a single radiologist.

RESULT

CIMT, presence of plaque, apelin, NT-proBNP, IL-6, and C-reactive protein (CRP) levels were higher in dialysis patients. There was a relationship between apelin and CIMT, and between apelin and high-density lipoprotein (HDL) in PD patients. Age, apelin, HDL, parathormone (PTH), glucose, and smoking were found to affect the presence of plaque in dialysis patients.

CONCLUSION

Apelin levels were high in dialysis patients. Especially in PD patients, there was a negative correlation between apelin and CIMT, and between apelin and HDL. Therefore, apelin may play a role in the pathogenesis of cardiovascular diseases in PD patients.

Association of Prescription With Body Composition and Patient Outcomes in Incident Peritoneal Dialysis Patients

Objective: The nutritional status of patients on peritoneal dialysis (PD) is influenced by patient- and disease-related factors and lifestyle. This analysis evaluated the association of PD prescription with body composition and patient outcomes in the prospective incident Initiative for Patient Outcomes in Dialysis–Peritoneal Dialysis (IPOD-PD) patient cohort.

Design and Methods: In this observational, international cohort study with longitudinal follow-up of 1,054 incident PD patients, the association of PD prescription with body composition was analyzed by using the linear mixed models, and the association of body composition with death and change to hemodialysis (HD) by means of a competing risk analysis combined with a spline analysis. Body composition was regularly assessed with the body composition monitor, a device applying bioimpedance spectroscopy.

Results: Age, time on PD, and the use of hypertonic and polyglucose solutions were significantly associated with a decrease in lean tissue index (LTI) and an increase in fat tissue index (FTI) over time. Competing risk analysis revealed a U-shaped association of body mass index (BMI) with the subdistributional hazard ratio (HR) for risk of death. High LTI was associated with a lower subdistributional HR, whereas low LTI was associated with an increased subdistributional HR when compared with the median LTI as a reference. High FTI was associated with a higher subdistributional HR when compared with the median as a reference. Subdistributional HR for risk of change to HD was not associated with any of the body composition parameters. The use of polyglucose or hypertonic PD solutions was predictive of an increased probability of change to HD, and the use of biocompatible solutions was predictive of a decreased probability of change to HD.

Conclusion: Body composition is associated with non-modifiable patient-specific and modifiable treatment-related factors. The association between lean tissue and fat tissue mass and death and change to HD in patients on PD suggests developing interventions and patient counseling to improve nutritional markers and, ultimately, patient outcomes.

Study Registration: The study has been registered at Clinicaltrials.gov (NCT01285726).

Volume-Independent Sodium Toxicity in Peritoneal Dialysis: New Insights from Bench to Bed

Sodium overload is common in end-stage kidney disease (ESKD) and is associated with increased cardiovascular mortality that is traditionally considered a result of extracellular volume expansion. Recently, sodium storage was detected by Na23 magnetic resonance imaging in the interstitial tissue of the skin and other tissues. This amount of sodium is osmotically active, regulated by immune cells and the lymphatic system, escapes renal control, and, more importantly, is associated with salt-sensitive hypertension. In chronic kidney disease, the interstitial sodium storage increases as the glomerular filtration rate declines and is related to cardiovascular damage, regardless of the fluid overload. This sodium accumulation in the interstitial tissues becomes more significant in ESKD, especially in older and African American patients. The possible negative effects of interstitial sodium are still under study, though a higher sodium intake might induce abnormal structural and functional changes in the peritoneal wall. Interestingly, sodium stored in the interstial tissue is not unmodifiable, since it is removable by dialysis. Nevertheless, the sodium removal by peritoneal dialysis (PD) remains challenging, and new PD solutions are desirable. In this narrative review, we carried out an update on the pathophysiological mechanisms of volume-independent sodium toxicity and possible future strategies to improve sodium removal by PD.

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

Effect of bioimpedance-defined overhydration parameters on mortality and cardiovascular events in patients undergoing dialysis: a systematic review and meta-analysis

OBJECTIVE

To evaluate the role of bioimpedance-defined overhydration (BI-OH) parameters in predicting the risk of mortality and cardiovascular (CV) events in patients undergoing dialysis.

METHODS

We searched multiple electronic databases for studies investigating BI-OH indicators in the prediction of mortality and CV events through 23 May 2020. We assessed the effect of BI-OH indexes using unadjusted hazard ratios (HRs) and 95% confidence intervals (CIs). Sensitivity analysis was used for each outcome.

RESULTS

We included 55 studies with 104,758 patients in the meta-analysis. Extracellular water/total body water (ECW/TBW) >0.4 (HR 5.912, 95% CI: 2.016-17.342), ECW/intracellular water (ICW) for every 0.01 increase (HR 1.041, 95% CI: 1.031-1.051), and OH/ECW >15% (HR 2.722, 95% CI: 2.005-3.439) increased the risk of mortality in patients receiving dialysis. ECW/TBW >0.4 (HR 2.679, 95% CI: 1.345-5.339) and ECW/ICW per increment of 10% (HR 1.032, 95% CI: 1.017-1.047) were associated with an increased risk of CV events in patients undergoing dialysis. A 1-degree increase in phase angle was a protective factor for both mortality (HR 0.676, 95% CI: 0.474-0.879) and CV events (HR 0.736, 95% CI: 0.589-0.920).

CONCLUSIONS

BI-OH parameters might be independent predictors for mortality and CV events in patients undergoing dialysis.

Relationship between sodium removal, hydration and outcomes in peritoneal dialysis patients

BACKGROUND

Fluid overload (FO) in peritoneal dialysis (PD) patients is associated with mortality. We explore if low daily sodium removal is an independent risk factor for mortality. We examined severely FO PD patients established for >1 year in expectation that PD prescription would have been optimized for solute clearance and ultrafiltration. We also wish to determine the relationship between kt/v and sodium removal.

METHODS

Retrospective analysis of 231 PD patients with FO ≥2.0 L and compared with 218 PD patients who were euvolaemic throughout their PD treatment. Patients were followed up until death censored for transplantation.

RESULTS

Mean daily sodium removal in overhydrated patients was only 75 mmoles (=1.7 g). CAPD usage was more common in patients with the highest sodium removal. Achievement of UK guidelines for solute clearance and daily fluid removal were not independent predictors of mortality. Markers of sarcopenia (low serum albumin and high CRP) were associated with increased mortality, but these parameters were not independent predictors in a model that included functional assessment (Karnofsky score). Daily sodium removal was not predictive of mortality but the imprecision of clinically used sodium assay should be noted. The correlation between Na and kt/v is statistically significant but R² was weak at .07.

CONCLUSION

While diabetic males were more likely to become overhydrated, these factors did not increase mortality further. Traditional targets of 'dialysis adequacy' did not predict survival. Kt/v is not a good indicator of sodium removal which can be surprisingly low. Measuring sodium clearance may help clinicians optimize PD modality (CAPD vs. APD).

Body Composition Changes Following Dialysis Initiation and Cardiovascular and Mortality Outcomes in CRIC (Chronic Renal Insufficiency Cohort): A Bioimpedance Analysis Substudy

Rationale & Objective

Bioelectrical impedance analysis (BIA) provides a noninvasive assessment of body composition. BIA measures of nutritional (phase angle) and hydration (vector length) status are associated with survival among individuals with chronic kidney disease (CKD), including those receiving maintenance dialysis. However, little is known regarding changes in these parameters with CKD following the high-risk transition to maintenance dialysis.

Study Design

Observational study.

Settings & Participants

427 adults enrolled in the Chronic Renal Insufficiency Cohort (CRIC) Study, with BIA measurements performed within 1 year before and after initiation of maintenance dialysis.

Exposures

We calculated the changes in vector length and phase angle for patients with CKD transitioning to maintenance dialysis.

Outcomes

We examined the association of changes in vector length and phase angle during the transition to maintenance dialysis with risk for all-cause mortality or nonfatal myocardial infarction, stroke, or heart failure, adjusting for demographics, comorbid conditions, and nutritional parameters.

Results

Mean age was 58 ± 12 years and mean estimated glomerular filtration rate using the CKD Epidemiology Collaboration equation before dialysis initiation was 17.0 ± 8.7 mL/min/1.73 m². After covariate adjustment, mean changes in vector length and phase angle were 18 (95% CI, 7 to 30) Ω/m and -0.6  (95% CI, -1.3  to 0.1 ), respectively. Changes in both BIA parameters were not associated with risk for heart failure, stroke, myocardial infarction, or all-cause mortality: HR, 1.02 (95% CI, 0.91-1.14) per 1-SD increment in change for vector length and HR, 1.11 (95% CI, 0.88-1.41) per 1-SD increment in change for phase angle.

Limitations

Observational study, relatively small sample size.

Conclusions

In a multicenter cohort of patients with CKD who progressed to kidney failure, the transition to maintenance dialysis was associated with changes in body composition reflecting poorer cellular integrity and improved volume control. However, these longitudinal changes were not associated with adverse clinical events after dialysis initiation.

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)

Novel Method for Osmotic Conductance to Glucose in Peritoneal Dialysis

Introduction

The osmotic conductance to glucose (OCG) is a crucial determinant of ultrafiltration (UF) in peritoneal dialysis (PD) patients and can be used to monitor membrane integrity in patients on long-term PD. It has been proposed that OCG can be assessed based on drained volumes in 2 consecutive 1-hour glucose dwells, usually 1.5% and 4.25% glucose, in a so-called double mini-peritoneal equilibration test (dm-PET). However, recent data indicated that the dm-PET provides a poor estimate of OCG unless the residual volume (RV) is taken into account. We introduce an easy, robust, and accurate method to measure OCG and compare it with conventional methods.

Methods

In a prospective cohort of 21 PD patients, a modified version of the dm-PET was performed, along with the determination of RV before, between, and after dwells. Based on computer simulations derived from the 3-pore model (TPM) for membrane permeability, we developed and validated a novel single-dwell method to estimate OCG. We next validated the equation in an independent cohort consisting of 32 PD patients.

Results

Single-dwell OCG correlated more closely with actual UF (r = 0.94 vs. r = 0.07 for conventional dm-PET), sodium sieving, and free water transport (FWT) compared with other methods. These findings were replicated in the validation cohort in which OCG calculated using the single-dwell method closely correlated with parameters of osmotic water transport, even when RV was not taken into account, using only drained volumes.

Conclusion

We propose a novel, easy, and robust single-dwell method to determine OCG in individual patients and to monitor membrane integrity over time on PD.

Bioimpedance Analysis–Guided Volume Expansion for the Prevention of Contrast-Induced Acute Kidney Injury (the BELIEVE Pilot Randomized Controlled Trial)

Introduction

Peri-procedural i.v. fluid administration is important for the prevention of contrast-induced acute kidney injury (CI-AKI). However, standardized fluid management protocols may not be suitable for all patients. We therefore wished to determine whether an individualized fluid administration protocol guided by measuring extracellular water (ECW) using bioimpedance analysis (BIA) would be safe and would reduce the incidence CI-AKI compared to a standardized fluid administration prescription.

Methods

In this pilot, randomized, parallel-group, single-blind, controlled trial, we compared the effect of BIA-guided isotonic bicarbonate administration according to the ratio of ECW to total body water (ECW/TBW) to our standard isotonic bicarbonate protocol in regard to the safety and efficacy of preventing CI-AKI in chronic kidney disease patients undergoing elective cardiac angiography. Our primary outcome was the incidence of CI-AKI, which was defined as a ≥0.3 mg/dl or 150% increase in serum creatinine concentration within 48 to 72 hours after cardiac angiography.

Results

We studied 61 patients, 30 in the bioimpedance group and 31 in the control group. Age was similar (72.5 ± 7 vs. 71.4 ± 7.9 years), as were body mass index (25.5 vs. 25.8 kg/m²) and baseline serum creatinine (1.3 ± 0.3 vs. 1.4 ± 0.4 mg/dl). The peri-procedural fluid volume administered was significantly greater in the BIA-guided hydration group (899.0 ± 252.7 ml vs. 594.4 ± 125.9 ml, P < .01). The incidence of CI-AKI was 3.3% in BIA-guided hydration group and 6.5% in the control group (relative risk = 0.52, 95% confidence interval = 0.05−5.40, P = 1.00). Adverse events reported were comparable between groups (6.7% vs. 6.5%, P = 1.00).

Conclusions

The overall incidence of CI-AKI after cardiac angiography in our patients with mild-to-moderate renal insufficiency was lower than anticipated. Isotonic bicarbonate administration guided by bioimpedance measurements was safe, and probably led to a lower incidence of CI-AKI, although this not reach statistical significance.

Assessment of Hydration Status in Peritoneal Dialysis Patients: Validity, Prognostic Value, Strengths, and Limitations of Available Techniques

BACKGROUND

The majority of patients undergoing peritoneal dialysis (PD) suffer from volume overload and this overhydration is associated with increased mortality. Thus, optimal assessment of volume status in PD is an issue of paramount importance. Patient symptoms and physical signs are often unreliable indexes of true hydration status.

SUMMARY

Over the past decades, a quest for a valid, reproducible, and easily applicable technique to assess hydration status is taking place. Among existing techniques, inferior vena cava diameter measurements with echocardiography and natriuretic peptides such as brain natriuretic peptide and N-terminal pro-B-type natriuretic peptide were not extensively examined in PD populations; while having certain advantages, their interpretation are complicated by the underlying cardiac status and are not widely available. Bioelectrical impedance analysis (BIA) techniques are the most studied tool assessing volume overload in PD. Volume overload assessed with BIA has been associated with technique failure and increased mortality in observational studies, but the results of randomized trials on the value of BIA-based strategies to improve volume-related outcomes are contradictory. Lung ultrasound (US) is a recent technique with the ability to identify volume excess in the critical lung area. Preliminary evidence in PD showed that B-lines from lung US correlate with echocardiographic parameters but not with BIA measurements. This review presents the methods currently used to assess fluid status in PD patients and discusses existing data on their validity, applicability, limitations, and associations with intermediate and hard outcomes in this population. Key Message: No method has proved its value as an intervening tool affecting cardiovascular events, technique, and overall survival in PD patients. As BIA and lung US estimate fluid overload in different compartments of the body, they can be complementary tools for volume status assessment.

Sodium Intake and Chronic Kidney Disease

In Chronic Kidney Disease (CKD) patients, elevated blood pressure (BP) is a frequent finding and is traditionally considered a direct consequence of their sodium sensitivity. Indeed, sodium and fluid retention, causing hypervolemia, leads to the development of hypertension in CKD. On the other hand, in non-dialysis CKD patients, salt restriction reduces BP levels and enhances anti-proteinuric effect of renin-angiotensin-aldosterone system inhibitors in non-dialysis CKD patients. However, studies on the long-term effect of low salt diet (LSD) on cardio-renal prognosis showed controversial findings. The negative results might be the consequence of measurement bias (spot urine and/or single measurement), reverse epidemiology, as well as poor adherence to diet. In end-stage kidney disease (ESKD), dialysis remains the only effective means to remove dietary sodium intake. The mismatch between intake and removal of sodium leads to fluid overload, hypertension and left ventricular hypertrophy, therefore worsening the prognosis of ESKD patients. This imposes the implementation of a LSD in these patients, irrespective of the lack of trials proving the efficacy of this measure in these patients. LSD is, therefore, a rational and basic tool to correct fluid overload and hypertension in all CKD stages. The implementation of LSD should be personalized, similarly to diuretic treatment, keeping into account the volume status and true burden of hypertension evaluated by ambulatory BP monitoring.

Determinants of volume status in peritoneal dialysis: A longitudinal study

AIM

In peritoneal dialysis (PD), fluid overload is frequent and associated with cardiac dysfunction and mortality. As it is considered a modifiable risk factor, we wished to describe clinical determinants of fluid overload in a longitudinal cohort of PD outpatients.

METHODS

We consecutively included PD outpatients treated with continuous ambulatory PD (CAPD) or automated PD (APD) attending for their routine clinical visit at a single tertiary hospital. Extracellular water (ECW) to total body water (TBW) ratio was measured by multifrequency bioelectrical impedance. Peritoneal transport characteristics were measured with a standard peritoneal equilibration test. Patients had a second follow-up visit with the same measurements. Univariable and multivariable mixed linear regression models were conducted with ECW/TBW as the dependent variable.

RESULTS

A total of 155 patients were enrolled with a median follow-up time of 12 months. Median dialysis vintage was 13.5 ± 3.4 months. Overall mean value of ECW/TBW was 39.3% ± 1.1. In multivariable analysis, factors positively associated with ECW/TBW were: Age (P < .001), diabetes (P = .002), and SBP (P = .028). Factors negatively associated with ECW/TBW were: nPNA (P = .001), serum albumin (P < .001) and PTH (P = .014). None of the considered variable showed a significant interaction with time.

CONCLUSION

We confirm a high prevalence of fluid overload in PD patients and show that it is strongly associated with older age, diabetes, hypoalbuminemia and protein energy wasting. In contrast, when PD prescription is tailored to patient's individual characteristics, residual renal function, PD modality and peritoneal characteristics are not decisive in controlling volume status.

Is high-volume post-dilution haemodiafiltration associated with risk of fluid volume imbalance? A national multicentre cross-sectional cohort study

Background

Fluid overload is frequent among hemodialysis (HD) patients. Dialysis therapy itself may favor sodium imbalance from sodium dialysate prescription. As on-line hemodiafiltration (OL-HDF) requires large amounts of dialysate infusion, this technique can expose to fluid accumulation in case of a positive sodium gradient between dialysate and plasma. To evaluate this risk, we have analyzed and compared the fluid status of patients treated with HD or OL-HDF in French NephroCare centers.

Method

This is a cross-sectional and retrospective analysis of prevalent dialysis patients. Data were extracted from the EUCLID5 data base. Patients were split in 2 groups (HD and OL-HDF) and compared as whole group or matched patients for fluid status criteria including predialysis relative fluid overload (RelFO%) status from the BCM^®.

Results

2242 patients (age 71 years; female: 39%; vintage: 38 months; Charlson index: 6) were studied. 58% of the cohort were prescribed post-dilution OL-HDF. Comparing the HD and OL-HDF groups, there was no difference between HD and OL-HDF patients regarding the predialysis systolic BP, the interdialytic weight gain, the dialysate-plasma sodium gradient, and the predialysis RelFO%. The stepwise logistic regression did not find dialysis modality (HD or OL-HDF) associated with fluid overload or high predialysis systolic blood pressure. In OL-HDF patients, monthly average convective or weekly infusion volumes per session were not related with the presence of fluid overload.

Conclusions

In this cross-sectional study we did not find association between the use of post-dilution OL-HDF and markers of fluid volume excess. Aligned dialysis fluid sodium concentrations to patient predialysis plasma sodium and regular monitoring of fluid volume status by bioimpedance spectroscopy may have been helpful to manage adequately the fluid status in both OL-HDF and HD patients.

The Influence of Glucose Exposure Load and Peritoneal Membrane Transport on Body Composition and Nutritional Status Changes after 1 Year on Peritoneal Dialysis

Background

The characteristics of peritoneal membrane transport differ among patients, affecting the prescription of peritoneal dialysis (PD) modality and glucose exposure in order to achieve an effective dialysis. This study aims to verify the influence of glucose exposure load and peritoneal membrane transport on body composition and nutritional status changes after the first year of PD.

Methods

We examined a cohort of 85 incident PD patients during the first year of treatment. We established a cut-off of 5% to define changes in dry weight (DW), lean tissue mass (LTM), and fat mass (FM).

Results

In total, 50.6% of the patients presented DW gain, 41.2% showed LTM loss, and 65.9% presented FM gain. Over the time (T0 – T12), we found significant differences in DW, body mass index (BMI), adipose tissue mass (ATM), FM and fat tissue index (FTI). Patients with lower dialysate-to-plasma creatinine ratio showed DW and FM gain. We observed a higher percentage of nonfast transporters in DW gain when comparing with DW no gain. As for glucose exposure load, no body composition changes were seen.

Conclusions

Most patients presented DW gain, FM gain, and LTM loss. The characteristics of peritoneal membrane transport affected DW during the first year, changes being greater in nonfast than in fast transporters.

The impact of volume overload on technique failure in incident peritoneal dialysis patients

Background

Technique failure in peritoneal dialysis (PD) can be due to patient- and procedure-related factors. With this analysis, we investigated the association of volume overload at the start and during the early phase of PD and technique failure.

Methods

In this observational, international cohort study with longitudinal follow-up of incident PD patients, technique failure was defined as either transfer to haemodialysis or death, and transplantation was considered as a competing risk. We explored parameters at baseline or within the first 6 months and the association with technique failure between 6 and 18 months, using a competing risk model.

Results

Out of 1092 patients of the complete cohort, 719 met specific inclusion and exclusion criteria for this analysis. Being volume overloaded, either at baseline or Month 6, or at both time points, was associated with an increased risk of technique failure compared with the patient group that was euvolaemic at both time points. Undergoing treatment at a centre with a high proportion of PD patients was associated with a lower risk of technique failure.

Conclusions

Volume overload at start of PD and/or at 6 months was associated with a higher risk of technique failure in the subsequent year. The risk was modified by centre characteristics, which varied among regions.

Using Bioimpedance Spectroscopy to Assess Volume Status in Dialysis Patients

The aim of the paper is to reflect on the current status of bioimpedance spectroscopy (BIS) in fluid management in dialysis patients. BIS identifies fluid overload (FO) as a virtual (overhydration) compartment, which is calculated from the difference between the measured extracellular volume and the predicted values based on a fixed hydration of lean and adipose tissue mass. FO is highly prevalent in both hemodialysis (HD) and peritoneal dialysis (PD) patients, while levels of FO are at a population level comparable between PD patients and HD patients when measured before the dialysis treatment. Even mild levels of FO are independently related to outcome in patients on HD, PD as well as in nondialysis patients with advanced chronic kidney disease. FO is not only related to left ventricular hypertrophy (LVH) but also forms part of a multidimensional spectrum with noncardiovascular risk factors such as malnutrition and inflammation. Even after multiple adjustments, FO remains an independent predictor of mortality. BIS-assisted adjustment of dry weight in HD patients has been shown to improve hypertension control and LVH and has resulted in a decline in intradialytic symptomatology. On the other hand, with increased fluid removal, target weight may not always be reached due to an increase in intradialytic symptomatology, and care should be applied in target weight adjustment in fluid overloaded patients with severe malnutrition and/or inflammation. Although a reduction in hospitalization rate was suggested, the effect of BIS-guided dry weight adjustment on mortality has not yet been shown, however, although available studies are underpowered. In PD patients, results have been more equivocal, which may be partly related to differences in treatment protocols or study populations. Future large-scale studies are needed to assess the full potential of BIS.

Sodium toxicity in peritoneal dialysis: mechanisms and "solutions"

The major trials in peritoneal dialysis (PD) have demonstrated that increasing peritoneal clearance of small solutes is not associated with any advantage on survival, whereas sodium and fluid overload heralds higher risk of death and technique failure. On the other hand, higher sodium and fluid overload due to loss of residual kidney function (RKF) and higher transport membrane is associated with poor patient and technique survival. Recent experimental studies also show that, independently from fluid overload, sodium accumulation in the peritoneal interstitium exerts direct inflammatory and angiogenetic stimuli, with consequent structural and functional changes of peritoneum, while in patients with Chronic Kidney Disease sodium stored in interstitial skin acts as independent determinant of left ventricular hypertrophy. Noteworthy, this tissue pool of sodium is modifiable being removed by dialysis. Therefore, novel PD strategies to optimize sodium removal, including the use of bimodal and/or low-sodium solutions, are actively tested. Nonetheless, a holistic approach aimed at preserving peritoneal function and the kidney may represent the key of therapy success in the hard task of preserving adequate sodium balance in PD patients. In this review, we describe the available evidence on sodium toxicity in PD, either related or unrelated to fluid overload, and we also discuss about possible "solutions" to preserve or restore sodium balance in PD patients.

Lower Phase Angle Measured by Bioelectrical Impedance Analysis Is a Marker for Increased Mortality in Incident Continuous Ambulatory Peritoneal Dialysis Patients

OBJECTIVE

Phase angle (PA) determined by bioelectrical impedance analysis has been suggested to be a predictor of death in a variety of disease conditions, but its associations with outcomes have not yet been assessed in a large continuous ambulatory peritoneal dialysis (CAPD) patient cohort. The aim of the present study was to examine the association of PA with risks for all-cause and cardiovascular death in patients treated with CAPD.

METHODS

Incident CAPD patients were enrolled from January 1, 2010 to December 31, 2015 and were followed until December 31, 2017. Multifrequency bioelectrical impedance analysis was conducted in the morning with patients in a fasting state. Multivariable linear regression analyses were performed to study the relationships between PA and other variables. Cox proportional hazard models were used to evaluate the association between PA and mortality.

RESULTS

A total of 760 incident CAPD patients were enrolled in this study. Patients have a median PA value of 4.59° ranging from 2.30° to 7.22°. Aging, presence of diabetes mellitus, and fluid overload were independently associated with lower PA, whereas male sex, higher body mass index, higher serum levels of albumin and creatinine, and better residual renal function were independently associated with higher PA in a multivariable linear regression model. A total of 125 (16.4%) patients died during a median follow-up of 42 months. In the Cox model with adjustment for confounders, PA was significantly associated with all-cause and cardiovascular mortality in incident CAPD patients (hazard ratio, 0.584; 95% confidence interval, 0.403 to 0.844, P = .004; hazard ratio, 0.597; 95% confidence interval, 0.359 to 0.993, P = .047, respectively).

CONCLUSIONS

PA reflected a combined dimension of the illness including deranged hydration status and nutritional status. Lower PA was associated with both all-cause and cardiovascular death in patients with CAPD.

Residual Renal Function and Effect of Low-Sodium Solution on Blood Pressure in Peritoneal Dialysis Patients

Background:Residual renal function (RRF) affects sodium and fluid balance. The aim of this analysis was to examine the impact of RRF on the effect of a sodium-reduced peritoneal dialysis fluid (PDF) on blood pressure (BP).Methods:This is a post-hoc analysis of a prospective, randomized, controlled double-blind clinical trial with 82 patients on continuous ambulatory PD (CAPD) treated with a low-sodium (125 mmol/L Na) or a standard-sodium (134 mmol/L Na) PDF. Subgroups according to glomerular filtration rate (GFR) at baseline (≤ / > 6 mL/min/1.73 m²) were analyzed for BP and antihypertensive medication.Results:In the low-GFR group on low-sodium PDF (N = 26), systolic BP was reduced from 152 ± 24 mmHg at baseline to 137 ± 21 mmHg at week 12, diastolic BP from 90 ± 16 mmHg to 83 ± 11 mmHg. In the low-GFR group on standard-sodium PDF and in the high-GFR group on both PDF types, only minor changes were observed. For the low-GFR subgroup, the confounder-adjusted mean study group difference in systolic BP at week 12 between low-sodium and standard-sodium PDF was -16.9 (95% confidence interval [CI] -27.2 to -6.6) mmHg, for diastolic BP, it was -7.0 (95% CI -12.6 to -1.4) mmHg. In both GFR subgroups, more patients had a reduced daily dose of antihypertensive medication and fewer patients an increased daily dose in the low-sodium compared with the standard-sodium group at week 12.Conclusions:The reduction of BP with a sodium-reduced PDF seems to be more effective in patients with no or low RRF than in patients with residual capacity of renal sodium and fluid control.

Evolution Over Time of Volume Status and PD-Related Practice Patterns in an Incident Peritoneal Dialysis Cohort

BACKGROUND AND OBJECTIVES

Volume overload is frequent in prevalent patients on kidney replacement therapies and is associated with outcome. This study was devised to follow-up volume status of an incident population on peritoneal dialysis (PD) and to relate this to patient-relevant outcomes.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This prospective cohort study was implemented in 135 study centers from 28 countries. Incident participants on PD were enrolled just before the actual PD treatment was started. Volume status was measured using bioimpedance spectroscopy before start of PD and thereafter in 3-month intervals, together with clinical and laboratory parameters, and PD prescription. The association of volume overload with time to death was tested using a competing risk Cox model.

RESULTS

In this population of 1054 participants incident on PD, volume overload before start of PD amounted to 1.9±2.3 L, and decreased to 1.2±1.8 L during the first year. At all time points, men and participants with diabetes were at higher risk to be volume overloaded. Dropout from PD during 3 years of observation by transfer to hemodialysis or transplantation (23% and 22%) was more prevalent than death (13%). Relative volume overload >17.3% was independently associated with higher risk of death (adjusted hazard ratio, 1.59; 95% confidence interval, 1.08 to 2.33) compared with relative volume overload ≤17.3%. Different practice patterns were observed between regions with respect to proportion of patients on PD versus hemodialysis, selection of PD modality, and prescription of hypertonic solutions.

CONCLUSIONS

In this large cohort of incident participants on PD, with different treatment practices across centers and regions, we found substantial volume overload already at start of dialysis. Volume overload improved over time, and was associated with survival.

Persistent overhydration is associated with a significant risk of peritoneal infection by enteric pathogens in patients treated with peritoneal dialysis

BACKGROUND

Overhydration (OH) complicates frequently the clinical course of Peritoneal Dialysis (PD) patients, and keeps a controversial association with the risk of peritoneal infection. The main objective of this study was to disclose an association between persistent OH and the risk of enteric peritonitis in a relatively large sample of patients undergoing PD.

METHOD

Following a prospective design, we monitorized systematically body composition of patients treated with PD in our unit (2011-2016), searching for a correlation with the ensuing risk of peritonitis, with an emphasis on the association between persistent OH (main study variable) and the risk of infection by enteric pathogens (main outcome). Essential demographic, clinical and laboratory variables with a potential influence on the risk of peritonitis were recorded. We used multivariate survival analysis to clarify the specific effect of different body composition parameters on the main outcome.

MAIN RESULTS

We included 139 patients for analysis (mean follow-up 24 months). Sixty-three patients suffered at least one peritonitis, and 17 had at least one diagnosis of enteric peritonitis. Univariate analysis disclosed a general trend to an increased risk of enteric peritonitis in overhydrated patients, as evidenced by associations of this outcome with mean extracellular water/intracellular water (ECW/ICW) (p=.007), OH/ECW (p=.033) and ECW/total body water (ECW/TBW) (p=.004) ratios, but not with absolute OH values. Multivariate analysis confirmed similar associations or trends (RR: 3.48, 95% CI: 1.03-14.59; p=.046, highest versus lowest tertile of ECW/ICW, RR: 2.31, 95% CI: 0.98-6.56; p=.061, highest versus lowest tertile of OH/ECW, and RR: 6.33, 95% CI: 1.37-19.37; p=.011, highest versus lowest tertile of ECW/TBW). On the contrary, no apparent association was detected between OH and the overall risk of peritoneal infection.

CONCLUSION

Persistent overhydration portends a significant risk of peritoneal infection by enteric pathogens, among patients undergoing chronic PD.

Classification of Hydration in Clinical Conditions: Indirect and Direct Approaches Using Bioimpedance

Although the need to assess hydration is well recognized, laboratory tests and clinical impressions are impractical and lack sensitivity, respectively, to be clinically meaningful. Different approaches use bioelectrical impedance measurements to overcome some of these limitations and aid in the classification of hydration status. One indirect approach utilizes single or multiple frequency bioimpedance in regression equations and theoretical models, respectively, with anthropometric measurements to predict fluid volumes (bioelectrical impedance spectroscopy-BIS) and estimate fluid overload based on the deviation of calculated to reference extracellular fluid volume. Alternatively, bioimpedance vector analysis (BIVA) uses direct phase-sensitive measurements of resistance and reactance, measured at 50 kHz, normalized for standing height, then plotted on a bivariate graph, resulting in a vector with length related to fluid content, and direction with phase angle that indexes hydration status. Comparison with healthy population norms enables BIVA to classify (normal, under-, and over-) and rank (change relative to pre-treatment) hydration independent of body weight. Each approach has wide-ranging uses in evaluation and management of clinical groups with over-hydration with an evolving emphasis on prognosis. This review discusses the advantages and limitations of BIS and BIVA for hydration assessment with comments on future applications.

Assessment and Management of Hypertension among Patients on Peritoneal Dialysis

Approximately 7%-10% of patients with ESKD worldwide undergo peritoneal dialysis (PD) as kidney replacement therapy. The continuous nature of this dialytic modality and the absence of acute shifts in pressure and volume parameters is an important differentiation between PD and in-center hemodialysis. However, the burden of hypertension and prognostic association of BP with mortality follow comparable patterns in both modalities. Although management of hypertension uses similar therapeutic principles, long-term preservation of residual diuresis and longevity of peritoneal membrane function require particular attention in the prescription of the appropriate dialysis regimen among those on PD. Dietary sodium restriction, appropriate use of icodextrin, and limited exposure of peritoneal membrane to bioincompatible solutions, as well as adaptation of the PD regimen to the peritoneal transport characteristics, are first-line therapeutic strategies to achieve adequate volume control with a potential long-term benefit on technique survival. Antihypertensive drug therapy is a second-line therapeutic approach, used when BP remains unresponsive to the above volume management strategies. In this article, we review the available evidence on epidemiology, diagnosis, and treatment of hypertension among patients on PD and discuss similarities and differences between PD and in-center hemodialysis. We conclude with a call for randomized trials aiming to elucidate several areas of uncertainty in management of hypertension in the PD population.

Clinical Studies of Interventions to Mitigate Cardiovascular Risk in Peritoneal Dialysis Patients

Cardiovascular disease (CVD) is highly prevalent in the peritoneal dialysis (PD) population, affecting up to 60% of cohorts. CVD is the primary cause of death in up to 40% of PD patients in Australia, New Zealand, and the United States. Cardiovascular mortality rates are reported to be approximately 14 per 100 patient-years, which are 10- to 20-fold greater than those of age- and sex-matched controls. The excess risk of CVD is related to a combination of traditional risk factors (such as hypertension, dyslipidemia, obesity, smoking, sedentary lifestyle, and insulin resistance), nontraditional (kidney disease-related) risk factors (such as anemia, chronic volume overload, inflammation, malnutrition, hyperuricemia, and mineral and bone disorder), and PD-specific risk factors (such as dialysis solutions, glycation end products, hypokalemia, residual kidney function, and ultrafiltration failure). Interventions targeting these factors may mitigate cardiovascular risk, although high-level clinical evidence is lacking. This review summarizes the evidence relating to cardiovascular interventions targeting modifiable CVD risk factors in PD patients, as well as highlighting the key recommendations of the International Society for Peritoneal Dialysis Cardiovascular and Metabolic Guidelines.

Fluid management and bioimpedance study in peritoneal dialysis

PURPOSE OF REVIEW

Maintaining euvolaemia is an essential yet challenging objective in management of patients on peritoneal dialysis. Optimal method to assess volume status remains to be determined. In this review, we will discuss the risk factors and clinical outcomes of fluid overload in PD patients, and examine the role of bioimpedance study in fluid management.

RECENT FINDINGS

Applying bioimpedance study to measure body composition has attracted increasing attention because it is noninvasive and provides point-of-care assessment of fluid status. Observational studies suggested that presence of residual renal function did not necessarily protect peritoneal dialysis patients from developing fluid overload. This reinforces the importance of fluid restriction in peritoneal dialysis patients, in whom the thirst sensation could be exacerbated by hyperglycaemia. Notably, fluid overload is present in significant portion of asymptomatic patients. Moreover, bioimpedance-defined fluid overload is associated with increase in all-cause mortality, technique failure and possibly excess peritonitis rate.

SUMMARY

Although future studies should investigate the clinical benefit of bioimpedance-guided fluid management in high-risk subgroup, raising awareness among clinicians, together with structured clinical assessment and dietary counselling are the cornerstone to maintain stable fluid status.

Asymptomatic fluid overload predicts survival and cardiovascular event in incident Chinese peritoneal dialysis patients

Background

Fluid overload is common among asymptomatic peritoneal dialysis (PD) patients. We aim to determine the prevalence and prognostic significance of fluid overload, as measured by bioimpedance spectroscopy, in asymptomatic incident PD patients.

Methods

We performed a single-center study on 311 incident PD patients. Volume status was represented by the volume of overhydration (OH), OH/extracellular water (ECW) ratio, ECW/total body water (TBW) ratio, and ECW to intracellular water (ICW) ratio (E:I ratio). Patient survival, technique survival and cardiovascular event-free survival were determined.

Results

The median period of follow up was 27.3 months. Fluid overload was present in 272 patients (87.5%) when defined as OH volume over 1.1L. All hydration parameters significantly correlated with Charlson Comorbidity Index, and inversely with total Kt/V, and serum albumin. Multivariate cause-specific Cox analysis showed that volume status independently predicted patient survival; every 0.1 unit increase in E:I ratio was associated with 24.5% increase in all-cause mortality (adjusted cause-specific hazard ratio [ACSHR] 1.245, p = 0.002). Hydration status was also an independent predictor of cardiovascular event-free survival after excluding hospital admission for congestive heart failure; each 0.1 unit increase in E:I ratio was associated with 18.7% decrease in cardiovascular event-free survival (ACSHR 1.187, p = 0.011). In contrast, hydration parameters were not associated with technique survival.

Conclusions

Fluid overload is common in asymptomatic incident PD patients and is a strong predictor of patient survival and cardiovascular event. The impact of bioimpedance spectroscopy-guided fluid management on the outcome of PD patients deserves further study.

Hydration and nutritional status in patients on home-dialysis-A single centre study

BACKGROUND

Over-hydration (OH) and malnutrition are prevalent among patients on dialysis therapy. The prevalence of OH and malnutrition as well as the risk factors associated with OH and malnutrition in our patients on home peritoneal dialysis (PD) and home haemodialysis (HD) are examined.

DESIGN AND METHODS

This was a cross-sectional study. The hydration and nutritional status of the study groups were assessed by a Body Composition Monitor. Patients who were stable on home dialysis therapy for over one year were invited to participate. Univariate and multivariate analyses were performed to identify associated factors and determine the predictors of OH and malnutrition, respectively.

RESULTS

Eighty-eight patients (41 PD and 47 home HD) were recruited. A 32.95% of our patients on home dialysis therapy were in OH status. There was a significance difference in the prevalence of hydration status between patients on PD and home HD (p = 0.014), as overhydration was more common in patients on PD than home HD (46.34 vs. 21.28%). Dehydration was more common in patients on home HD than PD (29.79 vs. 9.76%). Male gender, decreasing haemoglobin level and presence of diabetes mellitus (DM) were risk factors of OH on multivariable analysis. There was no significance difference in the prevalence of malnutrition between patients on PD and home HD (p = 0.27). Increasing Fat Tissue Index (FTI), height and patients on PD therapy were at higher risk of malnutrition.

CONCLUSION

OH and malnutrition were prevalent patients on home dialysis therapy.

Repeated Bioimpedance Measurements Predict Prognosis of Peritoneal Dialysis Patients

BACKGROUND

Fluid overload is a major risk factor for mortality in patients undergoing peritoneal dialysis (PD). However, few studies have investigated the effect of chronic exposure to sustained fluid overload on long-term outcomes.

METHOD

A total of 284 prevalent PD patients were included in this prospective study. Repeated multifrequency body composition analysis was performed 12 months apart, and 1-year cumulative chronic fluid overload were used to predict all-cause mortality and the risk for transfer to hemodialysis (HD) during the ensuing 15.6 ± 9.1 months.

RESULTS

The prevalence of fluid overload was approximately 27%. Interestingly, a substantial number of hypervolemic patients at first test were persistently hypervolemic at their second test. With this, chronic fluid overload was observed in 18.3% (n = 52). Notably, most of chronic fluid overload patients had diabetes (86.5%), and it was accompanied by concomitant changes in peritoneal membrane characteristics, a higher progression rate to high transporter. The risk of transfer to HD increased 2.8 times in patients with chronic fluid overload than in those without. Also, it significantly increased the risk of mortality (p = 0.038). Surprisingly, subgroup analysis found that patients with euvolemic status at follow-up experienced no mortality despite being in a fluid overload state at baseline.

CONCLUSIONS

One-year chronic exposure to fluid overload is a strong independent risk factor for transfer to HD and death in prevalent PD patients. Although the fluid status of most PD patients is not easily changed over time, becoming euvolemic during the entire PD treatment period seems to be very important.

Does Routine Bioimpedance-Guided Fluid Management Provide Additional Benefit to Non-Anuric Peritoneal Dialysis Patients? Results from COMPASS Clinical Trial

INTRODUCTION

In peritoneal dialysis (PD) patients, volume overload is related to cardiac dysfunction and mortality, while intravascular volume depletion is associated with a rapid decline in the residual renal function (RRF). This study sought to determine the clinical usefulness of bioimpedance spectroscopy (BIS)-guided fluid management for preserving RRF and cardiac function in PD patients.

SUBJECTS AND METHODS

This is a multicenter, prospective, open-label study that was conducted over a 1-year period (NCT01887262). Non-anuric (urine volume > 500 mL/day) subjects on PD were enrolled. Subjects in the control group received fluid management based on the clinical information alone. Those in the BIS group received BIS-guided fluid management along with clinical information.

RESULTS

The subjects (N = 137, mean age 51.3 ± 12.8 years, 54% male) were randomly assigned to the BIS group (n = 67) or to the control group (n = 70). There were no significant differences between the 2 groups with regard to age, sex ratio, cause of kidney failure, duration of PD, baseline comorbidity, RRF, PD method, or peritoneal transport type. At baseline, the 2 groups were not different in terms of RRF (glomerular filtration rate [GFR], 5.1 ± 2.9 vs 5.5 ± 3.7 mL/min/1.73 m²). After follow-up, changes in the GFR between the 2 groups were not different (-1.5 ± 2.4 vs -1.3 ± 2.6 mL/min/1.73 m², p = 0.593). Over the 1-year study period, both groups maintained stability of various fluid status parameters. Between the 2 groups, there were no differences in the net change of various fluid status parameters such as overhydration (OH) and extracellular water/total body water (ECW/TBW). A net change in ECW over 1 year was slightly but significantly higher in the control group (net increase, 0.57 ± 1.27 vs 0.05 ± 1.63 L, p = 0.047). However, this difference was not translated into an improvement in RRF in the BIS group. There were no differences in echocardiographic parameters or arterial stiffness at the end of follow-up.

CONCLUSION

Routine BIS-guided fluid management in non-anuric PD patients did not provide additional benefit in volume control, RRF preservation, or cardiovascular (CV) parameters. However, our study cannot be generalized to the whole PD population. Further research is warranted in order to investigate the subpopulation of PD patients who may benefit from routine BIS-guided fluid management.

Chiarello P. Estimation of Body Composition and Water Data Depends on the Bioelectrical Impedance Device

Overweight, obese and chronic kidney disease patients have an altered and negative body composition being its assessment important. Bioelectrical impedance analysis is an easy-to-operate and low-cost method for this purpose. This study aimed to compare and correlate data from single- and multi-frequency bioelectrical impedance spectroscopy applied in subjects with different body sizes, adiposity, and hydration status. It was a cross-sectional study with 386 non-chronic kidney disease volunteers (body mass index from 17 to 40 kg/m2), 30 patients in peritoneal dialysis, and 95 in hemodialysis. Bioelectrical impedance, body composition, and body water data were assessed with single- and multi-frequency bioelectrical impedance spectroscopy. Differences (95% confidence interval) and agreements (Bland-Atman analyze) between devices were evaluated. The intraclass correlation coefficient was used to measure the strength of agreement and Pearson's correlation to measure the association. Regression analyze was performed to test the association between device difference with body mass index and overhydration. The limits of agreement between devices were very large. Fat mass showed the greatest difference and the lowest intraclass and Pearson's correlation coefficients. Pearson's correlation varied from moderate to strong and the intraclass correlation coefficient from weak to substantial. The difference between devices were greater as body mass index increased and was worse in the extremes of water imbalance. In conclusion, data obtained with single- and multi-frequency bioelectrical impedance spectroscopy were highly correlated with poor agreement; the devices cannot be used interchangeably and the agreement between the devices was worse as body mass index and fat mass increased and in the extremes of overhydration.

Irisin and Volume Overload are Associated with Protein Energy Wasting in Peritoneal Dialysis Patients

BACKGROUND/AIMS

Protein energy wasting (PEW) is a common medical phenomenon that is observed in maintenance dialysis patients. PEW also increases morbidity and mortality of these patients. Its pathogenesis is unclear. We hypothesize that serum irisin levels and volume overload may induce PEW in peritoneal dialysis (PD) patients. The aim of this study is to measure serum irisin levels, evaluate volume status of PD patients, and study their correlations with PEW in PD patients.

METHODS

This study is a cross-sectional study with 160 PD patients from the PD center of Peking University Third Hospital and 35 healthy control subjects. PD patients were divided into PEW group and non-PEW group according to PEW diagnosis criteria. Serum irisin concentrations were measured by ELISA. Volume overload status (volume overload is defined as overhydration value ≥2 liters) of PD patients was analyzed by bioelectrical impedance.

RESULTS

The serum irisin levels were significantly lower in PD patients compared with those of the controls (113.2±11.8 ng/ml vs. 464.2±37.4 ng/ml, P<0.01). The serum irisin levels were lower in PD patients with PEW than those of the patients without PEW (106.5±15.2 ng/ml vs. 117.4±17.6 ng/ml, P<0.01). PEW is more prevalent in patients with volume overload than patients without volume overload (62.5% vs. 43.1%, x2=5.756, P=0.016); however, no direct relationship was found between irisin levels and volume overload status. The independent influencing factors of PEW were serum irisin, serum albumin, and volume overload.

CONCLUSION

Our results are the first to provide clinical evidence of the association between serum irisin, volume overload, and PEW in PD patients. PEW may inhibit the release or synthesis of irisin from skeletal muscles, and volume overload may aggravate PEW in PD patients.

Fluid overload as a major target in management of cardiorenal syndrome: Implications for the practice of peritoneal dialysis

Congestion is an integral component of cardiorenal syndrome and portends an adverse impact on the outcomes. Recent studies suggest that congestion has the ability of modulating the interactions between the kidney and the heart in this setting. Peritoneal dialysis (PD) is a home-based therapeutic modality that is not only offered to patients with end-stage renal disease to provide solute clearance and ultrafiltration, but it has also been used in patients with refractory heart failure and fluid overload to help optimize volume status. Several uncontrolled studies and case series have so far evaluated the role of PD in management of hypervolemia for patients with heart failure. They have generally reported favorable results in this setting. However, the data on the outcomes of patients with end-stage renal disease and concomitant heart failure is mixed, and the proposed theoretical advantages of PD might not translate into improved clinical endpoints. Congestion is prevalent in this patient population and has a significant effect on their survival. As studies suggest that a significant subset of patients with end-stage renal disease who receive PD therapy are hypervolemic, suboptimal management of congestion could at least in part explain these conflicting results. PD is a highly flexible therapeutic modality and the choice of techniques, regimens, and solutions can affect its ability for optimization of fluid status. This article provides an overview of the currently available data on the role and clinical relevance of congestion in patients with cardiorenal syndrome and reviews potential options to enhance decongestion in these patients.

Peritoneal Water Transport Characteristics of Diabetic Patients Undergoing Peritoneal Dialysis: A Longitudinal Study

BACKGROUND

Volume overload is frequent in diabetics undergoing peritoneal dialysis (PD), and may play a significant role in the excess mortality observed in these patients. The characteristics of peritoneal water transport in this population have not been studied sufficiently.

METHOD

Following a prospective, single-center design we made cross-sectional and longitudinal comparisons of peritoneal water transport in 2 relatively large samples of diabetic and nondiabetic PD patients. We used 3.86/4.25% glucose-based peritoneal equilibration tests (PET) with complete drainage at 60 min, for these purposes.

MAIN RESULTS

We scrutinized 59 diabetic and 120 nondiabetic PD patients. Both samples showed relatively similar characteristics, although diabetics were significantly more overhydrated than nondiabetics. The baseline PET disclosed lower ultrafiltration (mean 439 mL diabetics vs. 532 mL nondiabetics, p = 0.033) and sodium removal (41 vs. 53 mM, p = 0.014) rates in diabetics. One hundred and nine patients (36 diabetics) underwent a second PET after 12 months, and 45 (14 diabetics) underwent a third one after 24 months. Longitudinal analyses disclosed an essential stability of water transport in both groups, although nondiabetic patients showed a trend where an increase in free water transport (p = 0.033) was observed, which was not the case in diabetics.

CONCLUSIONS

Diabetic patients undergoing PD present lower capacities of ultrafiltration and sodium removal than their nondiabetic counterparts. Longitudinal analyses disclose an essential stability of water transport capacities, both in diabetics and nondiabetics. The clinical significance of these differences deserves further analysis.

Relationship between bioimpedance-determined body composition and peritoneal transport in peritoneal dialysis

PURPOSE

In peritoneal dialysis (PD) patients, body fluid homeostasis is dependent on peritoneal elimination of water and solutes. Patients with less favorable peritoneal transport parameters should be more overhydrated. Despite this, the association between faster transport and overhydration (OH) is weak, and the factors that influence hydration status are still poorly characterized. Modified peritoneal equilibration tests (PET) offer us new parameters that might correlate better with hydration status, like free water transport (FWT). The aim of this study was thus to establish the relationships between new peritoneal transport parameters and body composition parameters estimated by bioimpedance spectroscopy (BIS).

METHODS

Prospective observational study on incident PD patients with a baseline and 1-year follow-up evaluation.

RESULTS

61 patients were included in the baseline evaluation, 19 of whom had a 1-year follow-up evaluation; 67.2% were fluid overloaded. There was a negative correlation between D/P creatinine and FWT (r = -0.598, p = 0.000). The fraction of FWT was negatively correlated with OH (r = -0.302, p = 0.018). Peritoneal protein losses (PPL) were also correlated with OH (r = 0.287, p = 0.028). There were no significant differences in OH according to small-solute transport status or fluid output parameters. After 1 year, we observed a significant worsening of renal function and an improvement in 24-hour ultrafiltration (UF) and hydration status, but we detected no differences in peritoneal transport of water or solutes that could explain these changes.

CONCLUSIONS

There is a poor relationship between kidney/peritoneal function parameters and body composition parameters. The fraction of FWT and PPL may be underestimated markers of peritoneal health and of its contribution to the hydration status.

Should sodium removal in peritoneal dialysis be estimated from the ultrafiltration volume?

In peritoneal dialysis (PD), ultrafiltration (UF) volume is the sum of solute-free- and solute-coupled-water removal, a dynamic process throughout the entire dwell exerted via aquaporin-1 (AQP1) and small pores, respectively. Determination of sodium sieving is used as a parameter for AQP1 function analysis, while coupled water removal is essential for adequate sodium and water balance and thus blood pressure control. The diffusive capacity of glucose via the small pores determines the dynamic crystalloid osmotic gradient. The osmotic conductance, i.e., milliliter of UF per gram of glucose absorbed, quantifies cooperation between small-pores and AQP1 channels. In continuous ambulatory peritoneal dialysis, with dwell times beyond glucose-induced sodium-sieving effects, approximate dialytic sodium removal (DSR) may be estimated from the UF volume (in average 100 mmol Na/L UF), while DSR is lower, with shorter cycle times, in automated PD (APD); therefore, effluent sodium concentrations should be measured. Applying dialysis mechanics, i.e., varying dwell time and dwell volume-as proposed in adapted APD to the PD prescription-may provide unmatched high DSR relative to UF volume, findings which are not sufficiently explained by the three-pore model of PD. Overall DSR should therefore be measured rather than estimated from UF volume.