The importance of overhydration in determining peritoneal dialysis technique failure and patient survival in anuric patients

Predictors and prognostic significance of the volume load trajectory: a longitudinal study in patients on peritoneal dialysis

Volume overload in peritoneal dialysis patients is a common issue that can lead to poor prognosis. We employed a group trajectory model to categorize volume load trajectories and examined the factors associated with each trajectory class to explore the impact of different trajectory groups on clinical prognosis and residual renal function (RRF). This single-center prospective cohort study included 214 patients on maintenance peritoneal dialysis within a tertiary hospital. The ratio of extracellular water to total body water was measured using Bioimpedance analysis. The SAS 9.4 PROC Traj procedure was used to examine the group-based trajectory of the patients. A multivariate logistic regression model was used to calculate the adjusted odds ratios (aOR) of the associated factors to predict the trajectory class of participants. The average age of the included patients was 53.56 (SD: 11.77) years, with a male proportion of 46.7% and a median follow-up time of 6 months. The normal stable group accounted for 35.05% of the total population and maintained a normal and stable level, the moderate stable group accounted for 52.8% of the total population and showed a slightly higher and stable level, and the high fluctuation group accounted for 12.15% of the total population and showed a high and fluctuating level. A multivariate logistic regression analysis revealed that age, diabetes, and albumin levels are significant factors influencing the categorization of volume load trajectories. There were statistically significant differences in both the technical survival rate and the loss of residual renal function among the three trajectory groups.

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.

Peritoneal sodium removal compared to glucose absorption in peritoneal dialysis patients treated by continuous ambulatory peritoneal dialysis and automated peritoneal dialysis with and without a daytime exchange

Sodium removal in peritoneal dialysis (PD) depends on convective clearance, typically generated by a glucose gradient, but this can result in glucose absorption. We wished to determine which factors determine peritoneal sodium losses to glucose absorption (PD Na/Gluc). Peritoneal sodium losses and glucose absorption were calculated from measured 24-h collections of PD effluent, in patients attending for assessment of peritoneal membrane function. Five hundred and fifty eight patients; 317 (56.8%) males, mean age 56.1 ± 16.0 years, were studied, 281 treated by automated peritoneal dialysis (APD) with a daytime exchange (50.4%); 179 (32.1%) by APD and 98 (17.6%) by continuous ambulatory peritoneal dialysis (CAPD). All patients used glucose containing dialysates, with 352 (63.1%) using icodextrin and 210 (37.6%) hypertonic (22.7 g/L glucose) dialysates. The ratio of PD Na/Gluc was 0.14 (0.02-0.29). Patients using icodextrin had a higher ratio (0.16 (0.03-0.32) versus 0.11 (-0.02-0.26), P < .001), as did those using 22.7 g/L glucose versus 13.6 g/L (0.16 (0.06-0.32) versus 0.13 (-0.01-0.19), P < .01), and CAPD versus APD (0.18 (0.05-0.36) versus 0.11 (0.0-0.27), P < .05), respectively. A multivariable model showed that 24-h ultrafiltration (odds ratio [OR] 7.6 (95% confidence interval [3.9-14.8]), P < .001 was associated with increased PD Na/Gluc, whereas APD (OR 0.19 (0.06-0.62), P < .01 and increased extracellular water to total body water (OR 0.001 [0-0.08], P = .03) were associated with lower ratios. Twenty four-hour peritoneal ultrafiltration was strongly associated with PD Na/Gluc, whereas patients treated with APD cyclers without a daytime icodextrin exchange and those with an increased extracellular water to total body water had lower peritoneal sodium losses but with greater peritoneal glucose absorption.

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.

Technique Failure in Peritoneal Dialysis: Etiologies and Risk Assessment

Technique failure (TF) is a well-recognized challenge encountered in patients undergoing peritoneal dialysis (PD). Identification of patients at risk for this complication is of utmost importance. Early detection of patients at risk and development of preventative strategies can improve technique survival that may lead to an increased utilization of PD. It will also promote a safe and planned transfer to hemodialysis once a patient identified with TF. The aim of this review is to summarize risk factors and scenarios associated with TF focusing on prevention of remediable factors at their earliest stage. Furthermore, integration of this knowledge into quality improvement initiatives should be entertained in an effort to improve outcomes.

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.

Differences in predicting glucose absorption from peritoneal dialysate compared to measured absorption in peritoneal dialysis patients treated by continuous ambulatory peritoneal dialysis and ambulatory peritoneal dialysis cyclers

Background and aims:

Glucose-containing peritoneal dialysates are used to generate an osmotic gradient for the convective removal of water and sodium. Predictive equations were developed to estimate glucose absorption without having to formally measure changes in dialysate glucose. In view of the changes in peritoneal dialysis prescriptions over time, we compared predicted and measured glucose absorption.

Subjects/methods:

We measured peritoneal glucose losses when peritoneal dialysis patients attended their first assessment of peritoneal membrane function, and compared this to glucose exposure and Kidney Disease Outcomes Quality Initiative, Grodstein and Bodnar predictive equations.

Results:

We studied 689 patients; 329 (56.9%) males, 53 (37.1%) diabetics, with mean age 57.1 ± 16.2 years, with 186 treated by automated peritoneal dialysis cyclers and 377 by automated peritoneal dialysis with a daytime icodextrin exchange and 126 by continuous ambulatory peritoneal dialysis. Using Bland -Altman analysis, all equations demonstrated systematic bias overestimating glucose absorption with increasing glucose absorption. For continuous ambulatory peritoneal dialysis patients, the Kidney Disease Outcomes Quality Initiative formula underestimated glucose absorption (bias 188 (−39 to 437) mmol/day, as did Grodstein (bias 37.9 (−105 to 29) mmol/day, whereas mean bias for Bodnar was −29 (−130 to 180)). There was systematic overestimation for all equations for both automated peritoneal dialysis with and without a daytime exchange, with increasing bias with greater glucose absorption.

Conclusion:

Although formally measuring peritoneal glucose absorption is time consuming and requires patient co-operation, current predictive equations overestimate glucose absorption and do not provide accurate estimations of glucose absorption particularly for automated peritoneal dialysis patients.

Volume management as a key dimension of a high-quality PD prescription

BACKGROUND

Appropriate volume control is one of the key goals in a peritoneal dialysis (PD) prescription. As such it is an important component of the International Society of Peritoneal Dialysis (ISPD) guideline for "High-quality PD prescription" necessitating a review of the literature on volume management. The workgroup recognized the importance of including within its scope measures of volume status and blood pressure in prescribing high-quality PD therapy.

METHODS

A Medline and PubMed search for publications addressing volume status and its management in PD since the publication of the 2015 ISPD Adult Cardiovascular and Metabolic Guidelines, from October 2014 through to July 2019, was conducted.

RESULTS

There were no randomized controlled trials on blood pressure intervention and six randomized trials of bioimpedance-guided volume management. Generally, all studies were of small sample size, short duration, and used surrogate markers as primary outcomes. As a consequence, only "practice points" were drawn. High-quality goal-directed PD prescription should aim to achieve and maintain clinical euvolemia taking residual kidney function and its preservation into account, so that both fluid removal from peritoneal ultrafiltration and urine output are considered and residual kidney function is not compromised. Blood pressure should be included as a key objective parameter in assessing the quality of PD prescription but there is currently no evidence for a specific target in PD. Clinical examination remains the keystone of routine clinical care.

CONCLUSIONS

High-quality goal-directed PD prescription should include volume management as one of the key dimensions.

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.

Sodium loss, extracellular volume overload and hypertension in peritoneal dialysis patients treated by automated peritoneal dialysis cyclers

INTRODUCTION

Achieving sodium balance is important for peritoneal dialysis patients, as sodium excess may lead to hypertension and extracellular water expansion. We wished to determine whether greater sodium removal had adverse consequences.

METHODS

We calculated 24-h urinary and peritoneal sodium losses in peritoneal dialysis patients treated by automated cyclers, when attending for peritoneal membrane and bioimpedance assessments.

RESULTS

We reviewed 439 peritoneal dialysis patients, 56.7% male, average age 54.6 years, median sodium loss 110 (68-155) mmol/day. Sodium loss was strongly associated with urine volume, r = 0.37, protein nitrogen appearance rate, r = 0.29, and body cell mass, r = 0.21, all p < 0.001. We found no association with blood pressure or anti-hypertensive medication prescription, or extracellular water. On multivariable logistic regression analysis, sodium loss was associated with greater urine output, odds ratio 1.001, 95% confidence interval 1.00-1.001, p < 0.001, and protein nitrogen appearance (odds ratio 1.023, confidence interval 1.006-1.04), p = 0.008. Adjusting for body weight, sodium loss was associated with urine output (odds ratio 1.001, confidence interval 1.001-1.002, p < 0.001), and negatively with body fat index (odds ratio 0.96, confidence interval 0.93-0.99, p = 0.008) and co-morbidity grade (odds ratio 0.58, confidence interval 0.36-0.39, p = 0.023).

CONCLUSION

Heavier peritoneal dialysis patients with greater estimated dietary protein intake (protein nitrogen appearance), those with greater residual renal function and peritoneal clearances, along with lower co-morbidity, had greater daily sodium losses. Adjusting for body weight, then sodium losses were greater with higher daily urine output, and lower in patients with proportionately more body fat and co-morbidity. Sodium losses would appear to primarily determined by body size and not associated with hypertension or extracellular water expansion.

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.

Bioimpedance-defined overhydration predicts survival in end stage kidney failure (ESKF): systematic review and subgroup meta-analysis

Both overhydration and comorbidity predict mortality in end-stage kidney failure (ESKF) but it is not clear whether these are independent of one another. We undertook a systematic review of studies reporting outcomes in adult dialysis patients in which comorbidity and overhydration, quantified by whole body bioimpedance (BI), were reported. PubMed, EMBASE, PsychInfo and the Cochrane trial database were searched (1990-2017). Independent reviewers appraised studies including methodological quality (assessed using QUIPS). Primary outcome was mortality, with secondary outcomes including hospitalisation and cardiovascular events. Of 4028 citations identified, 46 matched inclusion criteria (42 cohorts; 60790 patients; 8187 deaths; 95% haemodialysis/5% peritoneal dialysis). BI measures included phase angle/BI vector (41%), overhydration index (39%) and extra:intracellular water ratio (20%). 38 of 42 cohorts had multivariable survival analyses (MVSA) adjusting for age (92%), gender (66%), diabetes (63%), albumin (58%), inflammation (CRP/IL6-37%), non-BI nutritional markers (24%) and echocardiographic data (8%). BI-defined overhydration (BI-OH) independently predicted mortality in 32 observational cohorts. Meta-analysis revealed overhydration >15% (HR 2.28, 95% CI 1.56-3.34, P < 0.001) and a 1-degree decrease in phase angle (HR 1.74, 95% CI 1.37-2.21, P < 0.001) predicted mortality. BI-OH predicts mortality in dialysis patients independent of the influence of comorbidity.

Peritoneal Protein Losses Depend on More Than Just Peritoneal Dialysis Modality and Peritoneal Membrane Transporter Status

Peritoneal protein clearance (PPCl) depends upon vascular supply and size selective permeability. Some previous reports suggested PPCl can distinguish fast peritoneal membrane transport due to local or systemic inflammation. However, as studies have been discordant, we wished to determine factors associated with an increased PPCl. Consecutive patients starting peritoneal dialysis (PD) who were peritonitis-free were studied. Data included a baseline peritoneal equilibration test (PET), measurement of dialysis adequacy, 24-h dialysate PPCl and body composition measured by multifrequency bioimpedance. 411 patients, mean age 57.2 ± 16.6 years, 60.8% male, 39.4% diabetic, 20.2% treated by continuous ambulatory peritoneal dialysis (CAPD) were studied. Mean PET 4-h Dialysate/Serum creatinine was 0.73 ± 0.13, with daily peritoneal protein loss 4.6 (3.3-6.4) g, and median PPCl 69.6 (49.1-99.6) mL/day. On multivariate analysis, PPCl was most strongly associated with CAPD (β 0.25, P < 0.001), extracellular water (ECW)/total body water (TBW) ratio (β 0.21, P < 0.001), skeletal muscle mass index (β 0.21, P < 0.001), log N-terminal brain natriuretic peptide (NT-proBNP) (β 0.17, P = 0.001), faster PET transport (β 0.15, P = 0.005), and normalized nitrogen appearance rate (β 0.13, P = 0.008). In addition to the longer dwell times of CAPD, greater peritoneal creatinine clearance and faster PET transporter status, we observed an association between increased PPCl and ECW expansion, increased NT-proBNP, estimated dietary protein intake and muscle mass, suggesting a link to sodium intake and sodium balance, increasing both ECW and conduit artery hydrostatic pressure resulting in greater vascular protein permeability. This latter association may explain reports linking PPCl to patient mortality.

Impact of Diabetes on Extracellular Volume Status in Patients Initiating Peritoneal Dialysis

BACKGROUND

Recent reports have highlighted that diabetic patients with kidney failure are at increased risk of technique failure and transfer to haemodialysis within 90 days of initiating peritoneal dialysis (PD). We wished to determine whether there were differences between diabetic and non-diabetic patients within the first 3 months of starting PD.

METHODS

We reviewed results of corresponding bioimpedance and the 1st test of peritoneal membrane function (PET) in consecutive patients, 6-10 weeks after initiating PD electively.

RESULTS

Adult patients numbering 386 - 230 males (59.6%), 152 (39.4%) diabetic, 188 (48.7%) white, mean age 57.3 ±16.9 years - were studied. Although weight, residual renal function and peritoneal clearances were not different, diabetic patients had greater extracellular water to total body water (ECW/TBW; 40.4 ± 1.1 vs. 39.2 ± 1.4) and % ECW excess (9.6 [6.3-12.3] vs. 4.9 [0.7-8.9]), lower serum albumin (35.2 ± 4.7 vs. 37.8 ± 4.9 g/L), greater fat mass index (9.5 ± 4.2 vs. 7.7 ± 4.2), and although mean arterial blood pressure was similar, arterial pulse pressure was greater (66.9 ± 10.8 vs. 54.3 ± 17.3 mm Hg, all p < 0.001). On multivariate analysis, glycated haemoglobin was associated with pulse pressure (standardised β 0.24, p < 0.001), N terminal brain natriuretic peptide (β 0.24, p < 0.001), ECW/TBW (β 0.19, p = 0.012) and negatively with serum albumin (β -0.14, p = 0.033) and creatinine (β -0.18, p = 0.02).

CONCLUSION

Diabetic patients electively starting PD were found to have greater ECW/TBW ratios and ECW excess 6-10 weeks after starting PD compared to non-diabetics, despite similar PET. Increased ECW could predispose diabetic patients to be at greater risk of volume overload.

Does Peritoneal Protein Transport Increase with Peritoneal Dialysis Therapy Duration and Lead to Extracellular Water Overload in Peritoneal Dialysis Patients?

Faster peritoneal transport status has been associated with adverse outcomes for peritoneal dialysis (PD) patients. Peritoneal protein clearance, through large pores, may be a surrogate marker of local inflammation. We wished to determine whether peritoneal protein transport increased with PD duration or was associated with extracellular water (ECW) expansion. We studied the relationships between 4 h Dialysate (D)/Serum (S) protein and ECW excess, using multifrequency bioelectrical impedance assessments, in 103 PD patients with up to 4 years of prospectively collected peritoneal equilibrium test (PET) results. 4 h PET D/S total protein and creatinine ratios were stable over time (K-W test, P = 0.063 and P = 0.3357, respectively). The initial PET 4 h D/S creatinine and D/S total protein correlated with ECW excess (r = 0.33, P = 0.003, and r = 0.27, P = 0.019, respectively), but thereafter there was no association. CRP and albumin did not correlate with 4 h D/S creatinine or total protein. Serial 4 h D/S total protein and 4 h D/S creatinine correlated all time points (P < 0.001). At the start of PD therapy, over-hydration (ECW excess) was observed with higher 4 h D/S creatinine and 4 h D/S total protein ratios, suggesting initial exposure to PD fluids causes faster transport. Thereafter changes in peritoneal creatinine and total protein transport mirrored each other suggesting that similar factors lead to changes in both small and large pore transport, and there was no sustained increase in larger pore transport with therapy time.