Therapeutic Options for Preservation of Residual Renal Function in Patients on Peritoneal Dialysis

Dialysis is not the ideal renal replacement therapy because it does not fully restore all kidney functions. Increasing evidence suggests that preservation of residual renal function is associated with a survival benefit, a decrease in morbidity, better nutrition, a lower level of inflammatory markers, an improved quality of life, and cost savings by obviating the need for more peritoneal dialysis exchanges and possibly by reducing the requirement for antihypertensive agents, phosphate binders, and erythropoietin. In the present article, we review the impact of residual renal function on patient outcomes and the renoprotective strategies available in patients on peritoneal dialysis.

Maximizing the Success of Peritoneal Dialysis in High Transporters

This article reviews the current understanding of high transport status in the peritoneal dialysis population and emphasizes survival can be improved for high transporters. To address the current state of knowledge on high peritoneal membrane transport, the negative impact of an increased peritoneal solute transport rate is first discussed. The potential downside of high transport status, notably on survival outcomes (as supported by registry data and meta-analysis), is highlighted. Based on recent advances and clinical studies, ways of maximizing the success of peritoneal dialysis treatment in high transporters are discussed, and management strategies are proposed.

Controlling Inflammation in Peritoneal Dialysis: The Role of PD-Related Factors as Potential Intervention Targets

Cardiovascular (CV) disease is the main cause of death in peritoneal dialysis (PD) patients, but the mechanisms mediating the increased CV risk observed in this group of patients are still largely unknown, which limits the perspective on effective therapeutic strategies. Patients on PD are already exposed to a number of traditional risk factors from the start of their chronic kidney disease (CKD), because many of those risk factors are common to CV disease and CKD alike. As renal dysfunction progresses, CKD-related risk factors are introduced, changing the profile of both the CV disease and the markers of risk. In this phase, which usually starts when glomerular filtration rate falls below 60 mL/min, the list of risk factors is expanded to include disturbances of mineral metabolism, anemia, fluid overload, uremic toxicity, and increased signs of oxidative stress and inflammation. Although many of the risk factors linked to CV burden are not related to the dialytic procedure, additional harm is introduced after the initiation of PD—with, for example, the presence of chronic infections and factors related to PD fluids, particularly reabsorption of glucose. In the present article, we review the impact of the novel risk factors introduced with the initiation of PD therapy, and we propose potential therapeutic strategies (which remain to be tested) for reducing CV mortality in this group of patients.

Inflammation in Peritoneal Dialysis: A Latin-American Perspective

Peritoneal dialysis (PD) patients present an extremely high mortality rate, but the mechanisms mediating the increased risk of mortality observed in this group of patients are still largely unknown, which limits the perspective of effective therapeutic strategies. The leading hypothesis that tries to explain this high mortality risk is that PD patients are exposed to a number of traditional risk factors for cardiovascular disease (CVD) already at the onset of their chronic kidney disease (CKD), since many of these risk factors are common to both CVD and CKD. Of particular importance, chronic inflammation recently emerged as an important novel risk factor related to multiple complications of CKD. There are many stimuli of the inflammatory response in CKD patients, such as fluid overload, decreased cytokine clearance, presence of uremia-modified proteins, presence of chronic infections, metabolic disturbances (including hyperglycemia), obesity. Many of these factors are related to PD. Latin America has made some progress in economic issues; however, a large portion of the population is still living in poverty, in poor sanitary conditions, and with many health-related issues, such as an increasing elderly population, low birth weights, and increasingly high energy intake in the adult population, which, in combination with changes in lifestyle, has provoked an increase in the prevalence of obesity, diabetes, and CVD. Therefore, in Latin America, there seems to be a peculiar situation combining high prevalence of low education level, poor sanitary conditions, and poverty with increases in obesity, diabetes, and sedentary lifestyle. Since inflammation and mortality risk are intimately related to both sides of those health issues, in this review we aim to analyze the peculiarities of inflammation and mortality risk in the Latin-American 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.

Current Challenges and Opportunities in PD

Despite the gradual increased use of peritoneal dialysis (PD) globally around the world, it is recognized that a number of areas in PD as a renal-replacement therapy require attention and improvements. The current challenges in PD include how to tackle technique failure and sustain long-term PD, manage and prevent peritoneal infections, malnutrition and inflammation, cardiovascular mortality, volume overload, glucose exposure, adequacy of solute removal, peritoneal access, peritoneal physiology and changes with long-term PD, patient fatigue, psychosocial issues, and care of elderly patients on PD. Obviously, hemodialysis as another renal-replacement therapy modality also has its own areas that need attention and improvement by nephrologists and nurses. With more clinical and basic science research, outcome studies, and through better education and training, together with the implementation of global PD guidelines for enhancing care of PD patients, it is likely that such problem areas in PD gradually will be resolved and PD patient outcomes will be improved.

Inflammation and Peritoneal Dialysis

Inflammation is one of the well-recognized nontraditional risk factors that contributes to the excessive cardiovascular mortality in peritoneal dialysis (PD) patients. Serum C-reactive protein and interleukin-6 levels are common surrogate markers used to measure inflammatory burden and predict adverse clinical outcomes in PD patients. Causes of inflammation are complex and can be categorized into factors related to a decrease in renal function and factors related to dialysis. They interact with each other and finally result in systemic and intraperitoneal inflammation. This review discusses the various causes and clinical implications of inflammation in PD patients. More importantly, potential therapeutic options that target the underlying pathogenic mechanisms are explored.

Coronary Artery Calcification Score as A Predictor of All-Cause Mortality and Cardiovascular Outcome in Peritoneal Dialysis Patients

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BACKGROUND

This study aimed to examine whether the coronary artery calcification score (CaCS) was associated with the prognosis of peritoneal dialysis (PD) patients. ♦

METHODS

Adult PD patients who were clinically stable for at least 2 months were recruited for this prospective, observational cohort study. Coronary artery calcification was assessed using multislice spiral computed tomography and was recorded according to the Agatston score. The endpoints including all-cause mortality, cardiovascular events, and cardiovascular mortality were assessed. Multivariate Cox regression was used to identify independent predictors of all-cause mortality, cardiovascular events (CVEs), and cardiovascular mortality. ♦

RESULTS

A total of 179 PD patients (86 men) with a mean age of 63.5 ± 14.8 years were recruited for this study. Coronary artery calcification scores ranging from 0 to 5,257 were stratified as follows: no (CaCS = 0, n = 54), low (0 < CaCS < 400, n = 72), and high (CaCS ≥ 400, n = 53) calcification. The follow-up duration was 30.6 ± 16.2 (24-63) months. Compared with the no calcification group, patients with a higher CaCS were older and had lower diastolic blood pressure, residual renal function, and serum albumin, and higher HbA1C and serum insulin. Multivariate Cox regression revealed that the CaCS was an independent predictor for all the 3 endpoints after adjustment in PD patients. ♦

CONCLUSIONS

CaCS was an independent predictor of all-cause mortality, cardiovascular events, and cardiovascular mortality in patients receiving peritoneal dialysis.

Euvolemia in hemodialysis patients: a potentially dangerous goal?

Dialysis patients have high mortality rate and the leading cause of death is cardiovascular disease. Uremic cardiomyopathy differs from that due to conventional atherosclerosis, where cardiovascular changes result in ineffective circulation and lead to tissue ischemia. Modern dialysis has significant limitations with fluid management probably the most challenging. Current evidence suggests that both volume overload and aggressive fluid removal can induce circulatory stress and multi-organ injury. Furthermore, we do not have accurate volume assessment tools. As a result, targeting euvolemia might result in more harm than benefit with conventional hemodialysis therapy. Therefore, it might be time to consider a degree of permissive over-hydration until we have better tools to both determine ideal weight and improve current renal replacement therapy so that the process of achieving it is not so fraught with the current dangers.

High-sensitivity C-reactive protein predicts mortality and technique failure in peritoneal dialysis patients

Introduction

An elevated level of serum C-reactive protein (CRP) is widely considered an indicator of an underlying inflammatory disease and a long-term prognostic predictor for dialysis patients. This cross-sectional cohort study was designed to assess the correlation between the level of high-sensitivity CRP (HS-CRP) and the outcome of peritoneal dialysis (PD) patients.

Methods

A total of 402 patients were stratified into 3 tertiles (lower, middle, upper) according to serum HS-CRP level and and followed up from October 2009 to September 2011. During follow-up, cardiovascular events, infection episodes, technique failure, and mortality rate were recorded.

Results

During the 24-month follow-up, 119 of 402 patients (29.6%) dropped out from PD, including 28 patients (7.0%) who died, 81 patients (20.1%) who switched to hemodialysis, and 10 patients (2.5%) who underwent kidney transplantation. The results of Kaplan–Meier analysis and log-rank test demonstrated a significant difference in the cumulative patient survival rate across the 3 tertiles (the lowest rate in upper tertile). On multivariate Cox regression analysis, only higher HS-CRP level, older age, the presence of diabetes mellitus (DM), lower serum albumin level, and the occurrence of cardiovascular events during follow-up were identified as independent predictors of mortality. Every 1 mg/L increase in HS-CRP level was independently predictive of a 1.4% increase in mortality. Multivariate Cox regression analysis also showed that higher HS-CRP level, the presence of DM, lower hemoglobin level, lower serum albumin level, higher dialysate/plasma creatinine ratio, and the occurrence of infective episodes and cardiovascular events during follow-up were independent predictors of technique failure.

Conclusions

The present study shows the importance of HS-CRP in the prediction of 2-year mortality and technique survival in PD patients independent of age, diabetes, hypoalbuminemia, and the occurrence of cardiovascular events.

Bioimpedance spectroscopy for the detection of fluid overload in Chinese peritoneal dialysis patients

BACKGROUND

Fluid overload probably contributes to the cardiovascular risk of peritoneal dialysis (PD) patients. We studied the relationship between over-hydration as determined by bioimpedance spectroscopy and dialysis adequacy, nutritional status, and arterial stiffness in Chinese PD patients.

METHODS

We studied 122 asymptomatic prevalent PD patients: bioimpedance spectroscopy, arterial pulse wave velocity, dialysis adequacy and nutritional status were determined.

RESULTS

Of the 122 patients, 88 (72.1%) had over-hydration of ≥ 1 L, while 25 (20.5%) were ≥ 5 L. Over-hydration significantly correlated with total body water (r = 0.474, p < 0.001) and extracellular water (r = 0.755, p < 0.001). Over-hydration was more severe in male and diabetic patients, and significantly correlated with Charlson's comorbidity score, blood pressure, body mass index, body weight, peritoneal transport characteristics, and carotid-femoral pulse wave velocity. Over-hydration significantly correlated with Kt/V (r = -0.287, p = 0.016), serum albumin level (r = -0.465, p < 0.001) and malnutrition inflammation score (r = 0.410, p = 0.006), but not residual renal function.

CONCLUSION

Over-hydration is common in asymptomatic Chinese PD patients. The degree of over-hydration is particularly pronounced in patients who are inadequately dialyzed, have multiple comorbid conditions and low serum albumin levels. Over-hydration is associated with high blood pressure and arterial stiffness, and may contribute to the excessive risk of cardiovascular disease in this group of patients.

Randomized, controlled trial of glucose-sparing peritoneal dialysis in diabetic patients

Glucose-containing peritoneal dialysis solutions may exacerbate metabolic abnormalities and increase cardiovascular risk in diabetic patients. Here, we examined whether a low-glucose regimen improves metabolic control in diabetic patients undergoing peritoneal dialysis. Eligible patients were randomly assigned in a 1:1 manner to the control group (dextrose solutions only) or to the low-glucose intervention group (IMPENDIA trial: combination of dextrose-based solution, icodextrin and amino acids; EDEN trial: a different dextrose-based solution, icodextrin and amino acids) and followed for 6 months. Combining both studies, 251 patients were allocated to control (n=127) or intervention (n=124) across 11 countries. The primary endpoint was change in glycated hemoglobin from baseline. Mean glycated hemoglobin at baseline was similar in both groups. In the intention-to-treat population, the mean glycated hemoglobin profile improved in the intervention group but remained unchanged in the control group (0.5% difference between groups; 95% confidence interval, 0.1% to 0.8%; P=0.006). Serum triglyceride, very-low-density lipoprotein, and apolipoprotein B levels also improved in the intervention group. Deaths and serious adverse events, including several related to extracellular fluid volume expansion, increased in the intervention group, however. These data suggest that a low-glucose dialysis regimen improves metabolic indices in diabetic patients receiving peritoneal dialysis but may be associated with an increased risk of extracellular fluid volume expansion. Thus, use of glucose-sparing regimens in peritoneal dialysis patients should be accompanied by close monitoring of fluid volume status.

Prevalence and progression of cardiovascular calcifications in peritoneal dialysis patients: A prospective study

BACKGROUND

Patients on dialysis may have abnormal serum levels of Ca, P and parathyroid hormone, with related bone diseases. This population has an increased risk of death, with cardiovascular calcification (CC) a contributing factor. Patients on peritoneal dialysis appear to be at increased risk of hyperlipidemia, a contributing factor to atherosclerotic plaque formation. Although several studies have described the presence and progression of CC in hemodialysis populations, there are fewer data in patients on peritoneal dialysis.

STUDY DESIGN

The Renal Osteodystrophy and Calcifications: Key factors in Peritoneal Dialysis (ROCK-PD) study was a 36-month, prospective observational study conducted in Italy. The study examined the presence and progression of CC in two cardiac valves and five arterial sites. The potential associations of serum Ca and P with mortality and cardiovascular morbidity, demographic, clinical and blood chemistry variables was investigated.

RESULTS

CC was present in 77% of patients at baseline (N=369) and in 90% of patients by study end (N=145), progressing in 73% of patients. There were 42 deaths (11%). Analyses showed a marked correlation between baseline P levels and the presence of left ventricular hypertrophy. However, there were no consistent correlations between serum Ca or P with mortality or morbidity.

CONCLUSIONS

CC was common in peritoneal dialysis patients and progressed in a majority of patients.

Relationship between CRP polymorphism and cardiovascular events in Chinese peritoneal dialysis patients

BACKGROUND AND OBJECTIVES

The single-nucleotide polymorphism (SNP) -717A→G substitution, rs2794521, was found in the promoter of the C-reactive protein (CRP) gene. Functional studies showed that A allele promoter has higher transcriptional activity than the G allele. This study investigated the association between this SNP and the outcome of Chinese patients undergoing peritoneal dialysis (PD).

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The study included 441 new PD patients (232 men; mean age ± SD, 56.7±13.5 years). CRP genotyping was determined; patients were followed for 41.3±18.3 months for cardiovascular events.

RESULTS

For the entire cohort, 5-year event-free survival rates did not differ between the AA and AG/GG groups (35.7% and 31.9%, respectively; P=0.64). However, there was significant interaction between plasma cholesterol levels and CRP genotype groups on event-free survival (P=0.04 for interaction). For patients with cholesterol levels of 200 mg/dl or greater, the 5-year event-free survival rate in the AG/GG group was significantly better than that in the AA group (54.7% versus 40.0%; P=0.04), whereas there was no difference in event-free survival between genotype groups for patients with cholesterol levels less than 200 mg/dl.

CONCLUSIONS

CRP gene -717AG or GG genotypes is associated with cardiovascular benefit to Chinese PD patients with cholesterol levels of 200 mg/dl or greater. These findings suggest a complex interaction among cholesterol, CRP, and cardiovascular disease in PD patients.

Treatment of Metabolic Syndrome in Peritoneal Dialysis Patients

Metabolic syndrome (MetS) occurs in about 50% of peritoneal dialysis (PD) patients. It encompasses a cluster of major risk factors for cardiovascular diseases. A modified National Cholesterol Education Program Third Adult Treatment Panel guideline for the diagnosis of MetS in PD patients has been proposed. Preliminary data suggest that PD patients with MetS in our cohort have an increased risk of cardiovascular mortality. The proinflammatory effects of adipose tissue are one of the reasons for poor outcome in obese PD patients. Lifestyle modification, including appropriate dietary restriction and exercise, especially reduction of fat mass in obese patients, has been one of the major areas proposed for managing patients with MetS. Individual therapeutic trials are treating hyperglycemia, hypertension, and dyslipidemia in dialysis patients. Evidence in PD patients that interventions targeting MetS can improve outcomes is still lacking. Large-scale studies with data on the clinical outcome for MetS intervention in PD patients are needed.

Metabolic syndrome in peritoneal dialysis patients

Cardiovascular morbidity and mortality are common in peritoneal dialysis patients. Metabolic syndrome (MES) is a medical condition with a clustering of major risk factors for cardiovascular diseases. In this review article, the various diagnostic criteria used in MES are discussed. It is proposed to use a modified National Cholesterol Education Programme Adult Treatment Panel III (NCEP ATP III) criteria for the diagnosis of MES in peritoneal dialysis (PD) patients taking into consideration the scientific evidence and practicality. When three or more of the following criteria are satisfied in PD patients, obesity, high triglyceride, low high-density lipoprotein cholesterol (HDL-C), hypertension or dysglycaemia, they are diagnosed as having MES. Body mass index (BMI) with reference to ethnicity is suggested to replace waist circumference for diagnosing obesity. Epidemiology and outcome of PD patients with MES are highlighted. The adverse sequelae of obesity appear to be primarily due to fat mass rather than non-fat mass, possibly related to the pro-inflammatory effect of adipose tissue. Whilst there are therapies to tackle MES in PD patients, more conclusive data in human studies to see clinically improved outcomes with such strategies are needed.

Impact of Early Nephrology Referral on Mortality and Hospitalization in Peritoneal Dialysis Patients

Objectives

Several studies have examined the possible association between late referral to a nephrologist and mortality on maintenance hemodialysis. However, we lack information on the benefit of early nephrologist referral in patients receiving peritoneal dialysis (PD).

Patients and Methods

In an inception cohort of 102 consecutive PD patients identified in a single center between 2003 and 2004, we sought to determine whether late nephrologist referral was associated with poor outcomes. The primary end point was all-cause mortality. The effects of early referral to a multidisciplinary low clearance clinic on cardiovascular mortality and length of hospitalization were also evaluated.

Results

Of 102 incident PD patients, 61 subjects (59.8%) were referred early to the nephrologist (more than 3 months) before dialysis initiation. During the study period of 284.9 patient-years (median follow-up period 36.8 months), 25 patients died, 12 due to cardiovascular causes. Both cardiovascular and all-cause mortality were significantly increased among PD patients with late referral, but the relationship between late referral and all-cause mortality was mitigated substantially by adjusting for relevant factors. In univariate analysis, late nephrology referral was associated with increased cardiovascular mortality, with a hazard ratio of 5.43 (95% confidence interval 1.46 – 20.21, p = 0.012). Annual adjusted days of hospitalization were similar between the early and late nephrology referral groups.

Conclusions

A comprehensive analysis of incident PD subjects confirmed the significant relationship between late nephrology referral and all-cause and cardiovascular mortality. A causal relationship remains to be established and validated.