Oral sodium bicarbonate for the treatment of metabolic acidosis in peritoneal dialysis patients: a randomized placebo-control trial

Association Between the Dialysate Bicarbonate and the Pre-dialysis Serum Bicarbonate Concentration in Maintenance Hemodialysis: A Retrospective Cohort Study

Background

It is unclear whether the use of higher dialysate bicarbonate concentrations is associated with clinically relevant changes in the pre-dialysis serum bicarbonate concentration.

Objective

The objective is to examine the association between the dialysate bicarbonate prescription and the pre-dialysis serum bicarbonate concentration.

Design

This is a retrospective cohort study.

Setting

The study was performed using linked administrative health care databases in Ontario, Canada.

Patients

Prevalent adults receiving maintenance in-center hemodialysis as of April 1, 2020 (n = 5414) were included.

Measurements

Patients were grouped into the following dialysate bicarbonate categories at the dialysis center-level: individualized (adjustment based on pre-dialysis serum bicarbonate concentration) or standardized (>90% of patients received the same dialysate bicarbonate concentration). The standardized category was stratified by concentration: 35, 36 to 37, and ≥38 mmol/L. The primary outcome was the mean outpatient pre-dialysis serum bicarbonate concentration at the patient level.

Methods

We examined the association between dialysate bicarbonate category and pre-dialysis serum bicarbonate using an adjusted linear mixed model.

Results

All dialysate bicarbonate categories had a mean pre-dialysis serum bicarbonate concentration within the normal range. In the individualized category, 91% achieved a pre-dialysis serum bicarbonate ≥22 mmol/L, compared to 87% in the standardized category. Patients in the standardized category tended to have a serum bicarbonate that was 0.25 (95% confidence interval [CI] = -0.93, 0.43) mmol/L lower than patients in the individualized category. Relative to patients in the 35 mmol/L category, patients in the 36 to 37 and ≥38 mmol/L categories tended to have a serum bicarbonate that was 0.70 (95% CI = -0.30, 1.70) mmol/L and 0.87 (95% CI = 0.14, 1.60) mmol/L higher, respectively. There was no effect modification by age, sex, or history of chronic lung disease.

Limitations

We could not directly confirm that all laboratory measurements were pre-dialysis. Data on prescribed dialysate bicarbonate concentrations for individual dialysis sessions were not available, which may have led to some misclassification, and adherence to a practice of individualization could not be measured. Residual confounding is possible.

Conclusions

We found no significant difference in the pre-dialysis serum bicarbonate concentration irrespective of whether an individualized or standardized dialysate bicarbonate was used. Dialysate bicarbonate concentrations ≥38 mmol/L (vs 35 mmol/L) may increase the pre-dialysis serum bicarbonate concentration by 0.9 mmol/L.

Gut permeability, circulating bacterial fragments and measures of congestion in peritoneal dialysis

Background

Limited data exist on the association between gut permeability, circulating bacterial fragment and volume overload in peritoneal dialysis (PD) patients. We measured circulating bacterial fragments, N-terminal pro B-type natriuretic peptide (NT-proBNP), calprotectin and zonulin levels, and evaluate their association with the clinical outcomes in PD patients.

Methods

This was a single-center prospective study on 108 consecutive incident PD patients. Plasma endotoxin and bacterial DNA, and serum NT-proBNP, calprotectin and zonulin levels were measured. Primary outcomes were technique and patient survival, secondary outcomes were hospitalization data.

Results

There was no significant correlation between plasma endotoxin and bacterial DNA, and serum NT-proBNP, calprotectin and zonulin levels. The Homeostatic Model Assessment for Insulin Resistance (HOMA)-2β index, which represents insulin resistance, positively correlated with plasma bacterial DNA (r = 0.421, P < .001) and calprotectin levels (r = 0.362, P = .003), while serum NT-proBNP level correlated with the severity of volume overload and residual renal function. Serum NT-proBNP level was associated with technique survival even after adjusting for confounding factors [adjusted hazard ratio (aHR) 1.030, 95% confidence interval 1.009-1.051]. NT-proBNP level was also associated with patient survival by univariate analysis, but the association became insignificant after adjusting for confounding factors (aHR 1.010, P = .073). Similarly, NT-proBNP correlated with the number of hospitalizations and duration of hospitalization by univariate analysis, but the association became insignificant after adjusting for confounding factors.

Conclusion

There was no correlation between markers of gut permeability, circulating bacterial fragments and measures of congestion in PD patients. Bacterial fragments levels and gut permeability are both associated with insulin resistance. Serum NT-proBNP level is associated with the severity of volume overload and technique survival. Further studies are required to delineate the mechanism of high circulating bacterial fragment levels in PD patients.

Nutrition in Peritoneal Dialysis

The use of peritoneal dialysis (PD) has been associated with improved quality of life, cost-effectiveness, and better outcomes for patients with kidney failure. However, many patients utilizing PD for replacement therapy face numerous nutritional hurdles. As the use of PD continues to increase worldwide, malnutrition has become an increasingly recognized concern for patients undergoing PD. The nephrology community needs to recognize and treat malnutrition to promote optimal nutritional states for our patients. In this review, we discuss several factors that contribute to malnutrition and protein-energy wasting and explore the benefits and limitations of nutritional parameters used to assess protein-calorie malnutrition. We also emphasize updated guidelines on daily caloric, protein, and micronutrient recommendations, as well as their effects on electrolyte homeostasis.

Effects of Oral Sodium Bicarbonate Supplementation on Protein Metabolism and Inflammation in Iraqi Hemodialysis Patients: An Open-Label Randomized Controlled Trial

Background

The effect of correcting metabolic acidosis on protein metabolism in hemodialysis patients is controversial.

Objectives

To study the effects of oral sodium bicarbonate on protein metabolism and markers of inflammation in acidotic hemodialysis patients. Patients and Methods. An open-label randomized controlled trial was conducted at a single center. Sixty-six clinically stable adult hemodialysis patients were recruited with an average predialysis serum bicarbonate level of <22 mmol/l and a dialysate bicarbonate concentration of 35 mmol/l. Forty-nine participants have completed the study. Oral sodium bicarbonate tablets of 500 mg were given daily in the intervention group (n = 25) for 12 weeks versus the standard of care in the control group (n = 24). Outcomes compared intervention versus nonintervention in both groups at equivalent time points (0 and 3 months). The clinical data, anthropometry, dialysis adequacy, albumin, normalized protein catabolism rate, blood gas analysis, and bicarbonate were recorded at 0 and 3 months. In addition, muscle mass and handgrip strength were measured. Finally, IL-6 as a marker of inflammation was measured at randomization and three months.

Results

Serum bicarbonate and pH increased significantly from 17.57 ± 3.34 mmol/L to 20.69 ± 2.54 mmol/L and from 7.26 ± 0.06 to 7.34 ± 0.04, respectively (p < 0.0001). Serum albumin was significantly higher in the intervention group at three months than in the control group, 4.11 ± 0.45 vs. 3.79 ± 0.47 (p value 0.011). Serum potassium significantly decreased in the intervention group at three months compared to the control group, 5.00 ± 0.43 mEq/l vs. 5.33 ± 0.63 mEq/l (p value 0.03). Muscle strength expressed as handgrip has improved significantly in the intervention group at three months compared to the control group, 45.01 ± 19.19 vs. 33.93 ± 15.06 (p value 0.03). The IL-6 values were less in the intervention group at 3 months with a p value of 0.01. The interdialytic weight of the intervention group at three months was 2.42 ± 0.64 compared to the 2.20 ± 1.14 control group, but this did not reach statistical significance (p value of 0.4). The composite of (albumin + nPCR) at three months was achieved in 59.18% of the intervention group compared to 14.28% with a p value of 0.01.

Conclusions

Correcting metabolic acidosis in hemodialysis patients improved serum albumin and nPCR without hypokalemia or significant interdialytic weight gain. This was particularly evident in patients with minimal inflammation with low IL-6 values.

Plasma vaspin levels and clinical outcome in incident peritoneal dialysis patients

BACKGROUND

Vaspin is an adipokine that regulates glucose and lipid metabolism. Plasma vaspin level is increased in chronic kidney disease but decreased in hemodialysis patients. However, plasma vaspin level in peritoneal dialysis (PD) patients, as well as its prognostic role, has not been studied.

METHODS

We recruited 146 incident PD patients. Their baseline plasma vaspin levels, body anthropometry, the profile of insulin resistance, bioimpedance spectroscopy parameters, dialysis adequacy, and nutritional indices were measured. They were followed for up to 5 years for survival analysis.

RESULTS

The average age was 58.4 ± 11.8 years; 96 patients (65.8%) were men, and 90 (61.6%) had diabetes. The median vaspin level was 0.18 ng/dL (interquartile range [IQR] 0.11 to 0.30 ng/dL). Plasma vaspin level did not have a significant correlation with adipose tissue mass or baseline insulin level. However, plasma vaspin level had a modest correlation with the change in insulin resistance, as represented by the HOMA-IR index, in non-diabetic patients (r = -0.358, p = 0.048). Although the plasma vaspin level quartile did not have a significant association with patient survival in the entire cohort, it had a significant interaction with diabetic status (p < 0.001). In nondiabetic patients, plasma vaspin level quartile was an independent predictor of patient survival after adjusting for confounding clinical factors (adjusted hazard ratio 2.038, 95% confidence interval 1.191-3.487, p = 0.009), while the result for diabetic patients was not significant.

CONCLUSIONS

Plasma vaspin level quartile had a significant association with patient survival in non-diabetic PD patients. Baseline plasma vaspin level also had a modest inverse correlation with the subsequent change in the severity of insulin resistance, but the exact biological role of vaspin deserves further studies.

Omentin-1 Levels and Outcomes in Incident Peritoneal Dialysis Patients

Rationale & Objective

Omentin-1 is an adipokine with anti-inflammatory and cardioprotective properties. The objective of this study was to determine the prognostic role of plasma omentin-1 levels in incident peritoneal dialysis (PD) patients.

Study Design

Retrospective analysis of prospective cohort.

Setting & Participants

152 incident PD patients.

Predictors

Plasma omentin-1 level, adipose tissue omentin-1 messenger RNA (mRNA) expression.

Outcomes

Patient survival, technique survival, hospital admission, and duration of stay.

Analytical Approach

Time-to-event survival analyses; linear regression for hospitalization.

Results

The mean age was 58.4 ± 11.7 years; 102 were men, and 92 had diabetes. There was no significant correlation between plasma omentin-1 level and its adipose tissue mRNA expression. A higher plasma omentin-1 level quartile was not associated with patient survival (P = 0.92) or technique survival (P = 0.83) but had a modest correlation with a lower number of hospital admissions (P = 0.07) and shorter duration of hospital stay (P = 0.04). In adjusted models using multivariable linear regression, a higher plasma omentin-1 level quartile remained significantly associated with fewer hospital admissions (β, -0.13; 95% CI, -0.26 to -0.002; P = 0.05) and shorter hospitalization duration (β, -0.20; 95% CI, -0.38 to -0.02; P = 0.03).

Limitations

Observational study with baseline measures only.

Conclusions

Plasma omentin-1 level was not associated with patient survival, technique survival, or peritonitis, but higher plasma omentin-1 levels were associated with fewer hospital admissions and shorter duration of hospitalization among incident PD patients.

Circulating and Adipose Tissue Adiponectin Level and Outcomes in Incident Peritoneal Dialysis Patients

Rationale & Objective

Cardiovascular disease is the major cause of mortality and morbidity in peritoneal dialysis (PD) patients. Adiponectin, a key adipokine, is related to obesity and insulin resistance. We determined the clinical and prognostic value of plasma adiponectin level and its adipose tissue messenger RNA (mRNA) expression in new PD patients.

Study Design

Retrospective analysis of a prospective observational study.

Setting & Participants

152 new PD patients from a single center; 6 adults undergoing abdominal surgeries without kidney disease served as controls.

Predictors

Plasma adiponectin level and its adipose tissue mRNA expression.

Outcomes

Body build and composition, patient and technique survival.

Analytical Approach

Adiponectin level and mRNA expression were grouped in quartiles for correlation analysis for body build and Cox regression for survival analysis.

Results

The median plasma adiponectin level was 31.98 μg/mL (IQR, 16.81-49.49 μg/mL), and adiponectin mRNA expression in adipose tissue was 1.65 times higher than in controls (IQR, 0.98-2.63). There was a modest but statistically significant correlation between plasma adiponectin and its adipose tissue mRNA expression (r = 0.40, P < 0.001). Plasma adiponectin level inversely correlated with body mass index, waist-hip ratio, mid-arm circumference, adipose tissue mass, plasma triglyceride (r = -0.39, -0.38, -0.41, -0.38, and -0.30, respectively; P < 0.001 for all), as well as serum insulin level (r = -0.24, P = 0.005). Similar correlations were present but less marked with adipose tissue adiponectin mRNA level. Neither plasma adiponectin level nor adipose tissue adiponectin mRNA level predicted patient or technique survival.

Limitations

Observational study, single center, single baseline measurement.

Conclusions

Plasma adiponectin level correlated with the degree of adiposity in new PD patients. However, neither plasma adiponectin level nor its adipose tissue mRNA expression was an independent prognostic indicator in kidney failure patients newly started on PD.

Clinical Consequences of Metabolic Acidosis-Muscle

Metabolic acidosis is common in people with chronic kidney disease and can contribute to functional decline, morbidity, and mortality. One avenue through which metabolic acidosis can result in these adverse clinical outcomes is by negatively impacting skeletal muscle; this can occur through several pathways. First, metabolic acidosis promotes protein degradation and impairs protein synthesis, which lead to muscle breakdown. Second, metabolic acidosis hinders mitochondrial function, which decreases oxidative phosphorylation and reduces energy production. Third, metabolic acidosis directly limits muscle contraction. The purpose of this review is to examine the specific mechanisms of each pathway through which metabolic acidosis affects muscle, the impact of metabolic acidosis on physical function, and the effect of treating metabolic acidosis on functional outcomes.

Plant-Based Diets and Peritoneal Dialysis: A Review

Whole food plant-based diets are gaining popularity as a preventative and therapeutic modality for numerous chronic health conditions, including chronic kidney disease, but their role and safety in end-stage kidney disease patients on peritoneal dialysis (PD) is unclear. Given the general public’s increased interest in this dietary pattern, it is likely that clinicians will encounter individuals on PD who are either consuming, considering, or interested in learning more about a diet with more plants. This review explores how increasing plant consumption might affect those on PD, encompassing potential benefits, including some specific to the PD population, and potential concerns.

Peritoneal dialysis adequacy: a paradigm shift

For the past 30 years, nephrologists have focused on a single minimal threshold of Kt/V_urea to determine the adequacy of peritoneal dialysis (PD). To date, there is no evidence that shows Kt/V_urea to be a good surrogate measure of uremic symptom control or nutritional state in patients on PD. Volume of distribution (V_urea) generally is considered equivalent to total body water (TBW). Yet, accurate determination of TBW is difficult. The most recent International Society for Peritoneal Dialysis practice recommendations on prescribing high-quality PD emphasized incorporation of multiple measures rather than the single value of Kt/V_urea. These measures include shared decision-making between the patient and the care team and assessment of health-related quality of life, burden of uremic symptoms, presence of residual kidney function, volume status, and biochemical measures including serum potassium and bicarbonate levels. In some cases, PD prescriptions can be tailored to the patient priorities and goals of care, such as in frail and pediatric patients. Overall, there has been a paradigm shift in providing high-quality care to PD patients. Instead of focusing on small solute clearance in the form of Kt/V_urea, nephrologists are encouraged to use a more comprehensive assessment of the patient as a whole.

The change in the prevalence of obesity and new-onset diabetes in Chinese peritoneal dialysis patients over 25 years

Background

The global prevalence of both obesity and end-stage kidney diseases (ESKDs) has increased in recent decades. Given the complicated interaction between obesity and ESKD, we examined the change in the prevalence of obesity in incident Chinese peritoneal dialysis (PD) patients over the past 25 years.

Methods

We reviewed the anthropometric measures of incident PD patients in a single Hong Kong center from 1995 to 2019. The results are reported in five 5-year periods. Patients with and without diabetes were analyzed separately, and the incidence of new-onset diabetes after PD was explored.

Results

We reviewed 1681 patients. Their mean age was 58.4 ± 12.5 years; 931 patients (55.4%) had pre-existing diabetes. From 1995–99 to 2015–19, the prevalence of obesity or overweight at the initiation of PD increased progressively for every 5-year period (from 21.9% to 26.2, 37.9, 42.7 and 47.3%, P < 0.001 for linearity). The increase in the prevalence of obesity or overweight was more pronounced in diabetic patients (from 33.7% to 59.6%) than non-diabetic ones (from 13.2% to 32.3%). Among nondiabetics patients, the incidence of new-onset diabetes after started on PD showed an insignificant rising trend during that period (from 18.0, 19.7, 17.8 and 22.4% to 23.3%, P = 0.106). The incidence of new-onset impaired fasting glucose or diabetes was significantly higher in obese or overweight patients than the others (56.9% versus 51.4%, P < 0.001).

Conclusions

The prevalence of obesity has increased substantially in both diabetic and nondiabetic new PD patients in Hong Kong over the past 25 years. The incidence of new-onset diabetes was significantly higher in new PD patients with pre-existing obesity or overweight than those without obesity. The prognostic implication and impacts on the healthcare system deserve further studies.

Dietary strategies for gut-derived protein-bound uremic toxins and cardio-metabolic risk factors in chronic kidney disease: A focus on dietary fibers

Chronic kidney disease (CKD) is associated with altered composition and function of gut microbiota. The cause of gut dysbiosis in CKD is multifactorial and encompasses the following: uremic state, metabolic acidosis, slow colonic transit, dietary restrictions of plant-based fiber-rich foods, and pharmacological therapies. Dietary restriction of potassium-rich fruits and vegetables, which are common sources of fermentable dietary fibers, inhibits the conversion of dietary fibers to short-chain fatty acids (SCFA), which are the primary nutrient source for the symbiotic gut microbiota. Reduced consumption of fermentable dietary fibers limits the population of SCFA-forming bacteria and causes dysbiosis of gut microbiota. Gut dysbiosis induces colonic fermentation of protein and formation of gut-derived uremic toxins. In this review, we discuss the roles and benefits of dietary fiber on gut-derived protein-bound uremic toxins and plant-based dietary patterns that could be recommended to decrease uremic toxin formation in CKD patients. Recent studies have indicated that dietary fiber supplementation may be useful to decrease gut-derived uremic toxin formation and slow CKD progression. However, research on associations between adherence of healthy dietary patterns and gut-derived uremic toxins formation in patients with CKD is lacking.

Oral sodium bicarbonate in people on haemodialysis: a randomised controlled trial

Background

Adverse events and mortality tend to cluster around dialysis sessions, potentially due to the impact of the saw-toothed profile of uraemic toxins such as potassium, peaking pre-dialysis and rapidly dropping during dialysis. Acidosis could be contributing to this harm by exacerbating a rise in potassium. The objectives of this study were to investigate the effects of oral bicarbonate treatment on reducing inter-dialytic potassium gain as well as other clinical consequences of preserving muscle mass and function and reducing intradialytic arrhythmia risk in people on haemodialysis.

Methods

Open-label randomised controlled trial in a single-centre (London, UK). Forty-three clinically stable adults on haemodialysis were recruited, with a 6 month average pre-dialysis serum bicarbonate level < 22 mmol/l and potassium > 4 mmol/l. Thirty-three participants completed the study. Oral sodium bicarbonate tablets titrated up to a maximum of 3 g bd (6 g total) in intervention group for 12 weeks versus no treatment in the control group. Outcomes compared intervention versus non-intervention phases in the treated group and equivalent time points in the control group: pre- and post-dialysis serum potassium; nutritional assessments: muscle mass and handgrip strength and electrocardiograms (ECGs) pre and post dialysis.

Results

Participants took an average of 3.7 ± 0.5 g sodium bicarbonate a day. In the intervention group, inter-dialytic potassium gain was reduced from 1.90 ± 0.60 to 1.69 ± 0.49 mmol/l (p = 0.032) and pre-dialysis potassium was reduced from 4.96 ± 0.62 to 4.79 ± 0.49 mmol/l without dietary change. Pre-dialysis bicarbonate increased from 18.15 ± 1.35 to 20.27 ± 1.88 mmol/l, however with an increase in blood pressure. Nutritionally, lean tissue mass was reduced in the controls suggesting less catabolism in the intervention group. There was no change in ECGs. Limitations are small sample size and unblinded study design lacking a placebo, with several participants failing to achieve the target of 22 mmol/l serum bicarbonate levels due mainly to tablet burden.

Conclusion

Oral sodium bicarbonate reduced bicarbonate loss and potassium gain in the inter-dialytic period, and may also preserve lean tissue mass.

Trial registration

The study was registered prospectively on 06/08/2015 with EU Clinical Trials Register EudraCT number 2015-001439-20.

Prognostic significance of peritoneal dialysis effluent mitochondrial DNA level

BACKGROUND

Mitochondrial DNA (mtDNA) resembles bacterial DNA and potentially triggers local and systemic inflammation. We evaluate the prognostic implications of PD effluent mtDNA level in peritoneal dialysis (PD) patients.

METHODS

We measured mtDNA in the PD effluent (PDE) sediment and supernatant of 168 incident PD patients. All patients were followed for hospitalization, technique and overall survival.

RESULTS

The median PD effluent supernatant and sediment mtDNA levels were 255.4 unit (interquartile range [IQR] 157.5-451.3) and 201.6 unit (IQR 147.8-267.3), respectively. Serum C-reactive protein level closely with PDE sediment mtDNA level (r = 0.471, p < 0.001) and less with supernatant mtDNA level (r = 0.156, p = 0.044). PDE supernatant mtDNA level correlates with dialysate-to-plasma creatinine ratio at 4 h (D/P4) (r = 0.361, p < 0.001) but not with any clinical outcome. PDE sediment mtDNA was an independent predictor of technique survival (p = 0.011) and the duration of hospitalization (p = 0.044) after adjusting for clinical confounding factors.

CONCLUSIONS

PDE sediment mtDNA level significantly correlated with systemic inflammation, while PDE supernatant mtDNA level correlated with peritoneal transport. PDE sediment mtDNA level also independently predicted technique survival and duration of hospitalization. The mechanism of the different implications between PDE sediment and supernatant mtDNA levels deserves further investigations.

Metabolic Acidosis in CKD: A Review of Recent Findings

Metabolic acidosis is fairly common in patients with chronic kidney disease (CKD). The prevalence of metabolic acidosis increases with worsening kidney function and is observed in ∼40% of those with stage 4 CKD. For the past 2 decades, clinical practice guidelines have suggested treatment of metabolic acidosis to counterbalance adverse effects of metabolic acidosis on bone and muscle. Studies in animal models of CKD also demonstrated that metabolic acidosis causes kidney fibrosis. During the past decade, results from observational studies identified associations between metabolic acidosis and adverse kidney outcomes, and results from interventional studies support the hypothesis that treating metabolic acidosis with sodium bicarbonate preserves kidney function. However, convincing data from large-scale, double-blinded, placebo-controlled, randomized trials have been lacking. This review discusses findings from recent interventional trials of alkali therapy in CKD and new findings linking metabolic acidosis with cardiovascular disease in adults and CKD progression in children. Finally, a novel agent that treats metabolic acidosis in patients with CKD by binding hydrochloric acid in the gastrointestinal tract is discussed.

KDOQI US Commentary on the 2020 ISPD Practice Recommendations for Prescribing High-Quality Goal-Directed Peritoneal Dialysis

The recently published 2020 International Society for Peritoneal Dialysis (ISPD) practice recommendations regarding prescription of high-quality goal-directed peritoneal dialysis differ fundamentally from previous guidelines that focused on "adequacy" of dialysis. The new ISPD publication emphasizes the need for a person-centered approach with shared decision making between the individual performing peritoneal dialysis and the clinical care team while taking a broader view of the various issues faced by that individual. Cognizant of the lack of strong evidence for the recommendations made, they are labeled as "practice points" rather than being graded numerically. This commentary presents the views of a work group convened by the National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) to assess these recommendations and assist clinical providers in the United States in interpreting and implementing them. This will require changes to the current clinical paradigm, including greater resource allocation to allow for enhanced services that provide a more holistic and person-centered assessment of the quality of dialysis delivered.

KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update

The National Kidney Foundation's Kidney Disease Outcomes Quality Initiative (KDOQI) has provided evidence-based guidelines for nutrition in kidney diseases since 1999. Since the publication of the first KDOQI nutrition guideline, there has been a great accumulation of new evidence regarding the management of nutritional aspects of kidney disease and sophistication in the guidelines process. The 2020 update to the KDOQI Clinical Practice Guideline for Nutrition in CKD was developed as a joint effort with the Academy of Nutrition and Dietetics (Academy). It provides comprehensive up-to-date information on the understanding and care of patients with chronic kidney disease (CKD), especially in terms of their metabolic and nutritional milieu for the practicing clinician and allied health care workers. The guideline was expanded to include not only patients with end-stage kidney disease or advanced CKD, but also patients with stages 1-5 CKD who are not receiving dialysis and patients with a functional kidney transplant. The updated guideline statements focus on 6 primary areas: nutritional assessment, medical nutrition therapy (MNT), dietary protein and energy intake, nutritional supplementation, micronutrients, and electrolytes. The guidelines primarily cover dietary management rather than all possible nutritional interventions. The evidence data and guideline statements were evaluated using Grading of Recommendations, Assessment, Development and Evaluation (GRADE) criteria. As applicable, each guideline statement is accompanied by rationale/background information, a detailed justification, monitoring and evaluation guidance, implementation considerations, special discussions, and recommendations for future research.

Nutritional Status in Peritoneal Dialysis: Nutritional Guidelines, Adequacy and the Management of Malnutrition

The positive impact of nutritional status on the health and treatment adequacy of peritoneal dialyzed patients has been well established. Protein intake is an important factor used to stratify malnutrition, with inadequate intake leading to protein-energy wasting during the course of therapy. In this review, we discuss the recommendations made by nephrological societies regarding nutrition in this population of dialysis patients. Special attention is given to the intake of protein, and recommendations on the intake of micronutrients are also discussed. Furthermore, factors that may impair nutritional intake and balance are discussed, with mention of the innovative strategies utilized to combat them. In light of inconsistent recommendations that vary between each respective society, as well as a general lack of concise information, it is our intention to call for further research regarding nutritional recommendations in peritoneal dialysis (PD), as well as to advocate for clear and accessible information for patients.

Advances in management of chronic metabolic acidosis in chronic kidney disease

PURPOSE OF REVIEW

Chronic metabolic acidosis is a common complication of chronic kidney disease (CKD) and is associated with adverse consequences, such as CKD progression and muscle wasting. We review the findings from recent clinical trials that have examined the effects of sodium bicarbonate therapy and veverimer in patients with CKD and chronic metabolic acidosis.

RECENT FINDINGS

There are four recent clinical trials on chronic metabolic acidosis of CKD. In a pilot, cross-over study, 6 weeks of sodium bicarbonate therapy improved vascular endothelial function, measured by brachial artery flow-mediated dilation. In a single-center, randomized, open-label study, 6 months of sodium bicarbonate therapy increased muscle mass and lean body mass, and preserved kidney function. The other two clinical trials (phase 1/2 and phase 3 studies) examined the effects of veverimer, which is a hydrochloric acid binder. The phase 3 study showed that 12-weeks of veverimer increased serum bicarbonate levels and might improve physical function. The effects of veverimer on CKD progression, physical function and cardiovascular endpoints as well as its long-term safety are yet to be determined.

SUMMARY

Recent studies suggest that sodium bicarbonate therapy may improve vascular endothelial function and muscle mass, and preserve renal function. Veverimer increases serum bicarbonate level and could be a potential new therapeutic option for treating chronic metabolic acidosis.

The Impact of Social Support on the Survival of Chinese Peritoneal Dialysis Patients

Background

Social support is an independent risk factor for mortality among new hemodialysis patients. We evaluated the effect of social support on the outcome of Chinese peritoneal dialysis (PD) patients.

Methods

We studied 167 prevalent PD patients. They completed the Medical Outcomes Study Social Support Survey, Chinese Version (MOS-SSS-C) questionnaire. Patients were followed for 1 year. Outcome measures included change in nutritional status, hospitalization, and technique and actuarial patient survival.

Results

Actuarial survival was 57.1%, 72.7%, 85.3%, and 88.6% for MOS-SSS-C total score quartiles I, II, III, and IV, respectively (log rank test, p = 0.037). Technique survival was 57.1%, 81.9%, 91.9%, and 91.4% (log rank test, p = 0.0044). By multivariate analysis with the Cox proportional hazard model to adjust for confounders, every 1 point increase in MOS-SSS-C total score was associated with a 0.6% [95% confidence interval (CI) 0.2% – 0.9%, p = 0.003] reduction in the risk of death and a 0.5% (95%CI 0.1% – 1.0%, p = 0.037) reduction in the risk of technique failure. The MOS-SSS-C score had no significant effect on change in nutritional or dialysis adequacy indices, hospitalization, or number of peritonitis episodes in 1 year.

Conclusion

The degree of social support is an important predictor of actuarial and technique survival in Chinese PD patients. Measures to enhance social support may represent an easily achievable means of improving the clinical outcome of PD patients.

New-Onset Diabetes Mellitus in Peritoneal Dialysis and Hemodialysis Patients: Frequency, Risk Factors, and Prognosis-A Review

New-onset diabetes mellitus (NODM) is observed in both hemodialysis (HD) and peritoneal dialysis (PD) patients. The prevalence of NODM in dialysis patients is slightly higher compared to subjects of the general population. Based on currently published data there is no convincing evidence that the risk of NODM is different between HD and PD patients. Data on the effect of glucose load on risk of NODM in dialysis patients remain controversial. PD modality (automated or continuous ambulatory PD) has no significant influence on NODM incidence. Chronic inflammation is associated with NODM in dialysis patients. Reported differences in NODM between PD and HD patients are possibly also influenced by differences in demographic factors between these patient groups. Mortality in NODM patients is lower than mortality in patients with preexisting DM. This may be partly explained by the younger age and lower number of comorbidities in patients with NODM.

Relationship between Plasma Endocan Level and Clinical Outcome of Chinese Peritoneal Dialysis Patients

BACKGROUND

Endocan is associated with endothelial dysfunction. In peritoneal dialysis (PD) patients, cardiovascular disease is a common cause of mortality. We examined the relationship between serum endocan level and clinical outcome of PD patients.

METHODS

We recruited 193 new PD patients (118 males, mean age 58.8 ± 11.6 years). Serum endocan levels were determined and stratified into tertile 1 (lowest) to 3 (highest). Nutritional status, arterial pulse wave velocity (PWV) and serum C-reactive protein (CRP) levels were measured. The patients were followed for at least 4 years for clinical outcomes.

RESULTS

For the whole cohort, patients with higher serum endocan levels had lower serum albumin and subjective global assessment score, higher carotid-femoral PWV, and higher serum CRP. For patients with suboptimal blood pressure (BP) control, cardiovascular event-free survival was 95.0, 95.5, and 78.5% for tertiles 1, 2, and 3 at 60 months respectively (p = 0.019). Multivariate Cox regression analysis showed that serum endocan level was an independent predictor of cardiovascular event-free survival. No association with cardiovascular event-free survival was found for patients with adequate BP control (95.0, 92.3, and 100% for tertile 1, 2, and 3 at 60 months, respectively, p = 0.6).

CONCLUSIONS

Higher serum endocan level is associated with unfavourable nutritional, arterial and inflammatory conditions in PD patients. In patients with suboptimal BP control, higher serum endocan is also associated with worse cardiovascular outcome.

Peritoneal protein clearance predicts mortality in peritoneal dialysis patients

BACKGROUND

Peritoneal protein clearance has been suggested to be a marker of peritoneal inflammation and systemic endothelial dysfunction.

METHODS

We enrolled 711 consecutive incident PD patients. Baseline peritoneal protein clearance and other clinical information were reviewed. All patients were followed for at least 1 year for all-cause and cardiovascular mortality.

RESULTS

The average PD effluent protein loss was 6.41 ± 2.16 g/day; peritoneal protein clearance was 97.15 ± 41.55 mL/day. The average duration of follow-up was 50.8 ± 36.2 months. Multivariate linear regression analysis showed that serum albumin, C-reactive protein, and mass transfer area coefficients of creatinine were independently associated with peritoneal protein clearance. By multivariate Cox regression analysis, age, Charlson comorbidity score, volume of overhydration and peritoneal protein clearance were independent predictors of all-cause mortality. Every 10 mL/day increase in peritoneal protein clearance confers 10.4% increase in risk of all-cause mortality (95% confidence interval 2.6-18.7%, p = 0.008). Peritoneal protein clearance was also associated with cardiovascular mortality by univariate analysis, but the association became insignificant after adjusting for confounding factors Cox regression analysis.

CONCLUSIONS

Baseline peritoneal protein clearance is an independent predictor of all-cause mortality in incident PD patients. Routine measurement of peritoneal protein clearance may facilitate patient risk stratification.

Acid-base alterations in ESRD and effects of hemodialysis

Acid-base alterations in patients with kidney failure and on hemodialysis (HD) treatment contribute to (1) intradialytic hypercapnia and hypoxia, (2) hemodynamic instability and cardiac arrhythmia, (3) systemic inflammation, and (4) a number of associated electrolyte alterations including potentiating effects of hypokalemia, hypocalcemia and, chronically, soft-tissue and vascular calcification, imparting poor prognosis and mortality. This paper discusses acid-base regulation and pathogenesis of dysregulation in patients with kidney failure. Major organ and systemic effects of acid-base perturbations with a specific focus on kidney failure patients on HD are emphasized, and potential mitigating strategies proposed. The high rate of HD-related complications, specifically those that can be accounted for by rapid and steep acid-base perturbations imposed by HD treatment, attests to the pressing need for investigations to establish a better dialysis regimen.

Renal Association Clinical Practice Guideline on peritoneal dialysis in adults and children

These guidelines cover all aspects of the care of patients who are treated with peritoneal dialysis. This includes equipment and resources, preparation for peritoneal dialysis, and adequacy of dialysis (both in terms of removing waste products and fluid), preventing and treating infections. There is also a section on diagnosis and treatment of encapsulating peritoneal sclerosis, a rare but serious complication of peritoneal dialysis where fibrotic (scar) tissue forms around the intestine. The guidelines include recommendations for infants and children, for whom peritoneal dialysis is recommended over haemodialysis.Immediately after the introduction there is a statement of all the recommendations. These recommendations are written in a language that we think should be understandable by many patients, relatives, carers and other interested people. Consequently we have not reworded or restated them in this lay summary. They are graded 1 or 2 depending on the strength of the recommendation by the authors, and A-D depending on the quality of the evidence that the recommendation is based on.

Clinical Practice Guideline on management of older patients with chronic kidney disease stage 3b or higher (eGFR<45 mL/min/1.73 m2): a summary document from the European Renal Best Practice Group

The population of patients with moderate and severe CKD is growing. Frail and older patients comprise an increasing proportion. Many studies still exclude this group, so the evidence base is limited. In 2013 the advisory board of ERBP initiated, in collaboration with European Union of Geriatric Medicine Societies (EUGMS), the development of a guideline on the management of older patients with CKD stage 3b or higher (eGFR >45 mL/min/1.73 m2). The full guideline has recently been published and is freely available online and on the website of ERBP (www.european-renal-best-practice.org). This paper summarises main recommendations of the guideline and their underlying rationales.

Oral Bicarbonate Slows Decline of Residual Renal Function in Peritoneal Dialysis Patients

BACKGROUND/AIMS

Metabolic acidosis is a common consequence of end-stage renal disease (ESRD) which may result in a substantial adverse outcome. The effect of oral bicarbonate on the preservation of residual renal function (RRF) in peritoneal dialysis (PD) patients has been rarely reported.

METHODS

We randomly assigned 40 continuous ambulatory peritoneal dialysis (CAPD) patients to the oral bicarbonate group or placebo group at a 1: 1 ratio. All enrollments were followed for a duration of 104 weeks. We took residual creatinine clearance (CCr), a measure of residual renal function (RRF), as the primary outcome. Residual CCr was calculated as the average of urea and creatinine clearance from a 24-hour urine collection.

RESULTS

Thirteen patients in the placebo group and 15 patients in the treatment group completed the 104 weeks of follow-up with a comparable dropout rate (placebo group: 35% vs treatment group: 25%). Compared with the placebo group, serum bicarbonate in treatment group was significantly increased at each time point, and oral bicarbonate resulted in a slower declining rate of residual CCr (F=5.113, p=0.031). Baseline residual CCr at enrollment also had a significant effect on residual CCr (F=168.779, P<0.001). Charlson Comorbidity Index which was adopted to calculate a comorbidity score had no significant effect on residual CCr loss (F=0.168, P=0.685).

CONCLUSION

Oral bicarbonate may have a RRF preserving effect in CAPD patients, and a normal to high level of serum bicarbonate (≥24mmol/L) may be appropriate for RRF preservation.

Peritoneal dialysis: The unique features by compartmental delivery of renal replacement therapy

Despite decades of research, the clinical efficacy of peritoneal dialysis (PD) remains enigmatic. We may wonder why the modality fail in some patients but perhaps the more proper question would be, why it works in so many? We know that the contribution of residual renal function (RRF), more so than in hemodialysis, is critically important to the well-being of many of the patients. Unique features of the modality include the relatively low volume of dialysate fluid needed to provide effective uremic control and the disproportionate tendency for both hypokalemia and hypoalbuminemia, when compared to hemodialysis. It is currently believed that most uremic toxins are generated on the interface of human and bacterial structures in the gastrointestinal tract, the intestinal biota. PD offers disproportionate removal of these toxins upon "first-pass", i.e., via PD fluid exchanges before reaching the systemic circulation beyond the gastrointestinal compartment. Studies examining the net removal gradient of protein-bound uremic toxins during PD are scarce, whereas RRF receives considerably more attention without effective interventions being developed to preserve it. We propose an alternative view on PD, emphasizing the modality's compartmental nature, both for its benefits and the limitations.

Bicarbonate Balance and Prescription in ESRD

The optimal approach to managing acid-base balance is less well defined for patients receiving hemodialysis than for those receiving peritoneal dialysis. Interventional studies in hemodialysis have been limited and inconsistent in their findings, whereas more compelling data are available from interventional studies in peritoneal dialysis. Both high and low serum bicarbonate levels associate with an increased risk of mortality in patients receiving hemodialysis, but high values are a marker for poor nutrition and comorbidity and are often highly variable from month to month. Measurement of pH would likely provide useful additional data. Concern has arisen regarding high-bicarbonate dialysate and dialysis-induced alkalemia, but whether these truly cause harm remains to be determined. The available evidence is insufficient for determining the optimal target for therapy at this time.

Bone Density Is Directly Associated With Glomerular Filtration and Metabolic Acidosis but Do Not Predict Fragility Fractures in Men With Moderate Chronic Kidney Disease

Hyperparathyroidism, vitamin D deficiency, increased fibroblast growth factor-23 (FGF-23), and metabolic acidosis promote bone fragility in chronic kidney disease (CKD). Although useful in predicting fracture risk in the general population, the role of dual-energy X-ray absorptiometry (DXA) in CKD remains uncertain. This cross-sectional study included 51 men aged 50-75 yr with moderate CKD. The stage 4 CKD patients had higher levels of parathyroid hormone (p<0.001), FGF-23 (p=0.029), and lowest 25-hydroxyvitamin D (p=0.016), bicarbonate (p<0.001), total femur (p=0.003), and femoral neck (p=0.011) T-scores compared with stage 3 CKD patients. Total femur and femoral neck T-scores were directly correlated with serum bicarbonate (p=0.003, r=0.447 and p=0.005, r=0.427, respectively) and estimated glomerular filtration rate (p=0.024, r=0.325 and p=0.003, r=0.313, respectively) but were not significantly associated with parathyroid hormone, 25-hydroxyvitamin D, or FGF-23. Only 3.9% of the participants had osteoporosis on DXA scan, whereas 31.4% reported a low-impact fracture. Our data point to a pivotal role of metabolic acidosis for bone impairment and to the inadequacy of DXA to evaluate bone fragility in CKD patients.

Circulating bacterial-derived DNA fragment level is a strong predictor of cardiovascular disease in peritoneal dialysis patients

BACKGROUND

Circulating bacterial DNA fragment is related to systemic inflammatory state in peritoneal dialysis (PD) patients. We hypothesize that plasma bacterial DNA level predicts cardiovascular events in new PD patients.

METHODS

We measured plasma bacterial DNA level in 191 new PD patients, who were then followed for at least a year for the development of cardiovascular event, hospitalization, and patient survival.

RESULTS

The average age was 59.3 ± 11.8 years; plasma bacterial DNA level 34.9 ± 1.5 cycles; average follow up 23.2 ± 9.7 months. At 24 months, the event-free survival was 86.1%, 69.8%, 55.4% and 30.8% for plasma bacterial DNA level quartiles I, II, III and IV, respectively (p < 0.0001). After adjusting for confounders, plasma bacterial DNA level, baseline residual renal function and malnutrition-inflammation score were independent predictors of composite cardiovascular end-point; each doubling in plasma bacterial DNA level confers a 26.9% (95% confidence interval, 13.0 - 42.5%) excess in risk. Plasma bacterial DNA also correlated with the number of hospital admission (r = -0.379, p < 0.0001) and duration of hospitalization for cardiovascular reasons (r = -0.386, p < 0.0001). Plasma bacterial DNA level did not correlate with baseline arterial pulse wave velocity (PWV), but with the change in carotid-radial PWV in one year (r = -0.238, p = 0.005).

CONCLUSIONS

Circulating bacterial DNA fragment level is a strong predictor of cardiovascular event, need of hospitalization, as well as the progressive change in arterial stiffness in new PD patients.

Effect of bicarbonate supplementation on renal function and nutritional indices in predialysis advanced chronic kidney disease

Current practice guidelines recommend alkali therapy in patients with chronic kidney disease (CKD) and metabolic acidosis to prevent complications. This study aims to investigate the effect of oral sodium bicarbonate supplementation on the progression of renal function and nutritional indices in patients with predialysis advanced CKD. Forty patients with predialysis stage 5 CKD(estimated glomerular filtration rate, eGFR <15mL/min per 1.73m²) and 40 patients with stage 4 CKD (eGFR 15 to 30mL/min per 1.73m²) who had a total CO₂ less than 22mEq/L were assigned into the bicarbonate treatment group or control group for 12 months. In stage 4 CKD, there were significant differences in the changes of eGFR during the study between the treatment group and the control group (-2.30±4.49 versus -6.58±6.32mL/min/1.73m², p<0.05). However, in stage 5 CKD, there were no significant differences in the change of eGFR during the study between the two groups (-2.10±2.06 versus -3.23±1.95mL/min/1.73 m²).There were no significant differences in the changes of nutritional indices such as albumin, prealbumin, transferrin, total lymphocyte count (TLC), and Ondodera's prognostic nutritional index (OPNI) during the study between the two groups. In stage 5 CKD, there were significant differences in the changes of TLC and OPNI between the two groups.

In conclusion, our results demonstrate that bicarbonate supplementation slows the rate of decline of renal function in stage 4 CKD and improves nutritional indices in stage 5 CKD. Alkali therapy in advanced CKD may have beneficial effect on renal function and malnutrition.

Association of serum bicarbonate with bone fractures in hemodialysis patients: the mineral and bone disorder outcomes study for Japanese CKD stage 5D patients (MBD-5D)

BACKGROUND/AIMS

Bone fracture is often complicated in hemodialysis (HD) patients. Metabolic acidosis is related to bone disease and muscle wasting, but it is not known whether acid-base disturbance is associated with the risk of bone fractures. The aim of this study was to clarify the association of serum bicarbonate level with bone fracture in HD patients.

METHODS

Using a subcohort of the Mineral and Bone Disorder Outcomes Study for Japanese CKD Stage 5D Patients (MBD-5D), 890 prevalent HD patients (age: 62 years old, male: 62.8%, duration of dialysis: 8.3 years) with secondary hyperparathyroidism were studied. After measuring predialysis serum bicarbonate at a 2-day interdialytic interval, we prospectively followed them every 3 months, and examined the occurrence of any type of bone fracture or hospitalization due to fracture over a 3-year observation period.

RESULTS

Seventy-four bone fractures and 47 hospitalizations due to fracture were observed during the follow-up period. HD patients with serum bicarbonate <20 mmol/l had a 1.93 (95% CI 1.01-3.71)-fold higher risk for all-cause fractures than those with serum bicarbonate of 20.0-21.9 mmol/l. A higher bicarbonate level (≥22 mmol/l) was also related to an increased risk of bone fracture. A restricted cubic regression spline disclosed that the higher or the lower than 21.0 mmol/l of serum bicarbonate, the greater the risk for bone fracture.

CONCLUSION

Both a lower level and a higher level of predialysis bicarbonate concentration were associated with risk of bone fracture in HD patients with secondary hyperparathyroidism.

Metabolic syndrome in peritoneal dialysis patients: choice of diagnostic criteria and prognostic implications

BACKGROUND AND OBJECTIVE

In the general population, metabolic syndrome (MES) is associated with cardiovascular risk. However, the definition of MES and its prognostic implication among patients undergoing peritoneal dialysis (PD) remain controversial.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We studied 329 prevalent PD patients from April 2008 to April 2011 and compared four sets of diagnostic criteria: the original World Health Organization (WHO) criteria, the International Diabetes Federation (IDF) criteria, the original National Cholesterol Education Program (NCEP) criteria, and the modified NCEP criteria. Nutritional status, body composition, and arterial pulse-wave velocity were measured. Patients were followed for 31.7 ± 15.5 months.

RESULTS

Among the 329 patients, 175 (53.2%) fulfilled the WHO criteria, 177 (53.8%) the IDF criteria, 199 (60.5%) the original NCEP criteria, and 218 (66.3%) the modified NCEP criteria. The agreement among the four sets of criteria was fair to moderate (Cohen κ=0.35-0.58). Patients with MES defined by all four criteria had higher adipose tissue mass than the others, although the difference in adipose tissue mass was most pronounced with the IDF criteria (MES versus no MES, 18.2 ± 7.9 versus 10.7 ± 5.9 kg; P<0.001). Patients with MES, as defined by the IDF criteria, were hospitalized longer than those without MES (3.82 [interquartile range, 0.00-12.61] versus 1.07 [interquartile range, 0.00-6.43]) days per year of follow-up; P=0.01). Overall survival, cardiovascular survival, or technique survival did not differ between patients with and without MES, irrespective of the diagnostic criteria after adjustment for diabetic status.

CONCLUSION

In patients undergoing PD, overall survival, cardiovascular survival, and technique survival did not differ between patients with and without MES, irrespective of diabetic status and diagnostic criteria. Further studies are needed to establish a new definition or clinical scoring system for risk stratification of PD patients.

A low serum bicarbonate concentration as a risk factor for mortality in peritoneal dialysis patients

BACKGROUND AND AIM

Metabolic acidosis is common in patients with chronic kidney disease and is associated with increased mortality in hemodialysis patients. However, this relationship has not yet been determined in peritoneal dialysis (PD) patients.

METHODS

This prospective observational study included a total of 441 incident patients who started PD between January 2000 and December 2005. Using time-averaged serum bicarbonate (TA-Bic) levels, we aimed to investigate whether a low serum bicarbonate concentration can predict mortality in these patients.

RESULTS

Among the baseline parameters, serum bicarbonate level was positively associated with hemoglobin level and residual glomerular filtration rate (GFR), while it was negatively associated with albumin, C-reactive protein (CRP) levels, peritoneal Kt/V urea, and normalized protein catabolic rate (nPCR) in a multivariable linear regression analysis. During a median follow-up of 34.8 months, 149 deaths were recorded. After adjustment for age, diabetes, coronary artery disease, serum albumin, ferritin, CRP, residual GFR, peritoneal Kt/V urea, nPCR, and percentage of lean body mass, TA-Bic level was associated with a significantly decreased risk of mortality (HR per 1 mEq/L increase, 0.83; 95% CI, 0.76-0.91; p < 0.001). In addition, compared to patients with a TA-Bic level of 24-26 mEq/L, those with a TA-Bic level < 22 and between 22-24 mEq/L conferred a 13.10- and 2.13-fold increased risk of death, respectively.

CONCLUSIONS

This study showed that a low serum bicarbonate concentration is an independent risk factor for mortality in PD patients. This relationship between low bicarbonate levels and adverse outcome could be related to enhanced inflammation and a more rapid loss of RRF associated with metabolic acidosis. Large randomized clinical trials to correct acidosis are warranted to confirm our findings.

Treatment of metabolic acidosis in patients with CKD

Metabolic acidosis is a common complication of chronic kidney disease and is believed to contribute to a number of sequelae, including bone disease, altered protein metabolism, skeletal muscle wasting, and progressive glomerular filtration rate loss. Small trials in animal models and humans suggest a role for alkali therapy to lessen these complications. Recent studies support this notion, although more definitive evidence is needed on the long-term benefits of alkali therapy and the optimal serum bicarbonate level. The role of dietary modification also should be given greater consideration. In addition, potential adverse effects of alkali treatment must be taken into consideration, including sodium retention and the theoretical concern of promoting vascular calcification. This teaching case summarizes the rationale for and benefits and complications of base therapy in patients with chronic kidney disease.

Combined walking exercise and alkali therapy in patients with CKD4-5 regulates intramuscular free amino acid pools and ubiquitin E3 ligase expression

Muscle-wasting in chronic kidney disease (CKD) arises from several factors including sedentary behaviour and metabolic acidosis. Exercise is potentially beneficial but might worsen acidosis through exercise-induced lactic acidosis. We studied the chronic effects of exercise in CKD stage 4-5 patients (brisk walking, 30 min, 5 times/week), and non-exercising controls; each group receiving standard oral bicarbonate (STD), or additional bicarbonate (XS) (Total n = 26; Exercising + STD n = 9; Exercising +XS n = 6; Control + STD n = 8; Control + XS n = 3). Blood and vastus lateralis biopsies were drawn at baseline and 6 months. The rise in blood lactate in submaximal treadmill tests was suppressed in the Exercising + XS group. After 6 months, intramuscular free amino acids (including the branched chain amino acids) in the Exercising + STD group showed a striking chronic depletion. This did not occur in the Exercising + XS group. The effect in Exercising + XS patients was accompanied by reduced transcription of ubiquitin E3-ligase MuRF1 which activates proteolysis via the ubiquitin-proteasome pathway. Other anabolic indicators (Akt activation and suppression of the 14 kDa actin catabolic marker) were unaffected in Exercising + XS patients. Possibly because of this, overall suppression of myofibrillar proteolysis (3-methylhistidine output) was not observed. It is suggested that alkali effects in exercisers arose by countering exercise-induced acidosis. Whether further anabolic effects are attainable on combining alkali with enhanced exercise (e.g. resistance exercise) merits further investigation.

Nutrition and the kidney: recommendations for peritoneal dialysis

Protein energy wasting (PEW) is highly prevalent in peritoneal dialysis (PD) and is associated with poor outcomes, including hospitalization and mortality. Recognizing and diagnosing PEW in PD is important; although studies are limited, there are interventions that may be associated with improved outcomes. In this review of nutritional aspects of PD, we highlight some of the important causes of PEW and explore the current diagnostic tools that are used to assess PEW. Finally, we discuss the established and experimental therapies for PEW in PD.

Effects of oral sodium bicarbonate in patients with CKD

BACKGROUND AND OBJECTIVES

Metabolic acidosis contributes to muscle breakdown in patients with CKD, but whether its treatment improves functional outcomes is unknown. The choice of dose and tolerability of high doses remain unclear. In CKD patients with mild acidosis, this study evaluated the dose-response relationship of alkali with serum bicarbonate, its side effect profile, and its effect on muscle strength.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this single-blinded pilot study from March of 2009 to August of 2010, 20 adults with estimated GFR 15-45 ml/min per 1.73 m(2) and serum bicarbonate 20-24 mEq/L were treated during successive 2-week periods with placebo followed by escalating oral NaHCO3 doses (0.3, 0.6, and 1.0 mEq/kg per day). At each visit, handgrip strength and time required to complete 5 and 10 repetitions of a sit-to-stand test were measured.

RESULTS

Each 0.1 mEq/kg per day increase in dose produced a 0.33 mEq/L (95% confidence interval=0.23-0.43 mEq/L) higher serum bicarbonate. Sit-to-stand time improved after 6 weeks of oral NaHCO3 (23.8±1.4 versus 22.2±1.6 seconds for 10 repetitions, P=0.002), and urinary nitrogen excretion decreased (-0.70 g/g creatinine [95% confidence interval=-1.11 to -0.30] per 0.1 mEq/kg per day higher dose). No statistically significant change was seen in handgrip strength (29.5±9.6 versus 28.4±9.4 kg, P=0.12). Higher NaHCO3 doses were not associated with increased BP or greater edema.

CONCLUSIONS

NaHCO3 supplementation produces a dose-dependent increase in serum bicarbonate and improves lower extremity muscle strength after a short-term intervention in CKD patients with mild acidosis. Long-term studies are needed to determine if this finding translates into improved functional status.

Frailty and protein-energy wasting in elderly patients with end stage kidney disease

Older people constitute an increasingly greater proportion of patients with advanced CKD, including those patients undergoing maintenance dialysis treatment. Frailty is a biologic syndrome of decreased reserve and resistance to stressors that results from cumulative declines across multiple physiologic systems and causes vulnerability to adverse outcomes. Frailty is common in elderly CKD patients, and it may be associated with protein-energy wasting (PEW), sarcopenia, dynapenia, and other complications of CKD. Causes of frailty with or without PEW in the elderly with CKD can be classified into three categories: causes primarily caused by aging per se, advanced CKD per se, or a combination of both conditions. Frailty and PEW in elderly CKD patients are associated with impaired physical performance, disability, poorer quality of life, and reduced survival. Prevention and treatment of these conditions in the elderly CKD patients often require a multifaceted approach. Here, we examine the causes and consequences of these conditions and examine the interplay between frailty and PEW in elderly CKD patients.

Nutrition in patients on peritoneal dialysis

Protein-energy wasting (PEW) is prevalent among patients on dialysis and has emerged as an important risk factor for morbidity and mortality in these patients. Numerous factors, including inflammation, inadequate dialysis, insufficient nutrient intake, loss of protein during dialysis, chronic acidosis, hypercatabolic illness and comorbid conditions, are involved in the development of PEW. The causes and clinical features of PEW in patients on peritoneal dialysis and hemodialysis are comparable; assessment of the factors that lead to PEW in patients receiving peritoneal dialysis is important to ensure that PEW is managed correctly in these patients. For the past 20 years, much progress has been made in the prevention and treatment of PEW. However, the results of most nutritional intervention studies are inconclusive. In addition, the multifactorial and complicated pathogenesis of PEW makes it difficult to assess and treat. This Review summarizes the nutritional issues regarding the causes, assessment and treatment of PEW, with a focus on patients receiving peritoneal dialysis. In addition, an in-depth overview of the results of nutritional intervention studies is provided.

Sevelamer carbonate in the treatment of hyperphosphatemia in patients with chronic kidney disease on hemodialysis

Sevelamer carbonate is an anion exchange pharmaceutical, developed to improve on the performance of the non-absorbable, non-calcium, and metal-free phosphate binder sevelamer hydrochloride. Sevelamer carbonate is expected not to worsen metabolic acidosis, as previously reported during long-term treatment with sevelamer hydrochloride in hemodialysis (HD) patients. Carbonate is the alternate counterion to chloride on the sevelamer polymeric backbone, but the active poly(allylamine) responsible for phosphate (PO₄) binding remains unaltered. Therefore, sevelamer carbonate is expected to reduce elevated serum phosphorus level, similarly to sevelamer hydrochloride. Sevelamers are prescribed in uremic HD patients to control hyperphosphatemia, but the carbonate has also been proposed for the treatment of chronic kidney disease (CKD) non-dialysis patients. Although hyperphosphatemia is regarded as a main contributor to increased mortality in the HD population because of cardiovascular calcification, metabolic acidosis has also been advocated as a major player in the increased mortality in this population, by engendering malnutrition, negative nitrogen balance, and inflammation. This paper reviews the evidence showing that sevelamer carbonate is as good as sevelamer hydrochloride in terms of hyperphosphatemia control in CKD, but with a better outcome in serum bicarbonate balance.