Role of an improvement in acid-base status and nutrition in CAPD patients

Pharmacologic therapeutics in sarcopenia with chronic kidney disease

Inflammation, metabolic acidosis, renin-angiotensin system activation, insulin resistance, and impaired perfusion to skeletal muscles, among others, are possible causes of uremic sarcopenia. These conditions induce the activation of the nuclear factor-kappa B and mitogen-activated protein kinase pathways, adenosine triphosphate ubiquitin-proteasome system, and reactive oxygen species system, resulting in protein catabolism. Strategies for the prevention and treatment of sarcopenia in chronic kidney disease (CKD) are aerobic and resistance exercises along with nutritional interventions. Anabolic hormones have shown beneficial effects. Megestrol acetate increased weight, protein catabolic rate, and albumin concentration, and it increased intracellular water component and muscle mass. Vitamin D supplementation showed improvement in physical function, muscle strength, and muscle mass. Correction of metabolic acidosis showed an increase in protein intake, serum albumin levels, body weight, and mid-arm circumference. The kidney- gut-muscle axis indicates that dysbiosis and changes in gut-derived uremic toxins and short-chain fatty acids affect muscle mass, composition, strength, and functional capacity. Biotic supplements, AST-120 administration, hemodiafiltration, and preservation of residual renal function are alleged to reduce uremic toxins, including indoxyl sulfate (IS) and p-cresyl sulfate (PCS). Synbiotics reversed the microbiota change in CKD patients and decreased uremic toxins. AST-120 administration changed the overall gut microbiota composition in CKD. AST-120 prevented IS and PCS tissue accumulation, ameliorated muscle atrophy, improved exercise capacity and mitochondrial biogenesis, restored epithelial tight junction proteins, and reduced plasma endotoxin levels and markers of oxidative stress and inflammation. In a human study, the addition of AST-120 to standard treatment had modest beneficial effects on gait speed change and quality of life.

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.

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.

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.

Uremic Sarcopenia

"Uremic sarcopenia" refers to a progressive decrease in muscle mass, strength, and function despite normal skeletal muscle physiology in patients with chronic kidney disease (CKD). Sarcopenia involves multiple risk factors, comprising immunological changes, hormonal, metabolic acidosis, reduced protein intake, and physical inactivity. All these risk factors, along with complex pathophysiological mechanisms including ubiquitin, insulin/IGF-1, myostatin, and indoxyl sulfate, activate downstream pathways that ultimately increase muscle degradation while reducing muscle regeneration. Uremic sarcopenia not only affects the quality of life but also increases the risk of morbidity and mortality in patients with CKD. Of all the treatment modalities, aerobic and resistance exercise have shown prevention and reduced rate of muscle degeneration. A variety of pharmacological agents have been tried to target different steps in the known pathogenetic pathways, including the use of androgens and anabolic steroids, correction of vitamin D deficiency, use of growth hormone supplementation, and suppression of the ubiquitin pathway. Though some of these techniques have had beneficial results in animal experiments, human trials are still sparse. This review article relates to recent publications that describe the abnormalities in skeletal muscle that primarily leads to muscle wasting and its consequences in patients with CKD.

Sarcopenia in Chronic Kidney Disease: A Scoping Review of Prevalence, Risk Factors, Association with Outcomes, and Treatment

Sarcopenia, a condition characterized by loss of skeletal muscle mass and function, has important clinical ramifications. We aimed to map the existing literature about prevalence, risk factors, associated adverse outcomes, and treatment of sarcopenia in individuals with chronic kidney disease (CKD). A scoping review of the literature was conducted to identify relevant articles published from databases' inception to September 2019. Individuals with CKD, regardless of their disease stage and their comorbidities, were included. Only studies with sarcopenia diagnosed using both muscle mass and function, based on published consensus definitions, were included. For studies on treatment, only randomized controlled trials with at least one sarcopenia parameter as an outcome were included. Our search yielded 1318 articles, of which 60 from were eligible for this review. The prevalence of sarcopenia ranged from 4 to 42% according to the definition used, population studied, and the disease stage. Several risk factors for sarcopenia were identified including age, male gender, low BMI, malnutrition, and high inflammatory status. Sarcopenia was found to be associated with several adverse outcomes, including disabilities, hospitalizations, and mortality. In CKD subjects, several therapeutic interventions have been assessed in randomized controlled trial with a muscle mass, strength, or function endpoint, however, studies focusing on sarcopenic CKD individuals are lacking. The key interventions in the prevention and treatment of sarcopenia in CKD seem to be aerobic and resistance exercises along with nutritional interventions. Whether these interventions are effective to treat sarcopenia and prevent clinical consequences in this population remains to be fully determined.

Effect of Extracorporeal Shock Wave Therapy on Muscle Mass and Function in Patients Undergoing Maintenance Hemodialysis: A Randomized Controlled Pilot Study

Patients undergoing maintenance hemodialysis (MHD) are susceptible to muscle wasting and decreased muscle function, resulting in shorter survival time. This study was aimed at evaluating the effect of radial extracorporeal shock wave therapy (rESWT) on muscle mass and function in patients on MHD. This single blind controlled study was conducted on patients on MHD from September 2018 to December 2019. Eighteen patients were enrolled in the rESWT and control groups. rESWT was performed once a week for 12 wk in both quadriceps femoris muscles of the ESWT group. Finally, 15 patients were assessed for body composition, handgrip strength, physical performance and blood chemistry before rESWT, after rESWT and at a 12-wk follow-up. Leg lean mass and appendicular skeletal muscle mass index increased significantly in the ESWT group compared with the control group (p = 0.001 and p = 0.017). The timed up-and-go test and sit-to-stand tests revealed greater significant improvement in the ESWT group (p = 0.023 and p = 0.046). This study is the first to report that rESWT can improve muscle mass and function in MHD patients. A subsequent study will be conducted to validate the clinical effects of rESWT in a larger sample of patients undergoing MHD.

Relationship Between Serum Total Carbon Dioxide Concentration and Bicarbonate Concentration in Patients Undergoing Peritoneal Dialysis

Background

Few studies have assessed the relationship between serum total carbon dioxide (CO₂) and bicarbonate ion (HCO₃⁻) concentration in patients undergoing peritoneal dialysis. We determined the agreement between serum total CO₂ and HCO₃⁻ concentration and the diagnostic accuracy of serum total CO₂ for the prediction of low (HCO₃⁻ <24 mEq/L) and high (HCO₃⁻ ≥24 mEq/L) bicarbonate concentrations in patients on peritoneal dialysis.

Methods

We collected 245 samples of venous blood from 51 patients on peritoneal dialysis. Independent factors that correlated with the HCO₃⁻ concentration were analyzed using multiple linear regression analysis. The diagnostic accuracy of serum total CO₂ was evaluated by receiver operating characteristic (ROC) curve analysis and a 2×2 table. Agreement between serum total CO₂ and HCO₃⁻ concentration was assessed by Bland-Altman analysis.

Results

Serum total CO₂ was independently correlated with HCO₃⁻ concentration (β = 0.354, p < 0.001). The area under the curve of serum total CO₂ for the identification of low and high bicarbonate concentrations was 0.909. The diagnostic accuracy of serum total CO₂ for the prediction of low and high bicarbonate concentrations was: sensitivity, 91.5%; specificity, 74.7%; positive predictive value, 53.5%; negative predictive value, 96.5%; and accuracy, 78.8%. Bland-Altman analysis showed a moderate agreement between serum total CO₂ and HCO₃⁻ concentration.

Conclusion

Serum total CO₂ correlated closely with the HCO₃⁻ concentration in patients undergoing peritoneal dialysis. Serum total CO₂ might be useful for predicting low and high bicarbonate in peritoneal dialysis patients.

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.

Studying the Effects of New Peritoneal Dialysis Solutions on the Peritoneum

♦ Background

Compelling data underscore the bioincompatible nature of glucose-based peritoneal dialysis (PD) solutions and their detrimental effects on peritoneal physiology and morphology. New PD solutions have been formulated to tackle common clinical problems such as inadequate ultrafiltration or malnutrition, and to improve biocompatibility—the latter aimed at preserving the structural and functional integrity of the peritoneum and reducing adverse systemic effects on the patient.

♦ Methods

This article reviews the factors in PD fluids that alter normal peritoneal anatomy and physiology, and the data that illustrate approaches to investigating the local and systemic biocompatibility of new PD solutions.

♦ Results

Chronic exposure of the peritoneal membrane to glucose-based PD solutions results in denudation of the mesothelium, thickened submesothelium, and hyalinization of the vasculature, often resulting in reduced or lost solute and water clearance. Data from in vitro or animal experiments and clinical studies have shown improved bio-compatibility profiles with new PD solutions that are glucose-free (that is, dialysates with amino acids or icodextrin), bicarbonate-buffered, or compartmentalized during heat sterilization to reduce levels of glucose degradation products. Improved biocompatibility is denoted by reduced induction of proinflammatory, profibrotic, or angiogenic growth factors in mesothelial cells and macrophages, or by less perturbation of leukocyte phagocytic function.

♦ Conclusions

Data from in vitro and animal experiments show more favorable biocompatibility profiles with new PD fluids than with glucose-based dialysates. Clinical studies are ongoing to assess the impact of the new PD fluids on peritoneal function, morbidity, and mortality.

Complications of metabolic acidosis and alkalinizing therapy in chronic kidney disease patients: a clinician-directed organ-specific primer

Chronic kidney disease is prevalent, affecting more than one in ten adults. In this population, metabolic acidosis is considered a key underlying pathophysiological feature, tying together bone mineral disorders, sarcopenia, insulin resistance, vascular calcification, pro-inflammatory and pro-thrombotic states. This review aims to address the paucity of literature on alkalinizing agents, a promising treatment option that has known adverse effects.

Clinical Experience with a New Bicarbonate (25 Mmol/L)/Lactate (10 Mmol/L) Peritoneal Dialysis Solution

Objective

Physiological bicarbonate/lactate-based solutions may correct acidosis in a better way than standard lactate-based solutions. In this study, a new 25 mmol/L bicarbonate/10 mmol/L lactate peritoneal dialysis (PD) solution was compared with a standard 35 mmol/L lactate solution.

Design

This was a prospective open label study. All patients had a 2-week baseline period using the standard lactate solution, followed by 8 weeks on the bicarbonate/lactate solution and 2 weeks on the lactate-basedsolution.

Setting

Four Danish and four Spanish nephrology centers.

Patients

40 well-dialyzed (creatinine clearance > 55 L/week/1.73 m2 body surface area) patients on continuous ambulatory PD.

Interventions

Blood samples were taken for biochemistry (including venous blood gases) at week –2, day 1, weeks 2, 4, and 8, and at follow-up. A physical examination, a peritoneal equilibration test (PET), and quality of life (K/DQOL), ultrafiltration, and adequacy assessments were performed at baseline and at week 8. Vital signs and other safety parameters were followed at each visit. Extraneal (Baxter Healthcare, Castlebar, Ireland) was used by all patients for the long dwell.

Main Outcome Measure

Effect on the venous plasma bicarbonate level.

Results

Venous plasma bicarbonate levels rose from 24.4 mmol/L when patients were on the pure lactate to 26.1 mmol/L when using the bicarbonate/lactate solution ( p < 0.001). When patients were using the bicarbonate/lactate solution, 66% of values were maintained within the venous normal range of 24 – 30 mmol/L, versus 46.2% when patients were on the pure lactate solution ( p < 0.001). There were no adverse findings with respect to clinical symptoms, vital signs, or physical examination. The PET and adequacy, ultrafiltration, and K/DQOL assessment results were unchanged.

Conclusions

The new 25 mmol/L bicarbonate/10 mmol/L lactate solution provided better correction of acidosis than an equivalent 35 mmol/L standard lactate solution, without any safety issues.

Malnutrition: Detection and Intervention

Malnutrition is common in patients with renal failure. Causes of malnutrition in this population are varied and sometimes specific to the method of renal replacement therapy. No single marker absolutely identifies malnutrition or tracks changes in status. Renal dietitians use a variety of parameters and techniques to identify malnutrition because many of the traditional markers can be skewed by renal disease and its comorbidities. Once malnutrition is identified, treatment is also complex and not well defined. Treatment is usually progressive in nature, ranging from intense nutritional counseling to total parenteral nutrition. Further research is needed to define optimal nutrition status, to refine techniques to maintain optimal nutrition status, to simplify the identification of malnutrition, and to improve the treatment for malnutrition.

A Long-Term Study of a Bicarbonate/Lactate-Based Peritoneal Dialysis Solution — Clinical Benefits

Objective

A bicarbonate/lactate peritoneal dialysis solution (Bic/Lac) has been developed based on in vitro and ex vivo data showing better preservation of cell function and correction of pain on infusion.

Design

This was a randomized, prospective, controlled, open-label study comparing a new 25 mmol/L bicarbonate/15 mmol/L lactate with a standard 40 mmol/L lactate-buffered peritoneal dialysis solution (Lac) over a 12-month treatment period.

Setting

17 European nephrology centers.

Patients

106 (70 Bic/Lac and 36 Lac) well-dialyzed continuous ambulatory peritoneal dialysis (CAPD) patients.

Interventions

Dialysis adequacy and peritoneal equilibration test (PET, week –4, months 3, 6, and 12); 24-hour ultrafiltration (week –4, months 1, 3, and 6); blood biochemistry (week –2, day 0, months 1, 2, 3,6, 9, and 12); and a product acceptability questionnaire (months 1 and 6).

Results

88 patients completed the first 6 months, and 44 the full year. The solutions were shown to be therapeutically equivalent with respect to plasma bicarbonate and peritoneal urea and creatinine clearances. Ultrafiltration in the Bic/Lac group increased significantly from baseline by about 150 mL/day for the whole of the 6-month treatment period ( p < 0.05). The biochemistry profile, adverse events, and physical examination (except body weight where there was a statistically significant increase in the Bic/Lac group) results did not differ significantly between the two groups. Reduced pain/discomfort on infusion or an increased sense of well-being was reported by 41% of patients on the Bic/Lac fluid.

Conclusions

The Bic/Lac solution is safe and effective in correcting uremic acidosis, provides relief of inflow pain/discomfort, and improves ultrafiltration and body weight.

Acidosis Correction with a new 25 Mmol/L Bicarbonate/15 Mmol/L Lactate Peritoneal Dialysis Solution

Objective

The aim of this study was to evaluate the effects of a combined 25 mmol/L bicarbonate/15 mmol/L lactate-based solution (Bic/Lac), compared to a 35 mmol/L lactate solution (Lac) — the most commonly used solution for patients in southern Europe — on the venous plasma bicarbonate level in patients treated with continuous ambulatory peritoneal dialysis (CAPD).

Design

This was a randomized, parallel, controlled, open-label study, with patients studied for a period of 3 months preceded by a 1-month baseline and followed by a 1-month follow-up. Patients used the 35 mmol/L lactate solution during baseline and follow-up periods.

Setting

Four Spanish nephrology centers.

Patients

Thirty-one (20 Bic/Lac, 11 Lac) well-dialyzed (creatinine clearance > 55 L/week/1.73 m2body surface area) CAPD patients.

Interventions

Blood samples were taken for biochemistry tests at all visits. A physical examination was completed at baseline and month 3, and a medical update was completed after 1, 2, and 3 months, and at the follow-up visit. Adverse-event monitoring and notation of prescription changes were carried out continuously.

Main Outcome Measure

Effect on venous plasma bicarbonate level.

Results

Venous plasma bicarbonate rose by 3.1 mmol/L (confidence intervals 1.6 – 4.8), from a baseline level of 23.0 mmol/L during the treatment period in those patients treated with Bic/Lac ( p < 0.05 vs Lac). The number of acidotic patients (venous plasma bicarbonate < 24 mmol/L) was statistically significantly reduced at every treatment period visit in the Bic/Lac group ( p < 0.05). There were no adverse findings with respect to vital signs, physical examination, or clinical symptoms, apart from one death in the control group.

Conclusions

The new Bic/Lac solution allowed better correction of acid–base status than the lactate solution.

Long-Term Clinical Experience with Pure Bicarbonate Peritoneal Dialysis Solutions

Objectives

The aim of this prospective study was to collect long-term experience in incident peritoneal dialysis (PD) patients treated with pure bicarbonate-buffered PD fluids.

Methods

The metabolic parameters acidosis, acid–base status, adequacy, fluid balance, nutritional markers, calcium, phosphorus, parathyroid hormone (PTH), and general laboratory work and medication were compared between incident PD patients in two groups: one treated with a 34 mmol/L bicarbonate-buffered PD fluid (BIC), the other with a 35 mmol/L lactate-buffered PD fluid (LAC). The observation period included 5 visits from 1 month (visit 1) until 12 months (visit 5) after the start of dialysis treatment. For the descriptive analysis, means and standard deviations were calculated. Student's t-test and linear mixed models were used to compare the two treatment groups.

Results

36 patients were followed for 12 months, 18 in the BIC group and 18 in the LAC group. Statistically significant differences between the groups (at the end of study) were found. In BIC group, venous plasma bicarbonate was 27.4 ± 2.3 mmol/L, base excess 0.8 ± 2.2 mmol/L, and pH 7.31 ± 0.05; in LAC group, venous bicarbonate was 25.9 ± 2.4 mmol/L, base excess –0.6 ± 2.1 mmol/L, and pH 7.30 ± 0.04. No patient from the BIC group needed oral bicarbonate, in contrast to 4 patients in the LAC group. Whereas peritoneal urea and creatinine clearances did not differ between the groups, there was better renal solute clearance in the BIC group, accompanied by better-preserved diuresis at 12 months (1333 ± 935 mL with BIC vs 839 ± 556 mL with LAC). The reverse was true for ultrafiltration.

Conclusions

Pure bicarbonate-buffered PD solutions were superior in correcting metabolic acidosis and they allowed omission of oral bicarbonate. The minor ultrafiltration with bicarbonate-buffered PD solutions was counterbalanced by better-preserved residual renal function with these solutions.

Impact of sarcopenia on long-term mortality and cardiovascular events in patients undergoing hemodialysis

BACKGROUND/AIMS

A high body mass index (BMI) is known to correlate with better survival in patients on hemodialysis (HD). However, the impacts of body composition and sarcopenia on survival have not been well studied in this population.

METHODS

One hundred and forty-two prevalent HD patients were recruited and followed prospectively for up to 4.5 years. Low muscle mass (measured using a portable, whole-body, bioimpedance spectroscopic device) was defined as a lean tissue index (LTI) two standard deviations (SD) or more below the normal gender-specific mean for young people. Low muscle strength was a handgrip strength (HGS) of less than 30 kg in males and less than 20 kg in females. Sarcopenia was considered present when both LTI and HGS were reduced.

RESULTS

The mean age was 59.8 ± 13.1 years; 57.0% were male and 47.2% had diabetes. Forty-seven patients (33.1%) had sarcopenia. During follow-up, 28 patients (19.7%) died, and low LTI (adjusted hazard ratio [HR], 2.77; 95% confidence interval [CI], 1.10 to 6.97) and low HGS (HR 5.65; 95% CI, 1.99 to 16.04) were independently associated with mortality. Sarcopenia was a significant predictor for death (HR, 6.99; 95% CI, 1.84 to 26.58; p = 0.004) and cardiovascular events (HR, 4.33; 95% CI, 1.51 to 12.43; p = 0.006).

CONCLUSION

Sarcopenia was strongly associated with long-term mortality and cardiovascular events in HD patients. Assessment of muscle strength and muscle mass may provide additional prognostic information to survival in patients with end-stage renal disease.

Effects of aging and comorbidities on nutritional status and muscle dysfunction in patients with COPD

Chronic obstructive pulmonary disease (COPD) is a prevalent, complex and debilitating disease which imposes a formidable burden on patients and the healthcare system. The recognition that COPD is a multifaceted disease is not new, and increasing evidence have outlined the importance of its extra-pulmonary manifestations and its relation to other comorbid conditions in the clinical course of the disease and its societal cost. The relationship between aging, COPD and its comorbidities on skeletal muscle function and nutritional status is complex, multidirectional and incompletely understood. Despite this, the current body of knowledge allows the identification of various, seemingly partially independent factors related both to the normal aging process and to the independent deleterious effects of chronic diseases on muscle function and body composition. There is a dire need of studies evaluating the relative contribution of each of these factors, and their potential synergistic effects in patients with COPD and advanced age/comorbid conditions, in order to delineate the best course of therapeutic action in this increasingly prevalent population.

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.

Metabolic Acidosis and Subclinical Metabolic Acidosis in CKD

Metabolic acidosis is not uncommon in CKD and is linked with bone demineralization, muscle catabolism, and higher risks of CKD progression and mortality. Clinical practice guidelines recommend maintaining serum total CO₂ at ≥22 mEq/L to help prevent these complications. Although a definitive trial testing whether correcting metabolic acidosis improves clinical outcomes has not been conducted, results from small, single-center studies support this notion. Furthermore, biologic plausibility supports the notion that a subset of patients with CKD have acid-mediated organ injury despite having a normal serum total CO₂ and might benefit from oral alkali before overt acidosis develops. Identifying these individuals with subclinical metabolic acidosis is challenging, but recent results suggest that urinary acid excretion measurements may be helpful. The dose of alkali to provide in this setting is unknown as well. The review discusses these topics and the prevalence and risk factors of metabolic acidosis, mechanisms of acid-mediated organ injury, results from interventional studies, and potential harms of alkali therapy in CKD.

Adverse Effects of the Metabolic Acidosis of Chronic Kidney Disease

The kidney has the principal role in the maintenance of acid-base balance, and therefore, a fall in renal net acid excretion and positive H⁺ balance often leading to reduced serum [HCO₃^-] are observed in the course of CKD. This metabolic acidosis can be associated with muscle wasting, development or exacerbation of bone disease, hypoalbuminemia, increased inflammation, progression of CKD, protein malnutrition, alterations in insulin, leptin, and growth hormone, and increased mortality. Importantly, some of the adverse effects can be observed even in the absence of overt hypobicarbonatemia. Administration of base decreases muscle wasting, improves bone disease, restores responsiveness to insulin, slows progression of CKD, and possibly reduces mortality. Base is recommended when serum [HCO₃^-] is <22 mEq/L, but the target serum [HCO₃^-] remains unclear. Evidence that increments of serum [HCO₃^-] >26 mEq/L might be associated with worsening of cardiovascular disease adds complexity to treatment decisions. Further study of the mechanisms through which positive H⁺ balance in CKD contributes to its various adverse effects and the pathways involved in mediating the benefits and complications of base therapy is warranted.

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.

Protein Nutrition and Malnutrition in CKD and ESRD

Elevated protein catabolism and protein malnutrition are common in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD). The underlying etiology includes, but is not limited to, metabolic acidosis intestinal dysbiosis; systemic inflammation with activation of complements, endothelin-1 and renin-angiotensin-aldosterone (RAAS) axis; anabolic hormone resistance; energy expenditure elevation; and uremic toxin accumulation. All of these derangements can further worsen kidney function, leading to poor patient outcomes. Many of these CKD-related derangements can be prevented and substantially reversed, representing an area of great potential to improve CKD and ESRD care. This review integrates known information and recent advances in the area of protein nutrition and malnutrition in CKD and ESRD. Management recommendations are summarized. Thorough understanding the pathogenesis and etiology of protein malnutrition in CKD and ESRD patients will undoubtedly facilitate the design and development of more effective strategies to optimize protein nutrition and improve outcomes.

Metabolic and Nutritional Aspects of Acute Renal Failure in Critically Ill Patients Requiring Continuous Renal Replacement Therapy

Acute renal failure (ARF) is rarely an isolated process but is often a complication of underlying conditions such as sepsis, trauma, and multiple-organ failure in critically ill patients. As such, concomitant clinical conditions significantly affect patient outcome. Poor nutritional status is a major factor in increasing patients' morbidity and mortality. Malnutrition in ARF patients is caused by hypercatabolism and hypermetabolism that parallel the severity of illness. When dialytic intervention is indicated, continuous renal replacement therapy (CRRT) is a commonly used alternative to intermittent hemodialysis because it is well tolerated by hemodynamically unstable patients. This paper reviews the metabolic and nutritional alterations associated with ARF and provides recommendations regarding the nutritional, fluid, electrolyte, micronutrient, and acid-base management of these patients. The basic principles of CRRT are addressed, along with their nutritional implications in critically ill patients. A patient case is presented to illustrate the clinical application of topics covered within the paper.

Con: Higher serum bicarbonate in dialysis patients is protective

Metabolic acidosis is often observed in advanced chronic kidney disease, with deleterious consequences on the nutritional status, bone and mineral status, inflammation and mortality. Through clearance of the daily acid load and a net gain in alkaline buffers, dialysis therapy is aimed at correcting metabolic acidosis. A normal bicarbonate serum concentration is the recommended target in dialysis patients. However, several studies have shown that a mild degree of metabolic acidosis in patients treated with dialysis is associated with better nutritional status, higher protein intake and improved survival. Conversely, a high bicarbonate serum concentration is associated with poor nutritional status and lower survival. It is likely that mild acidosis results from a dietary acid load linked to animal protein intake. In contrast, a high bicarbonate concentration in patients treated with dialysis could result mainly from an insufficient dietary acid load, i.e. low protein intake. Therefore, a high pre-dialysis serum bicarbonate concentration should prompt nephrologists to carry out nutritional investigations to detect insufficient dietary protein intake. In any case, a high bicarbonate concentration should be neither a goal of dialysis therapy nor an index of adequate dialysis, whereas mild acidosis could be considered as an indicator of appropriate protein intake.

Predialysis and Postdialysis pH and Bicarbonate and Risk of All-Cause and Cardiovascular Mortality in Long-term Hemodialysis Patients

BACKGROUND

To date, very few studies have been carried out on the associations of pre- and postdialysis acid-base parameters with mortality in hemodialysis patients.

STUDY DESIGN

An observational study including cross-sectional and 1-year analyses.

SETTING & PARTICIPANTS

Data from the renal registry of the Japanese Society of Dialysis Therapy (2008-2009), including 15,132 dialysis patients 16 years or older.

PREDICTOR

Predialysis pH<7.30, 7.30 to 7.34 (reference), 7.35 to 7.39, or ≥7.40 (1,550, 4,802, 6,023, and 2,757 patients, respectively); predialysis bicarbonate level < 18.0, 18.0 to 21.9 (reference), 22.0 to 25.9, or ≥26.0 mEq/L (2,724, 7,851, 4,023, and 534 patients, respectively); postdialysis pH<7.40, 7.40 to 7.44, 7.45 to 7.49 (reference), or ≥7.50 (2,114, 5,331, 4,975, and 2,712 patients, respectively); and postdialysis bicarbonate level < 24.0, 24.0 to 25.9, 26.0 to 27.9 (reference), or ≥28.0 mEq/L (5,087, 4,330, 3,451, and 2,264 patients, respectively).

OUTCOMES

All-cause and cardiovascular (CV) mortality during the 1-year follow-up.

MEASUREMENTS

HRs were estimated using unadjusted models and models adjusted for age, sex, dialysis vintage, history of CV disease, diabetes, weight gain ratio, body mass index, calcium-phosphorus product, serum albumin level, serum total cholesterol level, blood hemoglobin level, single-pool Kt/V, and normalized protein catabolic rate.

RESULTS

Of 15,132 patients, during follow-up, 1,042 died of all causes, including 408 CV deaths. In the adjusted analysis for all-cause mortality, HRs compared to the reference group were significantly higher in patients with predialysis pH≥7.40 (HR, 1.36; 95% CI, 1.13-1.65) and postdialysis pH<7.40 (HR, 1.22; 95% CI, 1.00-1.49). Predialysis pH≥7.40 was also associated with higher risk of CV mortality (HR, 1.34; 95% CI, 1.01-1.79). No association of pre- or postdialysis bicarbonate level with all-cause and CV mortality was observed.

LIMITATIONS

Single measurements of acid-base parameters, short duration of follow-up, small number of CV deaths.

CONCLUSIONS

Predialysis pH≥7.40 was associated with significantly elevated risk of all-cause and CV mortality. However, pre- and postdialysis bicarbonate levels were not associated with all-cause and CV mortality. Predialysis pH may be the most appropriate reference for accurate correction of metabolic acidosis in dialysis patients.

Current status of bicarbonate in CKD

Metabolic acidosis was one of the earliest complications to be recognized and explained pathologically in patients with CKD. Despite the accumulated evidence of deleterious effects of acidosis, treatment of acidosis has been tested very little, especially with respect to standard clinical outcomes. On the basis of fundamental research and small alkali supplementation trials, correcting metabolic acidosis has a strikingly broad array of potential benefits. This review summarizes the published evidence on the association between serum bicarbonate and clinical outcomes. We discuss the role of alkali supplementation in CKD as it relates to retarding kidney disease progression, improving metabolic and musculoskeletal complications.

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.

Low-frequency electrical stimulation attenuates muscle atrophy in CKD--a potential treatment strategy

Effective therapeutic strategies to treat CKD-induced muscle atrophy are urgently needed. Low-frequency electrical stimulation (LFES) may be effective in preventing muscle atrophy, because LFES is an acupuncture technique that mimics resistance exercise by inducing muscle contraction. To test this hypothesis, we treated 5/6-nephrectomized mice (CKD mice) and control mice with LFES for 15 days. LFES prevented soleus and extensor digitorum longus muscle weight loss and loss of hind-limb muscle grip in CKD mice. LFES countered the CKD-induced decline in the IGF-1 signaling pathway and led to increases in markers of protein synthesis and myogenesis and improvement in muscle protein metabolism. In control mice, we observed an acute response phase immediately after LFES, during which the expression of inflammatory cytokines (IFN-γ and IL-6) increased. Expression of the M1 macrophage marker IL-1β also increased acutely, but expression of the M2 marker arginase-1 increased 2 days after initiation of LFES, paralleling the change in IGF-1. In muscle cross-sections of LFES-treated mice, arginase-1 colocalized with IGF-1. Additionally, expression of microRNA-1 and -206, which inhibits IGF-1 translation, decreased in the acute response phase after LFES and increased at a later phase. We conclude that LFES ameliorates CKD-induced skeletal muscle atrophy by upregulation of the IGF-1 signaling pathway, which improves protein metabolism and promotes myogenesis. The upregulation of IGF-1 may be mediated by decreased expression of microRNA-1 and -206 and/or activation of M2 macrophages.

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.

A patient with CKD and poor nutritional status

Protein energy wasting is common in patients with CKD and ESRD and is associated with adverse clinical outcomes, such as increased rates of hospitalization and death, in these patients. A multitude of factors can affect the nutritional and metabolic status of patients with CKD, including decreased dietary nutrient intake, catabolic effects of renal replacement therapy, systemic inflammation, metabolic and hormonal derangements, and comorbid conditions (such as diabetes and depression). Unique aspects of CKD also confound reliable assessment of nutritional status, further complicating management of this comorbid condition. In patients in whom preventive measures and oral dietary intake from regular meals cannot help them maintain adequate nutritional status, nutritional supplementation, administered orally, enterally, or parenterally, is effective in replenishing protein and energy stores. The advantages of oral nutritional supplements include proven efficacy, safety, and compliance. Anabolic steroids and exercise, with nutritional supplementation or alone, improve protein stores and represent potential additional approaches for the treatment of PEW. There are several emerging novel therapies, such as appetite stimulants, anti-inflammatory interventions, and anabolic agents.

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.

Prevention and treatment of protein energy wasting in chronic kidney disease patients: a consensus statement by the International Society of Renal Nutrition and Metabolism

Protein energy wasting (PEW) is common in patients with chronic kidney disease (CKD) and is associated with adverse clinical outcomes, especially in individuals receiving maintenance dialysis therapy. A multitude of factors can affect the nutritional and metabolic status of CKD patients requiring a combination of therapeutic maneuvers to prevent or reverse protein and energy depletion. These include optimizing dietary nutrient intake, appropriate treatment of metabolic disturbances such as metabolic acidosis, systemic inflammation, and hormonal deficiencies, and prescribing optimized dialytic regimens. In patients where oral dietary intake from regular meals cannot maintain adequate nutritional status, nutritional supplementation, administered orally, enterally, or parenterally, is shown to be effective in replenishing protein and energy stores. In clinical practice, the advantages of oral nutritional supplements include proven efficacy, safety, and compliance. Anabolic strategies such as anabolic steroids, growth hormone, and exercise, in combination with nutritional supplementation or alone, have been shown to improve protein stores and represent potential additional approaches for the treatment of PEW. Appetite stimulants, anti-inflammatory interventions, and newer anabolic agents are emerging as novel therapies. While numerous epidemiological data suggest that an improvement in biomarkers of nutritional status is associated with improved survival, there are no large randomized clinical trials that have tested the effectiveness of nutritional interventions on mortality and morbidity.

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.