Effect of high-normal compared with low-normal arterial pH on protein balances in automated peritoneal dialysis patients

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.

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.

Understanding the Nutritional Needs of Healthy Cats and Those with Diet-Sensitive Conditions

Diets for cats must provide complete nutrition and meet the needs of the individual patient. There is no single diet that is perfect for all cats, and veterinarians must consider the needs of the cat as well as the preferences of the owners when making dietary recommendations. This article focuses on the interface between animal factors and nutritional needs in cats and is divided into 3 sections. Section 1 addresses the dietary needs of healthy cats, including differences among life stages. Section 2 addresses common myths regarding feline nutrition. Section 3 addresses common nutrient-sensitive conditions in cats, including sarcopenia of aging.

Controversies in Veterinary Nephrology: Renal Diets Are Indicated for Cats with International Renal Interest Society Chronic Kidney Disease Stages 2 to 4: The Con View

Renal diets typically incorporate protein and phosphorus restriction, supplement with potassium and Omega-3 fatty acids, and address metabolic acidosis. Compared to "maintenance" diets, these modifications appear to benefit cats with chronic kidney disease (CKD). However, there is limited data in cats justifying the specific amounts of the nutrients used in these diets, and there is little evidence supporting protein restriction in cats with CKD. Energy intake, maintenance of body weight, and muscle and body condition need to be addressed, and may take precedence over special diets. Further research is needed to better define optimum diets for cats with CKD.

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.

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.

Nutritional issues in peritoneal dialysis patients: how do they differ from that of patients undergoing hemodialysis?

It is important to understand the unique aspects vis-à-vis protein-energy wasting for patients undergoing PD. As a result of obligatory protein losses with the therapy, the serum albumin levels of patients undergoing PD are lower, as is the threshold serum albumin at which the risk for death is increased. Consequently, it is prudent to consider a lower threshold for serum albumin for the diagnosis of protein-energy wasting for patients undergoing PD. Likewise, it is important to consider the energy intake from obligatory nutrient absorption in the form of carbohydrates when estimating total energy intake (diet and dialysate) when evaluating patients for protein-energy wasting. The continuous nature of PD also has important therapeutic implications for protein-energy wasting. Such patients are more likely to have a complete correction of metabolic acidosis, and glucose absorption from the peritoneal dialysate has a protein-sparing effect, allowing some patients to maintain neutral nitrogen balances in the face of suboptimal protein intake. In contrast, clinical trials of amino-acid-based PD solutions have not met expectations and cannot be recommended for routine use for treatment of protein-energy wasting. In conclusion, it is important to consider these unique nutritional considerations when providing care to patients undergoing PD.

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.

Dialysis modality and correction of uremic metabolic acidosis: relationship with all-cause and cause-specific mortality

BACKGROUND AND OBJECTIVES

Uremic metabolic acidosis is only partially corrected in many hemodialysis patients, and low serum bicarbonate predicts higher death risk. This study determined the comparative efficacy of peritoneal dialysis in correcting uremic metabolic acidosis and the association of serum bicarbonate and death risk with the two therapies.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Data were obtained from 121,351 prevalent ESRD patients (peritoneal dialysis, 10,400; hemodialysis, 110,951) treated in DaVita facilities between July 1, 2001 and June 30, 2006, with follow-up through June of 2007.

RESULTS

Serum bicarbonate was <22 mEq/L in 25% and 40% of peritoneal dialysis and hemodialysis patients, respectively. Thus, peritoneal dialysis patients were substantially less likely to have lower serum bicarbonate (adjusted odds ratio<20 mEq/L, 0.45 [0.42, 0.49]; <22 mEq/L, 0.41 [0.39, 0.43]). Time-averaged serum bicarbonate<19 mEq/L was associated with an 18% and 25% higher risk for all-cause and cardiovascular mortality, respectively, in prevalent peritoneal dialysis patients (reference group: serum bicarbonate between 24 and <25 mEq/L). In analyses using the entire cohort of peritoneal dialysis and hemodialysis patients, the adjusted risk for all-cause mortality was higher in most subgroups with serum bicarbonate<22 mEq/L, irrespective of dialysis modality.

CONCLUSIONS

The measured bicarbonate is significantly higher in peritoneal dialysis patients, suggesting that the therapy provides a more complete correction of metabolic acidosis than intermittent hemodialysis. Survival data suggest maintaining serum bicarbonate>22 mEq/L for all ESRD patients, irrespective of dialysis modality.

Daily dietary energy and macronutrient intake and anthropometric measurements of the peritoneal dialysis patients

INTRODUCTION

This study was planned to investigate the relation between dietary macronutrient status and anthropometric measurements in peritoneal dialysis (PD) patients.

MATERIALS AND METHODS

A total of 28 clinically stable patients were enrolled in this study. All patients were taken a dietary therapy according to the guidelines of the American Journal of Kidney Foundation for 12 weeks. The anthropometric measurements were taken by bioelectrical impedance analyzer. The daily macronutrient intakes of the patients were calculated by the food consumption records.

RESULTS

The mean age was 48.3 ± 13.10 years [56.3 ± 7.41 years for males (n = 14) and 40.3 ± 12.84 years for females (n = 14)]. There were significant changes in fat percentage (%), total body water (TBW; %, L), extracellular water (ECW; %, L), basal metabolic rate over body weight (BMR/BW), and body fat mass index (BMFI) in males (p < 0.05), but there was no change in females (p > 0.05). The daily dietary energy and protein intakes were under the recommended level in the study period.

CONCLUSION

Patients undergoing PD frequently have low intakes of protein and energy. It is recommended that individuals undergoing PD periodically maintain 3-day dietary records followed by dietary interviews conducted by a dietitian.

High-flux versus low-flux membranes for end-stage kidney disease

BACKGROUND

Clinical practice guidelines regarding the use of high-flux haemodialysis membranes vary widely.

OBJECTIVES

We aimed to analyse the current evidence reported for the benefits and harms of high-flux and low-flux haemodialysis.

SEARCH METHODS

We searched Cochrane Renal Group's specialised register (July 2012), the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (1948 to March 2011), and EMBASE (1947 to March 2011) without language restriction.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) that compared high-flux haemodialysis with low-flux haemodialysis in people with end-stage kidney disease (ESKD) who required long-term haemodialysis.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two authors for study characteristics (participants and interventions), risks of bias, and outcomes (all-cause mortality and cause-specific mortality, hospitalisation, health-related quality of life, carpal tunnel syndrome, dialysis-related arthropathy, kidney function, and symptoms) among people on haemodialysis. Treatment effects were expressed as a risk ratio (RR) or mean difference (MD), with 95% confidence intervals (CI) using the random-effects model.

MAIN RESULTS

We included 33 studies that involved 3820 participants with ESKD. High-flux membranes reduced cardiovascular mortality (5 studies, 2612 participants: RR 0.83, 95% CI 0.70 to 0.99) but not all-cause mortality (10 studies, 2915 participants: RR 0.95, 95% CI 0.87 to 1.04) or infection-related mortality (3 studies, 2547 participants: RR 0.91, 95% CI 0.71 to 1.14). In absolute terms, high-flux membranes may prevent three cardiovascular deaths in 100 people treated with haemodialysis for two years. While high-flux membranes reduced predialysis beta-2 microglobulin levels (MD -12.17 mg/L, 95% CI -15.83 to -8.51 mg/L), insufficient data were available to reliably estimate the effects of membrane flux on hospitalisation, carpal tunnel syndrome, or amyloid-related arthropathy. Evidence for effects of high-flux membranes was limited by selective reporting in a few studies. Insufficient numbers of studies limited our ability to conduct subgroup analyses for membrane type, biocompatibility, or reuse. In general, the risk of bias was either high or unclear in the majority of studies.

AUTHORS' CONCLUSIONS

High-flux haemodialysis may reduce cardiovascular mortality in people requiring haemodialysis by about 15%. A large well-designed RCT is now required to confirm this finding.

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.

Optimizing bone health in chronic kidney disease

Phosphocalcic metabolism disorders often complicate chronic kidney disease (CKD) and worsen as kidney function declines, with a consequence on bone structural integrity. The risk of fracture exceeds that of the normal population in both patients with pre-dialysis CKD and end-stage renal disease (ESRD). The increasing incidence of CKD, the high mortality rate induced by hip fracture, the decreased quality of life and economic burden of fragility fracture make the renal bone disorders a major problem of public health around the world. Optimizing bone health in CKD patients should be a priority. Bone biopsy is invasive. Dual-energy X-ray absorptiometry, commonly used to screen individuals at risk of fragility fracture in the general population, is not adequate to assess advanced CKD because it does not discriminate fracture status in this population. New non-invasive three-dimensional high-resolution imaging techniques, distinguishing trabecular and cortical bone, appear to be promising in the assessment of bone strength and might improve bone fracture prediction in this population. Therapeutic intervention in the chronic kidney disease-mineral and bone disorders (CKD-MBD) should begin early in the course of CKD to maintain serum concentration of biological parameters involved in mineral metabolism in the normal recommended ranges, prevent the development of parathyroid hyperplasia, prevent extra-skeletal calcifications and preserve skeletal health. In this paper, we review studies of mineral and bone disorders in patients with CKD and ESRD, the utility of current techniques to assess bone health and the preventive and therapeutic strategies for managing CKD-MBD.