Metabolic acidosis in maintenance dialysis patients: clinical considerations

Preventing potential pitfalls of a liberalized potassium diet in the hemodialysis population

Emerging research suggests that a more liberalized diet, specifically a more plant-based diet resulting in liberalization of potassium intake, for people receiving hemodialysis is necessary and the benefits outweigh previously thought risks. If the prescribed hemodialysis diet is to be liberalized, the need to illuminate and prevent potential pitfalls of a liberalized potassium diet is warranted. This paper explores such topics as partial to full adherence to a liberalized diet and its consequences if any, the advantages of a high-fiber intake, the theoretical risk of anemia when consuming a more plant-dominant diet, the potential benefits against renal acid load and effect on metabolic acidosis with increased fruit and vegetable intake, the putative change in serum potassium levels, carbohydrate quality, and the healthfulness of meat substitutes. The benefits of a more plant-based diet for the hemodialysis population are multifold; however, the possible pitfalls of this type of diet must be reviewed and addressed upon meal planning in order to be avoided.

Profound metabolic acidosis in association with sodium thiosulfate therapy in a patient with calcific uremic arteriolopathy: a case report and literature review

Calciphylaxis, also known as Calcific uremic arteriolopathy (CUA), is a serious disorder that presents with skin necrosis due to calcification of dermal and subcutaneous adipose tissue capillaries and arterioles. The condition occurs primarily in patients with end-stage renal disease (ESRD) on dialysis, and it carries high morbidity and mortality, primarily due to sepsis, with an estimated six-month survival of approximately 50%. Although there are no high-quality studies to guide the optimal treatment approach for patients with calciphylaxis, many retrospective studies and case series support treatment with sodium thiosulfate (STS). Despite the frequent use of STS as an off-label treatment, data regarding its safety and efficacy are limited. STS has generally been considered a safe drug with mild side effects. However, severe metabolic acidosis associated with STS is a rare and life-threatening complication of STS treatment and is often unpredictable. Herein, we report a 64-year-old female with ESRD on peritoneal dialysis (PD) who presented with a profound high anion gap metabolic acidosis and severe hyperkalemia while on STS treatment for CUA. No other etiology for her severe metabolic acidosis other than STS was identified. ESRD patients receiving STS should be monitored closely for this side effect. Dose reduction, increasing the duration of infusion, or even discontinuing STS treatment should be considered if severe metabolic acidosis develops.

Water quality and adverse health effects on the hemodialysis patients: An overview

Hemodialysis is considered a treatment of choice for patients with renal failure worldwide, allowing the replacement of some kidney functions by diffusion and ultrafiltration processes. Over 4 million people require some form of renal replacement therapy, with hemodialysis being the most common. During the procedure, contaminants in the water and the resulting dialysate may pass into the patient's blood and lead to toxicity. Thus, the quality of the associated dialysis solutions is a critical issue. Accordingly, the discussion of the importance of a dialysis water delivery system controlled by current standards and recommendations, with efficient monitoring methods, disinfection systems, and chemical and microbiological analysis, is crucial for improving the health outcomes of these patients. The importance of treatment, monitoring, and regulation is emphasized by presenting several case studies concerning the contamination of hemodialysis water and the adverse effects on the respective patients.

A Counterion-Free Strategy for Chronic Metabolic Acidosis Based on an Orally Administered Gut-Restricted Inorganic Adsorbent

Chronic metabolic acidosis, arising as a complication of chronic kidney disease (CKD), not only reduces patients' quality of life but also aggravates renal impairment. The only available therapeutic modality, involving intravenous infusion of NaHCO3 , engenders undesirable sodium retention, thereby increasing hemodynamic load and seriously exacerbating the primary disease. This deleterious cascade extends to the development of cardiovascular diseases. Herein, an orally administered, gut-restricted inorganic adsorbent that can effectively alleviate chronic metabolic acidosis without causing any electrolytic derangement or superfluous cardiovascular strain is developed. The genesis of ABC-350 entails the engineering of bismuth subcarbonate via annealing, thereby yielding a partially β-Bi2 O3 -doped (BiO)2 CO3 biphasic crystalline structure framework enriched with atomic vacancies. ABC-350 can selectively remove chloride ions and protons from the gastrointestinal tract, mimicking the physiological response to gastric acid removal and resulting in increased serum bicarbonate. Owing to its gut-restricted nature, ABC-350 exhibits commendable biosafety, averting undue systemic exposure. In two rat models of metabolic acidosis, ABC-350 emerges not only as a potent mitigator of acidosis but also effects discernible amelioration concerning proximal tubular morphology, interstitial fibrosis, and the incendiary cascades incited by metabolic acidosis. ABC-350, as the translationally relevant material, provides a promising strategy for the treatment of metabolic acidosis.

Point-of-Care Testing to Differentiate Various Acid-Base Disorders in Chronic Kidney Disease

BACKGROUND

Normal-anion-gap metabolic acidosis (AGMA) and high-anion-gap metabolic acidosis (HAGMA) are two forms of metabolic acidosis, which is a common complication in patients with chronic kidney disease (CKD). The aim of this study is to identify the prevalence of various acid-base disorders in patients with advanced CKD using point-of-care testing (POCT) and to determine the relationship between POCT parameters.

METHODS

In a group of 116 patients with CKD in stages G4 and G5, with a mean age of 62.5 ± 17 years, a sample of arterial blood was taken during the arteriovenous fistula procedure for POCT, which enables an assessment of the most important parameters of acid-base balance, including: pH, base excess (BE), bicarbonate (HCO3-), chloride(Cl-), anion gap (AG), creatinine and urea concentration. Based on this test, patients were categorized according to the type of acidosis-base disorder.

RESULTS

Decompensate acidosis with a pH < 7.35 was found in 68 (59%) patients. Metabolic acidosis (MA), defined as the concentration of HCO3- ≤ 22 mmol/L, was found in 92 (79%) patients. In this group, significantly lower pH, BE, HCO3- and Cl- concentrations were found. In group of MA patients, AGMA and HAGMA was observed in 48 (52%) and 44 (48%) of patients, respectively. The mean creatinine was significantly lower in the AGMA group compared to the HAGMA group (4.91 vs. 5.87 mg/dL, p < 0.05). The AG correlated positively with creatinine (r = 0.44, p < 0.01) and urea (r = 0.53, p < 0.01), but there was no correlation between HCO3- and both creatinine (r = -0.015, p > 0.05) and urea (r = -0.07, p > 0.05). The Cl- concentrations correlated negatively with HCO3- (r = -0.8, p < 0.01).

CONCLUSIONS

The most common type of acid-base disturbance in CKD patients in stages 4 and 5 is AGMA, which is observed in patients with better kidney function and is associated with compensatory hyperchloremia. The initiation of renal replacement therapy was significantly earlier for patients diagnosed with HAGMA compared to those diagnosed with AGMA. The more advanced the CKD, the higher the AG.

A Novel Approach for Managing Protein-Energy Wasting in People With Kidney Failure Undergoing Maintenance Hemodialysis: Rationale and Call for Trials

Protein-energy wasting (PEW) is a unique presentation of protein-energy malnutrition in people with kidney disease that is characterized by body protein catabolism exceeding anabolism. PEW is especially common in patients undergoing maintenance hemodialysis (HD) treatment. Dietary guidelines for managing PEW in HD patients primarily focus on protein adequacy and typically promote the intake of animal-based protein foods. Although intake of protein and essential amino acids is important for protein synthesis, the emphasis on protein adequacy largely fails to address-and may actually exacerbate-many of the root causes of PEW. This perspective examines the dietary determinants of PEW in people undergoing HD treatment, with an emphasis on upstream disease-related factors that reduce dietary protein utilization and impair dietary intakes. From this, we present a theoretical diet model for managing PEW that includes etiology-based dietary strategies to address barriers to intake and treat disease-related factors, as well as supportive dietary strategies to promote adequate energy and protein intakes. Given the complexity of diet-disease interactions in the pathogenesis of PEW, and its ongoing burden in HD patients, interventional trials are urgently needed to evaluate alternative diet therapy approaches for PEW in this population.

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.

Hemodiafiltration Improves Low Levels of Health-Related Quality Of Life (Qol) and Nutritional Conditions of Hemodialysis Patients

We compared the effects on the nutritional condition and health-related quality of life (HR-QoL) of the treatment of patients with on-line hemodiafiltration (OL-HDF) and conventional hemodialysis (CHD) using a superflux dialyzer. In total, 47 maintenance (M) HD patients were treated by CHD with a high-flux dialyzer for the first 4 months (1st CHD) and were then switched to predilution OL-HDF for the next 4 months (OL-HDF), after which CHD was resumed for the last 4 months (2nd CHD). We assessed the clinical parameters, fat mass value, muscle mass value, and HR-QoL. In patients with low serum albumin levels, these levels significantly (p < 0.05) increased in the OL-HDF period. Moreover, the fat mass values significantly (p < 0.05) increased in patients with decreased fat mass values in the OL-HDF period. Although there was no significant difference in the patients with higher scores of physical functioning, role physical, vitality, and social functioning, patients with lower scores in the 1st CHD period had significantly increased (p < 0.05) in the OL-HDF period. In this crossover study, we revealed that OL-HDF treatment significantly improved the nutritional conditions and HR-QoL scores compared with the improvement observed after CHD with a superflux dialyzer, especially for maintenance hemodialysis patients with malnutrition and a low QoL.

The Effects of Oral Sodium Bicarbonate on Renal Function and Cardiovascular Risk in Patients with Chronic Kidney Disease: A Systematic Review and Meta-Analysis

OBJECTIVE

Oral sodium bicarbonate is often used to correct acid-base disturbance in patients with chronic kidney disease (CKD). However, there is little evidence on patient-level benign outcomes to support the practice.

METHODS

We conducted a systematic review and meta-analysis to examine the efficacy and safety of oral sodium bicarbonate in CKD patients. A total of 1853 patients with chronic metabolic acidosis or those with low-normal serum bicarbonate (22-24 mEq/L) were performed to compare the efficacy and safety of oral sodium bicarbonate in patients with CKD.

RESULTS

There was a significant increase in serum bicarbonate level (MD 2.37 mEq/L; 95% CI, 1.03 to 3.72) and slowed the decline in estimated glomerular filtration rate (eGFR) (MD -4.44 mL/min per 1.73 m2, 95% CI, -4.92 to -3.96) compared with the control groups. The sodium bicarbonate lowered T50-time, an indicator of vascular calcification (MD -20.74 min; 95% CI, -49.55 to 8.08); however, there was no significant difference between the two groups. In addition, oral sodium bicarbonate dramatically reduced systolic blood pressure (MD -2.97 mmHg; 95% CI, -5.04 to -0.90) and diastolic blood pressure (MD -1.26 mmHg; 95% CI, -2.33 to -0.19). There were no statistically significant body weight, urine pH and mean mid-arm muscle circumference.

CONCLUSION

Treatment of metabolic acidosis with sodium bicarbonate may slow the decline rate of kidney function and potentially significantly improve vascular endothelial function in patients with CKD.

PROSPERO REGISTRATION NUMBER

CRD42020207185.

Muscle-bone axis in children with chronic kidney disease: current knowledge and future perspectives

Bone and muscle tissue are developed hand-in-hand during childhood and adolescence and interact through mechanical loads and biochemical pathways forming the musculoskeletal system. Chronic kidney disease (CKD) is widely considered as both a bone and muscle-weakening disease, eventually leading to frailty phenotype, with detrimental effects on overall morbidity. CKD also interferes in the biomechanical communication between two tissues. Pathogenetic mechanisms including systemic inflammation, anorexia, physical inactivity, vitamin D deficiency and secondary hyperparathyroidism, metabolic acidosis, impaired growth hormone/insulin growth factor 1 axis, insulin resistance, and activation of renin-angiotensin system are incriminated for longitudinal uncoordinated loss of bone mineral content, bone strength, muscle mass, and muscle strength, leading to mechanical impairment of the functional muscle-bone unit. At the same time, CKD may also interfere in the biochemical crosstalk between the two organs, through inhibiting or stimulating the expression of certain osteokines and myokines. This review focuses on presenting current knowledge, according to in vitro, in vivo, and clinical studies, concerning the pathogenetic pathways involved in the muscle-bone axis, and suggests approaches aimed at preventing bone loss and muscle wasting in the pediatric population. Novel therapeutic targets for preserving musculoskeletal health in the context of CKD are also discussed.

Metabolic Acidosis in Chronic Kidney Disease: Pathogenesis, Clinical Consequences, and Treatment

The kidneys play an important role in regulating the acid-base balance. Metabolic acidosis is common in chronic kidney disease (CKD) patients and can lead to poor outcomes, such as bone demineralization, muscle mass loss, and worsening of renal function. Metabolic acidosis is usually approached with evaluating the serum bicarbonate levels but should be assessed by counting blood pH. Current guidelines recommend oral bicarbonate supplementation to maintain the serum bicarbonate levels within the normal range. However, a slow decline in the glomerular filtration rate might occur, even though the serum bicarbonate levels were in the normal range. Because the serum bicarbonate levels decrease when metabolic acidosis advances, other biomarkers are necessary to indicate acid retention for early diagnosis of metabolic acidosis. For this, urine citrate and ammonium excretion may be used to follow the course of CKD patients. Metabolic acidosis can be treated with an increased fruit and vegetable intake and oral alkali supplementation. Previous studies have suggested that administration of oral sodium bicarbonate may preserve kidney function without significant increases in blood pressure and body weight. Veverimer, a non-absorbed, counterion-free, polymeric drug, is emerging to treat metabolic acidosis, but further researches are awaited. Further studies are also needed to clarify the target therapeutic range of serum bicarbonate and the drugs used for metabolic acidosis.

A four-stream method for providing variable dialysis fluid bicarbonate concentrations for bicarbonate-based dialysis fluid delivery systems

BACKGROUND

Hemodialysis corrects metabolic acidosis by transferring bicarbonate or bicarbonate equivalents across the dialysis membrane from the dialysis fluid to the plasma. With the conventional three-stream bicarbonate-based dialysis fluid delivery system, a change in the bicarbonate concentration results in changes in the other electrolytes. In practice, the dialysis machine draws either a little less or more from the bicarbonate concentrate and a little more or less from the acid concentrate, respectively in a three-stream delivery system. The result not only changes the bicarbonate concentration of the final dialysis fluid but also causes a minor change in the other ingredients.

METHODS

We propose a four-stream bicarbonate-based dialysis fluid delivery system consisting of an acid concentrate, a base concentrate, a product water, and a new sodium chloride concentrate.

RESULTS

By adjusting the flow rate ratio between the sodium chloride and sodium bicarbonate concentrates, one can achieve the desired bicarbonate concentration in the dialysis fluid without changing the concentration of sodium or ingredients in the acid concentrate. The chloride concentration mirrors the change in bicarbonate but in the opposite direction.

CONCLUSION

A four-stream, bicarbonate-based dialysis fluid delivery system allows the bicarbonate concentration to be changed without changing the other constituents of the final dialysis fluid.

Randomized comparison of three high-flux dialyzers during high-volume online hemodiafiltration—the comPERFORM study

Background

Dialyzers should be designed to efficiently eliminate uraemic toxins during dialysis treatment, given that the accumulation of small and middle molecular weight uraemic solutes is associated with increased mortality risk of patients with end-stage renal disease. In the present study we investigated the novel FX CorAL dialyzer with a modified membrane surface for performance during online hemodiafiltration (HDF) in a clinical setting.

Methods

comPERFORM was a prospective, open, controlled, multicentric, interventional, crossover study with randomized treatment sequences. It randomized stable patients receiving regular post-dilution online HDF to FX CorAL 600 (Fresenius Medical Care Deutschland), xevonta Hi 15 (B. Braun) and ELISIO 150H (Nipro) each for 1 week. The primary outcome was β2-m removal rate (β2-m RR) during online HDF. Secondary endpoints were RR and/or clearance of β2-m and other molecules. Albumin removal over time was an exploratory endpoint. Non-inferiority and superiority of FX CorAL 600 versus comparators were tested.

Results

Fifty-two patients were included and analysed. FX CorAL 600 showed the highest β2-m RR (75.47%), followed by xevonta Hi 15 (74.01%) and ELISIO 150H (72.70%). Superiority to its comparators was statistically significant (P = 0.0216 and P < 0.0001, respectively). Secondary endpoints related to middle molecules affirmed these results. FX CorAL 600 demonstrated the lowest albumin removal up to 60 minutes and its sieving properties changed less over time than with comparators.

Conclusions

FX CorAL 600 efficiently removed middle and small molecules and was superior to the two comparators in β2-m RR. Albumin sieving kinetics point to reduced formation of a secondary membrane.

A Pilot Study of the Safety and Efficacy of Alkali Therapy on Vascular Function in Kidney Transplant Recipients

Introduction

Metabolic acidosis is associated with cardiovascular events, graft function, and mortality in kidney transplant recipients (KTRs). We examined the effect of alkali therapy on vascular endothelial function in KTRs.

Methods

We performed an 18-week, randomized, double-blind, placebo-controlled crossover pilot study examining the effect of sodium bicarbonate therapy versus placebo on vascular function in 20 adult KTRs at least 1 year from transplant with an estimated glomerular filtration rate (eGFR) ≥45 ml/min per 1.73 m² and a serum bicarbonate level of 20 to 26 mEq/L. Each treatment period was 8 weeks in duration with a 2-week washout period between treatments. The primary outcome was change in brachial artery flow-mediated dilation (FMD) between sodium bicarbonate treatment and placebo.

Results

Twenty patients completed the study and were included in the primary analysis. The mean (SD) baseline eGFR of participants was 75 (22) ml/min per 1.73 m², respectively. Serum bicarbonate levels did not increase significantly with treatment (0.3 [1.5] mEq/L, P = 0.37). Sodium bicarbonate therapy was not associated with worsening blood pressure, weight gain, or hypokalemia. There was no significant increase in FMD after 8 weeks of sodium bicarbonate therapy compared to placebo (mean change in FMD 2.2%, 95% CI -0.1 to 4.6, P = 0.06). There were no significant changes in high-sensitivity C-reactive protein, interleukin-6, eGFR, or urinary albumin-to-creatinine ratio during treatment. Urinary ammonium excretion decreased by 9 mmol/d (P=0.003), with sodium bicarbonate.

Conclusions

Sodium bicarbonate therapy is safe and feasible in KTRs, and our results strengthen the need for a larger randomized controlled trial.

Study on the Application and Efficacy of Responsibility Nursing in Dialysis Care

Providing high-quality care to patients undergoing hemodialysis (HD) is a priority for nurses. The present study was conducted to explore the experiences of the quality of nursing care among patients, nurses, and caregivers in Yanghu Branch of Changzhou Second People's Hospital, China. A total of 120 hemodialysis patients consecutively admitted to Yanghu Branch of Changzhou Second People's Hospital were enrolled and divided into two groups according to the nursing method they received: control group (routine nursing) and experimental group (responsibility nursing). The two cohorts were observed and compared for alterations of adverse emotions and inflammatory factors, the incidence of complications, pre-and post-nursing sleep quality, life quality, and patients' satisfaction with nursing. After nursing, the Self-Rating Anxiety/Depression Scale (SAS/DS) scores were lower in the experimental group (EG) than in the control group (CG) (both P < 0.05). Serum IL-6, hs-CRP, and TNF-α were decreased in both groups after nursing and were even lower in EG (both P < 0.05). EG had significantly improved sleep quality and life quality than CG, with a higher nursing satisfaction (all P < 0.05). This validates that the responsibility nursing for dialysis patients can validly mitigate patients' negative emotions, improve their quality of life, and ensure high-quality dialysis effect, which is feasible for wide popularization and application in clinics.

Incidence of Uncommon Clinical Events in USA Patients with Dialysis-Dependent and Nondialysis-Dependent Chronic Kidney Disease: Analysis of Electronic Health Records from TriNetX

INTRODUCTION

Further understanding of adverse clinical events in patients with chronic kidney disease (CKD) is needed. This study aimed to describe characteristics of patients with nondialysis-dependent (NDD) and dialysis-dependent (DD) CKD and to assess incidence rates of uncommon adverse clinical events of interest in these patients.

METHODS

This retrospective study used electronic medical record data from USA CKD patients (≥18 years) with estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m2 between January 1, 2010, and December 31, 2018, obtained from the USA-based TriNetX database. NDD-CKD and DD-CKD were diagnosed and staged from ≥2 consecutive eGFR readings, recorded ≥90 days apart. Dialysis was identified using procedure codes for renal replacement therapy. Outcomes assessed were select uncommon adverse clinical events, defined by International Classification of Disease, 9th and 10th Revision codes.

RESULTS

Incidence rates of adverse clinical events per 100 person-years (95% confidence interval) were generally higher in patients with DD-CKD versus NDD-CKD. Differences were particularly pronounced for hyperkalemia (26.9 [26.2-27.6] vs. 4.5 [4.5-4.6]), acidosis (15.1 [14.7-15.6] vs. 3.4 [3.4-3.4]), and sepsis (14.6 [14.2-15.1] vs. 3.3 [3.3-3.4]). Among DD-CKD patients, incidence rates of adverse events were particularly high during the first 3 months following dialysis initiation. Incidence of adverse clinical events generally increased with decreasing eGFR among patients with NDD-CKD and with hemoglobin <10 g/dL in both NDD- and DD-CKD patients.

CONCLUSIONS

Our results help establish baseline rates of uncommon adverse clinical events and provide additional evidence of increased morbidity for patients with DD-CKD versus NDD-CKD.

High ankle-brachial index predicts cardiovascular events and mortality in hemodialysis patients with severe secondary hyperparathyroidism

Introduction:

Vascular calcification related to severe secondary hyperparathyroidism (SHPT) is an important cause of cardiovascular and bone complications, leading to high morbidity and mortality in patients with chronic kidney disease (CKD) undergoing hemodialysis (HD). The present study aimed to analyze whether ankle-brachial index (ABI), a non-invasive diagnostic tool, is able to predict cardiovascular outcomes in this population.

Methods:

We selected 88 adult patients on HD for at least 6 months, with serum iPTH>1,000pg/mL. We collected clinical data, biochemical and hormonal parameters, and ABI (sonar-Doppler). Calcification was assessed by lateral radiography of the abdomen and by simple vascular calcification score (SVCS). This cohort was monitored prospectively between 2012 and 2019 for cardiovascular outcomes (death, myocardial infarction (MI), stroke, and calciphylaxis) to estimate the accuracy of ABI in this setting.

Results:

The baseline values were: iPTH: 1770±689pg/mL, P: 5.8±1.2 mg/dL, corrected Ca: 9.7±0.8mg/dL, 25(OH)vit D: 25.1±10.9ng/mL. Sixty-five percent of patients had ABI>1.3 (ranging from 0.6 to 3.2); 66% had SVCS≥3, and 45% aortic calcification (Kauppila≥8). The prospective evaluation (51.6±24.0 months), provided the following cardiovascular outcomes: 11% of deaths, 17% of nonfatal MI, one stroke, and 3% of calciphylaxis. After adjustments, patients with ABI≥1.6 had 8.9-fold higher risk of cardiovascular events (p=0.035), and ABI≥1.8 had 12.2-fold higher risk of cardiovascular mortality (p=0.019).

Conclusion:

The presence of vascular calcifications and arterial stiffness was highly prevalent in our population. We suggest that ABI, a simple and cost-effective diagnostic tool, could be used at an outpatient basis to predict cardiovascular events in patients with severe SHPT undergoing HD.

Understanding Development of Malnutrition in Hemodialysis Patients: A Narrative Review

Hemodialysis (HD) majorly represents the global treatment option for patients with chronic kidney disease stage 5, and, despite advances in dialysis technology, these patients face a high risk of morbidity and mortality from malnutrition. We aimed to provide a novel view that malnutrition susceptibility in the global HD community is either or both of iatrogenic and of non-iatrogenic origins. This categorization of malnutrition origin clearly describes the role of each factor in contributing to malnutrition. Low dialysis adequacy resulting in uremia and metabolic acidosis and dialysis membranes and techniques, which incur greater amino-acid losses, are identified modifiable iatrogenic factors of malnutrition. Dietary inadequacy as per suboptimal energy and protein intakes due to poor appetite status, low diet quality, high diet monotony index, and/or psychosocial and financial barriers are modifiable non-iatrogenic factors implicated in malnutrition in these patients. These factors should be included in a comprehensive nutritional assessment for malnutrition risk. Leveraging the point of origin of malnutrition in dialysis patients is crucial for healthcare practitioners to enable personalized patient care, as well as determine country-specific malnutrition treatment strategies.

Hyperlipidemia and Statins Use for the Risk of New Diagnosed Sarcopenia in Patients with Chronic Kidney: A Population-Based Study

Background: Previous research found that statins, in addition to its efficiency in treating hyperlipidemia, may also incur adverse drug reactions, which mainly include myopathies and abnormalities in liver function. Aim: This study aims to assess the risk for newly onset sarcopenia among patients with chronic kidney disease using statins. Material and Method: In a nationwide retrospective population-based cohort study, 75,637 clinically confirmed cases of chronic kidney disease between 1997 and 2011were selected from the National Health Insurance Research Database of Taiwan. The selection of the chronic kidney disease cohort included a discharge diagnosis with chronic kidney disease or more than 3 outpatient visits with the diagnosis of chronic kidney disease found within 1 year. After consideration of patient exclusions, we finally got a total number of 67,001 cases of chronic kidney disease in the study. The Cox proportional hazards model was used to perform preliminary analysis on the effect of statins usage on the occurrence of newly diagnosed sarcopenia; the Cox proportional hazards model with time-dependent covariates was conducted to take into consideration the individual temporal differences in medication usage, and calculated the hazard ratio (HR) and 95% confidence interval after controlling for gender, age, income, and urbanization. Results: Our main findings indicated that patients with chronic kidney disease who use statins seem to effectively prevent patients from occurrences of sarcopenia, high dosage of statins seem to show more significant protective effects, and the results are similar over long-term follow-up. In addition, the risk for newly diagnosed sarcopenia among patients with lipophilic statins treatment was lower than that among patients with hydrophilic statins treatment. Conclusion: It seems that patients with chronic kidney disease could receive statin treatment to reduce the occurrence of newly diagnosed sarcopenia. Additionally, a higher dosage of statins could reduce the incidence of newly diagnosed sarcopenia in patients with chronic kidney disease.

Effect of Treatment of Metabolic Acidosis on Vascular Endothelial Function in Patients with CKD: A Pilot Randomized Cross-Over Study

BACKGROUND AND OBJECTIVES

We examined the effect of alkali replacement for metabolic acidosis on vascular endothelial function in patients with CKD.

METHODS

We performed a pilot, prospective, open-label 14-week crossover study examining the effect of oral sodium bicarbonate treatment on vascular function in 20 patients with an eGFR of 15-44 ml/min per 1.73 m2 with low serum bicarbonate levels (16-21 mEq/L). Each period was 6 weeks in duration with a 2-week washout period in between. Patients were treated to goal serum bicarbonate of ≥23 mEq/L. The primary end point was change in brachial artery flow-mediated dilation (FMD) between treatment and control conditions. Secondary end points included changes in markers of inflammation, bone turnover, mineral metabolism, and calcification.

RESULTS

Eighteen patients completed the study and were included in the primary efficacy analysis. The mean (SD) age and eGFR were 59 (12) years and 26 (8) ml/min per 1.73 m2, respectively. Serum bicarbonate increased significantly with sodium bicarbonate treatment (+2.7±2.9 mEq/L, P≤0.001), whereas there was no change in bicarbonate levels in the control group. FMD significantly improved after sodium bicarbonate therapy (mean±SD, FMD baseline: 4.1%±4.1%; 6 weeks: 5.2%±2.9%; P=0.04) There was no significant change in FMD in the control group (mean±SD, FMD baseline: 4.6%±3.1%; 6 weeks: 4.1%±3.4%; P=0.20). Compared with control, sodium bicarbonate treatment resulted in a significant increase in FMD (mean, 1.8%; 95% confidence interval, 0.3 to 3.3; P=0.02). There was no significant change in bone markers or serum calcification propensity with treatment. Serum phosphorus and intact fibroblast growth factor 23 increased significantly during treatment.

CONCLUSIONS

Treatment of metabolic acidosis with sodium bicarbonate significantly improved vascular endothelial function in patients with stages 3b and 4 CKD.

Metabolic acidosis of chronic kidney disease and subclinical cardiovascular disease markers: Friend or foe?

The effect of chronic metabolic acidosis (MA) on cardiovascular disease (CVD) in the setting of chronic kidney disease (CKD) is largely unknown. Therefore, we aimed to study this relationship in nondialysis CKD patients.This cross-sectional, single-center study prospectively enrolled 95 clinically stable CKD patients (median age 61 (58, 65) years, 60% male, median eGFR 27 (22, 32) mL/min). Data on CKD etiology, CVD history, CVD traditional, and nontraditional risk factors were obtained. Also, markers of subclinical CVD were assessed: intima-media thickness (IMT), abdominal aortic calcifications (Kauppila score-AACs), cardio-ankle vascular index (CAVI), ankle-brachial index (ABI), ejection fraction, and interventricular septum thickness. Using the serum bicarbonate cutoff value of 22 mEq/L, comparisons between MA (<22 mEq/L; 43 patients) and non-MA (≥22 mEq/L; 52 patients) groups were performed.Vascular (40%), tubulointerstitial (24%), and glomerular (22%) nephropathies were the main causes of CKD. Twenty-three percent of patients had diabetes mellitus, but only 5% were considered to have diabetic nephropathy. Patients with chronic MA had lower eGFR (P < .01), higher iPTH (P = .01), higher serum phosphate (P < .01), and increased serum cholesterol (P = .04) and triglycerides (P = .01).Higher ABI (P = .04), lower IMT (P = .03), CAVI (P = .05), and AACs (P = .03) were found in patients with chronic MA.Separate binomial logistic regression models were performed using ABI (cutoff 0.9), CAVI (cutoff 9), IMT (cutoff 0.1 cm), and AACs (cutoff 1) as dependent variables. MA was used as independent variable and adjustments were made for iPTH, serum phosphate, eGFR, proteinuria, cholesterol, triglycerides, CVD score. The absence of MA was retained as an independent predictor only for the presence of AACs.In conclusion, the present study shows a potential advantageous effect of MA on vascular calcifications in predialysis CKD patients. Thus, a guideline relaxation of the serum bicarbonate target might prove to be beneficial in CKD patients at high risk of vascular calcifications. However, one should always consider the negative effects of MA. Therefore, additional research is warranted before any clear clinical recommendation.

The Relationship between Metabolic Acidosis and Nutritional Parameters in Patients on Hemodialysis

The progressive loss of kidney function is accompanied by metabolic acidosis. The relationship between metabolic acidosis, nutritional status, and oral bicarbonate supplementation has not been assessed in the Indian chronic kidney disease (CKD) population who are on maintenance hemodialysis (MHD). This is a single-center prospective study conducted in the Western part of India. Thirty-five patients, who were receiving MHD were assessed for metabolic acidosis along with various nutritional parameters at the baseline and at the follow-up after 3 months, postcorrection of acidosis with oral sodium bicarbonate supplements. The relationship between the correction of metabolic acidosis with oral bicarbonate supplements and changes in dietary and various nutritional parameters were evaluated. Metabolic acidosis at the baseline evaluation was found in 62.86% cases of the cohort with a mean serum bicarbonate value of 20.18 ± 4.93 mmol/L. The correction of acidosis with increment in the mean dosage of oral sodium bicarbonate supplements from 0.69 ± 0.410 mmol/kg/day at baseline to 1.04 ± 0.612 mmol/kg/day, significantly reduced the prevalence of metabolic acidosis to 23.33% cases at the follow-up. Improvement in serum bicarbonate level showed significant dietary, anthropometric, and nutritional improvements in these patients. Hence, we conclude that correction of metabolic acidosis with optimal oral bicarbonate supplementation plays a pivotal role in the treatment of malnourished CKD patients on MHD.

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.

Association between Low Serum Bicarbonate Concentrations and Cardiovascular Disease in Patients in the End-Stage of Renal Disease

BACKGROUND

Metabolic acidosis, a common condition particularly in the end-stage of renal disease patients, results in malnutrition, inflammation and oxidative stress. In this study, we focused on the association between low serum bicarbonate and cardiovascular disease in patients on intermittent dialysis.

METHODS

We studied 52 on-line-pre-dilution hemodiafiltration (on-l HDF) patients, 32 males and 20 females, with a mean age of 58.01 ± 15.4 years old. Metabolic acidosis was determined by serum bicarbonate concentrations less than 22 mmol/L. Residual renal function (RRF) was defined by interdialytic urine volume. Kaplan-Meier curves and Cox regression models were performed to predict coronary artery disease (CAD), defined by ejection fraction <50%, or diastolic dysfunction congestive heart failure (CHF) and peripheral vascular disease (PVD).

RESULTS

Kaplan-Meier analyses showed that a lower or higher than 22 mmol/L serum bicarbonate metabolic acidosis status was significantly associated with both PVD and diastolic dysfunction (log-rank = 5.07, p = 0.02 and log-rank = 5.84, p = 0.01, respectively). A similar prevalence of serum bicarbonate on CAD or CHF by low ejection fraction was not shown. The RRF was associated with PVD event and serum bicarbonate less than 22 mmol/L (log-rank = 5.49, p = 0.01 and log-rank = 3.9, p = 0.04, respectively). Cox regression analysis revealed that serum bicarbonate and RRF were significant risk factors for PVD after adjustment for confounders. Furthermore, RRF adjusted for covariates was shown to be a significant risk factor for diastolic dysfunction.

CONCLUSION

Low serum bicarbonate was associated with peripheral vascular disease and diastolic dysfunction in intermittent dialysis. The residual renal function may impact patients' outcomes through its relationship with metabolic acidosis status, particularly for peripheral vascular disease manifestation.

Correction of metabolic acidosis in hemodialysis: consequences on serum leptin and mineral metabolism

PURPOSE

Hyperleptinemia and metabolic acidosis (MA) are frequently observed in patients on hemodialysis (HD). While the role of leptin in patients on HD is not completely understood, HD only partially corrects MA. Both leptin and acidosis have effect on bone disease. The goal of the present study was to evaluate the effects of MA correction on chronic kidney disease-mineral and bone disorder laboratory parameters and leptin levels.

METHODS

Forty-eight patients on HD, aged 43±19 years, were prospectively studied. Individual adjustments in the bicarbonate dialysate concentration were made to maintain pre-dialysis concentration≥22 mEq/l. Blood gas analysis was done monthly for 4 months (M1-M4).

RESULTS

From M0 to M4, serum albumin increased (from 3.5 ±0.3 to 4.0±0.3 g/l, p<0.0001) while β2 microglobulin decreased (from 27.6±8.3 to 25.8±6.8 µg/ml, p=0.025). Serum leptin decreased in all but three patients, as well as leptin/adiponectin ratio (p<0.0001). There was a decrease in ionized serum calcium (from 5.0±0.5 to 4.7±0.5 mg/dl, p =0.002) and an increase in parathyroid hormone (PTH) [from 191 (85, 459) to 446 pg/ml (212, 983), p<0.0001] and in serum phosphate (from 5.4±1.4 to 5.8±1.1 mg/dl, p=0.048).

CONCLUSION

MA correction in HD patients can decrease leptin, an atherogenic marker. The impact of such treatment extends to uremic bone disease, as decrease in serum calcium and increase in PTH. However, this could be an undesirable effect because it may aggravate a secondary hyperparathyroidism. Whether the reduction in leptin levels has impact on outcomes in patients on hemodialysis deserves further investigation.

Autophagic clearance of mitochondria in the kidney copes with metabolic acidosis

Metabolic acidosis, a common complication of CKD, causes mitochondrial stress by undefined mechanisms. Selective autophagy of impaired mitochondria, called mitophagy, contributes toward maintaining cellular homeostasis in various settings. We hypothesized that mitophagy is involved in proximal tubular cell adaptations to chronic metabolic acidosis. In transgenic mice expressing green fluorescent protein-tagged microtubule-associated protein 1 light chain 3 (GFP-LC3), NH4Cl loading increased the number of GFP puncta exclusively in the proximal tubule. In vitro, culture in acidic medium produced similar results in proximal tubular cell lines stably expressing GFP-LC3 and facilitated the degradation of SQSTM1/p62 in wild-type cells, indicating enhanced autophagic flux. Upon acid loading, proximal tubule-specific autophagy-deficient (Atg5-deficient) mice displayed significantly reduced ammonium production and severe metabolic acidosis compared with wild-type mice. In vitro and in vivo, acid loading caused Atg5-deficient proximal tubular cells to exhibit reduced mitochondrial respiratory chain activity, reduced mitochondrial membrane potential, and fragmented morphology with marked swelling in mitochondria. GFP-LC3-tagged autophagosomes colocalized with ubiquitinated mitochondria in proximal tubular cells cultured in acidic medium, suggesting that metabolic acidosis induces mitophagy. Furthermore, restoration of Atg5-intact nuclei in Atg5-deficient proximal tubular cells increased mitochondrial membrane potential and ammoniagenesis. In conclusion, metabolic acidosis induces autophagy in proximal tubular cells, which is indispensable for maintaining proper mitochondrial functions including ammoniagenesis, and thus for adapted urinary acid excretion. Our results provide a rationale for the beneficial effect of alkali supplementation in CKD, a condition in which autophagy may be reduced, and suggest a new therapeutic option for acidosis by modulating autophagy.

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.

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.

Differential effects of phosphate binders on pre-dialysis serum bicarbonate in end-stage kidney disease patients on maintenance haemodialysis

Background

Phosphate binders’ constituents have alkalotic or acidotic properties and may contribute to acid base balance in haemodialysis patients. This study aimed to investigate the differential effects of phosphate binders on pre-dialysis serum bicarbonate in End Stage Kidney Disease patients on maintenance haemodialysis.

Methods

Stable out-patients having satellite haemodialysis for at least 3 months were retrospectively studied for 18 months, excluding those with other medical causes for metabolic acidosis. Blood results were censored for inpatient episodes, at the time of death, renal transplant or dialysis modality change. Multivariable multilevel mixed-effects linear regression was used and five groups of phosphate binders were compared: Group A(Calcium (Ca) and/or Aluminium (Al) binders); B(Sevelamer hydrochloride (SH) alone); C(lanthanum carbonate (LC) alone); D(SH and Ca/Al), E(LC and Ca/Al).

Results

Of 320 patients, 292 were eligible for analysis with a mean follow-up of 15.54 (standard deviation, SD 3.98) months. Similar mean pre-dialysis serum levels of bicarbonate were observed at all 6 month-interval analyses. At 18^th months, observed mean serum bicarbonate levels in mmol/L were Group B: 21.58 (SD 2.82, P<0.001), C: 23.29 (SD 2.80, P=0.02), D: 21.56 (SD 3.00, P<0.001), and E: 21.29 (SD 3.62, P=0.92) compared with Group A: 22.98 (SD 2.77). Mean serum bicarbonate was related to total SH dose in mmol/L: 22.34 (SD 2.56) for SH <2.5 g/day, 21.61 (SD 2.62) for SH 2.5-4.8 g/day, 21.04 (SD 3.31) for SH >4.8 g/day compared with 22.85 (SD 2.91) for non-users; P-trend<0.001.

Conclusions

Phosphate binders’ constituents may contribute to/protect against a predisposition to pre-dialysis metabolic acidosis. This may be dose dependant in patients taking Sevelamer Hydrochloride.

Sevelamer hydrochloride dose-dependent increase in prevalence of severe acidosis in hemodialysis patients: analysis of nationwide statistical survey in Japan

Metabolic acidosis has a negative impact on prognosis of dialysis patients. The aim of this study was to determine the prevalence of severe metabolic acidosis in dialysis patients treated with sevelamer hydrochloride. In 2004, a nationwide survey (101,516 dialysis patients) was conducted by the Japanese Society for Dialysis Therapy. We analyzed 32,686 dialysis patients whose bicarbonate levels were measured in the survey. Sevelamer hydrochloride was prescribed to 9231 dialysis patients while 23,455 dialysis patients were not prescribed sevelamer hydrochloride. In the present study, we defined severe acidosis as bicarbonate <15.8 mmol/L. The mean serum bicarbonate level correlated significantly and negatively with the daily dose of sevelamer hydrochloride (R(2) = 0.806, P < 0.0001). Logistic regression analysis indicated that the percentage of patients with severe acidosis increased significantly with increased dose of sevelamer hydrochloride (R(2) = 0.885, P < 0.00001). The estimated doses of sevelamer hydrochloride associated with severe acidosis in 10% and 15% of patients were 3.5 g/day (95% confidence interval [95%CI], 2.8-4.4) and 7.7 g/day (95%CI = 5.9-10.9), respectively. Severe acidosis was noted in 4.5% of patients who were not treated with sevelamer hydrochloride and in 16.1% of patients treated with sevelamer hydrochloride at ≥ 5.25 g/day (P < 0.0001). The results call for careful monitoring of serum bicarbonate level in hemodialysis patients treated with sevelamer hydrochloride.

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.

Activation of intrarenal renin-angiotensin system during metabolic acidosis

BACKGROUND

Chronic metabolic acidosis is a common metabolic disturbance and its clinical impact can be severe and extensive. The role and the change of the intrarenal renin-angiotensin system (RAS) during metabolic acidosis are uncertain, and whether acidosis can evoke inflammation remains unclear.

METHODS

Male Sprague-Dawley rats were fed with water containing 0.14 M NH(4)Cl to induce metabolic acidosis for 1 and 8 weeks, respectively. They were compared with animals fed with deionized water (control) and equimolar sodium chloride water (NaCl). Gene expression analysis of RAS components included renin, renin/prorenin receptor, angiotensinogen, angiotensin-converting enzyme (ACE), and angiotensin II type 1 and 2 receptors (AT1R and AT2R). Histological examination was also performed to detect morphological change.

RESULTS

Acidosis was found in 1-week NH(4)Cl-treated rats but not in the 8-week group. More than twofold proteinuria and a significant decline of glomerular filtration rate (GFR) were observed in acid-loaded rats. Compared to the control and NaCl groups, angiotensinogen, ACE, AT1R and AT2R were significantly increased in the 1-week acidosis group (all p < 0.05). Sustained increase of AT1R expression was found as NH(4)Cl was continued for 8 weeks. There was no significant change in transforming growth factor-β and nuclear factor-κB. The architecture of tubular epithelial cells was affected during our experiment.

CONCLUSION

Metabolic acidosis induced proteinuria and decline of GFR in association with activation of intrarenal RAS.

Amino Acid-Based Peritoneal Dialysis Solutions for Malnutrition: New Perspectives

Protein and energy malnutrition is frequently found in patients on maintenance dialysis and is associated with an increased risk of death. Among a variety of factors involved in the development of protein and energy malnutrition, such as acidosis, insulin resistance, inflammation, and dialysate protein losses, insufficient intake of proteins and energy as a result of anorexia plays a prominent role.

Amino acid (AA)-based peritoneal dialysis (PD) solutions can induce an anabolic response in malnourished patients on continuous ambulatory PD if enough calories are ingested simultaneously. Poor appetite, however, may impede the intake of sufficient calories. Peritoneal dialysis solutions containing a mixture of AAs and glucose in a proper ratio can serve as a source of proteins and calories. Such a dialysis solution can be used in fasting patients on nocturnal automated PD as part of a regular dialysis schedule. Using a sophisticated technique involving stable isotopes, this dialysis mixture has been found to induce acute anabolic changes in whole body protein metabolism. Such a metabolic response is similar to that induced by food. Intraperitoneal AAs, in common with ingested proteins, can induce generation of hydrogen ions and urea through oxidation of specific AAs. Supplying AAs together with calories could bring about utilization of AAs for the synthesis of proteins rather than the oxidation of AAs, thereby limiting production of acid and urea. Using dialysis solutions with a buffer concentration of 40 mmol/L further contributes to maintaining acid–base homeostasis.

We advocate consideration of usage of AA/glucose dialysate when PD patients cannot comply with dietary requirements. To evaluate the long-term effects of this approach on morbidity and mortality, clinical trials with large groups of patients are needed.

Influence of renal function and diet on acid-base status in chronic kidney disease patients

OBJECTIVE

We investigated the influence of potential renal acid load (PRAL) and renal function on the degree of metabolic acidosis in patients with chronic kidney disease (CKD).

DESIGN

This was a cross-sectional study.

SETTING

This study was conducted at the Nephrology Outpatient Division of the Hospital Universitário Clementino Fraga Filho (Rio de Janeiro, Brazil).

PATIENTS

Thirty CKD patients undergoing conservative treatment were divided according to plasma HCO(3)(-) values into acidotic (HCO(3)(-) <or=22 mM, n = 15) and nonacidotic (HCO(3)(-) >22 mM, n = 15).

MAIN OUTCOME MEASURE

Biochemical, nutritional, and anthropometric parameters and PRAL were measured.

RESULTS

The mean of plasma HCO(3)(-) values was 17.7 +/- 2.8 mM in the acidotic group, and 25.1 +/- 2.2 mM in the nonacidotic group. There was no significant difference in mean PRAL values between the acidotic (9.8 +/- 6.4 mEq/day) and nonacidotic (12.7 +/- 10.0 mEq/day) groups, but there was a significant correlation between plasma HCO(3)(-) and creatinine clearance (r = 0.78, P < .0001). Based on the receiver operating characteristic curve, the level of creatinine clearance to begin detection of acidosis was 31.8 mL/min, with a sensitivity and specificity of 86.7%.

CONCLUSION

The acid-base status of this group of CKD patients undergoing conservative treatment was mainly determined by degree of renal insufficiency rather than diet.

Dialysate as food as an option for automated peritoneal dialysis

Protein-energy malnutrition is frequently found in dialysis patients. Many factors play a role in its development including deficient nutrient intake as a result of anorexia. Peritoneal dialysis (PD) solutions containing a mixture of amino acids and glucose in an appropriate ratio could serve as a source of food. The authors of this article found that such a dialysis solution when administered to fasting patients who were on nightly automated peritoneal dialysis (APD), as part of a regular dialysis schedule, induced an acute anabolic effect. Also in PD patients in the fed state, dialysis solutions containing both amino acids and glucose were found to improve protein metabolism. It appears that the body responds similar to intraperitoneal and oral amino acid:dialysate as food. Like dietary proteins, intraperitoneal amino acids can bring about generation of hydrogen ions and urea as a result of oxidation. No rise of serum urea levels was found and serum bicarbonate remained within the normal range when a total buffer concentration of 40 mmol/L in the mixture was used. The use of this approach may be an option for PD patients who cannot fulfil dietary recommendations.

Bench-to-bedside review: metabolism and nutrition

Acute kidney injury (AKI) develops mostly in the context of critical illness and multiple organ failure, characterized by alterations in substrate use, insulin resistance, and hypercatabolism. Optimal nutritional support of intensive care unit patients remains a matter of debate, mainly because of a lack of adequately designed clinical trials. Most guidelines are based on expert opinion rather than on solid evidence and are not fundamentally different for critically ill patients with or without AKI. In patients with a functional gastrointestinal tract, enteral nutrition is preferred over parenteral nutrition. The optimal timing of parenteral nutrition in those patients who cannot be fed enterally remains controversial. All nutritional regimens should include tight glycemic control. The recommended energy intake is 20 to 30 kcal/kg per day with a protein intake of 1.2 to 1.5 g/kg per day. Higher protein intakes have been suggested in patients with AKI on continuous renal replacement therapy (CRRT). However, the inadequate design of the trials does not allow firm conclusions. Nutritional support during CRRT should take into account the extracorporeal losses of glucose, amino acids, and micronutrients. Immunonutrients are the subject of intensive investigation but have not been evaluated specifically in patients with AKI. We suggest a protocolized nutritional strategy delivering enteral nutrition whenever possible and providing at least the daily requirements of trace elements and vitamins.

Acidose metabólica na doença renal crônica: abordagem nutricional

A acidose metabólica é uma das complicações da doença renal crônica e está associada ao aumento do catabolismo protéico, à diminuição da síntese de proteínas e ao balanço nitrogenado negativo. A dieta tem forte influência sobre a geração de ácidos, podendo contribuir, portanto, para determinar a gravidade da acidose no paciente com doença renal crônica. Alguns pesquisadores têm observado que é possível estimar a excreção ácida renal, e que o cálculo dessa carga ácida a partir de alguns componentes da dieta, permitiria uma predição apropriada dos efeitos da dieta na acidose metabólica. Este artigo é uma comunicação sobre as bases fisiológicas, bem como as implicações clínicas da acidose em pacientes com doença renal crônica e a influência da dieta no balanço ácido-básico desses pacientes.