Serum bicarbonate levels and the progression of kidney disease: a cohort study

Metabolic Acidosis in CKD: Pathogenesis, Adverse Effects, and Treatment Effects

Metabolic acidosis is a frequent complication of chronic kidney disease and is associated with a number of adverse outcomes, including worsening kidney function, poor musculoskeletal health, cardiovascular events, and death. Mechanisms that prevent metabolic acidosis detrimentally promote further kidney damage, creating a cycle between acid accumulation and acid-mediated kidney injury. Disrupting this cycle through the provision of alkali, most commonly using sodium bicarbonate, is hypothesized to preserve kidney function while also mitigating adverse effects of excess acid on bone and muscle. However, results from clinical trials have been conflicting. There is also significant interest to determine whether sodium bicarbonate might improve patient outcomes for those who do not have overt metabolic acidosis. Such individuals are hypothesized to be experiencing acid-mediated organ damage despite having a normal serum bicarbonate concentration, a state often referred to as subclinical metabolic acidosis. Results from small- to medium-sized trials in individuals with subclinical metabolic acidosis have also been inconclusive. Well-powered clinical trials to determine the efficacy and safety of sodium bicarbonate are necessary to determine if this intervention improves patient outcomes.

A basic solution for a complex problem: does treatment of metabolic acidosis slow CKD progression?

PURPOSE OF THIS REVIEW

Metabolic acidosis is frequently encountered in patients with chronic kidney disease (CKD), with increasing prevalence as kidney function worsens. Treating electrolyte disturbances is the sine qua non of Nephrologists, and alkali therapy to normalize serum bicarbonate levels and slow progression of kidney disease has been embedded in clinical practice guidelines for decades on the basis of animal models and controversial clinical trials. This review will critically appraise the literature base for this recommendation and determine whether the available evidence supports this common practice, which is a timely endeavor considering the impending demotion of metabolic acidosis treatment from recommendation to practice point in forthcoming KDIGO guidelines.

RECENT FINDINGS

Earlier, open-label, studies supporting the utility of sodium bicarbonate therapy to slow progression of chronic kidney disease have been challenged by more recent, blinded, studies failing to show benefit on CKD progression. This was further demonstrated in the absence of concomitant sodium administration with the hydrochloric acid binder veverimer, which failed to demonstrate benefit on renal death, end stage kidney disease or 40% reduction in estimated glomerular filtration rate in a large multicenter trial.

SUMMARY

The current body of literature does not support the routine treatment of metabolic acidosis in patients with CKD and the authors agree with the forthcoming KDIGO guidelines to de-emphasize this common practice.

Serum bicarbonate levels and kidney outcomes in critically ill patients: a prospective cohort study

BACKGROUND

The interplay between serum bicarbonate levels and kidney outcomes is not fully understood. We conducted a prospective cohort study in three intensive care units (ICUs) to evaluate the association of serum bicarbonate levels with acute kidney injury (AKI) and kidney function recovery in critically ill patients.

METHODS

A prospective cohort study in three intensive care units (ICUs) was performed. The serum bicarbonate level in the first 24 h after ICU admission was categorized as low (< 22 mEq/L), normal (22-26 mEq/L), or high (> 26 mEq/L). Serum creatinine (SCr) levels according to the KDIGO AKI guideline were used for defining AKI within the first 7 days of ICU stay. At ICU admission, SCr ≥ 1.1 for women and ≥ 1.3 mg/dL for men were indicative of impaired kidney function. Mortality outcome was tracked up to 28 days, and kidney function recovery was assessed at hospital discharge.

RESULTS

A total of 2732 patients (66 ± 19 years and 55% men) were analyzed, with 32% having impaired kidney function at ICU admission. Overall, 26% of patients had low bicarbonate levels, while 32% had high bicarbonate levels. Notably, patients with preserved kidney function showed a lower prevalence of low bicarbonate levels compared to those with impaired kidney function (20% vs. 39%, p < 0.001), while higher rates were observed for high bicarbonate (35% vs. 24%, p < 0.001). Compared with patients with normal serum bicarbonate levels, those with low bicarbonate were 81% more likely to develop AKI (OR = 1.81; 95% CI 1.10-2.99), whereas those with high bicarbonate were 44% less likely (OR = 0.56; 95% CI 0.32-0.98) in the adjusted model for confounders. Neither those with high nor low serum bicarbonate levels were associated with an increased risk of mortality (HR = 1.03; 95% CI 0.68-1.56 and 0.99; 95% CI 0.68-1.42, respectively). In subgroup analysis, regardless of the kidney function at ICU admission, serum bicarbonate levels were not associated with the development of AKI and all-cause mortality. Regarding kidney function recovery, higher non-recovery rates were found for those with low bicarbonate.

CONCLUSION

In critically ill ICU patients, low bicarbonate levels were associated with the more likely development of AKI and subsequent non-recovery of kidney function, while high bicarbonate levels showed no such association. Therefore, low bicarbonate levels may be considered a risk factor for adverse kidney outcomes in critically ill patients.

The Role of Dietary Acid Load on Progression of Estimated Glomerular Filtration Rate Among Individuals Diagnosed With Chronic Kidney Disease

OBJECTIVE

Individuals with chronic kidney disease (CKD) are at an increased risk for developing metabolic acidosis. Metabolic acidosis has been shown to worsen kidney function and exacerbate systemic inflammation. Diets high in protein foods can exacerbate metabolic acidosis as protein foods tend to be more acidic, while fruits and vegetables are more alkalotic. The main objective of this systematic review was to determine if higher consumption of fruits and vegetables in adults with CKD stages 1-5 reduces the rate of decline of estimated glomerular filtration rate.

METHODS

Searches of Cumulated Index to Nursing and Allied Health Literature (CINAHL -Elton B. Stephens Company [EBSCO]), Cochrane Library (Wiley), Dissertation & Thesis Global (ProQuest), Embase (Elsevier), Medline (OVID), PubMed (National Library of Medicine), Scopus (Elsevier), and Web of Sciences (Clarivate) identified 1,451 articles published between January 2015 and June 2023.

RESULTS

After independent review, 7 total studies were included. Six of the studies found an association between dietary acid load and progression of CKD.

CONCLUSIONS

Dietary counseling focusing on decreasing dietary acid load may be beneficial for individuals with CKD.

Oral Sodium Bicarbonate and Bone Turnover in CKD: A Secondary Analysis of the BASE Pilot Trial

SIGNIFICANCE STATEMENT

In CKD, metabolic acidosis is commonly treated with alkali in the hope that it will improve bone health. In a post hoc analysis of the Bicarbonate Administration to Stabilize eGFR Pilot Trial, we investigated whether sodium bicarbonate affects serum levels of bone turnover markers and other hormones related to bone health in individuals with CKD who have normal to slightly reduced total CO2 (20-28 mEq/L). Sodium bicarbonate increased serum levels of α-klotho but had no significant effect on other bone health markers, including intact fibroblast growth factor-23 (iFGF-23), intact parathyroid hormone (iPTH), and bone-specific alkaline phosphatase (B-SAP). Further study is needed to determine the effect of bicarbonate administration on clinical aspects of bone health.

BACKGROUND

Treatment with alkali has been hypothesized to improve bone health in CKD by mitigating adverse effects of acid on bone mineral. We investigated the effect of treatment with sodium bicarbonate on bone turnover markers and other factors related to bone metabolism in CKD.

METHODS

This is a post hoc analysis of the Bicarbonate Administration to Stabilize eGFR Pilot Trial in which 194 individuals with CKD and serum total CO2 20-28 mEq/L were randomly assigned to placebo or one of two doses of sodium bicarbonate (0.5 or 0.8 mEq/kg lean body weight per day) for 28 weeks. The following serum measurements were performed at baseline, week 12, and week 28: B-SAP, c-telopeptide, procollagen type I intact N-terminal propeptide, iPTH, iFGF-23, soluble klotho, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and tartrate-resistant acid phosphatase 5b. The difference (sodium bicarbonate versus placebo) in mean change of each bone biomarker from baseline was determined using linear mixed models.

RESULTS

One hundred sixty-eight participants submitted samples for post hoc investigations. Mean eGFR was 37±10 ml/min per 1.73 m2 and mean total CO2 was 24±3 mEq/L at baseline. Sodium bicarbonate induced a dose-dependent increase in soluble klotho levels compared with placebo. There was no significant effect of treatment with either dose of sodium bicarbonate on any of the other bone biomarkers, including iFGF-23, iPTH, and B-SAP. Effects on bone biomarkers were similar in those with baseline serum total CO2 <24 mEq/L compared with those with total CO2 ≥24 mEq/L.

CONCLUSIONS

In this pilot trial of individuals with CKD and total CO2 20-28 mEq/L, sodium bicarbonate treatment increased serum klotho levels but did not affect other bone health markers over 28 weeks.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

ClinicalTrials.gov, NCT02521181.

In the "Plant-Based" Era, Patients With Chronic Kidney Disease Should Focus on Eating Healthy

In the era of plant-based diets, it is important for Nephrology providers to know the evidence regarding their healthfulness in patients with chronic kidney disease (CKD). A whole food, plant-based diet, which emphasizes fresh, minimally processed or refined plant-based foods and limits animal products, has shown benefits for patients with CKD. These include reduced dietary acid load, lower bioavailability of potassium and phosphorus, increased dietary fiber intake, nutritional adequacy, and cardiovascular and mortality benefits. Potential drawbacks include the need for specific knowledge, skills, and cost involved in preparing varied, healthy, and appetizing plant-based meals, leading to lower acceptability and accessibility to certain populations. Liberalization of the standard CKD diet to include healthy, minimally processed foods such as fruits, vegetables, nuts, legumes, and whole grains is likely beneficial, though more research is needed to determine whether a plant-based-only diet is the optimal way to achieve healthier eating in patients with CKD.

Association of body mass index with the development of metabolic acidosis in patients with chronic kidney disease

AIMS

Higher body mass index (BMI) is associated with higher bone mass and bone serves as a buffer during the development of metabolic acidosis. The authors sought to examine the relationship between BMI and metabolic acidosis in patients with chronic kidney disease (CKD).

MATERIALS AND METHODS

The study utilized a large US longitudinal data repository including over 103 million patients from healthcare provider organizations to evaluate the relationship between the exposure variable (BMI) and the prevalence and incidence of metabolic acidosis among patients with estimated glomerular filtration rate <60 ml/min/1.73 m2. Incident metabolic acidosis was identified at the first of two consecutive post-index serum bicarbonate values, 10-365 days apart, between 12 and <22 mEq/L in patients with normal index serum bicarbonate. Cox proportional hazard models were adjusted for multiple variables including demographics, comorbidities, income, education, and kidney function.

RESULTS

103,766 patients qualified for this study; 6472 (6.2%) had metabolic acidosis at index. An inverse association between BMI category and metabolic acidosis was observed for both baseline (prevalence) and new-onset (incidence) metabolic acidosis. Compared to BMI category of 18.5 to <25 kg/m2, each category of incrementally higher BMI was associated with a decreasing risk of incident metabolic acidosis; the adjusted hazard ratios (95% confidence interval) were 0.866 (0.824-0.911), 0.770 (0.729-0.813), 0.664 (0.622-0.709), and 0.612 (0.571-0.655) for BMI 25 to <30, 30 to <35, 35 to <40, and 40+ kg/m2, respectively.

CONCLUSIONS

Among patients with CKD, an incremental increase in BMI was inversely associated with both the prevalence and incidence of metabolic acidosis. These associations suggest that increased body weight may protect against the development of metabolic acidosis, a risk factor for progressive loss of kidney function.

Venous bicarbonate and CKD progression: a longitudinal analysis by the group-based trajectory model

Background

Metabolic acidosis accelerates chronic kidney disease (CKD) progression towards kidney failure in animal models. Clinical trials testing the effect of bicarbonate on kidney outcomes are underpowered and/or of suboptimal quality. On the other hand, observational studies testing the same hypothesis are generally based on bicarbonate measured at a single time point.

Methods

We studied the longitudinal relationship between repeated venous bicarbonate levels and a predefined composite renal outcome (a ≥30% estimated glomerular filtration rate reduction, dialysis or transplantation) by using group-based trajectory model (GBTM) analysis. The GBTM analysis was used to classify patients based on individual bicarbonate levels over time. The relationship between trajectory groups and renal outcomes was investigated using crude and adjusted Cox regression models. A total of 528 patients with stage 2-5 CKD were included in the analysis.

Results

The GBTM analysis identified four distinct trajectories of bicarbonate levels: low, moderate, moderate-high and high. During the follow-up period, 126 patients experienced the combined renal endpoint. The hazard rate of renal events decreased dose-dependently from the lowest to the highest bicarbonate trajectory. After adjusting for potential confounders, there was a 63% risk reduction for the composite renal endpoint for patients in the high trajectory category compared with those in the low trajectory category.

Conclusion

The study found that higher bicarbonate trajectories were associated with a lower risk of adverse renal outcomes in CKD patients. These results suggest that strategies to maintain higher bicarbonate levels may benefit patients with CKD. However, further high-quality randomised trials are needed to confirm these findings and recommend bicarbonate supplementation as a strategy to delay CKD progression.

Sodium Bicarbonate Treatment and Vascular Function in CKD: A Randomized, Double-Blind, Placebo-Controlled Trial

SIGNIFICANCE STATEMENT

Lower serum bicarbonate levels, even within the normal range, are strongly linked to risks of cardiovascular disease in CKD, possibly by modifying vascular function. In this randomized, controlled trial, treatment with sodium bicarbonate (NaHCO 3 ) did not improve vascular endothelial function or reduce arterial stiffness in participants with CKD stage 3b-4 with normal serum bicarbonate levels. In addition, NaHCO 3 treatment did not reduce left ventricular mass index. NaHCO 3 did increase plasma bicarbonate levels and urinary citrate excretion and reduce urinary ammonium excretion, indicating that the intervention was indeed effective. NaHCO 3 therapy was safe with no significant changes in BP, weight, or edema. These results do not support the use of NaHCO 3 for vascular dysfunction in participants with CKD.

BACKGROUND

Lower serum bicarbonate levels, even within the normal range, are strongly linked to risks of cardiovascular disease in CKD, possibly by modifying vascular function. Prospective interventional trials with sodium bicarbonate (NaHCO 3 ) are lacking.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial examining the effect of NaHCO 3 on vascular function in 109 patients with CKD stage 3b-4 (eGFR 15-44 ml/min per 1.73 m 2 ) with normal serum bicarbonate levels (22-27 mEq/L). Participants were randomized 1:1 to NaHCO 3 or placebo at a dose of 0.5 mEq/lean body weight-kg per day for 12 months. The coprimary end points were change in brachial artery flow-mediated dilation (FMD) and change in aortic pulse wave velocity over 12 months.

RESULTS

Ninety patients completed this study. After 12 months, plasma bicarbonate levels increased significantly in the NaHCO 3 group compared with placebo (mean [SD] difference between groups 1.35±2.1, P = 0.003). NaHCO 3 treatment did not result in a significant improvement in aortic pulse wave velocity from baseline. NaHCO 3 did result in a significant increase in flow-mediated dilation after 1 month; however, this effect disappeared at 6 and 12 months. NaHCO 3 resulted in a significant increase in 24-hour urine citrate and pH and a significant decrease in 24-hour urine ammonia. There was no significant change in left ventricular mass index, ejection fraction, or eGFR with NaHCO 3 . NaHCO 3 treatment was safe and well-tolerated with no significant changes in BP, antihypertensive medication, weight, plasma calcium, or potassium levels.

CONCLUSION

Our results do not support the use of NaHCO 3 for vascular dysfunction in participants with CKD and normal serum bicarbonate levels.

NBCe1-B/C-knockout mice exhibit an impaired respiratory response and an enhanced renal response to metabolic acidosis

The sodium-bicarbonate cotransporter (NBCe1) has three primary variants: NBCe1-A, -B and -C. NBCe1-A is expressed in renal proximal tubules in the cortical labyrinth, where it is essential for reclaiming filtered bicarbonate, such that NBCe1-A knockout mice are congenitally acidemic. NBCe1-B and -C variants are expressed in chemosensitive regions of the brainstem, while NBCe1-B is also expressed in renal proximal tubules located in the outer medulla. Although mice lacking NBCe1-B/C (KOb/c) exhibit a normal plasma pH at baseline, the distribution of NBCe1-B/C indicates that these variants could play a role in both the rapid respiratory and slower renal responses to metabolic acidosis (MAc). Therefore, in this study we used an integrative physiologic approach to investigate the response of KOb/c mice to MAc. By means of unanesthetized whole-body plethysmography and blood-gas analysis, we demonstrate that the respiratory response to MAc (increase in minute volume, decrease in pCO2) is impaired in KOb/c mice leading to a greater severity of acidemia after 1 day of MAc. Despite this respiratory impairment, the recovery of plasma pH after 3-days of MAc remained intact in KOb/c mice. Using data gathered from mice housed in metabolic cages we demonstrate a greater elevation of renal ammonium excretion and greater downregulation of the ammonia recycling enzyme glutamine synthetase in KOb/c mice on day 2 of MAc, consistent with greater renal acid-excretion. We conclude that KOb/c mice are ultimately able to defend plasma pH during MAc, but that the integrated response is disturbed such that the burden of work shifts from the respiratory system to the kidneys, delaying the recovery of pH.

Pathophysiological Implications and Therapeutic Approach of Klotho in Chronic Kidney Disease. A Systematic Review

The Klotho protein, known as an anti-aging protein, is expressed mainly in the kidney, and kidney disorders may contribute to disrupted expression of renal Klotho. The purpose of this systematic review was to determine if there are biological and nutraceutical therapies that increase the expression of Klotho and can help prevent complications associated with CKD. A systematic literature review was carried out through the consultation of PubMed, Scopus, and Web of Science. Records between the years 2012 and 2022 in Spanish and English were selected. Cross-sectional or prevalence and analytical studies were included that evaluated the effects of Klotho therapy. A total of 22 studies were identified after the critical reading of these selected studies. Three investigated the association between Klotho and growth factors; two evaluated the relationship between the concentration of Klotho and the type of fibrosis; three focused on the relationship between vascular calcifications and vitamin D; two assessed the relationship between Klotho and bicarbonate; two investigated the relationship between proteinuria and Klotho; one demonstrated the applicability of synthetic antibodies as a support for Klotho deficiency; one investigated Klotho hypermethylation as a renal biomarker; two investigated the relationship between proteinuria and Klotho; four linked Klotho as an early marker of CKD; one investigated Klotho levels in patients with autosomal dominant polycystic kidney disease. In conclusion, no study has addressed the comparison of these therapies in the context of their use with nutraceutical agents that raise the expression of Klotho.

Metabolic Acidosis in Children: A Literature Review

Metabolic acidosis is characterised by a primary decrease in the serum bicarbonate concentration, a secondary decrease in the arterial partial pressure of CO­2, and a reduction in blood pH. Metabolic acidosis, acute or chronic, may have deleterious effects on cellular function and cause increased morbidity and mortality. A systematic review of the available literature was performed to identify data on the prevalence, manifestations, cause, outcomes, and treatment of metabolic acidosis in children. Online databases (Ovid Medline, Embase, and PubMed), commercial search engines (including Google), and chapters on metabolic acidosis in the standard textbooks of paediatrics and medicine were reviewed. Systematic approach to acute metabolic acidosis starts with proper history taking and examination. This is followed by assessment of acid-base parameters, including pH, partial pressure of CO2, and bicarbonate concentration in arterial blood. Blood gas is needed to differentiate primary metabolic acidosis from compensated respiratory alkalosis. Once the diagnosis of a metabolic acidosis has been confirmed, serum electrolyte values are used to determine the serum anion gap. The various causes of increased and normal anion gap metabolic acidosis have been discussed in the article. The main aim of treatment in metabolic acidosis is to reverse the primary pathophysiology. In acute metabolic acidosis, sodium bicarbonate therapy is not beneficial due to potential complications and is reserved for specific situations. Base therapy is used in chronic metabolic acidosis where it ameliorates many of its untoward effects. Other modalities of treatment of metabolic acidosis include peritoneal or haemodialysis and tris-hydroxymethyl aminomethane.

Long-term complications of primary distal renal tubular acidosis

The clinical manifestations of primary distal renal tubular acidosis usually begin in childhood, but the disease is caused by a genetic defect that persists throughout life. This review focuses on the complications of distal tubular acidosis that occur or remain long-term such as nephrocalcinosis and urolithiasis, growth impairment, bone mineralization, severe hypokalemia, kidney cysts, and progressive kidney failure, as well as other persistent manifestations that occur independent of acidosis but are associated with some inherited forms of the disease. The pathogenic factors responsible for kidney failure are discussed in particular because it is a complication to which different publications have recently drawn attention and which affects a high percentage of adults with primary distal renal tubular acidosis. The need to maintain optimal metabolic control of the disease and scheduled clinical follow-up throughout life and the importance of organizing protocols for the transition of patients to adult nephrology services are emphasized.

Increasing Serum Bicarbonate is Associated with Reduced Risk of Adverse Kidney Outcomes in Patients with CKD and Metabolic Acidosis

Introduction

Low serum bicarbonate at a single point in time is associated with accelerated kidney decline in patients with chronic kidney disease (CKD). We modeled how changes in serum bicarbonate over time affect incidence of adverse kidney outcomes.

Methods

We analyzed data from Optum's deidentified Integrated Claims-Clinical data set of US patients (2007-2019) with ≥1 year of prior medical record data, CKD stages G3 to G5, and metabolic acidosis (i.e., index serum bicarbonate 12 to <22 mmol/l). The primary predictor of interest was the change in serum bicarbonate, evaluated at each postindex outpatient serum bicarbonate test as a time-dependent continuous variable. The primary outcome was a composite of either a ≥40% decline in estimated glomerular filtration rate (eGFR) from index or evidence of dialysis or transplantation, evaluated using Cox proportional hazards models.

Results

A total of 24,384 patients were included in the cohort with median follow-up of 3.7 years. A within-patient increase in serum bicarbonate over time was associated with a lower risk of the composite kidney outcome. The unadjusted hazard ratio (HR) per 1-mmol/l increase in serum bicarbonate was 0.911 (95% confidence interval [CI]: 0.905-0.917; P < 0.001). After adjustment for baseline eGFR and serum bicarbonate, the time-adjusted effect of baseline eGFR and other covariates, the HR per 1-mmol/l increase in serum bicarbonate was largely unchanged (0.916 [95% CI: 0.910-0.922; P < 0.001]).

Conclusion

In a real-world population of US patients with CKD and metabolic acidosis, a within-patient increase in serum bicarbonate over time independent of changes in eGFR, was associated with a lower risk of CKD progression.

Associations of the Serum Total Carbon Dioxide Level with Long-Term Clinical Outcomes in Sepsis Survivors

INTRODUCTION

Sepsis is characterized by a dysregulated host response to infection that leads to multiple organ dysfunction and often complicated with metabolic acidosis. However, the associations between serum total carbon dioxide level (TCO₂) and long-term clinical outcomes in sepsis survivors remains unknown.

METHODS

A total of 7212 sepsis survivors aged ≥ 20 years who were discharged from January  1, 2008 to December 31, 2018 were included in our analyses. The sepsis survivors were further divided into high TCO₂ (≥ 18 mmol/L) and low TCO₂ (< 18 mmol/L) groups, comprising 5023 and 2189 patients, respectively. The following outcomes of interest were included: all-cause mortality, myocardial infarction, ischemic stroke, hospitalization for heart failure, ventricular arrhythmia, and end-stage renal disease (ESRD).

RESULTS

After propensity score matching, the low TCO₂ group was at higher risks of all-cause mortality (hazard ratio [HR] 1.28, 95% confidence interval [95% CI] 1.18-1.39), myocardial infarction (HR 1.83, 95% CI 1.39-2.43), and ESRD (HR 1.38, 95% CI 1.16-1.64) than the high TCO₂ group. The results remained similar after considering death as a competing risk.

CONCLUSION

Patients discharged from hospitalization for sepsis have higher risks of worse long-term clinical outcomes. Physicians may need to pay more attention to sepsis survivors whose TCO₂ was low.

Longitudinal trajectory of acidosis and mortality in acute kidney injury requiring continuous renal replacement therapy

BACKGROUND

Acidosis frequently occurs in severe acute kidney injury (AKI), and continuous renal replacement therapy (CRRT) can control this pathologic condition. Nevertheless, acidosis may be aggravated; thus, monitoring is essential after starting CRRT. Herein, we addressed the longitudinal trajectory of acidosis on CRRT and its relationship with worse outcomes.

METHODS

The latent growth mixture model was applied to classify the trajectories of pH during the first 24 hours and those of C-reactive protein (CRP) after 24 hours on CRRT due to AKI (n = 1815). Cox proportional hazard models were used to calculate hazard ratios of all-cause mortality after adjusting multiple variables or matching their propensity scores.

RESULTS

The patients could be classified into 5 clusters, including the normally maintained groups (1st cluster, pH = 7.4; and 2nd cluster, pH = 7.3), recovering group (3rd cluster with pH values from 7.2 to 7.3), aggravating group (4th cluster with pH values from 7.3 to 7.2), and ill-being group (5th cluster, pH < 7.2). The pH clusters had different trends of C-reactive protein (CRP) after 24 hours; the 1st and 2nd pH clusters had lower levels, but the 3rd to 5th pH clusters had an increasing trend of CRP. The 1st pH cluster had the best survival rates, and the 3rd to 5th pH clusters had the worst survival rates. This survival difference was significant despite adjusting for other variables or matching propensity scores.

CONCLUSIONS

Initial trajectories of acidosis determine subsequent worse outcomes, such as mortality and inflammation, in patients undergoing CRRT due to AKI.

Associations of Metabolic Syndrome and Abdominal Obesity with Anion Gap Metabolic Acidosis among US Adults

BACKGROUND

Obesity is a recently identified risk factor for metabolic acidosis and anion gap elevations in the absence of CKD. Metabolic acidosis is a treatable condition with substantial adverse effects on human health. Additional investigations are needed to characterize at-risk populations and explore potential mechanisms. We hypothesized metabolic syndrome (MetS) and waist circumference (WC) would be closely associated with this pathology.

METHODS

Adult participants from NHANES 1999-2018 meeting study criteria were compiled as main (n=31,163) and fasting (n=12,860) cohorts. Regression models adjusted for dietary acid, eGFR, and other factors examined associations of WC and MetS features with anion gap metabolic acidosis and its components (serum bicarbonate ≤23 mEq/L and anion gap >95th percentile).

RESULTS

Greater WC and MetS features were associated with progressively lower bicarbonate, higher anion gap, and greater odds ratios (OR) of metabolic acidosis (MA) and anion gap metabolic acidosis (AGMA). Compared with the reference, participants with the highest WC had ORs for MA and AGMA of 2.26; 95% CI, 1.96 to 2.62 and 2.89; 95% CI, 1.97 to 4.21; those with three and four versus zero MetS features had ORs for AGMA of 2.52; 95% CI, 1.95 to 2.94 and 3.05; 95% CI, 2.16 to 3.82. Associations of body mass index with outcomes were attenuated or absent after adjustment for WC or MetS. Findings were preserved after excluding eGFR <90 ml/min per 1.73 m² and albuminuria. A lower MA cutoff (<22 mEq/L) raised the estimate of association between MetS and MA (OR for three and four vs zero features: 3.56; 95% CI, 2.53 to 5.02 and 5.44; 95% CI, 3.66 to 8.08).

CONCLUSIONS

Metabolic diseases are characterized by metabolic acidosis and anion gap elevations. Metabolic dysfunction may predispose patients without CKD to systemic acidosis from endogenous sources. Comprehensive acid-base analyses may be informative in patients with metabolic diseases.

Metabolic Acidosis is Associated With Acute Kidney Injury in Patients With CKD

Introduction

Metabolic acidosis in patients with chronic kidney disease (CKD) results from a loss of kidney function. It has been associated with CKD progression, all-cause mortality, and other adverse outcomes. We aimed to determine whether metabolic acidosis is associated with a higher risk of acute kidney injury (AKI).

Methods

This was a retrospective cohort study. Using electronic health records and administrative data, we enrolled 2 North American cohorts of patients with CKD Stages G3-G5 as follows: (i) 136,067 patients in the US electronic medical record (EMR) based cohort; and (ii) 34,957 patients in the Manitoba claims-based cohort. The primary exposure was metabolic acidosis (serum bicarbonate between 12 mEq/l and <22 mEq/l). The primary outcome was the development of AKI (defined using ICD-9 and 10 codes at hospital admission or a laboratory-based definition based on Kidney Disease: Improving Global Outcomes guidelines). We applied Cox proportional hazards regression models adjusting for relevant demographic and clinical characteristics.

Results

In both cohorts, metabolic acidosis was associated with AKI: hazard ratio (HR) 1.57 (95% confidence interval [CI] 1.52-1.61) in the US EMR cohort, and HR 1.65 (95% CI 1.58-1.73) in the Manitoba claims cohort. The association was consistent when serum bicarbonate was treated as a continuous variable, and in multiple subgroups, and sensitivity analyses including those adjusting for albuminuria.

Conclusion

Metabolic acidosis is associated with a higher risk of AKI in patients with CKD. AKI should be considered as an outcome in studies of treatments for patients with metabolic acidosis.

Acid-Mediated Kidney Injury Across the Spectrum of Metabolic Acidosis

Metabolic acidosis affects about 15% of patients with chronic kidney disease. As kidney function declines, the kidneys progressively fail to eliminate acid, primarily reflected by a decrease in ammonium and titratable acid excretion. Several studies have shown that the net acid load remains unchanged in patients with reduced kidney function; the ensuing acid accumulation can precede overt metabolic acidosis, and thus, indicators of urinary acid or potential base excretion, such as ammonium and citrate, may serve as early signals of impending metabolic acidosis. Acid retention, with or without overt metabolic acidosis, initiates compensatory responses that can promote tubulointerstitial fibrosis via intrarenal complement activation and upregulation of endothelin-1, angiotensin II, and aldosterone pathways. The net effect is a cycle between acid accumulation and kidney injury. Results from small- to medium-sized interventional trials suggest that interrupting this cycle through base administration can prevent further kidney injury. While these findings inform current clinical practice guidelines, large-scale clinical trials are still necessary to prove that base therapy can limit chronic kidney disease progression or associated adverse events.

Importance of Metabolic Acidosis as a Health Risk in Chronic Kidney Disease

Human kidneys are well adapted to excrete the daily acid load from diet and metabolism in order to maintain homeostasis. In approximately 30% of patients with more advanced stages of CKD, these homeostatic processes are no longer adequate, resulting in metabolic acidosis. Potential deleterious effects of chronic metabolic acidosis in CKD, including muscle wasting, bone demineralization, hyperkalemia, and more rapid progression of CKD, have been well cataloged. Based primarily upon concerns related to nutrition and bone disease, early Kidney Disease Outcomes Quality Initiative guidelines recommended treating metabolic acidosis with alkali therapy targeting a serum bicarbonate ≥22 mEq/L. More recent guidelines have suggested similar targets based upon potential slowing of CKD progression. However, appropriately powered, long-term, randomized controlled trials to study efficacy and safety of alkali therapy for these outcomes are largely lacking. As a result, practice among physicians varies, underscoring the complexity of treatment of chronic metabolic acidosis in real-world CKD practice. Novel treatment approaches and rigorous phase 3 trials may resolve some of this controversy in the coming years. Metabolic acidosis is an important complication of CKD, and where it "falls" in the priority schema of CKD care will depend upon the generation of strong clinical evidence.

Effects of Oral Bicarbonate Supplementation on the Cardiovascular Risk Factors and Serum Nutritional Markers in Non-Dialysed Chronic Kidney Disease Patients

Background and Objectives: Kidneys play a key role in maintaining the acid−base balance. The aim of this study was to evaluate the effect of a 3-month oral sodium bicarbonate administration on arterial wall stiffness, arterial pressure and serum nutritional markers in non-dialysed patients with chronic kidney disease (CKD) stages 3−5 and metabolic acidosis. Methods: Eighteen CKD patients with eGFR < 45 mL/min/1.73 m2 and capillary blood bicarbonate (HCO3) < 22 mmol/L were enrolled in this single-centre, prospective study. Anthropometric parameters, pulse wave velocity, 24-h ambulatory blood pressure measurements, blood and urine parameters were assessed at the beginning and at the end of the study. The patients received supplementation with 2 g of sodium bicarbonate daily for three months. Results: A significant increase of pH: 7.32 ± 0.06 to 7.36 ± 0.06; p = 0.025, HCO3 from 18.7 mmol/L (17.7−21.3) to 22.2 mmol/L (20.2−23.9); p < 0.001 and a decrease in base excess from −6.0 ± 2.4 to −1.9 ± 3.1 mmol/L; p < 0.001 were found. An increase in serum total protein from 62.7 ± 6.9 to 65.8 ± 6.2; p < 0.013 and albumin from 37.3 ± 5.4 to 39.4 ± 4.8; p < 0.037 but, also, NT-pro-BNP (N-Terminal Pro-B-Type Natriuretic Peptide) from 794.7 (291.2−1819.0) to 1247.10 (384.7−4545.0); p < 0.006, CRP(C Reactive Protein) from 1.3 (0.7−2.9) to 2.8 (1.1−3.1); p < 0.025 and PTH (parathyroid hormone) from 21.5 ± 13.7 to 27.01 ± 16.3; p < 0.006 were observed, as well as an increase in erythrocyte count from 3.4 ± 0.6 to 3.6 ± 0.6; p < 0.004, haemoglobin from 10.2 ± 2.0 to 11.00 ± 1.7; p < 0.006 and haematocrit from 31.6 ± 6.00 to 33.6 ± 4.8; p < 0.009. The mean eGFR during sodium bicarbonate administration did not change significantly: There were no significant differences in pulse wave velocity or in the systolic and diastolic BP values. Conclusion: The administration of sodium bicarbonate in non-dialysed CKD patients in stages 3−5 improves the parameters of metabolic acidosis and serum nutritional markers; however, it does not affect the blood pressure and vascular stiffness.

Elevated Serum Chloride Levels Contribute to a Poor Prognosis in Patients with IgA Nephropathy

Introduction

The identification of reliable prognostic factors is a crucial requirement for patients with IgA nephropathy (IgAN). Here, we explored the relationship between serum chloride levels and prognosis in patients with IgAN.

Methods

We recruited all patients with primary IgAN, as diagnosed by renal biopsy, between 1^st January 2015 and 1^st April 2019. Patients were divided two groups (high chloride group and low chloride group) based on the best cut-off values from survival receiver operating characteristic (ROC) curves. The baseline clinicopathological characteristics of two groups were then compared. Cox proportional hazard models were used to determine the prognostic value of serum chloride levels in patients with IgAN. Finally, we screened reliable prognostic indicators and built a clinical prediction model and validated the performance of the model.

Results

Compared with patients in the high chloride group, patients in the low chloride group had significantly lower levels of 24-hour urinary total protein (24 h-UTP), serum creatinine (sCr), and higher levels of hemoglobin (Hb), albumin (all p < 0.05), and less proportion of Oxford classification grade E1 (endothelial cell proliferation) and T2 (renal tubule atrophy or renal interstitial fibrosis). Cox analysis revealed that serum chloride level ≥ 105.4 mmol/L was a significant and independent risk factor for prognosis in patients with IgAN (p < 0.05). Serum chloride, sCr, T, hypertension, and Hb were used to generate a predictive model for prognosis. Thec-indices of our predictive model were 0.80, 0.86, and 0.78, for 1, 2, and 3 years, respectively; Brier scores were 0.06, 0.09, and 0.16, respectively.

Conclusions

A serum chloride level ≥ 105.4 mmol/l was identified as a significant and independent risk factor for the prognosis of patients with IgAN. A predictive prognosis model was generated using serum chloride, sCr, T, hypertension, and Hb; this model exhibited a good predictive effect.

Increased intrarenal post-glomerular blood flow is a key condition for the development of calcineurin inhibitor-induced renal tubular acidosis in kidney transplant recipients

BACKGROUND

Hyperchloremic metabolic acidosis (HCMA) from renal tubular acidosis (RTA) is common in kidney transplant (KT) recipients. Calcineurin inhibitors (CNIs) are a potential cause of RTA, and whether HCMA is a determinant of poor graft prognosis is controversial.

METHODS

The subjects were living-donor KT recipients (LDKTRs, n = 47) and matched donors (n = 43). All cases of rejection, extrarenal causes, and respiratory disorders were excluded. HCMA was defined as having a [Na+] - [Cl-] value of ≤ 34 or starting alkalization. We determined the potential causes of HCMA in LDKTRs at 3 months (m) and 1 year (y) post-KT. We examined renal hemodynamic parameters in 26 LDKTRs at 1 y post-KT: namely, glomerular filtration rate (GFR), renal plasma flow (RPF), filtration fraction (FF; GFR/RPF) and pre-/post-glomerular vascular resistance (pre-/postVR).

RESULTS

The HCMA incidence in the 3-m post-KT LDKTR group was higher than that of the donors (51.0% vs. 6.9%, p<0.001, adjusted odds ratio: 6.7-15.7). Among adjusted factors, the most dominant HCMA contributor was low hemoglobin concentration (Hb ≤12 g/dL). Compared to non-HCMA cases, HCMA patients had low FF and low post-VR (p = 0.008, 0.003, respectively) suggesting increased intrarenal post-glomerular blood flow. The high pathological score of alternative arteriolar hyalinosis (aah) ≥2 was a significant HCMA risk. The tacrolimus trough level was not high in HCMA but was significantly high in HCMA in the low post-VR setting (p = 0.002).

CONCLUSION

Among LDKTRs, low hemoglobin level is an important contributor to the manifestation of HCMA in the induction period, and increased intrarenal post-glomerular blood flow is a key condition for the development of CNI-induced RTA. This article is protected by copyright. All rights reserved.

Lower bicarbonate level is associated with CKD progression and all-cause mortality: a propensity score matching analysis

Background

Although metabolic acidosis is known as a potential complication of chronic kidney disease (CKD), there is limited information concerning the association between metabolic acidosis and clinical outcomes.

Methods

Five hundred fifty-two patients referred to renal division of Iwata City Hospital from 2015 to 2017 were included as a retrospective CKD cohort, and finally 178 patients with CKD stage III or IV and 20 to 80 years of age were analyzed. We examined the association between serum bicarbonate (HCO₃⁻) levels and clinical outcomes using Kaplan-Meier methods after the matching of baseline characteristics by propensity scores.

Results

Of 178 patients with CKD, patients with lower HCO₃⁻ levels (N = 94), as compared with patients with higher HCO₃⁻ levels (N = 84), were more likely to be male (P < 0.05), had more severe CKD stages (P < 0.05), more frequent use of renin-angiotensin system inhibitor (P < 0.05) or uric acid lowering agent (P < 0.001), heavier body weight (P < 0.001) and lower estimated glomerular filtration rate (P < 0.05). In Kaplan-Meier analysis after propensity score matching, the incidence of composite outcome as the doubling of serum creatinine level from baseline, end-stage kidney disease requiring the initiation of dialysis, or death from any causes was significantly fewer in the higher HCO₃⁻ group than the lower HCO₃⁻ group (N = 57 each group, P = 0.016).

Conclusions

Lower HCO₃⁻ level is significantly associated with the doubling of serum creatinine level, end-stage kidney disease or all-cause mortality in patients with CKD.

Trial registration

This study was registered with the Clinical Trial Registry of the University Hospital Medical Information Network (http://www.umin.ac.jp/, study number: UMIN000044861).

Effects of oral alkali drug therapy on clinical outcomes in pre-dialysis chronic kidney disease patients: a systematic review and meta-analysis

BACKGROUND

Metabolic acidosis accelerates the progression of chronic kidney disease (CKD) and increases the mortality rate. Whether oral alkali drug therapy benefits pre-dialysis CKD patients is controversial. We performed a meta-analysis of the effects of oral alkali drug therapy on major clinical outcomes in pre-dialysis CKD patients.

METHODS

We systematically searched MEDLINE using the Ovid, EMBASE, and Cochrane Library databases without language restriction. We included all eligible clinical studies that involved pre-dialysis CKD adults and compared those who received oral alkali drug therapy with controls.

RESULTS

A total of 18 eligible studies, including 14 randomized controlled trials and 4 cohort studies reported in 19 publications with 3695 participants, were included. Oral alkali drug therapy led to a 55% reduction in renal failure events (relative risk [RR]: 0.45; 95% confidence interval [CI]: 0.25-0.82), a rate of decline in the estimated glomerular filtration rate (eGFR) of 2.59 mL/min/1.73 m² per year (95% CI, 0.88-4.31). There was no significant effect on decline in eGFR events (RR: 0.34; 95% CI: 0.09-1.23), proteinuria (standardized mean difference: -0.32; 95% CI: -1.08 to 0.43), all-cause mortality events (RR: 0.90; 95% CI: 0.40-2.02) and cardiovascular (CV) events (RR: 1.03; 95% CI: 0.32-3.37) compared with the control groups.

CONCLUSION

Based on the available and low-to-moderate certainty evidence, oral alkali drug therapy might potentially reduce the risk of kidney failure events, but no benefit in reducing all-cause mortality events, CV events, decline in eGFR and porteninuria.

Measurement of Urinary Ammonium Using a Commercially Available Plasma Ammonium Assay

Background

Determination of urinary ammonium excretion is helpful in evaluating patients with acid-base disorders, chronic kidney disease, and nephrolithiasis. However, urinary ammonium levels are only measured by specialized laboratories in the United States, limiting widespread implementation. We evaluated the performance of a plasma ammonium assay to quantify urinary ammonium excretion and also determined ammonium stability under a variety of conditions.

Methods

An enzymatic plasma ammonium assay (Randox) was modified to measure urinary ammonium concentration. Urine samples were diluted 40-fold and then assayed on an Abbott Architect ci8200 analyzer. Assay precision, limit of quantitation, and linearity were determined. The method was compared against the formalin titration method, and stability studies were conducted at different temperatures and pH.

Results

After dilution, the assay had total precision of 18% at 2.54 mmol/L, 5% at 15.58 mmol/L, and 2% at 29.49 mmol/L, with a limit of quantitation of 2.92 mmol/L. Assay performance was linear in the range of 0.7-45 mmol/L. Method comparison against the formalin method showed a slope of 0.98 and intercept of -0.37 mmol/L. Urinary ammonium was determined to be stable for 48 hours at room temperature and for 9 days at 4°C and -20°C at pH 5.6-6.3. Ammonium was less stable at pH 3.8 and 8.5. When stored at -80°C, urinary ammonium was stable for at least 24 months.

Conclusions

The modified enzymatic plasma ammonium assay reliably quantifies urine ammonium at physiologic concentrations. It compares well with the formalin titration method and is suitable for routine clinical use on an automated chemistry analyzer.

Diagnosing metabolic acidosis in chronic kidney disease: importance of blood pH and serum anion gap

Metabolic acidosis is one of the most common complications of chronic kidney disease (CKD). It is associated with the progression of CKD, and many other functional impairments. Until recently, only serum bicarbonate levels have been used to evaluate acid-base changes in patients with reduced kidney function. However, recent emerging evidence suggests that nephrologists should reevaluate the clinical approach for diagnosing metabolic acidosis in patients with CKD based on two perspectives; pH and anion gap. Biochemistry and physiology textbooks clearly indicate that blood pH is the most important acid-base parameter for cellular function. Therefore, it is important to determine if the prognostic impact of hypobicarbonatemia varies according to pH level. A recent cohort study of CKD patients showed that venous pH modified the association between a low bicarbonate level and the progression of CKD. Furthermore, acidosis with a high anion gap has recently been recognized as an important prognostic factor, because veverimer, a nonabsorbable hydrochloride-binding polymer, has been shown to improve kidney function and decrease the anion gap. Acidosis with high anion gap frequently develops in later stages of CKD. Therefore, the anion gap is a time-varying factor and renal function (estimated glomerular filtration rate) is a time-dependent confounder for the anion gap and renal outcomes. Recent analyses using marginal structural models showed that acidosis with a high anion gap was associated with a high risk of CKD. Based on these observations, reconsideration of the clinical approach to diagnosing and treating metabolic acidosis in CKD may be warranted.

Serum bicarbonate is associated with kidney outcomes in autosomal dominant polycystic kidney disease

BACKGROUND

Metabolic acidosis accelerates progression of chronic kidney disease, but whether this is also true for autosomal dominant polycystic kidney disease (ADPKD) is unknown.

METHODS

Patients with ADPKD from the DIPAK (Developing Interventions to halt Progression of ADPKD) trial were included [n = 296, estimated glomerular filtration rate (eGFR) 50 ± 11 mL/min/1.73 m2, 2.5 years follow-up]. Outcomes were worsening kidney function (30% decrease in eGFR or kidney failure), annual eGFR change and height-adjusted total kidney and liver volumes (htTKV and htTLV). Cox and linear regressions were adjusted for prognostic markers for ADPKD [Mayo image class and predicting renal outcomes in ADPKD (PROPKD) scores] and acid-base parameters (urinary ammonium excretion).

RESULTS

Patients in the lowest tertile of baseline serum bicarbonate (23.1 ± 1.6 mmol/L) had a significantly greater risk of worsening kidney function [hazard ratio = 2.95, 95% confidence interval (CI) 1.21-7.19] compared with patients in the highest tertile (serum bicarbonate 29.0 ± 1.3 mmol/L). Each mmol/L decrease in serum bicarbonate increased the risk of worsening kidney function by 21% in the fully adjusted model (hazard ratio = 1.21, 95% CI 1.06-1.37). Each mmol/L decrease of serum bicarbonate was also associated with further eGFR decline (-0.12 mL/min/1.73 m2/year, 95% CI -0.20 to -0.03). Serum bicarbonate was not associated with changes in htTKV or htTLV growth.

CONCLUSIONS

In patients with ADPKD, a lower serum bicarbonate within the normal range predicts worse kidney outcomes independent of established prognostic factors for ADPKD and independent of urine ammonium excretion. Serum bicarbonate may add to prognostic models and should be explored as a treatment target in ADPKD.

Prevalence of Metabolic Acidosis Among Patients with Chronic Kidney Disease and Hyperkalemia

INTRODUCTION

Although hyperkalemia and metabolic acidosis often co-occur in patients with chronic kidney disease (CKD), the prevalence of metabolic acidosis among patients with CKD and hyperkalemia is understudied. Therefore, we used medical record data from the Research Action for Health Network to estimate this prevalence.

METHODS

Adult patients with CKD stage 3-5, ≥ 1 outpatient potassium value > 5.0 mEq/l, and ≥ 1 outpatient bicarbonate value available were identified. Patients with end stage kidney disease (ESKD) in the prior year were excluded. The prevalence of metabolic acidosis in each calendar year from 2014 to 2017 among patients with CKD and hyperkalemia was estimated using two definitions of hyperkalemia (potassium > 5.0 mEq/l and > 5.5 mEq/l) and metabolic acidosis (bicarbonate < 18 mEq/l and < 22 mEq/l).

RESULTS

In the 2017 patient cohort and among patients with CKD and hyperkalemia, patients with metabolic acidosis were younger (69 versus 74 years), more likely to have advanced CKD (35% versus 13%), and use oral sodium bicarbonate (21% versus 4%) than patients without metabolic acidosis. The prevalence of metabolic acidosis (< 22 mEq/l) ranged from 25 to 29% when hyperkalemia was defined by potassium > 5.0 mEq/l and ranged from 33 to 39% when hyperkalemia was defined by potassium > 5.5 mEq/l.

CONCLUSION

Results demonstrated that prevalence estimates of metabolic acidosis varied based on the definition of hyperkalemia and metabolic acidosis utilized.

Retrospective cohort study of changes in estimated glomerular filtration rate for patients prescribed a low carb diet

PURPOSE OF REVIEW

Obesity and diabetes contribute to chronic kidney disease (CKD) and accelerate the loss of kidney function. Low carbohydrate diets (LCDs) are associated with weight loss and improved diabetes control. Compared to the typical Western diet, LCDs contain more protein, so individuals with CKD are not included in studies of LCDs. Therefore, there are no studies of LCDs for weight loss and their effects on kidney function.

RECENT FINDINGS

Obesity, hyperglycemia, and hyperinsulinemia can be detrimental to kidney function. LCDs may improve kidney function in patients with obesity and diabetes because they are associated with weight loss, improve blood sugar control, and decrease endogenous insulin production and exogenous insulin requirements.

SUMMARY

In this study, for patients with mildly reduced and moderately to severely reduced kidney function who were prescribed an LCD, their estimated glomerular filtration rate (eGFR) was either unchanged or improved. For those with normal or elevated eGFR, their kidney function was slightly decreased. For those without diabetes, greater weight loss was associated with improved eGFR. Future studies should prospectively measure low carbohydrate dietary adherence and physical activity and directly measure changes in GFR and albuminuria for participants with CKD before and during that diet.

Sodium Bicarbonate Prescription and Extracellular Volume Increase: Real-world Data Results from the AlcalUN Study

Oral alkalization with sodium bicarbonate (NaHCO₃ ) or citrate is prescribed for conditions ranging from metabolic acidosis to nephrolithiasis. Although most nephrologists/urologists use this method routinely, extracellular volume (ECV) increase is the main feared adverse event reported for NaHCO₃ . Thus far, no trial has specifically studied this issue in a real-world setting. AlcalUN (NCT03035812) is a multicentric, prospective, open-label cohort study with nationwide (France) enrollment in 18 (public and private) nephrology/urology units. Participants were adult outpatients requiring chronic (>1 month) oral alkalization by either NaHCO₃ -containing or no-NaHCO₃ -containing agents. The ECV increase (primary outcome) was judged based on body weight increase (ΔBW), blood pressure increase (ΔBP), and/or new-onset edema at the first follow-up visit (V1). From February 2017 to February 2020, 156 patients were enrolled. After a median 106 days of treatment, 91 (72%) patients reached the primary outcome. They had lower systolic (135 (125, 141) vs. 141 (130, 150), P = 0.02) and diastolic (77 (67, 85) vs. 85 (73, 90), P = 0.03) BP values, a higher plasma chloride (106.0 (105.0, 109.0) vs. 105.0 (102.0, 107.0), P = 0.02) at baseline, and a less frequent history of nephrolithiasis (32 vs. 56%, P = 0.02). Patients experienced mainly slight ΔBP (< 10 mmHg). The primary outcome was not associated (P = 0.79) with the study treatment (129 received NaHCO₃ and 27 received citrate). We subsequently developed three different models of propensity score matching; each confirmed our results. Chronic oral alkalization with NaHCO₃ is no longer associated with an ECV increase compared to citrate in real-life settings.

Nutritional Adequacy of Animal-Based and Plant-Based Asian Diets for Chronic Kidney Disease Patients: A Modeling Study

Plant-based low protein diets (LPDs) have gained popularity for managing chronic kidney disease (CKD) patients. The nutritional adequacy of these and other LPDs prescribed for CKD patients have not been carefully examined. This study assessed the nutrient composition of such LPDs and moderately high protein diets (MHPDs) that might be prescribed for patients in the Asia Pacific region with CKD who are not dialyzed or undergoing maintenance dialysis. Conventional diets containing at least 50% animal-based proteins and plant-based diets were also planned with protein prescriptions of 0.5 to 0.8 g/kg/day and MHPDs with protein prescriptions of 1.0 to 1.2 g/kg/day. Plant-based, lacto-, ovo-, and lacto-ovo-vegetarian and vegan LPDs and MHPDs were planned by replacing some or all of the animal proteins from the conventional diet. With 0.5 g protein/kg/day, all diets were below the Recommended Dietary Allowances (RDA) for at least one essential amino acid (EAA). At a protein prescription of 0.6 g/kg/day, only the conventional LPD met the RDA for all EAAs. This deficiency with the plant-based LPDs persisted even with several plant food substitutions. With a protein prescription ≥0.7 g/kg/day, all the plant-based and vegetarian LPDs provided the RDA for all EAA. The plant-based and vegetarian diets also contained relatively greater potassium, phosphorus, and calcium content but lower long-chain n-3 polyunsaturated fatty acids and vitamin B-12 than the conventional diet. Other essential micronutrients were commonly below the RDA even at higher protein intakes. The low contents of some essential micronutrients were found in both animal-based and plant-based diets. Prescription of all LPDs for CKD patients, especially plant-based and vegetarian LPDs, requires careful planning to ensure the adequacy of all nutrients, particularly essential amino acids. Consideration should be given to supplementing all animal-based and plant-based LPDs and MHPDs with multivitamins and certain trace elements.

Obesity, Anion Accumulation, and Anion Gap Metabolic Acidosis: A Cohort Study

Background

Obesity is associated with low serum bicarbonate, an indicator of metabolic acidosis and a CKD risk factor. To further characterize acid-base disturbance and subclinical metabolic acidosis in this population, we examined prospective associations of body mass index (BMI) with elevated anion gap and whether anion gap values in obesity associate with low bicarbonate.

Methods

Data from adult outpatients (n=94,448) in the Bronx, New York were collected from 2010 to 2018. Mixed effects models and Cox proportional hazards models were used to examine associations of BMI with elevated anion gap and anion gap metabolic acidosis and of baseline anion gap with incident low bicarbonate and anion gap metabolic acidosis. Anion gap was defined using traditional and albumin-corrected calculations.

Results

Greater BMI was associated with higher anion gap over time and with progressively greater risk of developing an elevated anion gap (hazard ratio [HR] for body mass index [BMI]≥40 kg/m² versus 18 to <25 kg/m², 1.32; 95% confidence interval [95% CI], 1.23 to 1.42 for traditional and HR for BMI≥40 kg/m² versus 18 to <25 kg/m², 1.74; 95% CI, 1.63 to 1.85 for corrected). Higher BMI was also associated with increased risk of developing anion gap metabolic acidosis (HR for BMI≥40 kg/m², 1.53; 95% CI, 1.39 to 1.69). Among patients with obesity, higher anion gap was associated with increased risk of incident low bicarbonate (HR for fourth versus first quartile, 1.29; 95% CI, 1.23 to 1.44 for traditional and HR for fourth versus first quartile, 1.36; 95% CI, 1.26 to 1.48 for corrected) and higher risk of anion gap metabolic acidosis (HR for fourth versus first quartile, 1.78; 95% CI, 1.59 to 1.99).

Conclusions

Obesity is characterized by unmeasured anion accumulation and acid retention or overproduction. Modest elevations in anion gap among patients with obesity are associated with previously unrecognized anion gap metabolic acidosis.

Association of Time-Updated Anion Gap With Risk of Kidney Failure in Advanced CKD: A Cohort Study

RATIONALE AND OBJECTIVE

High anion gap acidosis frequently develops in patients with advanced chronic kidney disease (CKD) and might be involved in kidney injury. Its impact on kidney outcomes, however, has not been well studied. We sought to examine the association between time-updated anion gap and the risk of kidney failure with replacement therapy (KFRT) among patients with advanced CKD.

STUDY DESIGN

Retrospective cohort study.

SETTING AND PARTICIPANTS

1,168 patients with CKD stages G3b-G5 who had available data on anion gap.

EXPOSURE

High time-updated anion gap defined as values ≥9.2 (top 25th percentile).

OUTCOMES

KFRT and death.

ANALYTICAL APPROACH

Marginal structural models (MSM) were fit to characterize the association between anion gap and study outcomes while accounting for potential time-dependent confounding.

RESULTS

The mean baseline eGFR of the study participants was 28 mL/min/1.73m². Over a median follow-up of 3.1 years, 317 patients progressed to KFRT (7.5/100 patient-years) and 146 died (3.5/100 patient-years). In the MSM, a high anion gap was associated with a higher rate of KFRT (hazard ratio [HR], 3.04; 95% confidence interval [CI], 1.94-4.75; P<0.001). This association was stronger in patients with baseline eGFR of <30 mL/min/1.73m² (P for interaction=0.05). High anion gap was also associated with a higher mortality rate (HR, 5.56; 95% CI, 2.95-10.5; P<0.001). Sensitivity analyses with different definitions of high anion gap showed similar results.

LIMITATIONS

Observational study design; selection bias due clinical indications for measuring anion gap.

CONCLUSION

Among patients with advanced CKD, high anion gap was associated with an increased risk of progression to KFRT and death.

Association of dietary acid load with serum bicarbonate in chronic kidney disease (CKD) patients

BACKGROUND/OBJECTIVES

Diet can affect the acid-base status depending on the balance between the intake of acid-inducing foods and base-inducing foods. The purpose of this study was to estimate the dietary acid load and evaluate its association with serum bicarbonate in patients with stages 3 and 4 chronic kidney disease.

SUBJECTS/METHODS

One hundred adults (aged ≥ 20 years) with chronic kidney disease (CKD) stages 3 and 4 were enrolled in a cross-sectional study. A food diary was used to estimate the animal and plant protein intakes, which were used in the potential renal acid load (PRAL) formula described by Remer and Manz. PRAL was divided into quartiles. Regression models unadjusted and adjusted for age, gender, body mass index, diabetes, systolic and diastolic blood pressure, creatinine clearance were performed using the stepwise regression method.

RESULTS

The median level (25th, 75th percentiles) of PRAL was 8.3 mEq/day (1.6, 15.6). The highest quartile of PRAL had a higher consumption of animal protein (77.8 ± 10.9%) and a reduced consumption of plant protein (22.2 ± 10.9%), compared to the lowest quartile (59.5 ± 18.6% animal protein, 40.5 ± 18.6% plant protein), p for trend <0.0001. In the adjusted analysis, a significant association was observed between the highest quartile of PRAL and serum bicarbonate in CKD patients compared to the lowest quartile (β: 2.07, 95% CI: 0.21-3.92). According to the multiple linear regression, for each increase of 1 unit of PRAL there was a reduction of 0.25 mmol/L in serum bicarbonate (HCO₃). Using the stepwise method, animal protein intake and PRAL were determinants of HCO₃ (r = 0.49).

CONCLUSIONS

In CKD patients of stages 3 and 4, the dietary acid load was associated with HCO₃. Limiting dietary acid load could be a complementary approach in the dietary treatment of CKD. In addition, studies are needed to analyze the effect of replacing animal protein with plant protein.

Dietary Plant Protein and Mortality Among Patients Receiving Maintenance Hemodialysis: A Cohort Study

RATIONALE & OBJECTIVE

Although greater dietary intake of protein has been associated with beneficial health effects among patients receiving maintenance hemodialysis (MHD), the effects of plant protein intake are less certain. We studied the association of the proportion of protein intake derived from plant sources with the risk of mortality among patients receiving MHD and explored factors that may modify these associations.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

1,119 Chinese hemodialysis patients aged over 18 years receiving MHD in 2014-2015.

PREDICTORS

The proportion of plant protein intake to total protein intake.

OUTCOMES

All-cause mortality and cardiovascular disease (CVD) mortality.

ANALYTICAL APPROACH

Segmented regression models were fit to examine the association of plant protein intake proportion with the risk of all-cause mortality and CVD mortality. Multivariable-adjusted Cox proportional and cause-specific hazards models were used to estimate the hazard ratios (HR) and 95% CI for these outcomes.

RESULTS

The means of plant protein intake normalized to ideal body weight and plant protein intake proportion were 0.6±0.2 (SD) g/kg per day and 0.538±0.134, respectively. During a median follow-up period of 28.0 months, 249 deaths occurred, with 146 of these deaths resulting from CVD. Overall, there was a U-shaped association between plant protein intake proportion and the risk of all-cause mortality, with an inflection point at 45%. Among patients with a plant protein intake proportion<45%, there was a 17% lower rate of mortality with each 5% greater plant protein intake proportion (HR, 0.83 [95% CI, 0.73-0.96]). Among patients with plant protein intake proportion≥45%, there was a 9% greater rate of mortality with each 5% greater plant protein intake proportion. A similar U-shaped association was observed for CVD mortality, with an inflection point at 44%.

LIMITATIONS

Observational study, potential unmeasured confounding.

CONCLUSIONS

There was a U-shaped association between plant protein intake proportion and the risk of all-cause and cardiovascular mortality in MHD patients. If confirmed, these findings suggest a potential avenue to improve outcomes in this patient population.

Metabolic acidosis is associated with increased risk of adverse kidney outcomes and mortality in patients with non-dialysis dependent chronic kidney disease: an observational cohort study

BACKGROUND

Management of chronic kidney disease (CKD) requires the management of risk factors, such as hypertension and albuminuria, that affect CKD progression. Identification of additional modifiable risk factors is necessary to develop new treatment strategies for CKD. We sought to quantify the association of metabolic acidosis with CKD progression and mortality in a large U.S. community-based cohort.

METHODS

In this longitudinal, retrospective cohort study we identified non-dialysis-dependent patients with stage 3‒5 CKD from Optum's de-identified integrated electronic health records. We selected cohorts of patients with confirmed metabolic acidosis or normal serum bicarbonate levels based on 2 consecutive serum bicarbonate values: 12 to < 22 mEq/L or 22-29 mEq/L, respectively, 28‒365 days apart. The primary composite outcome was ≥ 40 % decline in estimated glomerular filtration rate (eGFR), renal replacement therapy (chronic dialysis or kidney transplant), or all-cause mortality (DD40). Secondary outcomes included each component of the composite outcome. Cox proportional hazards models were used for the DD40 outcome and secondary outcomes, while logistic regression models were used for the DD40 outcome at 2 years.

RESULTS

A total of 51,558 patients qualified for the study. The unadjusted 2-year incidence of adverse renal and fatal outcomes was significantly worse among patients in the metabolic acidosis group vs. those who had normal serum bicarbonate levels: 48 % vs. 17 % for DD40, 10 % vs. 4 % for ≥ 40 % decline in eGFR, 20 % vs. 6 % for renal replacement therapy, and 31 % vs. 10 % for all-cause mortality (all P < 0.001). Over a ≤ 10-year period, for each 1-mEq/L increase in serum bicarbonate, the adjusted hazard ratio for DD40 was 0.926 (95 % confidence interval [CI], 0.922-0.930; P < 0.001); over a ≤ 2-year period, the adjusted odds ratio for DD40 was 0.873 (95 % CI, 0.866-0.879; P < 0.001).

CONCLUSIONS

In this large community cohort of patients with stage 3‒5 CKD, the presence of metabolic acidosis was a significant, independent risk factor for the composite adverse outcome of CKD progression, renal replacement therapy, and all-cause mortality (DD40).

Efficacy and Safety of Veverimer in the Treatment of Metabolic Acidosis Caused by Chronic Kidney Disease: A Meta-analysis

Metabolic acidosis is a common complication of chronic kidney disease (CKD). Veverimer is an orally administrated, free amine polymer with high capacity and binding selectivity to hydrochloric acid from the gastrointestinal tract. This study pooled the current evidence of the efficacy and safety of veverimer for the treatment of metabolic acidosis associated with CKD. We conducted a systematic literature search on PubMed, Embase, and Cochrane Central for relevant randomized controlled trials (RCTs) in June 2020. In this study, three RCTs with 548 patients were included in our analysis. The analysis revealed that veverimer was associated with increased bicarbonate level of patients (weight mean difference [WMD] 3.08, 95% confidence interval [CI] [2.40, 3.77], p < 0.001) and improved physical function compared with placebo measured by Kidney Disease and Quality of Life Short Form 36, question 3 (physical functioning domain) (KDQoL-PFD) score (WMD 5.25, 95% CI [1.58, 8.92], p = 0.005). For safety outcomes, both groups exhibited similar risks for developing headache, diarrhea, flatulence, and hyperkalemia. In conclusion, current clinical evidence indicates that veverimer is efficacious and safe against metabolic acidosis related to CKD compared with placebo. Further research comparing long-term veverimer use with traditional alkali therapy is needed.

Relationship between mortality and use of sodium bicarbonate at the time of dialysis initiation: a prospective observational study

Background

Patients with chronic kidney disease often experience metabolic acidosis. Whether oral sodium bicarbonate can reduce mortality in patients with metabolic acidosis has been debated for years. Hence, this study was conducted to evaluate the utility of sodium bicarbonate in patients who will undergo dialysis therapy. In this study, we investigated the effect of oral sodium bicarbonate therapy on mortality in patients with end-stage kidney disease (ESKD) initiated on dialysis therapy.

Methods

We conducted an observational study of patients when they started dialysis therapy. There were 17 centres participating in the Aichi Cohort Study of Prognosis in Patients Newly Initiated into Dialysis. Data were available on patients’ sex, age, use of sodium bicarbonate, drug history, medical history, vital data, and laboratory data. We investigated whether patients on oral sodium bicarbonate for more than three months before dialysis initiation had a better prognosis than those without sodium bicarbonate therapy. The primary outcome was defined as all-cause mortality.

Results

The study included 1524 patients with chronic kidney disease who initiated dialysis between October 2011 and September 2013. Among them, 1030 were men and 492 women, with a mean age of 67.5 ± 13.1 years. Of these, 677 used sodium bicarbonate and 845 did not; 13.6% of the patients in the former group and 21.2% of those in the latter group died by March 2015 (p <  0.001). Even after adjusting for various factors, the use of sodium bicarbonate independently reduced mortality (p <  0.001).

Conclusions

The use of oral sodium bicarbonate at the time of dialysis initiation significantly reduced all-cause mortality in patients undergoing dialysis therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-021-02330-0.

Effect of Bicarbonate on Net Acid Excretion, Blood Pressure, and Metabolism in Patients With and Without CKD: The Acid Base Compensation in CKD Study

RATIONALE & OBJECTIVE

Patients with CKD are at elevated risk of metabolic acidosis due to impaired net acid excretion (NAE). Identifying early markers of acidosis may guide prevention in chronic kidney disease (CKD). This study compared NAE in participants with and without CKD, as well as the NAE, blood pressure (BP), and metabolomic response to bicarbonate supplementation.

STUDY DESIGN

Randomized order, cross-over study with controlled feeding.

SETTING & PARTICIPANTS

Participants consisted of 8 patients with CKD (estimated glomerular filtration rate 30-59mL/min/1.73m² or 60-70mL/min/1.73m² with albuminuria) and 6 patients without CKD. All participants had baseline serum bicarbonate concentrations between 20 and 28 mEq/L; they did not have diabetes mellitus and did not use alkali supplements at baseline.

INTERVENTION

Participants were fed a fixed-acid-load diet with bicarbonate supplementation (7 days) and with sodium chloride control (7 days) in a randomized order, cross-over fashion.

OUTCOMES

Urine NAE, 24-hour ambulatory BP, and 24-hour urine and plasma metabolomic profiles were measured after each period.

RESULTS

During the control period, mean NAE was 28.3±10.2 mEq/d overall without differences across groups (P=0.5). Urine pH, ammonium, and citrate were significantly lower in CKD than in non-CKD (P<0.05 for each). Bicarbonate supplementation reduced NAE and urine ammonium in the CKD group, increased urine pH in both groups (but more in patients with CKD than in those without), and increased; urine citrate in the CKD group (P< 0.2 for interaction for each). Metabolomic analysis revealed several urine organic anions were increased with bicarbonate in CKD, including 3-indoleacetate, citrate/isocitrate, and glutarate. BP was not significantly changed.

LIMITATIONS

Small sample size and short feeding duration.

CONCLUSIONS

Compared to patients without CKD, those with CKD had lower acid excretion in the form of ammonium but also lower base excretion such as citrate and other organic anions, a potential compensation to preserve acid-base homeostasis. In CKD, acid excretion decreased further, but base excretion (eg, citrate) increased in response to alkali. Urine citrate should be evaluated as an early and responsive marker of impaired acid-base homeostasis.

FUNDING

National Institute of Diabetes and Digestive and Kidney Diseases and the Duke O'Brien Center for Kidney Research.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov with study number NCT02427594.

Effectiveness of Chinese herbal medicine combined with Western medicine on deferring dialysis initiation for nondialysis chronic kidney disease stage 5 patients: a multicenter prospective nonrandomized controlled study

Background

In clinical practice, Chinese herbal medicine (CHM) purportedly has beneficial therapeutic effects for chronic kidney disease (CKD), which include delaying disease progression and dialysis initiation. However, there is a lack of high-quality evidence-based results to support this. Therefore, this study aimed to evaluate the efficacy of CHM combined with Western medicine in the treatment of stage 5 CKD.

Methods

This was a prospective nonrandomized controlled study. Stage 5 CKD (nondialysis) patients were recruited form 29 AAA class hospitals across China from July 2014 to April 2019. According to doctors' advice and the patients' wishes, patients were assigned to the CHM group (Western medicine + CHM) and the non-CHM group (Western medicine). Patient demographic data, primary disease, blood pressure, Chinese and Western medical drugs, clinical test results, and time of dialysis initiation were collected during follow-up.

Results

A total of 908 patients were recruited in this study, and 814 patients were finally included for further analysis, including 747 patients in the CHM group and 67 patients in the non-CHM group. 482 patients in the CHM group and 52 patients in the non-CHM group initiated dialysis. The median time of initiating dialysis was 9 (7.90, 10.10) and 3 (0.98,5.02) months in the CHM group and non-CHM group, respectively. The multivariate Cox regression analysis showed that patients in the CHM group had a significantly lower risk of dialysis [adjusted hazard ratio (aHR): 0.38; 95% confidence interval (CI): 0.28, 0.53] compared to those in the non-CHM group. After 1:2 matching, the outcomes of 160 patients were analyzed. The multivariate Cox regression analysis showed that patients in the CHM group had a significantly lower risk of dialysis (aHR: 0.32; 95% CI: 0.21, 0.48) compared to patients in the non-CHM group. Also, the Kaplan-Meier analysis demonstrated that the cumulative incidence of dialysis in the CHM group was significantly lower than that in the non-CHM group (log-rank test, P<0.001) before and after matching.

Conclusions

This study suggest that the combination of CHM and Western medicine could effectively reduce the incidence of dialysis and delay the time of dialysis initiation in stage 5 CKD patients.

Metabolic Acidosis in CKD: A Review of Recent Findings

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

Exhausted Capacity of Bicarbonate Buffer in Renal Failure Diagnosed Using Point of Care Analyzer

BACKGROUND

Metabolic acidosis in patients with chronic kidney disease (CKD) is a common complication. A bicarbonate concentration in venous blood (V-HCO₃^-) is a key index for diagnosis and treatment initiation. The aim of our study is to evaluate usability of acid-base balance parameters of in blood taken simultaneously from peripheral artery and the vein.

METHODS

A total of 49 patients (median age 66 years [interquartile range IQR 45-75]), with CKD stage G4 or G5 were enrolled in this cross-sectional study. All patients were qualified for arteriovenous fistula creation in pre-dialysis period. The samples were taken during surgery, directly after dissection, and evaluated in a point of care testing analyzer. The arteriovenous difference in bicarbonate levels (Δ-HCO₃^-) was calculated. According to glomerular filtration rate (eGFR) the group was divided into Group A eGFR ≥ 10 mL/min/1.73 m²) and Group B eGFR < 10 mL/min/1.73 m²).

RESULTS

In Group A Δ-HCO₃^- was significantly higher compared to Group B. No such differences were observed in the case of V-HCO₃^-. Δ-HCO₃^- positively correlated with eGFR. The discriminative power of Δ-HCO₃^- for predicting eGFR < 10 mL/min/1.73 m² was 0.72 (95% confidence interval [CI] = 0.551-0.88; p = 0.01) which provided 67% sensitivity and 75% specificity. The best cut-off was 0.5 mmol/L.

CONCLUSIONS

The Δ-HCO₃^- lower than 0.5 mmol/L may be used as predictor of exhaust buffer capacity. The value of this tool should be tested in larger population.

Low serum total CO2 and its association with mortality in patients being followed up in the nephrology outpatients clinic

Large-scale studies have not been conducted to assess whether serum hypobicarbonatemia increases the risk for kidney function deterioration and mortality among East-Asians. We aimed to determine the association between serum total CO₂ (TCO₂) concentrations measured at the first outpatient visit and clinical outcomes. In this multicenter cohort study, a total of 42,231 adult nephrology outpatients from 2001 to 2016 were included. End-stage renal disease (ESRD) patients on dialysis within 3 months of the first visit were excluded. Instrumental variable (IV) was used to define regions based on the proportion of patients with serum TCO₂ < 22 mEq/L. The crude mortality rate was 12.2% during a median 77.0-month follow-up period. The Cox-proportional hazard regression model adjusted for initial kidney function, alkali supplementation, and the use of diuretics demonstrated that low TCO₂ concentration was not associated with progression to ESRD, but significantly increased the risk of death. The IV analysis also confirmed a significant association between initial TCO₂ concentration and mortality (HR 0.56; 95% CI 0.49–0.64). This result was consistently significant regardless of the underlying renal function. In conclusion, low TCO₂ levels are significantly associated with mortality but not with progression to ESRD in patients with ambulatory care.

The therapeutic importance of acid-base balance

Baking soda and vinegar have been used as home remedies for generations and today we are only a mouse-click away from claims that baking soda, lemon juice, and apple cider vinegar are miracles cures for everything from cancer to COVID-19. Despite these specious claims, the therapeutic value of controlling acid-base balance is indisputable and is the basis of Food and Drug Administration-approved treatments for constipation, epilepsy, metabolic acidosis, and peptic ulcers. In this narrative review, we present evidence in support of the current and potential therapeutic value of countering local and systemic acid-base imbalances, several of which do in fact involve the administration of baking soda (sodium bicarbonate). Furthermore, we discuss the side effects of pharmaceuticals on acid-base balance as well as the influence of acid-base status on the pharmacokinetic properties of drugs. Our review considers all major organ systems as well as information relevant to several clinical specialties such as anesthesiology, infectious disease, oncology, dentistry, and surgery.

A Systematic Review and Meta-Analysis on Effects of Bicarbonate Therapy on Kidney Outcomes

Aim

Preclinical studies suggest treatment of metabolic acidosis may slow chronic kidney disease (CKD) progression. This systematic review aimed to summarize evidence from randomized controlled trials (RCTs) concerning the benefits and risks of bicarbonate therapy on kidney outcomes.

Methods

Medline, EMBASE, and Cochrane databases were searched for RCTs with ≥3 months’ follow-up in patients with CKD (estimated glomerular filtration rate [eGFR] ≤60 ml/min per 1.73 m² and/or proteinuria) comparing the effects of sodium bicarbonate with placebo/no study medication on kidney outcomes. The primary outcome was change from baseline to last measurement in kidney function measured as either eGFR or creatinine clearance. Treatment effects were summarized using random-effects meta-analysis.

Results

Fifteen trials (2445 participants, median follow-up 12 months) were eligible for inclusion. Compared with placebo or no study medication, sodium bicarbonate retarded the decline in kidney function (standardized mean difference [SMD]: 0.26; 95% confidence interval [CI]: 0.13–0.40; I² = 50%, low certainty evidence), and reduced the risk of end-stage kidney failure (risk ratio [RR]: 0.53; 95% CI 0.32–0.89; I² = 69%, low certainty evidence). The effect of sodium bicarbonate on proteinuria (SMD: −0.09; 95% CI −0.27 to 0.09; I² = 28%, very low certainty evidence), systolic blood pressure (weighted mean difference [WMD]: −0.57 mm Hg; 95% CI −2.32 to 1.18; I² = 0%, low certainty evidence), all-cause death (RR: 0.81; 95% CI: 0.39–1.68; I² = 30%; very low certainty evidence) and edema (RR: 1.16; 95% CI: 0.90–1.50; I² = 28%; low certainty evidence) were uncertain.

Conclusion

Sodium bicarbonate may slow CKD progression. Adequately powered randomized trials are required to evaluate the benefits and risks of sodium bicarbonate in CKD.

Association of serum uromodulin with mortality and cardiovascular disease in the elderly-the Cardiovascular Health Study

BACKGROUND

Uromodulin (UMOD) is released by renal tubular cells into the serum (sUMOD) and urine. Lower urine UMOD has been linked to mortality and cardiovascular disease but much less is known about sUMOD. We evaluated the association of sUMOD with these outcomes in community-dwelling older adults.

METHODS

We measured sUMOD in a random subcohort of 933 participants enrolled in the Cardiovascular Health Study. The associations of sUMOD with all-cause mortality, incident heart failure (HF) and incident cardiovascular disease (CVD; myocardial infarction, stroke and mortality due to coronary disease or stroke) were evaluated using multivariable Cox regression, adjusting for study participants' demographics, estimated glomerular filtration rate (eGFR), albuminuria and CVD risk factors. Generalized additive models with splines were used to address the functional form of sUMOD with outcomes. Due to nonlinear associations of sUMOD with all outcomes, 2.5% of the values on either end of the sUMOD distribution were excluded from the analyses, limiting the range of sUMOD to 34.3-267.1 ng/mL.

RESULTS

The mean age was 78 ± 5 years, 40% were male, sUMOD level was 127 ± 64 ng/mL, eGFR was 63 mL/min/1.73 m2 and 42% had CKD defined as eGFR <60 mL/min/1.73 m2. Patients in the lower sUMOD quartiles had lower eGFR and higher albuminuria (P < 0.01, respectively). During a median follow-up of 9.9 years, 805 patients died, 283 developed HF and 274 developed CVD. In multivariable analysis, higher sUMOD was significantly associated with a lower hazard for mortality {hazard ratio [HR] 0.89 [95% confidence interval (CI) 0.80-0.99] per 1 standard deviation (SD) higher sUMOD}, CVD [HR 0.80 (95% CI 0.67-0.96)] and the composite endpoint [HR 0.88 (95% CI 0.78-0.99)]; the association with HF was not statistically significant [HR 0.84 (95% CI 0.70-1.01)].

CONCLUSION

Higher sUMOD is independently associated with a lower risk for mortality and CVD in older adults.

Development of a Biomarker Panel to Distinguish Risk of Progressive Chronic Kidney Disease

Chronic kidney disease (CKD) patients typically progress to kidney failure, but the rate of progression differs per patient or may not occur at all. Current CKD screening methods are sub-optimal at predicting progressive kidney function decline. This investigation develops a model for predicting progressive CKD based on a panel of biomarkers representing the pathophysiological processes of CKD, kidney function, and common CKD comorbidities. Two patient cohorts are utilised: The CKD Queensland Registry (n = 418), termed the Biomarker Discovery cohort; and the CKD Biobank (n = 62), termed the Predictive Model cohort. Progression status is assigned with a composite outcome of a ≥30% decline in eGFR from baseline, initiation of dialysis, or kidney transplantation. Baseline biomarker measurements are compared between progressive and non-progressive patients via logistic regression. In the Biomarker Discovery cohort, 13 biomarkers differed significantly between progressive and non-progressive patients, while 10 differed in the Predictive Model cohort. From this, a predictive model, based on a biomarker panel of serum creatinine, osteopontin, tryptase, urea, and eGFR, was calculated via linear discriminant analysis. This model has an accuracy of 84.3% when predicting future progressive CKD at baseline, greater than eGFR (66.1%), sCr (67.7%), albuminuria (53.2%), or albumin-creatinine ratio (53.2%).

Chronic Metabolic Acidosis in Chronic Kidney Disease

BACKGROUND

Metabolic acidosis may be diagnosed as chronic (cMA) if it persists for at least 5 days, although an exact definition has not been provided by any guidelines yet. The most common cause is CKD; numerous less-known diseases can also account for cMA.

SUMMARY

In recent years, CKD-associated cMA has been proposed to induce several clinical complications. The aim of the article was to assess the current clinical evidence for complications and the respective management of CKD-associated cMA. In summary, cMA in CKD most likely promotes protein degradation and loss of bone mineral density. It aggravates CKD progression as indicated by experimental and (partly) clinical data. Therefore, cMA control must be recommended. Besides oral bicarbonate, dietary interventions potentially offer an alternative. Veverimer is a future option for cMA control; further systematic data are needed.

CONCLUSIONS

The most common cause of cMA is CKD. CKD-associated cMA most likely induces a negative protein balance; the exact role on bone metabolism remains uncertain. It presumably aggravates CKD progression. cMA control is recommendable; the serum bicarbonate target level should range around 24 mEq/L. Veverimer may be established as future option for cMA control; further systematic data are needed.