Metabolic Acidosis Is an Independent Risk Factor of Renal Progression in Korean Chronic Kidney Disease Patients: The KNOW-CKD Study Results

Prevalence, Risk Factors, and Management of Metabolic Acidosis in Chronic Kidney Disease Patients: A Multicenter Retrospective Study in Malaysia

Background Metabolic acidosis in chronic kidney disease (CKD) patients has lately gained attention due to the growing evidence of its treatment benefits. This study aims to provide baseline data on the prevalence, risk factors, and current management of metabolic acidosis among the pre-dialysis adult Malaysian CKD population. Methodology This multicenter cross-sectional retrospective study involved pre-dialysis CKD patients above 18 years old on regular nephrology clinic follow-up at three Malaysian government hospitals with nephrology subspecialty. Demographic data, clinical information, laboratory data, and a list of concomitant medications were collected. Factors associated with the occurrence of metabolic acidosis were identified via multiple logistic regression. Results Six hundred and fifty-seven CKD patients were screened for this study, in which only 39.4% (n=259) had available bicarbonate levels. From this, a total of 86.1% (n=223) had metabolic acidosis. Higher estimated glomerular filtration rate (odds ratio (OR) 0.96, 95% confidence interval (CI) 0.93-1.00, p=0.043) and those with cardiovascular disease (OR 0.33, 95% CI 0.15-0.73; p=0.007) were significantly associated with lower odds of metabolic acidosis. There were 43.0% (n=96) on alkali therapy with sodium bicarbonate solution being the most common (n=91, 94.8%). Among those receiving alkali therapy, only 19.8% (n=19) achieved bicarbonate levels of ≥ 22 mEq/L. Conclusion Our study showed that metabolic acidosis was highly prevalent, although few achieved target levels despite supplementation, supporting the need for focused management of metabolic acidosis in the CKD population.

Association between albumin-corrected anion gap level and the risk of acute kidney injury in intensive care unit

PURPOSE

This study was to investigate the association between albumin-corrected anion gap (AG) (ACAG) levels and the risk of acute kidney injury (AKI) in intensive care unit (ICU) patients.

METHODS

The ICU patients of this retrospective cohort study were collected from the Medical Information Mart for Intensive Care IV (MIMIC-IV) database between 2008 and 2019. ACAG = AG + {4.4 - [albumin (g/dl)]} × 2.5. The incidence of AKI was determined using the Kidney Disease: Improving Global Outcomes (KDIGO) definition. The logistic regression model was used to evaluate the association between ACAG levels and the risk of AKI. Subgroup analyses were applied based on age, gender, mechanical ventilation, vasopressors, the Charlson comorbidity index (CCI), and the Simplified Acute Physiology Score II (SAPS II).

RESULTS

Totally, 5586 patients were enrolled, of which 1929 patients (34.53%) occurred AKI. The higher levels of ACAG were associated with the risk of AKI in ICU patients, with the odds ratio (OR) value being 1.23 [95% confidence interval (CI): 1.22-1.24, P = 0.005] in ACAG level between 16.5 and 19.5, and OR value being 1.20 (95% CI 1.16-1.24, P = 0.016) in ACAG level > 19.5. A higher ACAG level was associated with a higher risk of AKI in ICU patients aged < 65 years, in ICU patients of female gender, in ICU patients who used mechanical ventilation, in ICU patients who did not use vasopressors, in patients without cardiogenic shock, and in ICU patients with CCI ≥ 2, and SAPS II > 31 (all P < 0.05).

CONCLUSION

There is an association between ACAG level and the risk of AKI in ICU patients. A higher ACAG value in ICU patients should therefore receive more attention.

NaHCO3 loading causes increased arterial pressure and kidney damage in rats with chronic kidney disease

Sodium bicarbonate (NaHCO3) is commonly utilized as a therapeutic to treat metabolic acidosis in people with chronic kidney disease (CKD). While increased dietary sodium chloride (NaCl) is known to promote volume retention and increase blood pressure, the effects of NaHCO3 loading on blood pressure and volume retention in CKD remain unclear. In the present study, we compared the effects of NaCl and NaHCO3 loading on volume retention, blood pressure, and kidney injury in both 2/3 and 5/6 nephrectomy remnant kidney rats, a well-established rodent model of CKD. We tested the hypothesis that NaCl loading promotes greater volume retention and increases in blood pressure than equimolar NaHCO3. Blood pressure was measured 24 h daily using radio telemetry. NaCl and NaHCO3 were administered in drinking water ad libitum or infused via indwelling catheters. Rats were housed in metabolic cages to determine volume retention. Our data indicate that both NaHCO3 and NaCl promote hypertension and volume retention in remnant kidney rats, with salt-sensitivity increasing with greater renal mass reduction. Importantly, while NaHCO3 intake was less pro-hypertensive than equimolar NaCl intake, NaHCO3 was not benign. NaHCO3 loading significantly elevated blood pressure and promoted volume retention in rats with CKD when compared with control rats receiving tap water. Our findings provide important insight into the effects of sodium loading with NaHCO3 in CKD and indicate that NaHCO3 loading in patients with CKD is unlikely to be benign.

Predictive value of serum human epididymis protein 4 for heart failure in patients with chronic kidney disease

AIM

To investigate the predictive value of human epididymis protein 4 (HE4) for heart failure in patients with chronic kidney disease (CKD).

METHODS

This study retrospectively analyzed the data of 241 patients with CKD admitted to Zhangjiakou First Hospital from January 2019 to January 2021. The subjects were divided into a heart failure (HF) group (n=117) and a non-HF group (n=124) according to whether heart failure occurred. The baseline data and laboratory hematologic indicators (complete set of HE4, blood routine and biochemistry) were collected and analyzed by univariate analysis. Subsequently, the variables that were significant in the correlation analysis were included in a multi-factor logistic regression analysis.

RESULTS

The HF group exhibited higher serum creatinine, HE4, hemoglobin, total cholesterol, triglycerides (TG), high-density lipoprotein (P<0.05), as well as higher B-type natriuretic peptide (BNP), creatine kinase, and creatine kinase-MB than the non-HF group, with significant differences (P<0.05). Spearman's rank correlation analysis revealed that age, HE4, calcium, TG, BNP and left ventricle ejection fraction were associated with the occurrence of heart failure (P<0.05). Multivariate analysis demonstrated that HE4 was a significant factor that could predict the development of heart failure in CKD patients (P<0.01), and the risk of heart failure was higher when HE4>27.2368 pmol/L.

CONCLUSIONS

HE4 is an important factor for predicting the occurrence of heart failure in CKD patients. A higher HE4 level predicts greater possibility of heart failure.

Comparing predictions among competing risks models with rare events: application to KNOW-CKD atudy-a multicentre cohort study of chronic kidney disease

A prognostic model to determine an association between survival outcomes and clinical risk factors, such as the Cox model, has been developed over the past decades in the medical field. Although the data size containing subjects' information gradually increases, the number of events is often relatively low as medical technology develops. Accordingly, poor discrimination and low predicted ability may occur between low- and high-risk groups. The main goal of this study was to evaluate the predicted probabilities with three existing competing risks models in variation with censoring rates. Three methods were illustrated and compared in a longitudinal study of a nationwide prospective cohort of patients with chronic kidney disease in Korea. The prediction accuracy and discrimination ability of the three methods were compared in terms of the Concordance index (C-index), Integrated Brier Score (IBS), and Calibration slope. In addition, we find that these methods have different performances when the effects are linear or nonlinear under various censoring rates.

Serum Bicarbonate Deficiency in Dogs with Acute and Chronic Kidney Disease

Serum bicarbonate deficiency is a disorder frequently found in human patients with acute (AKI) and chronic (CKD) kidney disease, due to abnormalities in kidney generation and reabsorption of bicarbonate. Although alkali supplementation is usually performed in both humans and veterinary CKD patients, data regarding the frequency of bicarbonate disorders in AKI and CKD dogs are scarce. The aim of the present study is to assess the frequency and the severity of bicarbonate deficiency of dogs affected by AKI, acute chronic kidney disease (ACKD), and CKD, and to investigate its possible association with the IRIS grade/stage as well as with disorders of calcium phosphate metabolism. A retrospective evaluation of the serum biochemical panels of all dogs with diagnoses of AKI, ACKD, and CKD referred to the nephrology and urology service of the Veterinary Teaching Hospital of the University of Pisa, between January 2014 and January 2022, was performed. Bicarbonate deficiency was defined as serum bicarbonate < 22 mmol/L and classified as moderate (between 18 and 22 mmol/L) or severe (<18 mmol/L). Serum bicarbonate deficiency was found in 397/521 dogs (76%), of which 142/397 (36%) showed moderate deficiency, and 255/397 (64%) severe deficiency. Dogs with AKI and ACKD showed a significantly higher frequency of bicarbonate deficiency (p = 0.004) and severe forms compared to CKD dogs (p = 0.02). In AKI and ACKD dogs, a negative linear correlation was found between serum bicarbonate and serum creatinine, urea, and phosphate. The frequency of bicarbonate deficiency was higher in the later stages of the disease in both AKI (p = 0.01), ACKD (p = 0.0003), and CKD dogs (p = 0.009). Dogs with serum CaxP ≥ 70 mg²/dL² showed a higher frequency of bicarbonate deficiency (p = 0.01) and showed severe forms (p = 0.01) compared to dogs with CaxP < 70 mg²/dL². Serum bicarbonate deficiency seems to be a very frequent disorder in both AKI, ACKD, and CKD dogs, with an increasing frequency and severity in more advanced stages of kidney disease. The higher frequency and severity of bicarbonate deficiency in AKI and ACKD may be caused by a more severe and sudden loss of kidney function, or extra-renal factors. Finally, the association between frequency and severity of bicarbonate deficiency and abnormal CaxP may suggest a potential connection between metabolic acidosis and bone mineral disorders.

The association between albumin corrected anion gap and ICU mortality in acute kidney injury patients requiring continuous renal replacement therapy

The relationship between albumin corrected anion gap (ACAG) and mortality in acute kidney injury (AKI) patients who received continuous renal replacement therapy (CRRT) has not been investigated in any previous studies. This study aimed to investigate the relationship between ACAG at CRRT initiation and all-cause mortality among these patients in the intensive care unit (ICU). Patients diagnosed with AKI and treated with CRRT in the ICU from the Medical Information Mart for Intensive Care-IV version 1.0 (MIMIC IV) database and Huzhou Central Hospital were retrospectively enrolled. Participants were divided into two groups: the normal ACAG group (12-20 mmol/L) and high ACAG group (> 20 mmol/L). The Kaplan-Meier method and log-rank test were used to compare the survival rate between the two groups. Restricted cubic spine (RCS) and Cox proportional-hazards models were utilized to analyze the relationship between ACAG at CRRT initiation and ICU all-cause mortality of these patients. A total of 708 patients met the inclusion criteria in the study. The all-cause mortality of these patients during ICU hospitalization was 41.95%. Patients in the high ACAG group exhibited significantly higher ICU all-cause mortality rate than patients in the normal ACAG group (all P < 0.001). The Kaplan-Meier survival curves showed that the normal ACAG group had a higher ICU cumulative survival rate than the high ACAG group (log-rank test, χ₁²= 13.620, χ₂² = 12.460, both P < 0.001). In the multivariate COX regression analyses, patients with higher ACAG (> 20 mmol/L) levels at the time of CRRT initiation in the MIMIC IV database and Huzhou Central Hospital were significantly correlated with ICU all-cause mortality after adjusting multiple potential confounding factors with hazard ratios of 2.852 (95% CI 1.718-4.734) and 2.637(95% CI 1.584-4.389), respectively. In critically AKI patients who undergo CRRT, higher ACAG (> 20 mmol/L) level at the initiation of CRRT was significantly correlated with ICU all-cause mortality. Therefore, clinicians should pay more attention to those patients with a higher ACAG value.

Urinary Sulfate, Kidney Failure, and Death in CKD: The African American Study of Kidney Disease and Hypertension

Background

Sulfur is an important mineral element whose principal source is animal protein. Animal protein contributes to the daily acid load, which is associated with poor outcomes in individuals with chronic kidney disease (CKD). We hypothesized that higher urinary sulfate, as a reflection of the daily acid load, is associated with a greater risk of death and CKD progression.

Methods

Urinary sulfate was measured in 1057 African American Study of Kidney Disease and Hypertension (AASK) participants at baseline. Participants were categorized by tertiles of daily sulfate excretion. The longitudinal outcome of interest was the composite of death, dialysis, or 50% reduction in measured glomerular filtration rate (GFR). Multivariable adjusted Cox regression models were fit to relate the composite outcome to daily sulfate excretion using the lowest tertile as the reference.

Results

Participants in the highest urinary sulfate tertile were more likely to be men and have a higher body mass index, protein intake, measured GFR, and urinary ammonium and phosphate excretion, and lower urinary protein/creatinine. Compared with those in the lowest tertile of sulfate, those in the highest tertile had a 44% lower hazard (95% CI, 0.37 to 0.84), and those in the middle tertile had a 27% lower hazard (95% CI, 0.55 to 0.96) of death, dialysis, or 50% reduction in measured GFR during follow-up after adjusting for demographics, GFR, protein intake, and other potential confounders. Protein intake was not associated with risk of these events.

Conclusions

Higher urinary sulfate excretion is associated with more favorable outcomes in Blacks who have CKD attributed to hypertension.

Trajectory of Estimated Glomerular Filtration Rate and Malnourishment Predict Mortality and Kidney Failure in Older Adults With Chronic Kidney Disease

Objective: The trajectory patterns of estimated glomerular filtration rates (eGFR) in chronic kidney disease (CKD) older adults with malnourishment and their association with subsequent patient outcomes have not been elucidated. We aimed to assess the eGFR trajectory patterns for predicting patient survival and kidney failure in the elderly without or with malnourishment.

Materials and Methods: Based on a prospective longitudinal cohort, CKD patients aged 65 years or older were enrolled from 2001 to 2013. Among the 3,948 patients whose eGFR trajectory patterns were analyzed, 1,872 patients were stratified by the absence or presence of malnourishment, and 765 patients were identified and categorized as having malnourishment. Four eGFR trajectory patterns [gradual decline (T0), early non-decline and then persistent decline (T1), persistent increase (T2), and low baseline and then progressive increase (T3)] were classified by utilizing a linear mixed-effect model with a quadratic term in time. The malnourishment was defined as body mass index < 22 kg/m², serum albumin < 3.0 mg/dL, or Geriatric Nutritional Risk Index (GNRI) < 98. This study assessed the effectiveness of eGFR trajectory patterns in a median follow-up of 2.27 years for predicting all-cause mortality and kidney failure.

Results: The mean age was 76.9 ± 6.7 years, and a total of 82 (10.7%) patients with malnourishment and 57 (5.1%) patients without malnourishment died at the end of the study. Compared with the reference trajectory T0, the overall mortality of T1 was markedly reduced [adjusted hazard ratio (aHR) = 0.52, 95% confidence interval (CI) 0.32–0.83]. In patients with trajectory, T3 was associated with a high risk for kidney failure (aHR = 5.68, 95% CI 3.12–10.4) compared with the reference, especially higher risk in the presence of malnourishment. Patients with high GNRI values were significantly associated with a lower risk of death and kidney failure, but patients with malnourishment and concomitant alcohol consumption had a higher risk of kidney failure.

Conclusions: Low baseline eGFR and progressively increasing eGFR trajectory were high risks for kidney failure in CKD patients. These findings may be attributed to multimorbidity, malnourishment, and decompensation of renal function.

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.