Oral Sodium Bicarbonate Supplementation Does Not Affect Serum Calcification Propensity in Patients with Chronic Kidney Disease and Chronic Metabolic Acidosis.

BACKGROUND: Cardiovascular disease is the leading cause of death in patients with chronic kidney disease (CKD) and metabolic acidosis might accelerate vascular calcification. The T50 calcification inhibition test (T50-test) is a global functional test analyzing the overall propensity of calcification in serum, and low T50-time is associated with progressive aortic stiffening and with all-cause mortality in non-dialysis CKD, dialysis, and transplant patients. Low serum bicarbonate is associated with a short T50-time and alkali supplementation could be a simple modifier of calcification propensity. The aim of this study was to investigate the short-term effect of oral sodium bicarbonate supplementation on T50-time in CKD patients. MATERIAL AND METHODS: The SoBic-study is an ongoing randomized-controlled trial in CKD-G3 and G4 patients with chronic metabolic acidosis (serum HCO3- ≤21 mmol/L), in which patients are randomized to either achieve serum HCO3- levels of 24 ± 1 mmol/L (intervention group) or 20 ± 1 mmol/L (rescue group). The effect of bicarbonate treatment on T50-time was assessed. RESULTS: The study cohort consisted of 35 (14 female) patients aged 57 (±15) years, and 18 were randomized to the intervention group. The mean T50-time was 275 (± 64) min. After 4 weeks, the mean change of T50-time was 4 (±69) min in the intervention group and 18 min (±56) in the rescue group (ß = -25; 95% CI: -71 to 22; p = 0.298). Moreover, change of serum bicarbonate in individual patients was not associated with change in T50-time, analyzed by regression analysis. Change of serum phosphate had a significant impact on change of T50-time (ß = -145; 95% CI: -237 to -52). CONCLUSION: Oral sodium bicarbonate supplementation showed no effect on T50-time in acidotic CKD patients.

Effect of Oral Sodium Bicarbonate Treatment on 24-Hour Ambulatory Blood Pressure Measurements in Patients With Chronic Kidney Disease and Metabolic Acidosis.

Background: Sodium bicarbonate supplementation is a mainstay in the treatment of metabolic acidosis in patients with chronic kidney disease (CKD). Recent studies showed reduction of progression of CKD and reduced all-cause mortality. However, additional sodium loading could worsen arterial hypertension, a well-known contributor to progression of CKD. This patient-relevant and economically negative side effect is under-studied in prospective studies up until now. Objective: The aim of this study was to analyze the effect of sodium bicarbonate treatment on arterial blood pressure at baseline and after 8 weeks. Methods: The SoBic study is an ongoing randomized controlled trial, in which patients with CKD receive either a high dose of oral sodium bicarbonate or a rescue treatment, if necessary. We used standardized office blood pressure and 24-hour ambulatory blood pressure monitoring (24h-ABPM). Regression models were adjusted for estimated glomerular filtration rate and change of antihypertensives. Results: 47 subjects were enrolled and the mean age was 57 (±14.6) years and 18 (38%) were female. In 43 randomized subjects with sufficiently performed 24h-ABPM neither systolic 24h-ABPM (2.522; 95%CI: -2.364, 7.408; mmHg) nor diastolic 24h-ABPM (0.868; 95%CI: -2.411, 4.147; mmHg) was affected by study group allocation. When looking at the effect of individual sodium bicarbonate dose on 24h-ABPM, the fully adjusted model suggested an increase of 0.047 (95%CI: -0.026, 0.119) mmHg by each mg/kg per day increase of sodium bicarbonate dose. Conclusion: Sodium bicarbonate supplementation over 8 weeks did not significantly increase blood pressure measured by 24h-ABPM in CKD patients. Trial Registration: EUDRACT Number: 2012-001824-36; 12/07/2012 (https://www.clinicaltrialsregister.eu).

Effect of oral alkali supplementation on progression of chronic kidney disease.

Metabolic acidosis is a frequent but asymptomatic complication in chronic kidney disease (CKD). In early stages of CKD acidosis is limited to the renal tissue and progresses to reduced serum bicarbonate levels. Reduced renal tissue pH and increased ammoniagenesis are the key mechanisms of the kidney to enhance acid excretion to the urine. The expressed protein patterns in the proximal tubular epithelial cells change remarkably, the proximal convoluted tubule develops hypertrophy, and an intra-renal enhanced renin-angiotensin-system leads to interstitial fibrosis. Since nephrons are numerically reduced in CKD each remaining functional unit has to progressively increase these mechanisms to keep up the equilibrium. The adverse effects of chronic metabolic acidosis include aside from acceleration of progression of kidney disease, the development or exacerbation of bone disease, increased degradation of muscle with muscle wasting, enhanced protein degradation and inflammation. Genome wide association studies demonstrated that tubular acid-base transporters are involved in the development of arterial hypertension. Several retrospective analyses have indicated that low serum bicarbonate predicts death in cohorts with CKD and cardiovascular disease. All studies confirmed a U-shaped association of mortality and serum bicarbonate, indicating that both, acidosis and alkalosis are associated with increased mortality. Randomized controlled trials showed that base substitution, either by modification of the diet or by simply adding alkalizing agents, might halt the decline of kidney function in subjects with CKD. In 2012 a meta-analysis concluded that alkali therapy might provide a long-term favorable effect on renal function in patients with CKD.