The role of oral sodium bicarbonate supplementation in maintaining acid-base balance and its influence on the cardiovascular system in chronic hemodialysis patients - results of a prospective study.

Background: Major acid-base variations during dialysis and the imbalances in serum calcium levels intensified by them play a role in cardiovascular damage of hemodialysis patients. Early vascular walls modifications can be objectified by determining the pulse wave velocity (PWV) - a marker of vascular stiffness that is associated with increased risk of cardiovascular events. Material and methods: This was a prospective study conducted on 63 chronic hemodialysis patients with diuresis above 500 mL/ 24 hours and predialysis blood pressure below 160 mmHg (treatment controlled) randomized in two groups for 12 months - the study group receiving interdialitic oral sodium bicarbonate doses and control group, without oral sodium bicarbonate supplementation, but receiving higher bicarbonate prescriptions in dialysis. All the patients were monthly evaluated by biochemical tests (serum calcium, phosphate, iPTH, bicarbonate), the assessment of prescribed doses of phosphate binders being undergone. Two PWV determinations and chest X-ray exams for coronary calcifications were done - at the beginning and end of the study for every patient. Results: In the study group (n = 29), the mean age was 56.48 ± 12.78 years and the average duration of dialysis was 55.51 ± 34.53 months, the mean dialysis bicarbonate was 29.81 ± 1.41 mEq/ L and 27 of them (subgroup 0) had alkaline reserve (AR) 20-22 mEq/ L. The control group (n = 34) had a mean age of 57.35 ± 15.32 years and the mean dialysis duration 59.67 ± 34.79 months, with an average level of dialysis bicarbonate of 33 ± 2.2 mEq/ L necessary to maintain AR within guidelines. Depending on the mean AR obtained, this group was divided into three subgroups (subgroup 1, subgroup 2, and subgroup 3). There were statistically significant differences regarding the necessary of dialysis bicarbonate (p < 0.001), average serum calcium levels (p < 0.001) and serum phosphorus (p < 0.001), as well as PWV mean values and the number of vascular calcifications (p = 0.036) between the study and the control group. The average dose of phosphate binders was significantly higher in the study group (p = 0.01). At the end of the study, the serum iPTH average levels were decreased in the study group (p < 0.001) and significantly increased in the control group (p < 0.001). Conclusions: Avoiding large variations in serum bicarbonate levels is an important step in hemodialysis patients' management because wide acidosis-alkalosis variation can increase cardiovascular risks in terms of altering the vessel walls elasticity and favoring their calcifications. Abbreviations: GFR = glomerular filtration rate,PWV = pulse wave velocity, iPTH = intact parathyroid hormone,AR = alkaline reserve, BP = blood pressure,mEq = milliequivalents,L = liter.