Varying Dialysate Bicarbonate Concentrations in Maintenance Hemodialysis Patients Affect Post-dialysis Alkalosis but not Pre-dialysis Acidosis

This study aimed to assess the effects of different dialysate bicarbonate concentrations in correcting acid-base imbalance in 53 stable hemodialysis patients in a university-hemodialysis unit. Three different bicarbonate concentrations were assigned, i.e. 25 mEq/L in 10, 30 mEq/L in 30, and 35 mEq/L in 13 patients. Blood gas analyses from arterial line blood samples before and after dialysis in the mid-week were performed for the determination of pH and serum bicarbonate (HCO(3)(-)) concentration. The mean values of predialysis arterial HCO(3)(-) were mildly acidotic in all 3 groups, but not significantly different among them, whereas those of post-dialysis arterial HCO(3)(-) were alkalotic, especially in the group of 35 mEq/L as compared with the other two groups. The mean blood pH was not significantly different among the 3 groups. As expected, there was a positive correlation between pre-dialysis pH and post-dialysis pH (r=0.45, p=0.001), and pre-dialysis HCO(3)(-) and post-dialysis HCO(3)(-) (r=0.58, p=0.000), but with a negative correlation between pre-dialysis HCO(3)(-) and the increment of intradialytic HCO(3)(-) following hemodialysis (r=-0.46, p=0.001). In conclusion, this study shows that the impact of conventional dialysate bicarbonate concentrations ranging from 25 to 35 mEq/L is not quite different on the mild degree of predialysis acidemia, but the degree of postdialysis alkalemia is more prominent in higher bicarbonate concentrations. Base supply by hemodialysis alone does not seem to be the main factor to determine the predialysis acidosis in end-stage renal disease patients on chronic maintenance hemodialysis.