Background:The appropriate hemodialysis dialysate bicarbonate concentration isn't clear. The recommended pre-hemodialysis blood bicarbonate level of >22mEq/L is frequently not achieved on the commonly used dialysate bicarbonate concentration of 33-35mEq/L. Higher dialysate bicarbonate concentration may correct acidosis and improve bone, muscle & nutritional state. However, it may also induce intra-dialytic metabolic alkalosis/alkalemia and/or increase bicarbonate buffering and CO2 production inducing hypercapnia in patients with disturbed ventilation. Recently Higher dialysate bicarbonate concentration has been demonstrated to be associated with increased mortality.Objectives: To evaluate the effects of high dialysate bicarbonate concentration on correction of acidosis in patients who were acidotic on low dialysate bicarbonate concentration, and on development of intradialytic metabolic alkalosis/alkalemia and/ or hypercapnia.
Methods:In a prospective bi-center study, nineteen chronic hemodialysis patients were evaluated on consecutive three-week period on low dialysate bicarbonate concentration (33-34mEq/L) and afterwards high dialysate bicarbonate concentration (40mEq/L). Arterial blood gases and electrolytes were assessed once weekly at start, middle and end of first weekly hemodialysis.Results: On low dialysate bicarbonate concentration pre-hemodialysis blood bicarbonate level was 21.8+3.3 and <22mEq/L in 11 patients. High dialysate bicarbonate concentration in these patients raised pre-hemodialysis blood bicarbonate level to 26.6+5mEq/L but induced intradialytic metabolic alkalosis/alkalemia similarly to the non-acidotic patients (post-hemodialysis: blood bicarbonate level 35.3+1.7mEq/L vs 37+2.1mEq/L, pH 7.52+0.04 vs 7.51+0.04, respectively). There were no significant hypercapnic episodes.
Conclusion:high dialysate bicarbonate concentration corrected the significant and common metabolic acidosis on low dialysate bicarbonate concentration but induced asymptomatic intra-dialytic metabolic alkalosis/alkalemia.