Optimal dialysate bicarbonate during hemodialysis.

Eleven stable hemodialysis patients were treated with acetate dialysate, then changed to bicarbonate dialysate at three different concentrations. Blood was drawn from the arterial limb of the arteriovenous fistula before and after dialysis for pH, partial pressure of carbon dioxide, bicarbonate radical, and partial pressure of oxygen. Both acetate (35 mEq/L) and the lowest bicarbonate concentration (25 mEq/L) resulted in inadequate control of acid-base balance. Using a bicarbonate concentration of 30 mEq/L, mild predialysis acidosis was still present; this could be abolished using 35 mEq/L, but only at the cost of postdialysis alkalosis and mild hypoxemia.