An unsuspected cause for metabolic acidosis in chronic renal failure: sorbent system hemodialysis.

A severe metabolic acidosis was produced in a patient with chronic renal failure by hemodialysis using a sorbent system to regenerate bicarbonate dialysate with an initial bicarbonate concentration of 60 mEq/L. The acidosis resolved with standard single-pass hemodialysis. In five additional patients, the bicarbonate concentration of the dialysate with the sorbent system was noted to be low and quite variable (mean +/- SD, 16.5 +/- 8.3 mEq/L, range 5 mEq/L to 39 mEq/L). The low dialysate bicarbonate failed to correct metabolic acidosis and, in fact, was capable of further lowering the serum bicarbonate. The capacity of the regenerating cartridge to release protons makes this form of dialysis a potential cause for metabolic acidosis. The safety of the sorbent system dialysis, at least in the bicarbonate mode, requires further evaluation.