Utilization of bicarbonate for base repletion in hemodialysis

Because of physiochemical considerations, acetate rather than bicarbonate has traditionally been used as the base repletion agent in dialysate. There are major differences in the mechanisms through which these agents neutralize the body's acid load in the circumstance of dialysis. Acetate dialysis relies on metabolism of acetate to generate bicarbonate. Loss of bicarbonate into the dialysate requires that acetate dialysis supply base far in excess of that required to buffer metabolic hydrogen ion generation alone. Consequently, net accrual of base is difficult to quantitate and may be inadequate to neutralize the excess hydrogen ion, leading to chronic buffer depletion. However, acute acid-base problems are usually avoided because of the indirect nature of base addition. In contrast, net base accrual with bicarbonate dialysis occurs in a direct and quantitative manner. While inadequate base repletion is avoided, the direct addition of base requires much tighter control if undesirable acute changes in blood pH are to be avoided.