Removal of phosphate (Pi) by either bicarbonate dialysis or biofiltration in uremics.

The kinetics of extra and intracellular red blood cell (RBC) Pi and its removal by different therapeutic modalities were evaluated in 30 uremic patients over a 6 mo. period. Acetate hemodialysis alone, combined with hemoperfusion, or associated once a week with plasma-perfusion sessions using an activated bauxite cartridge, bicarbonate dialysis either in single pass or in recirculating system (40 L) and biofiltration, were the depurative treatments employed. The treatments with acetate buffer showed a temporary intracellular shift of Pi at the end of the sessions with post-dialytic plasma Pi rebound. This was not evident with bicarbonate buffer and biofiltration where acidosis was corrected better, and similarly during plasma perfusion treatment because blood pH remained unchanged. These findings may explain the better plasma Pi level at the end of our study with these later therapeutic models compared to acetate dialysis alone or combined with hemoperfusion. In these conditions Pi removal is limited by the correction of acidosis which implies acetate metabolism with ATP activation leading to a transient Pi intracellular influx and a subsequent efflux into the extracellular compartment.