Phosphate kinetics in acetate-free biofiltration.

The phosphate kinetics during bicarbonate dialysis (BCD) and Acetate-free Biofiltration (AFB) were determined in 3 stable regular dialysis patients. These patients were switched to a 6-month period of AFB after a 12-month period of BCD. The plasma levels of phosphate, urea, and bicarbonate, and mass removal of phosphate and urea were measured every hour, during 3 consecutive dialysis sessions on BCD and AFB. The plasma phosphate behavior revealed a peculiar form with two main components, which differed from that of urea. The plasma phosphate level fell sharply during the first 2 hours of treatment, and then remained at a plateau towards to the end of the session. The plasma bicarbonate levels during the treatment sessions in the case of AFB were significantly higher than that in BCD. The actual mass removal in AFB was similar to that BCD, despite a significantly lower value of pre-plasma phosphate. A high ultrafiltration rate and better control of acidosis might be the reason for the better performance of phosphate mass removal in AFB. Better control of phosphatemia due to AFB can lead to a reduction in the amount of phosphate binders which have several untoward side effects.