ONLINE HEMODIAFILTRATION WITH PREDILUTION AND POSTDILUTION - IMPACT ON THE ACID-BASE STATUS

With on-line formation of the substitution fluid, high substitution ra tes in predilution (PRD) and postdilution (POD) can be obtained (Frese nius 4008 On-Line HDF; Gambro AK 100 Ultra). The substitution fluid is branched off from the dialysate produced by the dialysate delivery sy stem of the HDF machine. Under these conditions if is desirable to con sider the effect of the different treatment modes on the acid-base sta tus. Using Fresenius 4008 On-Line HDF machines, ESRD-patients were tre ated alternately with high-flux hemodialysis (HD), postdilution HDF (P OD-HDF) and predilution HDF (PRD-HDF), while all other treatment param eters were kept constant, in particular the bicarbonate dialysate conc entration. Plasma-HCO3, - pH and -pCO(2) were measured and compared wi th the results of a multicompartment bicarbonate model developed by Th ews. Also plasma-pO(2) and K+ were measured. The results showed no sig nificant differences between HD POD- and PRD-HDF: Acidosis was correct ed effectively and no excessive compensation of the acid-base disturba nce was observed.