Equivalent continuous clearances EKR and stdK in incremental haemodialysis.

BACKGROUND Many haemodialysis patients have residual renal function (RRF), which as such is insufficient to maintain satisfactory quality of life but reduces the demands of treatment and improves outcomes. In incremental dialysis, the dose is adjusted according to RRF, but how should it be done? METHODS Urea generation rate (G) and distribution volume (V) were determined by the double-pool urea kinetic model in 225 haemodialysis sessions of 30 patients. The effect of different degrees of RRF on equivalent renal urea clearance (EKR), standard urea clearance (stdK) and urea concentrations and required treatment times to achieve the HEMO study standard dose equivalent EKR and stdK targets were studied by computer simulations. RESULTS Ignoring RRF leads to underestimation of EKR, stdK, urea generation rate and protein equivalent of nitrogen appearance. Both EKR and stdK increase linearly with renal urea clearance (Kr). The HEMO standard dose equivalent EKRc is 13.8 mL/min/40 L and stdK/V 2.29 /wk (9.1 mL/min/40 L). The required treatment time to achieve the HEMO-equivalent targets has an almost linear inverse relationship to Kr. If the HEMO standard dose equivalent EKR or stdK is used as the target, RRF may replace several hours of weekly dialysis treatment time. stdK appreciates RRF more than EKR. CONCLUSIONS RRF is included in the original EKR and stdK concepts. EKR and stdK--determined by kinetic modelling--are promising measures of adequacy in incremental dialysis.