On-line dialyser clearance using conductivity.

A method allowing non-invasive measurement of dialyser clearance in vivo is described. Electrolyte concentration difference is measured by two conductivity sensors positioned up- and downstream of the dialyser in the dialysate path. From the conductivity differences measured at two different dialysate input concentrations and dialysate flow, electrolyte dialysance is calculated. The method takes recirculation effects into account and measures effective clearance rather than dialyser clearance. Test results comparing on-line electrolyte clearance with blood side clearance corrected for recirculation are consistent with this calculation. From clearance measured several times during dialysis and time on dialysis, K.t can be calculated with an estimated accuracy of +/- 10%. This method can be used to control the efficacy of each individual treatment. The K.t goal can be derived from monthly two-pool kinetic modelling.