Automatic, noninvasive intradialytic clearance measurement.

The feasibility of non invasive, automatic intradialytic measurement of effective clearance is demonstrated by a mathematical derivation. In a practical setting the conductivity difference between dialysate inlet and outlet of the dialyzer is measured for two different dialysate inlet concentrations. This allows for the calculation of the electrolyte dialysance, which is equal to the effective urea clearance, provided dialysate flow, blood flow and blood electrolyte composition remain unchanged during the measuring interval.