Non-invasive monitoring of effective dialysis dose delivered to the haemodialysis patient

Assessment of normalized dialysis dose Kt/V actually deliveredto the patient carries the drawback of requiring several bloodor dialysate samplings and urea concentration measurements.In order to easily quantify Kt/V, we validate here the routineimplementation of an original technique for the non-invasive,on-line, and fully automatic estimation of total mean urea clearance.This estimation is obtained from the measurement by a conductivitymethod of the effective ionic dialysance D_R, which is the dialysanceof electrolytes taking into account ultrafiltration and recirculation. The observed increase in D_R with ultrafiltration rate and decreasein D_R with elevation of access recirculation ratio show thatthe estimation of D_R is affected by ultrafiltration and recirculationin a consistant manner. The mean value K_eff of ionic dialysanceD_R was compared with the value K_dc of effective urea clearanceobtained by dialysate collection during 12 haemodialysis sessions.The similarity (magnitude of variation 5%) between the ionicdialysance K_eff and the effective urea clearance K_dc supportsthe validity of the equivalence between the transfer characteristicsof electrolytes and urea through the dialyser membrane. Givenan estimate of the urea distribution volume V, this estimationof effective urea clearance by ionic dialysance measurementallows an on-line estimation of the normalized dialysis doseKt/V actually delivered to the patient.