Real-time Kt/V determination by ultraviolet absorbance in spent dialysate: technique validation

Real-time determination of Kt/V can be provided by monitoring ultraviolet absorbance of solutes in spent dialysate. This not only overcomes dependency on error-prone pre- and post-dialysis blood sampling; it circumvents inaccuracies associated with estimating the urea distribution volume and its high measurement frequency tightly reflects the course of the dialysis. Our study compared the ultraviolet-based spKt/V and eKt/V with the commonly used blood-based counterparts. A first study of 16 patients compared ultraviolet Kt/Vs against blood Kt/Vs obtained by using the 'gold standard' of serial blood samples. A second study included 18 patients and compared the ultraviolet and blood values under routine conditions. Both studies showed mean blood-based spKt/V and eKt/V values statistically indistinguishable from their ultraviolet-based counterparts. Hence, on-line monitoring of ultraviolet absorption of spent dialysate is applicable in routine hemodialysis allowing continuous measure of removed solutes from spent dialysate without disturbing the patient or treatment session.