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. Kidney International (2010) 78, 920-925; doi:10.1038/ki.2010.216; published online 14 July 2010