Kt/V measurement based on ionic dialysance by Fresenius On-line Clearence Monitor (OCM)

Abstract

It is known that the ionic dialysance is equivalent to the blood water urea clearance. Thus, on-line Kt/V measurement can be a useful tool for verification of dialysis dose adequacy. The aim of this study was to verify the accuracy of the On-line Clearance Monitor device (OCM) with different dialysis membranes and its convenience in routine clinical work. Methods. 8 stable dialysis patients (4 M, 4 F, mean age 38 ± 2,2 years) were evaluated during 64 dialysis sessions with different membranes (Polysulfone Fresenius, Althane, Polysulfone Bellco, regenerated cellulose). OCM was incorporated into Fresenius 4008S dialysis machine. This device periodically varied inlet dialysate conductivity (CD) up and down by up to 17,5% from the setting value. The phase of change of CD lasts for a maximum of 60 sec. The CD variation was then followed by a phase of constant CD, and CD was measured at the dialysate inlet and outlet side. The total duration of the ionic dialysance measurement was approximately 11 min. After the measurement, the value of Kt/V is displayed. Blood urea samples were collected before and after each dialysis session (according to NKF-DOQI recommendation). Kt/V was calculated using the formula: Kt/V = -ln (R - 0,03) + (4 - 3,5 × R) × UF/W (Kt/V [Ur]). Results. Kt/V [Ur] was somewhat higher than Kt/V [OCM] in all cases, except for dialysis sessions with high ultrafiltration volume (9% of dry weight, N = 4). Mean Kt/V [OCM] was 1,195 ± 0,04; mean Kt/V [Ur] was 1,271 ± 0,04. The difference was not significant. There was high and significant correlation between these values (r = 0,96, р < 0,001). Kt/V determination was independent of dialyzer’s type. We can conclude that Fresenius OCM is a reliable, simple and inexpensive non-invasive tool for optimization of the dialysis program in usual clinical practice.