Evaluation of hemodialysis adequacy using online Kt/V and single-pool variable-volume urea Kt/V

Objective The hemodialysis (HD) team should deliver single-pool variable-volume (SPVV) urea Kt/V >= 1.2. At present dialysis machines provide online assessment of Kt/V. The aim of our study is to assess if online Kt/V and SPVV urea Kt/V yield similar values and if it may be replaced in evaluation of HD adequacy. Patients and methods Studies were carried out two times (evaluation I and evaluation II) in 40 patients dialyzed using machines with online Kt/V monitoring by the conductivity method. During the middle HD session in the week, SPVV Kt/V was estimated from urea measurements in serum at the beginning and at the end of the HD session using the second generation formula of Daugirdas. Values of SPVV urea Kt/V and simultaneously obtained online Kt/V were compared. Results In I, SPVV Kt/V was 1.37 +/- 0.16, and online Kt/V was 1.16 +/- 0.14 (P = 0.000), r = 0.559 (P = 0.000); a regression equation indicated SPVV Kt/V as 0.62457 + 0.64048 * online Kt/V. In II, estimated SPVV Kt/V was 1.37 +/- 0.20, online Kt/V-1.16 +/- 0.15 (P = 0.000), r = 0.493 (P = 0.001), and calculated SPVV Kt/V was 1.37 +/- 0.10. In I, SPVV urea Kt/V > 1.20 was shown in 87.5% of patients, whereas online Kt/V > 1.20 was observed in 37.5% of cases (P = 0.000). In II, respective values were 82.5% and 40.0% of patients (P = 0.000). Conclusions SPVV urea Kt/V indicates a more adequate HD session than online Kt/V. This difference has to be considered when applying Kt/V to clinical practice.