Daily dialysis Kt/V and flexible schedules: is it possible to control efficiency, when and how?

Daily hemodialysis is a promising treatment schedule but uniform criteria for defining efficiency are lacking. On our daily dialysis (DD) schedule, duration is flexible (2-3 hours, patients are free to add up to 30 min/session), Qb 250-350 mL/min; dialyser 1.6-1.8 m2. Study was performed on 12 pts on DD for > or = 2 months, with > or = 4 Kt/V on subsequent days, tested in the same laboratory. To evaluate variability and identify a simple method for weekly calculation, Kt/V was assessed for 133 sessions. On flexible DD, variability of Kt/V-session is high (relative error 4.9%-22%). On flexible schedules, within the time range chosen (2-3 hours) variability of average hourly Kt/V is lower (standard deviation: min (0.014; max (0.052 hour, relative error 4.9%-10%) allowing calculation of weekly Kt/V (averaging 3 sessions: relative error < 6%) suitable for clinical practice. Flexible schedules, allowing patients to increase treatment time, are an interesting clinical option, but a challenge for Kt/V assessment.