Influence of the ionic dialysance monitor on Kt measurement in hemodialysis.

BACKGROUND: Ionic dialysance can provide accurate monitoring of dialysis dose during each hemodialysis session. Increasingly, hemodialysis machines incorporate devices that measure ionic dialysance, allowing the dialysis dose to be determined noninvasively in real time and in each session. Because Kt product was proposed as a measure of hemodialysis dose to avoid the reverse J-shaped curve between urea reduction ratio or Kt/V and mortality, we investigated whether ionic dialysance values and Kt measurements are affected by different ionic dialysance monitors (Diascan and online clearance monitoring [OCM]) and dialysis machines.

STUDY DESIGN: Four-period crossover.

SETTING & PARTICIPANTS: 31 adult long-term hemodialysis patients using 2 different ionic dialysance monitors in 4 dialysis machines: Diascan in Hospal Integra and Gambro AK-200 machines and OCM in Fresenius 4008S and 5008 machines.

PREDICTORS: Ionic dialysance monitor and machine used in 4 hemodialysis sessions for each participant.

OUTCOMES: Kt and Kt/V measured by using ionic dialysance and serum urea nitrogen.

RESULTS: Mean values for initial and final ionic dialysance were similar for Integra and AK-200 machines, both measured by using Diascan, and for the 4008S and 5008 machines, both measured by using OCM; however, OCM values tended to be greater in the 4008S and 5008 machines. Kt measured in the 4008S and 5008 machines was greater (59.6 +/- 12 and 58.6 +/- 11 L, respectively) than with the Integra and AK-200 machines (53.4 +/- 11 and 53.8 +/- 11 L). Mean urea reduction ratio and Kt/V were 78.0% +/- 8% and 1.89 +/- 0.43 for Diascan monitors and 79.6% +/- 8% and 1.99 +/- 0.44 for OCM monitors, respectively (P < 0.01). Differences between monitors in Kt determination were caused in part by a real difference in dialysis effectiveness (6%) and in part by an intermethod difference (4%). Kt adjusted by Kt/V differences was recalculated, and because of good correlation between Diascan and OCM, we were able to apply a formula (Kt(OCM) = 1.08 Kt(Diascan) - 2; r =0.95) that allowed both Kt quantification methods to be compared.

LIMITATIONS: Nonblinded nonrandomized small sample.

CONCLUSIONS: Kt is a valid method for judging dialysis dose in real time by using ionic dialysance measurements. Adjustments to correct intermethod differences may be necessary to ensure generalizability among ionic dialysance monitors.