Introduction. Adequate delivered dose of solute removal (as assessed by urea reduction and calculation of Kt/V) is an important determinant of clinical outcome in chronic haemodialysis (HD) patients. The requirement for multiple blood sampling and efforts taken to minimize the effects of rebound on post‐treatment samples ensure Kt/V is measured only intermittently. On‐line conductivity monitoring (using sodium flux as a surrogate for urea) allows the repeated non‐invasive measurement of Kt/V on each HD treatment. We have studied the accuracy of this method of measuring Kt/V, and the variability of treatment dose delivered to individual patients.
Methods. We prospectively studied 26 established chronic HD patients over 4 weeks (316 treatments). Patients were dialysed using Hospal Integra dialysis monitors, equipped with Diascan® modules to measure Kt/V. Data were downloaded automatically to a central computer server. Urea reduction was measured (once a week) by a two‐pool calculation using 30 min post‐treatment sampling.
Results. Treatment time, QB and modality were fully delivered in all treatments analysed (97% of total). Kt/V measured by ionic dialysance (Kt/VID) correlated highly with that derived from measurement of urea reduction (R2=0.92, P<0.0001). Kt/VID underestimated urea‐based Kt/V by a mean of only 1.5% (95% CI 0.18–2.9%). Kt/VID varied greatly within individual patients with a mean CV of 0.13±0.10 (95% CI 0.05–0.3). If a Kt/VID of 1.0 is considered ‘adequate’, 55% of the patients had variations that would have potentially altered their status as being adequately or inadequately dialysed, as the range of Kt/V readings cross that point during the study period.
Conclusion. In conclusion, Kt/VID seems to be an accurate and readily obtained measure of adequacy. Substantial variation in Kt/V implies repeated measures (ideally for all treatments) are necessary to gain a true picture of the mean treatment dose being delivered to patients.
Keywords: haemodialysis; Kt/V; ionic dialysance
Journal Article. 2389 words. Illustrated.
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