Nephrol Dial Transplant (2003) 18: 559-562
© 2003 European Renal Association-European Dialysis and Transplant Association
Assessment of haemodialysis adequacy by ionic dialysance: intra-patient variability of delivered treatment
Department of Renal Medicine, Derby City General Hospital, Derby, UK
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
Correspondence and offprint requests to: Dr C. W. McIntyre, Department of Renal Medicine, Derby City General Hospital, Uttoxeter Road, Derby, DE22 3NE, UK. Email: chris-mcintyre{at}lineone.net
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