Assessment of haemodialysis adequacy by ionic dialysance: intra-patient variability of delivered treatment.
BACKGROUND
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, Q(B) and modality were fully delivered in all treatments analysed (97% of total). Kt/V measured by ionic dialysance (Kt/V(ID)) correlated highly with that derived from measurement of urea reduction (R(2)=0.92, P<0.0001). Kt/V(ID) underestimated urea-based Kt/V by a mean of only 1.5% (95% CI 0.18-2.9%). Kt/V(ID) varied greatly within individual patients with a mean CV of 0.13+/-0.10 (95% CI 0.05-0.3). If a Kt/V(ID) 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.


CONCLUSIONS
In conclusion, Kt/V(ID) 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.
McIntyre
Christopher W
CW
Department of Renal Medicine, Derby City General Hospital, Derby, UK. chris-mcintyre@lineone.net
Lambie
Stewart H
SH
Taal
Maarten W
MW
Fluck
Richard J
RJ
D000328:Adult; D000368:Aged; D004553:Electric Conductivity; D005260:Female; D015312:Hemodialysis Solutions / Q000378:metabolism*; D006801:Humans; D007473:Ion Channels / Q000378:metabolism*; D017736:Ion-Selective Electrodes; D007676:Kidney Failure, Chronic / Q000378:metabolism* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D011446:Prospective Studies; D006435:Renal Dialysis / Q000379:methods*; D015203:Reproducibility of Results; D013813:Therapy, Computer-Assisted / Q000379:methods*
D015312:Hemodialysis Solutions; D007473:Ion Channels