NDT Advance Access originally published online on April 12, 2006
Nephrology Dialysis Transplantation 2006 21(8):2225-2231; doi:10.1093/ndt/gfl147
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
© The Author [2006]. Published by Oxford University Press on behalf of ERA-EDTA. All rights reserved. For Permissions, please email: journals.permissions@oxfordjournals.org
Original Articles: Dialysis and Transplantation
Dialysis dose (Kt/V) and clearance variation sensitivity using measurement of ultraviolet-absorbance (on-line), blood urea, dialysate urea and ionic dialysance
1 Department of Nephrology, University Hospital, Linköping, S-581 85 Linköping, Sweden, 2 Centre of Biomedical Engineering, Tallinn Technical University, EST-19086 Tallinn, Estonia and 3 Department of Biomedical Engineering, Linköping University, University Hospital, S-581 85 Linköping, Sweden
Correspondence and offprint requests to: F. Uhlin, Department of Nephrology University Hospital, Linköping, S-581 85 Linköping, Sweden. Email: Fredrik.Uhlin{at}lio.se
Background. An on-line monitoring system for dialysis dose calculations could make it possible to provide an adequate dialysis dose that is consistently given to haemodialysis (HD) patients. The aim of this study was to compare dialysis dose (Kt/V) using four different methods and their sensitiveness to a reduction in clearance.
Methods. Six patients were monitored on-line with ultraviolet (UV)-absorbance at a wavelength of 297 nm in three consecutive dialysis sessions during 1 week. During the last treatment, the clearance was reduced by 
25% by decreasing the blood flow. For the determination of UV-absorbance, a spectrophotometer was connected to the fluid outlet of the dialysis machine with all spent dialysate passing through a flow cuvette. The equilibrated Kt/V (eKt/V) estimated by UV-absorbance was compared with eKt/V from the ionic dialysance method using the on-line clearance monitor (OCM) and the appurtenant software dose-calculation tool DCTool (Fresenius Medical Care, Germany), eKt/V calculated from the dialysate-urea slope and with eKt/V from pre- and post-dialysis blood-urea samples as reference.
Results. The study demonstrates that the sensitiveness to clearance reduction is similar in the four methods compared for eKt/V. When the different methods were compared, the mean eKt/V of UV-absorbance was 1.21 ± 0.20, blood 1.30 ± 0.21, dialysate 1.32 ± 0.21 and OCM (using the DCTool) 1.31 ± 0.21. The standard deviation was of the same magnitude.
Conclusion. The UV-method gives a similar response to clearance reduction compared with the other methods when comparing dialysis dose. The high sampling rate by continuous monitoring of UV-absorbance allows evaluation of the clearance process during dialysis and gives immediate feedback to on-line adjustments.
Keywords: clearance; haemodialysis monitoring; ionic dialysance; Kt/V; ultra violet absorption; urea