Estimation of delivered dialysis dose by on-line monitoring of the ultraviolet absorbance in the spent dialysate.
BACKGROUND
Several methods are available to determine Kt/V, from predialysis and postdialysis blood samples to using on-line dialysate urea monitors or to ionic dialysance using a conductivity method. The aim of this study is to compare Kt/V calculated from the slope of the logarithmic on-line ultraviolet (UV) absorbance measurements, blood urea Kt/V, dialysate urea Kt/V, and Kt/V from the Urea Monitor 1000 (UM; Baxter Healthcare Corp, Deerfield, IL).


METHODS
Thirteen uremic patients on chronic thrice-weekly hemodialysis therapy were included in the study. The method uses absorption of UV radiation by means of a spectrophotometric set-up. Measurements were performed on-line with the spectrophotometer connected to the fluid outlet of the dialysis machine; all spent dialysate passed through a specially designed cuvette for optical single-wavelength measurements. UV absorbance measurements were compared with those calculated using blood urea and dialysate urea, and, in a subset of treatments, the UM.


RESULTS
Equilibrated Kt/V (eKt/V) obtained with UV absorbance (eKt/Va) was 1.19 +/- 0.23; blood urea (eKt/Vb), 1.30 +/- 0.20, and dialysate urea (eKt/Vd), 1.26 +/- 0.21, and Kt/V in a subset measured by the UM (UM Kt/V) was 1.24 +/- 0.18. The difference between eKt/Vb and eKt/Va was 0.10 +/- 0.11, showing a variation similar to the difference between eKt/Vb and eKt/Vd (0.03 +/- 0.10) and in a subset between eKt/Vb and UM Kt/V (-0.02 +/- 0.11).


CONCLUSIONS
The study suggests that urea Kt/V can be estimated by on-line measurement of UV absorption in the spent dialysate.
Department of Nephrology University Hospital, Linköping, Sweden. fredrik.uhlin@lio.se
Fredrik
F
Uhlin
Ivo
I
Fridolin
Lars-Göran
LG
Lindberg
Martin
M
Magnusson
D000042:Absorption; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D015312:Hemodialysis Solutions / Q000008:administration & dosage* / Q000493:pharmacokinetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods; D006435:Renal Dialysis; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays; D014508:Urea / Q000097:blood*; D014511:Uremia / Q000378:metabolism / Q000628:therapy
D015312:Hemodialysis Solutions; D014508:Urea