Standard Kt/Vurea: a method of calculation that includes effects of fluid removal and residual kidney clearance

Standard Kt/Vurea (stdKt/V) is a hypothetical continuous clearance in patients treated with intermittent hemodialysis based on the generation rate of urea nitrogen and the average predialysis urea nitrogen. Previous equations to estimate stdKt/V were derived using a fixed-volume model. To determine...

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Bibliographic Details
Published in:Kidney international 2010-04, Vol.77 (7), p.637-644
Main Authors: Daugirdas, John T., Depner, Thomas A., Greene, Tom, Levin, Nathan W., Chertow, Glenn M., Rocco, Michael V.
Format: Article
Language:English
Subjects:
Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy
Biological and medical sciences
Emergency and intensive care: renal failure. Dialysis management
hemodialysis
hemodialysis adequacy
Humans
Intensive care medicine
Kidney - metabolism
Kidney Failure, Chronic - therapy
Medical sciences
Models, Biological
Nephrology. Urinary tract diseases
Ultrafiltration
Urea - metabolism
urea modeling
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Summary:Standard Kt/Vurea (stdKt/V) is a hypothetical continuous clearance in patients treated with intermittent hemodialysis based on the generation rate of urea nitrogen and the average predialysis urea nitrogen. Previous equations to estimate stdKt/V were derived using a fixed-volume model. To determine the impact of fluid removal as well as residual urea clearance on stdKt/V, we modeled 245 hemodialysis sessions (including conventional 3/week, in-center 6/week, and at-home nocturnal 6/week) in 210 patients enrolled in the Frequent Hemodialysis Network Daily and Nocturnal clinical trials. To examine the role of fluid removal, modeled stdKt/V was compared to stdKt/V estimated from a previously published simplified equation. In a subgroup of 45 sessions with residual urea clearance over 1.5 ml/min, the contribution of residual urea clearance to stdKt/V was measured. For all dialysis schedules, the fixed-volume equation predicted stdKt/V well when both fluid removal and residual urea clearance were set to zero. When fluid removal was included, modeled stdKt/V was slightly underestimated for all three modes of hemodialysis. The shortfall correlated directly with weekly fluid removal and inversely with modeled urea volume. Modeled stdKt/V compressed residual urea clearance to about 70% of its measured value and the fractional downsizing significantly correlated inversely with treatment Kt/V. Our new equation predicted modeled stdKt/V with a high level of accuracy, even when substantial fluid removal and residual urea clearance were present.
ISSN:0085-2538
1523-1755
DOI:10.1038/ki.2009.525