Journal Article

Solute clearance in CRRT: prescribed dose versus actual delivered dose

William D. Lyndon, Keith M. Wille and Ashita J. Tolwani

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 27, issue 3, pages 952-956
Published in print March 2012 | ISSN: 0931-0509
Published online September 2011 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/gfr480
Solute clearance in CRRT: prescribed dose versus actual delivered dose

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Background.

Substantial efforts have been made toward defining the dose threshold of continuous renal replacement therapy (CRRT) associated with improved survival in critically ill patients with acute kidney injury. Published studies have used prescribed effluent rates, expressed as total effluent volume (TEV) per weight and unit time (mL/kg/h), as a surrogate for dose. The purpose of this study was to compare differences in CRRT dose based on prescribed effluent rate, measured TEV and direct measurement of urea and creatinine clearance.

Methods.

We analyzed data that had been prospectively collected on 200 patients enrolled in a randomized trial comparing survival with a prescribed effluent rate of 20 mL/kg/h (standard dose) to 35 mL/kg/h (high dose) using pre-dilution continuous venovenous hemodiafiltration (CVVHDF). Filters were changed every 72 h. Blood urea nitrogen (BUN), serum creatinine (SCr), effluent urea nitrogen (EUN) and effluent creatinine (ECr) were collected daily. Actual delivered dose was calculated as: (EUN/BUN)*TEV for urea and (ECr/SCr)*TEV for creatinine. Data were available for 165 patients.

Results.

In both groups, prescribed dose differed significantly from the measured TEV dose (P < 0.001). In the standard dose group, there was no difference between the measured TEV dose and actual delivered urea and creatinine clearances. However, in the high-dose group, measured TEV dose differed significantly from delivered urea clearance by 7.1% (P < 0.001) and creatinine clearance by 13.9% (P < 0.001).

Conclusions.

Dose based on prescribed effluent rate or measured TEV is a poor substitute for actual CVVHDF creatinine and urea clearance.

Keywords: acute kidney injury; continuous renal replacement therapy; critical care nephrology; dialysis dose

Journal Article.  3139 words.  Illustrated.

Subjects: Nephrology

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