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- Title
The urea {clearance × dialysis time} product (Kt) as an outcome-based measure of hemodialysis dose.
- Authors
Lowrie, Edmund G.; Chertow, Glenn M.; Lew, Nancy L.; Lazarus, J. Michael; Owen, William F.
- Abstract
The urea {clearance × dialysis time} product (Kt) as an outcome-based measure of hemodialysis dose. Background. The normalized treatment ratio [Kt/V = the ratio of the urea {clearance × time} product to total body water] and the urea reduction ratio (URR) have become widely accepted measures of dialysis dose. Both are related to and derived from pharmacokinetic models of blood urea concentration during the dialysis cycle. Theoretical reconsideration of the models revealed that the premise about V on which they rest (that is, that V is a passive diluent with no survival-associated properties of its own) is flawed if the intended use of the models is for profiling clinical outcome (for example, mortality) rather than estimating urea concentration. As a proxy for body mass, V has survival-associated properties of its own. Thus, indexing {clearance × time} to body size could create an offsetting combination whereby one measure favorably associated with survival (Kt) is divided by another (for example, V). Observed clinical paradoxes support that interpretation. For example, patients with a low body mass have both higher URR and higher mortality than heavier patients. Increasing mortality is often observed at high URR, suggesting the possibility of “over-dialysis.” Black patients tend to be treated at lower URR than whites but enjoy better survival on dialysis. Therefore, {clearance × time} was evaluated as an outcome-based measure of dialysis dose, not indexed to V, and various body size estimates were evaluated as separate and distinct measures. Methods. The retrospective sample included 17,141 black and white hemodialysis patients treated three times per week. Logistic regression analysis was used to evaluate death odds in age-, gender-, race-, and diabetes-adjusted models. Kt and five body size estimates (total body water or V, body weight, body weight adjusted for height, body surface area, and body mass index) were evaluated...
- Subjects
HEMODIALYSIS; BODY size
- Publication
Kidney International, 1999, Vol 56, Issue 2, p729
- ISSN
0085-2538
- Publication type
Article
- DOI
10.1046/j.1523-1755.1999.00584.x