DAILY HEMODIALYSIS—SELECTED TOPICS: Predicting Treatment Dose for Novel Therapies Using Urea Standard Kt / V

Calculation of urea standard Kt / V (std Kt / V ) as a dose measure for guiding novel hemodialysis or hemofiltration therapy prescription is complex since this parameter depends on the magnitude of posttreatment urea rebound. We propose here a two‐step procedure for calculating urea std Kt / V from single‐pool urea Kt / V values (sp Kt / V ) determined from serum urea concentrations in pretreatment and posttreatment blood samples. First, the dependence of urea std Kt / V on equilibrated Kt / V (e Kt / V ) was derived from a fixed‐volume single‐pool model. Second, an empirical equation for predicting urea e Kt / V from urea sp Kt / V values was determined using multiple linear regression and available data during 4‐hour hemodialysis, 2‐hour hemodialysis, and 2‐hour hemofiltration treatments. This empirical (rate/dose) equation is likely more robust for novel therapies than other equations derived from only data during conventional (4‐hour) hemodialysis treatments. The combination of these formulas allowed construction of nomograms for calculating urea std Kt / V from sp Kt / V during novel therapies. These principles were further illustrated by calculating the predicted treatment dose for daily (six times per week) hemofiltration therapy required to achieve a given urea std Kt / V .