The Problem with Kt/V: Dialysis Dose should be Normalized to Metabolic Rate not Volume

Abstract

Current estimates of hemodialysis adequacy are based on calculations of small solute clearance or changes in online measurements of ionic conductance. A minimum target value of the widely used, dimensionless parameter, Kt/V(urea) has been adopted nationally and internationally to represent appropriate dialysis delivery. Based on the principles of allometry, which permit the calculation of scaling equations between the mass of an organism and other parameters, we propose that dialysis dose should be normalized to waste product generation (estimated by metabolic rate). The allometric equations predict a nonlinear correlation between body mass and dialysis dose, such that smaller individuals require proportionately ''more'' dialysis than larger persons. The argument we present is congruent with outcome data as it relates to sex, race, and body size, as well as supportive of studies suggesting that certain groups (e.g., pregnant women, critically ill patients, diabetics) require greater dialysis delivery than the hemodialysis population in general.