The hemoconcentration effect for middle weight solutes in hemodialysis is corrected by oversimplified methods based on hematocrit changes or distribution volume variations. Here we implemented a variable volume dual pool kinetic model targeted at obtaining a precise correction factor equation for extracellularly distributed solutes based on relevant kinetic parameters such as the ultrafiltration to dry weight ratio UF/DW, the dialyzer clearance, Kd, the intercompartment mass-transfer coefficient, Kc, and the central compartment to extracellular volume ratio, α. More than 300,000 solutions of the model were computed, performing a sweep among physiological values of the proposed kinetic parameters, resulting in a linear regression denoted by the expression fcorr = 1.0707 - 5.2246 (UF/DW) - 0.0005 Kd - 0.0004 Kc - 0.0007 α, with an excellent coefficient of determination R2 = 0.983. The presented fcorr provides a substantial extension of the currently implemented methods to estimate the hemoconcentration factor for middle and high molecular weight extracellular distributed solutes in hemodialysis.
Keywords: Correction factor; distribution volume; hemoconcentration; on-line hemodiafiltration; uremic toxins.