Magnitude and precision of absolute blood volume estimated during hemodialysis

Abstract

Background: Management of body fluid volumes and adequate prescription of ultrafiltration (UF) remain key issues in the treatment of chronic kidney disease patients.Objective: This study aims to estimate the magnitude as well as the precision of absolute blood volume ((Formula presented.)) modeled during regular hemodialysis (HD) using standard data available with modern dialysis machines.Methods: The estimation utilizes a two-compartment fluid model and a mathematical optimization technique to predict UF-induced changes in hematocrit measured by available on-line techniques. The method does not rely on a specific hematocrit sensor or a specific UF or volume infusion protocol and uses modeling and prediction tools to quantify the error in (Formula presented.) estimation.Results: The method was applied to 21 treatments (pre-UF body mass: 65.57 (Formula presented.) 13.44 kg, UF-volume: 3.99 (Formula presented.) 1.14 L) obtained in ten patients (4 female). Pre-HD (Formula presented.) was 5.4 (Formula presented.) 0.53 L with an average coefficient of variation of 9.8% (range 1 to 22%). A significant moderate correlation was obtained when (Formula presented.) was compared to a different method applied to the same data set (r = 0.5). Specific blood volumes remained above the critical level of 65 mL/kg in 17 treatments (80.9%).Conclusion: The method offers the opportunity to detect critical blood volumes during HD and to judge the quality and reliability of that information based on the precision of the (Formula presented.) estimate.