Magnitude and precision of absolute blood volume estimated during hemodialysis.

Management of body fluid volumes and adequate prescription of ultrafiltration (UF) remain key issues in the treatment of chronic kidney disease patients. This study aims to estimate the magnitude as well as the precision of absolute blood volume () modeled during regular hemodialysis (HD) using standard data available with modern dialysis machines. 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 estimation. The method was applied to 21 treatments (pre-UF body mass: 65.5713.44 kg, UF-volume: 3.991.14 L) obtained in ten patients (4 female). Pre-HD was 5.40.53 L with an average coefficient of variation of 9.8% (range 1 to 22%). A significant moderate correlation was obtained when was compared to a different method applied to the same data set ( = 0.5). Specific blood volumes remained above the critical level of 65 mL/kg in 17 treatments (80.9%). 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 estimate.