Blood volume analysis as a guide for dry weight determination in chronic hemodialysis patients: a crossover study

Abstract

Background: Volume overload and depletion both lead to high morbidity and mortality. Achieving euvolemia is a challenge in patients with end stage kidney disease on hemodialysis (HD). Blood volume analysis (BVA) uses radiolabeled albumin to determine intravascular blood volume (BV). The measured BV is compared to an ideal BV (validated in healthy controls). We hypothesized that BVA could be used in HD to evaluate the adequacy of the current clinically prescribed "estimated dry weight" (EDW) and to titrate EDW in order to improve overall volume status. We were also interested in the reproducibility of BVA results in end stage kidney disease.

Methods: Twelve adults on chronic HD were recruited; 10 completed the study. BVA (Daxor, New York, NY, USA) was used to measure BV at baseline. EDW was kept the same if the patient was deemed to be euvolemic by BVA otherwise, the prescribed EDW was changed with the aim that measured BV would match ideal BV. A second BVA measurement was done 1-3 months later in order to measure BV again.

Results: Based on BVA, 6/10 patients were euvolemic at baseline and 5/10 were euvolemic at the second measurement. When comparing patients who had their prescribed EDW changed after the initial BVA to those who did not, both groups had similar differences between measured and ideal BV (P = 0.75). BV values were unchanged at the second measurement (P = 0.34) and there was no linear correlation between BV change and weight change (r² = 0.08).

Conclusions: This pilot study is the first longitudinal measurement of BVA in HD patients. It revealed that changing weight did not proportionally change intravascular BV. BV remained stable for 1-3 months. BVA may not be helpful in clinically stable HD patients but studies on patients with hemodynamic instability and uncertain volume status are needed.

Trial registration: ClinicalTrials.gov (NCT02717533), first registered February 4, 2015.

Keywords: Absolute blood volume; dry weight; hemodialysis; Iodine radioisotopes/diagnostic use; Ultrafiltration; Volume control; Volume status.

Fig. 1

Participant flow chart. BVA blood volume analysis, EDW estimated dry weight

Fig. 2

Change in measured BV between 1st and 2nd BVA (in %) according to change in measured post dialysis weight (in kg). Change in measured BV(blood volume) (y-axis) is the difference between measured BV at the second BVA (blood volume analysis measurement) and the BV measured at the first BVA. The change in post-HD (post-hemodialysis) (y-axis) weight equals the post-HD weight on the day of the second BVA minus the post-HD weight on the day of the first BVA. Both the change in measured BV and the change in post-HD weights were calculated for every patient. Linear regression was performed and shows no linear relationship between changes in post-HD weight and changes in measured BV (coefficient of determination, r ² = 0.08)