Accuracy of Bioimpedance Modalities for Fluid Assessment in Hemodialysis
Patients: A Randomized Observational Study
Fluid overload is an independent risk factor for morbidity and
mortality in both adult and pediatric critically ill patients.
However, measuring fluid overload is not consistent nor dependable.
Gold standards for fluid overload assessment, such as air
displacement plethysmography or bromide and deuterium dilutions
are impractical in the clinical setting as they require specific devices,
specific expertise, and are time-consuming, which has
led to these techniques being mainly used for research purposes.
Weights and measurements of total fluid balance have been used
as a surrogate marker; however, these are known to be inaccurate.
Specific physical exam findings, static and dynamic vital signs,
imaging modalities, and laboratory data have been
used for fluid evaluation but have large variability in assessments.
Bioimpedance analysis is a form of fluid assessment
that has been used to evaluate total body water volume,
intracellular water volume, and extracellular water volume
and has been studied for over the last 5 decades.
There are three major techniques of measuring BIA: Single Frequency,
Multi-frequency, and Bioimpedance Spectroscopy.
Each of these methodologies uses different equations and theories
to derive fluid status, and therefore have inherent variations in fluid
The few who have evaluated their accuracy found strong inverse
associations between estimated VTBW as assessed by BIA and
net ultrafiltration volume, with VUF, net explaining 92-99% of
variability in VTBW measurements.
Although studies have been performed that compare BIA to other
existing technologies, there are few studies comparing various
BIA methods with each other.
Nephrol Open J. 2020; 6(1): 1-7. doi: 10.17140/NPOJ-6-124