Evaluation of multifrequency bioelectrical impedance analysis for the assessment of total body water and extracellular water in healthy cats and dogs

The assessment of total body water (TBW) and extracellular water (ECW) is important in any species to facilitate understanding changes that occur in the water compartments associated with both physiological (pregnancy, growth, exercise, hypothermia, hyperthermia) and pathophysiological (malnutrition, critical illness, chronic renal disease, dialysis, cardiac disease, infection) states. Multifrequency bioelectrical impedance analysis (MF-BIA) is an electrical method of assessing body composition that has the potential to quantify TBW, ECW, and intracellular water (ICW), and therefore enable prediction of fat free mass (FFM), fat mass (FM), and body cell mass (BCM). The purpose of this study was to (1) develop scaling constants and assess the effect of animal position, animal length measurement, and electrode configuration on the volume prediction accuracy of the Hydra ECF/ICF Bio-Impedance Analyzer (Model 4200, Xitron Technologies, San Diego, CA) compared to TBW estimated by deuterium water (D₂O) space and ECW estimated by bromide (Br) space in healthy cats; (2) cross validate the scaling constants developed for healthy cats in a separate population of cats; (3) develop scaling constants and assess the effect of anesthesia, animal position, animal length measurement, electrode type, and electrode configuration on the volume prediction accuracy of the Hydra ECF/ICF Bio-Impedance Analyzer compared to TBW estimated by D ₂O dilution, and ECW estimated by bromide space in healthy adult dogs.; There were no significant differences between the lead and height configurations on the MF-BIA predicted TBW or ECW. There were no significant differences between the MF-BIA predicted TBW and that determined by deuterium dilution. The standard error of the estimate for the prediction of TBW in the validation cats, cross validation cats, and validation dogs ranged from 9.96–23.7%, 9.97–18.3% and 5.88–20.4%, respectively. There were no significant differences between the MF-BIA predicted ECW and that determined by bromide space. The standard error of the estimate for the prediction of ECW in the validation cats, cross validation cats, and validation dogs ranged from 6.87–15.3%, 7.29–15.2% and 6.83–17.2%, respectively. MF-BIA is a practical, safe, non-invasive, rapid, and portable technique to assess TBW and ECW in healthy cats and dogs obviating the need for alternative laborious dilution techniques.