Towards personalized hydration assessment in patients, based on measurement of total body electrical resistance: Back to basics.

Background & Aims: Assessment of tissue hydration by conventional bioelectrical impedance analysis (BIA) has produced conflicting results because of flaws in the algorithms that are used to translate measurements of total body electrical resistance (TBER) into liters of body water. This type of error can be eliminated by a return to the TBER measurement itself, without attempting to convert Ohms into liters of body water. Aims of this study were to quantify tissue hydration based on TBER, to establish TBER normal values (TBER), to improve the prediction of TBER values in individual patients, and to evaluate this approach in patients on hemodialysis (HD).

Methods: TBER values were obtained in 213 healthy controls and corrected for body height (H-TBER). Inter-individual H-TBER variability was reduced by correction for arm muscle cross-sectional area (AMA). Performance of this approach was evaluated in 94 patients on HD.

Results: H-TBER was inversely related to AMA. Correction for AMA reduced the H-TBER standard deviation by 31% in men and 23% in women. When applied to patients on HD, H-TBER changes within subjects were inversely related to ultrafiltration volumes, with a mean R of 0.95 ± 0.04 in men and 0.93 ± 0.07 in women. Clinically significant H-TBER increments occurred after volume reductions of 0.39 ± 0.25 L in men and 0.37 ± 0.18 L in women.

Conclusions: TBER measurements, corrected for height and AMA, have the potential to become an objective and sensitive method to assess hydration in patients. Its clinical value remains to be shown in intervention studies.