Preprint Review Version 1 This version is not peer-reviewed

Classification of Hydration: Two Approaches Using Bioimpedance

Version 1 : Received: 5 March 2019 / Approved: 7 March 2019 / Online: 7 March 2019 (06:52:39 CET)

A peer-reviewed article of this Preprint also exists.

Lukaski, H.C.; Vega Diaz, N.; Talluri, A.; Nescolarde, L. Classification of Hydration in Clinical Conditions: Indirect and Direct Approaches Using Bioimpedance. Nutrients 2019, 11, 809. Lukaski, H.C.; Vega Diaz, N.; Talluri, A.; Nescolarde, L. Classification of Hydration in Clinical Conditions: Indirect and Direct Approaches Using Bioimpedance. Nutrients 2019, 11, 809.

Journal reference: Nutrients 2019, 11, 809
DOI: 10.3390/nu11040809

Abstract

Although the need to assess hydration is well recognized, laboratory tests and clinical impressions are impractical and lack sensitivity to be clinically meaningful. Different approaches use bioelectrical impedance measurements to overcome some of these limitations and aid in classification of hydration status. One indirect approach utilizes single or multiple frequency bioimpedance in regression equations and theoretical models, respectively, with anthropometric measurements to predict fluid volumes (bioelectrical impedance spectroscopy; BIS) and estimate fluid overload based on deviation of calculated to reference extracellular fluid volume. Alternatively, bioimpedance vector analysis (BIVA) uses direct phase-sensitive measurements of resistance and reactance, measured at 50 kHz, normalized for height, then plotted on a bivariate graph, resulting in a vector with length related to fluid content normalized by standing height, and direction with phase angle that indexes hydration status. Comparison with healthy population norms enables BIVA to classify (normal, under- and over-) and rank (change relative to pre-treatment) hydration independent of body weight. Each approach has wide-ranging uses in evaluation and management of clinical groups with overhydration with an evolving emphasis on prognosis. This review discusses the advantages and limitations of BIS and BIVA for hydration assessment with comments on future applications.

Subject Areas

fluid overload; resistance; reactance; bioelectrical impedance vector analysis; bioelectrical impedance spectroscopy; malnutrition

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