Abstract

ROS NOGALES, Ruth; MANSO GIL, Mª Teresa; PALACIOS GARCIA, Gema  and  RODRIGUEZ PENA, Jacoba. Bioimpedance vector and spectroscopic analysis: assessing hydration status using both methods in haemodialysis. Enferm Nefrol [online]. 2013, vol.16, n.1, pp.7-14. ISSN 2255-3517.  https://dx.doi.org/10.4321/S2254-28842013000100002.

Bioimpedance analysis is a useful tool for determining the nutritional and hydration status of haemodialysis patients. The two most commonly used systems are bioimpedance vector single frequency analysis and bioimpedance spectroscopic multiple frequency analysis, which use different criteria to classify the hydration status of the dialysed patient. The single frequency bioimpedance vector system uses a scale of 7 points ranging from a value of 3 (most hydration) to a value of -3 (most dehydration), defining hyperhydration when the vector is on the hydration axis below the tolerance ellipse of 75% (values 3 and 2 on the scale). Multi-frequency spectroscopy uses two criteria to define the pre-dialysis state of hyperhydration: OH more than 2.5 litres or more than 15% of the extracellular water volume. The aim of this study was to analyse the degree of concordance between the two systems of bioimpedance in defining the state of hyperhydration of haemodialysis patients. A transversal study was carried out on 54 patients undergoing haemodialysis, performing a bioimpedance analysis with single frequency vector and multi-frequency spectroscopic monitors immediately before a haemodialysis session. The degree of equivalence in the definition of hyperhydration between the two monitors was greater when the criterion of OH>15% of extracellular water was used in the multi-frequency monitor (kappa index 0.81, excellent concordance) than when the criterion of OH>2.5 litres was used (kappa index 0.71, acceptable concordance). Conclusions: There is a good relationship between the hydration vector scale and OH value (excess hydration). The criteria used by the single-frequency vector and multi-frequency spectroscopic monitors show acceptable equivalence and their results can be interchangeable.

Keywords : Bioimpedance; Vector; Spectroscopic; Hyperhydration.

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