Abstract
Bioelectrical impedance analysis (BIA) is a method that can accurately measure total body water (TBW), intracellular water (ICW), extracellular water (ECW), soft lean mass (SLM) and body fat mass (BFM). It is considered to be a preferable technique for determining dry weight (DW) in hemodialysis (HD) patients. InBody S20, a body composition analyzer, consists of a multifrequency and eight-polar tactile-electrode impedance method, and both its precision and reproducibility have been well established. Recently, the clinical application of this method for HD patients has been reported.
The present study investigated whether or not bioelectrical impedance is a useful method for estimating DW. The subjects comprised 41 chronic HD patients. In addition to routine blood tests, plasma human atrial natriuretic peptide (hANP) was measured. Body fluid components were measured by InBody S20 before and after HD. In addition, the cardiothoracic ratio (CTR) on chest Xp and dilatation of the inferior vena cava (IVC) on ultrasonography were measured after HD. The excess fluid volume (Edema score) was then estimated based on the ratio of ECW to TBW.
As a result, 1) The levels of hANP significantly correlated with the CTR and IVC during expiration (IVCe) (p<0.01 and p<0.05, respectively). 2) TBW, ECW and ICW all significantly decreased after HD (p<0.001) and correlated with IVCe (p<0.001). 3) The percentage change in TBW before and after HD (%TBW) significantly correlated with that of blood volume (%BV) and circulating plasma volume (%CPV) (p<0.001). 4) The ECW/TBW ratio significantly decreased after HD (p<0.001) and correlated with the levels of hANP (p<0.001). 5) DW determined by BIA (BIA-DW) after HD, which is equal to the BW when the ECW/TBW ratio is 0.38, significantly correlated with clinical DW (cDW) (r=0.99, p<0.001).
In conclusion, InBody S20, immediately, and non-invasively provides the information regarding body fluid components and body composition in HD patients. Especially, the ECW/TBW ratio and BIA-DW after HD are considered useful markers for estimating DW.
