title: Do Bioimpedance Measurements of Over-Hydration Accurately Reflect Post-Haemodialysis Weight Changes?
abstract: BACKGROUND
  Bioelectrical impedance spectroscopy (BIS) devices are being used to determine ultrafiltration requirements to achieve target weight for haemodialysis (HD) patients. Pre-dialysis measurements are more convenient for both patients and staff. We wished to compare the changes in pre- and post-dialysis hydration measured by BIS with actual weight loss.
  
  
  METHODS
  We compared paired BIS measurements made pre and post HD using a BIS device based on a 3-compartmental model, designed to provide information on extracellular water (ECW) excess.
  
  
  RESULTS
  BIS was measured in 49 HD patients, 35 male (71.4%) with mean age 67.6 ± 14.2. Weight fell significantly from 69.2 ± 17.8 to 67.6 ± 17.4 kg, and BIS over hydration (OH) from 4.5 ± 3.3.4 to 3.4 ± 2.9 litres, and ECW from 16.8 ± 4.8 to 15.5 ± 4.4 litres, but there was no change in the amount of intracellular water. Weight loss correlated positively with the change in ECW, but exceeded the fall in OH; mean bias -0.58 (95% confidence limits -3.6 to 4.8 kg).
  
  
  CONCLUSIONS
  We measured OH pre and post HD, but did not find that the change in OH correlated with changes in body weight. Although there was a correlation between changes in OH and ECW, there was none for weight. Our findings do not support total reliance on pre-dialysis BIS alone for assessing volume status in HD patients, but rather BIS should be considered an aid to clinical assessment of volume status.
authors: Faculty of Medicine, Mahasarakham University, Maha Sarakham, Thailand.
authors: Kamonwan
authors: K
authors: Tangvoraphonkchai
authors: Andrew
authors: A
authors: Davenport
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001826:Body Fluids; D001835:Body Weight; D017097:Electric Impedance; D006801:Humans; D008875:Middle Aged; D006435:Renal Dialysis