Monitoring of extracellular and total body water during haemodialysis using multifrequency bio-electrical impedance analysis

Multifrequency bio-electrical impedance analysis (MFBIA) was evaluated as a technique for monitoring changes in extracellular and total body water (ECW and TBW, respectively) of 15 subjects during dialysis. Dilution analysis, using deuterium oxide and sodium bromide, was also performed on each subject before dialysis so that prediction equations for ECW and TBW based on the MFBIA measures could be developed. These prediction equations were then used to estimate water compartment volume changes during dialysis and compared with volumetric measures of the dialysate removed. The results show that MFBIA does not accurately measure ECW and TBW changes during dialysis. The MFBIA measures tend to overestimate the changes and are not sufficiently precise to be clinically useful.