Proximal and distal measurements of extracellular and total body water by multi-frequency bio-impedance analysis in surgical patients.

Measurements of extracellular water (ECW) and total body water (TBW) can be useful when assessing the nutritional status of surgical patients. The simple and non-invasive nature of bio-impedance techniques may allow repeat measurements to assess clinically significant changes in ECW and TBW. We have evaluated bio-impedance spectroscopy (BIS) and multi-frequency bio-impedance analysis (MFBIA) using radioisotope dilution as the independent method.