BACKGROUND - Bioelectrical impedance analysis (BIA) is a noninvasive rapid and simple bedside technique that can be used to predict total body water (TBW), extracellular water (ECW), and intracellular water (ICW) and identify altered fluid distribution following critical illness.
METHODS - An equivalence study of BIA in 32 hospitalized elderly patients was compared with reference standard dilutional measurements of deuterated water (TBW) and sodium bromide (ECW). The results were compared with anthropometric equations commonly used to predict TBW.
RESULTS - There was variability in TBW content among the participating hospitalized elderly patients. This variability was within (+/-5 L) and the percent difference between the standard and BIA was as follows: mean (range) -4.1% (-18.5 to 11.2). BIA reliably predicted TBW and ECW in individual participants, whereas standard prediction equations uniformly over- or underestimated TBW in individuals and whole group population.
CONCLUSION - TBW in hospitalized elderly patients can be estimated noninvasively by bedside BIA. Standardized anthropometric equations have to be used with caution in this population.