Multiple frequency bioimpedance: a bed-side technique for assessment of fluid shift patterns in a patient with severe dehydration.

This report describes the use of multiple frequency bioimpedance analysis (MFBIA) to monitor fluid changes in a patient who developed severe dehydration and recovered. Initially, the patient weighed 53.2 kg, his total body water (TBW; D(2)0 dilution) was 33.5 L, his extracellular water (ECW; Br dilution) was 19.5 L, and hydration of the fat-free mass (FFM; dual-energy X-ray absorptiometry) was normal (73%). The resistances at infinite and 0 frequency were R(inf) = 454 and R(0) = 580 ohm respectively, which predicted TBW = 33.1 L and ECW = 16.6 L. On day 7, when the weight loss was 7.2 kg, FFM had decreased by 7.4 kg, and R(inf) and R(0) had increased to 662 and 902 ohm respectively, predicting decreases of 5.8 L in TBW and 3.7 L in ECW. On recovery (day 14), all parameters had returned to baseline values. This study encourages the use of MFBIA as a bed-side technique for the serial assessment of body water compartments in patients with disturbances in fluid balance.