MULTIFREQUENCY BIOELECTRICAL-IMPEDANCE FAILS TO QUANTIFY SEQUESTRATION OF ABDOMINAL FLUID

Multifrequency bioelectrical impedance analysis (MFBIA) was used to de termine the intracellular (ICW) and extracellular water (ECW) compartm ents in rats. Resistance and reactance were measured on various body s egments with frequencies ranging from 1 KHz to 1 MHz. After initial me asurements, 0.9% NaCl was injected intravenously or intraperitoneally, and changes in ECW and ICW were estimated by ILIFBIA. Important diffe rences were found between segments. In the leg, estimated ECW increase d in proportion to the volume of intravenous fluid infused, whereas es timated ICW changed minimally. However, in the trunk region, both esti mated ECW and ICW were increased with intravenous and intraperitoneal injections. Our findings indicate that MFBIA has important limitations for quantifying fluid compartments in the trunk and thus in whole bod y, especially when applied to ill patients in whom sequestration of fl uid in the trunk region frequently occurs.