Sensitivity of total body electrical resistance measurements in detecting extracellular volume expansion induced by infusion of NaCl 0.9.

BACKGROUND

Fluid balance management in hospitalized patients is hampered by the limited sensitivity of currently available tools. The aim of this study was to assess the sensitivity of total body electrical resistance (TBER) measurements for the detection of extracellular volume (ECV) expansion.

METHODS

TBER and plasma resistivity (ρplasma) were measured during a 4-h infusion of NaCl 0.9% at a rate of 500 mL/h in 23 patients undergoing a diagnostic saline infusion test for primary hyperaldosteronism. Extracellular fluid gain (EFG) was defined as infusion volume minus urinary volume.

RESULTS

Infusion of 2.0 L NaCl 0.9% was associated with a mean diuresis of 1.1 ± 0.5 L, an EFG of 0.9 ± 0.5 L, a decrease in ρplasma of 1.1 ± 0.7 Ω·cm or 1.7 ± 1.0% (P < 0.001), and a decline in TBER of 23.2 ± 10.9 Ω or 4.6 ± 2.2% (P < 0.001). At group level, infusion of 80 mL saline was sufficient to induce a statistically significant decline in mean TBER. At personal level, the decline in TBER was significant on 76% of occasions after an EFG of 0.5-0.75 L, and on all occasions after an EFG of 1.0 L or greater.

CONCLUSION

Raw TBER data are very informative for the detection of ECV expansion induced by the infusion of NaCl 0.9%, with a sensitivity at a personal level that is relevant for clinical practice.