Kidney Week

Abstract: FR-PO754

Determination of Calf Normalized Resistivity at 50 kHz in the General Population

Session Information

• Dialysis: Inflammation and Infection
  October 26, 2018 | Location: Exhibit Hall, San Diego Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Dialysis

• 701 Dialysis: Hemodialysis and Frequent Dialysis

Authors

• Zhu, Fansan, Renal Research Institute, New York, New York, United States

Fansan Zhu,

• Abbas, Samer R., Renal Research Institute, New York, New York, United States

Samer R. Abbas,

• Rosales, Laura, Renal Research Institute, New York, New York, United States

Laura Rosales,

• Levin, Nathan W., Renal Research Institute, New York, New York, United States

Nathan W. Levin,

• Kotanko, Peter, Renal Research Institute, New York, New York, United States

Peter Kotanko,

Background

We have developed 5 kHz calf normalized resistivity (CNR₅) method to identify degrees of fluid status in dialysis patients. However, the 50 kHz BIA method have been used in clinical studies for many years. The aim of this study was to evaluate whether 50 kHz CNR (CNR₅₀) could be used to determine fluid status by comparing CNR₅ and CNR₅₀ chosen randomly from a general population.

Methods

Subjects from a general population were studied once. Calf multi-frequency bioimpedance spectroscopy measurements (Hydra 4200) was performed in the supine position. Further measurements included body height, weight and calf circumference. Resistances at 5 kHz (R₅) and at 50 kHz (R₅₀) respectively were extracted from the raw data. Calf resistivities (Rho₅ and Rho₅₀) were calculated based on resistances and average cross-sectional areas over a calf length measurement of 10 cm. CNR₅ and CNR₅₀ were obtained by normalizing calf resistivities with body mass index (BMI).

Results

Ninety-one subjects (sex: 49 f, age: 57±10 year, BMI: 27.9± 4.7 kg/m²) were evaluated. Although calf R₅₀ (R²=0.89, p<0.0001), Rho₅₀ (R²=0.9, p<0.0001) and CNR₅₀ (R²=0.91, p<0.0001) highly correlated with CNR₅, Rho₅ and CNR₅ respectively, the values of R₅₀ (36.6±6.0, Ohm), Rho₅₀ (352.9±60.6, Ohm*cm) and CNR₅₀ (13.0±2.5, 10^-2 *Ohm*m³/kg) were significantly lower than in R₅ (48.1±7.2, Ohm), Rho₅ (464.9±79, Ohm*cm) and CNR₅ (17.1±3, 10^-2 *Ohm*m³/kg) respectively (Fig.1 and Fig.2). Bland-Altman analysis showed that the differences between CNR₅ and CNR₅₀ was 4.08±0.95 10^-2 *Ohm*m³/kg (Fig.3). The difference between CNR₅ and CNR₅₀ was weakly (R²=0.13) but significantly (p<0.001) associated with subject age (Fig.4).

Conclusion

Values of 50 kHz data R₅₀, Rho₅₀ and CNR₅₀ were lower than that of 5 kHz data with BIA respectively, presumably because a 50 kHz current passes into part of the intracellular space, while this does not occur measurably with 5 kHz current. This difference offers the practicability of using the CNR₅₀ range in healthy subjects, as a criterion of normal fluid status.

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