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Abstract: TH-PO248

Estimation of Fluid Overload in Hemodialysis Patients Using Leg Bioimpedance

Session Information

Category: Dialysis

  • 801 Dialysis: Hemodialysis and Frequent Dialysis

Authors

  • Zhu, Fansan, Renal Research Institute, New York, New York, United States
  • Kotanko, Peter, Renal Research Institute, New York, New York, United States
Background

While 8-point bioimpedance provides a simple and convenient technique to measure segmental and whole body extracellular (ECV) and intracellular volume (ICV), it cannot quantitate fluid overload (FO). The aim of this study was to evaluate whether FO in hemodialysis patients can be estimated with a leg bioimpedance model.

Methods

Leg resistances were measured with four metal electrodes built into the footplate (Fig.1). Leg extracellular resistance (RL; at 1 kHz frequency) and volume (ECVL) were measured. ECV2L represents ECV of both legs combined. Body height (H), pre-HD weight (Wt) and ultrafiltration volume (UFV) were recorded. Leg hydration index (α, Ω/cm) was defined as RL/H in healthy subjects (HS; αHS= RLHS/HHS) and patients (αP= RLP/HP), respectively. The difference between average αHS (α’HS) in the HS and patients (Δα=α’HS - αP) reflects the degree of leg FO. Δα*ECV2L and body mass index (BMI=Wt/H2) were considered as independent variables in a regression model that was built to explore the relationship between UFV and FO.

Results

Sixteen HS (age 34.8±7.6 years, H 168.7±9.5 cm, Wt 72.7±17.3 kg) and thirteen HD patients (age 47±16 years, H 169.5±4.5 cm, Wt 83.9±5.4 kg) were studied pre-HD. Leg resistance (RL) was 217.3±55.3 Ω pre-HD, UFV was 3862±1320 mL. Average αHS (α’HS), defined as the standard index of leg normal hydration, was 1.8±0.3 Ω/cm. Δα was 0.24±0.37 Ω/cm in the HD patients. FO [in mL] was estimated as 534 + 0.36*Δα*ECV2L + 70.24*BMI. UFV was highly correlated with estimated FO (R2= 0.82, p<0.0001). Bland-Altman analysis showed a bias of 0.15±394 mL (Fig.2).

Conclusion

Estimated leg hydration correlates well with FO in hemodialysis patients. A model with leg resistance and BMI as independent variables can predict FO in HD patients.