Volume Overload Assessed by Vector Impedance Analysis and Physical Function in Hemodialysis Patients

Loss of skeletal muscle mass in chronic kidney disease is strongly associated with reduced physical function and increased mortality. Although well recognized, the impact of volume overload, on physical function and muscle strength, remains understudied. This study aimed to assess the association between volume overload, physical function, and muscle strength in individuals on hemodialysis.

Fifty-two individuals on hemodialysis were included. Muscle strength was assessed using hand dynamometry, defining dynapenia as muscle strength < 20 kg in women and < 30 kg in men. Physical function was measured using the short physical performance battery, with "low physical function" defined as a score ≤ 8.0. Bioelectrical impedance vector analysis z-score graph was plotted according to physical function and muscle strength classification as normal or reduced. Resistance and reactance data, normalized to height, were converted into z-scores and plotted on a z-score graph. The comparison of bioelectrical impedance vector analysis between groups was performed using Hotelling's T ² test. In addition, multivariate logistic regression was used to explore the association between volume overload with muscle strength and physical function.

Bioelectrical impedance vector analysis z-score graphs showed that individuals with reduced physical function were outside the 95th percentile of the major axis, indicating volume overload, while those with normal physical function had adequate hydration status (p < 0.0001). In Model 1 of the multivariate logistic regression, volume overload was associated with low physical function. In Model 2, none of the independent variables were associated with muscle strength.

Individuals on hemodialysis with reduced physical function exhibited higher volume overload. Although volume overload is associated with worse physical function, no association was observed with muscle strength.