Association between phase angle and daily creatinine excretion changes in critically ill patients: an approach to muscle mass

Abstract

Assessing muscle mass in critically ill patients remains challenging. This retrospective cohort study explores the potential of phase angle (PA°) derived from bioelectrical impedance analysis (BIA) as a surrogate marker for muscle mass monitoring by associating it with daily creatinine excretion (DCE), a structural and metabolic muscle mass marker. In 20 ICU patients, we observed a linear relationship between PA° and DCE at initial (S1) and follow-up (S2) points, with Rho values of 0.78 and 0.65, respectively, as well as between their percentage changes (Rho = 0.80). Multivariate analysis confirmed a strong association between changes in PA° and DCE (adjusted R² of 0.73), while changes in the extracellular water to total body water (ECW/TBW) ratio showed no significant association. This study establishes a relationship between a BIA-derived independent-weight parameter and DCE, highlighting the potential of PA° for muscle mass monitoring during acute changes, such as those seen in ICU settings. Integrating PA° into clinical practice could provide a non-invasive and reliable tool to enhance muscle assessment and support targeted interventions in critically ill patients.

Keywords: bioelectrical impedance analysis; critical care; daily creatinine excretion; muscle mass; phase angle.

FIGURE 1

Correlation between changes in daily creatinine excretion (ΔDCE%) and phase angle (ΔPA%) in critically ill patients (n = 20).

FIGURE 2

Comparison of changes in daily creatinine excretion (DCE), phase angle (PA°), and extracellular water to total body water ratio (ECW/TBW) between set 1 (S1) and set 2 (S2) in critically ill patients. Left panels represent patients with negative ∆DCE, indicating a decrease in DCE between S1 and S2, while right panels show those with positive ∆DCE. Median values with interquartile ranges are shown for DCE (mg/24 h), PA°, and ECW/TBW (%). *p < 0.05.