Phase Angle Trajectory Among Critical Care Patients: Longitudinal Decline Predicts Mortality Independent of Clinical Severity Scores.

BACKGROUND/OBJECTIVES: The phase angle (PhA) is an emerging biomarker reflecting the cellular integrity and nutritional status. This study aimed to explore potential associations between the PhA, clinical severity scores, and 60-day survival outcomes following an admission to the Intensive Care Unit (ICU).

METHODS

This prospective, single-center study included 43 critically ill patients admitted to the ICU at Evangelismos General Hospital between May and November 2024. Patients were stratified by their PhA (≤5.4° vs. >5.4°). The PhA was measured at admission and subsequently on days 5-7, 10-11, 13-14, and until discharge. Severity scores (SOFA and APACHE II) were recorded. Between-group differences were assessed using independent samples -tests and Mann-Whitney U tests, as appropriate. Survival was analyzed using Kaplan-Meier curves and Cox proportional hazards models.

RESULTS

The mean age was 54.6 ± 17 years; 63.6% were male. At ICU admission, patients with a PhA > 5.4° were significantly younger ( < 0.001) and had a higher fat-free mass ( < 0.001), greater calf circumference ( < 0.001), higher extracellular water ( < 0.001), larger mid-upper arm circumference ( = 0.009), and higher resting energy expenditure per kilogram (27.4 vs. 23.1 kcal/kg, = 0.002). The PhA declined significantly during the ICU stay ( < 0.001). The Kaplan-Meier analysis showed a significantly shorter survival in patients with a PhA ≤ 5.4° (HR: 6.32, = 0.019), which remained significant after adjusting for sepsis ( = 0.017). In a multivariable Cox regression, both PhA and APACHE II scores independently predicted mortality.

CONCLUSIONS

While limited by a small sample size and single-center design, these findings support the further exploration of the PhA as a monitoring tool in critical care.