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

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).

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 t-tests and Mann-Whitney U tests, as appropriate. Survival was analyzed using Kaplan-Meier curves and Cox proportional hazards models.

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

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.