Low phase angle in critically ill older patients is associated with late mortality: A prospective study

The aim of this study was to ascertain the accuracy of phase angle (PhA) as a predictor of mortality during intensive care unit (ICU) stay (M_ICU) and at 28 (M₂₈) and 60 d (M₆₀) after ICU admission among patients aged >60 y.

Patients aged >60 y who were under mechanical ventilation (MV) ≥48 h were included once they were hemodynamically stable. PhA was measured by single-frequency bioelectrical impedance analysis up to 48 h after admission. ICU prognostic scores, functional scale, and nutritional assessments were performed in the first 24 h. Patients were followed for 60 d after ICU admission.

We enrolled 102 patients into the present study. PhA was significantly higher (P < 0.001) in survivors at M_ICU, M₂₈, and M₆₀. Areas under the receiving operator characteristic curves for M_ICU, M_28, and M₆₀ were 0.77 (95% confidence interval [CI], 0.67-0.86), 0.71 (95% CI, 0.60-0.82), and 0.71 (95% CI, 0.60-0.81), respectively. The PhA cutoff to predict mortality was 3.29° for males at M_ICU, M₂₈, and M₆₀ and lower for females at M₂₈ (2.63°) and M₆₀ (3.01°). PhA better discriminated M₆₀ than conventional prognostic scores. Logistic regression showed that even after controlling for other factors, PhA was a protective factor against late mortality. Survival analysis at 60 d revealed that low PhA was associated with lower median survival (18 versus 58 d; log-rank P < 0.001).

Low PhA values are associated with higher late mortality and a short survival time at 60 d in critically ill older adults. Low PhA values can be considered a useful ICU prognostic score in similar populations.