Nutritional state assessed by ultrasonography, but not by bioelectric impedance, predicts 28-day mortality in critically ill patients. Prospective cohort study

Background & aims Malnutrition is a disease associated with unfavorable outcomes and high prevalence among critically ill patients. The primary aim of the study was to correlate the nutritional status of patients recently admitted to the intensive care unit (ICU) with the 28-day mortality rate. The secondary aim was to establish cut-off values for the bioelectrical impedance analysis (BIA) and ultrasonography (USG) methods for the classification of the nutritional status of critically ill patients. Methods Cohort-type prospective observational study design, with the inclusion of critically ill clinical-surgical patients, ≥18 years old, mechanically ventilated. Their nutritional status was assessed by phase angle and skeletal muscle mass (using BIA), and the sectional area of the rectus femoris muscle (RFM) (using USG) within the first 48 h of ICU admission. Results Among the patients included (n = 160), the non-survivors had lower values related to the survivors for averages of the phase angle (4.4 ± 1.5° vs 4.9 ± 1.2°; p = 0.041) and sectional area of the RFM (6.1 ± 1.6 cm2/m2 vs 7.4 ± 1.8 cm2/m2; p = 0.030). Cut-off values were identified using the ROC curves for phase angle (≤4.4°), skeletal muscle mass (≤19.2 kg/m2), and sectional area of the RFM (≤5.9 cm2/m2). In multivariate logistic regression analysis, the sectional area of the RFM (≤5.9 cm2/m2) was the only independent predictor of 28-day mortality (OR = 6.08; p = 0.028). In the survival analysis, greater survival at 28 days was demonstrated for patients with phase angle >4.4° (p = 0.020) and sectional area of the RFM >5.9 cm2/m2 (p = 0.001). Malnourished patients had higher mortality than nourished patients according to the phase angle (31.5% vs 15.1%, respectively; p = 0.015) and the sectional area of the RFM (38.9% vs 6.3%, respectively; p = 0.001). Conclusions The USG of the RFM is an efficient method for both classifying the nutritional status at ICU admission and assessing the prognosis of critically ill patients.