Upper Arm Muscular Echogenicity Predicts Intensive Care Unit-acquired Weakness in Critically Ill Patients

OBJECTIVES: This retrospective observational study investigated whether the degree of muscular echogenicity in patients admitted to the intensive care unit (ICU) could help with the early detection of ICU-acquired weakness (ICU-AW) and predict physical function at hospital discharge. METHODS: Twenty-five patients who were mechanically ventilated for more than 48 h in the ICU were enrolled. We also enrolled 23 outpatients with nonmuscular diseases as the control group. The target sites for measuring muscular echogenicity were the upper arm and lower leg. First, the muscular echogenicity was compared between surviving nonsurgical patients admitted to the ICU and stable outpatients with nonmuscular diseases. Second, we investigated the relationship between muscular echogenicity and clinical features, e.g., the manual muscle test (MMT), Medical Research Council (MRC) sum score, and Functional Independence Measure (FIM). RESULTS: Muscular echogenicity in the upper arm in the ICU group was significantly higher than that in the control group. In the ICU group, the degree of muscular echogenicity of the upper arm was inversely correlated with the MMT of elbow flexion (P=0.006; r=−0.532) and the MRC sum score (P=0.002; r=−0.591). However, muscular echogenicity of the upper arm did not correlate with functional FIM (P=0.100; r=−0.344) at hospital discharge. CONCLUSIONS: Critically ill patients can experience pathological muscle weakness associated with increased muscular echogenicity in the upper arm. Additionally, the degree of muscular echogenicity in the upper arm correlated with the MRC sum score and can facilitate early detection of ICU-AW. The relationship between echogenicity and functional outcome at discharge requires elucidation.