Ultrasonographic assessment of muscle layer thickness and its relation to patient outcome in a medical intensive care unit

Abstract

Low skeletal muscle mass in ICU patients is associated with poor clinical outcome. Ultrasonography is a noninvasive method that can measure muscle thickness at the bedside. We aimed at studying the relation of the ultrasonography measured muscle layer thickness (MLT) at time of ICU admission with the patients' outcome namely mortality, duration of mechanical ventilation (MV) and ICU length of stay (LOS). In addition to define the best cut-off values that can predict mortality in medical ICU patients. this observational prospective study was conducted on 454 adult critically ill patients admitted to the medical ICU of a university hospital. At the time of admission, MLT of the anterior mid-arm and lower 1/3 thigh were assessed using ultrasonography with and without transducer compression. The clinical scores for assessment of disease severity; Acute Physiology and Chronic Health Evaluation score (APACHE-II) and Sequential Organ Failure Assessment score (SOFA) in addition to nutrition risk; modified Nutrition Risk in Critically ill score (mNUTRIC) were estimated for all patients. ICU LOS, duration on MV and mortality were reported. The mean age of our patients was 51 years±19. The ICU mortality rate was 36.56%. The baseline MLT was negatively associated with APACHE-II, SOFA and NUTRIC scores but not with duration of MV or ICU-LOS. The non-survivors had lower values of baseline MLT. A cut-off value of 0.895cm (AUC: 0.649, 95% CI of 0.595-0.703) using the mid-arms as a reference point with maximum probe compression showed the highest sensitivity (90%) to predict mortality compared to other techniques however with low specificity (22%). the baseline ultrasonography measured mid-arm MLT is a sensitive risk assessment tool that can reflect disease severity and predict ICU mortality.