To test diagnostic accuracy of changes in thickness (TH) and cross-sectional area (CSA) of muscle ultrasound for diagnosis of intensive care unit acquired weakness (ICU-AW). Fully conscious patients were subjected to muscle ultrasonography including measuring the changes in TH and CSA of biceps brachii (BB) muscle, vastus intermedius (VI) muscle, and rectus femoris (RF) muscles over time. 37 patients underwent muscle ultrasonography on admission day, day 4, day 7, and day 10 after ICU admission, Among them, 24 were found to have ICW-AW. Changes in muscle TH and CSA of RF muscle on the right side showed remarkably higher ROC-AUC and the range was from 0.734 to 0.888. Changes in the TH of VI muscle had fair ROC-AUC values which were 0.785 on the left side and 0.779 on the right side on the 10th day after ICU admission. Additionally, Sequential Organ Failure Assessment (SOFA), Acute Physiology, and Chronic Health Evaluation II (APACHE II) scores also showed good discriminative power on the day of admission (ROC-AUC 0.886 and 0.767, respectively). Ultrasonography of changes in muscles, especially in the TH of VI muscle on both sides and CSA of RF muscle on the right side, presented good diagnostic accuracy. However, SOFA and APACHE II scores are better options for early ICU-AW prediction due to their simplicity and time efficiency.

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Background: A common occurrence in severe illness is muscle wasting, which is defined as intensive care unit acquired weakness (ICU-AW) and characterized by flaccid tetraparesis with areflexia or hyporeflexia. Many studies revealed the tendency of changes in quantitative muscle ultrasound parameters in critical illnesses; however, the relation between those changes in muscle parameters and intensive care unit acquired weakness was unknown.Objectives: Using the Medical Research Council Criteria, test the accuracy in diagnosis of changes in quantitative muscle ultrasound for diagnosing intensive care unit acquired weakness.Methods: Patients who were conscious and positively responded to verbal commands with facial muscles were subjected to quantitative muscle ultrasonography including measuring thickness and cross-sectional area of biceps brachii (BB) muscle, vastus intermedius (VI) muscle, and rectus femoris (RF) muscles for 4 times in the next 10 days after assessing their muscle strength using the Medical Research Council score. Assessment of the diagnostic accuracy of changes in cross-sectional area and thickness of different muscle groups was made using area under the curve of the receiver operating characteristic curve (ROC–AUC). We also calculated specificity, sensitivity, negative predictive value, positive predictive value, and diagnostic accuracy of 15% threshold for reduction of thickness and 12% threshold for reduction of cross-sectional area.Results: 37 patients underwent muscle ultrasonography for 4 times and 24 were found to have ICW-AW. ROC–AUC of changes in muscle parameters were acceptable and ranged from 0.647 to 0.727. The changes in the thickness of vastus intermedius muscle on both sides while the change in thickness and cross-sectional area of rectus femoris muscle on the right side showed good diagnostic accuracy and ranged from 75.7% to 78.4%.Conclusions: Ultrasonography of the changes in muscle parameters with good diagnostic accuracy is an alternative approach for making a diagnosis of intensive care unit acquired weakness. Particularly, changes in the thickness of vastus intermedius muscle on both sides and changes in thickness and cross-sectional area of rectus femoris muscle on the right side have diagnostic potential.