Assessing Intensive Care Unit Acquired Weakness: An Observational Study Using Quantitative Ultrasound Shear Wave Elastography of the Rectus Femoris and Vastus Intermedius.

Introduction: Intensive care unit-acquired weakness (ICUAW) is associated with unfavorable outcomes. The current diagnostic tools for ICUAW are invasive, yield delayed results, and lack precision. This study explored the potential of shear wave elastography (SWE), an innovative ultrasound technique, to evaluate the quality changes in the lower extremity muscles of ICU patients, potentially aiding the early detection of ICUAW.

Materials and methods: We included adult patients diagnosed with ICUAW (average Medical Research Council score < 48) from December 2020 to October 2021. ICU patients were continuously monitored twice daily. Using ultrasonography, we measured the thickness (TH), cross-sectional area (CSA), pennation angle (PA), and SWE (SWE-values) modulus of the bilateral rectus femoris (RF) and vastus intermedius (VI). The diagnostic performance of each parameter was evaluated using sensitivity, specificity, and area under the receiver operating characteristic curve.

Results: Ultrasound quantification assessments were performed in 47 patients, 24 with ICUAW and 23 without ICUAW. Notably, PA decreased (RF: 11.33%, VI: 10.51%), while muscle rigidity increased (RF: 22.39%, VI: 22.50%) in ICUAW patients compared with non-ICUAW patients. The sensitivity and specificity for PA in the RF were 79.17% and 91.30%, respectively, and those for PA in VI were 79.17% and 78.26%, respectively. The use of both combinations yielded 91.67% and 73.91% sensitivity and specificity, respectively. Employing the PA of RF and SWE-values of RF together, we observed a diagnostic prediction sensitivity of 91.67% and a specificity of 60.87%.

Conclusions: ICUAW patients exhibited increased rigidity of the lower extremity muscles during their hospital stay. Ultrasonic SWE emerged as a reliable and objective tool, offering significant diagnostic value for ICUAW.