Peripheral muscular ultrasound as outcome assessment tool in critically ill patients on mechanical ventilation: An observational cohort study.

Background & Aims: Survivors of critical illness experience significant skeletal muscle wasting that may predict clinical outcome. Ultrasound (US) is a noninvasive method that can measure muscle quadriceps muscle layer thickness (QMLT) at the bedside. The aim of this study was to determine the muscle loss assessed by ultrasonography (US) of the quadriceps femoris muscle in critically ill patients on mechanical ventilation and its relationship with hospital outcomes.

Methods: This study involved patients ≥18 years admitted to the intensive care unit who needed mechanical ventilation for at least 48 h. The quadriceps muscle layer thickness (QMLT) in the two-thirds of the thigh was quantified using bedside US. The QMLT of the left and right legs on the first (D1), third (D3), and seventh (D7) days were measured.

Results: US quadriceps thickness measurements were performed in 74 critically ill patients. The mean age was 62.3 ± 19.5 years, 54.1% of the patients were men, with a BMI of 25.5 ± 4.6 kg/m2, SAPS 3 of 55.2 ± 17.2, and NRS of 3.2 ± 1.0. The percentage muscle thickness declined at the right leg in 15% (95%CI, 10.5%-19.4%), and 12.7% (95%CI, 9.1%-16.3%) at the left leg from the first to the seventh day. Receiver operating characteristic showed cutoff value in muscle thickness of ≤1.64 cm on day 7 could predict survival (area under then curve = 0.7; 95% CI, 0.582-0.801). In Cox regression after adjusting, the probability of patients remaining on mechanical ventilation was higher with ≤1.64 cm loss of thigh muscle thickness on day 7; HR = 2.1 (95% CI 1.1-3.8, P = 0.017). The same occurred about ICU survival probability; HR = 3.7 (95% CI 1.2 to 11.5) and hospital survival probability; HR = 4.5 (95% CI 1.5 to 13.7).

Conclusions: The measurement of QMLT using US showed that critically ill patients on mechanical ventilation presented with muscle wasting and greater loss of muscle thickness was associated with worse outcomes.