Evaluation of Bedside Methods to Measure Muscularity in Critically Ill Patients

Muscle wasting is a significant problem in critically ill patients, with reported losses of a half to three percent per day over the first ten days (for an average 70kg person this equates to 3 to 20kg of muscle loss). Low skeletal muscle mass at admission to the intensive care unit (ICU) and the loss of lean tissue have been associated with negative clinical outcomes, including increased incidence of infections, length of stay, mortality and muscle weakness. It is therefore crucial that technology is utilised to: 1) identify ICU patients with low muscularity on admission, 2) to help understand the factors impacting muscle loss and to 3) assess the effectiveness of interventions aimed at maintaining skeletal muscle mass in this population.

The measurement of lean body mass in patients admitted to the ICU is challenging however, due to the large fluid shifts that occur in this population and logistical issues in moving patients to specialised machinery for body composition analysis. Currently, there is no validated method for accurately assessing a patient's muscle mass at the bedside in the intensive care setting. It is therefore important to investigate the accuracy, feasibility and reliability of bedside methods such as subjective physical assessment of muscle mass, mid arm muscle circumference, ultrasound and bioimpedance analysis to assess muscularity in this population who are primarily bedbound. In order to do this, a critical comparison is required between these methods and muscularity assessed by a "reference" body composition method, such computed tomography (CT) image analysis. Briefly, quantification of skeletal muscle at the abdomen area utilising abdominal CT images has been shown to be highly representative of whole body skeletal muscle volume.

We wish to conduct a pilot, feasibility study (n= 50), which will recruit patients who have a CT scan (containing abdomen area), performed for clinical purposes. Our primary aim will be to investigate whether muscularity assessed with non-invasive bedside methods (ultrasound, bioimpedance analysis, SGA physical assessment, mid arm muscle circumference) are correlated with skeletal muscle mass quantified by a "reference method" (CT image analysis).