Ultrasound for the Assessment of Peripheral Skeletal Muscle Architecture in Critical Illness: A Systematic Review

Objectives: To critically evaluate and summarize identified evidence for the use of ultrasound to measure peripheral skeletal muscle architecture during critical illness. Data Sources: Seven electronic databases (Medline, Cumulative Index to Nursing and Allied Health Literature, Cochrane Library, Physiotherapy Evidence Database, Scopus, Excerpta Medica Database, and Web of Science [including Science Citations and Conference Proceedings]) and personal libraries were searched for relevant articles. Cross-referencing further identified references. Study Selection: Quantitative study designs excluding abstracts, published in English, including adult critically ill patients in the ICU, evaluating peripheral skeletal muscle architecture during critical illness with ultrasound were included. Studies using ultrasonographic muscle data as outcome measures in interventional trials were excluded. Data Extraction: Performed by one reviewer using a standardized data extraction form and cross-checked by a second reviewer. Quality appraisal was undertaken by two independent reviewers-studies were classified, graded, and appraised according to standardized algorithms and checklists. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were adhered to. Data Synthesis: Seven studies with independent patient cohorts totaling 300 participants were included. One study adopted a case-control design, and the remainder were case series. Ultrasound data demonstrated deficits in a variety of peripheral skeletal muscle architecture variables across a range of muscle groups associated with critical illness. Ultrasound offered more accurate data compared to limb circumference measurement and has excellent reported reliability, but underestimated data acquired via more invasive muscle biopsy. Conclusion: Ultrasound provides clinical utility for assessing the trajectory of change in peripheral skeletal muscle architecture during critical illness, supplementing more detailed characterization, albeit rarely used, from muscle biopsy analysis. Adoption of standardized operating protocols for measurement will facilitate future meta-analysis of data.