Prevalence and magnitude of muscle loss in the pediatric intensive care unit assessed by ultrasound: a systematic review and meta-analysis.

OBJECTIVE: To systematically review and quantify the variation in quadriceps femoris muscle thickness in children admitted to pediatric intensive care units (PICUs) and to identify factors associated with this loss. METHODS: Searches were performed in Cochrane Library, Embase, PubMed, Scopus, and Web of Science databases for studies published without date restrictions. Observational studies assessing quadriceps thickness via ultrasonography at a minimum of two time points during PICU stay were included. The study protocol was registered in PROSPERO (CRD42024628869). Following PRISMA guidelines, data were extracted regarding study characteristics, muscle thickness variations, and associated clinical/demographic factors. Quantitative synthesis utilized random-effects models for percentage change and meta-analysis of proportions for prevalence. RESULTS: Nine studies (n = 536 patients) were included. The mean reduction in muscle thickness at 7 days was -7.89% (95% CI, -11.36% to -4.41%; p < 0.001). The maximum observed loss during admission was -10.77% (95% CI, -12.87% to -8.67%; p < 0.001). The pooled prevalence of clinically significant atrophy (> 10%) was 49.4% (95% CI, 44.0% to 54.7%). Key factors associated with greater loss included the use of neuromuscular blocking agents, older age (older children vs. infants), and cumulative protein and caloric deficits. CONCLUSIONS: Muscle atrophy in critically ill children is an early, severe, and multifactorial phenomenon, affecting nearly half of the patients. Bedside ultrasonography monitoring is essential to guide early interventions and mitigate long-term functional impairment.