Muscle weakness and wasting in pediatric critical illness

: Muscle weakness and wasting is increasingly recognized as a problem in children admitted to the pediatric intensive care unit (PICU). Muscle weakness and wasting could potentially affect a child’s function and development, imposing a burden on the child and their families. We aimed to summarize the literature on muscle weakness and wasting in critically ill children, discuss methods to measure muscle changes as well as areas for future research. Intensive care unit weakness in children has been reported through numerous case reports and a cohort study. These papers demonstrated that muscle weakness can be persistent in critically ill children, with reduced strength reported even after hospital discharge. A prevalence of approximately 2% has been reported in critically ill children, lower than that reported in adults. This may be related to an under-detection of muscle weakness in critically ill children, as identification of muscle weakness and wasting in critically ill children can be challenging. Some methods that have been used to assess muscle changes in critically ill children include arm muscle circumference derived from triceps skinfold thickness and upper-arm circumference, ultrasound-derived limb and diaphragm muscle size, lean body mass from bioelectrical impedance analysis. Using these methods, various patterns have been reported including increase, decrease and no change in muscle. However, studies have not explored the relationship between muscle changes and function. Evidence suggests that there is heterogeneity in the muscle changes that critically ill children may experience. Future research may need to consider differences in age, illness severity and body composition in interpreting changes in muscle size and strength in critically ill children. Importantly, understanding the role of nutrition and physical rehabilitation in relation to muscle changes and function is an important direction in optimizing long-term outcomes in critically ill children.