Effect of Severe Burn Injury on Body Composition and Muscle Metabolism in Pediatric Patients

Abstract

Muscle wasting in burn injury is associated with increased morbidity and mortality. Burn-induced muscle cachexia is partly attributed to lack of physical activity imposed by standard of care. Moreover, evidence supports that muscle tissue is catabolized to provide amino acids necessary for wound healing and production of acute phase proteins. However, there is a paucity of data concerning acute body composition changes in response to burn trauma, or factors that influence burn-induced muscle wasting. The objectives of this dissertation are 1) to quantify the extent of body tissue remodeling and 2) assess the determinants of skeletal muscle protein turnover in children with severe burns. This is a retrospective analysis of data collected prospectively from two cohorts of patients: 24 patients who underwent dual-energy x-ray absorptiometry (DEXA) scans from 2000 to 2016 and 268 patients who underwent metabolic studies from 1999 to 2008. All patients were treated and studied at Shriners Hospitals for Children, Galveston. Tissue remodeling was assessed using two DEXA scans per patient performed within 2 weeks of injury and discharge, respectively. Muscle metabolism kinetic parameters were calculated from mass-spectrometry data generated during a 5-hour stable isotope infusion study. Our key findings were that severely burned children show significant central fat accumulation and reductions in whole-body in lean mass, which were more pronounced in upper relative to lower limps, in the acute period post injury. Patient characteristics such age, sex, weight and burn severity are associated with several parameters of muscle protein metabolism. Specifically, protein turnover was related to time post injury, body mass and sex. Further, muscle protein turnover may have greater contribution to burn-induced hypermetabolism than previously thought. These findings indicate some important directions for future research. Studies are required to examine potential benefits from rehabilitation schemes focusing more on upper extremities and individualized pharmacological/nutritional treatments based on patient characteristics. Finally, stable body weight combined with profound tissue remodeling suggests the need for further research on the understudied field of macronutrient requirements of severely burned children.