Dynamics of energy expenditure in severe traumatic brain injury during intensive care: the influence of infection and sedation

Aim : To investigate the dynamics of energy expenditure in patients with severe traumatic brain injury (TBI) during an intensive care unit (ICU) stay and to assess the effects of infection, sedation, sedation depth, and neurological status. Materials and methods : This prospective observational study was conducted in the ICU of St. George University Hospital in Plovdiv over 18 months. Thirty patients with severe TBI were included. Measured resting energy expenditure (mREE) was assessed using indirect calorimetry (Q-NRG+, Cosmed). Metabolic status was defined using the energy metabolic index, expressed as a percentage of Harris–Benedict predicted energy expenditure. Results : The measured REE increased progressively during ICU stay, reaching peak values between days 11 and 20 (31.08±4.61 kcal/kg/day; 115±15%), followed by a moderate decline while remaining above predicted levels. Marked interindividual variability was observed, with hypo-, normo-, and hypermetabolic states throughout all periods. Energy expenditure was significantly higher during infection compared to non-infectious periods (111±23% vs. 103±21%, p =0.037). Sedation was associated with lower energy expenditure (103±20% vs. 111±25%, p =0.041), with a significant inverse relationship between sedation depth and metabolic rate ( p <0.001). Neurological status and inflammatory markers showed no significant association with metabolic status. Conclusions : Energy expenditure in severe TBI is dynamic and highly variable during an ICU stay. Infection increases metabolic demand, whereas sedation reduces metabolic rate in a dose-dependent manner. These findings support individualized metabolic monitoring to optimize nutritional management.