Energy Expenditure Measured by Indirect Calorimetry in a Neuroscience Intensive Care Unit: a Retrospective Observational Study

Objectives: To compare indirect calorimetry (IC) readings with the Harris-Benedict equation (HBE) predictions of resting energy expenditure (REE) in intubated acute brain-injured patients in a tertiary hospital's Neuroscience Intensive Care Unit (ICU). Design: A single-centre, retrospective study. Setting: Neuroscience Intensive Care Unit at a tertiary hospital. Subjects: All adult patients admitted to the Neuroscience Intensive Care Unit between June 1, 2020, and June 30, 2021, who had an IC reading. Outcome measures: Comparison of the measured REE using IC and the predicted REE using the HBE modified for critically ill adults. Subgroup analysis based on body mass index (BMI) was also performed. Results: A total of 108 patients had IC readings taken during the study period. There was a significant difference between the REE predicted by the HBE and the measured IC readings, with a mean difference of 465.3 kcal (95% CI 408.1-522.5, p = 0.001). A moderate positive correlation was observed (coefficient r = 0.565, p < 0.001). In patients with BMI >= 30 kg/m(2), the HBE significantly overestimated REE compared with IC readings (p = 0.005). Conclusions: The Harris-Benedict equation tends to overestimate resting energy expenditure, especially in acute brain-injured patients with a BMI >= 30 kg/m(2). Utilising IC-directed nutrition therapy in intensive care units could help in delivering personalised caloric intake, reducing the risks of underfeeding or overfeeding.