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/m², 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/m². Utilising IC-directed nutrition therapy in intensive care units could help in delivering personalised caloric intake, reducing the risks of underfeeding or overfeeding.