Measured energy expenditure according to the phases of critical illness: A descriptive cohort study

Background: Indirect calorimetry is recommended for directing energy provision in the intensive care unit (ICU). However, limited reports exist of measured energy expenditure according to the phases of critical illness in large cohorts of patients during ICU admission. This study aimed to analyze measured energy expenditure overall in adult patients who were critically ill and across the different phases of critical illness.

Methods: Indirect calorimetry measurements completed at a mixed ICU between January 2010 and July 2019 were eligible. Measured energy expenditure was analyzed and reported as kcal/day and kcal/kg/day overall, as the percentage increase above predicted basal metabolic rate and according to the phases of critical illness; acute early (day 1-2), acute late (day 3-7) and recovery (>7 days) phases using mixed effects linear modelling.

Results: There were 629 patients with 863 measurements included; age mean (standard deviation) 48 (18) years, 68% male and 269 (43%) with a traumatic brain injury. Measured energy expenditure overall was 2263 (626) kcal/day (30 (7) kcal/kg/day), which corresponded to a median [interquartile range] of 135 [117-155] % increase above predicted basal metabolic rate. In patients with repeat measurements (n = 158), measured energy expenditure (mean ± standard error) increased over time; 27 ± 0.5 kcal/kg/day in the early acute, 30 ± 0.4 kcal/kg/day in the late acute, and 31 ± 0.4 kcal/kg/day in the recovery phases of critical illness (P < 0.001).

Conclusion: In a large cohort of ICU patients, measured energy expenditure was 135% above the basal metabolic rate and increased from the early acute to the late acute and recovery phases of critical illness.