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

Indirect calorimetry is a useful method to determine how much energy critically ill patients need while in the Intensive Care Unit (ICU). However, there is limited information on how energy needs change during the different stages of critical illness in large groups of patients.

This study analyzed energy use in adult ICU patients overall and during the early, late, and recovery phases of their illness. Data was collected from January 2010 to July 2019 using indirect calorimetry measurements from a mixed ICU.

Energy expenditure was measured in calories per day and calories per kilogram of body weight per day, and compared to predicted basic energy needs. The study included 629 patients with 863 measurements; their average age was 48 years, most were men, and a significant portion had traumatic brain injuries. On average, patients used about 2,263 calories per day, which was 135% higher than expected based on basic metabolic rates.

For patients who were measured multiple times, energy use increased over time, from about 27 calories per kilogram in the early phase, to 30 in the late phase, and 31 in the recovery phase. These findings show that energy needs in ICU patients are significantly higher than normal and tend to rise as they progress through the stages of critical illness.