Two‐hour indirect calorimetry measurement as a predictor of 24‐hour energy expenditure in critically ill surgical patients: A longitudinal study

Background Measuring energy expenditure (EE) by indirect calorimetry (IC) has become the gold standard tool for critically ill patients to define energy targets and tailor nutrition. Debate remains as to the optimal duration of measurements or the optimal time of day in which to perform IC. Methods In this retrospective longitudinal study, we analyzed results of daily continuous IC in 270 mechanically ventilated, critically ill patients admitted to the surgical intensive care unit in a tertiary medical center and compared measurements performed at different hours of the day. Results A total of 51,448 IC hours was recorded, with an average 24‐h EE of 1523 ± 443 kcal/day. Night shift (00:00–8:00) was found to have significantly lower EE measurements (mean, 1499 ± 439 kcal/day) than afternoon (16:00–00:00; mean, 1526 ± 435 kcal/day) and morning (8:00–16:00; mean, 1539 ± 462 kcal/day) measurements (P