Energy Requirements in the Post-ICU Period: An Exploratory Multicenter Observational Study

There is limited knowledge about nutritional intake and energy needs during the post-intensive care unit (ICU) period and their relationship with clinical outcomes and physical recovery.

Thus, this observational multicenter study (Azienda Ospedaliero-Universitaria "Santa Maria", Terni and "Madonna del Soccorso" General hospital, San Benedetto del Tronto, Italy) aimed, firstly, to measure energy expenditure via indirect calorimetry (IC) (Q-NRG+^® Metabolic Monitor, Cosmed, Rome, Italy), derived respiratory quotient (R/Q1) and, malnutrition risk via Mini Nutritional Assessment (MNA) test and body composition through bioimpedance vector analysis (BIVA-Akern, Pontassieve, Italy); secondly, to assess their effect on energy needs, body composition and physical rehabilitation steps in critically ill adults after ICU discharge. The provision of nutrients (PIS test) was also recorded. Oral nutritional supplementation was used to reach the optimal nutritional intake. All patients followed a standardized rehabilitation program.

A total of 43 patients were enrolled from January 2024 until February 2025 at the beginning of their post-ICU period. The mean age was 65.7 ± 1.0 years, the mean BMI was 20.73 ± 0.8 kg/m² at the recovery ward, and 60.4% (n = 26) were male. The mean admission period was 19.5 ± 1.7 days. The resting energy expenditure (mREE) was 1591 ± 71.2 at the admission and 1.856 ± 62.7 kcal/kg/d at the discharge (p < 0.05). The median phase angle value was 4.33 ± 0.15 at the admission and 5.05 ± 0.17° at the discharge (p < 0.05); R/Q1 at the admission was 0.7 ± 0.1 and 1.086± 0.11 at the discharge (p < 0.05). Improved energy expenditure significantly correlated with R/Q1 and phase angle (r = 0.81 and r = 0.72, respectively). Interestingly, there was no significant correlation between improved metabolism and improved PIS test scores (r = 0.18). Improved metabolism and nutritional status showed a tendency to correlate with shorter post-ICU courses and earlier physical recovery, without reaching statistical significance.

Measurement of energy expenditure and caloric intake, along with the assessment of body composition is feasible and provides an objective tool to guide and possibly enhance the functional recovery in patients during the post-ICU period.