Background & aims: Different metabolic phases can be distinguished in critical illness, which influences nutritional treatment. Achieving optimal nutritional treatment during these phases in critically ill patients is challenging. COVID-19 patients seem particularly difficult to feed due to gastrointestinal problems. Our aim was to describe measured resting energy expenditure (mREE) and feeding practices and tolerance during the acute and late phases of critical illness in COVID-19 patients. Methods: Observational study including critically ill mechanically ventilated adult COVID-19 patients. Indirect calorimetry (Q-NRGþ, Cosmed) was used to determine mREE during the acute (day 0e7) and late phase (>day 7) of critical illness. Data on nutritional intake, feeding tolerance and urinary nitrogen loss were collected simultaneously. A paired sample t-test was performed for mREE in both phases. Results: We enrolled 21 patients with a median age of 59 years [44e66], 67% male and median BMI of 31.5 kg/m 2 [25.7e37.8]. Patients were predominantly fed with EN in both phases. No significant difference in mREE was observed between phases (p ¼ 0.529). Sixty-five percent of the patients were hypermetabolic in both phases. Median delivery of energy as percentage of mREE was higher in the late phase (94%) compared to the acute phase (70%) (p ¼ 0.001). Urinary nitrogen losses were significant higher in the late phase (p ¼ 0.003). Conclusion:In both the acute and late phase, the majority of the patients were hypermetabolic and fed enterally. In the acute phase patients were fed hypocaloric whereas in the late phase this was almost normocaloric, conform ESPEN guidelines. No significant difference in mREE was observed between phases. Hypermetabolism in both phases in conjunction with an increasing loss of urinary nitrogen may indicate that COVID-19 patients remain in a prolonged acute, catabolic phase.

Conclusion:We showed lower need of vasopressors and continuous renal replacement therapies during ICU stay with the use of IMN formulas, which may be associated with their modulatory effect over inflammatory response. A higher protein delivery may be provided with IMN formulas in the ICU. References: [1] Braga M., et al. Cliinical evidence for pharmaconutrition in major elective surgery. JPEN. 2013.