Nutritional adequacy and accuracy in long-stay critically ill patients as measured by indirect calorimetry

ABSTRACT

Introduction: Nutritional optimisation is recognised as having significant impact on clinical and functional outcomes of critically ill patients.1 Clinical recommendations suggest use of indirect calorimetry guided nutrition in the intensive care unit (ICU),2 and a recent systematic review demonstrated improved outcomes from its use.3 The COVID-19 pandemic has seen a greater proportion of patients with prolonged critical illness, a cohort for whom nutritional optimisation is a key unmet need.4 Objectives: To assess rates of over and underfeeding in a tertiary centre ICU and how these relate to markers of catabolism and persistent critical illness. Methods: Serial measurements of REE (resting energy expenditure) and RQ (respiratory quotient) by indirect calorimetry were performed using Q-NRG+ device (COSMED, Rome, Italy). Nutritional intake and estimations of requirements were recorded concurrently together with routine clinical observations, and markers of critical illness, catabolism and over or underfeeding. Results: Across 30 patients, REE was lower than estimated energy requirements, 24.2 (IQR 20.0-28.1) kcal/ day/kg IBW vs. 29.1(IQR 25.4-33.1) kcal/day/kg IBW, p<0.001. 41.8% of measurements showed overfeeding (actual calorie intake >110% of REE), and 23.3% showed underfeeding (actual calorie intake <85% of REE). Obese patients (n=15) were underfed (-98kcal/day deficit) compared to non-obese patients (n=15), who were on average overfed (+256kcal/day surplus), p=0.021. Overfeeding was also associated with greater length of ICU admission (R2 0.159, p<0.005). Median day of ICU admission in overfed patients was 39 days (IQR 24-56), and in underfed patients 21.5 (IQR 7.5-45.25). However, there was no significant association between calorie surplus or deficit, and other markers of overfeeding PaCO2, insulin use, ureacreatinine-ratio. Conclusion: This service evaluation recorded measurements of REE and RQ in critically ill patients with high lengths of ICU stay (up to 66 days). We observed increased rates of overfeeding with increased duration of ICU admission, and increased overfeeding in non-obese patients.