Energy expenditure and indirect calorimetry in critical illness and convalescence: current evidence and practical considerations

Abstract

The use of indirect calorimetry is strongly recommended to guide nutrition therapy in critically ill patients, preventing the detrimental effects of under- and overfeeding. However, the course of energy expenditure is complex, and clinical studies on indirect calorimetry during critical illness and convalescence are scarce. Energy expenditure is influenced by many individual and iatrogenic factors and different metabolic phases of critical illness and convalescence. In the first days, energy production from endogenous sources appears to be increased due to a catabolic state and is likely near-sufficient to meet energy requirements. Full nutrition support in this phase may lead to overfeeding as exogenous nutrition cannot abolish this endogenous energy production, and mitochondria are unable to process the excess substrate. However, energy expenditure is reported to increase hereafter and is still shown to be elevated 3 weeks after ICU admission, when endogenous energy production is reduced, and exogenous nutrition support is indispensable. Indirect calorimetry is the gold standard for bedside calculation of energy expenditure. However, the superiority of IC-guided nutritional therapy has not yet been unequivocally proven in clinical trials and many practical aspects and pitfalls should be taken into account when measuring energy expenditure in critically ill patients. Furthermore, the contribution of endogenously produced energy cannot be measured. Nevertheless, routine use of indirect calorimetry to aid personalized nutrition has strong potential to improve nutritional status and consequently, the long-term outcome of critically ill patients.

Prolonged progressive hypermetabolism during COVID-19 hospitalization undetected by common predictive energy equations

“…In a separate model, an initial hypermetabolic response described as the systemic inflammatory response syndrome (SIRS) occurs first peaking early within days, followed by a subsequent opposing hypometabolic compensatory antiinflammatory response syndrome (CARS), which serves to reverse the changes in REE and hasten the return to normometabolism [28]. In yet a third model, the persistent inflammation catabolism syndrome (PICS), where the SIRS/CARS responses occur simultaneously early after the initial insult, peaking within the first week, but failing to return to baseline or normometabolism by 14 days [28,29].…”

Development of a Resting Energy Expenditure Estimation in Patients Undergoing Targeted Temperature Management with a Surface Gel Pad Temperature Modulating Device

“…Understanding a patient's REE in the critical care setting is important to accurately provide nutritional support and avoid the sequelae of malnutrition (Moonen et al, 2021). Measurement of REE by IDC is considered the gold standard but is cumbersome and often not performed given numerous estimating equations have been shown to accurately predict REE (Wichansawakun et al, 2015).…”

Modeling Energy Expenditure Estimation in Occupational Context by Actigraphy: A Multi Regression Mixed-Effects Model

“…On the other hand, the methods proposed in the expertise approach [ 79 ] are more accurate but are neither practical nor very appropriate for field studies, besides being expensive for specific situations. In the case of the double watermarked method, the standard presents only the principle of the method.…”

“…However, these details are not mentioned. Considering direct calorimetry, one of the main drawbacks is the difficulty or impossibility of the portability of the equipment for field studies and the high cost [ 48 , 79 ]. Although the improvements of estimation methods increased with technological advances, further studies to explore the causal relationships of energy expenditure variables in the occupational context are more complex than the movement execution analysis.…”

“…From ISO 8996:2004 [ 10 ], we applied estimation methods by the relationship with heart rate and by indirect calorimetry. As a gold standard measurement [ 76 , 79 ], results from the indirect calorimetry were compared to energy expenditure estimation of all other methods to identify the suitable technique in occupational settings. In addition, two of the equations found in the literature were also applied, and the two estimation models were developed by hierarchical mixed regression.…”