Doubly labelled water for determining total energy expenditure in adult critically ill and acute care hospitalised inpatients: a scoping review protocol
Creators: name: Tatucu, Oana
name: Nguo, Kay
name: Lambell, Kate
name: Romero, Lorena
name: Earthman, Carrie
name: Ridley, Emma
Publisher: name: Open Science Framework
Year: 2022
Subjects: subject: Medicine and Health Sciences
subject: Dietetics and Clinical Nutrition

description: Indirect calorimetry is recommended for directing energy delivery in the Intensive Care Unit (ICU) in key clinical guidelines (1, 2). Nonetheless, conduct is limited due to technical exclusions for measurement (fraction of inspired oxygen [FiO2] &gt;50%, positive end-expiratory pressure [PEEP] &gt;12, continuous renal replacement therapy and extracorporeal membrane oxygenation) (3). Furthermore, indirect calorimetry measurements only provide an indication of energy expenditure at one timepoint. As energy expenditure fluctuates during critical illness, single measurements may not be appropriate to extrapolate and use to direct energy delivery (3, 4). In the absence of indirect calorimetry, predictive equations are the most frequently used approach for estimating energy expenditure in clinical practice. However, when compared to indirect calorimetry, predictive equations have been repeatedly shown to be inaccurate in estimating the energy expenditure of critically ill patients (5). The doubly labelled water technique is considered the gold standard for determining total energy expenditure in free-living adults (6). This technique provides a measurement of total energy expenditure over a longer duration (i.e. 1-2 weeks), and thus may enable a better understanding of energy expended throughout the course of critical illness and in the post-ICU setting, a period that may be important for nutrition rehabilitation. Concerns regarding the use of this technique in the ICU have been previously raised (7), nonetheless this information to our knowledge has not been methodically collated and reviewed. A preliminary search for existing scoping and systematic reviews exploring the use of the doubly labelled water technique for determining total energy expenditure was conducted on 12th November 2020. This included searching JBI Evidence Synthesis, PROSPERO, Cochrane Database of Systematic Reviews and MEDLINE (Ovid) which did not generate relevant systematic or scoping reviews specific to the ICU and post-ICU acute care hospital setting. This highlights that at present, there is limited information and guidance on the use of the doubly labelled water method in these settings. The objective of this scoping review is to provide an overview of the available literature utilising the doubly labelled water technique to measure total energy expenditure in the ICU and post-ICU acute care setting. The specific research questions are: (1) What measurement protocols were used when conducting the doubly labelled water technique? (2) Were any barriers encountered when conducting measurements and if so, were any recommendations made by the authorship team to improve the technique? (3) Have any studies validated or compared total energy expenditure measured using doubly labelled water with other methods? If so, how did these measurements compare? Completion of this review will enhance our understanding of the use of this technique for measuring total energy expenditure in the ICU and post-ICU setting. References: 1. Singer P, Blaser AR, Berger MM, Alhazzani W, Calder PC, Casaer MP, et al. ESPEN guideline on clinical nutrition in the intensive care unit. Clin Nutr. 2019;38(1):48-79. 2. McClave SA, Taylor BE, Martindale RG, Warren MM, Johnson DR, Braunschweig C, et al. Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr. 2016;40(2):159- 211. 3. Delsoglio M, Achamrah N, Berger MM, Pichard C. Indirect Calorimetry in Clinical Practice. J Clin Med. 2019;8(9). 4. Frankenfield DC, Ashcraft CM, Galvan DA. Longitudinal Prediction of Metabolic Rate in Critically Ill Patients. Journal of Parenteral and Enteral Nutrition. 2012;36(6):700-12. 5. Tatucu-Babet OA, Ridley EJ, Tierney AC. Prevalence of Underprescription or Overprescription of Energy Needs in Critically Ill Mechanically Ventilated Adults as Determined by Indirect Calorimetry: A Systematic Literature Review. JPEN J Parenter Enteral Nutr. 2016;40(2):212-25. 6. Westerterp KR. Doubly labelled water assessment of energy expenditure: principle, practice, and promise. Eur J Appl Physiol. 2017;117(7):1277-85. 7. Plank LD, Hill GL. Energy balance in critical illness. Proceedings of the Nutrition Society. 2003;62(2):545-52.