Best Practices for Determining Resting Energy Expenditure in Critically Ill Adults

Abstract

Indirect calorimetry (IC) is the gold standard for measuring resting energy expenditure (REE) in the critically ill patient. The use of predictive equations to develop nutrition regimens can be problematic in the critical care setting, because the effects that disease, injury, and stress have on REE are often varied and unpredictable. IC testing ensures that the specific conditions of the critically ill patient are taken into account, thereby preventing potential complications from over- and underfeeding. The clinical indications for and appropriate applications of IC testing are discussed. In addition, 3 case studies are presented that highlight the application of IC. The clinician can face numerous obstacles in implementing IC testing, including lack of equipment, staff shortages, and lack of knowledge regarding application and interpretation of the IC study. Recommendations for addressing these challenges are discussed. In addition, guidelines on ordering and interpreting the IC study are provided. Best practices for predictive equations in critically and acutely ill patients are also presented, since IC testing is not feasible in certain situations. Given the importance of predicting REE in the critically ill patient, it is paramount that more healthcare professionals incorporate IC testing into practice. A multidisciplinary approach is helpful in developing a well-established clinical practice. Nutrition support clinicians can promote optimal nutrition management by being well-informed and able to provide evidence-based recommendations for the use of IC.

Harris-Benedict Equation and Resting Energy Expenditure Estimates in Critically Ill Ventilator Patients

“…[21][22][23][24] Many researchers have stated that the diffi culty in measuring REE accurately often culminates in inadequate nutritional intervention; that is, the daily calorie requirement is either underestimated or overestimated. 24,25 Provision of insuffi cient energy to critically ill patients can result in loss of muscle mass and signifi cant elimination of nitrogen in the urine, which rapidly deteriorates the patient's health and nutritional status. On the other hand, the excessive provision can result in other situations, such as hypercapnia and infectious complications.…”

Inflammation, negative nitrogen balance, and outcome after aneurysmal subarachnoid hemorrhage

“…The metabolic rate after injury was associated with younger age and male sex, both factors that are well known to impact the REE across all acute and chronic illnesses. 23,24 We additionally identified an independent relationship between 2 measures of severity of SAH, the Hunt Hess score 21 and modified Fisher grade, 22 and metabolic rate. It is likely that this relationship is mediated by a surge of catecholamines and release of proinflammatory cytokines that occurs at the time of injury, [25][26][27] and we did find a modest correlation between CRP and TTR levels with both grading scales.…”

Daily variability of resting energy expenditure in acute kidney injury patients on dialysis

“…4 However, many factors can alter the EE in ICU patients, such as pain, medications, body temperature, diet, heart rate, among others. 5 In addition to these factors, patients with severe AKI may also have an altered EE due to loss of kidney homeostasis and the adverse effects of the chosen RRT. 1,3 Thus, only one EE measure alone may not characterize the patient's correct energy needs.…”

“…9 However, in this study, IC was performed in patients during RRT and IC guidelines contraindicate this moment for the measurement of EE, due to possible interferences of the dialysis procedure in gas exchange, which would lead to errors in the measurement of EE using IC. 5,10,11 The present study aims to evaluate the daily variability of REE measured by IC in patients with AKI and dialytic indication and to identify the clinical variables associated with REE.…”