Throwing darts in ICU: how close are we in estimating energy requirements?

Abstract

BackgroundIndirect calorimetry (IC) is the gold standard for determining energy requirement. Due to lack of availability in many institutions, predictive equations are used to estimate energy requirements. The purpose of this study is to determine the accuracy of predictive equations (ie, Harris-Benedict equation (HBE), Mifflin-St Jeor equation (MSJ), and Penn State University equation (PSU)) used to determine energy needs for critically ill, ventilated patients compared with measured resting energy expenditure (mREE).MethodsThe researchers examined data routinely collected as part of clinical care for patients within intensive care units (ICUs). The final sample consisted of 68 patients. All studies were recorded during a single inpatient stay within an ICU.ResultsPatients, on average, had an mREE of 33.9 kcal/kg using IC. The estimated energy requirement when using predictive equations was 24.8 kcal/kg (HBE×1.25), 24.0 kcal/kg (MSJ×1.25), and 26.8 kcal/kg (PSU).DiscussionThis study identified significant differences between mREE and commonly used predictive equations in the ICU.Level of evidenceIII.

Comparison of predictive equations and indirect calorimetry in critical care: Does the accuracy differ by body mass index classification?

“…A historical sample from 2007 to 2009 that included 352 ICUs reported that nearly 0.5% of the cohort received an IC measurement 14 . Even with IC being available, the timing, accuracy, and ability to perform a study can be impacted by the cost of equipment, availability of properly trained personnel for maintenance and interpretation (eg, respiratory therapists, RDNs), and equipment appropriateness and calibration (eg, air leaks, anesthesia administration, certain ventilator settings) 3,5,15,16 . In addition to these factors, many individuals may not be eligible for IC.…”

“…The authors did suggest that with the paucity of data on energy needs in the ICU, a moderate, weak recommendation that nutrition support dosing should fall within 12 and 25 kcal/kg in the first 7-10 days of an ICU admission was included. Additional research has begun to explore the relationship between predictive equations and IC in various populations, including patients in trauma, surgical, medical, and cardiac ICUs, [5][6][7][8] but the heterogeneity of metabolic derangements seen in critically ill patients and variable study designs have left this question unanswered and under debate. 9,10 This heterogeneity during times of acute illness results from a hypermetabolic and catabolic environment that increases overall caloric needs.…”

“…14 Even with IC being available, the timing, accuracy, and ability to perform a study can be impacted by the cost of equipment, availability of properly trained personnel for maintenance and interpretation (eg, respiratory therapists, RDNs), and equipment appropriateness and calibration (eg, air leaks, anesthesia administration, certain ventilator settings). 3,5,15,16 In addition to these factors, many individuals may not be eligible for IC. Furthermore, repeat measures are often needed to understand the metabolic changes that occur over the course of an ICU admission.…”