Determining energy needs in critically ill patients: Equations or indirect calorimeters

PURPOSE OF REVIEW: The review focuses on current methodology for the most accurate way to determine resting metabolic rate in critically ill patients and to evaluate whether application of any particular method improves clinical outcome. RECENT FINDINGS: Consensus is that indirect calorimetry is the most accurate method for determining resting metabolic rate. Whenever an alternate method of determining energy expenditure is tested (e.g. equations), the criterion method used in the validation is indirect calorimetry. Of the alternates to indirect calorimetry, the Penn State equation has the strongest validation work supporting it. No study has been undertaken to determine whether the drop in accuracy associated with estimation methods translates into deterioration in clinical outcome compared to nutrition support guided by measurements. SUMMARY: Indirect calorimetry is the most accurate way to determine calorie needs in critically ill patients. Compared to indirect calorimetry, metabolic rate equations are accurate about 75% of the time. No study has been performed to determine whether the measurement or estimation method improves clinical outcome.