Clinical comparison of three methods to determine resting energy expenditure

An accurate and reliable method of determining resting energy expenditure in the critical care setting is crucial because inadequate caloric intake and excessive caloric intake are both associated with a number of complications. Energy requirements were determined by three different methods in a group of 25 post-cardiac surgery patients in the intensive care unit. Patients were intubated and had a thermodilution pulmonary artery catheter in place. The first method measured resting energy expenditure by indirect calorimetry. For the second method, the results of blood gases drawn at the same time that indirect calorimetry was measured were used in the Fick equation. In the third method, a registered dietitian assessed each patient by using the Harris-Benedict equation with stress factor modification. Indirect calorimetry was considered the standard with which the other two methods were compared. The results showed that, compared with calorimetry, both the Fick equation and the Harris-Benedict equation underestimated resting energy needs. Statistically, only the difference between the Fick equation method and indirect calorimetry was significant. Clinically, however, both methods seem to have applicability.