Comparison between resting energy expenditure measured by indirect calorimetry and metabolic rate estimate based on Harris-Benedict equation in septic patients

Background: Providing an adequate caloric intake is essential for improving clinical outcomes, because inadequate nutrition induces several problems. Previous studies have shown that energy expenditure calculated by classical prediction equations, such as the Harris-Benedict equation (HBE), is greater than the measured resting energy expenditure (REE). To compensate for this discrepancy, additional factors, such as a stress factor, are often used to rescale the value. However, the numerical value of the stress factor, particularly in septic patients, is unknown. Indirect calorimetry (IC) enables to the real-time measurement of REE at the bedside. We hypothesized that the stress factor could decrease over the time course of recovery in septic patients. To test this hypothesis, we measured the REE of septic patients hospitalized in our ICU throughout their intubation period. Methods: This single-center retrospective study was conducted to compare resting REE measured by IC and the estimated energy expenditure in adult septic patients. Basal metabolic rate (BMR) was estimated by the HBE. Chronological changes in the ratio of measured REE to BMR were analyzed to estimate the stress factor. Results: A total of 47 patients with sepsis were included in this study. We found that REE/BMR in the septic patients was in the range of 1.07 to 1.11. Moreover, the estimated stress factor did not change over time during the intubation period. REE/BMR did not depend on the number of sedatives administered. Both sequential organ failure assessment (SOFA) scores and blood concentrations of C-reactive protein (CRP) decreased over time. Respiratory quotient (RQ) on the last intubation day was greater than that on the first day. Conclusions: The REE measured by IC in sedated septic patients was approximately 1.1 times greater than BMR. The ratio of measured REE to BMR does not change with resolution of the illness. This result was likely caused by the concomitant increase in energy intake and improvement in patient general condition at this time. These findings may contribute to better nutrition control in ICU-admitted septic patients. Correspondence to: Dr. Tomonori Takazawa, Intensive Care Unit, Gunma University Hospital, Japan, Tel: +81-27-220-8693; Fax: +81-27-220-8692; E-mail: [email protected]