Calculation versus measurement of total energy expenditure

Abstract

In acutely ill patients both hypo- and hyperalimentation must be avoided by adjusting caloric intake to total energy expenditure (TEE). We determined the discrepancy between basal energy expenditure (BEE) calculated from the basic Harris-Benedict formula and TEE measured by continuous indirect calorimetry in a heterogeneous group of mechanically ventilated surgical patients. We also compared the accuracy of TEE calculated from the corrected Harris-Benedict formula or estimated by intermittent indirect calorimetry to that of TEE measured by continuous indirect calorimetry. The poor correlation between calculated BEE and measured TEE was significantly (p < .05) improved by a correction factor based on each patient's clinical condition. The mean absolute difference between calculated TEE and measured TEE was 8.9 ± 9.6 (SD) %. Calculations were significantly (p < .05) improved by estimating TEE from two 5-min recording periods, which suggests that continuous indirect calorimetry may not always be necessary to guide caloric replacement.