Accuracy of predictive methods to estimate resting energy expenditure of thermally-injured patients

Abstract

BACKGROUND: The purpose of this study was to evaluate the bias and precision of 46 methods published from 1953 to 2000 for estimating resting energy expenditure (REE) of thermally injured patients. METHODS: Twenty-four adult patients with > or =20% body surface area burn admitted to a burn center who required specialized nutrition support and who had their REE measured via indirect calorimetry (IC) were evaluated. Patients with morbid obesity, human immunovirus, malignancy, pregnancy, hepatic or renal failure, neuromuscular paralysis, or those requiring a FiO2 >50% or positive end expiratory pressure (PEEP) > or =10 cm H2O were excluded. One steady-state measured REE measurement (MEE) was obtained per patient. The methods of Sheiner and Beal were used to assess bias and precision of these methods. The formulas were considered unbiased if the 95% confidence interval (CI) for the error (kilocalories per day) intersected 0 and were considered precise if the 95% CI for the absolute error (%) was within 15% of MEE. RESULTS: MEE was 2780+/-567 kcal/d or 158%+/-34% of the Harris Benedict equations. None of the methods was precise (< or =15% CI error). Over one-half (57%) of the 46 methods had a 95% confidence interval error >30% of the MEE. Forty-eight percent of the methods were unbiased, 33% were biased toward overpredicting MEE, and 19% consistently underpredicted MEE. The pre-1980s methods more frequently overpredicted MEE compared with the 1990 to 2000 (p < .01) and 1980 to 1989 (p < .05) published methods, respectively. The most precise unbiased methods for estimating MEE were those of Milner (1994) at a mean error of 16% (CI of 10% to 22%), Zawacki (1970) with a mean error of 16% (CI of 9% to 23%), and Xie (1993) at a mean error of 18% (CI of 12% to 24%). The "conventional 1.5 times the Harris Benedict equations" was also unbiased and had a mean error of 19% (CI of 9% to 29%). CONCLUSIONS: Thermally injured patients are variably hypermetabolic and energy expenditure cannot be precisely predicted. If IC is not available, the most precise, unbiased methods were those of Milner (1994), Zawacki (1970), and Xie (1993).

Forty-six methods obtained from the literature for estimating energy expenditure in thermal injury were evaluated for bias and precision in 24 thermally injured adults requiring specialized nutrition support. None of the methods was precise as defined by a confidence interval for error ≤15%. One-third of the methods were biased toward overpredicting measured energy expenditure. In the event indirect calorimetry is not available, the most precise unbiased methods were identified.