Continuous measurement of energy expenditure in ventilated burn patients: an analysis.

Abstract

To predict the daily total energy expenditure of ventilated burn patients, this study was designed to determine the contribution of different activities on energy expenditure over a 24-hr period. Cohort study. Burn unit of an adult hospital. Twenty clinically stable burn patients undergoing mechanical ventilation with 36.7 +/- 4.2 total % burn surface area. Patients were fed according to a previously validated equation which takes into account the Harris-Benedict equation, % burn surface area, caloric intake, body temperature, and the number of postburn days: Toronto Formula = -4343 + (10.5 x % burn surface area) + (0.23 x caloric intake) + (0.84 x Harris-Benedict equation) + (114 x body temperature) - (4.5 x postburn days). The total energy expenditure of patients was measured by indirect calorimetry and their activity levels were recorded over a 24-hr period. The calculated Toronto Formula was 2191 +/- 83 kcal/day and patients were fed 2276 +/- 40 kcal/day. The measured resting energy expenditure was 2149 +/- 102 kcal/day and was similar to the Toronto Formula (NS). The total energy expenditure was 2492 +/- 120 kcal/day. Altogether the activities contributed 27.3 +/- 1.3% to the total energy expenditure and did not correlate with the % burn surface area. The activity factor calculated as [total energy expenditure less resting energy expenditure] x 100/resting energy expenditure was 16.6 +/- 2.4% and calculated as [total energy expenditure less Toronto Formula]/Toronto Formula was 14.5 +/- 4.3%. These results suggest that in clinically stable, mechanically ventilated burn patients, the Toronto Formula accurately predicts the resting energy expenditure and that the Toronto Formula or the resting energy expenditure x 1.2 can be used to estimate the total daily energy requirements.