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

OBJECTIVE

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.

DESIGN

Cohort study.

SETTING

Burn unit of an adult hospital.

PATIENTS

Twenty clinically stable burn patients undergoing mechanical ventilation with 36.7 +/- 4.2 total % burn surface area.

INTERVENTIONS

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.

RESULTS

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%.

CONCLUSIONS

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.