Factors influencing energy expenditure in patients with burns.

Twenty-three consecutive patients with a mean burn size of 39% of total body surface area (%TBSA) were studied prospectively. Expected basal energy expenditure (EBEE) calculated by the Harris-Benedict formula, initial and twice weekly measurements of energy expenditure (MEE) by indirect calorimetry, and simultaneous estimation of nutrient intake were obtained. In the whole cohort the EBEE was 1,715 +/- 24 kcal/day and the MEE was 2,218 +/- 59 kcal/day. The degree of hypermetabolism was 29.0 +/- 2.8%. A subgroup of 16 patients had metabolic rates measured in both the fed and unfed states. The degree of hypermetabolism was only 6.5 +/- 4.5% in the unfed, but increased to 34.1 +/- 3.2% when the same patients were fed (p less than 0.001). The factors affecting MEE were then evaluated by stepwise multiple regression analysis which showed that MEE = -4343 + (10.5 X %TBSA) + (0.23 X Caloric intake [CI]) + (0.84 X EBEE) + (114 X Temp [C]) - (4.5 X Postburn days), r = 0.82, p less than .001. We conclude that 25% of the CI is used to increase the MEE, which suggests that these measurements done in the fasting state cannot be used to predict requirements.