Thermogenic response to feeding in severely burned patients: relation to resting metabolic rate

Energy expenditure (EE) was measured one to five times by indirect calorimetry for 1 h after an overnight fast, and for 2 h after starting feeding in 19 severely burned patients (TBSA > 20 per cent) for a total of 36 tests. Twelve tube-fed volunteers served as controls. Thermogenic response to feeding (TRF) was calculated as the percentage of energy intake and hypermetabolism as the percentage of values obtained with the Harris-Benedict formula (%HB). Measured energy expenditure values were compared with values given by three predicting formulae. TRF was present in 10 out of the 33 measurements. Fasting EE was not different between the tests with and without TRF, but %HB was different between the two groups: 121.1 +/- 25.8 vs 157.8 +/- 32.0 per cent (tests with and without TRF, respectively (P < 0.01)). TRF was always absent when %HB was higher than 50. When TRF was present it was not statistically different from the control values. None of the three predicting formulae gave values within 10 per cent of the measured values in more than 25 per cent of the patients. We conclude that TRF is suppressed in burned patients with marked hypermetabolism, and that EE measured in the fed state reflects resting expenditure accurately in these patients. In addition, EE cannot be predicted from existing formulae.