Background: Understanding the changes in energy expenditure and body composition is essential for the optimal management of the critically injured, yet these changes have not been quantified within the current context of trauma care.
Methods: Ten critically injured patients (median Injury Severity Score = 35) had measurements of energy expenditure and body composition as soon as they were hemodynamically stable and then every 5 days for 21 days.
Results: Resting energy expenditure rose to 55% above predicted and remained elevated throughout the study period. Total energy expenditure was 1.32 X resting energy expenditure. Body fat was oxidized when energy intake was insufficient (r=-0.830, p<0.02). Body water changes closely paralleled body weight changes and were largely accounted for by changes in extracellular water. Over the 21-day study period, there was a loss of 1.62 kg (16%) of total body protein (p<0.0002), of which 1.09 kg (67%) came from skeletal muscle. Intracellular potassium was low (133 +/- 3 mmol/L, p<0.02) but did not deteriorate further after hemodynamic stability had been reached.
Conclusions: These results show that the period of hypermetabolism lasts longer and the protein loss is greater in critically injured patients than previously thought. Most, but not all, the protein is lost from muscle. Fat loss can be prevented and cell composition preserved once hemodynamic stability is achieved.