Comparison of measured and predicted energy expenditure in mechanically ventilated children

Objective: To determine the energy requirements in mechanically ventilated pediatric patients using indirect calorimetry and to compare the results with the predicted metabolic rate. Design: In 50 mechanically ventilated children with a moderate severity of illness, energy expenditure was measured by indirect calorimetry. Daily caloric intake was recorded for all patients. Total urinary nitrogen excretion was determined in 31 patients. Results: Although there was a close correlation between the measured total energy expenditure (mTEE) and the predicted basal metabolic rate (pBMR) (r = 0.93, p < 0.001), Bland–Altman analysis showed lack of agreement between individual mTEE and pBMR values. The ratio of caloric intake/mTEE was significantly higher in the patients with a positive nitrogen balance (1.4 ± 0.07) compared with those with a negative nitrogen balance (0.8 ± 0.1; p < 0.001). Conclusions: Standard prediction equations are not appropriate to calculate the energy needs of critically ill, mechanically ventilated children. Individual measurements of energy expenditure and respiratory quotient by means of indirect calorimetry in combination with nitrogen balance are necessary for matching adequate nutritional support. Received: 27 June 1997 Accepted: 12 February 1998