ASSESSMENT OF ENERGY EXPENDITURE AND ENERGY INTAKE IN CRITICALLY ILL PATIENTS Energy Expenditure and Intake in Critically Ill Patients

Objective: To measure the energy expenditure (EE) of critically ill patients and to determine the adequacy of energy intake in terms of nitrogen balance. Research Methods & Procedures: Indirect calorimetry was performed in 17 critically ill patients under mechanical ventilation in order to calculate EE, and 24 h urinary nitrogen excretion was determined in order to calculate the nitrogen balance. Basal EE (BEE) was calculated by the Harris-Benedict equations. Hypermetabolism was considered to be present when EE was higher than 30% of BEE and hypometabolism was considered to be present when EE was lower than 10% of BEE. Information was obtained about the nutritional therapy instituted and the quantity administered. Underfeeding was characterized by an energy intake ≤ 90% of EE and overfeeding by an energy intake 110% do EE. Results: There was a predominance of normal (65%) and hypometabolism (23%). The measured EE of the patients ranged from 1131 to 2320 kcal.d-1, with a mean of 1515±268 kcal.d-1. There was a 53% rate of inadequate nutritional intake, with 23% of the patients being underfed and 30% being overfed. Most patients presented a negative nitrogen balance (11/14), with a mean of -5±7g.d-1 and a positive and highly significant association was detected between the energy intake/measured EE ratio and the nitrogen balance. Conclusion: In view of the marked variations in EE estimates compared to measured EE, the recommendation is to use indirect calorimetry, with caution in the use of correction factors in order not to overestimate the energy requirements, and to monitor systematically the administration of the prescribed nutritional therapy.