[Energy metabolism of the brain in children (author's transl)].

Oxygen consumption of the human brain is of the order of 3,5 ml./minute. Since the brain of a 70 Kg. man has a weight of 1,400 g., its total oxygen consumption is close to 50 ml./minute. Thus, whereas the brain weight accounts only for about 2 percent of the body weight its oxygen consumption accounts for some 20 percent of the resting energy metabolism (BMR) of the body. Measurements in animals of different size indicates that the oxygen consumption of the mammalian brain, per unit of weight, is practically independent of body size. Accordingly, the above figure can be used to make an estimate of the fraction of BMR accounted for by the energy metabolism of the brain, in different species. The proportion of brain weight to total body weight changes during the period of growth. The brain of a new-born baby represents some 10 to 11 percent of the total body weight. Therefore, in spite of the fact that the BMR/Kg. is higher in the infant, the fraction of BMR accounted for by the metabolism of the brain, is expected to be higher in the infant and child than in the adult. The calculations presented in this paper show that the energy metabolism of the brain may account for about 50 percent of the BMR in the new-born. As indicated by our calculations the proportion of BMR accounted for by the energy metabolism of the brain decreases with age, but it still accounts for about 30 percent of the BMR at age 12 years. Our calculations also show that much of the decrease of BMR/Kg. that takes place during infancy and childhood, is due to the decrease in the proportion of brain weight to total body weight. Undernourished children tend to have higher brain weight, relative to total body weight, than eutrophic children. It has been proposed, that this fact could explain the high BMR observed in malnourished children during nutritional rehabilitation.