can impede recovery from injury. An understanding of the metabolism of the very young and the very old is necessary to provide adequate nutritional support to optimize wound healing.
The body composition of the young child contrasts with the adult in several ways that significantly affect nutritional requirements. Listed in Table 13.1 are the macro-nutrient stores of the neonate, child, and healthy young adult as a percentage of total body weight.123 Carbohydrate stores are limited in all age groups and provide only a short-term supply of glucose when utilized. Despite this fact, neonates have a high demand for glucose and have shown elevated rates of glucose turnover when compared to the adult.4 Short periods of fasting can predispose the newborn to hypogly-cemia. Thus, when infants are burdened with critical illness, they must turn to the breakdown of protein stores in order to generate glucose through the process of gluconeogenesis. Lipid reserves are also reduced in the neonate and gradually increase with age. The lowest proportion of lipid stores is found in premature infants, as the majority of polyunsaturated fatty acids accumulate in the third trimester.5 The most dramatic difference between young adults and pediatric patients is in the relative quantity of stored protein. Protein reserves are nearly doubled in the adult as compared to the neonate. Hence, infants cannot afford to lose significant amounts of protein during the course of protracted critical illness or injury.
Neonates and children also have much higher baseline energy requirements. Studies have demonstrated that the resting energy expenditure for neonates is two to three times that of adults when standardized for body weight.6-8 Clearly, the child's need for rapid growth and development is a large component of this increase in energy requirement. Moreover, the relatively large body surface area of the young child may increase heat loss and thereby contribute to elevations in energy expenditure.
The basic requirements for protein and energy in the healthy neonate and child based on recommendations by the National Academy of Sciences are listed in Table 13.2.9 It should be noted that the recommended dietary protein provision for the neonate
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