Chapter 9
FLUIDS, ELECTROLYTES & NUTRITION
Brian Kenney, MD
Marjorie J. Arca, MDI. Nutritional Physiology
Nutritional support for critically ill patients is an important element of care,
especially for infants and children who have requirements for growth and
development in addition to maintenance. Surgical patients have further
supplementary needs due to the stress of trauma and surgery. Nutrition in all
patients is best provided via the enteral route but many surgical patients require
parenteral nutrition. Calories are delivered primarily from carbohydrates and
lipids with protein provided to give essential amino acids for humoral and
structural proteins. The caloric density of carbohydrates is 4 kcal/g (dextrose, 3.4
kcal/g), lipids 9 kcal/g and protein 4 kcal/g.
Adult caloric storage is mainly found in fat. The average adult male
carries fat with the energy storage equivalent of 167,000 kcal. Muscle and
visceral proteins contain approximately 24,000 kcals. Carbohydrates, which are
stored in liver and muscle glycogen, contain a limited storage capacity of
approximately 1,200 kcals, which is sufficient for approximately 18-24 hours of
fasting. The brain and kidney have obligate glucose requirements of
approximately 150-180 grams per day (600 to 720 kcal/day). Because fats
cannot be converted to glucose, glycogenolysis is needed for the first 24 hours of