Prescribing total parenteral nutrition

The caloric value of protein is approximately 4 kcal/g. [...]carbohydrates must supply about 70% of an individual's daily non-protein needs. Lipids are available in 10% or 20% concentrations in units of 50 mL; 50 mL of 10% lipid contains 50 kcal. [...]our hypothetical patient can simply receive 84 mL of the 10% lipid emulsion in the TPN to make up the difference in caloric needs. When the recommended quantity of protein is administered, its contribution to the serum urea nitrogen is relatively minor (5 to 15 g/dL) compared with the level arising from the turnover of endogenous protein in a hypercatabolic patient (up to 200 g/dL). [...]dextrose and lipids delivered in TPN reduce endogenous protein turnover only if adequate exogenous protein is provided.