The current status of protein sparing.

Solutions of crystalline amino acids infused without dextrose produce a marked improvement in nitrogen balance. Increasing the infusion level of amino acid from 1.0 to 1.7 grams per kilogram further improves nitrogen balance. The addition of dextrose to the amino acid solutions did not affect nitrogen balance and proved that the role of insulin during protein sparing has been overemphasized. Nitrogen balance is slightly, but not significantly, superior when nonprotein dextrose calories are administered. However, amino acid solutions are isotonic and can be infused peripherally, whereas adding dextrose doubles the concentration and renders peripheral infusion more difficult. Protein sparing may be useful for short term nutritional support when the potential risks of total parenteral hyperalimentation are not justified. Endogenous body fat is mobilized. Hence, protein sparing also prevents the development of fatty acid deficiency and may be useful in treating fatty infiltration of the liver. Protein sparing provides suboptimal caloric replacement and should only be used for temporary nutritional support until oral alimentation is resumed or until there is an absolute indication for intravenous hyperalimentation. Expense and the fact that most patients do well after elective abdominal operations militate against the proposition that amino acids should become a routine substitute for 5 per cent dextrose therapy post-operatively.