Parenteral Nutrition: Amino Acids

Abstract

There is growing interest in nutrition therapies that deliver a generous amount of protein, but not a toxic amount of energy, to protein-catabolic critically ill patients. Parenteral amino acids can achieve this goal. This article summarizes the biochemical and nutritional principles that guide parenteral amino acid therapy, explains how parenteral amino acid solutions are formulated, and compares the advantages and disadvantages of different parenteral amino acid products with enterally-delivered whole protein products in the context of protein-catabolic critical illness.

Keywords: amino acids; critical illness; nutritional support; parenteral nutrition; protein nutrition.

Figure 1

Peptide bond formation is a dehydration reaction. The molecular weight of a free amino acid is greater than its molecular weight in formed protein. Consequently, free amino acids provide less protein substrate and energy than the same weight of formed protein.