Role of Glutamine inCriticallyIll Patients

Abstract

Summary G lutamine (Gln) is an important energy source and has been used as a supplementary energy substrate. Furthermore, Gln is an essential component for numerous metabolic functions, including acid-base homeostasis, gluconeogenesis, nitrogen transport and synthesis of proteins and nucleic acids. Therefore, glutamine plays a significant role in cell homeostasis and organ metabolism. It is known as a non-essential amino acid due to the ability of most cells to produce it. Glutamine is present in the plasma at levels around 0.6 mM and in the intracellular space at levels around 2 and 20 mM. It also serves as a metabolic intermediate, contributing carbon and nitrogen for the synthesis of other amino acids, nucleic acids, fatty acids, and proteins. Glutamine is consumed predominantly in the gastrointestinal tract as a source of energy, particularly under the conditions of trauma, sepsis and surgery. Glutamine has a unique role in the preservation of epithelial barrier function in the gastrointestinal tract. Glutamine supplementation protects the gastrointestinal mucosal homeostasis during total parenteral nutrition, diarrhea, radiation injury, starvation, sepsis and trauma. It plays multiple roles in the maintenance of physiological homeostasis of diverse organs and cell types. It is best known for its ability to serve as a source of fuel for the cells such as enterocytes, renal epithelial cells, hepatocytes, neurons, immune cells, Beta cells of pancreas. Glutamine metabolism plays multiple roles in nitrogen balance, regulation of glucose metabolism and acid base homeostasis. It is quantitatively the most important donor of ammonia in kidney and liver, and plays a role in maintaining the acid-base balance of body fluids. Parenteral glutamine administration is associated with a decrease in infectious complications, decrease in hospital length of stay, and possibly a decrease in mortality in critically ill postoperative or ventilator dependent patients requiring parenteral nutrition (PN). It may be beneficial in certain other adult surgical patients, such as patients undergoing major abdominal surgery, critically ill non-ventilated patients, in adult burn patients or acute pancreatitis patients who require PN.