Glutamine and Arginine in ICU nutrition

I want to make a note on arginine and glutamine today, just for me to remember some important points if asked during viva.
Glutamine

• serves as an oxidative fuel and nucleotide precursor for enterocytes and immune cells, mainly lymphocytes, neutrophils and macrophages.
• regulates the expression of many genes related to signal transduction and to cellular metabolism and repair.
• During critical illness glutamine is released in large quantities from skeletl muscle in order to supply this need. In these circumstances it may become 'conditionally essential' and is vulnerable to depletion, with potentially adverse effects on gut barrier and immune function which may in turn impair the ability to survive a sustained period of critical illness once glutamine stores are depleted.
• Evidence is debatable. Reductions in infectious complications and length of ICU stay were shown in small early studies of enterally fed trauma and burns patients. A larger study in unselected ICU patients found no effect on any outcome. (Intensive Care Med 2003).
• The evidence for TPN is contradictary. There are suggestions from meta analysis that there is a demonstrable mortality benefit from higher doses of parenteral glutamine (http://www.criticalcarenutrition.com/). This awaits confirmation in a large RCT. It seems that the patients most likely to benefit are those requiring TPN for more 10 days.

Arginine

• a non-essential amino acid acts as a precursor of NO, polyamines (important in lymphocyte maturation) an nucleotides.
• Animal studies suggest enhanced cell mediated immunity and survival when arginine is supplemented.
• Several commercially available enteral feeding solutions combine omega 3 fatty acids, arginine, nucleotides and in one case glutamine to produce imune enhancing diets. They have been assessed in a number of trials. Meta-analysis has suggested reductions in hospital stay and infections but not in mortality.
• Subgroup analysis revealed an increase in mortality when arginine supplementation was given to septic patients (JAMA 2001). Interim safety assessment of a RCT led to its early cessation when this finding was replicated in the subgroup of patients with sepsis (Intensive Care Med 2003). It appears that arginine should not be used septic patients. There are suggestions of benefit in patients undergoing surgery or suffering from a burn injury, there is little basis for their general use in ICU patients unless it is justified by future prospective trials.

Reference: Oh Intensive care manual

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