Immunonutrition
Another form of directed nutritional support affects the ability
of certain nutrients to stimulate or improve immune function during stress states.
This type of nutritional support has been called immunonutrition.
Immunonutritional support is composed of omega-3 fatty acids and the "conditionally
essential" amino acids arginine, glutamine, cysteine, and taurine.[176]
The lipid component should include medium-chain and long-chain triglycerides, polyunsaturated
omega-3 and omega-6 fatty acids. These nutrients have been suggested to enhance
immune function through various mechanisms. For example, omega-3 fatty acids have
been shown to reduce the immunosuppressive actions of omega-6 polyunsaturated fatty
acids found in most other enteral products. Arginine enhances wound healing and
lymphocyte immune responses and stimulates T-cell proliferation in humans. Glutamine
is used by lymphocytes as fuel for energy production and promotes intestinal gut
mucosal integrity through increase of villous height and stimulation of gut mucosal
cellular proliferation.[177]
[178]
Immunonutrition is especially important when a patient's immune
system is compromised, as in sepsis or systemic inflammatory response syndrome.
In these patients, the immunonutritional support should be started early, preferably
through the enteral route.[177]
However, in clinical
trials consisting of trauma patients (injury severity score [ISS] > 13), administering
arginine along with trace elements and omega-3 fatty acids required longer lengths
of stays compared with those fed a standard formula.[179]
In another study, trauma patients with higher injury scores (ISS > 20) did not
show any beneficial effect of the
Figure 77-21a
Order form for adult total parenteral nutrition. (Courtesy
of Pennsylvania State University, Hershey, PA.)
Figure 77-21b
immunonutritional support.[180]
The role of these
nutritional additives remains somewhat controversial.
