Page 439 - Small Animal Clinical Nutrition 5th Edition

Enteral-Assisted Feeding 453

ed amino acids will be used for tissue synthesis and repair patients and theoretically enhance the host’s capacity to resist
VetBooks.ir (Mallet, 1984). Excessive protein feeding requires energy infection. Arginine enrichment stimulates the immune sys-
tem, improves wound healing and decreases morbidity and
expenditure to rid the body of excess nitrogen, which, in certain
mortality in burn patients. A feeding regimen with arginine as
patients, may or may not be handled well by the liver (urea
cycle) and kidneys and can result in hyperammonemia with 9% of the protein source has been suggested and tested in
accompanying clinical signs of encephalopathy. Conversely, burn patients.Those receiving the arginine-enriched food had
insufficient protein has been linked to low albumin concentra- a significant reduction in the incidence of wound infection
tions, poor immune response, impaired healing and increased and shorter hospital stays. As a nutrient substrate, arginine
risk of wound dehiscence and muscle wasting. The most effi- appears nontoxic and may benefit surgical patients at
cient use of protein in people occurs when 2 to 6 g protein/100 increased risk of infection (Goffschlich et al, 1990). The opti-
kcal are administered (Stein, 1986). mal arginine intake for people is unknown, so selection of
Commercial products intended for enteral support of canine enteral foods based solely on arginine content is not recom-
and feline critical care patients provide between 5.5 and 14.3 g mended for human patients.
protein/100 kcal. Due to a lack of evidence to the contrary and Numerous studies in a variety of animal models demonstrat-
because these products appear to work well in critical care ed the efficacy of arginine-supplemented foods in reducing the
patients, a range of 5.0 to 12.0 g protein/100 kcal is recom- catabolic response to major trauma, sepsis and injury and in
mended for canine patients and 7.5 to 12.0 g protein/100 kcal improving the immune response after a variety of adverse stim-
is recommended for feline patients. Because of the overlap of uli. For example, a food containing arginine as 2% of the total
these recommendations, several commercial products intended nonprotein calories significantly increased survival after 30%
for enteral support are designated for use in both canine and surface burns (Irenton-Jones and Baxter, 1990). Furthermore,
feline critical care patients. in animal studies, exogenous arginine supplementation consis-
When formulating parenteral nutritional support, it is pru- tently improved nitrogen retention, protein turnover and
dent to first provide for total caloric needs with carbohydrate wound healing. Arginine augments cellular immunity, as evi-
and fat, and then meet the protein requirement. If sufficient denced by enhanced skin allograft rejection in normal mice,
calories are supplied to patients as either fat or carbohydrate, and improves delayed hypersensitivity responses.
then most of the essential amino acids will be used for protein Arginine is an essential amino acid in dogs, cats and people.
synthesis and not burned for energy. A starting point of 2 to 3 Therefore, most pet foods meeting AAFCO nutrient concen-
g protein/100 kcal parenterally (Remillard and Thatcher, 1989) trations should contain at least 146 mg arginine/100 kcal for
can be used for most dogs that can excrete protein waste prod- adult dogs and 250 mg arginine/100 kcal for adult cats (provid-
ucts and do not have an extraordinary protein loss. A lower ing approximately 80 to 200 mg/kg body weight). Arginine
range (1 to 2 g/100 kcal parenterally) is a more reasonable esti- content of human enteral products is variable but usually stat-
mate for patients with kidney or liver diseases. A higher range ed on the label. Human enteral products and parenteral nutri-
(3 to 4 g/100 kcal parenterally) is a more reasonable estimate tion solutions must contain at least adequate amounts of argi-
for cats because of their constant state of gluconeogenesis from nine if used for more than a few days in dogs or cats.
amino acids. Protein intake can then be adjusted based on the
patient’s needs and ability to handle the initial protein recom- Glutamine
mendation (e.g., decreasing serum albumin concentration or Glutamine is an amino acid that plays an important role in
encephalopathic signs). many cellular processes. Human studies suggest that glutamine
In addition, specific nutrients affect immunocompetence. concentrations in whole blood and skeletal muscle decrease
Some nutrients act directly on the lymphoid system and markedly following injury and other catabolic states, thus mak-
immune cell function, thereby altering host immune response ing it “conditionally” essential during serious injury or illness
to pathogens. As an example, arginine, glutamine and dietary (Lacey and Wilmore, 1990). Numerous clinical trials suggest
nucleotide-enriched foods are associated with significant that intervention with glutamine reduces rates of infectious
reduction in wound infection and length of hospital stay in complications in postsurgical patients and complications and
human burn patients. mortality rates in critically ill patients (Novak et al, 2002).
Replicating cells such as fibroblasts, lymphocytes and intestin-
Arginine al epithelial cells have high glutaminase activity and consume
Arginine is essential to traumatized patients. It has a marked glutamine, but the intracellular level of glutamine remains low.
immunopreserving effect in the face of immunosuppression The mechanism linking the beneficial effect of glutamine on
induced by protein malnutrition and cancer. In postsurgical attenuating cellular metabolic dysfunction and enhancing cell
patients, arginine supplementation enhances T-lymphocyte survival depends on glutamine-induced enhancement of specif-
response and augments T-helper cell numbers, with a rapid ic heat shock proteins (Peng et al, 2006).These findings may be
return to normal T-cell function postoperatively, compared important for patients with large wounds or inflammation
with findings in control patients (Bower et al, 1995). These associated with infection.
data taken together suggest that arginine supplementation The controversy persists as to which route of glutamine
may increase or preserve function in high-risk surgical administration (enteral or parenteral) is most effective at