Page 440 - Small Animal Clinical Nutrition 5th Edition

454 Small Animal Clinical Nutrition

improving clinical outcomes in critically ill patients. At least in fewer postsurgical diarrhea days compared to dogs adminis-
VetBooks.ir 80% of the published data in laboratory animals demonstrate a tered non-glutamine supplemented parenteral admixture
(Saker et al, 2001). In short-term studies in rats and pigs,
positive effect with glutamine-enriched feedings. Positive
effects include enhanced protein metabolism, intestinal and
adding glutamine to nutritional intravenous solutions reduced
pancreatic repair and regeneration, nutrient absorption, gut- some aspects of disuse intestinal atrophy and enhanced intes-
barrier function, systemic and intestinal immune function and tinal immune function (Remillard et al, 1998). Intravenous glu-
animal survival.The mechanism(s) for these effects are not well tamine supplementation immediately following hemorrhagic
clarified, but studies suggest several possibilities. First is the shock partially restored the depletion of hepatic ATP, reduced
inter-organ conversion of glutamine-derived citrulline to renal cellular apoptosis and oxidative stress-associated cell damage in
arginine synthesis (Ligthart-Melis et al, 2007). A second rat and feline models (Yang et al, 2007; Krizova et al, 2004),
mechanism is through glutamine attenuation of the gut- suggesting additional benefit from intravenous-glutamine sup-
derived inflammatory response (Wischmeyer, 2006). plementation during critical illness. Intravenous glutamine
Numerous animal studies have demonstrated the value of should probably be limited to short-term use (one week or less)
enteral glutamine during stress. For example, rats undergoing just before oral refeeding. Inclusion of 2% L-glutamine via the
abdominal radiation and fed glutamine orally for eight days fol- intravenous route has been safely used in human and veterinary
lowing the stress had significantly increased jejunal villous patients. However, it should be noted that inclusion of gluta-
number and height and an increased number of mitoses per mine in parenteral nutrition solutions can be difficult to achieve
crypt, whereas non-irradiated control rats fed the same food due to solubility constraints.
without glutamine supplementation had no significant increase
in mucosal cell activity (Klimberg et al, 1990). Similarly, dogs Fat
had an increased intestinal requirement for glutamine during Supplying the majority of calories as fat to critically ill patients
the immediate postoperative phase (less than seven days), but has several benefits. Fat contains 8.5 kcal metabolizable ener-
uptake rates returned to normal later during the recovery phase gy/g and is therefore calorically dense compared to carbohy-
(after 10 days) (Souba et al, 1987). Oral glutamine supplemen- drate and protein. Therefore, more calories may be provided in
tation influences GI function, along with cell morphology. For a smaller volume to patients. After three to five days of not eat-
example, rats undergoing ischemia-reperfusion injury main- ing, the liver has shifted from glucose to fat metabolism, there-
tained small intestinal barrier function when provided with fore providing more fat and less dextrose at this time reduces
enteral glutamine (Kozar et al, 2004). metabolic complications of nutritional support. Additionally,
Provision of exogenous glutamine to stressed patients might providing calories as fat rather than dextrose reduces CO pro-
2
better support the metabolic requirements of the small intestine duction, which noticeably reduces respiratory work in patients
and possibly decrease the rate of systemic protein catabolism requiring oxygen therapy. On average, “recovery” type foods
(Wischmeyer, 2006), therefore, supplementation is warranted. provide 5 to 7.5 g fat/100 kcal; this appears to be a safe starting
The optimal concentration of glutamine for different disease point for refeeding. The exceptions include patients with pan-
states is still under study. It is presently unclear whether gluta- creatitis or other conditions in which enteral intake of a high-
mine must be in the free form to be beneficial or if the protein- fat food is not tolerated.
bound form is also beneficial in maintaining gut integrity. Most
enteral foods contain some protein-bound glutamine but the Other Nutritional Factors
glutamine concentration of these products must be estimated. Other nutritional factors can be important considerations for
Some enteral products have added free glutamine. The gluta- enteral foods or parenteral fluids for critical care patients.
mine content of these products is often stated on the label. Factors such as vitamins and minerals are typically included in
Glutamine levels in commercial enteral foods intended for crit- adequate amounts in commercial veterinary therapeutic enteral
ical care canine and feline patients should be at least 500 foods formulated for dogs and cats. However, these nutrients
mg/100 kcal. are important to consider in parenteral nutrition support.Other
Although based on human studies indicating the gut prefer- factors (nucleotides, essential fatty acids and antioxidants) may
ably takes up enterally administered glutamine compared with benefit veterinary patients based on the human critical care lit-
intravenously provided glutamine (Ligthart-Melis et al, 2007), erature and case reports. The optimal daily dose and duration
evidence suggests intravenous glutamine can provide benefits as of provision have yet to be standardized for dogs and cats.
well. In protein-depleted rats, intravenous glutamine supple- Typical ingredients used in many enteral foods contain
mentation resulted in increased villous height, increased small- nucleotides, essential fatty acids and antioxidants. Some critical
bowel mucosal weight, enhanced DNA activity (O’Dwyer et al, care foods have been specifically enriched, whereas others have
1989) and improved DNA content and sucrase and lactase not been and would need exogenous supplementation if they
activities. Parenteral admixture supplemented with 2% gluta- were deemed valuable. Provision enterally is more efficient and
mine and administered for 48 hours before and 72 hours practical than through parenteral fluids.
postintestinal abdominal surgery in undernourished dogs
improved ileal morphology, increased CD4:CD8 cells, select B Vitamins
immunoglobulins and mononuclear cell function and resulted Folic acid, thiamin, riboflavin, niacin, pantothenic acid, pyri-