Page 627 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

614 SPECIAL THERAPY

compared with dextrose would be given to a hyperglyce- Minerals
mic animal). In people, the maximal amount of dextrose As previously mentioned, parenteral nutrition can be
that can be oxidized is 5 mg/kg/min. In fact, dextrose
formulated without any electrolytes or electrolytes can
infusion rates exceeding 4 mg/kg/min have been
be included, either as a component of an amino acid solu-
associated with the development of hyperglycemia in tion, added individually, or added as a combination of
nondiabetic human patients. 63 In light of these findings,
TPN electrolytes (most commonly, a combination of
the authors recommend limiting the amount of dextrose
sodium, potassium, calcium, magnesium, chloride, and
infused during parenteral nutrition to less than
acetate). The most effective method will depend on the
4 mg/kg/min. When formulating parenteral nutrition
individual hospital and, in some cases, the individual
for diabetic patients, a greater proportion of calories
patient. In certain situations, additional potassium or
should be provided from amino acids and lipids. Despite
magnesium may be added directly to parenteral nutrition.
adjustments to the formulation, diabetic patients often
However, the disadvantage of adding directly to the par-
require adjustment of insulin therapy during parenteral
enteral nutrient admixture is that if the animal’s
nutritional support.
requirements change during the day (or over a few days
if more than 1 day of parenteral nutrition is compounded
Lipid at one time) and the electrolyte is already in the admix-
Lipid emulsions are used in parenteral nutrition as an ture, the parenteral admixture must be reformulated or
energy source (a 20% solution provides 2 kcal/mL) and the animal will receive a less than optimal electrolyte
as a source of essential fatty acids. Commercial lipid composition. Adjusting electrolytes separately from the
emulsions in the United States are usually based on soy- parenteral nutrition allows greater flexibility.
bean oil or soybean and safflower oil. They also include Trace elements are sometimes added to the parenteral
egg yolk phospholipids, glycerin, and water. The presence nutrient admixture, but the authors only add them for
of soybean and safflower oil means that these solutions animals that are malnourished or are receiving parenteral
are composed primarily of n-6 fatty acids. High doses nutrition for 5 days or more. The most common trace
of lipid can cause immunosuppression via granulocyte elements supplemented are zinc, copper, manganese,
and reticuloendothelial cell dysfunction. 31,34,37 In addi- and chromium, with copper considered the most limiting
tion to immunologic effects, lipids can have hemody- of these elements. The authors use a commercial trace ele-
namic and inflammatory effects, the latter mediated by ment product containing (per 5 mL): 4 mg zinc, 1 mg
the more inflammatory eicosanoids produced from n-6 copper, 0.8 mg manganese, and 10 mg chromium at a
fatty acids. 30 In other countries, different types of lipid dosage of 0.2 to 0.3 mL/100 kcal (4 Trace Elements,
emulsions are available that may be preferable to the stan- Abbott Laboratories, North Chicago, Ill.).
dard soybean-based emulsions (e.g., n-3 fatty acids, n-9
fatty acids, medium-chain triglycerides, structured Vitamins
lipids), but these are not commercially available in the For most hospitalized animals, including a B vitamin
United States. The authors try to limit the lipid dosage complex to the parenteral nutrient admixture is sufficient.
in dogs and cats to 2.0 g/kg/day to prevent the potential Some B vitamins, particularly riboflavin, are light sensi-
for immunosuppression. Animals with hypertrigly- tive. Therefore sufficient B vitamin complex should be
ceridemia also require lower doses of lipid and may given such that the riboflavin dose is administered within
require a TPN formulation without any lipid. Although the first 6 hours of the parenteral nutrition infusion.
some dogs with pancreatitis have hypertriglyceridemia When using a commercial B vitamin complex containing
and require reduction (or elimination) of the lipid dose, thiamine, niacin, pyridoxine, pantothenic acid, riboflavin,
dogs with pancreatitis without hypertriglyceridemia do and cyanocobalamin (B vitamin complex, Veterinary
not need any reduction in the amount of lipid provided Laboratories, Lenexa, Kan.), a dosage of 0.2 mL/
from the standard calculation. 100 kcal should provide this amount of riboflavin.
Recently, the use of intravenous lipids for the treat- For debilitated animals or those that receive parenteral
ment of moxidectin toxicosis in a dogs was reported. 22 nutrition for prolonged periods, a TPN vitamin complex
A proposed mechanism as to how intravenous lipids can be included in the nutrient admixture. These
can be used to treat certain toxicities relies on the lipid products typically contain vitamins A, D, E, and C, in
solubility of the drug and the creation of a “lipid sink” addition to the B vitamins.
by infusion of lipids. The protocol used involved Although certain medical conditions may result in
administering a 1.5 mL/kg bolus of a 20% intralipid solu- vitamin K deficiency (e.g., biliary obstruction, hepatic
tion followed by a 0.25 mL/kg/min infusion for 60 disease), vitamin K is not typically administered intrave-
minutes. The amount of lipids used in this protocol is well nously and therefore is not added to the parenteral nutri-
within the guidelines of administered 2 g/kg/day of tion admixture. Interestingly, lipid solutions do contain
intralipids. vitamin K, which can be at sufficient concentrations to