Page 624 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

612 SPECIAL THERAPY

are provided by a lipid emulsion; however, fat is not Amino Acids
required on a daily basis. Some nutritionists formulate Amino acid solutions provide a nitrogen source and essen-
parenteral nutrition without lipids or provide an intermit-
tial amino acids. Amino acid solutions are available in
tent infusion of a lipid emulsion when animals remain
varying concentrations from 3.5% to 10%. However, the
on parenteral nutrition for prolonged periods over which worksheets in this chapter use amounts specific for an
essential fatty acid supplementation would be required. 9
8.5% amino acid solution. Other concentrations could be
Electrolytes, vitamins, and trace elements also may be
used, but the amounts would need to be adjusted
added to the parenteral nutrition formulation.
accordingly. Most amino acid solutions are available in
Depending on the hospital and the patient, electrolytes
two formulations: one with electrolytes and one without
can be added individually to the admixture, added as an
(see Table 25-3). The majority of animals receive parenteral
electrolyte mixture, included as part of the amino acid
nutrition formulated using amino acids with electrolytes.
solution, or left out altogether and managed separately
However, amino acid solutions without electrolytes can
in the animal’s crystalloid fluid prescription. The most
be used for patients with marked electrolyte disturbances,
appropriate method will depend upon the individual case,
and these electrolyte imbalances are corrected separately
on the facilities, and on clinician preference. Because most
via other administered intravenous fluids.
animals receive parenteral nutrition for only a short dura-
The standard amount of protein included in the paren-
tion, fat-soluble vitamins usually are not limiting, and teral formulation is 4 to 5 g/100 kcal for dogs and 6 to
supplementation with TPN vitamin preparations 8 g/100 kcal for cats (although the optimal concentra-
designed for humans usually is not indicated. The excep- tion for ill and injured dogs and cats has not been
tion is obviously malnourished animals in which supple- determined). 15 This concentration can be reduced for
mentation may be desirable. Conversely, because B animals with protein intolerance (e.g., those with hepatic
vitamins are water soluble, they are more likely to become encephalopathy or severe renal failure) or increased for
depleted, particularly in anorectic animals. Therefore B those with higher needs (e.g., animals with large draining
vitamins should be routinely supplemented in the paren- wounds or hypoalbuminemia).
teral nutrient admixture. Trace elements serve as It is important to note that the essential amino acids
cofactors in a variety of enzyme systems and can become
provided in these solutions are intended to meet the
depleted in malnourished animals or during long-term
essential amino acid requirements in people. Currently,
parenteral nutrition. In people receiving parenteral nutri-
no amino acid solutions are made specifically for dogs
tion, zinc, copper, manganese, and chromium are
or cats, and therefore these solutions do not meet all of
routinely included in the parenteral nutrient admixture.
these species’ needs or provide amino acids in the optimal
These are sometimes added to parenteral nutrition
proportions. However, when used for short-term
preparations for malnourished animals, but in the
nutritional support, this situation is unlikely to result in
authors’ practice, they are not routinely included.
clinically relevant deficiencies. This may not be the case
Other nutritional requirements will depend on the
for certain amino acids such as taurine, which could
patient’s underlying disease, clinical signs, and laboratory
become limiting if parenteral nutrition were to be used
test results. Adjustments to the nutritional plan may
long term.
include sodium restriction for cardiac patients, protein
Other amino acid products are commercially available
restriction for encephalopathic and end-stage renal failure
for people, including those intended for patients with
patients, and fat restriction for patients with hypertrigly-
renal failure, hepatic failure (e.g., high concentrations
ceridemia. Finally, there may be certain nutrients that may of branched chain amino acids), and for neonates. Some
have benefits when added in amounts above their nutri- of these products may meet companion animal needs, but
ent requirements. This concept is often called nutritional their additional cost usually does not justify their
pharmacology. The addition of immune-modulating hypothetical benefits.
substances such as arginine, glutamine, antioxidants, Dextrose
and n-3 fatty acids to parenteral nutrition preparations
may offer added benefits, but few studies have been Dextrose is a component of nearly all parenteral nutrition
conducted in companion animals. 13,18,52 formulations. In the formulations provided in this
chapter, a 5% dextrose solution is used in PPN, whereas
PARENTERAL NUTRITION a 50% dextrose solution is used in TPN. Different
COMPONENTS concentrations can be used, but the worksheets would
Typically, the desired parenteral nutrition formula is need to be adjusted accordingly. A 50% dextrose solution
calculated, and the components are compounded into a provides 1.7 kcal/mL, whereas the 5% solution provides
parenteral nutrient admixture. This solution is most often 0.17 kcal/mL. Typically, in TPN, half of the nonprotein
composed of amino acids, dextrose, and lipid along with calories are provided by dextrose, but the ratio between
vitamins and minerals. Information on the various paren- dextrose and lipid can be adjusted depending on the indi-
teral nutrition components is presented in Table 25-3. vidual circumstances (e.g., a greater proportion of lipid