Page 441 - Small Animal Clinical Nutrition 5th Edition

Enteral-Assisted Feeding 455

doxine and B 12 are essential for hepatic metabolism of glucose, approximately 1 ml per 100 kcal of solution.
VetBooks.ir fat and protein. These are coenzymes for the tricarboxylic acid Fat-Soluble Vitamins and Macrominerals
(TCA) cycle, ATP production and RBC metabolism. B vita-
Hospitalized patients rarely need fat-soluble vitamins and
mins are required in small amounts relative to other nutrients,
but they are required daily and are necessary for efficient ener- macrominerals. Most patients have fat and hepatic stores of the
gy metabolism. Most commercial pet foods contain adequate fat-soluble vitamins sufficient to meet metabolic needs for
amounts of these nutrients, so deficiency should not be of con- months to years. However, administering fat-soluble vitamins
cern if the patient is eating or being fed enough food to meet should be considered in cases of prolonged malnutrition in
its RER. B vitamins should be added to the fluids (1 to 2 ml of which the patient is severely underweight with little to no fat
vitamin-B complex/1,000 ml of crystalloid fluid) of all patients stores (i.e., BCS 1/5). Most pet foods contain adequate amounts
that are not eating but receiving fluid therapy or parenteral of these nutrients,thus deficiency should not be of concern if the
nutrition support. patient is eating enough food to meet its RER. Fat-soluble vita-
mins are not added to parenteral nutrition solutions due to
Microminerals insolubility problems. It is easiest to administer a single dose of
Zinc, copper, manganese, chromium and selenium are vital vitamins A, D and E by deep intramuscular injection to patients
cofactors for optimal hepatic and peripheral metabolism of needing these vitamins. Such an injection supplies approximate-
energy substrates. Microminerals (i.e., trace minerals or trace ly one to two months of daily requirements.
elements) are important cofactors (metalloenzymes) and partic- Macrominerals (i.e., calcium, phosphorus, magnesium, sodi-
ipate in tissue repair and albumin synthesis; therefore, zinc, cop- um and potassium) are rarely needed by patients above that
per and manganese should be included in all food forms used for required to maintain serum electrolyte levels.Whole body stores
assisted feeding. Most pet foods contain adequate amounts of of these minerals can be depleted but are usually easily correct-
these nutrients, thus deficiency should not be of concern if the ed by intravenous administration. The distribution between the
patient is eating enough food to meet its RER. Specialized solu- intracellular and extracellular fluid space can be a problem and
tions containing essential trace (zinc, copper and manganese) imbalances should be corrected before assisted feeding is begun
minerals can easily be added to parenteral nutrition solutions at (Box 25-3). Sodium, potassium and magnesium levels may

Box 25-3. Refeeding Syndrome.

Refeeding syndrome in people is characterized by generalized mus- nary excretion of potassium, exacerbates hypokalemia and causes
cle weakness, tetany, myocardial dysfunction, dysrhythmias, sei- hypocalcemia, which is refractory to supplementation until the
zures, excessive sodium and water retention, hemolytic anemia and hypomagnesemia is corrected. Little information is available about
death due to cardiac or respiratory failure. A similar syndrome magnesium status in hospitalized dogs and cats; however, serum
occurs less commonly in veterinary patients. When it does occur, it magnesium levels should probably be monitored in veterinary
is most often seen in patients receiving parenteral nutrition or dur- patients with abnormal serum electrolytes.
ing inappropriate assisted enteral feeding and most commonly
presents as hypokalemia or hypophosphatemia. Significant elec- RECOMMENDATIONS FOR AVOIDING COMPLICATIONS OF
trolyte shifts occur from extracellular to intracellular compartments THE REFEEDING SYNDROME
as energy and amino acids are reintroduced. This electrolyte shift 1. Anticipate the potential for the problem and re-feed with for-
will occur regardless of the route of administration (i.e., enteral or mulations known to contain adequate potassium, phosphate
parenteral). Often serum ion levels are deceptively normal in ano- and magnesium levels and lowered digestible (soluble) carbo-
rectic patients before refeeding begins (Table 25-4). However, hydrate content.
when calories are reintroduced, particularly from carbohydrate, 2. Use initial nutritional refeeding rates that do not exceed the
potassium and phosphate shift intracellularly with glucose resulting patient’s resting energy requirement (RER) and 2 to 6 g pro-
in hypokalemia and hypophosphatemia. tein/100 kcal (parenterally) or 5.5 to 7.5 g protein/100 kcal
Potassium moves into cells with refeeding because glucose stim- (enterally). These rates can be increased as needed over sub-
ulates insulin release, which in turn stimulates the Na-K ATPase sequent days. Consider refeeding a high-fat, low-carbohydrate
pump and glycogen synthesis, which requires 0.33 mEq potassi- formula to patients that have not eaten for four to five days or
um/g of glycogen. Phosphate moves into cells with refeeding to more.
support the increased production of phosphorylated intermediary 3. Monitor serum potassium, phosphate and magnesium levels
compounds of energy metabolism. Severe hypophosphatemia, as needed. Once a day is sufficient for most cases.
hemolytic anemia and death have occurred in cats within 12 to 72 4. Supply water-soluble vitamins free choice, particularly thiamin,
hours of refeeding with either an apparently normal or phosphorus- to facilitate energy metabolism.
deficient diet. The refeeding formula should contain at least the 5. Monitor patients daily for signs of fluid overload and conges-
Association of American Feed Control Officials recommended min- tive heart failure.
imum allowance of 0.5% dry matter phosphorus.
In people, hypomagnesemia is another common electrolyte com- The Bibliography for Box 25-3 can be found at
plication that must be corrected. Hypomagnesemia increases uri- www.markmorris.org.