Incorporating enteral nutrition into your practice - Veterinary Medicine
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Incorporating enteral nutrition into your practice
Since it's critical that ill animals receive adequate calories, if these patients aren't voluntarily consuming enough it is your responsibility to provide assistance. So read on for the why, when, what, and how of enteral nutrition.



Factors that should be considered when determining if a patient requires assisted feeding include the animal's underlying medical condition, the medications it is receiving, and the duration of anorexia (complete absence of appetite) or hyporexia (decreased appetite). Given the loss of critical lean body mass associated with illness or injury, animals that have been—or are anticipated to be—anorectic for longer than three to five days require nutritional support, as this period is when deleterious effects (e.g. enterocyte atrophy, decreased immune function) begin to be observed.2,7,8 It is important to consider a patient's entire duration of anorexia or hyporexia, including time at home before presentation.2 In animals that are already malnourished, the lag time before initiating enteral nutrition should be abbreviated since the adverse effects of anorexia have already begun.

Table 1: Comparison of Feeding Tube Options
A feeding plan should be instituted as soon as the patient is hemodynamically stable. Whenever possible, enteral feeding is preferred because it provides the most physiologically sound method of nutritional support and is less expensive than parenteral nutrition. In addition, enteral nutrition supports normal gastrointestinal structure and function.


See Your feeding tube options and Table 1 for pointers on which feeding tube is best for various presentations.


All nutrition plans should include precise feeding orders, including the amount, route, frequency, and diet to be fed.


The amount of food consumed and the caloric density of the food (calories per can or cup; available from product guides or manufacturers' websites or by calling the manufacturer) must be recorded so you can monitor the patient's caloric intake. If the amount fed and eaten are recorded (e.g. feed diet X orally – can four times a day; ate 50% of food offered [ can]), the specific number of calories eaten per day can be calculated and compared with the patient's requirements to ensure adequate voluntary intake.

It is recommended to feed a hospitalized, ill animal its resting energy requirement (RER). While the exponential equation for calculating RER (70 x body weight in kg0.75 ) is more accurate, the linear equation (30 x body weight in kg + 70) is a reasonable approximation of caloric needs for animals weighing 3 to 25 kg.2,9

When calculating RER for a patient that is at its ideal weight (4/9 or 5/9 BCS), is underweight (< 4/9 BCS), or is mildly overweight (6/9 BCS), the animal's actual weight should be used.

For an animal that is moderately to severely overweight (BCS > 7/9), using an adjusted body weight to calculate RER may be more appropriate to avoid overfeeding. When calculating RER for animals with a BCS > 7/9, we use the ideal weight plus 25% of the animal's excess weight to account for the proportion of lean body mass that typically accompanies overweight animals. For example, for an 80-lb dog that should weigh 60 lb, the adjusted weight we would use to calculate RER would be 65 lb (60 lb + [25% x 20 lb]).

Once the patient is at home, maintenance energy requirement (MER) can be calculated by multiplying the RER by an activity factor. This activity factor may range from 1 to 1.8, depending on the animal's activity level and metabolism (e.g. neutered adult dog = 1.6; neutered adult cat = 1.2).10 However, it is important to remember that while the calculations for both RER and MER provide a starting point, the amount fed often needs to be adjusted over time to maintain a patient's body weight and optimal body condition.

Appetite stimulants (e.g. mirtazapine) may provide some benefit to animals with decreased appetites11-13; however, the underlying disease must also be addressed. It is still important to give specific feeding instructions and to monitor intake and body weight since many animals receiving appetite stimulants do not consume adequate amounts to achieve RER or maintain weight.

If a patient does not eat sufficient amounts voluntarily, there are many methods by which animals can be encouraged to eat.7,8 Offering the animal its favorite foods or feeding it in a quiet location may be effective. Warming the food or sitting with the animal may also increase food intake. Introducing a new diet to a hospitalized animal (especially a veterinary therapeutic diet indicated for long-term management) should not be prioritized because it may contribute to the development of a food aversion (the animal adversely associates a specific food with a feeling of illness).

For some animals, syringe feeding may be attempted. In these cases, using a liquid enteral diet or a calorie-dense critical care diet may be useful. Careful attention must be paid to the total calories eaten compared with the animal's RER to ensure that underfeeding does not occur. If adequate intake cannot be met or if the animal is exhibiting signs of nausea or stress, syringe feeding should be avoided.


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