Feeding challenging hospitalised patients to prevent malnutrition

A very close relationship exists between disease and malnutrition. Malnourished animals are more prone to disease, due to alterations in organ function, immune system and healing.

On the other hand, ill animals (particularly critically ill ones) are more prone to malnutrition due to several factors related to a decrease in nutrient and energy intake, an increase of nutrient and energy losses, or a combination of both (Figure 1). This can result in higher morbidity and mortality.

One study identified 50% of hospitalised cats had lost weight and appetite at the time of hospitalisation¹ and another study found hospitalised cats and dogs did not meet their energy needs more than 70% of the time².

The latter study identified almost half of the patients did not eat due to anorexia/hyporexia, a third did not eat due to medical orders to withhold food and a quarter did not receive specific orders on their file, thus were not offered food. The study highlighted the importance of developing a nutritional plan for each patient as soon as possible and the need to document it.

The WSAVA’s nutrition tool kit has downloadable charts to note the nutritional plan and monitor daily food intake in hospitalised patients, available at www.wsava.org/nutrition-toolkit

Regarding losses, some patients present with vomiting, diarrhoea and/or polyuria – all of which can result in increased nutrient and energy requirements. Moreover, critically ill patients are in a hypermetabolic state³, resulting in increased energy needs and proteolysis.

Several studies have found energy intake is positively associated with outcome^2,4,5, thus it is very important to ensure hospitalised animals receive nutritional support.

Risk factors for malnutrition in hospitalised patients

Several risk factors exist for malnutrition in hospitalised patients.

One study, with 500 dogs and 100 cats, was performed at a Spanish veterinary teaching hospital and identified around 20% lost bodyweight and body condition score (BCS) during hospitalisation^5,6. The risk factors associated with such losses include age, vomiting at admission, hospitalisation length, percentage of energy requirements consumed and initial BCS.

Older dogs were at higher risk of malnutrition than younger dogs and vomiting was associated with loss of BCS. Low energy intake was also associated with malnutrition in both species and was specially marked in long hospitalisation periods.

Obese dogs and cats lost more BCS than thinner patients, although thin animals had a worse outcome. One hypothesis is obese patients might appear at less risk of malnutrition than underweight patients and nutritional intervention in these patients might be delayed.

Patient selection and feeding time: nutritional evaluation

It is important to carry out an extended nutritional evaluation⁷ on all hospitalised patients to identify risk factors, select patients needing nutritional support and decide the best course of action.

A list of malnutrition risk factors is shown in Table 1, and when two or more are present, the patient is a good candidate for advanced nutritional support. They are not very specific (especially blood work alterations), but, taken together, they give a good overall picture.

It is also important to identify if the disease process or treatment will result in inadequate food intake (such as in cases of facial fractures) to plan how to overcome the problem; for example, by placing a feeding tube at the moment of surgery.

Feeding plan

The feeding plan consists on deciding when, how, what and how much to feed.

When to intervene

Nutritional intervention should be instituted as soon as possible, once the animals is stabilised – regarding hydration, blood pressure, and electrolyte and acid-base balance.

Overall, patients that have been anorexic for three days (including before hospitalisation) or hyporexic for five days are candidates for nutritional support. For some, it is recommended to intervene faster, if possible, for patients with BCS<4, severe muscle atrophy, involuntary weight loss of more than 10% and high nutrient losses. In addition, elderly and young animals, and obese cats, require more immediate attention.

Route

The algorithm to choose the feeding route is presented in Figure 2. Oral voluntary intake is preferred, followed by enteral feeding tubes if the patient is unwilling to eat (see Table 2 for suggestions to promote voluntary feed intake⁸).

Parenteral nutrition is the last resort, as it is less physiological, less safe and more expensive than enteral feeding – see the review by Chan and Freeman³ for details on parenteral nutrition. Forced feeding is not recommended, due to risks of food aversion, injury, stress, and aspiration pneumonia.

Regarding feeding tubes, several factors will determine which to use, including disease, available diets and if anaesthesia is possible. In some patients, anaesthesia might be too risky, so using a short-term feeding tube until the animal is a better candidate to place a long-term solution is common.

In Table 3, the pros and cons of the most common feeding tubes are presented. For a more detailed review, see the reviews by Delaney et al (2006)⁹ and Goy-Thollot and Elliott (2008)¹⁰.

Nasoenteral tubes (nasooesophageal or nasogastric) do not require anaesthesia (only mild sedation) and are not invasive, so are a great short-term option – as long as liquid diets are available because slurries will result in tube obstruction.

Oesophagostomy tubes (Figure 3) are excellent mid-term to long-term solutions (weeks to months), very easy to place with low rates of complications and can be used at home, so are ideal for cats with hepatic lipidosis. Canned food can be made into slurry to go through these tubes (Figure 4).

Gastrostomy feeding tubes are a great long-term nutritional support (from two weeks to months and years) and can be used at home. They are also the best choice in cases of oesophageal dysfunction. Depending on the size, both canned and dry food can be made into slurry to feed the patient. Dry food should be pulverised in a blender, then water can be slowly added until achieving the desired texture.

Jejunostomy tubes are very rare, mostly used in hospital and can be applied where the stomach cannot be used or in cases of canine pancreatitis. Only liquid diets can be used, and constant rate infusion is better than bolus feeding, since it bypasses the stomach and the jejunum is not elastic.

It was proposed elemental (or monomeric) diets are best in these cases, since the feeding is post-pancreas, but regular liquid diets work well in most cases and monomeric diets are from human medicine, so are expensive and not complete or balanced for patients. Correct placement of feeding tubes should always be double checked by radiographs.

Diet choice

Several factors will affect diet choice, such as disease process, route of feeding, availability, price and personal experience. For many hospitalised patients, convalescence or recovery commercial diets are used.

These diets have several characteristics in common:

• They are both cats and dogs (with some exceptions).
• Texture adequate for tube feeding (with some exceptions): some can go through a 12F or higher tube (French; 1F = 0.3mm external diameter) without need for additional water. Others are in liquid form and are adequate for all tubes, and especially useful in thin ones, such as nasoenteral and jejunostomy tubes.
• High in energy density (at least 1kcal per g or ml).
• High in fat (around 50% fat calories): this helps achieve high energy density, also increases palatability and provides good texture for tube feeding. Moreover, critically ill patients are already consuming their own fat stores and the same energy fuel needs to be provided.
• Normal (cat)/high (dog) in high quality protein, to ensure ample protein and amino acid supply. Critically ill dogs and cats are at risk of protein deficiency due to proteolysis induced by inflammation.
• Low in starch, because critically ill patients can be insulin-resistant³ and, overall, it is the less palatable macronutrient.
• Complete and balanced, with all the important essential nutrients for adequate recovery and healing.
• Some have added eicosapentaenoic and docosahexaenoic acids (omega-3 fatty acids), which can be helpful for the control of inflammation¹¹.

These diets have some contraindications, especially related to high fat levels. Thus, their use is not recommended in canine pancreatitis, hyperlipidaemia and severe protein intolerance (such as uraemia and hepatic encephalopathy).

Amount to feed

To avoid the risks of overfeeding, it is recommended to feed the resting energy requirements (RER):

RER(Kcal/d) = 70 × bodyweight(kg)^0.75

Historically, the RER was modified with an illness factor of 1.4 to 2, under the assumption critically ill animals in an hypermetabolic state had higher energy requirements. However, their use resulted in overfeeding and many sick pets are in cage rest with energy requirements less than a healthy pet.

Once the RER for current bodyweight is calculated, it is divided by the energy density (kcal/g, kcal/ml or kcal/can) of the diet of choice for the daily amount.

Feeding method

Before feeding, especially via a feeding tube, water should be offered at small amounts (for example, 2ml/kg to 5ml/kg bodyweight) a couple of times to ensure tolerance and tube patency.

Food should be introduced slowly over several days, especially in patients that have been anorexic for a while (Table 4). The daily allowance should be given over three meals to four meals, separated at least by two hours.

The food should be warmed to body temperature. If tube feeding, it is very important to go slowly (more than 10 minutes to 20 minutes per feeding), and have the pet in a comfortable position and not manipulate him or her for a half hour after feeding. After feeding, the tube should be flushed with 5ml of warm water to prevent clogging.

In patients not receiving fluids, water requirements (70 × kg^0.75 ml/day) can be provided using the feeding tube (Table 4).

Follow-up

Besides the monitoring indicated for each disease process, bodyweight, BCS and muscle mass should be evaluated daily. The goal is to keep a stable bodyweight. Once the patient is receiving the full RER, the amount fed should be adjusted up or down by 10% to ensure stable bodyweight. In thin animals (BCS of 3 out of 9 or below), bodyweight gain is acceptable.

Food and energy intake should also be monitored daily. In patients eating orally, compare energy intake to the RER to ensure they are consuming at least 75% to 100%. This information, plus bodyweight evolution, will help determine if these patients need assisted feeding.

Signs that tube feedings are not well tolerated are vomiting, nausea, and abdominal pain. In these cases, evaluate a feeding method (such as temperature of slurry and speed of administration) and consider more feedings per day, or do a slower transition towards 100% RER. If fat intolerance is suspected, switch to slurry of a more adequate diet.