Nutrition is an important consideration when managing critically ill patients. Depending on the patient’s condition (e.g., pancreatitis or parvoviral enteritis), early enteral nutritional support can play a crucial role in improving outcomes, increasing chances of survival, and reducing the time to discharge.1-3
For many patients, nutritional support should be started as soon as possible. Assisted feeding is indicated for some dogs and cats with anorexia or severe hyporexia. Because the effects of starvation become more pronounced after 3 days, provision of nutritional support, such as placing a feeding tube, is recommended within 3 days of the patient’s appetite decline.4 This “3-day rule” includes the time the patient was anorexic or hyporexic before the presentation. A feeding tube should also be considered if anorexia or hyporexia is anticipated for longer than 2 to 3 days in the future.
The many options for feeding tube type and selection of diet to deliver via feeding tube make it possible to individualize nutritional support plans. The 6 steps below describe how to tailor an enteral nutrition plan to your canine or feline patient.
1. Determine the Delivery Route and Place the Tube
Although this article focuses on developing a nutritional plan versus selecting or placing the feeding tube, some basic information about tubes is helpful. Evaluation of each patient before tube placement should include the patient’s medical history, nutritional assessment, and physical examination findings, all of which can help determine which type of tube to place.
Feeding tube types (named according to delivery route) include nasogastric, nasoesophageal, esophagostomy, gastrostomy, and jejunostomy tubes. Each tube type has advantages and disadvantages (TABLE 1).
When deciding which type of tube to place, the first consideration should be how long the tube will most likely be needed. If the answer is just a few days and if the patient can tolerate nasogastric or nasoesophageal feeding, one of those would be a good first choice. If the patient will require a tube for a longer time and is stable enough for general anesthesia, then an esophagostomy or gastrostomy tube would be a good choice, depending on the clinician’s level of comfort with tube placement.
2. Use Current Body Weight to Calculate Resting Energy Requirements
Calculate resting energy requirements ([RER] kcal/day) by using current body weight in kilograms (BOX 1). Although whether to use current versus ideal weight for obese patients is debated, the literature recommends starting with current body weight for all patients and then monitoring closely to ensure that the patient does not seem nauseated, vomit, lose weight, or have other adverse effects of feeding.6 The eventual goal for most hospitalized patients is 100% of RER (RER × 1); however, that amount may be too much or too little for some patients. Monitoring body weight and other parameters such as electrolytes for hospitalized patients is essential for fine-tuning feeding amounts.
3. Calculate Daily kcal Goal and Gradually Increase it to RER
Depending on the duration of anorexia or hyporexia, provide 25%, 33%, or 50% of RER on day 1 of feeding. There is no exact science for determining where to start, but a good rule of thumb is to use 50% if the duration of anorexia is <3 days, 33% if ~3 days, and 25% if >3 days. Unstable patients are at higher risk for metabolic complications during assisted feeding, and it is wise to increase calories per day and volume per feeding more slowly or to withhold feeding for 12 to 24 hours if the patient is hypovolemic or hypotensive.
Days 2 to 4
After selecting a starting point, plan to gradually increase to 100% of RER over 2 to 4 days, depending on the stability of the patient. Some patients may require a more conservative feeding plan if the feedings are not well tolerated.
4. Determine Feeding Frequency and kcal per Feeding
Feeding frequency is determined by hospital hours, staff availability, and patient tolerance of volume fed. Ideally, feeding frequency can be every 4 to 6 hours initially and later decreased to every 6 to 8 hours after it is clear that the patient can tolerate the feedings.
Kcal per Feeding
To determine the number of calories to give at each feeding, simply divide the total amount of calories intended for the day by the number of feedings per day. The kcal per feeding will gradually increase as the daily caloric amount approaches 100% of RER.
5. Select a Canned Diet, Liquid Diet, or Blend and Determine kcal/mL
Diets for enteral feeding can be commercially canned food, commercial liquid diets, canned diets blended with water, or canned and liquid diets combined into a blend. A diet for an enteral nutrition plan should be selected based on the patient’s problem list. TABLE 2 shows some diet options, but other options can be tailored to the individual patient. A tailored plan means that if the patient has a condition requiring a specific diet and nutritional profile (e.g., chronic kidney disease or pancreatitis), the diet should address that specific problem or the patient’s combination of problems. Typical critical care diets are high in protein and fat and may not be appropriate for all patients, especially those with dietary protein sensitivities or fat intolerance.
The chosen diet may need to be diluted depending on the patient, tube type, and tube size, although some diets can go through feeding tubes undiluted. Liquid diets will go through nasogastric, nasoesophageal, or jejunostomy tubes undiluted. For all patients with larger feeding tubes, select a pâté-style canned food rather than a chunky-style canned food.
Canned diets can be diluted with either water or an appropriate liquid diet. The benefit of diluting a canned diet with a liquid diet to create a blend is that the energy density of the blend will be higher than if water is used. For esophagostomy or gastrostomy tube feeding, approximately 50 mL of water or a liquid diet will dilute a smaller can of food (5 to 6 oz) and about 100 mL of liquid is needed to dilute a larger can of food (12 to 14 oz). However, dilutions will depend on the diet chosen, its moisture content, and the size of the feeding tube. Always mix the canned diet and dilution liquid in a blender. To ensure that the blend will flow through the tube without clogging, test it in an unused feeding tube (i.e., not in the patient).
After the diet and dilution liquid have been chosen, calculate the total kcal/mL of the feeding tube blend (BOX 1). If water is used to dilute a canned diet, note that the kcal in water is always zero. If a liquid diet is used for dilution, the kcal/mL can be found in TABLE 2 or in a product guide.
6. Calculate the Amount to Deliver at Each Feeding
After the kcal per mL of the blend or liquid diet is calculated (if needed), divide the kcal per feeding by the kcal per mL to get mL per feeding. This number will be the amount to give the patient at each feeding. Feedings should be given over 10 to 15 minutes, and the blend or liquid diet should be at room temperature when administered.
The maximum volume a patient can tolerate at each feeding can vary according to species and duration of anorexia but should start at no more than 5 mL/kg body weight per feeding.7 Some animals cannot tolerate even 5 mL/kg per feeding, but others can tolerate up to 30 to 40 mL/kg per feeding.8 Ensuring that the volume is tolerated and that the patient remains metabolically stable requires monitoring, including body weight, blood values (i.e., blood glucose and electrolytes), clinical status, and vital signs. If the patient does not seem to be tolerating the feeding or if the patient has signs of nausea, decrease the amount fed to that of the previous day. Similar to underfeeding, overfeeding has risks, so aggressive feeding is not ideal for most patients.
If the patient is discharged home with a feeding tube, the patient may need a new calculated feeding frequency and volume in addition to instructions for proper monitoring and care for the tube. The amount fed at the patient’s home will depend on the nutritional assessment and nutritional goals. Work up to this amount over time if the patient is not already being fed the goal for calorie intake. An advantage for clients is that feeding tubes can also be used to administer fluids and certain medications.
Although this step-by-step guide can help clinicians make enteral nutrition plans, it is just a starting point. Enteral nutrition plans can be tailored to each individual patient. Patients with feeding tubes should be re-examined for assessment of the tube site, body weight, body condition score, muscle condition score, and disease parameters. Although tube placement can be nerve-wracking for clinicians not familiar with feeding tubes, enteral feeding can positively influence patient outcomes and increase survival rates. Despite the possibility of tube-related complications, the benefits of feeding tubes and the provision of nutrition to critically ill patients generally outweigh the potential disadvantages.