Critically Ill Patients: How to Feed

Part 2

If the gut works, use it!

Feeding via the enteral route is preferred in the presence of a functioning gastro-intestinal tract. Gut cells receive approximately 40% of their nutrition from digesta in the lumen of the gastrointestinal tract. Therefore, when critically ill patients are not fed enterally, there is loss of mucosal cell mass. There is also impaired gastrointestinal function, rendering the gut more susceptible to damage and bacterial translocation.^[1]

1. Offer food for voluntary consumption before enteral feeds in selected patients. Monitor food and calorie intake, along with body weight and if energy and nutrient requirements are not being met, select another route.
2. Syringe feeding of blended slurries may work, but requires repeated handling and manipulation of the animal, and risks aspiration and a grumpy patient! Inadequate calorie consumption is a risk, as more food ends up on, rather than in, the patient. It is critical to minimise stress in ill animals, so select the feeding method that causes the least discomfort. This may mean feeding by an indwelling tube rather than force feeding boluses, syringe feeding or repeated intubations.
3. Tube feeding includes nasoesophageal and nasogastric tubes, or surgically placed tubes such as oesophagostomy, gastrostomy and jejunostomy tubes. It is common to use a nasoesophageal tubes for nutritional support lasting 4 to 7 days, whereas gastrostomy tubes are more commonly used for long-term support for weeks to months (e.g. cats with hepatic lipidosis).
   • Many veterinary nutritionists consider oesophagostomy tubes to be the most useful and effective feeding tube. Consider placing an O tube in the majority of critically ill patients in intensive care and those at risk of malnutrition.  They are easy to place (requiring only a short general anaesthetic), simple to manage and can be left in for weeks or months.

Principals of tube feeding³

• Heat up refrigerated food to room temperature in a bowl or jug of hot water before feeding. Microwave ovens can cause uneven heating, and I don’t recommend them for this reason.
• Infuse the bolus slowly over 1 minute to allow the stomach to expand.
• Split the daily volume into several smaller meals, depending on the stomach capacity.
• The stomach capacity of cats and dogs is initially 5 to 10 mL per kg but can increase to 45 mL per kg (cats weighing 4-6 kg) and 90 mL per kg (dogs) once the feeding regimen is established.
• Salivating, gulping, retching or vomiting may indicate infusion of too large a volume of food, or that it has been infused too quickly. Check tube placement as it may also mean that the tube is displaced.
• Stop feeding at the first sign of salivating, gulping, retching or vomiting. Decrease the meal size by 50% for 24 hours, and then increase gradually by 25% daily.
• Follow all infusions with a water flush of the tube volume only. Remember to meet the animal’s requirements for water.
• Clear blocked feeding tubes by filling the tube with water or a carbonated drink. Allow time for the food plug to dissolve, or insert a stiff urinary catheter into the feeding tube.

How much to feed?

Feeding plans require an understanding of the critically ill patients metabolic state relative to changes in metabolism resulting from ongoing food deprivation. Feeding more of any food than is necessary may cause metabolic complications.

Initially, offer the daily food intake that supplies the calories determined for cage-rest. Calculate the approximate caloric needs from the following equation for Resting Energy Requirement (RER):

RER (kcal) = 70 x (Current Bodyweight)^0.75

• In patients that have not eaten for several days, do not start supplementation at the full RER.
• Give only 1/3 of the estimated energy requirement on the first day, divided into several small meals or boluses.
• Increase the amount to 2/3 on the second day if this is well tolerated, and give the entire amount on the third day.
• Decrease the rate and/or volume if there are any signs of drooling, retching, swallowing or vomiting during feeding.

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References:

1. Remillard RL, Darden DE, Michel KE et al. An investigation of the relationship between caloric intake and outcome in hospitalized dogs. Vet Ther 2001; 2: 301-310
2. Saker KE, Remillard RL. Critical Care Nutrition and enteral-assisted feeding. In: Hand et al, editors. Small Animal Clinical Nutrition. 5th edn. Mark Morris Institute, Kansas, 2010: 439-476
3. Burns K, Yagi K. Nutrition as a life saver in critical care. NAVC Proceedings Veterinary Technician 2017 45-47