Why good quality nutrition is vital when caring for your medical patients
I don’t need to tell you that nutrition is one of the most important parts of nursing care.
As veterinary nurses, it’s our job to advocate for our patients. A great way we can do this is by working with the vet to create a tailored nutritional plan. This should include:
A nutritional assessment
Calculating the patient’s energy requirements
Placing a feeding tube if required
Selecting an appropriate diet for the patient’s disease and life stage
Creating the feeding plan
Monitoring the response to feeding and adjusting the plan as required
This is especially important for our medical patients. They have a host of complex diseases and comorbidities often requiring specific nutritional management. In addition, lots of our patients present with inappetence, anorexia and weight loss as part of their disease.
But how do we do this? In this post, I’m going to share exactly how to calculate your patient’s energy requirements, look at tempting vs feeding tubes, and we’ll touch on what to do when your patient can’t have enteral feeding.
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Why is enteral nutrition important?
Early enteral nutrition is absolutely vital when treating so many different medical conditions!
When our patients don’t eat (or don’t eat enough) for prolonged periods, they start to break down their own body tissues to provide energy for cellular processes. By providing early enteral nutrition, we are able to prevent (or reverse) this process.
Providing enteral nutrition also allows us to deliver nutrition directly to the enterocytes. Our enterocytes line the intestines and get their nutrition directly from food.
If we don’t feed via the enteral routine, these cells don’t get nutrition. This can compromise the intestine’s barrier ability - their ability to keep bacteria in the intestinal lumen, and out of the bloodstream!
So, we know that enteral is best - and in order to make our enteral plan, the first thing we need to do is calculate our patient’s energy requirements.
Calculating energy requirements
There are a number of different ways we can calculate energy requirements for our patients. The first, and the one we're most familiar with, is resting energy requirement or RER.
Resting energy requirement
A patient's resting energy requirement is the amount of energy needed to maintain essential physiological processes in the body in a thermoneutral environment. When we say essential processes, think digestion, respiration, cardiac function and brain activity.
There are two ways to calculate this: the linear formula, and the allometric formula.
Linear formula: kcal/day = bodyweight (kg) x 30 + 70
Allometric formula: kcal/day = bodyweight (kg)^0.75 x 70
The linear formula is easier to calculate but not quite as accurate, especially in very small or very large patients (<2kg or >30kg). The allometric formula is technically more accurate but requires a scientific calculator (or a smartphone turned on its side!) to work it out.
Daily energy requirement
RER is different to a patient's daily energy requirements or DER (also called maintenance energy requirements/MER). The DER takes into account activity, life stage and things like growth, pregnancy and lactation. By incorporating these lifestyle/stage factors, we can more accurately assess calorie requirements in some of our patients where appropriate.
What we don't do anymore is use illness factors. The reality is that there is no 'one size fits all' when it comes to managing nutrition for different diseases, and we run the risk of overfeeding in many unwell patients - and this comes with potential metabolic consequences and risks things like refeeding syndrome.
This means starting with their calculated energy requirements only, and feeding them for their current bodyweight - not their ideal weight or a previous weight pre-illness, during their hospitalisation.
Monitoring response to feeding
The amount of food offered to your patient at each meal should be measured and recorded in grams. Any remaining food should be weighed and recorded prior to disposal. Each day, the number of calories consumed can then quickly be totalled up and expressed as a percentage of the patient's RER/DER (whichever is most appropriate for the individual patient).
We also want to weigh our patients at least daily, monitoring for any weight loss or gain. Body and muscle condition scoring should also be performed regularly.
A note on calculations…
Regardless of the calculation you use, it's important to remember they're all guidelines and not exact figures that fit every patient. There will be some variation amongst individuals, and it's important to regularly assess weight, body condition and muscle condition, and continue adjusting your patient's nutritional plan as needed.
Delivering nutrition
We have two options when it comes to managing inappetence - tempting, or tubes.
Tempting
Our options for very recent anorexia or hyporexia (eating less than normal), or where we feel we can get the patient eating easily/soon with us, include:
Managing pain and nausea which could contribute to anorexia
Minimising stress in the hospital
Offering a variety of palatable foods (not at the same time!)
Using appetite stimulants such as capromorelin or mirtazapine
Trialling some alfresco dining (or out-of-kennel dining!) and some good old TLC
The one thing we really want to avoid is syringe feeding. It doesn’t deliver enough calories, risks aspiration, compromises our patient’s wellbeing in the hospital and can cause food aversion, making them less likely to eat voluntarily for us
This means that any patient who has been inappetent or anorexic for 48-72 hours (or who is not expected to eat for a 72-hour period) should have some kind of enteral feeding tube considered.
Feeding tubes
There are a few options when it comes to tube feeding, including:
Naso-oesophageal tubes
Nasogastric tubes
Oesophagostomy tubes
Gastrostomy/PEG tubes
Jejunostomy tubes
The best one to use depends on the individual patient, their disease process, how long you expect to feed for, and their temperament.
Nasoesophageal tubes
These tubes are easy and quick to place and can be placed in conscious (or lightly sedated) patients.
They are generally well tolerated for short-term feeding, but are only suitable for very liquid diets, as most tubes are small in diameter.
Placement of nasal tubes is contraindicated in facial/nasal disease/trauma, vomiting and sneezing patients.
Nasogastric tubes
Many considerations for NG tubes are the same as NO tubes, but with nasogastric tubes, the tube extends into the stomach rather than the mid-oesophagus.
They are useful in parvovirus patients and patients with ileus, to aspirate acidic stomach contents and reduce residual gastric volumes. They can also be used in gastric dilation cases to decompress the stomach.
Oesophagotomy tubes
Oesophagostomy tubes are larger bore tubes which allow thicker foods to pass through. They are useful in cases requiring short-medium term feeding but require general anaesthesia for placement.
They are contraindicated in patients with oesophageal disease, and need to be used carefully in vomiting patients (ensuring the patients are receiving antiemetics and not continuing to vomit).
As the tube is surgically placed, the site needs to be inspected, cleaned and redressed at least daily, to minimise the risk of a tube site infection.
Patients can be discharged with the tube in for at-home feeding, which is a huge plus for our medical patients! This is also a great opportunity for us to get involved with client education and support, showcasing our knowledge and skills as RVNs!
Gastrostomy tubes
Gastrostomy tubes are indicated in oesophageal disease (e.g. post foreign body). They are large bore tubes allowing gruel-consistency foods to be fed (e.g. blended wet food).
These tubes are suitable for long-term feeding (months to years) and are placed one of two ways, - either surgically, or endoscopically.
Endoscopic tubes are known as PEG tubes (percutaneous endoscopic gastrostomy tubes) as they are placed through the skin with the assistance of an endoscope.
After placement, the patient cannot be fed via the tube for the first 24 hours, to allow a seal to form at the site, and help avoid peritonitis. The tube must not be removed before 7-14 days post-placement for the same reason. Daily site inspection and dressing changes are required, just like any other surgically placed tube.
Jejunostomy tubes
Jejunostomy tubes enter the GI tract directly in the middle of the small intestine. They are very rarely used. They can be indicated in gases of gastroduodenal disease, where we need to bypass this portion of the GI tract (called post-pyloric feeding).
J tubes are placed either surgically via a laparotomy directly into the jejunum, or via a G tube (called 'J-through-G').
J tubes are very narrow tubes permitting liquid diet administration only. We also have to administer these diets only as a constant trickle feed, as the jejunum can’t stretch like the stomach can - meaning no large meals!
We often see diarrhoea in patients on J tube feeding, because the food is bypassing the stomach and duodenum, which is where most of digestion happens!
Parenteral nutrition
What about when patients won’t tolerate enteral nutrition?By tolerate - I don't mean they won't eat. I mean that we're not able to get any (or enough) calories into them via a feeding tube.
In these cases, we have to look for alternatives - like parenteral nutrition (PN)!
This is something we might reach for in patients with horrible ileus, for example, where their GI tract just won't move and any food we give, even a little trickle through an NG tube, just backs up in the stomach causing regurgitation. It's not without risk, though, and these patients need intensive management. This means it’s really important for us, as RVNs, to be familiar with the considerations, complications and monitoring requirements for PN patients.
So what is parenteral nutrition?
Parenteral nutrition solutions are solutions containing glucose, electrolytes, amino acids and lipid for intravenous infusion. They provide a source of calories for patients who aren't able to consume enough enterally.
Parenteral nutrition (PN) is generally only used in a specialist setting. The solutions must be administered through a central venous catheter, because the 11% glucose content causes high osmolarity. This osmolarity causes phlebitis when administered through a peripheral vein.
How is it prepared?
To prepare parenteral nutrition, we first need the following:
Sterile PN bag
Sterile gloves
Giving set
1.2 micron lipid filter
Extension line
Disinfectant IV port caps
Tape
Spirit/chlorhexidine swabs
A plain sterile drape
Here’s how to prepare your solution.
Pop the bag to mix the three separate compartments (lipids, amino acids/electolytes and glucose).
Glove up and aseptically connect your giving set, filter, and extension line together. I like to do all of this on a plain trolley drape to give myself a sterile surface to work on.
Insert the giving set into the PN bag and run the line through.
Cover any IV ports with disinfectant caps and cover with tape, to stop the line being broached with a needle or syringe.
Wrap any joins in the lines (where one line joins to another) with spirit or chlorhexidine swabs and wrap with tape/bandage.
Aseptically attach the line to your patient and run it
Label the bag with the date and time of opening and expiry.
Nursing the PN patient
Patients receiving PN need careful aseptic technique whenever they (or their PN bag/line) are handled. Bags and giving sets should be changed daily, as bacterial contamination of the solution is a particular risk. It’s intravenous food, after all - and it feeds bacteria just as well as people!
Sterile gloves must also be worn when handling the patient’s catheter or line, and the patient should not be disconnected from their PN line at any time.
Remember we said that enteral feeding nourishes our enterocytes, maintaining the intestinal barrier? Well, PN does not do this. This means that compromise to the gastrointestinal barrier can occur with prolonged use, risking bacterial translocation and sepsis.
If possible, patients should receive partial parenteral nutrition, to supplement any amounts they are able to receive enterally - this way, some nutrition is still delivered to those intestinal cells.
Refeeding syndrome
Refeeding syndrome is an uncommon but serious complication we can see in our medical patients. The most common disease it’s associated with is hepatic lipidosis, but it can be seen in any condition causing severe or long-term anorexia.
It is associated with not restricting (or not restricting enough) food intake in a long-term or severely anorexic patient. Picture this…
A stray cat is brought into your practice by a member of the public.
You scan the microchip and find they’re already registered with you, but they weigh half the last weight on their record and are barely recognisable.
The client collects their cat, explaining they have been missing for 9 months.
When they arrive home, the client (understandably!) starts feeding up their cat, as much as they would like to eat, to get them back to normal.
Understandable, right?
But during this time, our patient’s body has adapted to their reduced calorie intake - and they’re then at a high risk of refeeding syndrome if they are fed a ‘normal’ amount straight away.
How does refeeding syndrome work?
During periods of prolonged anorexia, the body adapts to a reduction in food intake by entering a catabolic state. In this state, the body uses protein as its main energy source. The patient also reduces their metabolic rate, cardiac output, gastrointestinal motility and other metabolic functions, to save energy.
During refeeding, the body shifts into an anabolic state, using carbohydrates as the primary energy source, which causes insulin to be released. The insulin release then causes various electrolyte abnormalities such as hypophosphataemia, hypomagnesaemia and hypokalaemia - because insulin drives these electrolytes out of the bloodstream and into cells.
This causes signs such as haemolysis and anaemia, weakness, hypoperfusion and white blood cell dysfunction. In addition, we have a body in ‘slow down mode’, where cardiac output is reduced. This puts our patient at a high risk of fluid overload as soon as we start treating them with IV fluids and electrolyte supplementation!
In order to prevent refeeding syndrome, enteral feeding should be reinstated gradually, over at least a 3-4-day period, depending on the duration of anorexia.
In patients deemed at risk of refeeding syndrome (e.g. patients with marked weight loss and chronic anorexia lasting over 7 days) enteral feeding should be introduced extremely gradually and beginning at under 20% of RER.
Monitoring of phosphorus, potassium, packed cell volume, total solids and magnesium levels should ideally be performed daily in patients at increased risk of re-feeding syndrome, beginning within 12 hours of feeding.
As you can see, there is a LOT to think about when it comes to nutrition in our medical patients, and these patients give us so many opportunities to use new nursing skills!
If you want to learn more about how to do more with your medical patients, sign up for the VIMN weekly newsletter here and get bonus access to a webinar teaching you how to do just that!
References
American Animal Hospital Association, 2021. AAHA 2021 Nutrition and Weight Management Guidelines. Available from: https://www.aaha.org/aaha-guidelines/2021-aaha-nutrition-and-weight-management-guidelines/home/
Chan, D. Nutritional Management of Hospitalised Small Animals. Oxford: Wiley-Blackwell, 2015.
Olson, M. 2022. Energy Calculations: Gauging the Proper Caloric Intake for Patients. Today's Veterinary Nurse.
Merrill L. 2012. Small Animal Internal Medicine for Veterinary Technicians and Nurses. Iowa: Wiley-Blackwell.
Wara A, Datz C. 2014. Enteral Nutrition: Tube Feeding. Clinician’s Brief. Available from: http://www.cliniciansbrief.com/article/enteral-nutrition-tube-feeding
World Small Animal Veterinary Association Nutrition Toolkit: https://www.wsava.org/nutrition-toolkit
