107 | Here's why your hospitalised cat won't eat (and what to do about it as a vet nurse)

Today we’re talking about probably the most common and frustrating nursing issue we encounter… but the most rewarding to fix - inappetent cats.

You know the ones - the ones who just won’t eat despite you having tried almost every flavour, texture and variety of food, in every type of bowl, warmed, not warmed, where you’ve pretended to eat it first, and practically begged them. And being cats, they’ve just given you the ‘look’ and turned away.

I’ve been there, we’ve all been there, and we’ve all been frustrated by it. So what can we do about it? The evidence is clear that inappetence is something needing prompt and careful management, and we’ve now got clinical guidelines to help us with this.

So sit back, grab a cuppa and together we’ll break down the 2022 ISFM Consensus Guidelines on Management of the Hospitalised Inappetent Cat, helping you get more of these patients eating, and use more of your skills.

Why is inappetence such a big problem in our feline patients, and what issues does it cause?

So before we get into the management side, I want to spend a few minutes talking about why cats are so uniquely vulnerable when it comes to nutrition. I know the phrase ‘cats are not small dogs’ is overused, but it really is true, and understanding the nutritional difference between them helps us better understand their needs.

Cats are obligate carnivores. Their metabolism has evolved around a diet that's higher in protein and lower in carbohydrate - essentially, small prey animals. And because of that, cats have what's called a lack of enzymatic adaptation to protein. In plain English: unlike dogs or humans, cats cannot downregulate their protein breakdown when food is scarce. Their bodies just keep burning protein regardless. So even after a relatively short period without food, they are already losing lean muscle mass.

For hospitalised cats - who are often already unwell, possibly in a catabolic state driven by disease and inflammation - this becomes a really urgent problem. The guidelines describe what they call 'stressed starvation,' where inflammatory mediators and sympathetic nervous system activation increase energy expenditure and accelerate protein breakdown, but without any adaptive reduction in metabolic rate. The result is a negative energy and nitrogen balance that impacts the cat's ability to do things like fight infection and recover from illness. In turn, this means longer hospitalisation, and potentially a higher risk of things like hospital-acquired infection.

Even though hospitalised cats are in this catabolic state, their overall energy expenditure is often actually lower than maintenance, because they're on cage rest, not moving around. So the goal isn't to feed them for their normal maintenance need, but to meet their current metabolic need. And this is generally their Resting Energy Requirement (RER), which is the calories needed to maintain homeostasis at rest.

We calculate it using the formula 70 multiplied by body weight in kilograms to the power of 0.75. That formula, by the way, is calculated on current body weight, not ideal body weight, and not admission weight if things have changed. This is really important because overfeeding has its own risks, including metabolic complications like refeeding syndrome, which we'll come back to later in the episode.

The guidelines also highlight some of the other unique nutritional considerations that make cats challenging - things like their inability to convert plant-based beta-carotene into vitamin A, their need for dietary taurine and arachidonic acid, and their more limited capacity to metabolise certain nutrients compared to other species. 

So from all of this, we can see how specific and unique the nutritional needs of our cats are, and how important it is that we meet them.

So now we know WHY nutrition is so important in our cats, HOW do we support it?

Well first, we need to look at why they stop eating.

There are more reasons for inappetence than you might think, and it's our job as nurses and technicians to be thinking about all of them for each individual patient.

The guidelines list a pretty comprehensive set of causes, but in hospitalised cats the big three non-specific factors are nausea, pain, and ileus - and then added on top of that, we have the stress of being in hospital. 

These factors often overlap, because a painful cat is more stressed, and a stressed cat may be more likely to experience nausea. A nauseous cat won't eat, and a cat that isn't eating is losing lean mass and becoming more vulnerable to complications. On top of that, we might be managing pain using potent opioids, which could impact GI motility, and predispose our patients to ileus. It all interacts to the detriment of our patient.

Nausea and its role in feline inappetence

Nausea is worth paying some extra attention to, because it isn’t always easy to spot especially in cats but it contributes to inappetence significantly when it’s present. Cats don't always vomit when they're nauseous - in fact, inappetence may be the only sign. Other subtle signs include ptyalism, which is excessive drooling or salivation, lip licking, and perhaps turning away from food or even subtle lip licking at just the sight or smell of it. All of these signs are worth looking out for and should prompt us to discuss antiemetics with the vet, if appropriate. 

How pain affects appetite in our hospitalised cats

Pain is another big one. A cat in pain is not going to eat, and yet pain is so easy to underestimate in feline patients because cats are brilliant at hiding it. This is where validated pain scoring tools, such as the Feline Grimace Scale or the Glasgow Composite Pain Scale are essential. We need to use these regularly, document the results, and communicate any changes in findings to our vets. And adequate multimodal analgesia, selected carefully to avoid side effects that themselves might cause inappetence (such as hypomotility, nausea or sedation), should be a priority.

Speaking of GI motility, we also need to consider ileus and its effect on appetite

Ileus - reduced or absent gut motility - is more common than we might think in our unwell cats, particularly those with critical illness, severe GI disease, pancreatitis, or certain hepatobiliary diseases such as hepatic lipidosis. 

Signs include nausea, abdominal distension, regurgitation, and discomfort. On ultrasound you might see reduced gastric contractions and fluid-filled stomach and intestinal loops. Management involves prokinetics like metoclopramide or cisapride alongside antiemetics and early (but careful) enteral nutrition where appropriate.

The impact of medications on appetite in cats

Another important area to highlight is the medications we use, and the impact these have. Because while we’re not making prescribing decisions as vet nurses, we are administering these drugs, and monitoring patients receiving them. 

We give cats a lot of drugs in hospital, and a significant number of them can cause inappetence. We're talking about many antibiotics - penicillins, metronidazole, doxycycline, clindamycin. NSAIDs. Opioids. Even omeprazole. Some of these are bitter-tasting, which creates a whole additional problem, as they make our patients feel worse and in turn they become less likely to eat. Cats can taste bitterness, and if a drug is bitter and we're giving it orally, we may be creating a negative association with eating that outlasts the drug itself.

So when you're looking at a cat that isn't eating, it’s worth looking at their hospital sheet and the medications they’re on currently. Perhaps we could speak to the vet and discuss whether any can be de-escalated, or whether a bitter-tasting oral medication could be put inside a gelatin capsule to mask the taste. Or whether there’s an injectable version we could give instead if appropriate. All of these things will help our patients feel better and increase their likelihood of eating voluntarily.

Dehydration and electrolyte abnormalities and their role in feline inappetence

And then there's dehydration and electrolyte abnormalities. Hypokalaemia is really common in critically ill cats and it's associated with both reduced appetite and ileus; where present, it will need managing with supplemented IVFT +/- enteral potassium supplementation, under veterinary direction. Cobalamin (vitamin B12) deficiency can also impact appetite, particularly in cats with GI disease, and again this may need to be corrected under veterinary direction.

How does the hospital environment impact appetite in cats, and what can we do about it as vet nurses?

Stress is probably the most underappreciated factor impacting appetite in hospitalised cats, and it's also the area where we make the biggest difference as nurses and technicians.

Cats are solitary and territorial, and highly bonded to their environment. In the hospital, they’ve been removed from their territory and are housed in an unfamiliar space with unfamiliar smells, sounds, and people. There may be dogs nearby. There may be other cats they can see or smell. They have no control over when they're handled, when the lights go on, when strangers come into their space. Their routine is completely disrupted. Their food might be different. Their bowl might be different.

We know that a cat in a state of high emotional arousal is less inclined to eat. And while I know a lot is said about stress in cats, the truth is that stress is not just an inconvenience for these patients; it is a genuine problem that affects appetite, recovery, wound healing, and immune function. Stress management is a clinical need, and one we’re ideally placed to take the lead on as nurses and technicians.

How to minimise stress and improve your cat’s chances of eating in hospital

We need to consider their kennel environment first - things like opportunities for hiding, and resource management. First up, hides - every hospitalised cat needs somewhere to hide, not necessarily fancy, it could just be a cardboard box or their own carrier placed inside the kennel, but they need the opportunity to hide away on their own terms. 

Resource placement within the kennel also matters. As far as we can, separate resources and get distance from their toileting facilities and their food and water. And where possible, separate the food and water from each other if you can, and avoid using ‘double-diner’ bowls. 

Try and reduce the sight and smell of other patients as much as possible - other cats as well as other species - as anything we do to help minimise perceived threat and calm our patients will also improve their willingness to eat. For the same reason, feline facial pheromone diffusers should be considered.

How to pick the right food for your hospitalised cat (and how to actually feed them)

When it comes to food, the guidelines are quite specific. Offer small amounts of fresh food regularly - ideally based on what you know the cat eats at home. We spoke about this in episode 106, but wherever you can, collect a dietary history from the client. 

A cat that normally eats a specific brand or texture of wet food may not appreciate something completely unfamiliar, especially when they’re already feeling rubbish. 

Neophobia - which is a dislike of novel foods - is an issue in cats, and introducing prescription diets while the cat is hospitalised and nauseous or in pain can create lasting food aversions that persist long after discharge. The guidelines are very clear about this: do not try to introduce prescription diets while the cat is in hospital, because there’s a high likelihood of aversion. Instead we need to transition them to a new diet (if clinically indicated) gradually, at home, when they're feeling better.

We also need to consider the bowls we use - which sounds basic but in reality is fundamental. Wide, flat, ceramic bowls are ideal, because they avoid whisker fatigue which can cause discomfort,, and they don't taint the food with metallic or unpleasant smells the way metal and plastic bowls can. Offer food at body or room temperature, not fridge-cold, and remove uneaten food within about 30 minutes to keep it fresh and avoid negative associations.

The other thing the guidelines are clear about is force-feeding. And by force-feeding I mean both syringe feeding and wiping food on the cat’s nose in the hope they’ll lick it off. These approaches (even though well-meaning) can cause stress and in severe cases, profound and lasting food aversion which can be difficult to reverse.

One last thing on the topic of stress management and general nursing care: the number of interactions, checks, treatments and handling events is important. In many cases, fewer is better. Every time we open the kennel door for a check, a heart rate, a medication, a bandage change or any other procedure, it's a stressor. Try to batch observations and interventions where you can, and aim for a ratio of many positive interactions (such as a treat, a fuss if accepted, or other forms of TLC) for every one occasion that requires a procedure. This will help build a relationship with your patient, and improve their willingness to eat.

And once we’ve covered those fundamentals, we need to assess our patients and make their feeding plan.

Now I’m not going to go into nutritional assessments in too much detail because we did that last week in episode 106, so definitely go back and listen to that one if you haven’t already. But what I will say is this: just like the AAHA Nutritional Guidelines and the WSAVA Nutritional Toolkit say, nutritional assessment is vital. It’s the fifth vital sign, and should be performed for every patient, every visit. This means collecting a dietary history, completing at least a screening evaluation +/- extended evaluation, and measuring weight, BCS and MCS.

We need to calculate RER (or a percentage of it, depending on the individual patient), track the food offered, and track their intake - regardless of whether they have a feeding tube in or not.

And in our hospitalised cats, their nutritional assessment should be repeated regularly - at least daily, as we discussed in episode 106. And, just like we said in that episode, escalation, including feeding tube placement, needs to happen after no later than 3 days of anorexia.

When do we use appetite stimulants in our hospitalised cats, and how do they work?

The next thing we need to talk about is appetite stimulants - because they’re used really often, and sometimes inappropriately, and a big part of our role as nurses is understanding when they should (and should not) be used.

There are two licensed appetite stimulants for cats at the moment. Mirtazapine, available as an oral tablet or the transdermal formulation applied to the inner ear pinna; and capromorelin, licensed under the name Elura in the US and currently licensed in Europe too.

Let’s talk about giving mirtazapine to our inappetent cats

Mirtazapine is probably the most commonly used. This drug acts as both an appetite stimulant and an antiemetic and is usually given at a dose of 2mg/cat once daily. The transdermal version achieves therapeutic serum concentrations, though the effect can be slightly more subtle than oral. In cats with chronic kidney disease, clearance is slower, so the dose is usually adjusted (sometimes to every 48 hours). In cats with hepatic disease, the half-life is prolonged too, so dosing needs to be considered carefully. Side effects to watch for include vocalisation, agitation, cardiovascular changes (in severe cases), and erythema at the application site for transdermal use.

And then there’s our newer appetite stimulant - capromorelin.

Capromorelin is a ghrelin receptor agonist, which stimulates appetite by mimicking ghrelin, which is the hunger hormone. 

It's dosed at 2mg per kg orally every 24 hours. It's been shown to be effective for weight gain in cats with CKD, but there are important contraindications: it shouldn't be used in cats with acromegaly, and caution is needed in diabetic cats because it can cause hyperglycaemia. 

Transient bradycardia and hypotension have also been documented, so it's generally not recommended in significantly systemically compromised patients, such as our more critical patients.

Regardless of which your vet prescribes, appetite stimulants are a useful tool, but they are not a substitute for identifying and treating the underlying cause of inappetence. Before you reach for the appetite stimulant, nausea, pain, and stress need to be addressed. An appetite stimulant given to a cat that is still nauseous, or still in pain, or really stressed, is not going to work - and worse, it might give a false reassurance that the cat is being managed because they’re eating SOMETHING, when in reality they’re not eating nearly enough.

Another important point mentioned in the guidelines is that appetite stimulants should not delay the placement of feeding tubes. So if appetite stimulants aren't working, or if the cat has clear indications for a tube, we shouldn’t wait.

Speaking of feeding tubes, which should we place in our anorexic cats, and how are they managed?

Feeding tubes are an essential tool in the inappetent cat (and dog!) and still underused in practice.

I think there is sometimes apprehension about recommending or accepting a feeding tube. It can feel like an escalation, like things are getting worse, and for our clients it can feel quite scary and invasive (and I say this having had my old kidney cat Nigel at home with an O tube in for several weeks). 

But the evidence tells us the opposite is true. Early intervention with enteral nutrition supports gut motility, gut immunity, mucosal integrity, and immune function. It reduces catabolism and stops our patients breaking down lean body mass. And it allows us to give medication reliably, which is a huge practical benefit, especially for cats requiring prolonged treatment courses. In fact, even if a cat is eating again, keeping the tube in for medication use at home can make treatment SO much easier for clients.

So let's run through the different types of tube, and briefly recap their use.

Placing nasal feeding tubes in our hospitalised cats

Naso-oesophageal or nasogastric tubes (NO or NG tubes) are the go-to for short-term feeding, generally up to about five days, or in cats where anaesthesia isn't possible. 

The huge advantage is that they can be placed in a conscious or lightly-sedated patient with just a local anaesthetic to the nose, which means they're available almost immediately. 

The downsides are that they're small bore, so diet choices are limited to liquid consistencies. 

In some cases (not all) they can interfere with the cat's ability to eat voluntarily, and some cats are bothered by them. 

They need to be checked before every single feed to confirm correct placement, because vomiting can dislodge the tube into the trachea, and accidental tracheal feeding causing aspiration pneumonia is a serious complication. 

Using oesophagostomy (O) tubes to manage inappetence in feline patients

Oesophagostomy tubes (O tubes) are my personal favourite for medium to long-term feeding, and I think they're still quite underused in practice. 

They require general anaesthesia to place, but once they're in, they are brilliant. 

They’re larger bore, so a wider variety of diets can go down them. Medications can be crushed and given via the tube. 

They can also be used at home, which means cats can be discharged earlier; this is really important for recovery, because being at home in a familiar environment is going to reduce stress and we know that stress drives inappetence.

Complications include stoma site infection in roughly 12 to 18% of cases, and tube dislodgement. Stoma sites should be cleaned at least once daily (ideally twice daily in hospital and once daily at home) with antimicrobial solution, inspected carefully, and any signs of infection should be managed.

The we have our other options: gastrostomy tubes, and (rarely) jejunostomy tubes.

Gastrostomy tubes (G or PEG tubes) are used for longer-term feeding, particularly in cats with oesophageal disease. They're large bore and very well tolerated, but they require surgical or endoscopic placement, and they cannot be removed for at least 10 to 14 days to allow a seal to form at the gastrostomy site.

Jejunostomy and nasojejunal tubes are rarely used in cats. In fact, I’ve only ever seen one placed and that was in a dog - so we’re not going to go into detail on them here. However, they exist as an option for specific cases.

And then there's parenteral nutrition (intravenous nutrition) for cats who genuinely cannot tolerate enteral feeding (and by ‘can’t tolerate’ I mean that their GI tract can’t tolerate it, not that they won’t eat). This is more specialised, more expensive, and associated with higher complication rates, so enteral feeding is always preferred. If the gut works - use it!

Once we’ve got a feeding tube in our patient, we need to create a feeding plan and manage their tube.

Once a feeding tube is in place, it’s our role to create the patient’s feeding plan (under direction), use the tube, and manage it carefully.

Before we start feeding, out patient should be haemodynamically stable, rehydrated, and have had major electrolyte abnormalities corrected. In a critically unwell patient, that means stabilising them first before considering introducing nutrition.

Then, start low and go slow if your patient has been inappetent. We don’t want to go straight in with 100% RER in a patient who has not been eating; instead, we need to reach that 100% RER gradually, depending on how long the patient has been anorexic for. 

While in many cases we use 3 days to refeed - 33% on day 1, 66% on day 2, and 100% on day 3 - this may need to be extended in patients who have not eaten for longer than 3 days.

Feeding can be given as bolus meals (most cats tolerate three to six bolus feeds per day) or as a constant rate infusion via a syringe driver for cats who struggle to tolerate bolus volumes. Monitor for signs of intolerance: lip licking, excessive swallowing, gagging, retching, vomiting, or restlessness. If any of these occur, stop and reassess.

Before using the tube, we need to check the position carefully, flush the tube before and after feeding, and stop and re-check the tube if any complications arise. Stoma sites for O tubes and gastrostomy tubes should be cleaned regularly and assessed for infection, and every feed should be recorded accurately - including what went in, any complications, how the cat responded.

In most cases, we can (and should!) keep offering voluntary food alongside tube feeds. Just because there's a tube doesn't mean we stop trying to get cats eating on their own. Offer food before you tube feed, and if they eat SOME food, subtract that number of calories from their tube feed to avoid overfeeding. 

Once the patient has been eating voluntarily at 75 to 100% of RER consistently for three to five days, that's when you can start thinking about tube removal.

The importance of preventing refeeding syndrome in inappetent cats

Refeeding is a rare but serious complication that nurses need to be aware of. In cats who have been anorexic for extended periods, like cats that have gone missing, or cats with significant disease such as hepatic lipidosis, reintroducing nutrition too rapidly can trigger a life-threatening metabolic crisis. 

Refeeding these patients inappropriately can cause an insulin surge that drives glucose, phosphate, potassium, and magnesium into cells, causing significant electrolyte abnormalities. Signs include neurological changes, weakness, haemolytic anaemia, and cardiovascular instability.

A big part of our role as veterinary nurses is looking out for these at-risk patients, and considering their refeeding plan even more carefully. These patients include those who are severely emaciated, have had extended (5-7 days+) starvation, or who have significant electrolyte abnormalities before we start feeding them. 

In these cases, the recommended approach is to start at no more than 20% of RER on day one, and increase very slowly over 5-10 days while monitoring electrolytes closely. Electrolyte supplementation is recommended based on the individual patient and their blood results, and thiamine (vitamin B1) should be given prior to feeding. If we suspect refeeding syndrome is developing, we need to stop feeding and stabilise the patient before reassessing the plan. This shows the importance of ongoing reassessment, even after we’ve placed the feeding tube - and of course, as nurses and technicians our role in this cannot be overlooked.

So let’s bring all of this together and summarise our role in nursing inappetent cats in practice.

The inappetent hospitalised cat is one of the most common, perhaps most frustrating, but ultimately most rewarding patients we see as nurses and technicians. That being said, I hope today’s episode has reminded you how much we can do to make a real difference for these patients.

Assess nutrition as the fifth vital sign, every day, for every patient. Think about all the contributors to inappetence - nausea, pain, ileus, dehydration, electrolytes, medications, stress. Create a cat-friendly environment. Use validated pain scores. Get a dietary history. Offer familiar food in appropriate bowls at the right temperature. Don't force-feed. Consider appetite stimulants thoughtfully. Advocate for early feeding tube placement. And depending on the type of tube, even place it - this is a great use of our nursing skills.

And lastly, don’t underestimate the importance of your role in all of this. We are the ones in the wards caring for these patients. We’re the ones noticing that they’ve started turning away from food. We’re the ones noticing that they’ve lost weight again today. We’re the ones who see that the stoma site looks a little angry. Our role makes all the difference, and I hope today has given you some new ways to approach these patients.

Did you enjoy this episode? If so, I’d love to hear what you think. Take a screenshot and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!

References and Further Reading

• Taylor S, Chan DL, Villaverde C, Ryan L, Peron F, Quimby J, O'Brien C, Chalhoub S. 2022 ISFM Consensus Guidelines on Management of the Inappetent Hospitalised Cat. Journal of Feline Medicine and Surgery (2022) 24, 614–640.