Key Takeaways from the ISFM Guidelines on Management of the Inappetent Hospitalised Cat

Philip R Judge BVSc MVS PG Cert Vet Stud MACVS (Vet. Emergency and Critical Care, Medicine of Dogs)

Introduction

Inappetence is common in hospitalised cats. It can be caused by the underlying disease, pain, nausea, ileus, electrolyte abnormalities, medications and stress. It has significant consequences: delayed recovery from illness, impaired wound healing, reduced immune function and malnutrition. Because cats have high protein requirements and are vulnerable to stress in the hospital environment, they are at particular risk of malnutrition. The 2022 ISFM Consensus Guidelines on Management of the Inappetent Hospitalised Cat were produced by an international panel to provide practical, evidence-informed guidance on this problem. The guidelines cover nutritional assessment, correction of contributing factors, cat-friendly ward practices, appetite stimulants, feeding tube selection and placement, monitoring and refeeding syndrome. This review summarises the main recommendations and highlights the points most relevant to everyday clinical practice.

The Importance of Nutritional Assessment

Every hospitalised cat should get a nutritional assessment on admission, and every 12-24 hrs thereafter, when in hospital. The assessment should include:  

• Bodyweight: Weigh every patient daily and track trends over time
• Score Your Patient: Use both body condition and muscle condition scores together
• Obtain Nutrition History: Get a dietary history from the owner, including food preferences, as cats can be food neophobic – meaning they may reject novel foods in hospital
• Classify patients as low, moderate or high risk for malnutrition to guide how aggressively you intervene

Cats Are Not Small Dogs

Cats have higher dietary protein requirements; they can’t downregulate protein catabolism the way other species can, and lack the enzymatic flexibility to adapt to low-protein diets. Cats require approximately 40 essential nutrients from their diet. Essential nutrients include taurine, arginine, methionine, phenylalanine, histidine, lysine, tryptophan, threonine, leucine, isoleucine, valine, omega-6 linoleic and arachidonic acids, omega-3 EPA and DHA, fat-soluble vitamins A (retinol), D (cholecalciferol), E and K, water-soluble vitamins, and minerals. In addition, cats cannot adequately use beta-carotene as vitamin A, have low delta-6-desaturase activity, and cannot synthesise sufficient taurine, so those must come from exogenous sources. 

• Critically ill cats are often recommended 60–80 g protein per 1000 kcal.
• Aim to meet resting energy requirements (RER = 70 × BWt^0.75) using current cat body weight, not ideal weight
• Don’t add illness factors to the calculation – that practice is out
• Begin feeding to meet one-third RER on day 1, two-thirds on day 2, and full RER by day 3 if tolerated
• Overfeeding can cause hyperglycaemia, vomiting, diarrhoea, and refeeding syndrome. Close monitoring is essential

The Cause is Multifactorial

Anorexia is a feature of many diseases in the cat, but it may be caused or exacerbated by many other factors as well, including:

• Pain
• Fever 
• Nausea
• Intestinal ileus
• Dehydration
• Electrolyte abnormalities
• Constipation
• Medications
• Food aversion
• The hospital environment (odours, noise, anxiety/stress etc.) 

To adequately manage reduced appetite, a complete review of all predisposing or contributing factors must be considered. The following are recommended:

• Review the medication list. Medications associated with inappetence include
  • Antibiotics (penicillins, trimethoprim/sulphonamides, doxycycline, metronidazole, rifampicin, clindamycin)
  • Antifungals (itraconazole)
  • NSAIDs (meloxicam)
  • Opioids (methadone, morphine)
  • Diuretics (furosemide)
  • Chemotherapeutics (vincristine, cyclophosphamide)
  • Gastroprotectants (omeprazole)
  • Cardiac glycosides (digoxin)
  • Others (fluoxetine, mycophenolate, carbimazole, methimazole, ciclosporin).
• Score pain using a validated tool and treat it properly
• Correct electrolyte abnormalities
• Supplement with thiamine and cobalamin
• Treat nausea (even if the cat isn’t vomiting) Antiemetic options include
  • Maropitant 1 mg/kg SC, IV or PO q 24 h
  • Metoclopramide 0.25–0.5 mg/kg IV, IM, SC or PO q 8 h or 1–2 mg/kg IV over 24 h as a continuous infusion
  • Ondansetron 0.1–1 mg/kg IV, IM, SC or PO q 6-12 h
  • Mirtazapine 2 mg/cat PO or transdermal q 24 h, reduced to q 48 h in renal or hepatic disease.
• Manage constipation with laxatives or warm water enema; provide familiar cat litter

Stress Reduction and Cat-Friendly Care

Cats are territorial, place-bonded, selectively social, and can be easily overwhelmed by unfamiliar sights, sounds and smells. The hospital environment can cause sensory overload, lack of autonomy, inability to escape or hide, unfamiliar food, handling and exposure to other animals. Distress in the cat includes feelings of anxiety, fear, frustration and pain. Negative emotional states such as stress correlate with protective behaviours and reduced food intake.

Environmental stress reduction is a key component of the management of hyporexia/anorexia in the hospitalised cat. It has many facets:

• Move quietly and slowly; avoid direct approach or prolonged staring; avoid strong scents on hands, clothing or body.
• Use considerate, gentle restraint; never scruff or forcefully restrain; allow hiding, including during procedures; use a two-gentle-try/three-seconds-of-contact rule.
• Provide somewhere to hide and perch in every cage, such as a box, carrier, cat castle or cardboard box, or a towel hung halfway across the cage door.
• Face cages away from each other and avoid visual contact between cats; use a cat-only ward where possible.
• Line cages with newspaper or incontinence pads and use elastic bands to close doors to reduce metal door noise.
• Use feline facial pheromones; plug in diffusers 24 h a day in a low-down, wide-open area; pre-spray bedding, towels, clothing and carriers 20 minutes before the cat is present and refresh every 4 h as needed.
• Spot clean cages rather than replacing everything; include an item carrying the scent of the cat’s home or caregiver.
• Allow quiet time with lights off or dimmed, especially at night; use a dimmer switch or low-light torch.
• Offer small amounts of fresh food based on known preferences; remove uneaten food within 30 minutes unless the cat eats at night; separate food from litter trays and water bowls; offer food at room or body temperature; use wide-brimmed ceramic bowls.
• Do not introduce prescription diets while the cat is hospitalised
• Avoid force-feeding, syringe-feeding or wiping food on the cat.
• Use soft fabric Elizabethan collars that allow eating; supervised periods without collars may encourage intake.
• Maximise positive experiences with treats, quiet words, stroking or grooming if accepted, and aim for many positive interactions for every procedure.
• Provide enrichment such as play, puzzle feeders and problem-solving toys.

Appetite Stimulants

Mirtazapine (oral or transdermal) and Capromorelin are the two approved appetite stimulant options in cats. Indications include:

• Short-term use during diagnostic work-up
• Behavioural or environmental causes of inappetence
• As a supportive care measure in acute and chronic disease
• Cats showing some interest in food
• Cats eating but not reaching RER
• In cases where feeding tube placement is not an option. 

Contraindications for use include:

• Critical illness
• Active vomiting or nausea
• Physical impedance to prehension or ingestion
• In patients with inadequate pain management
• In patients with ileus. 

Appetite stimulants that have received evaluation for safety and efficacy in cats are outlined below:

• Oral mirtazapine:
  • Dose: 2 mg/cat PO q 24 h
  • In chronic kidney disease, use 1.88 mg PO q 48 h
  • In liver disease, the half-life may be prolonged, necessitating dose reduction
  • Reduce dose by 50% if behavioural side effects occur.
• Transdermal mirtazapine:
  • Dose: 2 mg applied daily to the inner ear pinnae
  • Achieves therapeutic serum concentrations and weight gain in cats with more than 5% unintended weight loss
  • Mild erythema at the application site occurred in 17.4% cats (versus 10.4% with placebo)
  • Daily dosing is appropriate for most chronic kidney disease patients
  • Clinical effect may be more subtle than oral due to a flatter concentration curve
  • Perfusion status and body temperature may affect absorption

• Capromorelin: ghrelin receptor agonist
  • Dose: 2 mg/kg PO q24h
  • In a clinical trial of 112 cats with chronic kidney disease and more than 5% weight loss, significant weight gain occurred over 56 days
  • Adverse events include vomiting, hypersalivation and lethargy
  • Contraindicated in acromegaly
  • Caution in diabetes due to hyperglycaemia
  • Transient bradycardia and hypotension have been documented
  • Avoid use if significant systemic compromise is present
• Cyproheptadine:
  • Not approved
  • 1–4 mg/cat q 12–24h
  • Anecdotal efficacy
  • Sedating
  • Not recommended in hepatic lipidosis
  • Takes days to reach therapeutic levels
  • It is the recommended antidote for mirtazapine toxicity, so the two drugs should not be used concurrently

Monitor effectiveness closely to avoid underfeeding or delaying more reliable nutritional support such as feeding tubes.

Feeding tubes

Indications for feeding tube placement include:

• Consuming less than 80% RER for 3 days or more, especially with involuntary weight loss
• Physical inability to consume adequate food due to jaw, oral cavity, pharynx or oesophageal disorders
• Anticipated inability to eat adequately after major surgery or during chemotherapy
• High risk of malnutrition or overt malnutrition
• Severe underlying disease
• To facilitate medication compliance. 

Enteral nutrition is preferred over parenteral in most cases because it stimulates gastrointestinal motility, enteric blood flow, local immunity, neuroendocrine pathways, favourable microbiota, reduces oxidative stress and has trophic effects on mucosal epithelium.

Methods of providing nutritional support via feeding tube include:

• Naso-oesophageal and nasogastric tubes: suitable for facilitating nutritional support for up to 3-5 days. These tubes are inexpensive, quick to place, require no specialised equipment, can be placed in conscious cats, are able to be used immediately after placement and are removable at any time. Their small bore lumen necessitates feeding of liquid diets only, as they are prone to obstruction. Additionally, the presence of the tube can impair voluntary food intake; and the necessity of an E-collar may cause stress to some patients. Contraindications to use include nasal disease, facial trauma, oesophageal disease, protracted vomiting, reduced mentation or poor gag reflex, and coagulopathy.
• Oesophagostomy tubes: are suitable for long term nutritional support. They are inexpensive, easy to place with practice, and require no specialised equipment. Being larger bore than nasogastric tubes allows increased diet choice, and the ability for medications to be crushed and given via the tube. These tubes are well tolerated, can be placed with head or nasal trauma or disease, are able to be used immediately after placement, are removable at any time, and can be used by caregivers at home. They do require general anaesthesia to place. They can become obstructed, and the stoma site can become infected. They require a collar or dressing that may cause stress. They are the preferred feeding tube for hepatic lipidosis, facial surgery, jaw fractures and pancreatitis.
• Gastrostomy tubes: These tubes are useful for long term enteral nutritional support. They are large bore, allowing for increased diet choice, and medication delivery. They are generally well tolerated and can be used by caregivers at home. Placement requires general anaesthesia, surgical or endoscopic equipment and training. Stoma site infection, tube migration and peritonitis are potential complications. Additionally, these tubes cannot be removed for 10-14 days following placement, and require a dressing that may cause stress. Primary indications for use include patients with oesophageal disease and long-term feeding requirement.
• Jejunostomy or nasojejunal tubes are rarely placed. They may be useful in selected severe disease such as pancreatitis, gastric disease, gastro-oesophageal reflux or refractory vomiting.

Tube maintenance includes:

• Check tube position before every feed:
  • Aspirate for negative pressure with naso-oesophageal or oesophagostomy tubes; aspirate acidic gastric content with nasogastric or gastrostomy tubes
  • Inject 5 ml air and auscultate for borborygmi, then inject 2 ml sterile saline and observe for cough or respiratory noise
  • Use of capnography to confirm tube placement in the oesophagus or stomach (no carbon dioxide) is useful, and testing of the pH of aspirated fluid to confirm gastric placement is useful, along with radiography to confirm tube placement prior to initial feeding f
• Flush with at least 2 ml water at body temperature before and after feeding; leave a column of water in the tube between feeds minimises risk of concretions forming within the tube lumen.
• If tube become obstructed, flush and aspirate with warm water. A solution of one-quarter teaspoon pancreatic enzymes and 325 mg sodium bicarbonate in 5 ml water left in the tube for a few minutes before flushing was effective in unblocking tubes in one study. Carbonated drinks were less useful than water.
• Clean stoma sites at least once daily with an antiseptic solution such as chlorhexidine, and check for infection or food leakage. Mild infection may be managed with increased cleaning frequency. Severe cellulitis or abscess may require systemic antibiotics, tube removal and possibly surgical debridement. Culture and sensitivity testing should be performed where possible. 

Tube use: 

• Feed 3–6 meals per day in small boluses over administered over 10–15 minutes. The maximum bolus volume should be no greater than is 5 ml/kg. Position the patient upright or with the head and neck supported in an elevated position above the stomach to avoid regurgitation.
• Monitor daily:
  • Body weight
  • Hydration status: Watch for overhydration, including chemosis, gelatinous skin turgor, clear nasal discharge, increased respiratory rate and crackles, especially with concurrent intravenous fluids
  • Vital signs
  • Stoma site. 
• Remove feeding tubes after voluntary intake has been adequate for 3–5 days

Refeeding Syndrome

Refeeding syndrome develops in patients that have severe muscle wasting because of prolonged starvation or catabolic disease. This results in shrinkage of body cell mass, and release of the intracellular cations, potassium, and magnesium, as well as intracellular anions including phosphorus into the extracellular space from where they are excreted in the urine. Refeeding syndrome also occurs in patients with depletion of one or more of the intracellular cations due to urinary losses in diseases such as diabetes mellitus, chronic kidney disease, or gastrointestinal disease. 

• Patients frequently have normal serum levels of these electrolytes despite an overall state of total body depletion. 
• When nutritional support is initiated in an electrolyte-depleted patient, these cations and anions rapidly shift into the re-expanding intracellular compartment due to the institution of anabolic metabolism and insulin secretion, and serum levels can fall dramatically within 1-2 days following feeding. Thiamine deficiency may also accompany the electrolyte abnormalities.
• The clinical syndrome is characterised by:
  • Weakness
  • Haemolytic anaemia
  • Acute respiratory failure
  • Myocardial dysfunction +/- arrhythmias
  • CNS depression and encephalopathy
  • Gastrointestinal dysmotility 
• Prevention includes feeding no more than 20% RER on day 1 and increasing slowly over 4–10 days. Supplement phosphate at 0.01–0.03 mmol/kg/h, potassium at 0.05 mEq/kg/h and magnesium at 0.01–0.02 mEq/kg/h for the first 24 h if electrolytes are not above the reference interval. Give thiamine 25 mg total SC or IM before feeding and daily until signs resolve. Stop feeding if refeeding syndrome is suspected.

Conclusion

Prompt multimodal management of the inappetent hospitalised cat improves outcomes. Nutritional assessment, correction of contributing factors, stress reduction, appropriate use of appetite stimulants and timely feeding tube placement are central. Delayed intervention because of clinician or caregiver apprehension may worsen nutritional deficits and hinder recovery. Enteral nutrition is preferred over parenteral in most cases. Refeeding syndrome prevention is important in severely debilitated or starved cats, and warrants careful attention to electrolyte status in at-risk patients.

References: 

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 Jul;24(7):614-40.

Taylor S, Bessant C. Inappetence in cats: the fifth vital assessment. Journal of Feline Medicine and Surgery. 2022 Jul;24(7):613-.