How to provide early enteral nutrition in the canine pancreatitis patient

There are many practical skills s registered veterinary nurses (RVNs) can utilise in primary care practice. Nursing cases such as canine pancreatitis can lead to many challenges for the veterinary team. Nutrition is a vital part of the nursing care, and the placement of a nasogastric (NG) feeding tube can have endless benefits. This article will help veterinary nurses to understand the pathophysiology of canine pancreatitis, the benefits of early assisted enteral nutrition and how to successfully place a NG feeding tube.

Anatomy

The pancreas is a flat, long, abdominal organ (Thomas Colville, 2016), which sits adjacent to the stomach. The pancreas is connected to the duodenum (the first portion of the intestine) via the pancreatic duct. Most of its mass is made up of exocrine glandular tissue, which produces digestive enzymes (Thomas Colville, 2016). These digestive enzymes flow from the pancreas via the pancreatic duct when food leaves the stomach and enters the duodenum. This helps break down food for absorption through the small intestine.

The endocrine portion of the pancreas is organised into thousands of tiny clumps of cells scattered all over the organ. These are called pancreatic islets or islets of Langerhans (Thomas Colville, 2016). They play an important role in the production of insulin and maintaining normoglycaemia.

Pathophysiology

Digestive enzymes — trypsin

Trypsin is a digestive enzyme secreted by the pancreas. It is stored in zygomen granules inside the organ as trypsinogen, its inactive form. The zygomens are secreted into the duodenum where they are activated by other digestive enzymes. Early activation within the pancreas can cause autodigestion and severe inflammation of the pancreas. Protease inhibitors play an important role in removing trypsin from the circulation. If more than 10% of acinar trypsin becomes activated, trypsin inhibitors become overwhelmed and a chain reaction occurs: damage to digestive enzymes in the acinar cell and vascular endothelium occur, leading to circulatory changes, vasoconstriction, capillary stasis, pancreatic oedema and ischaemia (Walton, n.d.). Inflammatory cells may be released into the circulation causing organ failure, such as acute kidney injury or acute respiratory distress (Walton, n.d.). Autodigestion, severe inflammation and peri-pancreatic fat necrosis lead to focal and generalised sterile peritonitis.

Signalment

Dogs of any age, sex or breed can develop pancreatitis, however, it seems most common in middle aged to older dogs (Watson et al, 2010). Some breeds seem to be overrepresented:

• Miniature Schnauzers
• English Cocker Spaniels (Watson et al, 2007)
• Cavalier King Charles Spaniel (Watson et al, 2007)
• Boxers (Watson et al, 2007)
• Collies (Watson et al, 2007)
• Terriers.

Clinical signs

Clinical signs can vary depending on the severity of the disease. They are caused by local pancreatic inflammation and systemic inflammatory response syndrome (Bostrom et al, 2013):

• Lethargy (80% of dogs)
• Anorexia (91%) or hyporexia (70%)
• Vomiting in 63–90% of dogs — this usually occurs because of delayed gastric emptying from peritonitis
• Diarrhoea (33–36%)
• Weakness (79%)
• Dehydration (46%)
• Tachycardia
• Cranial abdominal pain (45–58%)
• Pyrexia
• Jaundice caused by elevated total bilirubin because of extra-hepatic biliary duct obstruction — typically an acute flare up in a dog with chronic pancreatitis
• Presence of a cranial abdominal mass
• Low volume ascites
• Cardiac arrhythmias — caused by the release of myocardial depressant factor in some animals. Pain could also be a contributing factor.
• Pancreatitis can mimic the clinical signs of many other acute abdominal diseases, such as a gastric foreign body, acute kidney injury, septic peritonitis etc
• End-stage chronic pancreatitis may present with signs of concurrent illness, such as diabetes mellitus, or exocrine pancreatic insufficiency, as a result of a permanent loss of endocrine and exocrine function respectively.

Pancreatitis can be a difficult disease to diagnose. Histopathology is thought to be gold standard but is invasive, and pancreatic biopsy can carry a variety of risks and complications (Floris Dröes, 2017). Clinical judgement alongside imaging and biochemical findings are used to support a diagnosis of pancreatitis (Hess, 1998).

Causes

Around 90% of cases are idiopathic, with no known cause (Watson, 2004). A common trigger of acute pancreatitis in dogs is the ingestion of a high fat diet. This could be a routine high fat diet or a one-off dietary indiscretion (Lem et al, 2008).

Some of the other causes associated with canine pancreatitis include:

• Trauma or previous surgery
• Hypercalcaemia
• Medication (such as potassium bromide)
• Stress
• Duodenal and biliary reflux as seen in inflammatory bowel disease.

Cases of pancreatitis can be mild or severe and acute or chronic.

Acute pancreatitis

Acute pancreatitis cases tend to be more severe than chronic cases, and may be fatal. There may be little or no permanent pathological changes after recovery.

Chronic pancreatitis

Chronic cases have a continuing inflammatory process that is characterised by irreversible changes to the pancreas.

Commonly dogs can have chronic pancreatitis then an acute episode may be triggered by a fatty diet or scavenging.

Nausea, vomiting and regurgitation

Altered gastrointestinal motility (ileus) can occur as a result of regional peritonitis, which can cause nausea. It is important to be able to recognise the signs of nausea so treatment can be administered if necessary.

Signs of nausea can include:

• Inappetence
• Salivation
• Lip smacking
• Gulping
• Ragging/retching.

Nausea can cause vomiting, but nausea may also be present without vomiting. It is important to be able to tell the difference between vomiting and regurgitation.

Vomiting is the involuntary, forceful discharge of ingested material. There are two phases — retching and expulsion. Vomiting can significantly increase morbidity by worsening the patient's hydration status, acid–base and electrolyte balance.

Regurgitation is the passive discharge of ingested material often associated with oesophagitis in pancreatitis patients after protracted periods of vomiting. Both vomiting and regurgitation can potentially cause aspiration pneumonia.

Antiemetics, such as maropitant and ondansetron, are very effective in reducing emesis and can be used alongside one another if necessary. Maropitant is the most used antiemetic in practice and is thought to have some analgesic properties (Mansfield and Beths, 2015).

Although the evidence is limited around the analgesic properties of maropitant, it may be used to form part of a multi-modal analgesic plan (Bradbrook, 2020).

Nutrition

Nutrition of the pancreatitis patient is an essential part of the recovery process and has caused much controversy over the years.

Traditionally, the approach to the pancreatitis patient consisted of ‘resting’ the pancreas for 24–48 hours to prevent the production of digestive enzymes (Simpson, 2003). Some studies have shown better weight gain and improvement of condition in dogs fed within 12 hours of admission despite vomiting than those that were starved until the vomiting had stopped. The theory is that this is a result of improved enterocyte nutrition and prevention of malnutrition in these patients. Enterocyte nutrition improves enterocyte health, immune function and gastrointestinal (GI) motility. Early enteral nutrition plays an important role in preventing bacterial translocation and endotoxin release (Wang et al, 2013).

Acute severe pancreatitis patients have usually been anorexic for over 48 hours before presentation, and will likely remain so for several days. In these patients it is vital to provide assisted enteral nutritional support shortly after admission to the hospital with the use of a feeding tube.

Choosing a feeding tube

There are many different types of feeding tubes available. NG and oesophagostomy tubes are the most commonly used in veterinary patients (Jensen and Chan, 2014):

• NG tubes are a great short-stay tube that can be placed conscious. They are generally well tolerated but can block easily because of the narrow bore of the tube (only liquid diets can be used). The benefit of a nasogastric over a naso-oesophageal (NO) tube is that it allows aspiration of the stomach contents prior to feeding if gastric ileus or gastric distension is a problem. This reduces the risk of regurgitation and aspiration pneumonia. It was previously thought that a NG tube was more likely to cause complications, such as regurgitation and gastro-oesophageal reflux, as it crossed the lower oesophageal sphincter. However, research has shown that neither tube carries a higher complication risk over the other (Yu et al, 2013).
• Oesophagostomy tubes are a great long-stay tube that are easy to place (although they do require a general anaesthetic) and can be used at home. They are less likely to become blocked than NG tubes because of the wide bore of the tube. A variety of diets can be fed through an oesophagostomy tube including most wet diets blended with water.

The author recommends the placement of a NG feeding tube early on during the patient's hospital stay for early enteral nutrition. Once the patient is cardiovascularly stable with a safe electrolyte balance, the patient should be anaesthetised for a diagnostic investigation and placement of an oesophagostomy tube.

Placement of a naso-gastric feeding tube

See Tables 1 and 2, Figures 1, 2 and 3.

Techniques to confirm placement

There are five options for confirming placement:

• A lateral thoracic radiograph (preferred by the author)
• Presence of negative pressure — if the tube is in the trachea there will be no negative pressure
• Slow injection of 5 ml sterile water — if coughing occurs, stop as the tube is likely to be sitting in the trachea
• Attach capnograph to check for carbon dioxide (CO₂) reading — CO₂ should be detected if the tube is in the airway (Johnson et al, 2002)
• A NG tube should sit in the stomach which will also allow you to aspirate stomach content if required.

Feeding and daily tube care

Feeding and daily care of the tube involves:

• Cleaning the tube twice a day with a swab and sterile saline
• Sterile water should be used to flush slowly before each feed to confirm the tube is still in the oesophagus — the patient will cough if it has been inhaled
• The tube should be flushed with sterile saline twice daily to maintain patency, especially once the patient starts to eat and the tube is used less frequently
• Check attachment site and clean the staples/stitch
• The patient should ideally be sitting up in sternal recumbency during administration of food to prevent regurgitation
• Calculate new daily resting energy requirement (RER)
• Liquid diets are ideal and should be administered slowly over 20 minutes
• Food should be warmed before administration to non-nauseous patients. If the patient is still nauseous, the smell of warmed food is likely to worsen this. In this instance, warm the food to room temperature only
• Lip smacking may be a sign of nausea, if noted slow down the rate of administration
• If the patient is eating a small amount, top up feeds should be provided to ensure the daily RER is met
• A buster collar should be worn to prevent interference. If the patient is tolerating the tube well, the busted collar may be removed while the food is being administered
• Remember that tender loving care (TLC) goes a long way for hospitalised patients, and meal time is an ideal time for this.

Complications of naso-gastric tubes

A number of complications can occur with NG tubes:

• Coughing sneezing or regurgitation — if tolerated, the tube can often be reinserted
• Chewed off — remove remainder of the tube and monitor for the tube being passed in faeces
• Inhalation — requires endoscopic retrieval
• Local irritation to the nostril — check the tube has not been pulled too tight when secured. If it is too tight, loosen and re-secure in place. A small amount of lubrication around the nostril may make the patient feel more comfortable. The nostril should remain clean and clear without blockage Buster collars should always be worn.

Contraindications to naso-gastric feeding tube placement

There are a number of contraindications to placing NG tubes. They should not be placed in:

• Recumbent patients/patients in a coma
• Primary gastric disease i.e. gastric outflow obstruction, oesophagitis, persistent vomiting
• Facial trauma or disease to the nose or maxilla, i.e. rhinitis
• Severe thrombocytopenia (bleeding disorder)
• Brain trauma
• Increased intracranial pressure.

Resting energy requirement (RER)

Calculating a patient's resting energy requirement while in the hospital environment is very important. It allows veterinary professionals to provide the correct number of calories required and prevent nutritional deficiencies.

There are a number of different calculations available based on the patient's weight. The following formula is commonly used for patients between 2 and 45 kg:

RER = 30 × BW ( kg ) + 70 ( Merrill, 2012 )

If a patient is less than 2 kg, the following formula may be used:

RER = 70 × BW ( kg ) 0.75

The patient's calorie requirement should be calculated and increased gradually over 3–5 days based on the length of time they have been anorexic. This helps reduce the risk of refeeding syndrome once food is reintroduced.

If the patient has been anorexic for up to 3 days, gradually build up to 100% RER over 3 days. If the patient has been anorexic for more than 3 days, gradually build up to 100% RER over 5 days.

It is vital to weigh patients daily and adjust the RER accordingly. RER is a guide only, and the individual diet plan should be assessed and adjusted as necessary. For example, if a patient is losing weight or seems hungry, the amount of food offered may be increased to prevent malnutrition. Whenever alterations are made to a patient's feeding plan, it is important to monitor for signs of nausea. It is vital that the increased volume is well tolerated by the patient.

Feeding

A variety of different methods may be used to tempt patients to eat, such as warming the food, stroking, talking to the patient and hand feeding. Detailed information should be kept in the patient's hospital records to include the food type offered, volume offered, volume eaten, technique used, and if the patient needed tempting.

It is recommended to feed little and often with a low-fat highly digestible diet (Ackerman 2019). There are many veterinary diets available for gastrointestinal disease containing a low-fat content. Diets formulated for obesity or fibre-responsive conditions are not appropriate as they require large volumes of food to meet the patient's energy requirements.

Low-fat liquid diets, such as Royal Canin Gastro-intestinal Low Fat Liquid, are ideal for administering via the NG tube. If a low fat liquid diet is unavailable, a diet that is not low-fat may be used, but the patient must be monitored closely for signs of nausea, vomiting and abdominal pain.

Trickle feeding via a constant rate infusion can be successfully used in hospitalised patients that will not tolerate bolus feeding. Syringe or force-feeding patients by mouth is not recommended. Aspiration pneumonia can occur, along with food aversion.

Pain assessments should be performed regularly to ensure the patient is comfortable and receiving an adequate level of analgesia. The Glasgow composite pain scale is a useful tool to use in practice. Good pain management and regular assessments are essential during the patient's hospitalisation and in supporting a successful recovery.

Home care

Once discharged from the hospital, the patient's feeding regimen is often altered to a long-term therapeutic diet in patients with pancreatitis. If hyperlipidaemia is present, the diet should remain low fat. Otherwise, a moderate fat level of no more than 40 g/1000kcal or 15% fat on a dry matter basis (Wood, 2019). High fat diets, table scraps and fatty snacks should be avoided long term.

Owner education is essential in these cases as many patients can continue with chronic pancreatitis for the rest of their lives. Nutritional guidance and education of clinical signs will help the owner in preventing any future flare ups or help spot them early should one occur.

Conclusion

Feeding tubes are a really useful addition to a nursing care plan. Nutrition is the cornerstone of treatment for many conditions, and feeding tubes are an excellent way of achieving this level of care. Nurses are qualified individuals with a large set of practical skills, and NO or NG tube placement can be part of all nurses' skill set. Being more active with nutrition in the hospital setting will help veterinary professionals achieve a successful outcome for patients. More research is needed around specific diets for canine pancreatitis cases — there is varying evidence on what level of fat content is deemed appropriate in diets used to treat canine pancreatitis. It remains a challenging disease to diagnose, treat and manage, but with good nursing care and owner compliance, the outcome can often be successful.

KEY POINTS

• Early onset nutrition has been shown to reduce hospitalisation times and improve patient outcome.
• Feeding tubes are a useful and effective method of achieving the patient's resting energy requirement (RER) when anorexic or hyporexic.
• Nutrition is the cornerstone treatment for many medicine conditions. Feeding tubes allow us to achieve that goal and may contribute to a successful patient outcome.
• There are several breed predispositions to canine pancreatitis, however, any dog can get the disease.
• Good owner education is imperative to potentially prevent future flare ups and maintain a good level of compliance. Long-term dietary changes may be necessary in most patients.