Enteral feeding in dogs and cats: Indications, principles and techniques (Proceedings)
Enteral feeding tubes are an essential tool in the provision of nutritional support to animals unable or unwilling to consume sufficient calories on their own. Nutritional support should be considered for any animal that has been anorexic or has had inadequate voluntary caloric intake for ? 3 days, has lost ? 10% of their body weight or has other signs of malnutrition (e.g. poor hair coat, muscle wasting, poor wound healing, hypoalbuminemia, lymphopenia).
Introduction and General Principles
Enteral feeding tubes are an essential tool in the provision of nutritional support to animals unable or unwilling to consume sufficient calories on their own1. Nutritional support should be considered for any animal that has been anorexic or has had inadequate voluntary caloric intake for ≥ 3 days, has lost ≥ 10% of their body weight or has other signs of malnutrition (e.g. poor hair coat, muscle wasting, poor wound healing, hypoalbuminemia, lymphopenia)2. Nutritional support should be considered in patient with predisposing conditions such as vomiting, diarrhea or liver disease, prior to development of overt malnutrition3. Pre-emptive feeding tube placement is also recommended in patients where complete or partial anorexia can be expected (e.g. facial or jaw surgery, feline gastrointestinal lymphoma, etc.) and can often be done at the time of general anesthesia for initial therapeutic or diagnostic procedures.
When the gastrointestinal tract is functional, enteral nutrition is usually preferable to parenteral nutrition, as it is a simpler, more economical, has fewer complications and is more physiologically sound2,3. As a starting point, animals are generally supplemented with calories equivalent to their resting energy requirement (RER) each day (RER = (70 x body weight in kg)0.75 )2. Body weight, body condition and tolerance to enteral feeding are carefully monitored to determine if the caloric value of the nutritional plan should be modified2. The volume of commercially available liquid (nasoesophageal and jejunostomy tubes) or blenderized canned diet (esophagostomy and gastrotomy tubes) to be fed each day is calculated. Canned diets (Hill's a/d, Eukanuba Maximum Calorie, Royal Canine Recovery RS) are blenderized with just enough water to ease passage through the tube. The energy density (kcal/mL) of the blended food is equal to the kcal of the unaltered diet divided by the final volume (in mL). The volume (mL/day) of food to be administered per day is equal to the RER (kcal/day) divided by the energy density of the blended food (kcal/mL). Liquid diets (e.g. Clinicare Canine/Feline or RF liquid diet (Abbott Animal Health)) generally need not be diluted, so the volume equivalent to the animals RER is administered each day. Assuming enteral feeding is well tolerated, animals that have been anorexic for more than 3-5 days, should be fed one third of their RER on Day 1, 2/3 of their RER on Day 2 and full RER from Day 3 onwards.
Feeding can occur as a continuous infusion (generally liquid diets to hospitalized patients) or as 4-6 bolus feedings per day. Bolus feedings should be warned to body temperature by resting the filled syringe in a warm water bath. For bolus feeding through esophagostomy and gastrotomy tubes, the tube is aspirated with a syringe prior to instillation of food. If residual food is aspirated it is returned to the patient and the volume of the scheduled feeding decreased by an equivalent amount. If residual food volumes are persistent or prevent feeding full RER, promotility agents should be considered (e.g. metoclopramide 0.3 mg/kg PO or via tube 3-4 times per day 30 minutes prior to feeding). A volume of 5-10mL/kg/feeding is usually well tolerated, although animals that were eating normally before tube placement (e.g. post-op facial surgery) or animals that have been chronically tube fed may tolerate slightly larger volumes2. The tube should be flushed with 5-10mL of water after each feeding.
Complications common to enteral feeding techniques in general include tube dislodgement, tube obstruction, aspiration pneumonia and diarrhea4. To prevent obstruction, the tube should be flushed with lukewarm water before and after bolus feedings or medications, intermittently throughout the day for continuous feeding and whenever the tube is aspirated to check for gastric contents or of gastric contents are noted within the tube. Injecting water under gentle pressure will relieve most obstructions4. If unsuccessful, instill carbonated water4 or Coca Cola6 and leave for 1-2 hours (or longer) to digest6. Avoid putting sucralfate through the tube and dissolve all tablet medications completely in water prior to administration through the tube4. Inflammation of the ostomy site, especially in the first few days following placement, is a common complication of esophagostomy, gastrotomy and jejunostomy tubes. Infection of the stoma site is treated with flushing and cleaning of the wound, topical antibacterial ointment and frequent dressing changes4. Persistent leakage or infection of the stoma site requires further investigation. Diarrhea may occur as a result of the primary disease process, the high fat content or osmolality of the diet aconcomitant antibiotic therapy4.
1. Nasoesophageal (NE) tube
Indications: Short term (< 7-10 days), in-hospital nutritional support of patients with normal nasal cavity, pharynx, esophagus and stomach.4
Technique: Instill 3-5 drops of proparacaine hydrochloride into the nostril4,5. Determine the length of the tube (8-French (dogs > 15 kg or 33 lbs) or 5 -French (cats and small dogs) polyvinylchloride, polyurethane or red rubber tube) to be inserted by measuring from the tip of the nose to the 7th or 8th intercostal space and mark with pen or tape. Lubricate tube with 5% viscous lidocaine4. Hold the animal's nose with your non-dominant hand, maintaining the head in a neutral position. From the ventromedial aspect of the nostril, gently (but quickly) direct the tube caudoventrally and medially, into the ventral meatus. Advance the tube in a ventromedial direction to the pre-marked length, flexing the neck down to minimize the chance of tracheal intubation5. The tube should pass easily, with no resistance. If resistance is felt, the tube may be in the middle meatus. Secure the tube to the animal at the junction of the lateral aspect of the planum nasale and the hair and on the dorsal midline between the eyes with a SMALL amount of glue 4,6 or by suturing in place5. The patient should wear an E-collar to deter tube removal. Verify correct tube placement by aspirating with a syringe to check for negative pressure; significant air in the syringe suggests tracheal intubation6. Instill 1-3mL of sterile saline into the tube2,6. If the patient coughs, tracheal intubation is likely. Obtain a lateral thoracic radiograph to confirm the distal end of the tube lies just beyond the heart in the mid-distal esophagus5. Placement near or across the lower esophageal sphincter increases the likelihood of gastroesophageal reflux4. Re-confirm tube placement if the animal vomits, coughs or seems uncomfortable during feeding5.
Complications: Epistaxis, dacrocystitis, rhinitis, sneezing, inadvertent tracheal intubation, vomiting, tube dislodgement, clogging of tube, small bowel diarrhea secondary to liquid diet4,5.
Comments: General anesthesia is NOT required for placement, although mild sedation may be required. As such NE tubes are good choice for stabilization of debilitated patients or as a stop-gap measure (e.g. over the weekend) until a more permanent tube can be placed. NE tubes are contraindicated in vomiting patients or patients without a gag reflex because of the risk of aspiration pneumonia3. The small diameter of the tube means feeding is limited to a liquid diet in either a bolus or continuous feeding schedule. As such, NE tubes are only appropriate for hospitalized patients. Feeding may be initiated immediately after placement
2. Esophagostomy tube
Indications: Long-term (> 1 week to 3-4 months)7, at home nutritional support of patients with normal pharynx, esophagus and stomach.
Technique: The patient must be under general anesthesia with endotracheal intubation and in right lateral recumbency. Clip and aseptically prep the left cervical region from the angle of the mandible to the mid-cervical region and the wing of the atlas to the trachea6. Choose a 12 (small cats) 14 (cats and small dogs) or 16 to 20-French (dogs > 15 kg or 33lbs) red rubber (most commonly), polyurethane or silicone tube4,5 tube. Determine the length of the tube to be inserted by measuring the tube from the 7th intercostal space (tip of the tube) to the point where the tube will exit the skin; just distal to the hyoid apparatus and dorsal to the jugular groove 5,6. Advance curved forceps (e.g. curved carmalt) through the mouth into the proximal esophagus and direct the curved tip laterally4,6. Palpate the tip of the forceps externally in the mid-cervical region, over the proposed site of insertion4. Use a No.11 scalpel blade to make a small (5 mm) skin incision over the tip of the curved forceps 4,6. Push the forceps laterally to expose the esophagus over the tips of the forceps through the skin incision4,6. Use the scalpel blade to make a very small nick in the esophagus over the tip of the forceps and gently force the tip of the forceps through the nick6 or bluntly push the tip of the forceps through the esophagus and skin incision5. Grasp the distal end of the tube with the forceps and pull it into the esophagus and out the oral cavity such that the distal end of the tube extends out the oral cavity and the proximal end out the cervical incision4-6. Being careful not to pull the proximal end of the tube through the skin incision, redirect the distal end of the tube posteriorly (down the esophagus) with fingers or forceps5,6. The proximal end of the tube will rotate in a cranial direction as the distal portion of the tube moves down the esophagus4. Advance the tube to the premeasured length and secure in place with a purse-string (around the incision and tube) and "Chinese finger trap" suture (2-0 polypropylene) and a tacking suture through the periosteum of the wing of the atlas4,6. Place a small amount of antibiotic ointment over the tube exit site and cover with gauze. Apply a light, circumferential wrap and cap the tube (catheter injection cap or other adaptor) to prevent aerophagia6. Obtain a lateral thoracic radiograph to ensure the distal end of the tube lies in the distal third of the esophagus 5 and does not encroach on or cross the lower esophageal sphincter.
Complications: The most common complication is inflammation or infection of the stoma site 6. Ostomy site should be inspected every 1-2 days and owners instructed on proper stoma care and bandaging 7. Minor redness and discharge around the stoma site is normal, especially for the first 1-2 weeks days after placement. Premature or inadvertent tube dislodgement is also common. Vomiting may displace the distal end of the tube into the oral cavity 6,7. If the patient vomits, a lateral thoracic radiograph is recommended to confirm tube placement prior to resumption of tube feeding. Animals have been known to bite off and swallow the end of a dislodged tube. Alternatively, patients may dislodge tube through biting, rubbing or scratching at stoma site or circumferential wrap 5. If clinical signs of esophagitis or vomiting are observed, a lateral thoracic radiograph is indicated to evaluate for potential distal migration of the tube across the lower esophageal sphincter7. Repositioning of the tube may be required.
Comments: The larger diameter of the tube compared to NE tube, supports blended diets and administration of oral medications. Feeding may be initiated immediately after placement. Esophagostomy tubes are contraindicated in vomiting animals (see Complications)6. Some authors have suggested esophagostomy tube placement may be more difficult in larger dogs5. Alternate techniques include percutaneous feeding tube applicator technique and percutaneous needle catheter technique4. Most owners report a high degree of satisfaction with the tube and are comfortable with their use7. If the tube becomes dislodged or non-functional, it can be replaced through the existing stoma (assuming no cellulitis or infection). General anesthesia is recommended and the reader is encouraged to review the technique5. A normograde minimally invasive technique for esophagostomy tube placement in the cat was recently described8. A major limitation of this technique is the small diameter of the tube, limiting feeding to liquid diets but may be effective for short term, in hospital feeding of feline patients with facial or oral trauma where NE tube placement is contraindicated8.
3. Percutaneous endoscopically-guided gastrotomy (PEG) tube
Indications: Long-term (months), at home nutritional support of patients with conditions where food or fluid in the stomach or duodenum is not contraindicated6. It is the long-term feeding tube of choice in patients with oropharyngeal or esophageal disease or patients in which esophagostomy tube is contraindicated or not tolerated. Alternative techniques for placement of gastrotomy tube include surgical placement during laparotomy or by left-flank approach 9 and blind percutaneous gastrotomy technique4.
Technique (see references 5 and 6 for additional details): With the patient under general anesthesia with endotracheal intubation and in right lateral recumbency, clip and aseptically prep an 8cm x 8 cm area centered over the distal end of the last rib5,6. Choose a 14 (small cats), 16 (cats and small dogs), 18 (10-25 kg), 20 (25-40kg) or 22-French (> 40kg) Bard-Pezzer mushroom tip catheter. Cut a piece of tube off the distal end of the mushroom tip catheter that is slightly longer than the width of the mushroom tip6. Make a 0.5cm slit in the middle of the cut piece of tubing. Pass the distal end of the feeding tube through the slit and slide the cut piece down the feeding tube to rest next to the mushroom tip6. This creates an "internal phalange". Cut a minimium1 meter piece of 2-0 nylon or mersilene suture. Pass the endoscope into the stomach and insuflate with air to visualize the entire gastric mucosa, ensuring there are no findings that would prohibit tube placement. Insufalte the stomach until it is tense and firmly against the abdominal wall6. This displaces abdominal viscera from the insertion site and prevents the stomach from pushing away the catheter is inserted 5,6. Identify a proposed skin insertion site approximately 5mm ventral and 10 mm caudal to the last rib6. An assistant applies intermittent pressure with a sterile, gloved finger to the proposed skin insertion site5. The corresponding area of gastric indentation is visualized by the endoscopist to ensure it is an avascular area of fundus5. Using a No. 11 scalpel blade, the assistant makes a small (2mm) stab skin incision at the proposed skin insertion site5,6. The assistant quickly and sharply insert a 14-16 gauge over the needle catheter through the skin incision, entering the gastric lumen. The stylet is removed from the catheter and the nylon or mersilene suture passed through the lumen of the catheter and into the stomach6. The endoscopist grasps the suture within the stomach with biopsy or grasping forceps and pulls the endoscope and forceps as a unit into the esophagus and out the mouth6. Remove the catheter from the body wall over the suture material and place a small hemostat on the suture to avoid inadvertently pulling it into the stomach6. Insert a 3.5 French open-ended tomcat catheter over the oral end of the suture with the tip of the catheter directed in the distal or aborad direction5. Suture the oral end of the suture to the tapered end of the feeding tube using a horizontal mattress suture5,6. Wedge the tapered end of the feeding tube into the hub of the tomcat catheter (may need to trim the end of the feeding tube on an angle5. Move the feeding tube into the stomach by applying steady traction on the suture exiting the abdominal wall6. Do not pull on the tomcat catheter as it appears through the skin. Continue to pull the feeding tube until the mushroom tip can be palpated against the abdominal wall5,6. Endoscopically visualize the mushroom tip, ensuring it is snug against the gastric mucosa5,6. Create an outer flange by cutting off the distal tip of the feeding tube, make a 0.5 cm slit in the middle this piece of tubing and pass it over the exteriorized end of the feeding tube and slide it down to sit loosely against the abdominal wall6. Place a small amount of antibiotic ointment over the tube exit site and cover with gauze. A T-shirt or stockinette body shirt is placed over the tube to keep from catching on objects and protect from scratching / chewing6.
Complications: Inflammation or infection of the stoma site is a common complication, especially in the first few days to weeks after palcement6. Owners should be instructed to monitor the stoma site daily and report any changes or concerns. PEG-tubes should remain in place for at least 14 days after placement to ensure a strong adhesion between the tube and the abdominal wall. Peritonitis due to leakage of stomach contents or food into the abdominal cavity can occur following accidental dislodgement, tube migration or breakdown of the adhesion between the stomach and body wall. Owners should immediately discontinue feedings and seek veterinary care if the animal appears uncomfortable during feeding. The risk of tube dislodgement resulting in peritonitis is greatest in the first 14 days after placement but can occur at any time. Anecdotally, detachment of the stomach from the body wall may be more likely in large breed dogs. The author prefers surgically placed (exploratory laparotomy or flank approach) gastrotomy tubes or esophagostomy tubes in large breed dogs. Excessive tension on the mushroom tip (or inner phalange) or external phalange, can result in gastric or skin pressure necrosis, respectively4. Complications related to placement include splenic laceration, gastric bleeding or pneumoperitoneum and are best avoided by ensuring full insuflation of the stomach.
Comments: Commercial PEG-tube kits that include introduction needle, guidewire, 36-inch PEG-tube with collapsible internal bumper, external right angle fixation device and adapter for feeding are available (MILA International Inc., Erlanger, KY). The large diameter of the tube supports blended diets and administration of oral medications. PEG and gastrotomy tubes are contraindicated in vomiting patients. Non-surgically placed tubes should be used with caution in cachetic patients (poor healing) or in conditions where apposition of the stomach to the body wall is difficult (ascites, space occupying mass, splenomegaly, etc)4. Feeding is generally initiated immediately (surgically placed) or 24 hours after (endoscopically placed) placement. Trickle feeding of a liquid diet is recommended prior to initiation of bolus feedings.
4. Jejunostomy Tubes
Jejunostomy tubes are are indicated for short term (< 14 days) in hospital nutritional support of patients with conditions where food in the stomach is contraindicated (e.g. pancreatitis, gastropareisis, gastric outlet obstruction)3. Jejunostomy tubes are generally placed surgically, often during an exploratory laparotomy, although endoscopic placement through a PEG-tube was recently described 10. Jejunostomy tubes are of small diameter, necessitating feeding of a liquid diet. Complications include inflammation or infection of the ostomy site, tube migration, vomiting, diarrhea, abdominal pain, tube obstruction, accidental tube dislodgement with subsequent peritonitis 3,10.
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