Nutrition is an oft-overlooked aspect of management of the hospitalized patient. In the case of inadequate energy intake in the non-stressed cat or dog, the body will down-regulate energy expenditure, conserve lean muscle mass and increase lipolysis. However, in the stressed patient with inadequate energy intake, increased levels of catecholamines, glucocorticoids, and inflammatory cytokines lead to peripheral insulin resistance and proteolysis in addition to lipolysis. Lack of nutritional support contributes to depressed immune function, increased length of hospitalization, increased morbidity, and increased mortality. Therefore, nutritional support should be included in the treatment plan of every patient who cannot or will not eat.
In general, enteral feeding is the preferred method of nutritional support. The closer one is to the oral route of food intake, the more efficient assimilation and digestion of nutrients will be and the greater flexibility one has in formula composition. The presence of luminal nutrients maintains mucosal integrity and decreases bacterial translocation. Atrophy of enterocytes begins within 48 hours of onset of anorexia. Parenteral nutrition should be reserved for those patients whose gastrointestinal tract is not functional or when total bowel rest is indicated.
Force-feeding a critical patient is not recommended. It is very stressful for the patient. It is difficult to force feed the required amount of calories. And, particularly in cats, it can cause food aversion to develop. A variety of feeding tubes can be employed to aid in enteral nutrition; nasoesophageal (NE), esophagostomy (E), and gastrostomy (G) tubes are the most commonly used. Of these tubes, the NE and E tubes are relatively easy to place, inexpensive and do not require specialized equipment or invasive procedures to place.
NE tubes carry the benefits of being inexpensive and easy to place with no general anesthesia required. They tend to be well tolerated by the majority of patients and carry a very low risk of complications. They are only appropriate for short-term feeding, however, as usage beyond 3-5 days will lead to pressure necrosis of the nasal mucosa. Also, diet choices are limited to liquid diets, and even then these tubes are prone to blockage. Patients with NE tubes in place must wear an Elizabethan collar to prevent them from dislodging the tube. Potential complications of NE tubes include epistaxis during placement, development of sinusitis, or dislodgement of the tube if the patient vomits or sneezes excessively. NE tubes should not be used in patients with head or neck injury; patients requiring surgery of the nasal cavity, pharynx or esophagus; patients with esophageal motility disorders or strictures; patients with a coagulopathy; patients without a normal gag reflex or unable to protect their airway; and patients with vomiting.
Supplies to gather prior to NE tube placement include: 0.5% proparacaine, water-based lubricant, the feeding tube, 1” white tape, a packet of 2-0 or 3-0 suture, needle drivers or a 20 g needle, suture scissors, skin stapler or tissue glue, and an Elizabethan collar. Depending on the patient’s temperament, sedation may be necessary in addition to topical anesthesia. For cats a 3.5-5 French feeding tube can be used, for dogs a 5-8 French feeding tube. A long red rubber catheter can work as a feeding tube. There are also tubes specially made for NE use, such as a Kendall Argyle feeding tubes. Some of the specially made feeding tubes are radio-opaque, to better assess placement on radiographs.
Placement of an NE tube takes just a few minutes. The patient is sedated, if needed. A few drops of proparacaine are instilled into the nostril the NE tube will be placed a few minutes before starting. The tube should be pre-measured from the tip of the nose to the 7th or 8th intercostal space. The tube can be marked with a butterfly of 1” tape. The tip of the tube is lubricated. Restrain the patient and immobilize the head while the veterinarian directs the tube into the nostril, in a medial-ventral trajectory. Passage of the tube will be slowed as the oropharynx is approached, to allow the patient to swallow the tube into the esophagus. The tube is inserted up to the level of the white tape butterfly. The tape butterfly is then sutured to the nasal planum, just lateral to the external naris. The alar fold should then be glued down over the tube. The tube can further be secured with staples or tissue glue at the dorsal bridge of the nose and on one or two spots on the dorsal midline of the head. Finally, an Elizabethan collar is placed to prevent dislodging the tube by either pawing at or rubbing the nose.
After NE tube placement, the location of the tube should be confirmed. Injecting sterile water or saline into the tube or connecting the tube to a capnograph will confirm that the tube is within the gastrointestinal tract instead of the trachea. However, a lateral thoracic radiograph is preferable as it will not only confirm placement in the gastrointestinal tract, but it will also confirm location of the distal tip of the NE tube. Ideally the tip of the tube should at the 7th or 8th intercostal space. If the distal tip of the tube is in the stomach, it may promote acid reflux and esophagitis as the presence of the tube irritates the lower esophageal sphincter. (Occasionally this disadvantage to a nasogastric tube is outweighed by the ability to use a NG tube to suction gastric contents in patients with gastric stasis. This is particularly notable in puppies with parvovirus enteritis. There are tubes specially designed for nasogastric placement that have a weighted tip.)
Patients can be fed via NE tube immediately after placement, unless the patient had been sedated. Either boluses of liquid food can be given 4-6 times daily or as a constant rate infusion. Constant rate infusions are most commonly used with NE tubes. Some patients may require occasional nasal proparacaine drops for comfort.
E tubes carry the benefits of being generally the best tolerated tube by patients and large enough that a blenderized diet can be fed through it. While their placement does require general anesthesia, placement is relatively fast and carries a low risk of complications if properly performed. E tubes can be left in place for weeks to months at a time. Unlike NE tubes, E tubes can be used at home by owners. And, unlike G tubes, there are no adverse effects if an E tube is removed prematurely. However, E tubes do require bandaging and wound care and can be removed by a patient if not well secured. They can also be vomited up and bitten off. Potential complications of E tubes include inadvertent laceration of the jugular vein during placement, inadvertent placement in the mediastinum during placement, and cellulitis surrounding the stoma. E tubes should not be used in patients intolerant of general anesthesia; patients that have had surgery of the esophagus; patients with esophageal motility disorders or strictures; patients with a coagulopathy; and patients with vomiting.
Supplies to gather prior to E tube placement include: sterile gloves for the veterinarian, the feeding tube, a Christmas tree adaptor and PRN if using a red rubber feeding tube, a permanent marker, a packet of 2-0 or 3-0 suture, needle drivers and a thumb forceps, curved Kelly or Carmalt hemostats, #10 scalpel blade, suture scissors, non-adherent dressing and antibiotic ointment, and bandaging material. For cats an 8-14 French feeding tube can be used, for dogs an 8-24 French feeding tube. A long red rubber catheter can work as a feeding tube. There are also tubes specially made for E tube use, such as a Cook’s or Mila esophagostomy tube. Tubes made of silicon are longer lasting than red rubber catheters. Some of the specially made feeding tubes are radio-opaque, to better assess placement on radiographs.
Placement of an E tube requires general anesthesia. The patient should be intubated and placed in right lateral recumbency. The left side of the neck should be shaved from the ramus of the mandible cranially to the thoracic inlet caudally and from the cervical epaxial muscles dorsally to the ventral midline and then sterilely prepped. The veterinarian will pre-measure the feeding tube from the mid-cervical region to the 7th or 8th intercostal space and ask for their assistant to mark the tube. The veterinarian will then insert a curved hemostat into the mouth and down the esophagus. They will then use the scalpel blade to make a stab incision through the skin of the mid cervical region and push the tips of the hemostat through the skin incision. They will then grasp the distal end of the tube with the hemostat and pull the tube rostrally through the mouth. The tube is folded back on itself and pushed caudally back down the esophagus, taking care to avoid wrapping it around the endotracheal tube. The proximal part of the tube will “flip” rostrally once the tube is straight within the lumen of the esophagus. The veterinarian will then suture the tube in place. If using a red rubber tube, it should then be capped off with the Christmas tree adaptor and PRN. Cut a slit in a piece of non-adherent dressing and apply antibiotic ointment to the dressing. Apply the dressing over the stoma and secure with a light three layer wrap. After E tube placement, the location of the tube should be confirmed as with NE tubes.
Patients can be fed via E tube after recovery from anesthesia. Either boluses of food can be given 4-6 times daily or a constant rate infusion of a liquid diet. Bolus feedings are used most commonly with E tubes. The bandage should be changed daily and the stoma lightly cleansed. A Kitty or Kanine Kollar (http://kittykollar.com/) can also be used in the place of bandaging.
G tubes are the largest bore feeding tubes allowing the thickest foods to be fed through them. They can also be permanent. G tubes can be used at home by owners. G tubes also can be used in patients with esophageal disease. However, G tubes either require specialized equipment (i.e. an endoscope) to place non-invasively or require a laparotomy. If a G-tube is removed prematurely before the stomach adheres to the body wall, which takes approximately 10-14 days, life-threatening peritonitis can occur. Potential complications of G tubes include inadvertent laceration of the spleen, intestines or diaphragm during endoscopic placement; cellulitis of the stoma; and peritonitis. G tubes should not be used in patients intolerant of general anesthesia; patients with a coagulopathy; patients with a disease that will delay stoma formation after placement (e.g. ascites, high-dose steroid therapy); or placed endoscopically in deep chested dogs.
Supplies to gather prior to G tube placement include: the feeding tube, a Christmas tree adaptor and PRN depending on the type of tube, a packet of 2-0 or 3-0 suture, and stockinette. Additional supplies will be needed depending on if the placement will be via endoscope or laparotomy. For cats a 16-20 French feeding tube can be used, for dogs a 16-28 French feeding tube. A mushroom-tipped Pezzer catheter can work as a feeding tube. A Foley catheter is not suitable for use as a G tube as the balloon is not durable enough. There are also tubes specially made for G use, such as the Mila gastrostomy tube. There are also low profile G tubes for patients who will need the G tube for the long-term, but these tubes are not suitable for initial placement.
Placement of a G tube requires general anesthesia. The patient should be intubated and placed in right lateral recumbency. The left side of the abdomen should be shaved from behind the last rib cranially to the wing of the ileum caudally and from the epaxial muscles dorsally to the ventral midline and then sterilely prepped. After the veterinarian places the G-tube, a non-adherent dressing can be applied over the stoma and the tube secured with stockinette fashioned into a shirt.
Patients should not be fed via the G tube until 24 hours after placement. Either boluses of food can be given 4-6 times daily or a constant rate infusion of a liquid diet. Bolus feedings are used most commonly with G tubes. The dressing should be changed daily and the stoma lightly cleansed. An infant or toddler t-shirt can be used in place of the stockinette if the patient will tolerate it.
Tube use & troubleshooting
When preparing food for an E or G tube, blenderize the food with a small amount of water thoroughly for 3-5 minutes to ensure it is as smooth as possible. Keep unused quantities in the refrigerator until needed. Warm to body temperature before use. Food that is cold from storage may induce vomiting. Mix thoroughly to ensure there are no hot spots in the food. It may help to re-blend the slurry before each use.
Always offer the patient food to eat before feeding through the tube. As the patient begins to eat on their own, tube feedings can be reduced in amount and frequency. Before feeding, aspirate the tube. You should receive negative pressure. If, on aspirating a G tube prior to a meal, you remove more than half the volume fed at the previous meal, hold off on feeding and try again later. Notify the veterinarian as prokinetic therapy may need to be started.
When bolus feeding, the food should be administered slowly, beginning at a rate of approximately 1 ml a minute. Monitor the patient for signs of nausea (e.g. excessive swallowing, hypersalivation, vomiting) or discomfort (e.g. restlessness or vocalizing). If any signs are noted, temporarily discontinue the feeding. You may be able to restart the feeding more slowly once the symptoms subside. If the patient is tolerating the meal, the rate of administration can be slowly increased. An entire meal can typically be given over 10-20 minutes.
After meals, the tube should be flushed and filled with a column of water to help prevent clogging. If the tube does become clogged, first try flushing the tube with warm water. Allow the water to sit in the tube for 5-10 minutes and flush again. If that does not work, flush with ¼ tsp of pancreatic enzymes (e.g. Viokase) + 325 mg sodium bicarbonate mixed with 5 ml warm water. Again, allow the solution to dwell in the tube for 5-10 minutes before flushing again.