Instead of viewing anorexia as a secondary problem that will improve when the primary disease has resolved, it is better to be proactive and administer nutrients early.
Instead of viewing anorexia as a secondary problem that will improve when the primary disease has resolved, it is better to be proactive and administer nutrients early. The major consequences of malnutrition are decreased immunocompetence, decreased anabolism, and altered intermediary drug metabolism. In chronic illness, loss of muscle mass is commonly observed before serum protein levels become subnormal because muscle wasting is less life threatening than decreased serum protein concentrations. Survival rates of human patients have been directly correlated with available muscle mass. Loss of more than 25 to 30% of body protein compromises the immune system and muscle strength, and death results from infection, pulmonary failure or both. As in human medicine, malnutrition in veterinary patients is thought to increase morbidity and mortality.
Any sick dog or cat with voluntary food intake significantly below the calculated daily resting energy requirement (RER) for more than three days is a good candidate for assisted feeding. Fasting for longer than three days results in enterocyte deterioration and decreased gastrointestinal immunity. Translocation of enteric bacteria may occur across a compromised intestinal mucosal barrier. Enteral infusion of even small quantities of a liquid diet (microenteral nutrition) has proven beneficial in preventing intestinal mucosal deterioration during parenteral nutrition in piglets and in human infants and adults
Selection of Feeding Route
Nutrients can be supplied either enterally or parenterally. Enteral feeding is preferred to parenteral feeding, whenever possible, because using the gastrointestinal tract is less expensive, stimulates the immune system and avoids most metabolic complications. Nutrients must be administered parenterally when the small intestine is not functioning sufficiently well to meet the patient's nutrient requirements enterally. When enteral access cannot be safely acquired for several days, parenteral nutrition can be used initially. An indwelling feeding tube is the method of choice if enteral feeding is necessary for more than two days. Nasoesophageal, esophagostomy, gastrostomy or enterostomy are potential tube placement sites. Pharyngostomy tubes are no longer recommended due to the risk of aspiration pneumonia. Because of frequency of insertion and ease of use, this talk will focus on placing and using nasoesophageal tubes.
Nasoesophageal (NE) tubes are generally placed to feed cats or dogs that are anticipated to need feeding for less than a week, such as for patients with facial trauma that may be unable to eat initially, or to precede placement of a more durable tube. Nasoesophageal tubes are occasionally used to feed a patient for several weeks, such as some cats with liver disease. General anesthesia or tranquilization is not necessary to place an NE tube, therefore these tubes provide enteral access to patients considered anesthetic risks.
Indwelling NE tubes are placed so that the tip lies in the distal third of the esophagus, not in the stomach (hence, the term "stomach tube" is not used). The reason for this is that gastric acid will reflux back into the distal esophagus if a tube is holding open the lower esophageal sphincter, causing esophagitis. A distal esophageal placement is accomplished by measuring the tube along the approximate course of the esophagus from the nose to the 10th rib before placing the tube. Polyurethane tubes (with or without a tungsten-weighted tip) and silicone feeding tubes may used. An 8-Fr. tube will pass through the nasal cavity of most dogs; a 5-Fr. tube is more comfortable for most cats.
Contraindications to using an NE tube include neurologically impaired patients (recumbent and/or lack of gag reflex), patients with primary gastric disease, gastric outflow obstruction, or gastric paresis (i.e. conditions causing profuse vomiting), and animals with severe facial, maxillary, or nasal trauma or disease. Severe debilitation/lateral recumbency may provide a relative contraindication.
5 French 36" or 8 French 42" feeding tube with a 0.025" or 0.035" angiography guide wire stylet
Topical anesthetic such as ophthalmic anesthetic drops
KY jelly or anesthetic lubricant
Mineral oil (lubricant for stylet)
Suture (3/0) and 20 gauge needle
Sterile saline, 12 cc syringe, and stethoscope for testing placement
1. Desensitize the nostril(s) with topical anesthetic (tilt head upwards)
2. Measure and mark the desired length of the feeding tube
- 10th rib or ziphoid for distal esophageal placement; last rib for gastric placement
3. Place a drop of mineral oil in the tube and advance the stylet
4. Lubricate the tip of the tube
5. Gently and deftly advance the tube into the ventral meatus of one nostril
- use "pig nose" technique in dogs to avoid having to aim the tube in a caudoventral and medial direction
- hold head at a normal angle of articulation to allow swallowing
6. Advance tube to the pre-determined mark and withdraw the stylet
7. Check tube placement
- aspirate air (will eventually get negative pressure in esophagus or stomach)
- rapidly inject 10 cc air while ausculting over distal esophagus or stomach
- inject 5-10 cc sterile saline and monitor for coughing
- lateral thoracic radiograph
8. Suture tube in place using Chinese finger knot, tape butterfly; staples or tissue glue; use 20 gauge needle to place sutures
- one suture through the wing of the nostril on the haired skin (avoid whisker entrapment)
- one suture over zygomatic arch
9. Coil extra tubing and tie with gauze around neck; fit Elizabethan collar
Whenever a patient is being fed by tube, food selection depends on tube size and location within the GI tract, availability and cost of products, clinician preference, and patient tolerance. The importance of providing adequate protein and calories during recovery cannot be over-emphasized. Protein should be restricted only if there is clear evidence of hepatic encephalopathy (mental depression, altered mental state, excessive drooling, etc.) A liquid veterinary food product, such as Feline Clinicare, is often the easiest option for NE tube feeding, as a liquid diet will not risk clogging the tube and can be used as a continuous drip feeding, if necessary. Although commercially available syringeable diets, such as Hill's a/d, are better suited to feeding through an esophagostomy or gastrostomy tube, a/d can be fed through a 5-8 French NE tube. Care must be taken to use a blender to liquefy the food well by blending it with a small amount of water.
The feeding schedule is determined by the patient's ability to tolerate food and the logistics of feeding. Resting energy requirement (in kcal) is easily calculated as 30 x body weight in kg + 70. Many animals are initially volume sensitive after a period of prolonged anorexia. In such cases, feeding one-third of their energy requirements over day 1 and then increasing the amount by one-third every 24 hours may be better tolerated than schedules that increase the feeding volume faster. If the animal has been anorexic for a few days or less, then a faster "ramp up" to full feeding can usually be accomplished.
Foods should be warmed to room temperature, but not higher than body temperature, before feeding. Food boluses must be infused slowly (approximately 2-3 minutes) to allow gastric expansion. Daily food dosage should be divided into several meals according to expected stomach capacity. Capacities for cats, for example, are approximately 5 to 10 ml/kg during initial food re-introduction. Research in people has demonstrated that the stomach does not "shrink" during a prolonged fast, but rather the stretch receptors are more sensitive, and, as a result, are stimulated by a smaller volume when refeeding occurs. Feeding should be stopped at the first sign of gulping, retching or salivating, the meal size reduced by 25-50% for 1-2 feedings and then increased gradually. Patients that are unable to tolerate bolus feeding without vomiting often benefit from a slow, continuous drip administration (by pump or gravity flow) of a liquid diet. Antiemetics are used routinely in patients with a history of vomiting (metoclopramide 0.2-0.4 mg/kg SC q6-8 hrs or dolasetron 0.6 mg/kg IV q24 hrs).
Each meal must be followed by a water flush to clear the tube of food residue. The tube is capped between feedings. When the patient is volume sensitive, it is important to know the minimum volume required to flush the tube. The patient's daily fluid requirement must also be met and additional water may be administered through the feeding tube to meet that requirement. Liquid oral medications may also be administered through NE feeding tubes. Resist the temptation to crush pills to administer them through an NE tube.
Complications that occur at the time of tube placement include patient resistance (causing stress), nasal bleeding, and inadvertent placement into the trachea (be sure to follow the steps listed above to verify the location of tube placement!).
Once the tube is in place, the most common complication is premature removal by the patient. We use a "three strikes and you are out" rule and will only replace a tube twice before moving to a more durable tube type, such as esophagostomy. Some patients, especially cats, can use the base of their tongue to bring the end of the tube out of the esophagus into the pharynx, resulting in the need to replace it even if an Elizabethan collar keeps their paws away from the tube. This possibility also means that the tube should be checked visually prior to each feeding.
Dacryocystitis may occur with NE tube use, however it resolves rapidly after tube withdrawal. Tube clogging is a real problem if a non-liquid diet or medications are introduced into small diameter tubes. Although cola products have been used for tube flushing in such circumstances with anecdotal success, the literature supports using water flushes to re-establish tube patency. Tubes placed (incorrectly) as indwelling tubes that traverse the lower esophageal sphincter (nasogastric tubes) can lead to serious esophagitis and, in time, life-threatening esophageal stricture formation.