Instead of viewing anorexia as a secondary problem that will improve when the primary disease has resolved, it is now well
recognized that 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. There are several methods of enteral feeding. The first attempt is usually to offer a choice of palatable
foods, followed by assisted oral feeding by hand or syringe. Appetite stimulants may be used successfully to induce food consumption
in some patients (cyproheptadine 1 mg/cat/day or mirtazapine 1/8-1/4 of a 15 mg tablet/cat q72 hrs.) With each of these techniques,
the amount of food consumed must be closely monitored to be certain it approximates the animal's RER.
Orogastric tubes require placement at each feeding but may provide a useful option for one to two days of feeding. Neonates
appear to tolerate multiple oral tube feedings daily better than adults. 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. Tube placement
should be in the most proximal functioning portion of the GI tract possible via the least invasive method. Nasoesophageal
tubes are used most frequently to provide enteral nutritional support.
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 head 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. Other
indications for placement include delivery of fluids or liquid medications and diagnostic testing (e.g. nasogastric tube for
contrast radiography). 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 to end 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. Polyurethane tubes (with or without a tungsten-weighted tip) and silicone
feeding tubes may be placed in the caudal esophagus. 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 facial, maxillary, or nasal trauma or disease. Severe debilitation/lateral recumbency may provide a relative
contraindication.
Supplies Needed
5 French 36" or 8 French 42" feeding tube with a 0.025" or 0.035" angiography guide wire stylet
Topical anesthetic; 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
Elizabethan collar
