Joseph W. Bartges, DVM, PhD, DACVIM, DACVN
In order to provide complete patient care, nutritional support should be part of the therapeutic plan. Providing nutrition may accomplish several goals (Table).
Goals of nutritional support
1. Minimize metabolic derangements
a. Maintain hydration
b. Attenuate acid-base disorders
c. Attenuate electrolyte disturbances
d. Provide disease-specific nutrients
2. Provide nutrients to facilitate recovery
a. Suppress hypermetabolic response
b. Restore or reverse protein catabolism and negative nitrogen balance
c. Maintain gastrointestinal tract integrity and function
d. Optimize immune function
3. Maintain lean body mass and body weight
4. Avoid complications associated with refeeding
There are 2 main "Golden Rules" of nutrition: 1. If the gut works, use it, and 2. Keep it simple.
There are several different techniques available that facilitate "using the gut". These include forced feeding, appetite stimulation, and tube feeding. Feeding tubes offer a means to provide nutrition to an animal that is unable or unwilling to consume food. Placing a tube within the gastrointestinal tract may provide enteral feeding. Such tubes include orogastric, nasoesophageal, pharyngostomy, esophagostomy, gastrostomy, and enterostomy tubes.
a) Orogastric feeding tube
These tubes are often used to provide nutrition to orphaned puppies and kittens. They are not left in, but are inserted at each feeding.
b) Nasoesophageal feeding tube
Nasoesophageal feeding tubes are technically easy to place, and can be used safely in many animals. Do not use if the patient is comatose or lacks a gag reflex because of risk of aspiration. Nasoesophageal feeding tubes should probably not be used in animals with esophageal motility disorders. These tubes may be placed without general anesthesia. Complications of nasoesophageal feeding tubes include rhinitis, dacryocystitis, esophageal reflux, vomiting, aspiration, pneumonia, inadvertent tube removal, and obstruction of the tube. Placement of a nasoesophageal feeding tube is accomplished as follows:
1. An 8 French tube may be used in most dogs and cats; however, in small dogs and small cats, a 5 Fr tube should be used.
2. To place the tube, instill 2-4 drops of topical anesthetic into the nasal cavity, and tilt the head back. Do this 2 times.
3. The distal end of the tube may terminate in the thoracic esophagus or stomach. To accomplish this, measure the tube to the last rib. I usually place a small piece of tape as a butterfly to mark the tube and to provide a means of securing the tube once it is passed. Lubricate the end of the tube.
4. Pass the tube into the nasal cavity. In cats, pass the tube ventromedially. In dogs, pass the tube in 0.5 to 1 cm and then push up on the planum nasale while passing the tube in a ventromedial direction. Once it has been inserted a little further, flex the head ventrally to promote passage of the tube into the esophagus and not the trachea. When the animal swallows, continue passing the tube into the esophagus to the level of the butterfly piece of tape.
5. If it cannot be passed beyond the level of the medial canthus, it is probably in the dorsal meatus. Withdraw and redirect.
6. Secure tube using 3-0 nylon and the butterfly tape. Dogs usually require Elizabethan collars to prevent dislodging.
Nasoesophageal feeding tubes are easy to place and maintain. Many dogs and cats will leave them alone as long as there is no tension placed on the skin of the face. Prior to feeding, you should insure that the tube is still within the esophagus. This can be done by infusing 5-10 ml of warm tap water and observing for coughing, or by injecting 5-10 ml of air while ausculting over the abdomen for "gurgling" as air moves into the stomach. Complications of nasoesophageal feeding tubes include irritation at the nares, dacryocystitis, inhibition of voluntary food intake, and migration of the tube into the respiratory cavity. If an 8 French tube is placed, convalescent therapeutic diets may be blended and administered; however, if a 5 French tube is placed, then only liquid diets may be administered.
c) Pharyngostomy feeding tube
These tubes are not routinely used.
d) Esophagostomy feeding tube
Esophagostomy tubes are easy to place, and a large bore (> 12 French) feeding tube may be placed in most animals. The advantages of an esophagostomy feeding tube are that there is no interference with voluntary consumption of food, and that gruels may be used because of the size of the tube used. Furthermore, because the tube exits caudal to the oropharynx, esophagostomy tubes provide a means of bypassing the oral cavity and do not interfere with voluntary food consumption when the animal recovers. Esophagostomy tubes must be placed under heavy sedation or general anesthesia. It can be placed surgically, or by using a blind percutaneous gastrostomy feeding tube applicator such as the ELD PGFTA (Jorgenson Laboratories). In all placement methods, the tube is fixed in place with a friction suture or tape "butterfly". The tube is capped and bandaged so that the feeding port exits behind the animal's head. Many cats do not tolerate bandages that encompass their neck; therefore, I do not wrap esophagostomy tubes in cats. The ostomy site is allowed to heal by granulation and epithelialization when the tube is removed. Esophageal has not been reported to occur unless the distal tip of the tube terminates in the stomach, which may cause gastroesophageal reflux and esophagitis. They should not be used in dogs with esophageal motility disorders.
e) Gastrostomy feeding tube
Gastrostomy feeding tubes may be placed surgically through a small laparotomy incision or at time of abdominal surgery, or non-surgically using an endoscope (percutaneous endoscopic gastrostomy tube) or non-endoscopically (blind placement using an ELD PGFTA, the gastrostomy introducer (Cooke Veterinary Products), or using a stomach tube). Advantages of a gastrostomy tube are that they can be used in animals with esophageal or higher disease, a large bore feeding tube (16 to 24 French) can be used so pet food gruels may be administered, they can be used for extended periods of time (months to years), and there is no mechanical inhibition of voluntary food consumption. A gastrostomy tube placement device can be prepared by purchasing a length of vinyl or stainless steel tubing from a hardware store. The length of the tubing is determined by measuring the distance from the nasal planum to the iliac crease and adding 15 cm. The outer diameter of the tube ranges from 1.2 cm (patients weighing <12kg) to 2.5 cm for dogs weighing >25kg. The distal tip of a stainless steel tube can be flared and deflected 45o to the long axis of the tube to help displace the lateral body wall. The lubricated tube is passed through the mouth and into the stomach. The tube is advanced until the end of the tube displaces the stomach laterally. Positioning the animal with its head over the edge of the table and lowering the proximal end of the tube will facilitate identifying the tube tip through the body wall. A percutaneous needle is introduced into the lumen of the tube while the assistant firmly holds the distal tip of the tube between two fingers. A skin nick is made over the end of the tube and a 14G over-the-needle catheter is advanced into the lumen of the tube. Proper positioning of the catheter is confirmed by moving the hub from side to side and feeling the catheter tip strike the inside of the tube. A guide wire prepared from a banjo string or cerclage wire is threaded through the catheter, into the tube, and out of the mouth of the patient. The tube and catheter are removed and the wire is attached to a gastrostomy tube, which is secured. The tube is then pulled into the stomach and through the abdominal wall by placing tension on the wire at the abdominal wall exit site. Gastrostomy tubes can also be placed by using commercially available devices (the ELD PGFTA or the Cooke gastrostomy introducer). The ELD PGFTA is the only device that utilizes an internal trocar, whereas the Cooke gastrostomy introducer contains a wire that is threaded through an introduction needle. Dogs and cats tend to tolerate gastrostomy feeding tubes well. In addition, a low profile gastrostomy feeding tube device may be used for extended periods of time. Complications with use of gastrostomy feeding tubes include vomiting with risk of aspiration pneumonia (often associated with administering cold food or food too quickly), dislodgement of the tube which may result in peritonitis or cellulitis, peristomal infections, and difficulties in maintaining bandages on dogs and cats. Additionally, penetration of the spleen, stomach, or omentum may occur if the stomach is not insufflated with air prior to positioning the tube against the lateral abdominal wall. When managing a gastrostomy feeding tube, it is important for the ostomy site to be observed and cleaned daily. Contraindications to using the blind techniques include severe obesity, ascites, and esophageal disease.
f) Enterostomy feeding tube
Enterostomy feeding tubes are usually 5 French tubes that are placed directly into the duodenum and/or jejunum. An advantage of an enterostomy feeding tube is that they bypass the stomach and so can be used in animals undergoing gastric surgery or in dogs with pancreatitis. However, they must be placed surgically, and only liquid enteral diets may be used through a 5 French feeding tube. Placement of an enterostomy feeding tube can be done at the time of surgery; therefore, careful planning is necessary to avoid a second surgery. An enterostomy feeding tube should be placed in the descending duodenum or jejunum. The tube should travel in the wall of the small intestine for a few centimeters before it enters the lumen of the small intestine. The distal end of the tube should be 20-30 cm from the site of entry into the small intestine. The feeding end of the tube should exit the lateral abdominal wall. Usually, liquid diets are administered through enterostomy feeding tubes. It is difficult to pulverize medications into a fine enough powder to prevent them from occluding enterostomy tubes; therefore, administer only liquid medications.