How to place commonly used feeding tubes in dogs and cats

NO and NG tubes

NO and NG tubes provide short-term enteral nutritional support, generally for up to 5 to 10 days, and are suitable for use in patients for whom sedation or general anaesthesia is contraindicated (Aicher and Tobias, 2013). In addition to feeding, NG tubes can also be useful for aspirating residual gastric fluid in conditions such as ileus. The type of diet used is limited by the narrow bore of the tube, typically 3.5–6 Fr in cats and 8–10 Fr in dogs, to low viscosity and nutritionally complete liquid diet formulations. Examples include Royal Canin liquid diets, Formula V® EnteralCare™ KC (PetAg), CliniCare® (Zoetis) and Rebound® liquid diet (Virbac Animal Health).

Despite the selection of an appropriate diet, blockages remain a potential risk and can be minimised through careful flushing before, and after, feeding and by avoiding the administration of oral medications via NO and NG tubes. These feeding tubes are contraindicated in patients that are laterally recumbent or dyspnoeic and for those with altered consciousness, facial trauma, oesophageal dysfunction/obstruction or an inability to protect their airway. Use in patients with raised intraocular and intracranial pressure should also be avoided due to the risk of sneezing during placement. Potential complications of placement also include epistaxis, therefore care should be taken in patients with thrombocytopenia or coagulopathies.

Placement of NO and NG tubes

Ensure that the patient is restrained securely. The head should be held in a normal functional position, avoiding hyperextension or hyperflexion (Figure 1). The VS should decide if sedation of the patient is required and make the necessary arrangements for this to be done.

Tilt the patient's head upwards and place 4–5 drops of lidocaine, or proparacaine, hydrochloride solution into the nostril(s) (Figure 2). Application into both nostrils enables either to be used as required. Allow several minutes to take effect. The local anaesthetic may have a bitter taste, resulting in hypersalivation by the patient. Some practitioners also recommend adding a drop of proxymethacaine or lidocaine to the eye to aid in numbing the nasal passages.

If placing a NO tube, the distance from the nose to the seventh or eighth intercostal space should be measured. If placing a NG tube, the nose to the last rib should be measured. This position should be marked on the tube with a permanent marker pen or a small piece of tape.

To aid insertion, the tube can be lubricated with a water-soluble, or lidocaine, gel.

With the patient in a standing, sitting or sternally recumbent, position, one hand will steady the patient's head in a neutral position while the other inserts the tube. Cats: the tube should be inserted in the medial aspect of the nares and directed in a caudoventral direction. Dogs: the tube should be directed ventromedially and into the ventral meatus of the nasal cavity. Applying gentle pressure in between the nares can facilitate opening and elevate the proximal end of the tube, aiding insertion (Figure 3). A confident motion can prevent stimulation of sneezing.

The tube is passed until it reaches the predetermined position (nose to intercostal space). If resistance is felt, the tube should be withdrawn and redirected in a ventral direction.

To prevent unintentional removal, or displacement, the tube should be secured before verifying its position. One of the common methods used to confirm correct placement is to instill sterile saline down the feeding tube and observe for signs of coughing. The volume must be adapted for the size of patient but is usually between 1 and 5 mls. There should be no gurgling when auscultating the chest. More accurate methods involve either:

Connecting the feeding tube to a portable capnograph. A lack of visible waveform and an end-tidal carbon dioxide measurement of 0 mmHg will verify correct tube placement.

Taking survey or contrast radiographs of the thorax

pH assessment of fluid aspirated from the tube (Figure 4)

Aspiration with a syringe to check for a vacuum.

Securing of the tube can be achieved using square knot or finger trap sutures (with or without tissue glue) or skin staples, at a point level with the forehead or buccal pouch on the lateral face (Figure 5). The application of EMLA cream to the patient's nose or forehead prior to placing, and securing, the tube can increase patient comfort and compliance.

To prevent patient interference and premature removal of the tube, a buster collar should be fitted. Once the tube is no longer required, it can be easily removed by cutting the suture material, or removing the staples, and pulling the tube out.

Oesophagostomy tubes

For patients requiring longer-term nutritional support and/or bypass of the oral cavity or oropharynx, oesophagostomy tubes are well tolerated and can be managed by owners at home. The larger bore (14–20 Fr) allows the feeding of a broader selection, and volume, of food, including blenderized diets. Despite these advantages, limitations include surgical placement, warranting general anaesthesia. Endotracheal intubation of the patient is desirable however, as reported by Boveri and Brearley (2015), care must be taken by the VS to avoid entrapment during placement of the feeding tube. Further, serious, complications include inadvertent placement in the trachea, or mediastinum, and damage to major vessels or nerves, therefore surgical competence should be assured prior to placement, together with careful verification of correct positioning afterwards.

Oesophagostomy feeding tubes are contraindicated in patients with persistent vomiting, altered consciousness and for those with oesophageal disorders or who have undergone oesophageal surgery. They can also be challenging to place in giant breeds or obese patients (Hodshon and Tobias, 2014). Feeding can begin immediately following placement (Eirmann, 2015), but should be instigated in consultation with the VS. To reduce the risk of aspiration pneumonia, patients should have recovered fully from anaesthesia and be able to support themselves in a sternal position.

Placement of oesophagostomy tubes

Proper placement of an oesophagostomy feeding tube requires the distal tip to be placed in the mid cervical oesophagus to the level of the fifth to ninth intercostal space. This may require premeasuring of the tube.

ather than cutting the distal tip and creating a sharp edge, the exit side hole should be elongated using a small blade. This will help prevent clogging of food.

The patient should be anaesthetised and preferably intubated. While in right lateral recumbence, the left side of the neck should be clipped and aseptically prepared using a routine surgical scrub (Figures 6 and 7).

With the tips facing outwards, a curved Rochester-Carmalt forcep (or a curved haemostat) is placed into the mouth and down the oesophagus to the mid-cervical region (Figure 8). The jugular vein should be identified and avoided.

The tip of the Carmalt is pushed dorsal to the jugular vein, pressing the oesophagus towards the skin.

The tip of the Carmalt is palpated over the skin to confirm its location (Figure 9). Avoiding any nearby neurovascular structures, a stab incision is made through the skin and into the oesophagus. The mucosa of the oesophagus is relatively more difficult to incise than the skin.

The tip of the instrument is pushed through the incision, which can be slightly enlarged with the blade.

The Carmalt is opened slightly and tip of the oesophagostomy tube is placed within the jaws of the instrument (Figure 10).

The Carmalt is then clamped closed and pulled from the oral cavity (Figure 11).

The tips of the Carmalt are disengaged and the tip of the tube is curled back into the mouth and fed into the oesophagus (Figure 12). As the curled tube is pushed into the oesophagus, the proximal end is gently pulled simultaneously.

This will result in a subtle ‘flip’ as the tube is redirected within the oesophagus. The tube should easily slide back and forth a few millimeters, confirming that the tube has straightened within the larynx (Figure 13).

A visual inspection will confirm that the tube is no longer present within the oropharynx.

A thoracic radiograph will confirm correct placement of the tube in the mid to distal oesophagus (Figure 14). The tip of the tube should not pass beyond the lower oesophageal sphincter (Figures 15 and 16) as this can cause irritation and predispose the patient to gastric reflux (Hodshon and Tobias, 2014).

The tube is secured using a Chinese finger trap, or Roman sandal, suture pattern (Figure 17). The use of a purse-string suture around the stoma is documented, but associated with cellulitis and peristomal inflammation (Hodshon and Tobias, 2014).

The incision site can be gently cleaned before placing a light bandage (Figure 18). Despite a limited supporting evidence base, some authors, including Eirmann (2015), suggest the application of antibiotic ointment to the stoma site.

While complications associated with O-tubes are generally minor (Hodshon and Tobias, 2014), these may include tube obstruction, stomal infection and abscessation, peristomal dermatitis or cellulitis and inflammation (Ireland et al, 2003). Swelling of the head and neck can also result due to an excessively tight bandage. While rare, vomiting can lead to dislodgement of the tube, resulting in a foreign body. Once oral food intake is sufficient to meet the patient's caloric requirement, the tube can be removed. This can easily be performed by cutting the suture material and pulling the tube, leaving the wound to heal via second intention.

Gastrostomy tubes

Gastrostomy feeding tubes offer the provision of mid to long-term nutritional support via entry into the stomach; adequate gastrointestinal function is therefore essential (Marks, 2009). The wide diameter tube, often 15 Fr for cats and 19–24 Fr for medium to large dogs, enables easy administration of food from a wider selection of diets in comparison to smaller diameter tubes. Placement requires general anaesthesia and either laparotomy or percutaneous approach, the latter involving a blind or endoscopic technique using specialised equipment. Feeding is generally delayed for at least 12–24 hours with either method (Snyder, 2009) and endoscopic placement can affect gastric motility for up to 3 days (Gajanayake and Chan, 2015). Tubes usually remain in place for a minimum of 7 to 10 days, often longer in hypoproteinaemic or immune-compromised patients. This allows adequate adhesions to form between the stomach and abdominal wall, preventing leakage of stomach contents and subsequent peritonitis (Snyder, 2009).

The use of gastrostomy tubes is contraindicated in patients with persistent vomiting, gastrointestinal obstruction, compromised gastric wall and altered consciousness (Marks, 2009). Endoscopic placement in larger breeds of dog (weighing 30 kg or over) is also contraindicated due to tendency for migration of the feeding tube and subsequent peritonitis (Snyder, 2009). Incorrect placement can cause abdominal visceral injury and pyloric outflow obstruction. Further complications include dehiscence, cellulitis and infection of the stoma site. Overly tight securing of the tube can also result in pressure necrosis. Careful patient evaluation and selection, appropriate selection of feeding tube, correct surgical technique and competence, accurate patient monitoring and adherence to the prescribed feeding regimen can limit potential complications (Gajanayake and Chan, 2015).

Placement of gastrostomy tubes

The following methodology describes the placement of a percutaneous endoscopically placed gastrostomy (PEG) tube using a commercial kit.

The patient should be placed in right lateral recumbence, enabling entry of the tube through the greater curvature of the stomach and left body wall.

Clip and surgically prepare the skin over the lateral abdominal wall and caudal to the left costal arch.

A mouth gag is placed between the right upper and lower canine teeth before the endoscope is passed down into the stomach.

Following slight inflation and distension of the abdomen, the position for insertion of the PEG tube is located on the anterior abdominal wall by either:

Transabdominal impulse — endoscopically visible bulging when the surgical assistant presses the wall (Figure 19) or

Trans-illumination after dimming the light in the room.

Under direct endoscopic view, a small stab incision is made into the stomach, adjacent to the endoscope tip and a 16–18 G, 1.5–2 inch, catheter punctures the body wall and into the stomach (Figure 20).

The needle is removed, leaving the cannula in place.

The placement wire (introduction line) is advanced through the cannula and the loop is grasped with endoscopic retrieval forceps (Figure 21).

The wire is then pulled out through the mouth as the endoscope is withdrawn.

The placement wire is looped through the PEG tube.

Gentle traction is applied to the placement wire through the puncture cannula, while guiding the PEG tube through the mouth (Figure 22).

When the tip of the PEG tube reaches the puncture cannula, some resistance will be felt. The puncture cannula is removed and the conical end of the PEG tube is gently pulled through the incision. It may be necessary for the VS to extend the incision slightly using a scalpel blade.

The PEG tube is pulled through the abdominal wall until the inner retention plate (mushroom tip) touches the inner gastric wall (Figure 23).

The guiding thread of the PEG tube is cut close to the cone. A plastic fixation plate and clamp is placed over the tube before it is capped (Figure 24). In cases of prolonged use, PEG tubes can be modified to be low-profile.

A light bandage, or stockinette, can be fitted to protect the tube. A non-adhesive dressing, with or without antibiotic ointment, can be used to cover the stoma site.

Once oral food intake is sufficient to meet the patient's caloric requirement, the tube can be removed. In medium to large dogs, the PEG tube can be cut close to the body wall and the mushroom tip pushed into the stomach and passed via faeces. For cats and small dogs, this method could result in intestinal obstruction and thus, the tube can be removed using quick traction via the stoma site or via anaesthesia and endoscopic retrieval via the mouth (Han, 2004). The gastrointestinal tract should seal with minimal or no leakage within 24 hours.

Feeding tube management and prevention of complications

The following points should be considered in the use of all enteral feeding tubes:

Conclusion

This paper has provided a practical overview of the steps involved in placing commonly used feeding tubes. For further information regarding the underpinning evidence base, principles and nursing care associated with the use of this, and other, assisted feeding techniques, readers are advised to consult the list of references provided.

Key Points