How to manage indwelling feeding tubes in critically ill dogs and cats

Naso-enteric tubes

Nasogastric (NG) or nasoesophageal (NE) feeding tubes are indicated in cases where short-term (< 7–10 days) assisted feeding is required and where general anaesthesia is contraindicated (Figure 1) (Perea, 2008; van Schoor, 2010). Patients require a functional oesophagus, stomach and small intestines (Wortinger, 2006). These tubes are easy to place and fairly inexpensive (Perea, 2008). The advantage of NG tubes is that gastric content could be aspirated if indicated (van Schoor, 2010). It was previously theorised that nasogastric (NG) feeding tubes were associated with more complications because they would interfere with closure of the lower oesophageal sphincter. However, a recent study showed that complication rates with naso-enteric tubes were quite low and complication rates between NG and NE tubes were not significantly different (Yu et al, 2013). Their use is contraindicated in patients with severe trauma to the nares and nasal turbinates, uncontrolled vomiting or regurgitation, absence of a gag reflex, comatose patients, decreased oesophageal function and severe bleeding tendencies (van Schoor, 2010). Feeding via these tubes can start immediately after placement. The patient will be able to consume food orally with the tube in place and when it is no longer required, the suture or glue anchor can be clipped and the tube removed (Marks, 2010a).

Oesophagostomy tubes

The use of oesophagostomy tubes is indicated when feeding is required for more than 7–10 days in patients with a functioning, unobstructed oesophagus and healthy gastrointestinal tract (Prittie and Barton, 2004). In patients with disorders of the nasal passages, jaw bones, oral cavity or pharynx oesophagostomy tubes bypass the injured site and enable enteral feeding (Wortinger, 2006; Cruikshank, 2010). These tubes have slightly larger diameters than NG and NE tubes, allowing for the feeding of larger particles (gruel) of food and are less likely to become blocked (Perea, 2008). They are more comfortable for the patient compared with nasal tubes. Placement requires a short general anaesthesia, but the procedure is fairly simple and quick (Figure 2) (Perea, 2008). Placement techniques are described in the literature (Cruikshank, 2010; Marks, 2010a).

Feeding can start as soon as the patient has recovered from the anaesthesia and is able to stay in sternal recumbency. After 10 days and when the tube is no longer required the sutures are clipped and the tube is removed slowly. A light bandage is placed over the opening for the first 12 hours and the wound is left to heal by second intention (Figures 3 and 4.).

Gastrostomy tubes

Gastrostomy tubes are indicated in patients where oesophageal disease precludes the use of oesophageal feeding. These tubes are indicated for longer-term feeding and due to their larger diameter, larger particles (gruel) can be tube fed (Perea, 2008). General anaesthesia is required for placement and the tubes are either placed surgically or endoscopically (Figure 5) (Perea, 2008).

A variety of feeding tubes are available for use as gastrostomy tubes (Marks, 2010a). These include tubes with French-Pezzer mushrooms, balloons, bumpers or dome tips. Placement techniques are described in the literature (Marks, 2010a).

Feeding can start 12–24 hours after placement (Marks, 2010b) (Figures 6 and 7). After 10–14 days when a permanent stoma is formed and when the tube is no longer required, it can be removed by gently pulling it through the stoma (Wortinger, 2006). The wound is covered with a light dressing for 12 hours and left to heal by second intention.

Jejunostomy tubes

Jejunal tubes are indicated in patients with functional problems of the proximal gastrointestinal tract (Prittie and Barton, 2004). These include persistent vomiting, gastric outflow obstruction, partial gastrectomy and recurrent aspiration (Perea, 2008; Marks, 2010a). Tube placement requires general anaesthesia and is done surgically, endoscopically, laparoscopically or nasojejunal (Heuter, 2004). Placement techniques are described in the literature (Heuter, 2004; Hitt, 2010).

Patients can be fed from 6 hours after placement (Marks, 2010b). These tubes need to be left in place for 10–14 days to allow stoma formation. They are removed by gently pulling them through the stoma and the wound is left to heal by second intention (Wortinger, 2006).

Placement technique for naso-enteric tubes

Placement of the tube requires minimal manual restraint of the patient, but some patients may require mild sedation (van Schoor, 2010). The size of tube selected depends on the size of the patient. Approximate sizes are: for puppies and kittens 3 French gauge; for cats and small dogs 5 French gauge; for larger dogs 8 French gauge; and for giant breed dogs 12 French gauge or larger (van Schoor, 2010). The largest tube that would be able to pass through the nares is selected and pre-measured from the tip of the nares to the level of the sixth intercostal space for NE tubes or the ninth intercostal space for NG tubes (Figure 8). A marker is placed to indicate the correct length (Figure 9). Up to 0.5 ml of lignocaine is instilled in each nostril and left for 1–2 minutes to take effect (Figure 10). Both nostrils are anaesthetised in case it becomes necessary to change nostrils during the procedure. The tube is lubricated with obstetric cream or lubrication jelly and is then directed ventro-medially into the nostril and passed via the ventral meatus. In dogs the nose is gently pushed upwards for easier passage (Figure 11). The neck is slightly flexed to enable the animal to swallow during placement. The tube is advanced to the level of the marker after which it is secured to the side of the face using a suture or quick-drying glue, avoiding the whiskers in cats (Figure 12). The first point of attachment should be as close to the nares as possible.

Because of the risk of tracheal intubation it is important to verify correct placement of the tube (Perea, 2008; van Schoor, 2010). The author prefers making a lateral thoracic radiograph to confirm placement of the tube in the oesophagus (NE) or stomach (NG) (Figure 13). In most patients an Elizabethan collar is placed to prevent the animal from removing the tube (van Schoor, 2010).

Complications with the use of feeding tubes

Complications that could occur with naso-enteric tubes include epistaxis during tube placement, tracheal intubation, dacrocystitis, rhinitis, aspiration pneumonia, vomiting, regurgitation and blocked or dislodged tubes (van Schoor, 2010; Yu et al, 2013). Blockage of the tubes occurs due to the small lumen of these tubes that need to be thin enough to pass through the nasal passage.

Complications with the use of stoma-forming tubes include peristomal infections, tube kinking and blockage, vomiting and regurgitation and tube displacement (Perea, 2008). Leakage around the tube or premature removal of the tube could lead to life-threatening peritonitis in the case of gastrostomy and jejunostomy tubes (Wortinger, 2006; Perea, 2008). These tubes should be left in place for at least 7–10 days to allow for healing of the stoma (Marks, 2010a). In the case of jejunal tubes abdominal cramping and osmotic diarrhoea could occur (Perea, 2008).

Calculating the energy requirements

Critically ill patients should start receiving resting energy requirements (RER) as soon as they are haemodynamically stable. It is not necessary to feed patients more than RER (Chan and Freeman, 2006; Brunetto et al, 2010; Marks, 2010b). In fact, overfeeding and its detrimental effects occur when more than RER is fed to a patient (Chan and Freeman, 2006). Nutritional state of patients is monitored daily and should it become evident that a patient requires more nutrition than what is being provided, the number of calories can be increased by up to 25% at a time (Chan and Freeman, 2006).

The requirements are calculated using the following formulae (Marks, 2010b):

For animals > 2 kg < 45 kg bodyweight (BW) use the simple linear formula:

For all animals the allometric formula can be used:

Refeeding syndrome

If patients receive too much food when feeding is first introduced it could lead to a number of metabolic derangements which are referred to as the ‘refeeding syndrome’ (Michel, 2004; Wortinger, 2006). When feeding is introduced after prolonged starvation and muscle catabolism, rapid intracellular shifts of electrolytes can occur once the intracellular compartment starts re-expanding. This results in, amongst others, hypophosphataemia, hypokalaemia and hypomagnesaemia. Clinical manifestations of refeeding syndrome include muscle weakness, cardiac arrhythmias, respiratory depression, intestinal ileus and haemolysis (Michel, 2004; Wortinger, 2006). Refeeding syndrome can be avoided by initially feeding 25–50% of RER and gradually increasing the energy supply over a period of a few days until 100% RER is being fed (Marks, 2010b). The patient is closely monitored for clinical signs and serum electrolyte changes, and electrolytes are supplemented when indicated (Wortinger, 2006). Vomiting and diarrhoea could result from feeding large volumes of food via a previously starved intestinal tract. By gradually increasing the energy supplied and the volumes administered, these complications are avoided.

Types of diets and volumes fed per meal

Current nutrient recommendations in canines and felines suggest that hospitalised dogs be fed 4–6 g of protein per 100 kcal (15–25% of total energy requirements) and cats be fed >6 g of protein per 100 kcal (25–35% of energy requirements) (Remillard et al, 2000; Chan and Freeman, 2006). Most enteric liquid formulae used in humans contain less than 20% protein and long-term use for more than 2 weeks is contraindicated, especially in cats (Marks, 2010b). The choice of diet will depend on the size of the tube and the affordability of the product. In some countries products such as Abbott Clinicare Canine/Feline liquid diet® are available, but quite costly (Marks, 2010b). Commercially available canned small animal diets are ideal, as they will supply the correct amount and ratio of nutrients, and many of these diets, once blenderized, can be fed via feeding tubes (Figure 14). In the author's hospital diets including Royal Canin Recovery®, Hill's canine/feline a/d® or Hill's feline i/d® are blenderized and fed even via small tubes such as naso-oesophageal tubes. In patients where tube diameter is too small even for blenderized food, a small amount of water can be blended with the food to make it even more liquid. Unfortunately this does also dilute the nutrients and increases volumes that need to be fed. Diets such as Eukanuba High Calorie® can be mashed, diluted and fed via larger tubes such as oesophagostomy and gastrostomy tubes. The caloric density of commercial diets are available from the manufacturers and in the literature (Marks, 2010b, Proulx, 2002). For example: Hill's canine/feline a/d® contains 8.8 g protein/100 kcal and provides 33% protein as % of total energy requirements. It has a caloric density of 1.1 kcal/ml.

Using feeding tubes

Daily food volumes are calculated and divided into approximately six meals (Marks, 2010b). Food is warmed to body temperature prior to feeding (Figure 15). In tube fed animals, the feeding tube is flushed with warm water (5–20 ml depending on patient size and tube volume) at each meal prior to feeding and immediately after feeding to avoid blocking of the tube (Marks, 2010b). When calculating daily fluid requirements these volumes of water need to be taken into account to avoid over supplementation of daily fluids. Maximum tolerable feeding volumes in debilitated dogs and cats can be estimated as 5–10 ml/kg bodyweight initially (Box 1). Patients that do not tolerate larger volumes can be fed very small volumes more often and in certain patients continuous rate infusion (CRI) feeding may be preferred (Marks, 2010b). By slowly trickling food into the stomach as a CRI, sudden distension of the stomach is avoided and vomiting is minimised. When making use of CRI the infusion needs to be interrupted every 8 hours and the residual stomach volume determined via suction on the feeding tube to ensure that delayed stomach emptying (Marks, 2010b) resulting in over distension of the stomach is not a problem. Metoclopramide may be administered at 1–2 mg/kg/24 hours to promote gastric emptying, decrease residual volume and prevent vomiting (Marks, 2010b).

Example: calculating feeding volumes

Patient: Mixed breed dog; 4 years old; weight 10.6 kg

Caloric requirements: Resting energy requirement (RER) = (Bodyweight × 30) + 70 = (10.6 × 30) + 70 = 388 kcal/day

Caloric density of food: Hill's canine/feline a/d contains 1.1 kcal per ml

Food volume: RER ÷ food density = 388 kcal ÷ 1.1 kcal/ml = 352.7 ml

Maximum initial meal volume: Estimated at 5–10 ml per kg bodyweight

In this case: 10.6 kg × 5–10 ml = 53–106 ml.

This dog can safely be fed the calculated volume of food and the tube can be flushed with approximately 10 ml water prior to and after feeding. The total volume would be 10 ml water + 60 ml food + 10 ml water = 80 ml. Even at 100% RER this amounts to less than 106 ml given via the tube at each meal.

Keeping feeding tubes clean

Flushing the tube before and after is feeding is crucial. Tube obstruction can cause a lot of frustration (Michel, 2004). Attempts to unblock the tube with warm water flushing followed by suctioning are often not successful. Sodium bicarbonate (Michel, 2004) added to the water may offer more success. One could also use a mixture of pancreatic enzyme, sodium bicarbonate and water (Michel, 2004). Unfortunately it may be necessary to replace a blocked tube (Michel, 2004).

Nutritional assessment and patient monitoring

The World Small Animal Veterinary Association (WSAVA) and the American Animal Hospital Association have published guidelines for the nutritional assessment of dogs and cats (Baldwin et al, 2010; WSAVA, 2011a). The five standardised vital signs which make up part of the clinical examination now include temperature, pulse, respiration, pain assessment as well as nutritional assessment (WSAVA, 2011a). Detailed descriptions of nutritional assessment guidelines are available as part of a nutrition toolkit published on the WSAVA website (WSAVA, 2011b). Apart from obtaining a thorough nutrition history, animals should be weighed on a daily basis and additional parameters such as body condition score, muscle condition score, serum proteins and serum electrolytes assessed from time to time. The nutritional plan should be evaluated daily and adjusted according to the patient's changing needs. A very useful WSAVA monitoring sheet is available for use in the hospital (WSAVA, 2011b). Constant monitoring will ensure that animals maintain body condition during hospitalisation as far as possible (Figure 16).

Conclusion

Assisted feeding using feeding tubes can improve outcome and decrease duration of hospitalisation in critically ill dogs and cats. Providing RER will prevent the deleterious effects of malnutrition. It is easy to implement and needs to be considered as part of the therapeutic plan in small animal patients.