Early enteral nutrition was considered by Frye et al (2015) as being a gold-standard method of providing nutritional assistance to patients in veterinary practice, provided there is a functional gastrointestinal (GI) tract. O'Dwyer (2017) and Ackerman (2019) have both stated that enteral feeding in critically ill patients would stimulate the GI tract and in turn, help to reduce the incidence of bacterial translocation. This problem occurs through the migration of bacteria from the GI tract to lymph nodes and other internal organs (Jones and Ackerman, 2016a; O'Dwyer, 2017); sepsis associated with the GI tract can occur (O'Dwyer, 2017). This process could occur in any patient in veterinary practice not receiving enteral nutrition, not just the critically ill. This article will explore some indications for early enteral nutrition, the benefits that this can bring and finally, discuss a main complication that can arise from not providing early enteral nutrition. Specific methods of delivery will be mentioned but not discussed in detail as this is not within the scope of this article.
Indications for early enteral nutrition
Eating was specifically considered in the Ability Model's patient assessment framework (Orpet and Welsh, 2011), demonstrating that this should not be overlooked while creating a nursing care plan (NCP). This highlighted how important it is that nutrition is planned properly for each individual in order to provide holistic care for patients (Orpet and Welsh, 2011). Alongside providing the appropriate calorie intake, the method of delivery should be carefully considered and accurately documented on the NCP in order to ensure that consistent standards of nursing care are provided (Bloor, 2019).
Orpet and Welsh (2011) stated that supported nutrition and fluid therapy is needed when a patient has lost 10% or more of their initial bodyweight (Figure 1). This was corroborated by the World Small Animal Veterinary Association guidelines (Freeman et al, 2011), which considered nutritional assessment to be the fifth vital sign. When a patient's history is taken, in addition to the percentage bodyweight loss, other factors that would indicate the need for supported enteral nutrition include the need to bypass certain GI tract areas, anorexia or decreased food intake (Ackerman, 2019). Additional factors, as stated by Ackerman (2019), were an increase in both nutrient demands and losses, as well as acute deterioration of a chronic medical condition. Every patient should have an individualised nutritional plan (Freeman et al, 2011), which should be calculated accurately to meet the individual's resting energy requirements (RER). Hospitalised patients should ideally have their bodyweight checked twice daily, depending on their clinical status (Jones and Ackerman, 2016a), and the registered veterinary nurse (RVN) should regularly review the patient's body condition score and muscle condition score to detect improvement or deterioration, thus giving an indication to the adequacy of the nutrition provision.
There are a multitude of indications for early enteral nutrition, some of which are considered below within the categories mechanical and physiological.
Mechanical indications
Some patients may not be able to ingest adequate calories to meet their individual requirements even if they are willing, with some common mechanical or physical barriers being facial injuries (Griggs, 2014) and recumbency (McDonald, 2017).
Out of all the fractures seen in veterinary practice, jaw fractures account for around 5%, with many of these fractures being repaired utilising external fixation techniques, thus making feeding difficult and indicating the need for assisted early enteral nutrition (Griggs, 2014). Assisted early enteral nutrition should begin as soon as possible post-surgery to aid with healing; an oesophagostomy feeding tube (Griggs, 2014) would allow adequate calorific intake while bypassing the injury. The recommendation of an oesophagostomy feeding tube could extend to patients that have other facial issues, such as those requiring surgery to remove oral masses (Bloor, 2019). These patients may have undergone significant surgery in the oral cavity, meaning that it would be unrealistic to expect that patient to be able to meet their nutritional demands voluntarily. Bloor (2019) advised the same feeding tube interventions as Griggs (2014), adding that a suitable alternative would be a gastrostomy tube. While oral masses might not be commonplace in most veterinary practices, the information discussed by Bloor (2019) served to substantiate the suitability of feeding tubes to provide early enteral nutrition for patients unable to prehend food.
Recumbency can occur with many patients, for example post-surgical and trauma patients through to those with severe mobility issues (McDonald, 2017). The specific nutritional requirement would be dependent on the reason for the recumbency, to include any underlying disease. Recumbency generally causes increased physiological stress for example, ongoing tissue repair (Chandler and Middlecote, 2011), meaning that a higher calorific intake will be required to meet demands. In patients that are not anorexic, voluntary intake may be successful, but only if the food and water is within easy reach for the patient (Chandler and Middlecote, 2011). If assisted feeding techniques are indicated, enteral methods using an appropriate feeding tube would be the suitable choice (McDonald, 2017). It would be difficult to achieve the adequate calorie intake via methods such as hand feeding and syringe feeding, the latter of which can cause unnecessary stress to both patient and RVN, in addition to complications such as aspiration pneumonia.
Physiological indications
Hepatic lipidosis is a disease which is the result of protracted anorexia and an increase in catabolism, the latter being a destructive process where complex molecules such as protein are broken down into simpler ones (Tartaglia and Waugh, 2002). It is the most commonly acquired liver disease of cats and can potentially be fatal (Valtolina and Favier, 2017; Center, 2019); it occurs when the liver is no longer able to use or redistribute fats (Center, 2019), leading to excessive lipid storage in hepatocytes, thus increasing the weight and decreasing the functionality of the liver (Valtolina and Favier, 2017). Early enteral nutrition plays a major role in the reversal of the effects of hepatic lipidosis (Valtolina and Favier, 2017), while avoiding refeeding syndrome (Brenner et al, 2011); the latter will be discussed in the Complications of early enteral nutrition section.
Anorexia can be a clinical symptom of many systemic diseases, for example pancreatitis (Jones and Ackerman, 2016a), parvovirus (Thakur and Thakur, 2017) and chronic kidney disease (Almond, 2017). Molina et al (2018) discussed an association between anorexia being apparent on presentation and there being a higher risk of patient death; there is also an apparent association between inadequate nutrition and death (Molina et al, 2018). On cessation of nutritional intake, the patient's body will go into starvation where catabolism of fats and protein sources occurs (Chan, 2009). When a healthy patient is starved, they will mainly lose fat and glycogen stores, which is characteristic of simple starvation (Chan, 2009). In contrast to this, when an unhealthy patient (due to trauma or illness) is starved, they enter a state known as stressed starvation whereby ca-tabolism of lean mass will occur in order to deliver enough calories to the patient (Chan, 2009). Table 1 shows a short list of conditions and problems that can result in anorexia, the reasoning or physiological indication and basic management advice in relation to early enteral nutrition.
Table 1. Patients may become anorexic for many reasons, some of which are included in this table
| Condition | Physiological indication/reasoning | Management |
|---|---|---|
| Pancreatitis | The autodigestion of the pancreatic cells leads to severe abdominal pain, vomiting and diarrhoea, depression, anorexia (Jones and Ackerman, 2016a) and an overall reduction in quality of life (Watson, 2015) | If there is no vomiting present, then early enteral nutrition via a feeding tube is indicated. The recommendation is a gastrostomy tube or even an oesophagojejunostomy tube, if post-pancreatic feeding is desired (Cummings and Daley, 2014). Reduced incidence of vomiting was observed with oesophagostomy tube feeding (Firth, 2013), and earlier return to voluntary feeding when feeding tubes are used for early feeding (Harris et al, 2017). Early enteral nutrition has been associated with a decreased morbidity and pain in dogs with pancreatitis (Mansfield and Beths, 2015) |
| Parvovirus | Parvovirus kills the germinal epithelium within the gastrointestinal (GI) tract. This causes necrosis of this epithelium and the absorptive capacity is markedly less (van Schoor and Schoeman, 2014). One of the many symptoms of parvovirus is anorexia (Thakur and Thakur, 2017) | Traditionally, these patients were nil per os for a period of around 24 to 72 hours, but more recent guidelines suggested that early enteral nutrition can hasten the clinical improvement of the patient. Feeding is recommended via naso-gastric or nasoenteric feeding tubes to allow for bolus feeding or constant rate infusions (van Schoor and Schoeman, 2014) |
| Chronic kidney disease | A progressive loss of renal function leads to uraemia and when this builds to toxic levels, the patient is likely to vomit and become anorexic (Almond, 2017) | Early intervention with enteral feeding is recommended (Ograin, 2017), with a specific diet to support remaining renal function as well as increasing quality of life (Thornton, 2017). This should be commenced as soon as possible once vomiting is under control |
| Nasal masses | These masses make it difficult for the patient to breathe while eating (Goddard and Irving, 2011), therefore it is likely that there would be a cessation in voluntary food intake | Early enteral nutrition via a feeding tube, bypassing the nasal cavity |
| Any disease process causing nasal discharge such as upper respiratory tract disease | Profuse nasal discharge can cause discomfort (Harris and Rock, 2011) and impair olfaction, which can cause the patient to become anorexic. This is particularly prevalent in feline patients | Clean discharges from nostrils (Harris and Rock, 2011), enteral nutrition should be attempted via warming palatable food to room temperature (Delaney, 2006) increasing the aroma from the food |
Disorders of the GI tract provide an anomaly when considering early enteral nutrition as, if vomiting is present, feeding the patient can be less than ideal; vomiting patients may become candidates for parenteral feeding (Valtolina and Favier, 2017). It was traditionally recommended that there is a 3 to 5-day period of gastric rest following hospitalisation (Firth, 2013) for patients with various GI conditions. This is now considered out-dated practice (Jones and Ackerman, 2016a), particularly in the instance of patients with pancreatitis for which it is considered that early enteral nutrition is an important factor alongside analgesia and fluid therapy (Droes and Tappin, 2017) (Table 1). Another GI tract condition where early enteral nutrition is recommended is parvovirus, as outlined in Table 1. Not all patients with a GI tract condition will be a candidate for early enteral nutrition, there may be good reason to delay nutrition provision, however, each patient should still receive a nutritional assessment (Freeman et al, 2011) to determine their requirements.
Benefits of early enteral nutrition
Early enteral nutrition brings many benefits however a few, clinically relevant benefits, are outlined below.
Prevention/reduction of risk of protein energy malnutrition (PEM)
Inadequate nutrition can have a multitude of consequences for the patient including the development of PEM (Ackerman, 2019); PEM is characterised by a deficit of all macro and some micro-nutrients, which can be the result of either a sudden, total starvation or a gradual problem (Morley, 2019). The severity can differ from patient to patient, but it is often the case that multiple organ systems are impaired (Morley, 2019). While is can be difficult to establish when exactly PEM has occurred, a patient that has not achieved their RER for a period of 3 days or more is classed as being at risk of developing PEM (Chan, 2009); an enteral feeding tube would be the intervention of choice. The initiation of early enteral nutrition can aid in either preventing undernourishment from progressing to PEM or reduce the severity and hasten the patient's recovery from a nutritional aspect.
Prevention of bacterial translocation
Bacterial translocation was briefly discussed in the introduction to outline basic reasoning for the importance of early enteral nutrition; the prevention of this can help to dramatically improve patient outcomes (Harris et al, 2017). Enterocytes are nourished from the passage of food through the intestinal lumen (Droes and Tappin, 2017), which evidently is not possible when the patient is being fasted or is anorexic. Intestinal motility will start to decrease without enteral nutrition, in addition to the atrophy of villi, which can lead to bacterial translocation (Droes and Tappin, 2017) and resultant sepsis. Sepsis can lead to systemic inflammatory response syndrome (van Schoor and Schoeman, 2014) and progress to multiple organ dysfunction syndrome, which has a high mortality rate (Osterbur et al, 2014), therefore intervention is needed in order to maintain homeostasis. Enterally feeding the patient a suitable diet soon after hospitalisation can reduce the likelihood of bacterial translocation occurring, thus preventing it and facilitating a quick recovery.
Decreased healing and recovery times
Anorexia was stated by Chan (2009) as a contributing factor in delayed wound healing as adequate nutrients, particularly protein, are needed for tissue growth and repair (Jones and Ackerman, 2016b). When nutrition is not adequate, negative effects can occur with essential factors for optimal wound healing, these being impaired immune function in addition to a decrease in both collagen formation and the tensile strength of the wound (Chan, 2017). Dehiscence of a surgical wounds is multifactorial (Anderson and Smith, 2011), but one contributing factor is when the general health of the patient is poor, which can be directly related to nutritional status. Not all patients will have a wound but knowing that nutrition is vital for repairing damaged cells (Jones and Ackerman, 2016b), it becomes pertinent to initiate enteral nutrition in as many hospitalised patients as possible. Addressing the nutritional needs for each patient will help to indicate when early enteral nutrition is possible (Delaney, 2006), thus avoiding the nutrition-related problems associated with delayed healing. This in turn would help to decrease overall recovery times and reduce the length of hospitalisation.
Complications of early enteral nutrition
One of the main complications that comes with early enteral nutrition is the risk of refeeding syndrome, which is caused by the rapid initiation of enteral feeding following an excessive period of anorexia (Dorricott, 2012). It can occur in patients that have rapidly lost weight, such as those with hepatic lipidosis (Brenner et al, 2011), as previously mentioned. When a patient is suddenly supplied with nutrients, an imbalance can occur with electrolytes (Dorricott, 2012); Brenner et al (2011) discussed that findings of hypophosphataemia, hypokalaemia and haemolytic anaemia were consistent with the veterinary surgeon (VS) reaching a diagnosis of refeeding syndrome. Hypophosphataemia is associated with an increased risk of acquiring infections and inadequate oxygen delivery to the tissues, amongst many others (Brenner et al, 2011). Inadequate delivery of oxygen coupled with anaemia will mean that the patient will be hypoxic, which is a derangement that can lead to the damage of many organs (Murrell and Ford-Fennah, 2011). Hypokalaemia can lead to cardiac arrhythmias (Kogika and de Morais, 2017), which would be an unwanted and potentially avoidable complication for these ill patients. While refeeding syndrome is relatively uncommon in veterinary practice when compared with human medicine (Brenner et al, 2011), it should still be a potential problem noted on the patient's NCP in relation to the nursing intervention of the enteral feeding method. It should be a main aim of the caregiver to prevent the incidence of refeeding syndrome, and one way to do this is to meet the patient's RER gradually over a few days rather than meeting the whole RER straight away (Chan, 2009; Ackerman, 2019). This would allow for assessment of the response to enteral nutrition, including assessment by the VS of the relevant blood parameters.
Conclusion
There are many indications in current veterinary practice for the use of early enteral nutrition, including those which create a physical barrier for example jaw fracture (Griggs, 2014), and those which create a physiological barrier for example anorexia (Chan, 2009). Early identification of patients in need of nutritional assistance (Freeman et al, 2011) can lead to a reduction in complications such as PEM, demonstrating a clear benefit to early enteral nutrition. Feeding patients should be done gradually in order to avoid the incidence of refeeding syndrome (Ackerman, 2019), however, when delivered appropriately, early enteral nutrition can improve patient outcomes and reduce hospital stays.
KEY POINTS
- Enteral nutrition is suitable in most patients provided there is functional gastrointestinal (GI) tract.
- A nutritional assessment should take place including measurement of the patient's weight, body condition score and muscle condition score, in addition to calculating their resting energy requirement (RER).
- Early enteral nutrition is suitable for a wide variety of hospitalised veterinary patients with some indications being facial trauma, recumbency and anorexia.
- The patient's RER should be fed gradually to avoid the serious complication of refeeding syndrome.