Many patients present for critical care with persistent vomiting and other gastrointestinal compromise including loss of appetite, inability to eat or tolerate feeding and diarrhoea, which accompany many disease processes (Chan, 2020). The gastrointestinal tract spans from the mouth through to oesophagus, stomach, small and large intestines, pancreas and liver, digesting and absorbing food (Gajanyake, 2021). Therefore, gastrointestinal complications are something registered veterinary nurses deal with on a regular basis. But this does not make these cases simple. This article discusses critical care nutrition for cases that are persistently vomiting, unable or unwilling to eat or digest food appropriately. These cases can be time consuming and, often, difficult to nurse, requiring a lot of skill and critical thinking. However, the recovery and progression of these patients can make them incredibly rewarding for the nursing team.
Aetiology
Critically ill patients are at an increased risk of gastrointestinal compromise, including those where gastrointestinal compromise is not their primary condition. Gastrointestinal compromise can be caused by inflammation, either primary (eg surgical trauma, infection) or secondary to other disease processes (Gajanyake, 2021).
Many conditions can result in secondary gastrointestinal compromise as a result of inflammation, including pancreatitis, multi-trauma, systemic and multisystemic conditions, immune-mediated disease and surgery (Gajanyake, 2021). Inflammation is a response of the immune system, and triggers include damaged cells and pathogens. In the acute stages, this functions to restore health (Chan, 2020). Inflammatory mediators dilate blood vessels to increase blood flow, remove damaged cells and pathogens, and assist in healing (Kirkness, 2021). Complications arise when inflammation is inappropriate, extreme or chronic, resulting in systemic damage to healthy organs and tissue, such as those of the gastrointestinal tract. Persistent inflammation results in mucosal damage, and actual or perceived pathogens are not cleared from the GI tract, resulting in a more aggressive response and continued inflammation (Rooney, 2017; Gajanyake, 2021). Pathogens which are not successfully cleared from the gastrointestinal tract can also remain in the tissue, causing persistent inflammation.
Presentation
Signs of gastrointestinal compromise in critical care patients depend on the patient's condition, comorbidities and area of gastrointestinal tract affected. Signs include:
Vomiting
Vomiting can be mechanical or functional, preceded by nausea (eg food aversion, belching and gulping), and involves active expulsion of gastrointestinal contents from the stomach and duodenum, through abdominal heaving (Bacon, 2019). Vomiting can produce variably digested material depending on the duration in the stomach or further down the gastrointestinal tract (Polton and Branscombe, 2008). The qualities of vomitus material provides an indication of the type of gastrointestinal compromise (eg brown matter from the lower gastrointestinal tract).
Regurgitation
Regurgitation can be characterised by the involuntary, nonactive, expulsion of gastrointestinal contents, often occurring without pre-emptive signs (Polton and Branscome, 2008). The material produced can indicate gastrointestinal tract health. For example, the production of undigested food 12 hours after consumption indicates severe delay in gastric emptying, and therefore gastric motility issues, while projectile expulsion can indicate obstruction. Gastro-oesophageal reflux, also known as silent regurgitation, is the passive passage of the gastrointestinal contents into the oesophagus which is often undetected (del Barrio, 2023). Recumbent patients should have their heads elevated to reduce the risk of silent regurgitation and subsequent aspiration pneumonia (Devey, 2021). Signs of regurgitation can include gulping, frequent swallowing and lip smacking (Devey, 2021).
Oesophagitis
Oesophagitis is the irritation and inflammation of the esophagus as a result of contact with products of the stomach (Polton and Brascombe, 2008). Patients known to reflux, regurgitate or vomit can develop oesophagitis due to acidic fluid from the stomach (Woolfe, 2014). This can be shown through repeated swallowing, discomfort, stress, reluctance to eat and depression. Oesophagitis can also be associated with motility issues, sphincter compromise, abdominal distension, and brachycephalic conformation (Woolfe, 2014; Watkins, 2022). Further to this, patients that are starved or anorexic have an increased acidity of stomach contents, therefore increasing their risk of oesophagitis (Gerrard, 2023).
Diarrhoea
There are different forms of diarrhoea, based on the type and location of gastrointestinal compromise. Diarrhoea associated with the large intestines is usually produced in high frequency but small volumes, with an urgency to pass, blood and straining. Diarrhoea associated with small intestinal issues is often produced in large volumes of liquid (Polton and Brascombe, 2008).
Ileus
Ileus is the reduction or cessation in motility of the gastrointestinal tract (Woolfe, 2014). Mechanical ileus refers to that caused by an obstruction, such as a mass or foreign body. Functional ileus refers to the lack of regular peristaltic movement of the gastrointestinal tract (Madl and Druml, 2003). Ileus can result from inflammation causing suppression of gastrointestinal mixing and propulsion, causing reduced gut motility. Functional ileus may also occur with premature motility, causing gastrointestinal contents to rapidly sweep through, and the contents of the faeces in these cases may be partially digested. Motility changes can be associated with weight change, abdominal distension, muscle loss and regurgitation. Delayed gastric emptying and ileus may be seen secondary to abdominal surgery as well as with inflammatory diseases (eg pancreatitis and gastroenteritis), dehydration and opioid use (Kehlet and Holte, 2001; Madl and Druml, 2003).
Pain
Pain and discomfort are common symptoms of gastrointestinal compromise and can perpetuate the continuation or worsening of disease processes and symptoms including hyporexia and anorexia (Woods-Lee, 2022). Stress from illness, pain, the environment and trauma causes cytokine and hormone release, which can affect neurotransmission within the nervous system, responsible for secretion control and muscles for digestion, with the parasympathetic nervous system controlling life sustaining processes such as digestion (Tindle and Tadi, 2022).
Treatment
Treatment for those with gastrointestinal compromise and associated inflammation depends on the primary and secondary disease processes; however, some common treatment options are discussed.
Immunosuppressive medication can be used to blunt the body's immune response, therefore reducing the perpetuation of inflammation. However, this can delay healing and recovery from infection, as well as promoting vomiting, diarrhoea and gastrointestinal ulceration, as is noted with steroid administration (Allerton, 2023). Appetite stimulants can be used; however, this does not work for anorexic patients, only those with reduced appetite. Antibiotics may reduce the bacterial load, however this has a negative effect on the microbiome as well as increasing permeability and therefore bacterial translocation risk increases (Gajanyake, 2021). Gastric or oesophageal protectants may be used to prevent further ulcerative erosion by reducing contact with acids and bile salts. Gastric stimulants can be used for those with reduced gut motility to increase oesophageal and gastric contractions and relax the pyloric sphincter. Faecal transplants can be used by giving a suspension of a healthy faecal sample via nasogastric (NG) tube, colonoscopy, gastroduodenoscopy or enema to establish a healthy bacterial microbiota (Ridgway, 2020). Normal gut microbial populations are sustained by enteric nutrients (Ridgway, 2020) and they protect the internal environment to maintain normal function, digestion, immune stimulation and protection. Dysbiosis, the microbial shift, can be caused by gastrointestinal conditions, including intestinal motility, nutrition and gastrointestinal secretions. Symptomatic treatment can include fluids and electrolyte supplementation to correct disturbances and analgesia, however opioid analgesia may also contribute to ileus (Gajanyake, 2021).
Nutritional nursing care
Malnutrition occurs due to a lack of nutrients and calories provided for the patients’ survival. Critical patients are at increased risk of malnourishment, with risk factors including malabsorption, anorexia, underlying disease and pain (Chan, 2020), all of which are common in critical patients. Factors which predispose patients to malnutrition include serious underlying disease (eg trauma, sepsis, peritonitis, pancreatitis, gastrointestinal surgery) and large protein losses (eg vomiting, diarrhoea and draining wounds) (Chan, 2020). Sick or traumatised patients will catabolise lean muscle rather than fat when they are not provided with sufficient calories. This loss of lean tissue reduces strength, wound healing, and causes compromised immune function resulting in enteric dysbiosis, infectious diseases or worsening of existing infectious processes (Ridgway, 2020; Woods-Lee, 2022) and likely negatively impacts overall survival (Chan, 2020). Signs of malnourishment include weakness, muscle loss and 10% weight loss, which can be masked by fluid shifts and stabilisation attempts (Chan, 2020). These patients are also at risk of stress starvation. When nutrient requirements are not met, the healthy body slows metabolism. However, during stress and illness, cytokine release increases the metabolic rate, increasing fat and muscle breakdown, causing rapid malnutrition and cellular failure.
The gut wall consists of a semi-permeable, protective barrier, which allows nutrient uptake while restricting pathogens and bacteria. The epithelial cells are packed tightly and maintained by a mucosal barrier coating to restrict acute stress on cells. These secretions bind to bacteria, deactivating and clearing them, assisting in immune responses. These intestinal epithelial cells derive their nutrition directly from the gut's luminal contents (Bacon, 2019). Lack of enteral nutrition can lead to changes in the gastrointestinal mucosal integrity which then destabilizes the gastrointestinal barrier and results in atrophy of the intestinal epithelia (Bacon, 2019). Those not fed or those provided total parenteral nutrition have a resultant breakdown and inflammation of the tight epithelial cell barrier due a lack of nutrition. Chronic inflammation can then self-perpetuate, as losing the protective mucosal barrier allows more pathogens into the mucosa, resulting in more inflammation. This also opens entry points for bacteria to leave the gut and enter the circulation, resulting in systemic infection and bacterial translocation and a further inflammatory response (Bacon, 2019). This disruption in permeability also causes a loss of fluid, protein, electrolytes and, in some cases, red blood cells. This is not limited to long-term critical patients. In the short-term patient malnutrition should be avoided, as alterations can be observed after just 1–4 days of hyporexia or anorexia as a result of insufficient energy and nutrients (Woods-Lee, 2022). Development and early implementation of an appropriate nutrition plan can be associated with improved outcomes and shorter hospitalisation times.
Nutritional assessments should be made regularly in these patients. This can be done by weighing every 6–12 hours, daily body condition score and muscle condition score and calculations of resting energy requirement. These should all be compared to the patient's current body weight and score and their ideal/pre-illness scores. Nutritional assessment should use both visual and tactile assessments (Chan, 2020). Continual decline in body weight or condition should prompt reassessment and modification of the nutritional plan, for example to increase the calories provided by 25% (Chan, 2020). Important monitoring for those receiving enteral nutrition includes body weight, serum electrolyte concentrations, tube patency, appearance of tube exit site and gastrointestinal signs (Chan, 2020).
Where possible, the gastrointestinal tract should be used for nutrient and energy absorption (Woods-Lee, 2022). Enteral nutrition helps to maintain intestinal structure and function (Chan, 2020). The route of enteral nutrition depends on the patient's stability for anaesthesia or sedation and their condition. Nasogastric tubes are often the safest and most appropriate option in the short term for small volume liquid feeds, and can stay in place for 3–10 days (Woods-Lee, 2022). However, nasogastric tubes are not always appropriate for connecting to a constant rate infusion of food and boluses of food can result in nausea and vomiting (Chan, 2020). Force or syringe feeding should be avoided (Woods-Lee, 2022). Care should always be taken in deciding whether a patient should be syringe fed because of the association with aspiration pneumonia and food aversion. Dyspnoeic patients, those with compromised ability to protect their airways (eg as a result of head trauma or nerve damage) or brachycephalic conformation should never be syringe fed (Chan, 2020).
For patients unable to tolerate nutrition to cover their resting energy requirement, such as those that regurgitate or vomit consistently, minimal luminal (trophic) feeding should be initiated (Bacon, 2019). Luminal feeding provides enterocytes with glucose and electrolytes for survival (Gajanyake, 2021), not the patient's metabolic requirements (Bacon, 2019). Small amounts are used for these patients as this avoids any abdominal distension and reduces the risk of initiating vomiting. Luminal feeding has also been associated with a compensatory hyperplasia of the intestinal cells. The feed contains glucose, water and electrolytes which are easily absorbed (Bacon, 2019), an important factor for the inflamed gastrointestinal tracts which have low absorption rates. An example ‘recipe’ option is a 5% glucose solution of lactated ringers. This solution helps the intestinal lumen to absorb potassium; however, if the patient is hypokalaemic then the solution may have 20 mmol of potassium per litre added.
1 L lactated ringers ( Number 11 ) made to 5 % glucose solution + 20 mmol potassium
The nutrition plan should be reassessed and discussed by the team frequently and appropriate adjustments made as per the example stages below. The volumes and type of feeding should be adjusted slowly, every 12–24 hours dependent on the patient's progress.
- Stage 1) 0.1–0.2 ml/kg/hour glucose solution
- Stage 2) 1–2 ml/kg/hour glucose solution
- Stage 3) 1–2 ml/kg/hour of an oral rehydration liquid
- Stage 4) 1–2 ml/kg/hour of energy dense recovery liquid food. At this stage, check the amount given against the patient's resting energy requirement and do not exceed 25% of the patient's resting energy requirement at this stage.
Example: 10 kg dog
- Stage 1) 1–2 ml per hour if given on a constant rate infusion or 2–4 ml given as bolus every 2 hours
- Stage 2) 10–2 0ml per hour constant rate infusion or 20–40 ml bolus every 2 hours – glucose solution
- Stage 3) 10–20 ml per hour constant rate infusion or 20–40 ml bolus every 2 hours – rehydration liquid
- Stage 4) 10–20 ml per hour constant rate infusion or 20–40 ml bolus every 2 hours – recovery liquid
These volumes can be given as boluses every 2–4 hours or as a constant rate infusion, depending on what the patient tolerates and the type of feeding tube being used. If at any time the patient vomits, they should be returned to the previously tolerated volume. Once these four stages are tolerated, the patient may have a staged transition to their full resting energy requirement over 3–4 days (eg day 1 – 25%, day 2 – 50%, day 3 – 75%, day 4 – 100%) (Chan, 2020; Woods-Lee, 2022).
Resting energy requirement = body weight × 30 + 70
Example: 10 kg dog fed liquid food at 1 kcal/ml
25%: 15 ml given 6 times daily
50%: 30 ml given 6 times daily
75%: 45 ml given 6 times daily
100%: 61 ml given 6 times daily
The food should continue to be provided in small frequent meals until the patient's gastrointestinal signs are well controlled. Although healthy patients are able to tolerate 10–20 ml/kg/feed, patients experiencing gastrointestinal compromise should not exceed 5–10 ml/kg per feed initially. Maintaining a single position reduces the risk of regurgitation, as time is allowed for food to enter the stomach (Tappin, 2016), this also avoids excess pressure being placed on the potentially distended or painful abdomen.
Feeding in this way minimises metabolic derangements and catabolism, protecting gut integrity. Further to this, feeding helps gut motility, downregulates inflammatory responses and has an antiemetic and prokinetic effect. Ideally anything given to the patient should be warmed to assist with gastric emptying, further avoiding gastric distension. Postural feeding may be helpful for those with gastro-oesophageal reflux. To be beneficial the food should be provided at a level of at least 45 degrees higher than the oesophageal sphincter and maintained for 20–30 minutes (Ridgway, 2020). This can also be done for tube feeding recumbent patients by placing them on a mattress angled in such a way that the head is above the stomach and oesophageal sphincter.
Once the patient is able or willing to eat they may be transitioned to a complete oral diet. The decision on diet type should be considered on a case-by-case basis and may be influenced by the cause of the gastrointestinal inflammation. Therapeutic diets can reduce signs of disease and promote recovery from illness (Woods-Lee, 2022). For diet-induced inflammatory responses, these patients may benefit from antigen limiting diets to reduce antigen exposure and therefore reduce the negative response from the body. Diets of this type include hydrolysed diets, where the protein is reduced to a low molecular component and therefore not recognised by the body, this is often seen as the preferred low antigen diet (Gajanyake, 2021). Another option is to use a carefully selected, novel, single protein source diet. For those that do not require ongoing dietary modification, gastrointestinal diets, which are fat restricted (as fat malabsorption worsens diarrhoea), highly digestible and with low fibre (as fibre reduces digestibility) can be used in the short term (Gajanyake, 2021). High digestibility is important for ease of digestion and lower residue resulting in a lower faecal output (Woods-Lee, 2022). Raw food diets should not be given to these patients due to the faecal shedding of harmful bacteria, systemic infections from pathogens and the risk of bacterial translocation in these patients due to intestinal epithelial fragility (O'Dwyer, 2017; Gajanyake, 2021).
Care should be taken if attempting to use these diets for tube feeding by blending, as this often required the addition of water, which increases the volume of food delivered and decreases the calorie density (Woods-Lee, 2022). This may be contraindicated in the presence of delayed gastric emptying as this may cause distension and vomiting (Woods-Lee, 2022). If there is not another option available then consider using a constant rate infusion to deliver the patient's required food volume.
Conclusions
Nutrition has the potential to impact the outcome of treatment significantly (Woods-Lee, 2022) and earlier feeding is associated with faster recovery, improved gut function and shorter hospitalisation periods (Gajanyake, 2021). The goal of nutritional support for the critically ill patient is to prevent further losses to lean tissue and provide energy and nutrients required for healing (Chan, 2020), and this can be a gradual and staged process. Veterinary professionals need to provide excellent nutrition for these patients, including when they cannot or will not consume food voluntarily; however, it has been found that the majority of hospitalised patients have energy deficits (Woods-Lee, 2022). As veterinary nurses, being equipped with the knowledge to create an appropriate nutritional plan for these patients has a huge impact.
KEY POINTS
- Veterinary nurses require the ability to identify which patients require adjusted nutritional support.
- It is important to identify patients at risk of malnutrition and the associated complications.
- Veterinary nurses need to understand luminal feeding and how to apply this to a case.
- There is a need to create and assess for nutritional plans.