daniel l. chan nutritinal supprt fr …...3 nutritional support is now considered an essential part...

NUTRITIONAL SUPPORT FOR CRITICALLY ILL PATIENTS

DANIEL L. CHAN

16VET-ICU SCIENTIFIC GUIDE A4.indd 1 26/07/2016 16:31:16

Introduction ..........................................................................................3

Importance of Nutritional Support ......................................................4

Pathophysiology of Malnutrition ..........................................................6

Nutritional Assessment .......................................................................8

When to initiate feeding.....................................................................11

Choosing the most appropriate feeding tube ...................................12

Placement of feeding tubes ..............................................................14

Meeting Nutritional Needs and Special Considerations .................18

Nutritional Plan .................................................................................19

Implementing Nutritional Plan .........................................................20

Monitoring and Reassessment .........................................................21

Complications ....................................................................................22

Conclusions .......................................................................................23

Index


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Nutritional support is now considered

an essential part of managing critically

ill patients, especially if they are

malnourished. There are a number of

reasons for critically ill animals to be at

high risk for becoming malnourished.

Moreover, critically ill animals undergo

several metabolic alterations that further

increase this risk for malnutrition. The risk

of malnutrition in this patient population

relates to inadequate food intake because it

is not uncommon for inappetence to be one

of the main clinical problems in animals requiring medical care. Animals are frequently presented to

veterinarians for loss of appetite, an inability to tolerate feedings, and persistent vomiting, or diarrhoea

that accompanies many disease processes. Because malnutrition can occur quickly in these animals,

it is vital that we identify animals at risk for malnutrition, and initiate early nutritional support for these

patients. The goals of nutritional support are to treat malnutrition when present and, just as important,

to prevent malnutrition from developing in patients at risk.

Whenever possible, the enteral route should be used because it is the safest, most convenient, and most

physiologically sound method of nutritional support.

Ensuring the successful nutritional management

of critically ill patients involves selecting the

right patient, making an appropriate nutritional

assessment, and implementing a feasible and

effective nutritional plan. This clinical review aims

to clarify the consequence of inadequate nutritional

intake and provide guidance for initiating effective

nutritional supportive measures. By improving

the way we support patients with nutrition, we

can ensure they have the best chance for making

successful recoveries.

Introduction

ABOUT THE EDITOR:

Daniel L. Chan is Professor of Emergency and Critical Care and Clinical Nutrition at the Royal Veterinary College, University of London, UK where he is the Head of the Section for Emergency and Critical Care and of the Nuritional Support Service. He is a Diplomate of the American and European Colleges of Veterinary Emergency and Critical Care and of the American College of Veterinary Nutrition.

The enteral route should be used because it is the safest, most convenient,

and most physiologically sound method of nutritional

support.

The goals of nutritional support are to treat

malnutrition when present and, just as important, to prevent malnutrition from

developing in patients at risk.

Hawkshead Lane North Mymms, HERTS

United Kingdom AL97TA

DANIEL L. CHAN

Daniel L. Chan, DVM, DACVECC, DECVECC, DACVN, FHEA, MRCVS


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Many of the challenges encountered when ma-naging critically ill patients relate to the presence of organ dysfunction (e.g., ileus, diarrhoea, azo-taemia), clinical signs suggestive of gastrointes-tinal intolerance (e.g., regurgitation, vomiting), metabolic complications (e.g., hyperglycaemia, hypokalaemia, accelerated lean muscle loss) and the presence of co-morbidities (e.g., anaemia, chronic kidney disease, aspiration pneumonia) all of which can be bar-riers for effective feeding. Moreover, the lack of proper nutrition will only worsen the nutritional and metabolic state of these patients, making it more difficult to recover. For example, protracted lack of food intake will negatively impact their ni-trogen balance (Figure 1) and accelerate the cata-

bolic state, which is not easily reversed even when feeding is re-instituted. Lack of enteral nutrition will contribute to abnormal gastrointestinal function such as ileus, and loss of mucosal barrier function. Lack of proper nutrition also compromises the ability by the body to synthesize important substances such as albumin, which in turn affects drug pharmacokinetics. For these reasons, the importance of proper nutrition

cannot be underesti-mated. There is now mounting evidence that with early nutritional support, animals can have improved outco-mes. Therefore it is vital that clinicians mana-ging critically ill patients explore ways of initiating early nutritional support whenever possible.

Importance of Nutritional Support

The lack of proper nutrition will only worsen

the nutritional and metabolic state of

critically ill patients, making it more difficult

for them to recover.

Hospitalization is often a cause of anorexia.

Hospitalized cats are particularly sensitive to stress and can develop an aversion to the food they are given during their stay in intensive care.


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GluconeogenesisUrogenesis

Acute-phase protein synthesis

Loss of the skeletal muscle mass (lysis

of muscle cells to draw amino acids)

HEALTHY PET & FOOD INTAKE SICK PET & FOOD DEPRIVATION

Amino acid intake from the diet

No / Low amino acid intake from the diet

Inflammation processes.Defence against sepsis, shock…

Maintenance/gain of muscle mass

Base metabolismMaintenance

Hormone synthesisEnergy production

Nitrogen balance in a critical animal and in a healthy animal.

FIGURE 1

amino acidFROM DIET

amino acidFROM MUSCLE

POSITIVE NITROGEN BALANCE

NEGATIVE NITROGEN BALANCE


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One of the major metabolic alterations asso-ciated with critical illness involves body protein catabolism, in which protein turnover rates may become markedly increased. Whereas healthy animals primarily lose fat when temporarily de-prived of sufficient calories (i.e., ‘simple starva-tion’) as may be encountered by fasting animals before surgery, sick or traumatised patients catabolise lean body mass when they are not provided with sufficient calories (i.e., ‘stressed starvation’). During the initial stages of fasting in the healthy state, glycogen stores are used as the primary source of energy. Following deple-tion of glycogen stores, a metabolic shift occurs towards the preferential use of store fat depots, sparing catabolic effects on lean muscle tissue.

However, during diseased or stressed states, the inflammatory response triggers alterations in metabolism towards a catabolic state. Gly-cogen stores are quickly depleted, especially in strict carnivores such as the cat, and this leads to an early mobilisation of amino acids from muscle stores. As cats undergo continuous gluconeogenesis, the mobilisation of amino acids from muscles is more pronounced than that observed in other species. With continued lack of food intake, the predominant energy source is derived from accelerated proteolysis (muscle breakdown), which in itself is an en-ergy-consuming process. Muscle catabolism that occurs during stress provides the liver with gluconeogenic precursors and other amino

acids for glucose and acute-phase protein production. The resultant negative nitrogen ba-lance or net protein loss has been documented in critically ill dogs and cats. (See Figure 1).

One study estimated that 73% of hospitalised dogs (including post-operative patients) evaluated in four different veterinary referral centres were in a negative energy balance.

More recent studies re-port that in intensive care unit environments, which treat patients at the highest risk of de-veloping malnutrition, up to 66% of patients don’t receive adequate nutritional support.

The consequences of continued lean body mass losses include negative effects on

wound healing, immune function, strength (both skeletal and respiratory muscle strength), and ultimately on overall prognosis (See Table 1). In the context of post-operative patients, this could lead to greater risk of surgical wound dehiscence and post-operative infections.

Pathophysiology of Malnutrition

73% of hospitalised dogs in negative energy

balance.

Up to 66% of patients don’t receive adequate

nutritional support.


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Lack of energy Weakness, Recumbency

Accelerated lean body mass loss Catabolic state

Decreased tissue healing Increased risk of surgical wound dehiscence

Decreased albumin synthesisHypoalbuminaemia, Compromised drug-carrying capacity

Compromised immune function Increased risk of nosocomial infections

Lack of enteral nutritionGastroinstestinal dysmotility, Increased enterocyte turnover, Compromised gut barrier function

CONSEQUENCES OF MALNUTRITION IN CRITICALLY ILL PATIENTS

TABLE 1

Due to the metabolic alterations associated with critical illness, and in part due to an inability or reluctance of many critically ill and post-operative dogs and cats to eat sufficient calories, this patient population is at increased risk for developing complications related to their malnourished state. Given the serious se-quelae of malnutrition, preservation or reversal of deteriorating nutritional status via nutritional support is paramount. Nutritional support is therefore aimed at minimising the impact of malnutrition and enhancing rate of recovery.

In dogs, a period as short as 3 days of anorexia has been documented to produce metabolic changes consistent with those seen associated with starvation in people. However, these dogs would not necessarily

exhibit any easily detectable abnormalities on clinical assessment suggestive of being mal-nourished. Dogs with overt signs suggestive of malnutrition (e.g., severe muscle wasting, poor coat quality) usually have a more protracted period (usually weeks to months) of disease progression. In cats detectable impairment of immune function can be demonstrated in healthy cats subjected to acute starvation by day 4, and so recommendations to institute some form of nutritional support in any ill cat with inadequate food intake for more than 3 days have been made. In both dogs and cats, there

is some consensus that there is an urgent need to implement a nutritional intervention (e.g., place feeding tube) when a dog or cat has not eaten for more than 5 days.

3 days of anorexia are enough to produce severe

metabolic changes and immune malfunction.


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The successful management of critically ill patients may involve the selection of patients most likely to benefit from nutritional support and the selection of the most appropriate route for providing nutrition. The technique for performing nutritional assessment was designed to utilize readily available historical and physical parameters to identify malnou-rished patients who are at increased risk for complications and who will presumably benefit from nutritional intervention. The assess-ment involves determining whether nutrient assimilation has been restricted because of decreased food intake, maldigestion or malab-sorption, whether any effects of malnutrition on organ function and body composition are evident, and whether the patient’s disease process influences its nutrient requirements. The findings of the historical and physical assessment are used to categorize the patient as well nourished, moderately malnourished or at risk of becoming malnourished or severely malnourished. Checklists have been proposed to allow assessment of a patients need for instituting nutritional support based on certain risk factors and a modified checklist is found in Table 2.

A patient with 2 or more high-risk factors pre-sent should receive nutritional support as soon as they are stabilised. Patients with fewer than 2 high risk factors should be closely monitored and re-assessed every few days.

Nutritional Assessment

Blood analysis helps to better evaluate the hospitalised

animal’s nutritional status.

Obesity is a form of malnutrition often responsible for complications in the event of intensive care.


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The patient history should be assessed for indications of malnutrition including evidence of weight loss and the time frame in which it has occurred, there should be a determination of the adequacy of dietary intake including the nutritional adequacy of the diet, the presence of persistent gastrointestinal signs, the patient’s functional capacity (e.g., evidence of weakness, exercise intolerance) and the metabolic demands of the patient’s underlying disease state. The physical exam should focus on changes in body composition, presence of edema or ascites, and appearance of the patient’s hair coat. With regard

to assessing changes in body composition, it is important to recognize that while metabolically stressed patients experience catabolism of lean tissue, these changes may not be noted using standard body condition scoring systems if the patient has normal or excessive body fat. Since catabolism of lean tissue can have deleterious consequences for outcome, it is important that along with evaluation of body fat, patients undergo evaluation of muscle mass to assess lean tissue status. A muscle mass scoring system that has been used in dogs and cats is outlined in Table 3.

Modified from Perea, SC. Parenteral Nutrition. In: Fascetti AJ, Delaney SJ (eds) Applied Veterinary Clinical Nutrition. Wiley Blackwell, Chichester, West Sussex, 2012, first edition; page 355

A patient with 2 or more high-risk factors present should receive nutritional support as soon as they are stabilised. Patients with few than 2 high risk factors should be closely monitored and re-assessed every few days.

TABLE 2 : ASSESSMENT OF NEED FOR NUTRITIONAL SUPPORT

PARAMETER LOW RISK MODERATE RISK HIGH RISK

Food intake < 80% RER for < 3 days

Food intake < 80% RER for 3-5 days

Food intake < 80% RER for > 5 days

Anorexia ≥ 3 days

Presence of Weight Loss

Severe Vomiting/Diarrhoea

Body condition score < 4/9

Muscle Mass Score ≤ 2

Hypoalbuminaemia

Expected Course of illness < 3 days

Expected Course of illness 2-3 days

Expected Course of illness > 3 days


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Description of a Muscle Mass Scoring System for Dogs and Cats.

Muscle Condition Score charts for dogs and cats can be downloaded from the WSAVA website:

www.wsava.org/nutrition-toolkit

TABLE 3

SCORE MUSCLE MASS

0 On palpation over the spine, muscle mass is severely wasted

1 On palpation over the spine, mass is moderately wasted

2 On palpation over the spine, muscle mass is mildly wasted

3 On palpation over the spine, muscle mass is normal

The next step of nutritional assess-ment is to determine whether or not the patient’s voluntary food intake is suffi-cient. To do this one must have a caloric goal in mind, select an appropriate food, and formulate a feeding plan for the patient. This will permit an accurate accounting of how much food is offered to the patient and will allow evaluation of the patient’s intake based on how much of the food is consumed.Providing nutrition via a functional digestive system is the preferred route of feeding, and so particular care should be taken to evaluate whether the patient can tolerate enteral feedings. Even if the patient can tolerate only small amounts of enteral nutrition, this route of feeding should be pursued. Supplementation with parenteral nutrition should only be pur-sued when the use of enteral nutrition cannot meet at least 50% the patient’s nutritional needs (i.e., 50% of the patient’s resting energy requirement). On the basis of the nutritional

assessment, the anticipated dura-tion of nutritional support, and the

appropriate route of delivery (i.e., enteral or parenteral), a nutritional plan is formulated to meet the patient’s nutritional needs.

It is worth noting that before instituting the nutritional plan, patients should have hydration status, electrolyte and acid-base disturbances addressed and patients should be haemody-namic stable. Commencing nutritional support before these abnormalities are addressed can increase the risk of complications and, in some cases, can further compromise the patient. It should be emphasized that this is not counter to the concept of “early nutritional support,” which has been documented to result in positive effects in several animal and human studies. Early nutritional support advocates feeding as soon as possible after haemodynamic stability is achieved, rather than delaying nutritional intervention by several days.


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As alluded to earlier, for many years conventio-nal therapy actually ignored nutritional needs of critically ill patients. As more and more evidence illustrates the consequences of malnutrition there has been a gradual change to ensure that all patients receive adequate nutrition. Typical delays in starting nutrition decreased from weeks to 10 days, and now the debate has shif-ted to how many hours from admission should nutrition be delayed. As more and more research has unco-vered the benefits of enteral nutrition and the complications arising from gut atrophy, critical case specialists have be-gun feeding patients earlier in the course of hospitalisation with good results.In veterinary medicine a similar transition oc-curred as well, probably only in the past 15 years. From the ineffective strategies such as force- or syringe-feeding, warming foods, adding flavour enhancers, to more recent recommendations for early tube feeding in most if not all critically ill patients. While most can agree that nutritional support is important, and that early intervention

is better that delayed, the question remains, how early to intervene? Is it days or hours? The most aggressive approach is to place a feeding tube as soon as possible and start feedings within hours. Is this necessary? Studies in canine patients with parvoviral enteritis, haemorrhagic gastroenteri-tis and acute pancreatitis support the premise that early nutritional intervention is at least well tolerated and produces little complications.

The lack of any se-rious consequence to initiating feeding early in these patient populations dispel the myth that feeding early is fraught with complications. The overall effect of early nutrition on survival is

beyond these small trials, unfortunately. Commencing feeding after tube placement should really be held until at least the animal has recovered from anaesthesia. Recumbent animals receiving feeds are at risk of aspiration. Patients with compromised gastrointestinal motility (e.g., anaesthetised patients, patients on opioids analgesics, patients with ileus) are also at risk for complications and should be monitored closely.

When to initiate feeding

Critical care specialists have begun feeding patients

earlier and earlier in the course of hospitalisation

with good results.

Assisted feeding with a syringe is sometimes sufficient for small animals but the process quickly becomes ineffective and associated with higher risks of complications.


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Choosing the most appropriate feeding tube

Determining of the route of nutritional support is an important step in the nutritional mana-gement of critical care patients. Routes of nutritional support are broadly categorized into enteral and parenteral routes. Enteral routes include nasoesophageal, na-sogastric, oesophageal, gastric and jejunal feeding tubes, while parenteral routes in-clude peripheral and central venous catheters. In most veterinary practices, na-soesophageal, nasogastric and oesophagostomy fee-ding tubes should be the most commonly considered feeding routes. The route selec-ted for each patient will be ultima-tely influenced by the patient’s medical and nutritional status, the anticipated length of required nutritional support, and consideration of the advantages and disadvantages presented by each route. Table 4 summarizes the major advantages and disadvantages associated with each feeding tube.

Nasoesophageal and nasogastric feeding are relatively easy and convenient methods of nutri-tional delivery for patients who will require short-term (fewer than 5 days) nutritional support, or for patients who are not candidates for general anaesthesia. The distinction between these techniques is whether the tip of the feeding tube remains within the oesophagus or whether they should be placed in to stomach. Concerns regar-ding possible interference of feeding tubes of the lower oesophageal sphincter led to recommen-dations that feeding tube should terminate into the distal oesophagus. However, a recent study found no difference in complication rates between nasoesophageal and nasogastric tube, the importance of where these tubes terminate

is unclear. The one advantage afforded by nasogastric tubes is that these provide access for aspirating gastric residual volumes.

In general, nasoesophageal and naso-gastric feeding tubes provide the ad-

vantages of being relatively easy to place and being inexpensive.

However, because of the risk of aspiration, nasoesopha-geal/nasogastric feeding should not be implemented in patients with protracted vomiting or those that lack

of a gag reflex. Nasogastric tubes in cats are typically

3.5 – 5 French in diameter and in dogs they may go up to 8

French. For such tubes, liquid en-teral diets work best as they do not tend

to obstruct these tubes. Liquid formulations may be delivered via continuous or intermittent bolus feedings. Although continuous feeding can be helpful in pets in which high feeding volumes may not be tolerated, a recent study demonstrated that gastric residual volumes and clinical outcome did not differ between the two feeding methods.

Placement of an oesophagostomy feeding tube requires general anaesthesia for placement, but is still a relatively quick and simple procedure. Compared to nasoesophageal/nasogastric feeding tubes, oesophagostomy tubes can be used for an extended period of time with some reported over a year of use. Other advantages include increased comfort for the animal, and an increased tube diameter (12-14 French), allowing for a wider selection of diets that may be fed through the tube.


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Advantage and Disadvantages of various feeding tube options.

TABLE 4

FEEDING TUBE DURATION ADVANTAGES DISADVANTAGES

Nasoesophageal/ Nasogastric tubes

Short term (<5 days)

Inexpensive.Easy to place.No general anaesthesia required.

Requires a completely liquid diet, limiting choice.Some animals will not eat with these tubes in place.

Œsophagostomy tubes Long term

Inexpensive.Easy to place.Can use calorically dense diets.

Requires general anaesthesia for placement.Cellulitis and infection can develop at the stoma site.

Gastrotomy tubes placed by laparotomy

Long termCan use calorically dense diets.

Requires general anaesthesia and laparotomy.Peritonitis can occur if tube is prematurely removed.

Percutaneous endoscopically guided (PEG) surgically placed gastrotomy tubes

Long termCan use calorically dense diets.

Requires endoscope.Requires general anaesthesia.Peritonitis can occur if tube is prematurely removed.

Jejunostomy tubes Long term

Bypasses upper gastrointestinal tract.Can be used in patients with protracted vomiting.

Requires general anaesthesia and laparotomy.For all in-hospital use.Requires continuous rate infusion.Requires completely liquid diet.Peritonitis can occur if tube is prematurely removed.


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NASOOESOPHAGEALNASOGASTRIC FEEDING TUBES

Placement of feeding tubes

Nasoesophageal and nasogastric feeding tubes are placed into the distal esophagus or directly into the stomach via the nares. This can be a very useful feeding technique in clinical cases where a relatively short-term nutritional intervention (e.g., for about 3 to 5 days) is required. This type of feeding tube does not require any specialized equipment or expertise for placement and thus can be a very useful tool in general practice. In addition, these feeding tubes can be placed without the need for general anesthesia (or heavy sedation) and as such, they can be act as a temporary intervention in patients where anesthesia may be contraindicated. 1 Nasal Cavity

2 Oesophagus 3 Larynx 4 Trachea

1

2

3

4

This modality of nutritional support entails a relatively easy placement technique that is minimally invasive and well tolerated. Placement of the feeding tube into the midcervical region mitigates complications associated with pharyngostomy tubes including gagging and partial airway obstruction. Oesophagostomy tubes can provide at-home nutritional support for weeks to months for patients unable or unwilling to eat to meet nutritional needs orally. The larger diameter of this tube compared to nasoesophageal or jejunostomy tubes allows for a wider selection of diet options including blenderized prescription formulated for specific medical conditions (e.g., novel protein diets, fat-restricted diets). The technique preferred by the author is demonstrated in photos 5-15 and detailed p16-17.

OESOPHAGOSTOMY TUBES

1 Larynx 2 Trachea 3 Oesophagus 4 Oesophageal tube

4

3

21


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PLACEMENT TECHNIQUE FORNASOESOPHAGEAL (NASOGASTRIC) TUBES

Placing a feeding tube into the nares of a cat.

Position the conscious or sedated patient in sternal recumbency.

Apply 1-2 drops of local anaesthetic (e.g., proxymetacaine) into one nostril with the head held up so that the anaesthetic agent flows caudally into the nasal cavity.

While waiting for the local anaesthetic take effect (usually 1 or 2 minutes), measure the tube from the nares to the 7th or 8th intercostal space for nasooesphageal placement or to behind the ribs for nasogastric placement- mark this position on the tube with some adhesive tape or permanent marker.

Lubricate the tube with gel.

Hold the head at a normal angle and direct the tube ventrally and medially (i.e., toward the opposite ear) for passage into the ventral nasal meatus ; in dogs it may be necessary to pass the tube dorsally initially (for about 1 cm) over the ventral ridge and then in a ventral and medial direction whilst holding the external nares in a dorsal position.

The tube should pass without resistance and the patient may swallow as the tube passes the oropharynx.

If resistance is met the tube should be withdrawn and steps 4 - 6 should be repeated.

Once the tube has been passed to the level of the tape marker it should be secured as closely as possible to the nostril using a single suture to the skin encompassing the tube.

A second anchoring suture is then placed further along the tube to attach the tube via a suture on the head between the eyes or along the side of the face (care must be taken to avoid the tube touching the whiskers in cats).

An Elizabethan collar is then placed to avoid inadvertent removal of the tube by the patient.

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3

4

5

6

7

8

9

10

2

Application of local anaesthetic to the nares of a cat to facilitate placement of the naso-gastric feeding tube.


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The patient is anaesthetized, intubated, and placed in right lateral recumbency with the mouth held open by an oral speculum.

The surgical field is aseptically prepared from the mandibular ramus to the thoracic inlet and extended to the dorsal and ventral midlines. Placement of the tube on the left side is preferred due to the anatomi-cal location of the oesophagus.

A feeding tube is premeasured and marked from the midcervical oesophagus caudal to larynx to the 7th-8th intercostal space if the distal tip is to lie in the distal oesophagus or to behind the 13th rib if the distal tip is to lie within the stomach. The feeding tube should be long enough to allow several centimeters to remain exterior to the skin post-placement. The size of the feeding tube depends upon patient size but com-monly ranges from 12- to 14-French for cats and up to 20-French for dogs. Red rubber, polyurethane, or silicone tubes may be used.

Depending upon the feeding tube, the distal exit side hole may be enlarged to facilitate passage of the diet.

Curved forceps (eg, Kelly, Carmalt) are placed in the mouth and advanced to the midcervical oesophagus distal to the hyoid apparatus. With the patient in lateral recumbency, the curved tip of the forceps is pushed dorsally, tenting the skin and palpated externally. The jugular groove is identified to avoid major vasculature and nerves.

A small incision is made on the tented skin over the tip of the forceps through the oesophageal wall.

The forceps tip is exteriorized by blunt dissection and with incision of the oesophageal mucosa.

The distal end of the feeding tube is grasped with the forceps and pulled through the incision and out the oral cavity. The tongue is retracted to facilitate redirection of the feeding tube.

1

3

2

4

5

A patient being prepared for placement of an oesophagostomy tube placement.

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6

8

PLACEMENT TECHNIQUEFOR OESOPHAGOSTOMY TUBES


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The end of the tube is lubricated, retroflexed, and pushed down the oesophagus while the proximal end of the tube is slowly retracted a few centimeters.

The proximal end of the tube will rotate cranially as the tube straightens to the proper orientation. The tube should slide easily back and forth a few millimeters and can be advanced to the premarked site on the tube.

The oropharynx is visually inspected to confirm that the tube is no longer present.

The incision site is re-scrubbed and the tube is secured with purse-string and Chinese finger-trap sutures using polypropylene suture material.

Several techniques may be preformed to verify cor-rect placement of the feeding tube, including use of capnography; however radiographic confirmation is recommended.

Antibiotic ointment on a non-adherent pad is placed over the surgical site and a light wrap is applied.

The tube is marked at the exit site to monitor for migration. The tube should be flushed with sterile saline to assess for a cough response and to introduce a column of liquid in the tube. The tube remains capped when not in use.

To avoid accidental administration of food into an intravenous catheter (termed ‘enteral misconnection’) all feeding tubes should be clearly labeled.

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Radiography to control proper placement.

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Meeting Nutritional Needs and Special Considerations

There is much that remains unclear regarding the nutritional requirements of critically ill animals in general. In certain circumstances assumptions are made that nutritional requirements in animals are similar to that of people afflicted with similar diseases. However, it is important to recognise that there may be significant species and disease differences that make such direct comparisons or extrapolations less applicable. Experimental data suggests that there are dramatic changes in energy requirements in animals with thermal burns, however, this does not appear to apply to clinical cases with critical illnesses. In the absence of definitive data to suggest otherwise, current recommendations are to start nutritional support as soon as it is deemed safe and initially target the resting energy requirements (RER) but to reassess the patient continually as energy requirements may exceed 2 x RER in some cases.

The goal of nutritional support is to optimise protein synthesis and preserve lean body mass. With this in mind, the current recommendation is to feed 5-6 g protein per 100 kcal (25-35% of total energy) in dogs and 6-8 g protein per 100 kcal (30-40% of total energy) in cats. Patients with protein intolerance, e.g., hepatic encephalopathy, severe azotaemia should receive reduced amounts of protein (e.g., 3-4 g protein per 100 kcal in dogs). Similarly, patients with hyperglycaemia or

hyperlipidaemia may also require decreased amounts of simple carbohydrates and fat, respectively. Other nutritional requirements will depend upon the patient’s underlying disease, clinical signs, and laboratory parameters.

Stupor in a cat suffering from hepatic lipidosis.

Critically ill dog with anorexia.


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Nutritional Plan

CHOOSING THE MOST APPROPRIATE DIET

The guiding principle regarding the diet to be used to support a patient will depend on the needs of the patient. The composition of the diet needs to reflect the dietary needs of the patient (e.g., higher protein requirements in catabolic patients, fat restriction in hyperlipi-daemic patients). Generally speaking, critically ill patients should be fed a calorically dense, high protein and fat diet. However, patients that have specific contraindications to high protein (e.g., chronic kidney failure, hepatic encepha-lopathy) should be fed a moderately restricted protein diet. In animals with gastrointestinal diseases, there may be a need to restrict fat

content in the diet. The chosen diet must also be able to be fed via feeding tubes. Liquid diets have the advantage that they can be delivered virtually via any feeding tube. However, it is im-portant to consider the caloric density of these liquid diets. Diets that require a large amount of water to be blenderised in order to get through feeding tubes drops the caloric density of the diet and also means that large volumes of the diet will be required. Diets for tube fee-ding should be energy and nutrient dense (1-2 kcal/ml) and highly digestible, allowing lower feeding volumes to be used.

CALCULATING ENERGY REQUIREMENTS

The patient’s resting energy requirement (RER) is the number of calories required for maintaining homeostasis while the animal rests quietly. The RER is calculated using the following formula:

Traditionally, the RER was then multiplied by an illness factor between 1.0-1.5 to account for increases in metabolism associated with diffe-rent conditions and injuries. Recently, there has been less emphasis on these subjective illness factors and current recommendations are to use more conservative energy estimates to avoid overfeeding and so illness factors are usually not applied when formulating feeding plans of critically ill patients. Overfeeding can result in metabolic and gastrointestinal complications,

hepatic dysfunction, increase carbon dioxide production, and weaken respiratory muscles. Of the metabolic complications, the development of hyperglycaemia is most common.

Currently, the RER is used as an initial estimate of a critically ill patient’s energy requirements. It should be emphasized that these general guidelines should be used as starting points, and animals receiving nutritional support should be closely monitored for tolerance of nutritional interventions. Continual decline in body weight or body condition should prompt the clinician to reassess and perhaps modify the nutritional plan (e.g., increasing the number of calories provided by 25%).

RER (in kcal) = 70 x (body weight in kg)0.75


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The prescribed amount of food is administered over 15 to 20 minutes

and fed every 4 to 6 hours. The volumes of food that

can be fed per feed should typically be less

than 10 ml/kg.

To implement enteral nutritional support, a feeding tube is typically required. Placement of a feeding tube is recommended whenever voluntary eating by the patient is lacking in sufficient amounts to meet at least 80% RER. Once a feeding tube is in place, a diet preparation that is suitable to meet the nutritional needs of the patient and appropriate for the tube is chosen. Small-bore tubes such as those typically used for nasoesophageal placement, or jejunostomy tubes, require complete liquid diets. Gruel-type diets require larger-bore tubes such as oesophagostomy and gastrostomy tubes and the preparation of these diets may require the use of a kitchen blender. Alternatively, there are veterinary diets that have been especially formulated for use via feeding tubes. Other considerations for choosing a diet include fat content, protein content, and caloric density of the food. The next consideration involves the manner in which food is delivered ; animals with naso-oesophageal, oesophagostomy, and gastrostomy tubes tolerate bolus feedings in which the prescribed amount of food is administered over 15 to 20 minutes and fed every 4 to 6 hours. The volumes of food that can be fed per feed should typically be less than 10 ml/kg ; however, some patients will not tolerate being fed any more than 2 mL/kg whilst some animals can tolerate 30-40 mL/kg per feed.

Regardless of the severity of malnutrition, one must remember that the immediate goals of therapy in any critically ill patient should focus on proper cardiovascular resuscitation, stabilisation of vital signs, and identification of primary disease process. As steps are taken to address the primary disease, formulation of a nutritional plan should aim to mitigate overt nutritional deficiencies and imbalances. By providing adequate energy substrates, protein, essential fatty acids, and micronutrients, the body can support wound healing, immune function, and tissue repair. A major goal of nutritional support is to minimise metabolic derangements and the catabolism of lean body tissue. During hospitalisation, recovery of normal body weight is not the top priority as this should occur once the animal is discharged from the hospital and completing its recovery at home.

Implementing Nutritional Plan

ANOREXIA DURATION RECOMMENDATION APPLICATION

Anorexia < 3 days

Plan to meet the requirements over 3 days Day 1 : of requirements Day 2 : of requirements

Day 3 :Full requirments

If anorexic ≥ 3 days

Plan to meet the requirements over 5 days

Day 1 : of requirements




Day 5 : Full requirements


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Monitoring and Reassessment

Body weights should be monitored daily in all patients receiving nutritional support. However, the clinician should take into account fluid shifts in evaluating changes in body weight. For this reason, body condition score assessment is important as well. The use of the RER as the patient’s caloric requirement is merely a starting point. The number of calories provided may need to be increased to keep up with the patient’s changing needs, typically by 25% if well tolerated. In patients unable to tolerate the prescribed amounts, the clinician should

consider reducing amounts of enteral feedings and supplementing the nutritional plan with some form of parenteral nutrition.

With continual reassessment, the clinician can determine when to transition patient from assisted feeding to voluntary consumption of food. The discontinuation of nutritional support should only begin when the patient can consume approximately 75% of its RER without much coaxing.

• Ribs visible on shorthaired cats

• Obvious waist• Very small amount

of abdominal fat• Marked abdominal tuck

• Ribs easily palpable and may be visible with no palpable fat

• Tops of lumbar verte-brae visible, pelvic bones becoming prominent

• Obvious waist and abdo-minal tuck

• Ribs, spine and pelvic bones easily visible on shorthaired cats

• Very narrow waist• Small amount of muscle• No palpable fat on the

rib cage• Severe abdominal tuck

• Ribs, lumbar vertebrae, pelvic bones and all bony prominences evident from a distance

• No discernible body fat• Obvious loss

of muscle mass

TOO THIN

BODY CONDITION SCORE


22

Possible complications of enteral nutrition include mechanical complications such as clogging of the tube or early tube removal. Metabolic complica-tions include electrolyte disturbances, hyperg-lycaemia, volume overload, and gastrointestinal signs (eg, vomiting, diarrhoea, cramping, bloating). In critically ill patients receiving enteral nutritional support, the clinician must also be vigilant for the development of aspiration pneumonia. Monitoring parameters for patients receiving enteral nutrition include body weight, serum electrolytes, tube pa-tency, appearance of tube exit site, gastrointestinal signs (eg, vomiting, regurgitation, diarrhoea), and signs of volume overload or pulmonary aspiration. The complications associated with nasoesophageal feeding tubes are relatively minor and are unlikely to result in significant morbidity. In one study, the most common com-plications seen with the use of nasogastric feeding tubes were vomiting, diarrhoea and inadvertent tube removal, which occur-red in 37% of patients. Other minor compli-cations (e.g., irritation of nasal passages, sneezing) can occur during the placement of the tube or as a consequence of the indwelling tube. A recent study comparing complications associated with nasoesophageal versus naso-gastric feeding tubes found no difference in rates of complications. To prevent inadvertent use of the nasoesophageal tube for anything other than feeding, the feeding tube should be clearly labelled. Complications associated with oesophagostomy feeding tubes are relatively uncommon and typically minor to moderate. There was no difference in com-plication rate or severity in one retrospective study comparing esophagostomy tubes to percutaneous endoscopic gastrostomy tubes. Serious complica-tions such as inadvertent placement in the airway or mediastinum or damage to the major vessels and nerves can be avoid by proper placement tech-

nique and verifying position of the tube radiographi-cally. Midcervical placement minimizes the risk of gagging and partial airway obstruction. Proper tube size and material decrease the risk of oesophageal irritation. Proper patient evaluation to ensure the pet can protect his airway in the event of vomiting is critical to lessen the risk of pulmonary aspiration. If the patient vomits, tube placement should be veri-fied to ensure it has not been displaced. Complications related to the stoma site or mecha-nical issues with the tube are possible. Peristomal cellulitis, infection or abscess may occur. Peristo-mal inflammation is a more common complica-tion. It can be managed in mild cases with through cleaning and topical antibiotics while more severe cellulitis or abscessation may require systemic antibiotics and tube removal. These risks can be

minimized by ensuring the tube is secured properly and the stoma site is kept clean and protected. Mechanical issues with the tube include premature removal, kinking, or clogging. Risk of pre-mature removal can be minimized by using an

appropriately sized tube size for patient comfort. The tube should be securely sutured and wraps should be comfortable. An Elizabethan collar may be needed in some cases. Kinking can occur du-ring tube placement or after vomiting and can be detected radiographically. Completely flushing the tube with water after every use decreases the risk of tube obstruction. The diet used should have the proper consistency to be easily fed through the feeding tube. In addition, the administration of medications through the tube should be avoided or performed with caution as it could lead to clo-gging of the tube. Tube obstructions may dislodge with warm water by applying pressure and suc-tion. Other methods include infusing a carbonated beverage or a solution of pancreatic enzyme and sodium bicarbonate.

Complications

Complications associated with feeding tubes

are relatively uncommon and typically minor

to moderate.


23

While critically ill patients are often not regarded as in urgent need of nutritional support given their more pressing problems, the severity of their injuries, altered metabolic condition, and necessity of frequent fasting, place these patients at high risk of becoming malnourished during their hospitalisation. Proper indication of these patients and careful planning and execution of a nutrition plan can be key factors in the successful recovery of these patients.As our understanding of various disease pro-cesses and their interactions with metabolic pathways improve, along with the refinement of nutritional support techniques we can provide, there is indeed great optimism that nutrition can have a significant positive impact on the recovery of critically ill patients.

Conclusions

Careful planning and execution of a nutrition plan can be key factors

in the successful recovery of critically ill patients.


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