is a particularly dangerous drug from the standpoint of causing GUE. It is extremely potent and can be devastating if combined with steroids like dexamethasone. While able to cause significant ulceration and bleeding all by themselves, the ulcerogenic potential of NSAIDs is particularly augmented by other factors, especially concurrent administration of another NSAID or a corticosteroid, and hypoperfusion of the alimentary tract. Even though many dogs seemingly tolerate such combination therapy, you need to realize that you are "walking on thin ice" (see comments above on use of ultra-low dose aspirin). Many to most of the dogs treated with NSAIDs have endoscopically visible erosions, haemorrhages and/or ulcers, depending upon the drug used and the dose administered. It is important to note that most dogs with GUE due to NSAIDs may be completely asymptomatic. Finally, there is tremendous between-dog variation regarding the alimentary tract response to NSAIDs; some dogs may almost bleed to death because of a small dose of aspirin while most dogs would tolerate a much larger dose with relative impunity.

While the newer Cox-2 NSAIDs (e.g., carprofen, etogesic, deracoxib, meloxicam, etc) have much less potential for causing GUE than the older NSAIDs, you can still see GUE (and even perforation) due to these drugs. Part of the problem is that these "safe" drugs are being used so extensively and casually. The problem often revolves around using inappropriately high doses (after all, the drug is so safe that ...), using the drug at the wrong time (e.g., when the patient is experiencing shock or has poor perfusion to the alimentary tract), and possibly using the drug too soon after stopping some other NSAID. The concept of a "washout" period when changing from one NSAID to another is extremely controversial. There is published literature to the contrary, but the fact is that nobody really knows at this time.

## CLINICAL APPROACH TO THE PATIENT WITH HAEMATEMESIS OR GI BLEEDING:

There is often something in the history that is suggestive of the cause of the bleeding (e.g., use of NSAIDs, shock, etc). If that is the case, then it is often reasonable to begin appropriate therapy after requesting basic laboratory testing (e.g., CBC, serum chemistry panel) to determine the severity of the bleeding and if there are other diseases (e.g., hepatic disease, renal disease) present. Imaging (especially ultrasound) is typically appropriate but not necessarily imperative at this time. If the cause of the GI bleeding or haematemesis is not obvious, if the patient has not responded to 5-7 days of appropriate therapy, or if the bleeding is severe, then additional diagnostics are important and should be performed promptly.

**Medical management:** If the patient is not exsanguinating, the cause is known or strongly suspected, and the patient has not had 5-7 days of appropriate medical therapy, then medical therapy is often reasonable as opposed to doing a major diagnostic work up. In distinction, if the patient is exsanguinating or if the patient has not shown any appreciable response to 5-7 days of appropriate medical therapy for the ulceration, then it is usually reasonable to surgically resect the ulcerated area. Note - when I say "response", I am not referring to the patient being cured; I am referring to clear evidence of improvement. If surgery will be considered, it is usually very wise to perform gastroduodenoscopy before the surgery to be sure that you find all of the sites of ulceration. It is very easy to fail to detect an ulcer at surgery, and endoscopy usually allows one to easily find all areas of ulceration. Sometimes intraoperative endoscopy is necessary to help the surgeon find the ulcer(s).
If medical management is elected, first be sure to remove the cause of the GUE. If the cause is not removed, medical management tends to be far less successful. Next, be sure that the patient is well hydrated; healing of the gut requires or is at least benefitted by adequate perfusion. If there is significant gastroduodenal reflux of bile, metoclopramide or cisapride may be helpful in preventing bile from entering and/or staying in the stomach and augmenting the ulcerogenic process.

H-2 receptor antagonists are, unfortunately, commonly used. Cimetidine, ranitidine, and famotidine are very poor medications for decreasing the gastric hydrogen ion concentration. Cimetidine (5-10 mg/kg) needs to be given 3-4 times per day if you are really serious about decreasing gastric acid secretion. Famotidine (0.5 mg/kg) only needs to be given once or twice daily. Ranitidine (2.2 mg/kg) is given twice daily, but may cause vomiting if given as an IV bolus. Side-effects of the H-2 receptor antagonists are rare but may include diarrhoea, drug eruption, hyperpyrexia, thrombocytopenia, granulocytopenia, and CNS problems including seizures. I think (?) I have seen a couple of dogs in which ranitidine was responsible for large bowel diarrhoea or seizures.

Proton pump inhibitors are the most effective antacid drugs we have. Omeprazole, lansoprazole and pantoprazole are the most effective inhibitors of gastric acid secretion we currently have available. In the USA, omeprazole is available OTC as Prilosec®. The dose of omeprazole is 1-2 mg/kg bid. The dose of lansoprazole (Previcid), pantoprazole (Protonix), and esomeprazole (Nexium) is 1 mg/kg IV (not approved for use in dogs). It generally takes 2-5 days for a PPI to have maximal efficacy; but, the immediate effect on gastric acid secretion is often still better than that obtained by high dose H-2 receptor blockade.

Misoprostol (Cytotec®) is a prostaglandin E analog which was primarily designed to be a prophylactic drug used to prevent GUE due to NSAIDs. It is also useful in treating existing ulcers, but its higher cost and more plentiful side effects usually make it undesirable as a first line therapy for GUE. It is typically used at a dose of 2-5 ug/kg, 3-4 times daily. It can cause abdominal cramping and diarrhoea, but the drug seems relatively safe in dogs. The main disadvantage is that it must be given orally, which is not possible in some vomiting animals. Because it is a prostaglandin analog, it should not be used in pregnant females for fear of causing abortion or miscarriage. It is the best drug available that can be used to prevent NSAID-induced ulceration, but it is not uniformly effective in dogs. The main indications to use it appear to be a) the patient that must have NSAIDs to function, but which evidences side-effects from them (e.g., anorexia, vomiting) and b) the patient that seemingly needs to receive NSAIDs that have substantial potential for such side-effects (e.g., piroxicam).

Sucralfate seems to be extremely effective in protecting those areas which are already ulcerated and helping them heal. The only common side-effect is constipation. There is minimal absorption from the intestines, but it does have the capacity for adsorbing other drugs (e.g., enrofloxacin). While carafate is effective in treating ulcers, it is not always effective in preventing ulceration. My major problem with this drug is that it must be given orally, which does not always work in vomiting dogs. The suspension form is probably more effective than the tablet form.
# RAW FOOD DIETS IN THE ICU: RECIPE FOR DISASTER?

Daniel L. Chan, DVM, DACVECC, DECVECC, DACVN, FHEA, MRCVS
The Royal Veterinary College, North Mymms, Hertfordshire, UK

## Introduction

In recent years there has been great interest by pet owners to feed unconventional diets to their pets. Most people claim that their primary interest is to improve the health of their animal, which they feel is not accomplished by using conventional commercial diets. Effective propaganda campaigns have swayed thousands of owners to question manufacturing practices of the pet food industry and to seek alternatives. Unfortunately information substantiating claims by the proponents of such diets is lacking. All food processing is being viewed as harmful and all things natural are viewed as beneficial. With greater acceptance in these types of diets, veterinarians need to be aware of the important issues surrounding this controversial topic and in particular the implications and risks this practice has to critically hospitalized critically ill animals in an ICU setting. The purpose of this lecture is to present some of concerns regarding raw food diets and other unconventional diets and highlight any evidence regarding the use of such diets.

## Why is this approach gaining acceptance?

Use of raw foods and other unconventional diets is obviously filling a niche not addressed by conventional pet food companies. There is a perception (mostly propagated by proponents of unconventional diets) that processing of pet foods is the cause of many ailments seen in the pet population. Conspiracy theories linking pet food industry and the veterinary profession are particularly interesting allegations. As an all-natural alternative, diets such as a Bones And Raw Food (BARF) appeal to those suspicious of the pet food industry (and of the veterinary profession). A group that quite readily accepted such notions was dog and cat breeders, who hold a great deal of influence over prospective pet owners. With the endorsement from many breeders, the movement to feed raw foods to companion animals gained a great deal of momentum. As new pet owners invariably receive the majority of advice on raising dogs solely from breeders, veterinarians are often left out of important decision-making such as choosing an appropriate diet.

## Where did this trend originate?

When one investigates the claims why raw food diets are 'superior,' a common cited reason is that dogs "were designed to eat raw food." From the types of teeth they have, to their evolutionary links, much of the justification of feeding raw food stems from the belief that dogs are healthier when fed as if they were "still in the wild." Leaving the issue of domestication aside, the notion that wild canids somehow were in ideal nutritional status when fed raw food is certainly unfounded. In fact, archaeological data suggests that prehistoric canids were omnivores and not pure carnivores. Modern wolves (which are often misrepresented as the reference species for domestic dogs) have evolved to consume prey mostly because of human encroachment in their habitats. So in reality, domestication of dogs not only introduced the dependence by dogs on humans for food, it also led to the changes in diets of wild canids. Domestication of both dogs and cats has resulted in remarkable prolongation and improvement in the quality of life for many animals, and many of the benefits could be directly linked with the provision of balanced and complete commercial diets. While improvements in food
palatability have probably contributed to the onset of obesity and associated conditions, consistent
use of balanced commercial diets has reversed malnutrition in many more patients.

What are the concerns?

In order to truly offer a balanced and informed analysis of the evidence on the potential risks and benefits of feeding raw meat-based diets would require the availability of data from high quality studies. Unfortunately there is very little data available to formulate a balanced analysis. Much of the information used to support one view or another on the merits and dangers of feeding raw meat-based diets are based on low quality studies composed of anecdotal reports, case reports and case-series. On the major issue of safety related to bacterial contamination, the evidence is more robust and more numerous, but comparative studies on the impact on the health of animals that consume raw meat-based diets are still lacking.

A particularly dangerous notion is that raw meat-based diets somehow pose no health risk because animals are “resistant to such infections.” While it is true that there may be a reduced risk, by no means are dogs immune to systemic infections due to enteric bacteria such as salmonella and campylobacter. In fact, dogs and cats with chronic or acute diarrhoea are commonly evaluated for salmonella and campylobacter infections. We know that dogs and cats can be severely affected by salmonellosis and campylobacter infections. But even if one accepts that many dogs and cats can consume contaminated raw-food diets and not become overtly ill, this is not to say they don’t pose a risk to others. In experimental studies, dogs fed Salmonella-contaminated food reliably shed Salmonella for many days without showing any gastrointestinal signs. The fact that many asymptomatic dogs can shed salmonella into the environment while appearing healthy has led to banning dogs that are fed raw-meat diets from being used as therapy dogs in some areas. There are also studies that have shown that a rise in cases of Salmonella in infants (some which are multi-drug resistant) could be traced to raw hide treats given to dogs. Recently, the FDA undertook a 2 year study evaluating the microbial contamination of conventional commercial pet foods in comparison to commercial raw-foods which showed the much higher risk of incidence of coliform and Listeria spp in commercial raw-meat foods. But perhaps most worrisome of all comes from a study evaluating a large group of healthy labradors that were not in any way exposed to veterinary hospitals or treated with any antibiotics (ie, lack of selection pressure associated with antimicrobial use). In these healthy dogs, not only was there a presence of clinically-relevant organisms isolated from these dogs, but also many harboured multi-drug resistant bacteria. Investigators also identified that the major factor in increasing the likelihood of having these bacteria was being fed a raw-meat based diet. The major significance of this study was that the profile of community bacterial colonization (ie, without selection pressures associated with antimicrobial use or contact with veterinary hospitals) is changing to reflect multi-drug resistant bacterial populations and is occurring due to feeding of raw-meat based diets. The obvious question (which has not been thus far investigated) is what risk do such animals that are fed raw-meat based diets pose to other animals in veterinary hospitals when they are hospitalized themselves? The most rational conclusion is that veterinary hospitals must perform a risk assessment about hospitalizing animals normally fed raw-meat based diets at home. Does your hospital accept such raw-meat based diets to be fed while the animal is hospitalized? And knowing that such animals could be shedding multi-drug resistant bacteria, including salmonella and campylobacter, what is your hospital policy for handling these animals? Should they be in isolation similarly to dogs and cats with other contagious infectious diseases? Until we have more direct
evidence to the contrary, it would seem sensible to ban feeding raw meat-based diets in hospital settings (especially ICUs) and that if animals normally fed in this manner are hospitalized, that barrier nursing protocols should be instituted.

## Implications for ICU patients

As already alluded to, the major concern with feeding raw meat-based diet centres on bacterial contamination of the diet and the risk posed to the animals fed in this manner, their owners and to other hospitalized patients. As many ICU patients are already immune-compromised, having animals that may be shedding virulent and multi-drug resistant bacteria in the ICU environment must be addressed by the hospital. Hospitals should have established policies and protocols for dealing with such cases. In the author's institution, there is a strict policy that no animal is to be fed raw foods and that whenever these animals are hospitalized, that barrier nursing protocols are instituted in the care of such patient (e.g., disposable protective clothing, gloves). All healthcare staff that comes in contact with such patients must adhere to good hygiene practice and all areas of the hospital that such patients come in contact with must be appropriately disinfected. Whether such animals must have mandatory screening for salmonella or multi-drug resistant bacteria is unknown at this point and each hospital should consider what should be done. It is also unknown if such animals such be isolated rather than barrier nursed, however, animals that require intensive care would be potentially compromised if cared for in isolation facilities. Another consideration is that the number of animals being fed raw-meat based diets will likely escalate and it would be unfeasible to manage all of such patients in isolation.

## Summary

Given the absolute and passionate devotion to the practice of feeding raw meat-based diets demonstrated by many pet owners, breeders, and even veterinarians, it is safe to say that this way of feeding is here to stay. Despite growing evidence highlighting the possible dangers to both animals fed such diets and public health concerns amongst those that feed these diets, many are swayed by the appeal of feeding a "natural diet." It is probably worth noting that growing scientific knowledge highlighting possible or likely dangers will not necessarily influence a segment of pet owners because "scientific evidence" is not what guides their relationship with their pets. Veterinarians should not lose sight of this. Nevertheless, given our growing understanding of these dangers, it is our duty to educate pet owners about the risks both to their pets as well as to themselves and their families. In terms of the implications to hospitalized patients in the ICU, animals fed raw-meat based diets pose a tangible risk to other ICU patients. Hospitals should adopt policies and protocols to reduce the risk of disease transmission within the hospital environment related to animals fed raw-meat based diets. We should remain vigilant to the risks posed by the growing trend of feeding raw-meat based diets to dogs and cats, and frequently re-evaluate our policies and procedures so that we can minimize the risk to our patients.

## References

* Billinghurst, I. Give your dog a bone. Bridge Printery, Alexandria, Australia, 1993

* Bowen J. Canine feeding behavior. Vet Focus 2014;24:8-15.

* Finley R, Ribble C, Aramini J, et al. The risk of salmonellae shedding by dogs fed Salmonella-containing commercial raw food diets. Can Vet J 2007;48:69-75
Freeman LM, Chandler M, Hamper BA, et al. Current knowledge about the risks and benefits of raw meat-based diets for dogs and cats. J Amer Vet Med Assoc 2013;243, 11, 1549 - 1558.

Freeman LM, Michel KE. Evaluation of raw food diets for dogs. J Amer Vet Med Assoc 2001; 218, 5, 705 – 709.

Handl S. The “BARF” trend – Advantages, drawbacks and risks. Vet Focus 2014;24:16-23.
Lefebvre SL, Reid-Smith R, Boerlin P, Weese JS. Evaluation of the risk of shedding salmonellae and other potential pathogens by therapy dogs fed raw diets in Ontario and Alberta. Zoonoses Public Health 2008; 55:470-480.

Nemser SM, Doran T, Grabenstein M, et al. Investigation of Listeria, Salmonella, and Toxigenic Escherichia coli in various pet foods. Foodborne Pathogens and Disease. 2014;11,9,706 – 709.

Schmidt VM, Pinchbeck GL, Nuttall T, et al. Antimicrobial resistance risk factors and characterisation of faecal E. Coli isolated from healthy Labrador retrievers in the United Kingdom. Prev Vet Med 2015;119:31-40.
# CHALLENGING ABDOMINAL IMAGING CASES

Livia Benigni, DVM, CertVDI, PGCertAP, MRCVS, FHEA, DipECVDI

Youliv4 Imaging Referrals and The Ralph Veterinary Referral Centre, London, UK

A few examples of challenging abdominal imaging cases are reviewed and discussed.

## Biliary Tract

Cholecystocentesis is considered a relatively safe technique and it is routinely performed in many veterinary hospitals.¹ Therapeutic cholecystocentesis has been proposed as a way of relieving the pressure from the biliary system in patients suffering from extrahepatic biliary obstruction secondary to pancreatitis.² However bile leakage and subsequent peritonitis are potential complications of percutaneous cholecystocentesis. Currently there is limited published information regarding the success rate of this procedure in the veterinary field.

## Pancreatitis

Early diagnosis of acute pancreatitis is essential as it carries a high mortality rate in dogs. In order to reach a diagnosis of acute pancreatitis the clinician takes into consideration clinical history, physical examination, serum biochemistry (including the Spec cPL assay for canine pancreatic lipase), and abdominal ultrasound results. The reported sensitivities and specificities of these tests are variable; thus, these tests are sometimes insufficient to reach a final diagnosis.

A recent study comparing ultrasound and computed tomographic angiography (CTA) in the diagnosis and evaluation of acute pancreatitis in dogs showed that, in comparison to US, CTA better identified dogs with more severe acute pancreatitis and those with portal vein thrombosis, factors that may predict longer hospitalization and increased risk of relapse.³

It is important to notice that a 3-phase CTA protocol was used for this study. The authors used a 16-slides CT, a bolus trace protocol and a power injector.

## Normal Renal Pelvis, Ureteral Calculi and Pyelonephritis

Urinary tract obstruction secondary to ureteral calculi has become increasingly common in feline veterinary medicine. Young patients are often affected and present with non-specific signs of renal failure. Diagnostic imaging is essential to identify the calculi and differentiate urinary obstruction from other causes of renal failure. Ultrasound is an effective imaging modality to identify dilatation of the renal pelvis and urinary calculi, including ureteral calculi.

An attempt by d'Anjou et al. was made to determine whether it is possible to predict the underlying cause of renal pelvis dilatation on the basis of the size of the renal pelvis dilatation measured on ultrasound.⁴ Dogs and cats with hydronephrosis were divided in 6 groups: clinically normal renal function, normal renal function with diuresis, pyelonephritis, acute or chronic renal insufficiency, obstructive disorders and a miscellaneous group. Minimal to mild dilatation of the renal pelvis (RP) was observed in patients with clinically normal renal function. Mild to moderate dilatation of the renal pelvis has been associated with increased diuresis (e.g. secondary to intravenous fluid administration, diuretics administration), pyelonephritis, outflow obstruction and chronic parenchymal renal disease.
Dilatation of the renal pelvis is variable in dogs and cats with pyelonephritis (dogs = 5.6 +/- 3.7 mm; cats = 4.6 +/- 3.6 mm). The RP can be up to 12 mm but also minimally dilated (below 2 mm). Minor dilatation of the renal pelvis may be related to the short duration of the infection. In conclusion only when the pelvic width was more than 13mm it was possible to reliably associate it with obstruction. Renal pelvis width in ten cats with clinically normal renal function was between 0.8 and 3.2 mm. In case of renal pelvis width of less than 13mm, it was not possible to differentiate between the groups on the basis of imaging alone.

## Ultrasound-guided Antegrade Pyelogram

Intravenous urography is often not particularly useful to diagnose ureteral obstruction because of the ureter is not clearly visualised due to lack of contrast excretion secondary to renal failure. The same problem can occur when performing computed tomography after intravenous administration of contrast.

In the presence of hydronephrosis, when the cause of obstruction is not readily identified, an ultrasound-guided antegrade pyelogram is indicated. Antegrade pyelography helps determining whether there is partial or complete obstruction. The study should be performed with the patient anaesthetized. The area over the kidney is clipped and aseptically prepared. The renal pelvis dilatation is measured and the safest path for insertion of the needle is selected with ultrasound. Under ultrasound guidance a hypodermic needle (23 gauge needle - 1 inch) connected to a small extension set and 3 way-taps is inserted into the renal pelvis. If possible urine is collected from the dilated renal pelvis before injection of contrast. The contrast injected is equal to 75%-100% of the urine volume removed. Lateral and ventrodorsal abdominal radiographs (or fluoroscopic images) should be obtained immediately, at 5 minutes and possibly at 15 minutes post-injection.⁵ This technique is also useful to detect possible ureteral tears.

## Abdominal Active Bleeding

In humans CT is used to demonstrate the presence of small sources of active bleeding in the peritoneal cavity. Identification of the “sentinel clot sign” defined as the highest attenuation haematoma adjacent to a bleeding organ in humans with haemoabdomen has been suggested as a potentially useful indicator of source of bleeding in dogs with haemoabdomen.⁶

## References

1. Sciborra F, McConnell JF, Maddox TW. Percutaneous ultrasound-guided cholecystocentesis: complications and association of ultrasonographic findings with bile culture results. J Small Anim Pract. 2017; 58(7): 389-39

2. Herman BA, Brawer RS, Murtaugh RJ et al. Therapeutic percutaneous ultrasound-guided cholecystocentesis in three dogs with extrahepatic biliary obstruction and pancreatitis. J Am Vet Med Assoc 2005; 227(11): 1728-1753

3. French JM, Twedt DC, Rao S et al. Computed tomographic angiography and ultrasonography in the diagnosis and evaluation of acute pancreatitis in dogs. J Vet Intern Med. 2019; 33(1): 79-88.

4. D'Anjou MA, Bedard A, Dunn ME. Clinical significance of renal pelvis dilatation on ultrasound in dogs and cats. Vet Radiol & Ultrasound 2011; 52(1): 88-94.
5. Kulendra NJ, Syme H, Benigni L et al. Feline double pigtail ureteric stents for management of ureteric obstruction: short- and long-term follow-up of 26 cats. J Feline Med Surg 16(12): 985-2014

6. Specchi S, Auriemma E, Morabito S et al. Evaluation of the computed tomographic “sentinel clot sign” to identify bleeding abdominal organs in dogs with haemoabdomen. Vet Radiol & Ultrasound 2017 Jan; 58(1): 18-22.
# RESPIRATORY ENDOSCOPY: WHEN IS IT AN EMERGENCY?

Michael D. Willard, DVM, MS, DACVIM

## INTRODUCTION

Respiratory procedures require relatively small diameter, flexible instruments. Although rigid equipment can be used, flexible is necessary to obtain a good examination. Flexible bronchoscopes are much like flexible gastroduodenoscopes except that the bronchoscopes are a) smaller in diameter (e.g., 5-6 mm in most cases, although there are some "ultra thin" scopes with diameters < 2-3 mm), b) do not have the ability to wash off the lens, c) are shorter, and d) have a tip that will flex in one plane only. There is a biopsy channel (typically 2.0 mm in diameter) which can be used for performing washes or aspirations, passing biopsy instruments or a foreign body retrieval device, and administering oxygen during some bronchoscopic procedures. In larger dogs, one can often use pediatric flexible gastroduodenoscopes for these procedures. However, in animals weighing less than 10-15 kg, it becomes excessively hard to use flexible gastroduodenoscopes with outer diameters > 7.9 mm (a major problem is that they are so large that they tend to occlude the trachea during the procedure). When examining the posterior nares, it helps to have a scope with a narrow flexing radius so that there is less pressure in the posterior nares (and hence less propensity to gagging).

Biopsy instruments are used through bronchoscopes just as for gastroduodenoscopes. However, they are not used as frequently. The most useful instruments used through bronchoscopes include sterile polypropylene tubes for washes and aspiration, and covered brushes for obtaining samples for cytology. Brushes can be particularly useful for obtaining a "deeper" cytology of an area. They should be used only once, because it can be extremely hard to adequately clean them off after use, and today's sample may be contaminated with last weeks sample if the brush is reused without scrupulous cleaning in between uses. Likewise, it is best to use aspiration tubes once and then discard them. We make our own at minimal expense by attaching soft plastic tubing and blunt needles. Because the foreign bodies found in the respiratory tract tend to be much different than those found in the alimentary tract, one seldom needs such a wide array of devices as are needed for gastroduodenoscopes. Biopsy cup forceps and "W"-type coin retrieval forceps are usually more than adequate (although occasional odd objects are found that require specialized equipment).

## BRONCHOSCOPY

Bronchoscopy is primarily indicated in animals with pulmonary parenchymal or airway disease such as coughing, exercise intolerance, stridor or dyspnoea. This is especially true when the more common causes have been eliminated. Brush cytology or directed washings (e.g., bronchoalveolar lavage) are often particularly useful. The primary reason bronchoscopy becomes an emergency procedure is when patients are dyspnoeic/hypoxic and the suspected cause is obstruction. The most common causes of obstruction are laryngeal/pharyngeal disease (e.g., everted lateral saccules), collapsing trachea, tracheal-bronchial foreign body, and tracheobronchial mass [tumour or granuloma]).

No special preparation is needed before this procedure, and in the case of emergencies, there is no time for such. Narcotic preanaesthetics (e.g., oxymorphone, 0.05 to 0.1 mg/kg, or butorphanol, 0.22 mg/kg, followed by an anticholinergic) can make the examination easier by suppressing coughing. If only the lower airways will be examined to remove a foreign body or mass or perform a
bronchoalveolar lavage or a brushing, then it is acceptable to induce anaesthesia with a barbiturate or propofol and then maintain with isoflurane. The bronchoscope can be passed through the endotracheal tube if it has a large enough diameter. However, one must be very careful to make sure that the bronchoscope does not obstruct the endotracheal tube and suffocate the patient. If the endotracheal tube is too small to allow the scope to be used, then one must use injectable agents to maintain anaesthesia. Propofol (4 to 6 mg/kg) may be given to effect to maintain anaesthesia; it is noncumulative and can be given as needed. Oxygen may be insufflated through the biopsy channel of the endoscope during the examination. However, it is important to not obstruct the airway with the scope and cause barotrauma. If the patient is maintained by injectable rather than inhalant agents, a mouth gag is necessary.

## FOREIGN BODIES

The removal of foreign bodies in the respiratory tract is usually not too much different than removing them from the GI tract. The same retrieval devices are used, and the techniques are the same. However, one foreign body that can be particularly difficult is the broken canine tooth that heads down the respiratory tract point first. This results in the endoscopist finding a "blank wall" (i.e., the broad surface of the broken canine) which effectively plugs the bronchi and makes it very difficult to find a place to grab the foreign object. The most effective technique is to use W-type coin removal forceps and try to force the edges of the forceps between the bronchi and the edge of the broken tooth. Finding seeds and small sticks can be difficult if the foreign object has been there for any length of time. The longer the foreign object is present, the more mucopurulent mucoid exudate accumulates around it, making it harder and harder to see. Finding that one bronchus is filled with such mucus is a sign that it needs to be investigated. The endoscopist should carefully insert partially opened alligator forceps and blindly grasp and pull. Do not pull too hard in case you have accidentally grabbed bronchus instead of a foreign body.

## TRACHEAL COLLAPSE

This is a common event. The value of endoscopy is that it can diagnose cases that are missed by fluoroscopy (yes, you can have severe tracheal collapse and not see it on fluoroscopy). Respiratory endoscopy can better define the extent and severity of the collapse. If the patient is dyspnoeic under anaesthesia, it can be hard to pass the scope through the larynx. Aim the tip of the endoscope for the ventral most aspect of the laryngeal opening and slide the tip along this ventral surface. If you are insufflating air while you do this, you can usually improve the patient's oxygenation. If a stent is needed, that is best performed under fluoroscopic imaging.

## LUNG LOBE TORSION

An uncommon event, it is important. One can often see the bronchus of the affected lobe literally twisting and closing off that particular lung lobe.

## RESPIRATORY TRACT BLEEDING

Bronchoscopy is usually a diagnostic procedure in patients with respiratory tract bleeding because most sources of bleeding are deeper in the lung parenchyma as opposed to the trachea or major bronchi. Therefore, bronchoscopy is usually used to determine which lung lobe needs to be resected. In rare cases the source of the bleeding will be in the trachea and bronchi and can be cauterized or removed.
## TRACHEAL TEARS

This is usually due to placement of an endotracheal tube, and especially in cats. Such a tear is an absolute contraindication to scope the respiratory tract of the patient. First, you may or may not be able to find the tear, but you will almost certainly worsen the tear during the procedure. Second, this is not an indication for surgery unless the tear is so severe that it is resulting in a tension pneumothorax (and this is exceedingly rare event). Just put the patient in a cage and leave it alone. The tear will eventually seal over without problem.

## DIAGNOSTIC PROCEDURES

Sternal or lateral recumbency is used unless a bronchoalveolar lavage is going to be done, in which case lateral recumbency with the side to be sampled placed down is necessary. The scope is lightly lubricated and carefully advanced through the arytenoids or the endotracheal tube. When you reach the carina, you should carefully examine each bronchus by advancing the scope as far into it as possible. Do not advance the scope if you feel resistance, even if the path in front of you seems to be "wide open". Remember that the scope is larger than the image seen. It is especially easy to tear the feline trachea.

For bronchoalveolar lavage, you should gently advance the tip of the scope or a sterile tube as far as possible into a particular dependent bronchus. Be sure that you do not completely occlude the airway, and then instill sterile, physiologic saline solution into the bronchus. We usually use 25-mL aliquots in dogs and 5-mL/kg aliquots in cats. Aspirate it immediately after you have instilled it. In dogs, you should repeat the procedure on the same lung lobe. Dogs and cats with respiratory disease can become hypoxic for anywhere from several minutes to a few hours right after the bronchoalveolar lavage. These patients may need respiratory support (i.e. an oxygen cage and bronchodilators).

## EXAMINATION OF THE CHOANA

The animal must be in a very deep plane of anaesthesia or it will gag. A narcotic preanaesthetic is recommended. A cuffed endotracheal tube is mandatory if a biopsy will be done. The patient is best positioned in sternal recumbency. The mouth is held open with a strong mouth gag, and then the tongue is pulled forward while the tip of the scope is placed beyond the caudal margin of the soft palate. The tip of the scope is then maximally deflected dorsally. At this point, you should be able to see the choana. If a biopsy is desired, it is best to place the biopsy instrument into the biopsy channel such that the tip is just about ready to protrude from the tip before retroflexing the tip of the scope. Trying to force the biopsy instrument through the channel after maximally deflecting the tip can easily damage or destroy the scope. The most common findings in this area are foreign objects and tumours.

## CHOANAL FOREIGN BODIES AND STRICTURES

If an animal vomits vigorously, a foreign body may by propelled past the base of the tongue and into the choana. One must be careful in trying to remove such foreign bodies because the tip of the scope is maximally retroflexed (making it easier to damage the biopsy channel of the insertion tube). Sometimes such foreign bodies can be pushed out by vigorously flushing large volumes of water into the nose under as much pressure as possible. Strictures may occur at the choana, obstructing the posterior aspect of the nasal cavity. Such strictures are potentially very difficult to treat, and these cases should be referred to a specialist with experience in such cases.
ELECTROCAUTERY

Use of electrocautery in the respiratory tract is an uncommon event. The following discussion presupposes that the clinician has experience with endoscopic electrocautery (typically in the GI tract). If you do not know and fully understand concepts such as "current density" and "capacitance" as well as the fundamentals of polypectomy and how to protect both the patient and the endoscope, you should not attempt electrocautery in the respiratory tract.

It is especially important when working in the relatively cramped space of the respiratory tract to keep the tip of the electrocautery probe or snare away from the tip of the endoscope. If you activate the electrosurgery device when the tip of the instrument is in close proximity to the tip of the endoscope, it is possible to send a current up the insertion tube and even into the video processor. While this is a rare occurrence, it has the potential to destroy the camera in the tip of the insertion tube and the video processor (both of which are potentially expensive propositions).

However the most important consideration is the fact that activating the almost any electrocautery instrument in the respiratory tract when oxygen is being infused is almost guaranteed to kill the patient. Such an action can literally ignite the tracheal/bronchial mucosa and burn up the epithelium of the entire system of airways. This has happened in people and there is no reason to believe it will not happen in dogs and cats. Insufflation of room air through the endoscope during the procedure will generally be sufficient to support the patient and allow the procedure to occur safely.
# AN UPDATE ON HYDROXYETHYL STARCH: DEBATE ON CURRENT USE

Isabelle Goy-Thollot¹ and Katja-Nicole Adamik²

¹Dr Vet, PhD, DECVECC, SIAMU, VetAgro Sup, Lyon, France;

²PD Dr. med. vet, DACVECC, DECVECC, Vetsuisse Faculty, University of Bern, Switzerland

## Background

Synthetic colloids are widely used in veterinary medicine with hydroxyethyl starch (HES) being the most frequently used.¹ Moreover, HES is currently the most studied synthetic colloid in human and veterinary medicine in contrast to dextran and gelatin. HES preparations are characterized by the mean molecular-weight (MW in kilo Dalton [kDa]) of the HES molecule (equals molecular size), molar substitution (MS, mole hydroxyethyl residue per mole glucose subunit), C2/C6-ratio (locations of hydroxyethyl residues on the carbon atom of the glucose subunits), its concentration (e.g., 6% [60 g/L] versus 10% [100 g/L]), the carrier solution (normal saline versus polyionic, buffered, and balanced) and the starch-source (potato [HES 130/0.42) versus maize starch [HES 130/0.4]). They are further classified according to the MW into high-molecular-weight (>450 kDa), medium-molecular-weight (>200 kDa), and low-molecular-weight (<130 kDa) solutions, and according to the MS into highly substituted (hetastarch; 0.62–0.75), medium-substituted (pentastarch; 0.5), and low-substituted solutions (tetrastarch; 0.4).² The most frequently used HES preparation in small animals is the modern, low-molecular weight HES (6% HES 130/0.4, a maize-derived starch with 60g HES per 1000 mL carrier solution).¹

Two major concerns put the use of HES into question: Its anticipated effects (benefits) and its side effects (risks). Traditionally, the rationale for the use of HES preparations (and other colloids) was prevention of oedema formation by plugging capillary leaks, an increase in the intravascular colloid-osmotic pressure, reabsorption of fluid from the interstitium into the intravascular space with subsequent intravascular volume expansion and reduction of existing peripheral oedema, and a volume-sparing effect compared to isotonic crystalloids.³,⁴ However, the concept of colloid therapy was strongly based on the Starling concept, which was discovered more than 100 years ago. Many of these expectations are invalid, due to recent findings in the area of microcirculation and endothelial glycocalyx layer (e.g., ‘revised Starling’ model). In particular, there is no reabsorption from the interstitial space into the intravascular space (‘no absorption rule’).⁵ Two reviews (2013 and 2018) of the benefits and risks of HES by the Pharmacovigilance and Risk Assessment Committee (PRAC) of the European Medicines Agency were performed, which led to restrictions, contraindications, and changes to the warnings on HES product packaging (for people).⁶ The first review was triggered in 2012 by results from large randomized clinical trials (RCT) in people,⁷⁻⁹ which found an increased risk of mortality in patients with sepsis and an increased risk of kidney injury requiring dialysis in critically ill patients following treatment with HES. In addition to the already existing contraindications (e.g., renal failure), additional contraindications were introduced (e.g., sepsis, critically ill patients).⁶ The second review was triggered by the Swedish Medical Products Agency due to non-adherence to the restrictions from 2013 (e.g., HES solutions were used in patients with sepsis and kidney injury), with the aim to completely ban HES in the EU. The recommendation to ban HES was ultimately not endorsed; however, limitations on supply to only accredited hospitals, training of healthcare professionals, and additional packaging warnings were enacted. Several guidelines in human medicine recommend against HES due to the safety concerns. As such, current guidelines from the Surviving
Sepsis Campaign recommend crystalloids for initial resuscitation and subsequent volume replacement with albumin when patients require 'substantial' amounts of crystalloids.¹⁰ In contrast, the International Fluid Optimization Group (perioperative fluid therapy) did not recommend against HES, but instead the anaesthetist should assess patient specific risks (renal dysfunction and/or sepsis) prior to administering HES.¹¹ In veterinary medicine, HES cannot be easily replaced by albumin or plasma as the safety profile for human serum albumin solutions is worse compared with HES,¹²⁻¹⁴ and allogenic plasma or albumin products are not ubiquitously available and are more expensive. Therefore, synthetic colloids might be the only alternative if crystalloids are not sufficient. Unfortunately, no guidelines yet exist on the use of synthetic colloids or HES in companion animals and the controversy is still ongoing. The following sections elucidate the current evidence of the cons and pros of HES.

## Evidence opposing the use of HES

Use of HES solutions is controversial in human medicine because the use of these fluids may not achieve higher volume expansion than that expected crystalloids and may be associated not only with acute kidney injury but also with impaired coagulation.

It is commonly assumed that 3 to 4 volumes of crystalloid solution achieve similar plasma volume expansion as 1 volume of colloid solution. Recent data suggest it might depend on the integrity of the endothelial glycocalyx. The CRYSTMAS trial, a RCT in patients with severe sepsis in whom capillary integrity was likely compromised, showed that in people with naturally occurring sepsis, the crystalloid to colloid volume ratio was close to 1.2:1.¹⁵ Therefore, in clinical situations where the integrity of the glycocalyx may be compromised, synthetic colloids such as HES cannot be relied upon to maintain their superiority over crystalloids in terms of plasma volume expansion.

The coagulopathy associated with HES solutions may involve several mechanisms, including: (1) inhibition of the formation of the fibrin network because of binding and inactivation of factor VIII and von Willebrand's factor (vWF); (2) inhibition of blood clot formation by inhibition of glycoproteins GP IIb/IIIa located on the surface of activated platelets; (3) inhibition of the binding of GP IIb/IIIa platelet receptors to vWf and fibrinogen; and (4) acceleration of fibrin degradation.¹⁶,¹⁷ The properties of individual HES molecules vary according to their MW, MS ratio and the C2/C6 ratio. A high C2/C6 ratio appears to have the largest impact on haemostasis.¹⁸ HES solutions with smaller MW and lower MS are more rapidly degraded and eliminated with an apparent reduction in some adverse effects.¹⁶ In humans, numerous studies and meta-analyses show that patients receiving a synthetic colloid have increased risk of bleeding and require more blood product than patients receiving crystalloid fluid therapy.¹⁹ Likewise, some in vitro and in vivo studies in healthy dogs have demonstrated both primary and secondary haemostatic impairment with the administration of clinically relevant doses of synthetic colloids,²⁰,²¹ while others have not.²²,²³ Although studies showed that coagulation can be impaired by tetrastarch, the clinical application of these findings is not clear because tetrastarch was compared to equal volumes of isotonic crystalloids.²¹,²⁴ A recent study²⁵ showed that the use of tetrastarch for volume resuscitation after haemorrhage in healthy dogs induced a transient hypocoagulable state (2-4 hours) suggesting that tetrastarch induces dilutional coagulopathy that can be avoided by using lower volumes.²⁵ Notably, according to recent results in dogs suffering from spontaneous haemoperitoneum, HES should be used with caution in dogs with pre-existing coagulopathy and active haemorrhage.²⁶,²⁷
Three randomized clinical trials in people suggested an increased risk of AKI and mortality in critically ill human patients receiving HES compared with those receiving crystalloids.⁸,⁹ The pathophysiology of AKI secondary to synthetic colloid administration is not well understood, but is likely multifactorial. Osmotic nephrosis secondary to phagocytized HES molecules within proximal tubular cells is thought to be an important mechanism. HES induced AKI is dose- and time-dependent and leads to potentially reversible cellular vacuolization, cellular swelling and inflammation. Abnormal macrophage infiltration and “hyperoncotic AKI” have also been proposed as possible mechanisms for HES-induced AKI. In addition, due to its oncotic properties, HES administration decreases renal filtration pressure.²⁸ Phagocytosed intracellular HES can persist for up to 18 days in canine kidneys, depending on the dose received.²⁹ In humans with severe sepsis, patients receiving LRS are less likely to develop AKI and need renal replacement therapy (RRT) than patients receiving HES.⁹ To date, only retrospective studies have been published in the veterinary literature and the results are conflicting. Interpretation of these studies is also hampered by the lack of agreement on the definition of AKI. In a prospective study in septic dogs undergoing emergency laparotomy, dogs that received HES had increased neutrophil gelatinase associated lipocalin (NGAL) concentration compared to those that did not receive synthetic colloids,³⁰suggesting that HES administration caused renal epithelial injury. A retrospective cohort study,³¹ found that critically ill dogs receiving HES 250/0.5 had a higher incidence of AKI and non-survival to discharge compared to a control group.

Most RCTs in humans have demonstrated a trend towards an increase in mortality in patients receiving HES compared to crystalloids. In one retrospective study of critically dogs, administration of HES was associated with an increase in mortality.³¹ Likewise, in the Yozova et al. study of dogs receiving HES, those that received HES had a higher mortality rate than those that did not.³² In all of these studies, dogs in the HES group were significantly sicker and had lower albumin concentrations. They were also more likely to suffer from sepsis.

## Evidence on the positive aspects of HES

As described above, the use of HES may not achieve the expected higher volume expansion compared to isotonic crystalloids in patients with a non-intact endothelial glycocalyx. Inflammation, sepsis, ischaemia/reperfusion, and increased atrial natriuretic peptide are some of the conditions leading to glycocalyx layer destruction, with resultant increased vascular permeability, and oedema formation.³³,³⁴ Moreover, rapid administration of intravenous fluid can lead to endothelial glycocalyx damage.³⁵ However, in dogs with experimental haemorrhagic shock, endothelial glycocalyx shedding and inflammation were found to be significantly less after tetrastarch compared with the 4-fold volume of isotonic crystalloid.³⁶ Nevertheless, many studies aiming to prove the volume expanding effect of HES were performed in healthy or non-septic individuals. In non-septic people with hypovolaemia, the volume effect of tetrastarch is 90% compared to only 20% with isotonic crystalloids.³⁷ Likewise, in normovolaemic, healthy dogs, hetastarch led to the highest volume expanding efficiency after 30 minutes (blood volume increase by 140%) compared with hypertonic saline and normal saline, which lasted up to 4 hours.³⁸ Moreover, tetrastarch had a volume-sparing effect in experimental haemorrhagic shock in healthy non-septic dogs.³⁹ In dogs with LPS induced systemic inflammation, tetrastarch led to a transient increase in blood pressure compared with the same volume of crystalloid.⁴⁰ Similar to critically ill people,⁴¹ in critically ill hospitalized dogs and cats, fluid overload is a possible complication, which is associated with an increased mortality.⁴² Crystalloids have a marked redistribution, whereby 50% of the volume effect is lost within 20 minutes.⁴³ The
addition of a colloid during the resuscitation phase after a certain amount of crystalloids, may help to reduce the total volume of crystalloids and prevent fluid overload. A large human randomized controlled trial requiring fluid resuscitation for acute hypovolaemia with either colloids (the majority received HES) or crystalloids (CRISTAL trial) found a significant reduction in 90-day mortality, more vasopressor-free, and more ventilator-free days by day 28 in the colloid group. Subgroup analysis confirmed a significantly reduced 90-day mortality in patients treated with HES when compared with patients treated with 0.9% saline.⁴⁴

As described above, one major concern is the risk of AKI in patients receiving HES due to tissue storage and subsequent osmotic nephrosis. Notably, various drugs are described to cause osmotic nephrosis (e.g., intravenous immune globulins, mannitol, low-molecular-weight dextran, radiocontrast preparations).⁴⁵ According to the restrictions on the use of HES from 2013 (e.g., HES is contraindicated in septic and critically-ill people), newer studies on the risk for AKI in people were performed in surgical or perioperative populations. Interestingly, data in this population revealed that fluid therapy with HES was not associated with more AKI compared to crystalloids.⁴⁶,⁴⁷ Moreover, long term follow-up (up to 12 months) revealed no difference in renal function between patients that received HES vs. crystalloids.⁴⁸ In recent retrospective studies in critically ill dogs and cats (including some patients with sepsis), HES-treated patients (tetrastarch) were not more prone to develop AKI than HES-untreated (crystalloids),⁴⁹⁻⁵² although prolonged administration time (several days) led to AKI in some dogs in one study.⁴⁹ The authors of that study recommended to keep the time period of administration as short as possible. The retrospective character of the aforementioned studies are a major drawback and plasma creatinine might not adequately represent real kidney injury after HES. Nevertheless, recent data suggest that tetrastarch may not cause AKI, as measured by several renal biomarkers for AKI and renal histology, when used for volume resuscitation in experimental haemorrhagic shock in healthy non-septic dogs.⁵³,⁵⁴ However, no prospective clinical studies in naturally ill dogs or cats evaluating AKI after HES are available.

HES-induced coagulopathy is a known side effect in dogs and cats which is transient and dose dependent.²¹ However, in dogs without preexisting coagulopathy, tetrastarch did not impair platelet function beyond the effect of haemodilution, and only mildly impaired clot firmness and clot formation time was found.²²,²⁵,⁵⁵ It also remains unclear to what extent the changes in viscoelastic coagulation analyses after HES are clinically significant.

## Summary

In specific patient populations, tetrastarch is a potent volume expander with a volume-sparing and longer lasting effect compared with crystalloids. It is unclear, if the initial positive volume effect is associated with an improved outcome in dogs and cats. HES is undoubtedly a fluid with side effects which are dose and time-dependent. It should be administered only in states of acute hypovolaemia or perioperative hypotension, and at the lowest effective dose and over a short period of time.
References

1. Yozova ID, Howard J, Sigrist NE, et al. Current Trends in Volume Replacement Therapy and the Use of Synthetic Colloids in Small Animals-An Internet-Based Survey (2016). *Front Vet Sci* 2017;4:140.

2. Kozek-Langenecker SA. Effects of hydroxyethyl starch solutions on hemostasis. *Anesthesiology* 2005;103:654-660.

3. Adamik KN, Yozova ID, Regenscheit N. Controversies in the use of hydroxyethyl starch solutions in small animal emergency and critical care. *J Vet Emerg Crit Care* 2015;25:20-47.

4. Glover PA, Rudloff E, Kirby R. Hydroxyethyl starch: a review of pharmacokinetics, pharmacodynamics, current products, and potential clinical risks, benefits, and use. *J Vet Emerg Crit Care* 2014;24:642-661. 5. Woodcock TE, Woodcock TM. Revised Starling equation and the glycocalyx model of transvascular fluid exchange: an improved paradigm for prescribing intravenous fluid therapy. *Br J Anaesth* 2012;108:384-394.

6. Adamik KN, Yozova ID. Starch Wars-New Episodes of the Saga. Changes in Regulations on Hydroxyethyl. Starch in the European Union. *Front Vet Sci* 2018;5:336.

7. Brunkhorst FM, Engel C, Bloos F, et al. Intensive insulin therapy and pentastarch resuscitation in severe sepsis. *N Engl J Med* 2008;358:125-139.

8. Myburgh JA, Finfer S, Bellomo R, et al. Hydroxyethyl starch or saline for fluid resuscitation in intensive care. *N Engl J Med* 2012;367:1901-1911.

9. Perner A, Haase N, Guttormsen AB, et al. Hydroxyethyl starch 130/0.42 versus Ringer's acetate in severe sepsis. *N Engl J Med* 2012;367:124-134.

10. Rhodes A, Evans LE, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016. *Intensive Care Med* 2017;43:304-377.

11. Navarro LH, Bloomstone JA, Auler JO, Jr., et al. Perioperative fluid therapy: a statement from the international Fluid Optimization Group. *Perioper Med* 2015;4:3.

12. Cohn LA, Kerl ME, Lenox CE, et al. Response of healthy dogs to infusions of human serum albumin. *Am J Vet Res* 2007;68:657-663.

13. Francis AH, Martin LG, Haldorson GJ, et al. Adverse reactions suggestive of type III hypersensitivity in six healthy dogs given human albumin. *J Am Vet Med Assoc* 2007;230:873-879.

14. Martin LG, Luther TY, Alperin DC, et al. Serum antibodies against human albumin in critically ill and healthy dogs. *J Am Vet Med Assoc* 2008;232:1004-1009.

15. Guidet B, Martinet O, Boulain T, et al. Assessment of hemodynamic efficacy and safety of 6% hydroxyethylstarch 130/0.4 vs. 0.9% NaCl fluid replacement in patients with severe sepsis: The CRYSTMAS study. *Crit Care* 2012;16:R94.

16. Fenger-Eriksen C, Tonnesen E, Ingerslev J, et al. Mechanisms of hydroxyethyl starch-induced dilutional coagulopathy. *J Thromb Haemost* 2009;7:1099-1105.

17. Toyoda D, Shinoda S, Kotake Y. Pros and cons of tetrastarch solution for critically ill patients. *J Intensive Care* 2014;2:23.

18. Treib J, Haass A, Pindur G, et al. Influence of low and medium molecular weight hydroxyethyl starch on platelets during a long-term hemodilution in patients with cerebrovascular diseases. *Arzneimittelforschung* 1996;46:1064-1066.

19. James MF. Place of the colloids in fluid resuscitation of the traumatized patient. *Curr Opin Anaesthesiol* 2012;25:248-252.
20. Chohan AS, Greene SA, Grubb TL, et al. Effects of 6% hetastarch (600/0.75) or lactated Ringer's solution on hemostatic variables and clinical bleeding in healthy dogs anesthetized for orthopedic surgery. *Vet Anaesth Analg* 2011;38:94-105.

21. Reuteler A, Axiak-Flammer S, Howard J, et al. Comparison of the effects of a balanced crystalloid-based and a saline-based tetrastarch solution on canine whole blood coagulation and platelet function. *J Vet Emerg Crit Care* 2017;27:23-34.

22. McBride D, Hosgood G, Raisis A, et al. Platelet closure time in anesthetized Greyhounds with hemorrhagic shock treated with hydroxyethyl starch 130/0.4 or 0.9% sodium chloride infusions. *J Vet Emerg Crit Care* 2016;26:509-515.

23. Wurlod VA, Howard J, Francey T, et al. Comparison of the in vitro effects of saline, hypertonic hydroxyethyl starch, hypertonic saline, and two forms of hydroxyethyl starch on whole blood coagulation and platelet function in dogs. *J Vet Emerg Crit Care* 2015;25:474-487.

24. Gauthier V, Holowaychuk MK, Kerr CL, et al. Effect of synthetic colloid administration on coagulation in healthy dogs and dogs with systemic inflammation. *J Vet Intern Med* 2015;29:276-285.

25. Diniz MS, Teixeira-Neto FJ, Goncalves DS, et al. Effects of 6% tetrastarch or lactated Ringer's solution on blood coagulation in hemorrhaged dogs. *J Vet Intern Med* 2018;32:1927-1933.

26. Fletcher DJ, Rozanski EA, Brainard BM, et al. Assessment of the relationships among coagulopathy, hyperfibrinolysis, plasma lactate, and protein C in dogs with spontaneous hemoperitoneum. *J Vet Emerg Crit Care* 2016;26:41-51.

27. Iannucci C, Howard J, Adamik K. Evaluation of coagulation impairment in dogs with spontaneous hemoperitoneum treated with hydroxyethyl starch pr polyinonic crystalloid (abstract). *J Vet Emerg Crit Care* 2018;27:S1-S29.

28. Wiedermann CJ, Joannidis M. Accumulation of hydroxyethyl starch in human and animal tissues: a systematic review. *Intensive Care Med* 2014;40:160-170.

29. Thompson WL, Fukushima T, Rutherford RB, et al. Intravascular persistence, tissue storage, and excretion of hydroxyethyl starch. *Surg Gynecol Obstet* 1970;131:965-972.

30. Cortellini S, Pelligand L, Syme H, et al. Neutrophil Gelatinase-Associated Lipocalin in Dogs With Sepsis Undergoing Emergency Laparotomy: A Prospective Case-Control Study. *J Vet Intern Med* 2015;29:1595-1602.

31. Hayes G, Benedicenti L, Mathews K. Retrospective cohort study on the incidence of acute kidney injury and death following hydroxyethyl starch (HES 10% 250/0.5/5:1) administration in dogs (2007-2010). *J Vet Emerg Crit Care* 2015.

32. Yozova ID, Howard J, Adamik KN. Retrospective evaluation of the effects of administration of tetrastarch (hydroxyethyl starch 130/0.4) on plasma creatinine concentration in dogs (2010-2013): 201 dogs. *J Vet Emerg Crit Care* 2016;26:568-577.

33. Chappell D, Jacob M, Becker BF, et al. [Expedition glycocalyx. A newly discovered "Great Barrier Reef"). *Anaesthesist* 2008;57:959-969.

34. Rehm M, Bruegger D, Christ F, et al. Shedding of the endothelial glycocalyx in patients undergoing major vascular surgery with global and regional ischemia. *Circulation* 2007;116:1896-1906.

35. Berg S, Golster M, Lisander B. Albumin extravasation and tissue washout of hyaluronan after plasma volume expansion with crystalloid or hypooncotic colloid solutions. *Acta Anaesthesiol Scand* 2002;46:166-172.
36. Smart L, Boyd CJ, Claus MA, et al. Large-Volume Crystalloid Fluid Is Associated with Increased Hyaluronan Shedding and Inflammation in a Canine Hemorrhagic Shock Model. *Inflammation* 2018;41:1515-1523.

37. Rehm M, Haller M, Orth V, et al. Changes in blood volume and hematocrit during acute preoperative volume loading with 5% albumin or 6% hetastarch solutions in patients before radical hysterectomy. *Anesthesiology* 2001;95:849-856.

38. Silverstein D, Aldrich J, Haskins C, et al. Assessment of changes in blood volume in response to resuscitative fluid administration in dogs *J Vet Emerg Crit Care (San Antonio)* 2005;15:185-192.

39. McBride D, Raisis AL, Hosgood G, et al. Hydroxyethyl starch 130/0.4 compared with 0.9% NaCl administered to greyhounds with haemorrhagic shock. *Vet Anaesth Analg* 2017;44:444-451.

40. Gauthier V, Holowaychuk MK, Kerr CL, et al. Effect of synthetic colloid administration on hemodynamic and laboratory variables in healthy dogs and dogs with systemic inflammation. *J Vet Emerg Crit Care*; 24:251-258.

41. Finfer S, Myburgh J, Bellomo R. Intravenous fluid therapy in critically ill adults. *Nat Rev Nephrol* 2018;14:541-557.

42. Cavanagh AA, Sullivan LA, Hansen BD. Retrospective evaluation of fluid overload and relationship to outcome in critically ill dogs. *J Vet Emerg Crit Care* 2016;26:578-586.

43. Hahn RG. Why crystalloids will do the job in the operating room. *Anaesthesiol Intensive Ther* 2014;46:342-349.

44. Annane D, Siami S, Jaber S, et al. Effects of fluid resuscitation with colloids vs crystalloids on mortality in critically ill patients presenting with hypovolemic shock: the CRISTAL randomized trial. *JAMA* 2013;310:1809-1817.

45. Dickenmann M, Oettl T, Mihatsch MJ. Osmotic nephrosis: acute kidney injury with accumulation of proximal tubular lysosomes due to administration of exogenous solutes. *Am J Kidney Dis* 2008;51:491-503.

46. Joosten A, Delaporte A, Ickx B, et al. Crystalloid versus Colloid for Intraoperative Goal-directed Fluid Therapy Using a Closed-loop System: A Randomized, Double-blinded, Controlled Trial in Major Abdominal Surgery. *Anesthesiology* 2018;128:55-66.

47. Pagel JI, Rehm M, Kammerer T, et al. Hydroxyethyl Starch 130/0.4 and Its Impact on Perioperative Outcome: A Propensity Score Matched Controlled Observation Study. *Anesth Analg* 2018;126:1949-1956.

48. Joosten A, Delaporte A, Mortier J, et al. Long-term Impact of Crystalloid versus Colloid Solutions on Renal Function and Disability-free Survival after Major Abdominal Surgery. *Anesthesiology* 2019;130:227-236.

49. Sigrist NE, Kalin N, Dreyfus A. Changes in Serum Creatinine Concentration and Acute Kidney Injury (AKI) Grade in Dogs Treated with Hydroxyethyl Starch 130/0.4 From 2013 to 2015. *J Vet Intern Med* 2017;31:434-441.

50. Sigrist NE, Kalin N, Dreyfus A. Effects of Hydroxyethyl Starch 130/0.4 on Serum Creatinine Concentration and Development of Acute Kidney Injury in Nonazotemic Cats. *J Vet Intern Med* 2017;31:1749-1756.

51. Yozova ID, Howard J, Adamik KN. Retrospective evaluation of the effects of administration of tetrastarch (hydroxyethyl starch 130/0.4) on plasma creatinine concentration in dogs (2010-2013): 201 dogs. *J Vet Emerg Crit Care* 2016;26:568-577.
52. Yozova ID, Howard J, Adamik KN. Effect of tetrastarch (hydroxyethyl starch 130/0.4) on plasma creatinine concentration in cats: a retrospective analysis (2010-2015). *J Feline Med Surg* 2017;19:1073-1079.

53. Boyd CJ, Claus MA, Raisis AL, et al. Evaluation of biomarkers of kidney injury following 4% succinylated gelatin and 6% hydroxyethyl starch 130/0.4 administration in a canine hemorrhagic shock model. *J Vet Emerg Crit Care* 2019 (Early view)

54. Diniz MS, Teixeira-Neto FJ, Celeita-Rodriguez N, et al. Effects of 6% Tetrastarch and Lactated Ringer's Solution on Extravascular Lung Water and Markers of Acute Renal Injury in Hemorrhaged, Isoflurane-Anesthetized Healthy Dogs. *J Vet Intern Med* 2018;32:712-721.

55. Boyd CJ, Claus MA, Raisis AL, et al. Hypocoagulability and Platelet Dysfunction Are Exacerbated by Synthetic Colloids in a Canine Hemorrhagic Shock Model. *Front Vet Sci* 2018;5:279.
# CLINICAL NUTRITION IN THE INTENSIVE CARE UNIT

Hanna-Liis Lepp

In my lecture I hope to give an overview of the goals of clinical nutrition in the ICU and how to reach them. I hope to touch this topic through evidence of targets and practice in the light of the new European Society for Clinical Nutrition and Metabolism ICU Nutrition Guideline as well as the experience of team work of North Estonia Medical Centre Nutrition Team!
# DECONTAMINATE: APPROACH TO TOXICOLOGICAL EMERGENCIES

Kenichiro Yagi, MS, RVT, VTS (ECC, SAIM)

Cornell University, Ithaca, NY, United States

Animal exposure to toxic substances is one of the common forms of emergencies presenting at a veterinary practice. The 2012 Annual Report of the American Association of Poison Control Centers (AAPCC) included 66,440 reports of non-human toxic exposures, of which 90.43% were dogs, and 8.49% were cats. In 2013, the American Society of Prevention of Cruelty to Animals (ASPCA) Poison Control Center handled approximately 180,000 possible toxin exposure cases. The top 10 exposures included prescription human medication, insecticides, over-the-counter human medication, household products, people food, veterinary products and medications, chocolate, rodenticides, plants, and lawn or garden products. Toxic exposures are predominantly through ingestion, though dermal, ocular, and inhalant contacts are some other forms seen. Many of these exposure require swift intervention, decontamination, and supportive care until the patient is no longer at risk of detrimental effects of the toxins.

## At Home Intervention

First notice of an animal being exposed to a toxin is typically communicated through a phone call to the veterinary practice with the owner seeking advice. Advice given to the owner requires vital information to be collected swiftly and a judgment made on further treatment. Information on the species, breed, age, gender, and body weight should be obtained as one of the first pieces of information. Obtaining of the body weight from a recent visit and considering the likelihood of significant change (growth, disease), and owner estimates should be considered with the possibility of inaccuracy. Information regarding the toxin exposure including the type of potential toxin, amount exposed to, the degree of certainty of exposure, estimated amount of time since the exposure, and any information gained from poison control advice lines (if obtained) is valuable in making a judgment. One of the main purposes of the phone conversation is to establish whether there is a life threatening problem occurring with the patient. The mentation and level of consciousness of the patient is an important indicator of stability. Animals with no impairment in cerebral perfusion and oxygen delivery will be alert and responsive to owner cues. The patient may be obtunded, having a slowed or decreased response to stimuli, indicating some compromise. If the patient is stuporous, or only responsive when providing noxious stimulus, this indicates even further compromise to brain function. If a patient is comatose, or unresponsive to any stimuli, the compromise is severe. Questions directed at determining respiratory effort should also be considered, as specific toxins of vomiting may lead to respiratory compromise. Patients with altered mentation and respiratory distress require immediate medical attention.

While appropriate medical treatment at the veterinary practice is advocated, at home intervention may be necessary if the trip to the veterinarian is expected to be longer than allowable time for interventions before the toxin takes effect (general allowable time is within one hour, though certain substances may be shorter or longer), and ingestion was witnessed or virtually certain. Induction of emesis at home may be warranted, though care should be taken to make sure no contraindications of emesis exist. Emesis should not be suggested in patients that have altered mentation, respiratory distress, compromise to normal protection of the airway (laryngeal or musculoskeletal disease), or
ingested caustic substances. In the case of ingestion of caustic substances, dilution with large amounts of water or milk prior to heading to see the veterinarian is suggested.

In case inducing emesis at home is necessary, options include syrup of ipecac, table salt, and 3% hydrogen peroxide. Syrup of ipecac stimulates receptors in the stomach and the chemoreceptor trigger zone in the posterior medulla, inducing vomiting. However, side effects such as prolonged vomiting and diarrhoea, lethargy, fever, and irritability is seen in humans, cautioning use. Recommended dose is 1-2mL per pound in dogs, and 3.3mL per pound in cats, and it may be justifiable to use if there is no other option available to prevent gastric absorption (activated charcoal) and a delay in treatment is expected otherwise. Salt and hydrogen peroxide stimulate the central nervous system through neurons in the pharyngeal and gastric areas, causing nausea and emesis. Table salt, while may be recommended by some sources, can be very harmful by causing electrolyte disturbances (hypernatraemia) leading to life-threatening harm, and is not recommended. Hydrogen peroxide can cause mucosal erosion leading to gastrointestinal ulceration, and should be used with caution. 1mL per pound up to a maximum of 45mL (3 tablespoons or 9 teaspoons) even in the largest dogs is the recommended dose.

If vomiting does not occur readily within 15 minutes, repeat doses of the above emetics may increase the chances of emesis occurring. However, the additional time required to administer the additional dose and wait for it to take effect may be counterproductive as it causes delays in medical intervention by the veterinarian. Instructing owners to induce emesis in a manner that is easy to collect the vomitus for examination by the veterinary staff is recommended. Once the attempt to induce emesis has been performed, the animal should be brought to a proper medical facility. Some toxins may induce seizures, tremors, hyperactivity, or altered mental states in the animal and precautions in preventing trauma to the patient and the owner during transport are important.

## Medical Intervention at the Veterinary Facility

Medical attention to the patient presenting for intoxication should be directed at patient stabilization, control of neurologic or haemorrhagic symptoms, correction of any metabolic derangements, decontamination, and any supportive care needed.

## Patient Stabilization

Patient stabilization includes assessment of the patient's airway patency and ability to protect their airway. Neuromuscular paralysis or paresis, severe respiratory distress, and respiratory arrest is an indication for endotracheal intubation (anaesthesia may be required) to secure the airway. A cuffed endotracheal tube is recommended. If significant respiratory signs are present, monitoring of oxygenation and ventilation through pulse oximetry, capnography, or arterial blood gas analysis is helpful. If oxygenation or ventilation is seen to be inadequate, supplementation with oxygen or assistance in ventilation through manual or mechanical positive pressure ventilation (PPV) may be necessary. The degree of oxygen supplementation and PPV should be moderated to allow for normal oxygenation (SpO2 of 95-98% or PaO2 of 80-100mmHg), and slightly higher than normal PaCO2 (50-60mmHg). The higher CO2 level is permissible from an acid-base standpoint, and will also continue to stimulate the respiratory drive of the patient.
The patient's cardiovascular status should also be assessed through the evaluation of forward perfusion parameters, including mentation, mucous membrane colour, capillary refill time, heart rate, pulse quality, and core to extremity temperature variance. The intravascular volume status of an intoxicated patient is variable depending on the symptoms and the time elapsed since exposure. Hypovolaemic or dehydrated patients will require fluid resuscitation and replacement of deficits. In the case of vitamin K antagonism, plasma would be a part of the treatment plan, and the patient may even require red cells if sufficient bleeding has occurred. Electrolyte abnormalities should be considered for the choice of fluids as well. Most electrolyte imbalances can be corrected with fluid therapy and supplementation. Toxins that produce cardiotoxic effects may alter cardiac rhythm and function. An ECG may be warranted for further evaluation. Drugs aimed at providing cardiovascular support may be required if fluid therapy alone is not adequate in supporting adequate cardiac output or cardiac dysfunction is present. Dobutamine is used as an inotropic agent intended to increase cardiac contractility. Dopamine, vasopressin, norepinephrine, are all vasopressors which can cause vasoconstriction creating better systemic vascular resistance and blood pressure. Epinephrine can be used as both an alpha and beta adrenergic agonist causing an increase in cardiac output and systemic vascular resistance. However, sympathomimetics (dopamine, norepinephrine, and epinephrine) are contraindicated in use with methylxanthine (caffeine, throbromine) toxicities, inducing severe cardiac arrhythmias. Toxins causing severe hypertension will benefit from the use of vasodilators such as hydralazine, amlodipine, and nitroprusside, causing reduction of systemic vascular resistance. Toxins altering oxygen carrying capacity through alteration of haemoglobin or red blood cell levels can cause significantly reduced oxygen delivery and tissue hypoxia. In the case of impaired haemoglobin function, oxygen supplementation, and in some cases transfusions are necessary. Reduced red cell mass will benefit from red cell transfusions.

As these immediately life threatening factors are controlled, any neurologic symptoms brought on by the intoxication need to be treated. Many toxins cause seizures and muscle tremors when allowed to persist lead to hyperthermia and damage to vital tissues and organs, coagulopathies, and a multitude of sequelae leading to an animal's demise. Anticonvulsants and muscle relaxants may be necessary to control these neurologic signs as decontamination takes place. Benzodiazepines such as diazepam and midazolam are commonly used anticonvulsants. Barbiturates such as pentobarbital and phenobarbital are also used, with alternatives such as levetiracetam being used more frequently. Propofol may be used to control muscle movement, though electrical activity within the brain may not cease with its use, and electroencephalography is required to determine cessation of seizure activity. Intoxication with tremorgenic toxins can be treated with muscle relaxants, with methocarbamol being the primary agent used.

## Decontamination

Regardless of the toxin the animal is exposed to, is, prevention of further exposure is necessary. Various methods of decontamination are employed depending on the route of exposure and elimination of the toxin.

Ocular exposure should be decontaminated through irritation with copious quantity of saline or water, to wash away and dilute out the toxin in question to prevent further exposure. Care should be taken to prevent prolonged application of direct pressure on the globe with pressurized fluids, accomplished
by irrigating at an angle more parallel with the globe surface. Irrigation may be possible at home, though thorough treatment may require sedation or anaesthesia to accomplish.

In the case of dermal exposure to toxins, care should be taken for the owner and medical personnel to protect themselves from exposure through second-hand contact through transportation or treatment. Toxic exposure can occur transdermally, or through ingestion as the animal tries to clean their body and ingestion should be prevented. For long-haired individuals, shaving the coat off may be a more effective and efficient way to remove contamination from the fur than to wash it off. Using a mild soap and detergent may be adequate to remove most toxic substances, though oily substances will require degreasing detergent used for strong hand cleaning or dish washing to eliminate. Care should be taken to prevent hypothermia in patients from the bathing. Dermal exposure to caustic chemicals requires special care. Copious flushing and gentle cleaning is necessary to prevent further traumatization while removing the toxin.

Most toxic exposures, however, are through the gastrointestinal tract by ingestion. The benefit of induction of emesis will depend on various factors. Similar to at home emesis, patients at risk of aspiration because of altered mentation, neurological dysfunction, or pre-existing conditions that prevent protection of the airway or ingested caustic substances should not have emesis induced. Otherwise, recovery of gastric contents are greater when emesis is induced closer to the time of ingestion (mean of 49% if induced within 11 to 30 minutes post ingestion). Emesis is worth inducing within 60 minutes from ingestion, with induction beyond more than 4 hours post ingestion having very little value.

Apomorphine, directly stimulating the chemoreceptor trigger zone, induces vomiting in animals. It is used primarily in dogs as it seems effective in swiftly inducing emesis. Apomorphine is given at 0.02 to 0.04mg/kg IV or IM, or topically as a tablet in the subconjunctival sac. Vomiting typically occurs within minutes, with repeat doses having mixed results in inducing further emesis. If any negative side effects are seen, naloxone (0.01 to 0.04mg/kg IV) may be used to reverse the opioid. Patients with metaldehyde toxicity can have CNS excitation through administration of apomorphine, and should have a different method utilized. Xylazine is an alpha-2 agonist sometimes used at 0.1mg/kg IV in cats (and less commonly dogs) as an antiemetic, having limited reported success rates (~60%). Other drug combinations such as rapid injections of cefazolin, hydromorphone and midazolam combinations, or dexmedetomidine in cats have been used with limited success.

Gastric lavage, the act of irrigating the stomach with water to dilute or wash out the toxin, may be considered in some cases. The patient is placed under anaesthesia, a cuffed endotracheal tube placed, and a gastric tube inserted into the stomach. The patient is placed at a slight decline (20 degrees) towards the head to prevent any gastric content to flow into the airway, though too much of a decline will reduce patient tidal volume by pressing on the diaphragm. Care should be taken to prevent overdistension of the stomach, and saline should be used in smaller patients to alleviate electrolyte losses through the lavage. External, manual manipulation of the stomach is performed to dislodge any toxins on the gastric mucosa. Copious amount and repeat lavaging is used. The amount of gastric content recovered through gastric lavages are variable and minimal compared to emesis (29-38% when performed within 15-20 minutes of ingestion and 8.6-13% if longer than 60 minutes), making advocating for this technique in the majority of cases difficult. Gastric lavages can be beneficial when
the ingested material is prone to causing clumps or toxins that delay gastric emptying, which may stay in the stomach longer than typical material.

Whole bowel irrigation is a technique used to clear the intestines of their content by administration of a polyethylene glycol electrolyte solution through a nasogastric tube. This technique is indicated in patients that have ingested sustained-release or enteric coated forms of medication which require additional effort in eliminating the effects of. Studies show a 68.9% elimination rate in dogs. The rate of solution required for this technique is quite high, at 500mL/hr, and may require administration of an antiemetic or prokinetic to allow for administration without induction of emesis. A 50% reduced rate may be necessary to prevent vomiting. Whole bowel irrigation is contraindicated in patients with gastrointestinal compromise (perforation, ileus, haemorrhage), haemodynamic instability, uncontrolled vomiting, or unprotected airway. Effectiveness of activated charcoal therapy is also reduced through concurrent use of whole bowel irrigation.

Ion exchange compounds such as cholestryramine and activated charcoal are administered to bind the toxin, removing it from the absorbable pool. These compounds especially are useful in treatment for toxins that undergo enterohepatic recirculation. Enterohepatic recirculation is the process of chemicals being excreted out by the liver into the bile being reabsorbed by the enterocytes back into the liver, prolonging systemic circulation of the chemical. Activated charcoal is very commonly used as an adsorbent, preventing absorption of the toxin. Activated charcoal reaches equilibrium with chemicals in the environment within 30 minutes, at which point some adsorption may occur. This is one of the reasons administration with a cathartic is advocated, to shorten gastrointestinal transit time. Recommended dosage of activated charcoal is 2 to 5g/kg (refer to product label for accurate dosing). Charcoal has the disadvantage of not being able to adsorb ionized toxins, and preventing endoscopic viewing of intestinal contents (62 hours for intestines to clear up).

Cathartics, such as sorbitol, are commonly administered with, or included in activated charcoal solutions to shorten gastric transit time. Reduction of transit time allows for less time for absorption to occur, and promotes excretion. Osmotic cathartics will promote movement of water into the lumen of the intestines increasing the fluid volume of the bowel content. Osmotic cathartics can be saline based, made of sodium and magnesium containing solution leading to higher osmolarity, or saccharide based (sorbitol). Repeated doses of cathartics are dangerous, as they can cause vomiting, nausea, dehydration, and even hypotension due to fluid depletion. Cathartics are often not very effective when administered alone. Cathartics are often combined with activated charcoal to provide a synergistic effect.

Diuresis, or increased urination, can be induced through administration of intravenous fluids and diuretics, increasing elimination of the toxin through the urine. Diuretics such as furosemide and mannitol are frequently used. The strategy is most useful in toxins that show a high degree of renal excretion (bromide, lithium, amphetamine, phenobarbital, and salicylate), while benefits may not be seen as much with protein bound toxins. Care must be taken to prevent fluid overload and electrolyte abnormalities, as high volume fluid administration can lead to hyponatraemia, hypokalaemia, pulmonary oedema, and cerebral oedema if not closely monitored. Patients that are anuric or oliguric whether from the toxin or pre-existing disease, are at higher risk of complications.
Ion trapping is a technique used to allow for further excretion of toxins through the urine by "trapping" the toxins in its ionic form to prevent reabsorption through the kidneys. Ionized molecules less readily diffuses through cellular membranes made of lipids. Trapping of weak acids and bases are easier to accomplish. Ion trapping is useful when the toxin is excreted predominantly through the urine, is a weak electrolyte, and is distributed to the extra-cellular space and non-protein bound. Ion trapping can be accomplished through acidifying the urine through administration of ammonium chloride or alkalinizing the urine by administration of sodium bicarbonate. Acidifying may be useful for treatment of amphetamines and phencyclidines. Ion trapping requires frequent monitoring of urine pH and blood pH to prevent detrimental acidosis or alkalosis, and may alter metabolism and excretion of other drugs.

Lipid emulsions, typically used for parenteral nutrition, have been more recently used for treatment of toxicities. Lipid emulsions consist of triglycerides and phospholipids, which can solubilize lipophilic chemicals (ivermectin, pyrethrins, permethrin, ionophores, marijuana) and make them unavailable for binding to the site of action. Each compound has a differing degree of lipophilic nature, which the effectiveness will depend on.

Physical removal of the source of the toxin through gastrotomy may be necessary if other options of decontamination are not expected to be fruitful. Iron tablets, for example, are known to adhere to the gastric mucosa and are difficult to remove without manually removing them. For some toxins, placement of a urinary catheter to keep the bladder empty is warranted for the prevention of reabsorption of metabolites across the bladder wall (methylxanthines, for example).

There are many considerations to be made in successful decontamination and recovery of a patient exposed to toxins. The appropriate method and giving the highest chance of success requires knowledge of options available and an understanding of the types and pharmacology of the toxins the patient is exposed to. We are often faced with situations where we do not know what the patient has been exposed to and are forced to treat based on suspicions due to symptoms seen, creating a level of difficulty in appropriate decontamination.
## HOW TO: PLACE AND MAINTAIN CHEST DRAINS

Tiago Abreu, RVN, NCert(PracTec), CertVN(ECC)

Hospital Veterinário do Bom Jesus/ Banco de Sangue Animal

Chest drains or thoracic drains/chest tubes/thoracostomy drains/tubes are drains that are used to remove any air (pneumothorax) or fluid (pleural effusion) that builds up in the pleural space due to variable reasons¹,³. Thoracostomy tubes are indicated in cases of recurrent pneumothorax, tension pneumothorax, pyothorax, rapidly forming pleural effusion and post-operative management of thoracotomy patients¹.

The placement of these tubes can be a life-saving intervention especially if this evacuation cannot be performed by thoracocentesis or if the production rate is too high³. If a thoracocentesis has to be performed more than 3 times in 12-24 hours, then a chest drain should be placed³. They allow either frequent intermittent evacuation of the pleural space or continuous evacuation if connected to a continuous suction device. As well as draining pleural effusion or pneumothorax, these tubes can be used to perform pleurodesis or administration of local or regional analgesia. Pleurodesis consists of the delivery of a substance (whole blood or chemotherapeutic drug) via the chest drain into the pleural space with the intent of obliterating the space, promoting adhesion of the pleural membranes³. Thoracostomy tube placement is contraindicated in patients with coagulopathies¹.

There are three different types of chest drains: trocar drains, small bore wire guided drains or red rubber catheters³. Trocar drains are stiffer, less prone to kinking but cause more discomfort to the patient during placement, and so a general anaesthetic is required. Small bore wire guided drains are placed using the Seldinger technique. These are the most commonly placed drains as their smaller bore causes less discomfort to the patient, but still, a general anaesthetic can be performed. Sterile red rubber catheters are used if no other options are available. Fenestrations can be made into the tube to improve its draining capacity³.

In order to place any of these tubes it is necessary to know the technique very well and to be comfortable with it. As well as knowing the technique, all the material should be prepared beforehand.

### List of required material:

* Chosen chest tube (size comparable to the diameter of the mainstem bronchi)

* 14-16 Fr for small dogs/cats

* 24-26 Fr for large dogs

* Christmas tree connector

* Tubing with Luer Lock

* Non collapsing extension set

* 3-way tap

* Scalpel blades

* Haemostats, scissors, needle holders

* Sterile swabs
* Tube clamp

* Bandage material³

Regardless of the chosen tube type and because it is a painful procedure, a general anaesthetic/sedation should be performed. If a large bore trocar tube is chosen, the patient's airway should be secured with an endotracheal tube. The patient should never be ventilated during the insertion or advancement of the trocar, minimising the risks of lung puncture³. Pre-oxygenation is advised prior to induction¹. Once anaesthetised, the patient should be placed in lateral recumbency, have the lateral aspect of the chest clipped between the 6th -10th intercostal spaces, and then have this area aseptically prepared. Intercostal block analgesia can be administered, making the insertion of the chest tube less painful³.

If a red rubber tube or trocar is the chosen tube, after aseptic preparation of the thoracic wall, an assistant pulls the skin cranially. The surgeon placing the tube can choose between two different techniques:

a) Full-thickness incision

I. Make a full thickness incision at the 10th -11th intercostal space

II. Advance tube through to the level of the 7th/8th intercostal space³

b) Partial thickness intercostal incision

I. Make a partial thickness intercostal incision

II. Bluntly dissect with haemostat forceps

III. Holding the distal end of the tube with the non-dominant hand, start advancing, avoiding over-advancement³.

Once in, the tube should be reoriented to advance in a craniocentral direction and the assistant releases the skin, creating a tunnel for the tube. The tube should then be connected to a 3-way tap and using a syringe, the chest should be drained. A chest radiograph should be performed to confirm position. A purse string suture is placed around the base of the tube, and the tube secured with a Chinese finger trap suture³.

If a wire guided tube is chosen, once the thoracic wall is prepared, a skin incision is made between the 7th -9th intercostal spaces and an over-the-needle catheter is inserted into pleural space. The stylet is then removed and the guidewire advanced through the catheter into the pleural space. The catheter is then removed allowing the chest drain to be advanced over the guidewire. As with trocar or red rubber tubes, a radiograph should be performed to confirm position and then the tube should be secured to the thoracic skin³.

These tubes require 24 hour supervision and should be handled in an aseptic manner, using gloves at all times¹,³. A bandage or some kind of barrier should be used to protect the incision site and tube and should be changed daily. An Elizabethan collar should be worn by the patient at all the times to avoid complications. The drain should always be clamped when not being drained in order to prevent the entry of air into the pleural space¹,³. The insertion site should be evaluated at least once daily for signs of subcutaneous emphysema, as well as for signs of inflammation or infection such as redness, pain, heat or swelling and/or purulent discharge¹. When manually draining a pneumothorax/pleural
effusion, an empty syringe should be connected to a 3-way tap which is connected to the chest tube¹.
The tube is then gently aspirated until negative pressure is obtained. Once this happens, the patient
should be repositioned to understand if the movement will allow any further drainage or not¹. An
analgesia plan should be decided and could include the administration of local anaesthetic into the
pleural space making drainage more comfortable³. Respiratory rate and effort should be monitored
and recorded to evaluate trends and assess frequently for any abnormalities.

Chest drains should be removed as soon as they are no longer needed. The decision to pull the tube should be based on the amount of fluid/air that is being drained. In a pneumothorax case, if no or minimum air is produced, the tube can be removed. In a pleural effusion case, the tube can be pulled out when the fluid production volume is low and is not causing respiratory distress to the patient³.

The placement of these tubes carries possible complications such as infection, haemorrhage, visceral injury, re-expansion pulmonary oedema, occlusion/kinking of tubing and patient interaction with tubing³.

References

1. Lombardi, R., Savino, E., & Waddell, L. S. (2012). Pleural space drainage. *Advanced Monitoring and Procedures for Small Animal Emergency and Critical Care*, 378-392. Aspinall, V. (Ed.). (2011). *The Complete Textbook of Veterinary Nursing*. Elsevier Health Sciences.

2. Dodd, L. (2014). Critical patient care (venous catheters, urinary catheters, drains). In *13th EVECCS Congress Proceedings*. EVECCS

3. Lynch, A., & Campos, S. (2018). Thoracostomy Tube Placement. *Textbook of Small Animal Emergency Medicine*, 1199-1201.
# HOW TO PLACE AND MANAGE A TRACHEOSTOMY TUBE

Gonçalo Babau, VN; CertVN(ECC); VetOeiras

## Introduction

Placement of a tracheostomy tube is a procedure considered as a lifesaving intervention. This technique allows air to bypass the glottis and nasal cavity to improve respiratory tract function. Appropriate management is essential.

Tracheostomy patients require constant monitoring while the tube is in place. Associated complications are common and may lead to death if they are unrecognized and untreated ⁴.

Tracheostomy is a common procedure performed in the emergency room (ER), therefore it is crucial that ER clinicians understand how to perform a tracheostomy urgently without needing to review the procedure in the event of an airway occlusion ⁵.

## Indications

Tracheostomy tube placement is indicated for potentially life-threatening upper airway obstructions (when orotracheal route is unavailable), oral or pharyngeal surgery or long-term positive pressure ventilation (PPV) in critically ill patients. With tracheostomy, accessing the trachea distal to the nose, mouth, pharynx and larynx allows oxygen flow to enter distal to obstructions and decreases the risk of damage to the oral cavity during long-term intubation¹.

Tracheostomy is also indicated for the following:

- preoperatively in patients with upper airway obstructions before definitive treatment is implemented (e.g., allowing referral or processing of biopsy specimens)

- transient soft tissue obstructions such as swelling after upper respiratory tract surgery, trauma, laryngeal/pharyngeal oedema or inflammation

- as part of elective surgery when orotracheal intubation is unavailable (e.g. when the patient is unable to open its mouth, or in oral or pharyngeal surgery ⁴.

## Contraindications

There are several contraindications to performing a temporary tracheostomy. These include coagulopathies (e.g. Vitamin K antagonist rodenticide intoxication), masses or tracheal obstruction distal to the recommended site of tracheostomy and tracheal collapse distal to the site of tracheostomy or previous tracheal stent placement ³.

## Tracheostomy tube selection

Several types of tracheostomy tubes are available. They can be cuffed or uncuffed and with or without an inner cannula. Placing a tube with or without a cuff depends on individual patient factors. To reduce the risk of tracheal damage, an uncuffed tube should be used or the tube cuff should keep deflated. Even on patients under PPV, uncuffed tubes may also be feasible. A removable inner cannula is considered desirable allowing for easy and effective tube maintenance. This can be briefly removed for cleaning whilst avoiding the risk of disrupting airway integrity. In the absence of an inner cannula,
the entire tracheostomy tube should be replaced at least every 24 hours to prevent occlusion with
accumulated secretions ¹.

The most appropriate tracheostomy tube size is debatable, but the larger the relative size of the tube to the trachea, the less air can flow around it in the event of tube obstruction, so patients with larger tubes should be more closely monitored. However if the upper airway tract obstruction is marked or complete, bypassing airflow will be minimal, meaning a larger tube will benefit the patient. Larger tubes may predispose to site damage.

With better airflow a less negative intrathoracic pressure is achieved during inspiration, consequently,
there is less risk of gastro-oesophageal reflux and regurgitation, which is believed to decrease the
aspiration risk ⁴. Extra tube length may help to avoid tube dislodgement. It is suggested to use the
largest internal diameter tube that will fit into the tracheal lumen without any effort, or as a rule of
thumb one that is approximately 75% of the internal tracheal diameter. Tubes vary according to their
material, external and internal diameters, length, and presence/absence of cuff. An uncuffed tube is
used, unless PPV is required, when a low-pressure cuffed tube is necessary. This tube requires special
care to avoid pressure necrosis on the internal tracheal mucosa ⁴.

Tracheostomy tubes can also be fenestrated to allow airflow through the upper airway if the external
opening is occluded. However, the utility in veterinary medicine is questionable and this kind of tube
cannot be used with PPV. If a tracheostomy tube is not available, an endotracheal tube can be
shortened and used as an effective substitute ⁶.

Equipment

In addition to the tracheostomy tube itself, essential equipment for performing a temporary
tracheostomy includes instruments for a surgical approach to the trachea, suture, and material to
secure the tube in place².

Essential equipment to perform a tracheostomy includes:

- Hair clippers

- Endotracheal or tracheostomy tube

- Skin preparation solutions (povidone iodine or chlorhexidine)

- Sterile drape

- Towel clamps

- Scalpel blades (10 and 15)

- Mosquito haemostats

- Scissors

- Needle drivers

- Suture scissors

- Small Gelpi retractors

- Umbilical tape

- 3/0 or 4/0 nonabsorbable suture

- 3/0 or 4/0 absorbable suture
## Technique

Tracheostomies can be percutaneous or surgical (transverse or vertical incision).

Percutaneous tracheostomy (Seldinger technique) is a good technique for emergent patients and can be done rapidly. A small transverse incision is made at the desired location for tube insertion. A small-gauge needle is inserted into the tracheal lumen, a guidewire is introduced via the needle into the lumen. Than a dilator is passed over the guidewire. The guidewire and dilator are then removed and the tube is secured in place ¹.

Advantages of this technique include smaller skin incisions, less tissue trauma and a lower incidence of complications².

Surgical tracheostomy, is best performed in a controlled manner with the patient under general anaesthesia and with an orotracheal tube placed. The animal is placed in dorsal recumbency with the neck extended for exposure the incision site. Surgical preparation of the ventral cervical region should be performed.

Several techniques for tracheostomies have been described, none of which have been shown to be superior with respect to functionality or complication rate². The two common surgical approaches for tracheostomy are transverse and vertical incisions.

### Transverse incision

In this approach the incision is made between the 3rd and 4th or 4th and 5th tracheal rings. The incision should be extended for no more than 50% of the tracheal circumference. Care should be taken to avoid left recurrent laryngeal nerve injury. To reduce tracheal irritation or inflammation, a small ellipse of cartilage adjacent to the incision can be made. Long loops of suture are placed around the tracheal rings adjacent to the incision to facilitate retraction of the trachea and future replacement of the tube after cleaning ¹.

### Vertical incision

A ventral midline vertical incision is made through 2nd to 4th tracheal rings. Long stay sutures may be placed encircling the cartilage rings lateral to the incision to aid in continued manipulation of the trachea and future tube replacement. Segmental lateral tracheal collapse may be a long-term complication of this procedure ¹.
<figure><img src="image_29.png" /><figcaption>**Figure 1.** Transverse incision tracheostomy</figcaption></figure>

<figure><img src="image_30.png" /><figcaption>**Figure 2.** Transverse incision tracheostomy</figcaption></figure>

## After care and management

Tracheostomy tubes are commonly associated with several complications but at the same time with a good outcome in most patients. Continuous monitoring is always required.

Major aims of tracheostomy tube management are preventing tube obstruction, facilitating removal of airway secretions and minimizing the risk of airway trauma or nosocomial pneumonia ⁶.

All staff working in ER should be trained in recognizing a tube occlusion or dislodgement ⁵.

## Suctioning Protocol

Care of the tracheostomy tube requires frequent monitoring and suctioning as necessary to remove mucous and blood clots that can cause tube obstruction. To humidify the tracheal mucosa and remove debris within the trachea and tracheostomy tube, instillation of sterile saline and a tracheostomy tube suction are performed at regularly scheduled intervals ³.

This procedure should be performed frequently to remove secretions and reduce the risk of tube occlusion.

- Preoxygenate the patient with 100% oxygen 3-5 minutes prior to suctioning

- Remove the inner cannula for cleaning.

- Humidify airway for 20 minutes before performing suctioning

- Insert a sterile suction catheter to the level of the carina and apply suction intermittently using a circular motion (no longer than 10 seconds)
- Repeat the suctioning 3 - 4 more times

- Administer 100% oxygen for 3 – 5 minutes after each suctioning episode.

- Replace the cleaned inner cannula

- Clean the incision site surrounding the tracheostomy tube and ensure that the tube is still in position⁶.

### Tracheostomy site care

Tracheostomy technique implies that a tube bypasses the normal defence mechanisms of the upper airway. Therefore, sterile technique must be used all times while caring for the tracheostomy site and the tracheostomy tube itself, in order to avoid iatrogenic nosocomial infection ³.

### Removal of the tracheostomy tube

When airway obstruction has resolved, the tracheostomy tube should be removed within 48 hours and the site should heal by second intention. Closing the skin increases the risk of subcutaneous emphysema⁵.

### Complications

There are several complications associated with temporary tracheostomy and correct management of the tube is essential. Possible complications include tube occlusion or dislodgment, subcutaneous emphysema, pneumothorax, aspiration of fluids and foreign bodies, pneumonia and incision site infection ⁶, damage to the laryngeal nerve, pneumomediastinum, tracheal collapse and some others.

### References

1. Fudge, M. (2009). Endotracheal Intubation And Tracheostomy. Ed D. Silverstein, *Small Animal Critical Care Medicine* (2nd ed.). Elsevier.

2. Lam, N. (2015). Small. Em L. Aronson, *Small Animal Surgical Emergencies* (pp. 263-269). Wiley Blackwell.

3. Mazzaferro, E. (2013). Temporary tracheostomy. *Topics in Compan An Med 28*, 74-78.

4. Nicholson, I., & Baines, S. (March de 2010). Indications, placement and management of tracheostomy tubes. *In Practice*, *32*, 104-113.

5. Rozanski, E. (2019). Airway Management. Ed K. Drobatz, K. Hopper, E. Rozanski, & D. Silverstein, *Textbook of Small Animal Emergency Medicine* (Vol. 2, pp. 1173-1176). New Jersey: Wiley Blackwell.

6. Silverstein, D. (2015). Small Animal Critical Care Medicine (2nd ed.). EUA: Elsevier.
HOW TO: PLACE AND MAINTAIN CENTRAL LINES

Tiago Abreu, RVN, NCert(PracTec), CertVN(ECC)

Hospital Veterinário do Bom Jesus/ Banco de Sangue Animal

Central line placement allows us to gain access to the vasculature in order to administer fluid therapy and medications, perform serial blood sampling, and monitor haemodynamic parameters. Careful vessel selection and catheter placement are of paramount importance. Central venous catheters (CVC) are most commonly inserted via the jugular vein, with the tip of the catheter sitting in the cranial vena cava. PICC (Peripherally Inserted Central Catheter) lines can be used, especially if there is a suspicion of increased intracranial pressure or where the access to the jugular vein is limited. In this case, long catheters are inserted through the medial or lateral saphenous veins and the tip sits in the caudal vena cava¹,².

When choosing the appropriate site, several factors should be taken into account, like the patient size and species, vein accessibility, physical barriers (wounds, fractures, neoplasia, neurologic insufficiencies), restraint requirements, patient temperament, haemodynamic stability, coagulation abnormalities (CVC may be contraindicated in hyper- or hypocoagulable states) and sources of contamination like urine, vomit, diarrhoea or faeces¹,².

Indications for CVC or PICC line placement include prolonged hospitalization, administration of hypertonic fluids or hyperosmolar medications, frequent blood sampling, delivery of total parenteral nutrition (TPN), central venous pressure (CVP) monitoring and when maintaining a peripheral catheter is expected to be challenging¹,².

There are several disadvantages in the use of a CVC/PICC line, like longer placement time, which increases the risk of infection, greater expense, patient discomfort during placement which requires the patient to be sedated/anaesthetised, longer length may make rapid fluid administration problematic and difficulty in monitoring for extravasation of fluid¹,².

The use of CVC should be avoided in cases where there is suspicion of thromboembolic disease, coagulopathy, increased intracranial pressure, respiratory disease (prolonged time for its placement could be an issue), immune mediated haemolytic anaemia and cervical disease/pain.

Several different types of catheters can be used for CVC/PICC lines, such as:

1. Long over-the-needle catheters are cheaper, available in various diameters and lengths, made of a stiff material which can cause discomfort, prone to kinking and as made of Teflon should be replaced every 72 hours¹,².

2. Through-the-needle catheters are longer than long over-the-needle, are available in various diameters and lengths, placement is faster, they can be placed in peripheral vein if the jugular cannot be used, they are cheaper and requires a bandage to secure them¹,².

3. Over-the-wire catheters are available in single or multi lumen. They are designed to stay in place for longer periods (soft, flexible and made of anti-thrombogenic material). Available in various lengths and diameters. Placement requires a longer procedure time, and they are more expensive¹,².
## Placement

The most commonly used CVC placement technique is the over-the-wire (Seldinger) technique. PICC lines may require through-the-needle techniques. A few steps are common to both techniques and are very important:

* Determine the appropriate length of CVC before scrubbing by measuring (tape measure) from the approximate site of insertion to where the tip of the catheter should lie. For jugular lines the tip should lie just outside the right atrium which usually approximates to the caudal border of the scapula when measuring.

* Prepare all equipment needed for CVC placement

* Attach patient to monitoring equipment

* The catheterisation site is clipped and surgical preparation performed

* Aseptic technique is essential and the operator and assistant should wear a gown, face mask and sterile gloves.

### Through-the-needle (Peel-away) catheter

- Insert the peel-away over-the-needle sheath into the vein

- Remove the needle, leaving the sheath in the vein

- Insert the catheter through the sheath into the vein

- Grasp and pull the sheath, peeling it up out of the vein, leaving the catheter in place

- Aspirate catheter and flush with 0.9% NaCl or heparinised Saline

- Suture at the anchor points and bandage²

### Through-the-needle catheter

- A plastic sleeve around the catheter prevents contamination during placement

- Once the catheter has been fed entirely into the vessel, the needle is backed out of the skin and a protective guard is snapped over the needle²

### Over-the-wire catheter (Seldinger technique)

**Material:**

1. Mayo stand or a table with sterile field

2. CVC Single or Multi-lumen (Multi-lumen preferably)

3. Sterile swabs

4. Suture material

5. Sterile NaCl 0.9% 100mL bag

6. Sterile syringes (5mL and 10 mL quantity depending on number of lumens x2)

7. Sterile needles (ideally 21G 5/8") equal to number of syringes

8. Intravenous catheters (size depending on the size of guide wire)

9. ECG monitor

10. Lidocaine 2% with 2mL syringe and 21-23G needle

11. Needle free valves for each lumen ³

## Placement

1. Ask assistant to open the required equipment in a sterile manner

2. Prepare syringes with sterile NaCl 0.9% (do not fill them completely as some available volume is required for aspiration of blood from CVC once it is in place)

3. Prepare CVC by attaching needle-free valves and pre-flushing the lumens with 0.9% NaCl and clamping them off immediately after flushing before the syringe is detached. Return catheter to
the pack

4. Drape the patient

5. Ask assistant to raise the vein and determine the venepuncture site

6. Use a peripheral intravenous catheter of an appropriate size, or the catheter supplied with the CVC pack for initial venepuncture (skin incision using a scalpel blade can be performed for ease)

7. Once catheter is placed in the jugular vein, remove the stylet, leaving the catheter in place and then introduce the guide wire. Use the J ending of the guide wire which should be retracted back into the sheath and then fed through the catheter into the vessel (at this point monitor patient for any changes on the ECG monitor as this might indicate introduction of the wire into the heart which can cause cardiac arrhythmias)

8. Once the guide wire is in, remove the catheter ensuring the guide wire is held at all times and that it does not move deeper into or completely out of the vessel

9. Once only the wire remains in the vessel, a dilator is fed over the wire and should be introduced into the vessel by a slight rotating motion. Some force might be required to pass through the tissues and the vessel wall

10. Remove dilator while holding the wire and ensuring it remains in the vessel

11. Remove the dilator and feed the CVC over the guide wire unclamping the distal (brown) lumen to allow free passage of the guide wire (the guide wire should always be held by operator or assistant and must be retracted out of the vessel enough to enable firm hold of it at the distal CVC lumen while introducing CVC into the vein)

12. Once the CVC is inserted to the pre-measured length the guide wire can be removed.

13. Attach sterile syringe preloaded with NaCl 0.9% and aspirate each lumen until blood is visible. If any air remains it should be aspirated into the syringe. Flush lumens until cleared of any remaining blood.

14. Secure the CVC in place by placing sutures through its wings.

15. Radiograph chest to confirm positioning. If the catheter is sitting within the right atrium or is not parallel to the vessel, it should be repositioned and reconfirmed. Inappropriate positioning of the CVC could lead to life threatening complications.

16. Place a sterile dressing (Allevyn adhesive for example, size depending on size of animal) over the insertion site, followed by padding such as Soffban, and conforming bandages respectively. Take care to keep bandages around the neck very loose to avoid restricting breathing.³

**Maintenance:**

Appropriate maintenance is of extreme importance and it is paramount that aseptic technique is used at all times:

**Catheter check**

- Flush unused ports with sterile saline (q8-12h)

- More frequent checks if any concerns or high rates of fluid therapy

- Check for swelling, if there is swelling cranial to the insertion site, the tape might be too tight or there might be oedema formation. If the swelling is caudal to the insertion site, fluid extravasation may have occurred.

- Check for signs of inflammation (pain, redness, malodour, discharge)

- If complications are noted when doing the catheter check:

- Record findings and inform clinician
- Consider removing the catheter if appropriate

- Consider sending the tip for culture and sensitivity

- Replace in another site if necessary

- The bandage should be removed and changed at least once daily as well as any dressing covering the incision port¹,²,³

## Blood collection

One of the ports should be reserved for blood collection only. The port should be swabbed with alcohol impregnated solution for 15 seconds allowing 15 seconds to dry³. Then, the line should be flushed with heparinised saline and 2-2.5ml of blood should be drawn and not discarded³. The samples can be collected and the amount of blood firstly drawn be re-introduced. The line should then be flushed with saline and the port swabbed again.

## Administration of medications/intravenous fluid therapy (IVFT)

One port should be dedicated to this purpose. The port should be swabbed with alcohol impregnated solution for 15 seconds allowing 15 seconds to dry³. The fluid line can then be connected or medication administered. In case of medication being administered, the used port should be flushed. The port should then be swabbed again².

## Total Parenteral Nutrition (TPN)

One port should be dedicated to this purpose even if patients are not on it. The port should be swabbed with alcohol impregnated solution for 15 seconds allowing 15 seconds to dry. Disconnection of the line from the port should be avoided as can increase the infection risk³.

## Central Venous Pressure (CVP)

Use the IVFT or blood collection port, swab port with alcohol impregnated solution for 15 seconds allowing 15 seconds to dry. Then, connect the CVP measurement tubing. After the measurement is performed, swab the port again²,³.

## Complications:

Complications may include displacement, extravasation of fluid or medication, phlebitis/ thrombophlebitis, infection, dislodgement/catheter embolism, air embolism or exsanguination¹,².

## References

* Adamantos, S., Alwood, A. (2015). Vascular access. In *BSAVA manual of canine and feline emergency and critical care* (pp. 8-17). BSAVA Library.

* Creedon, J. M. B., & Davis, H. (Eds.). (2012). *Advanced monitoring and procedures for small animal emergency and critical care*. John Wiley & Sons.

* Aspinall, V. (Ed.). (2011). *The Complete Textbook of Veterinary Nursing2: The Complete Textbook of Veterinary Nursing*. Elsevier Health Sciences.

* SOP folder from the ICU at the Royal (Dick) School of Veterinary Studies

* Dodd, L. (2014). Critical patient care (venous catheters, urinary catheters, drains). In *13th EVECCS Congress Proceedings*. EVECCS
# HOW TO: PLACE AND MAINTAIN ABDOMINAL DRAINS

Gonçalo Babau, VN; CertVNECC; VetOeiras

## 1. Introduction

Abdominal drains have the ability to continually remove fluid from the abdominal cavity. After surgery, even if peritoneal lavage and surgical suction have been performed, additional inflammatory fluid accumulates and cannot be reabsorbed by natural peritoneal drainage. In addition, inflammation reduces the effectiveness of both the peritoneum and omentum (Sturgeon, 2016). Therefore, placing an abdominal drain might be the best option to avoid fluid accumulation in the abdominal cavity.

The two main options for peritoneal drainage include open peritoneal drainage and closed suction drainage (Devey, 2013).

The traditional method of open peritoneal lavage might be detrimental to protein levels and requires continuous patient monitoring. The use of an active-suction drain instead of an open technique allows more accurate measurement of the drained fluid without further debilitating the patient and takes away the need for a surgical approach to close the coeliotomy site (Sturgeon, 2016).

## 2. Indications

Abdominal drains are often used in patients after surgical treatment of septic peritonitis as a method of evacuating peritoneal effusion and monitoring for evidence of ongoing infection or surgical site dehiscence. They can even be used after elective gastrointestinal surgery, especially in those patients with decreased wound healing capabilities. The most common causes of septic peritonitis are gastrointestinal perforation with food content leakage, abdominal trauma, necrotising pancreatitis, bile leakage, pancreatic, hepatic or splenic abscesses, rupture of pyometra or prostatic abcession (Culp & Holt, 2010; Goethem, 2015). Abdominal drainage may be required after the underlying disease has been treated, but there are no guidelines as to whether the abdomen should be left open or not after surgery, and the decision lies with the individual surgeon.

Thus, the main goals of abdominal drainage are:

- avoiding the accumulation of peritoneal fluid;

- avoiding secondary increased intra-abdominal pressure;

- removing bacterial contamination;

- monitoring fluid volume and characteristic changes that may predict infection or dehiscence.

## 3. Drain selection

Drains may be passive or active. Passive drains rely on gravity, capillary action, natural pressure gradients or overflow to control gas/fluid outflow. An example of a passive drain commonly used is a Penrose drain. Drain efficacy depends upon its exit position. Passive drains are more often used in wound management.

Active drains create and rely on negative pressure (suction) to promote outflow of gas or fluid.

The most commonly used tube for abdominal drainage is the Jackson-Pratt drain (Figure 1). The flat, white, silicone part is specifically designed to prevent occlusion of the fenestrations by abdominal structures (omentum).
<figure><img src="image_31.png" /><figcaption>Figure 1: Jackson-Pratt drain</figcaption></figure>

The ideal drain should be soft, comfortable for the patient, inert, radio-opaque and non-reactive (Lanz, 2011). Drains are typically made of latex, red rubber, polyethylene, polyvinyl chloride or silicone rubber. Polyethylene, polyvinyl chloride and silicone rubber are fairly inert (Goethem, 2015).

## 4. Technique

The two main options for peritoneal drainage include open peritoneal drainage and closed suction drainage (Devey, 2013). In cases where the source of contamination cannot be identified, contamination is severe or longstanding or the virulence of organisms is high, such as that seen with faecal contamination, open peritoneal drainage is advocated.

### 4.1 Open peritoneal drainage

Open peritoneal drainage is a process by which the linea alba and skin are left partially or completely open and covered with sterile dressings, which are changed at frequent intervals (Lanz).

Open peritoneal drainage was applied in human patients in response to persistently high morbidity and mortality rates associated with gross peritoneal contamination.

After complete the abdominal procedure, a portion of the abdominal incision is left open to drain, with the opening large enough to allow a gloved hand to be inserted (Fossum, 2012). This technique is accomplished by loose simple continuous monofilament suture closure of the linea alba. Falciform fat is normally excised and omentum can be removed, but potentiation of peritonitis has been suggested with partial omentectomy. For ease of postoperative management, closure of the caudal third of the linea alba is recommended. The cranial two thirds of the wound are left opened and this is covered with sterile bandages. Urinary catheterization with a closed collection system is recommended to prevent urine contamination of the bandage (Fossum, 2012; Kirby, 2012).

The main advantages of open peritoneal drainage are that it allows unimpeded drainage of fluid and exudate from the peritoneal cavity, effective removal of excessive amounts of fluid, easier access for re-exploration of the peritoneal cavity, creation of an environment unfavourable to anaerobic bacteria, increased efficiency of removal of bacteria, foreign material and inflammatory mediators from the peritoneal cavity, improves metabolic status and decreases abdominal adhesion formation (Culp & Holt, 2010; Lanz, 2011).

Disadvantages and/or complications of this technique are protein loss, electrolyte abnormalities, fluid loss, evisceration risk, adhesion of the abdominal viscera to the bandages, contamination of the abdominal cavity with cutaneous organisms. Apart from these, there is always a high risk of nosocomial infections and all efforts should be made to avoid this (Culp & Holt, 2010; Kirby, 2012).
## 4.2 Closed suction drainage

A variety of different drain materials and types have been experimentally and clinically used in patients with septic peritonitis (Kirby, 2012).

Closed gravity dependent drainage is reported to be ineffective because of the creation of a vacuum. Sump-tube drainage provides an air vent to overcome this vacuum phenomenon but also allows airborne bacteria access to peritoneal cavity. Filters have been added to sump drains to eliminate this airborne route of contamination (Kirby, 2012).

At surgery, a drain, e.g. a Jackson-Pratt drain, is placed into the abdomen before closure. Small dogs and cats will only need one drain placed between the liver and diaphragm whereas large dogs may require a second drain into the caudal ventral abdomen. Drain(s) exit(s) through the body wall via an incision and is/are sutured to the skin of the abdominal wall with a roman sandal suture. The abdomen is routinely closed and the suction reservoir bulb is attached to the tubing and a vacuum applied. Then, a sterile protected bandage is placed around the tube-skin interface. The bulb should always be handled and emptied using aseptic technique and the volume of fluid recorded. The drain is removed by cutting the suture and applying gentle traction (Fossum, 2012).

The closed suction technique is much more effective, allowing accurate measurement of the amount of fluid drained and minimizing morbidity.

The main disadvantage of this technique is that drains may become occluded. Fluid that is more serous in nature may be best managed by closed suction drainage, whereas fluids that are exudative in nature may occlude the drain. In this case, open peritoneal drainage is a better option (Fossum, 2012). Other disadvantages include ineffective drainage of the entire peritoneal cavity and nosocomial bacterial contamination of the peritoneal cavity even when a filter is added (Kirby, 2012).

## 5. After care and maintenance

Drains should be handled in a strict aseptic manner and all drains should be protected by a bandage (Fossum, 2012).

With open abdominal drainage, the bandage should be changed once daily or more frequently as necessary to prevent moist bacterial strike-through. Omental adhesions to the open wound can be gently disrupted with a sterile gloved finger to facilitate drainage if needed. The bandage should be weighed at each dressing change to quantify fluid loss in the peritoneal effusion (Kirby, 2012).

When a drain is placed, the drain, tubing and skin exit site should be kept clean and inspected several times daily for evidence of contamination or damage to the drain system. The frequency of emptying the reservoir will depend on the volume of abdominal effusion produced; highly effusive peritonitis patients could require drainage every 2-4 hours depending on the size of the reservoir (Clarke & Winkler, 2017).

Proper hygiene is essential for drain handling, including gloves and preventing contact with the reservoir and container being used for fluid collection and quantification (Clarke & Winkler, 2017).
## 5.1 Removal of drain

Retrospective studies report a duration of open abdominal drainage from 1 to 9 days, with a mean duration of 4 days. However, duration of open peritoneal drainage up to 14 days has been described (Kirby, 2012).

When a drain is placed, it should be removed as soon as possible in order to reduce the risk of bacterial colonization. The longer it is kept the higher the risk. The decision to remove the drain is based on the quantity and type of drained fluid. The decision for removal is made when the amount of fluid decreases and reaches a plateau, while turning increasingly serosanguineous. Serial cytology can be performed to evaluate the characteristics of the fluid (Goethem, 2015; Lanz, 2011).

Drains should be left in place until the fluid amount being produced is within the physiologic limits (1-2mL/kg/day) and its cytology shows no signs of active inflammation or infection (Devey, 2013).

## 6. Conclusions

Based on the current human surgical literature, definitive need for abdominal drainage has not been proven and may contribute to longer hospital stays and postoperative complications (Clarke & Winkler, 2017). While similar conclusions cannot be drawn from the current veterinary literature, closed suction abdominal drains appear safe for the management of septic peritonitis but have limited value to predict infection or dehiscence (Clarke & Winkler, 2017).

## References

* Clarke, D., & Winkler, K. (2017). Closed Abdominal Drains. *International Veterinary Emergency and Critical Care Symposium*. Nashville, TN.

* Culp, W., & Holt, D. (October de 2010). Septic Peritonitis. (Vetelearn, Ed.) *Septic Peritonitis*.

* Devey, J. (19 de Jul de 2013). Surgical Considerations in the Emergent Small Animal Patient. pp. 899-914.

* Fossum, T. (2012). Surgery of the abdominal cavity. Em T. Fossum, *Small Animal Surgery* (4th ed., p. 381). Missouri, USA: Elservier.

* Goethem, B. (2015). Use of Drains (Thoracic, Abdominal). *World Small Animal Veterinary Association World Congress Proceedings*, (pp. 1-4). Bangkok.

* Gómez, J., Sañudo, M., & Morales, J. (2007). *Cirurgía en la clínica de pequeños animales* (Vol. El abdomen caudal). Zaragoza, Spain: Servet.

* Kirby, B. (2012). Peritoneum and Retroperitoneum. Em K. Tobias, & S. Johnston, *Veterinary Surgery: Small Animal* (pp. 1414-1416). Elsevier.

* Koenigshof, A. (2019). Acute Abdomen. Em K. Drobatz, K. Hopper, E. Rozanski, & D. Silverstein, *Textbook of Small Animal Emergency Medicine* (Vol. 1, pp. 26-30). Wiley Blackwell.

* Lanz, O. (2011). Closed versus open peritoneal drainage for the maintenance of septic peritonitis. *ACVS Veterinary Symposium, Chicago, Illinois*. pp. 153-155.

* Saile, K. (2015). Drains: Proper use and management (Proceedings).

* Sturgeon, C. (2016). Draining An Abdomen. *British Small Animal Veterinary Congress*.

* Young, A. (2011). Nursing patients with open peritoneal drainage. *Veterinary Nursing Journal*, 189-191.
# CRITICAL CARE NURSING OF THE GI PATIENT

Kenichiro Yagi, MS, RVT, VTS (ECC, SAIM)

Cornell University, Ithaca, NY, United States

Patients with gastroenteritis can present with vomiting, anorexia, and diarrhoea in both dogs and cats which can be caused by dietary indiscretion, infectious diseases, toxins, immunologic diseases, and metabolic dysfunction. Patients hospitalized for gastrointestinal diseases are provided treatment for the underlying cause while supportive care including intravenous fluid therapy, nutritional support, antiemetics, and gastric protectants are employed. It is during this time that nursing care considerations are applied.

## Initial Assessment

Patients with gastroenteritis will present with the same type of signs regardless of the cause. Signs include vomiting, diarrhoea, anorexia, and haematemesis or melaena when severe inflammation or ulceration is present. Depending on how long the signs have been persisting, the patient may present with signs of dehydration or hypovolaemic shock. Abdominal pain may be present, and if haemorrhaging is present the patient may be anaemic. With severe acute vomiting or prolonged diarrhoea, electrolyte disturbances may also be present.

## Causes of Gastroenteritis

A major category of causes of gastroenteritis is infectious causes. Viral, bacterial, parasitic, and fungal are all sources of infectious disease. While canine parvovirus is the most commonly seen infectious GI disease in dogs, there are other viruses that cause GI disease such as coronavirus and rotavirus infections. Feline panleukopenia is similar to canine parvovirus in signs, though occurring in cats. Bacterial organisms such as Clostridium, Campylobacter, Salmonella, Helicobacter, and E. coli are bacteria commonly associated with gastroenteritis. Parasitic organisms such as ascarids, hookworms, and whipworms as well as protozoans such as Giardia, coccidia, and Cryptospora can be associated with mild forms of diarrhoea.

Another form of gastroenteritis includes acute haemorrhagic diarrhoea syndrome which may be a result of an abnormal immune response to bacteria, endotoxin, or dietary ingredients. Dietary indiscretion can lead to inflammation of the GI tract, osmotic diarrhoea, GI trauma, and reactions to chemicals that cause GI signs. Protein-losing enteropathies including lymphocytic-plasmacytic, eosinophilic, or granulomatous inflammatory bowel diseases, lymphangiectasia, and neoplasia can cause significant damage to the intestinal mucosa leading to excessive loss of plasma.

## Treatment and Nursing Care

Treatment and nursing care in GI patients are related to the supportive care provided to patients with gastroenteritis. Because anorexia, vomiting and/or diarrhoea contribute to dehydration and fluid deficit, fluid therapy is warranted. Other forms of treatment depend on the underlying cause, such as the use of antimicrobials or antiparasitics for infectious diseases or anti-inflammatories in protein-losing enteropathies. GI protectants and antiemetics will help improve recovery time of the GI tract. An area commonly given little attention for GI patients aside from providing low fat, easily digestible food is nutrition.
## Early Enteral Nutrition

Feeding a patient when they are vomiting goes against most traditional approaches to nutrition in a patient suffering from gastrointestinal ailments. A typical approach in such a case is to withhold food, designating an NPO (nil per os, or no food or water from the oral route) to prevent nausea from introduction of food and distension of the stomach. Small amounts of easily digestible food are introduce, being increased to a normal amount gradually.

There are several reasons why withholding of food is thought to be beneficial. These include the idea of resting the bowel, as it is irritated and has a reduced ability to absorb the nutrients. Vomiting is also thought to be reduced in frequency when the stomach is empty, giving decreased chances of vomiting and potential aspiration in a critically ill animal. In addition, food contains fat and fibers that are difficult to digest potentially increasing the chances of vomiting even further. In patients with dysfunctional gastrointestinal systems, food will pass into the intestines undigested, leading to bacterial proliferation and osmotic diarrhoea by pulling water into the intestinal lumen. All of these reasons combined, it may seem reasonable to withhold food in a patient with gastrointestinal issues. However, many of these beliefs actually might not be true.

Fasting causes hunger pains, delays cessation of vomiting, prevents healthy healing of GI mucosa, sets the gastric system up for inefficient digestion when food is reintroduced, and makes the GI tract more vulnerable to bacterial translocation and sepsis. Feeding leads to faster intestinal recovery, even when compared to parenteral nutrition, indicating benefits of passive luminal nutrition. Feed those guts!

Specifically for parvoviral enteritis, early enteral nutrition reduced the time for patients to have normal attitude, appetite, ceasing of vomiting and diarrhoea, increased body weight, and improved mucosal permeability when compared with fasting.

## Nutritional Tubes

Nutritional interventions are a vital part of successful treatment of critical care patients, but often overlooked. An animal who is anorexic for as short as 3 days can develop nutritional deficiency related detrimental effects (metabolic derangements, depressed immune system, catabolic wasting, and deteriorating GI system, to name a few), and should receive nutritional support at latest by 5 days into anorexia. While enticing voluntary eating is most comfortable and beneficial for patients, this is not always sufficient to meet nutritional and caloric needs. When a patient is anorexic, there are several methods by which nutritional supplementation can be performed, divided into enteral and parenteral routes.

The least invasive of tubes utilized in nutrition are nasoenteral tubes. Nasoenteral tubes are inserted through the nares and down into the GI tract. Tubes terminating in the oesophagus are called nasooesophageal (NE) tubes, while nasogastric (NG) tubes terminate in the stomach. Nasoenteral tubes are used for short term feeding and are able to be used immediately after placement and typically no longer than 10 days. The tubes are typically too narrow to feed blended canned foods, and require a liquid diet to be infused. When a nasogastric tube is in use the gastric content may be evacuated and measured to determine the degree of functional gastric motility. The placement is
typically well tolerated with none to minimal sedation. Contraindications include patients with intractable vomiting, poor mentation, respiratory distress, facial trauma, or nasal diseases. One of the most important aspects of nasoenteral tube placement lies in prevention of tracheal placement. Food infused into the trachea can very easily turn into life-threatening respiratory compromise. Radiographic confirmation of appropriate placement should always be performed to prevent this. Other complications include epistaxis, rhinitis, and vomiting. If vomiting occurs, the placement of the tube should be rechecked to make certain the tube did not come up the oesophagus and inhaled into the trachea. The tube can also clog due to its narrowness, and requires constant infusions or flushing after bolus feedings.

Oesophagostomy tubes may be opted to be placed through the side of the neck in a surgical procedure for patients requiring longer term nutritional intervention. Oesophagostomy tubes can be used immediately upon placement and for up to 20 weeks when cared for properly. The larger diameter when compared to nasoenteral tubes allows for feeding of blended canned foods, providing the ability to meet nutritional needs more easily. It is also useful in patients with facial trauma or nasal diseases as it bypasses the muzzle into the GI tract. The procedure does require anaesthesia to perform. Another significant advantage is the ability for an owner to take a patient home with an oesophagostomy tube for long term care and relieving the need for hospitalization for nutritional management. The tube should be flushed with 5-10mL of water after feeding to prevent the tube from being clogged. Main complications include blocked tubes, displacement of the tube by vomiting or intentional removal by the patient, and stoma site infections. The stoma site (insertion site) of the tube requires regular monitoring for redness, swelling, and signs of infections.

Gastrostomy tubes (G tubes) are another surgically placed enteral feeding tube. G tubes extend from the skin on the side of the abdomen and into the stomach. G tubes are used for long term enteral feeding, capable of providing nutrition for years after placement. Polyurethane or silicone based G tubes are required for long term use as they are resistant to loss of integrity from digestive enzymes. Fibrin sealing of the stoma site will occur within 12-24 hours after placement, and feeding should not be started until this seal is formed to avoid contamination and infection of the site. This option may be taken when the patient has oesophageal disorders, facial or oral trauma. There is a higher cost associated with the procedure, which may make it cost prohibitive. As this is a more invasive surgical procedure, there is a higher anaesthetic risk involved, and should be avoided with patients with healing impairments. Patients vomiting consistently should be held off for the procedure until vomiting is under control. G tubes require similar attention to the stoma site as oesophagostomy tubes. Complications include vomiting, aspiration pneumonia, peritonitis, accidental tube removal, pressure necrosis, and stoma site infection.

Jejunostomy tubes are more rarely placed, bypassing the stomach and into the jejunum. The tube may be used from weeks to months, and is used when resting of the upper GI tract is necessary. These include patients with pancreatitis, uncontrolled vomiting, gastroparesis, and recent gastric surgery. Feeding can commence 12-24 hours after placement. Liquid diets are necessary since the tube diameter is narrow. Constant infusions alleviate the risks of cramping and diarrhoea. Patients with jejunostomy tubes require close monitoring and will need to be hospitalized. Complications include osmotic diarrhoea and vomiting. Obstruction of the tube is a common complication, and can be best avoided through periodic flushing (every 4 hours). If there is leakage of GI tract content, a peritonitis
can develop and is a serious complication. When the GI tract is dysfunctional altogether, parenteral nutrition should be used, and can be provided through a dedicated sterile port through a central line.

Enteral nutrition is important in mainlining a healthy GI tract and mucosa. Many of the traditional thoughts of benefits to withholding food does not hold up to be as detrimental when compared to the benefits of early enteral feeding. Because of this, knowledge of use and maintenance of enteral feeding tubes will allow one to help influence a positive patient outcome. In the case of parvovirus gasteroenteritis, anything more invasive than nasoenteral tubes are rarely used.

## Nutritional Plan

When the decision is made to feed the patient, there are a few key points to consider. What will we feed? How much of it will be fed and how fast?

Current recommendations include oral rehydration over 3-4 hours, and then introducing food. It is unreasonable to attempt feeding their full maintenance energy requirement for patients suffering from acute diarrhoea or frequent vomiting. The amount that can be reasonably be fed initially should be targeted for 1/4 resting energy requirement (RER), as a highly digestible, low-fat diet in order to ensure healthy gut recovery and minimal stimulation of vomiting and diarrhoea.

An animal's RER can be calculated by the formula: $RER = 70 \times (BW in kg)^{0.75}$ kcal per day. As an example, a patient that is 15kg would have a RER of $70 \times 15^{0.75} = 533.5$ kcal per day. ¼ of this will be 133.4 kcal, leading to a feeding rate of 5.6 kcal per hour. Depending on the energy density of the diet being fed, the volume will differ.

The type of food fed in these cases ideally should be highly digestible. There are many commercial diets available which are highly digestible (gastrointestinal diets). The diet should also be low in fat content, with less than 20% of metabolizable energy coming from fat. Excessive fiber content should be avoided since it can cause delayed gastric emptying, diarrhoea, flatulence, and abdominal pain. The recommended level is no more than 8% dietary fiber.

In critical care, especially for feeding through a nasoenteral tube, liquid diets are employed. Products such as Clinicare have been a commonly used diet due to the simple calculation of the volume required to fulfill RER through its caloric density of 1 kcal/mL. The product also comes readily made as a liquid in a can, making preparation simpler. There are newer products on the market such as Emeraid Critical Care HDN specifically formulated for dogs and cats and being highly digestible. This product is formulated for critical care patients at a higher default caloric density of 1.5-2.4 kcal/mL (concentration is adjustable as it is mixed with water on preparation), allowing for lower volume feeding. The choice of liquid diet may vary depending on clinician preference.

Regardless of what product is used, early implementation of nutrition is the key element to encouraging swift recovery of patients with parvoviral enteritis, providing passive nutrition for the enterocytes which prevents mucosal breakdown and bacterial translocation. Technicians play a large role in advocating for patients and their proper nutrition to influence patient outcomes.
## Oral Recuperation Fluids as a Supplement

An additional tool that has been added to our toolbox are oral recuperation fluids (ORFs). Oral recuperation fluids typically contain prebiotics, omega 3 and 6 fatty acids, and amino acids such as glutamine, arginine, and taurine and are provided to assist animals to recovery from illness. The intended effect of the fluid is to improve immune function and aid in regaining of normal mucosal morphology and permeability, as well as encouraging early regaining of voluntary appetite. The data associated with studies on ORFs shows a significant decrease in time to regaining voluntary appetite and an increase in percent of RER consumed the first 24 hours after return of appetite. The ORF can be provided in place of, or alongside a bowl of water, fed via syringe, or through feeding tubes.
# WHAT IS ON THE MENU? NUTRITIONAL SUPPORT OF THE CRITICAL PATIENT

Louise O'Dwyer MBA BSc(Hons) VTS(ECC) DipAVN(Medical&Surgical) RVN
Clinical Support Manager, Vets Now
louise.odwyer@vets-now.com

The provision of adequate and timely nutritional support for patients during recovery from illness, trauma or surgery is vital. The majority of patients will recover from fairly mild illness or elective surgical procedures without any issues, but patients presenting with more severe disease or trauma, or those undergoing more complex surgical procedures, are likely to have prolonged recoveries, and therefore nutrition will need to be addressed early during the hospitalisation period.

The appropriate absorption of essential nutrients and energy, along with fluids, is of primary importance during the first 14 days following trauma or the onset of severe illness, in order to ensure the effective functioning of the gastrointestinal and immune systems. Wherever possible the enteral route should be selected, vs. parenteral nutrition, as intraluminal nutrition will stimulate the gastrointestinal tract and help reduce the incidence of bacterial translocation.

The majority of critically ill patients will not have sufficient voluntary food intake to meet even minimal nutritional needs. When dealing with trauma patients, this situation is even more acute. All too often is it perceived that this lack of adequate food intake, whilst not desirable, will have no serious implications on the patient's clinical outcome. For many patients, this will be the case; however, the more serious the illness, and the more metabolically stressed the patient is, the more likely that the patient's nutritional status will deteriorate to an extent where it may suffer nutritionally related complications such as immunosuppression or poor wound healing. Whilst the more critical patients can be more challenging in terms of providing assisted feeding, the initial nutritional assessment will greatly help in the process of choosing the route of feeding a suitable diet, and the development of a plan for monitoring the patient during feeding so that problems or complications can be prevented or at least recognised early and quickly addressed. Individual patient's nutritional assessment serves several purposes. It allows a determination of the patient's nutritional status. This evaluation is based on the patient's medical history and physical examination. Once an assessment of the patient's nutritional status and food intake has been made, these factors along with the severity of the patient's current illness and whether there are any pre-existing or current medical conditions can be taken into consideration when deciding upon whether some type of assisted feeding will be required for the patient, and how proactive the approach should be to initiating assisted feeding.

## Calculating Calorie Requirements

The resting energy expenditure (RER) is the number of calories necessary for a non-stressed animal in the post-prandial state in a calm, thermoneutral environment. In other words, it is the amount of energy necessary for basic functions not including obtaining and digesting foodstuffs. Caloric goals are based on the resting energy requirements (RER), which are calculated by one of two formulas:

* Linear formula:
  RER in kcal/day = (30 x bodyweight in kg) + 70

* Exponential formula:
$$RER \text{ in kcal/day} = 70 \times (\text{bodyweight in kg})^{0.75}$$

The patient should be fed approximately 25% to 30% of its caloric requirement on the first day of feeding, with subsequent gradual increases of 25% to 30% of its caloric requirement per day. We previously added an illness energy requirement (IER) to the RER. The IER is the energy requirement associated with illness, injury, infection and inflammation. The IER is an arbitrary number multiplied by the RER to combat the proposed increase in caloric requirements associated with various forms of illness. However, studies have found no increase in RER in numerous hospitalised patients, so this value is generally the value selected when calculating the patient's nutritional requirements. At minimum daily weighing and reassessment of body condition scoring should be performed, and the patients RER should be increased or decreased dependent on these parameters.

For any patient that has undergone a period of prolonged starvation a longer period of food introduction should be considered, for example:

* Day 1 – 1/6 RER with electrolyte monitored q4-8hrs

* Day 2 – 2/6 RER with electrolyte monitoring q 4-8hrs

* Day 3 – 3/6 RER with electrolyte monitoring q 4-8hrs

Common side effects of starting feeding patients that have undergone prolonged periods of malnutrition may include nausea, vomiting, diarrhoea, changes in the electrolyte balance and if re-feeding syndrome develops acute haemolytic anaemia in cats. It is important to note that if refeeding syndrome does develop we should not stop feeding these patients as we need to move them from a catabolic state to an anabolic state, however we may alter the amounts fed or the constitution of food administered. It is essential that we monitor any patient with an extended period of anorexia for re-feeding syndrome. This can be signified by changes in patient demeanour, changes in patient's electrolyte and acid-base balance and can be extremely dangerous if undetected.

Re-feeding syndrome is characterised by changes in the patient's electrolyte balance following re-introduction of nutritional support following a prolonged period of malnutrition/anorexia. Hypophosphataemia is the most significant disturbance of refeeding syndrome. "Refeeding syndrome" is a description of multiple metabolic disturbances that occur during and complicate the reinstatement of oral, enteral, or parenteral nutrition in malnourished or starved patients. In contrast to the human literature, which states that hypophosphataemia is frequently associated with reinstatement of alimentation in at-risk patients, only a handful of reports document the same occurrence in veterinary patients.

## Creating the Nutritional Plan

One of the first stages in creating a nutritional plan is to ensure fluid deficits, e.g. hypovolaemia or dehydration, have been addressed, ensuring the patient is haemodynamically stable, along with correction of electrolyte or acid-base imbalances. Once these issues have been corrected then the nutritional plan can be instituted, which aims to achieve target levels of nutrient delivery within 48 – 72 hours. It is also essential that the nutritional plan is reassessed, which includes assessment of the patient tolerance of feeding, regular assessment of bodyweight and body condition scoring, along with monitoring patients for complications associated with nutritional support, e.g. electrolyte
disturbances, hyperglycaemia, vomiting, regurgitation, aspiration and infections related to the
presence of a feeding tube.

In patients that do not have any contraindications to enteral feeding, e.g. vomiting, then the placement of a feeding tube should be considered early in the hospitalisation period, particularly if injuries are present which indicate the requirement of prolonged nutrition, e.g. jaw fractures.

An additional consideration, often overlooked, with trauma patients is the requirement for daily sedation or anaesthesia for procedures such as dressing changes, or wound debridement. It is not uncommon for these patients to be fasted for periods of 8-12 hours prior to having these procedures performed, and if this is not factored into a nutritional plan, these patients are at risk of malnourishment.

## Choice of feeding tube

The best feeding tubes for prolonged use are made of polyurethane or silicone. For short-term feeding (<10 days), polyvinylchloride can be used. Silicone is softer and more flexible than other tubing materials and has a greater tendency to stretch and collapse. Polyurethane is stronger than silicone, which allows for thinner tube walls and a greater internal diameter, despite the same overall French size. Both silicone and polyurethane tubes do not disintegrate or become brittle in situ. The French (Fr) unit measures the outer lumen diameter of a tube; each unit is equal to 0.33 mm.

## Naso-oesophageal and nasogastric tubes

Naso-oesophageal tubes can be inserted using minimal equipment and standard techniques. Nasogastric tubes are inserted in a similar fashion as naso-oesophageal tubes, but they should be long enough to reach 7–10 cm past the last rib. Both types of tubes are useful for providing short-term nutritional support (usually <7 days). They can be used in animals with a functional oesophagus, stomach and intestines. Naso-oesophageal tubes are contraindicated in animals that are vomiting, comatose, lack a gag reflex or have respiratory diseases. Complications include epistaxis, intolerance of the insertion procedure and inadvertent removal by the animal. Because of the small internal diameter of these tubes, only liquid enteral diets can be used. Feeding may be delivered via a syringe pump as a continuous rate infusion or as bolus feedings. If a syringe pump is used, the delivery equipment must be completely changed every 24 hours to help prevent bacterial growth within the system. Clogging of these tubes is a common problem, due to the narrow bore, but the incidence can be decreased by using a syringe pump or flushing the tube well before and after bolus feedings. A column of water should always remain within the feeding tube in between feeds. If the tube becomes clogged, replacement may be necessary, or carbonated drinks may be used to remove the blockage. Diluting the liquid diet with water may also help prevent clogging, but this decreases the caloric concentration of the diet and increases the volume necessary to meet caloric needs. Maintenance of the tube should be carried out by cleaning the external nares gently using a warm, damp cotton wool ball. If tubes do become blocked, then carbonated drinks may be used to unclog the blockage. The tube can be removed at any point following placement. When removing the tubes, they are simply pulled out after the skin adhesive or sutures are removed.

## Oesophagostomy tubes

Oesophagostomy tubes are ideal for patients with head or jaw injuries, and are particularly useful in
cats. The placement of oesophagostomy tubes requires general anaesthesia, with the animal intubated and in lateral recumbency. Complications include tube displacement from vomiting, removal or damage to the tube by the animal, and skin infection around the exit site. Depending on the insertion technique used and the size of the animal, an 8–20 Fr catheter may be used. The large bore of these catheters allows the feeding of a thicker recovery diet. These catheters are also easy for owners to use and maintain, as long as vomiting is not a problem. The tube may simply be pulled out after the sutures are removed. The exit hole is allowed to heal by second intention. A light bandage may be applied over the exit site for the first 12 hours.

## Oesophagostomy tube removal

After every bolus feeding the tube will require a flush of water to rinse it of food debris. The tube exit site will require topical cleaning using sterile saline or chlorhexidine solution, the use of topical antimicrobials rather than antibiotic cream at the stoma site should be encouraged. A light bandage is applied and the entire dressing is changed every 6-12 hours. When the tube is no longer needed, it is simply removed by cutting the skin sutures and the tube is pulled out. The wound can be stapled or left to granulate. The exit site will granulate within a few days.

## Gastrostomy tubes

Gastrostomy tubes can be inserted blindly using specialised equipment, placed with the aid of a gastroscope (i.e. percutaneous endoscopic gastrostomy [PEG] tube), or be surgically inserted. These tubes can be placed in any animal that can withstand general anaesthesia. A minimum of 12 hours, preferably 24 hours, is needed for a temporary stoma to form before feeding can begin, and the feeding tube should be left in place a minimum of 7–10 days to allow a permanent stoma to form before removal. These tubes can be left in long term (1–6 months), often without replacement. Complications associated with PEG tubes include those that arise acutely during tube placement (e.g. splenic laceration, gastric haemorrhage, pneumoperitoneum) and those that are delayed (e.g. vomiting, aspiration pneumonia, tube removal, tube migration, peritonitis and infection around the stoma). Most animals are able to eat normally with gastrostomy tubes in place, and the tubes can easily be used as a source of additional nutritional supplementation until the animal is eating normally. For animals that are difficult to medicate or require long-term medications, many medicines can be given through the feeding tube at the clinician's discretion. The major disadvantages of gastrostomy tubes are the need for general anaesthesia during insertion and the risk of peritonitis from inadvertent removal before a permanent stoma develops. For animals requiring feeding tubes over a long duration, the initial gastrotomy tube can be replaced with a low profile silicone tube. The low-profile silicone tube can be placed through the external stoma site without an endoscope.

## Jejunostomy tubes

Jejunostomy tube feeding is indicated when the upper gastrointestinal tract must be rested or when decreased pancreatic stimulation is desirable. Jejunal tubes can be placed either surgically or threaded through a gastrostomy tube (transpyloric placement). Standard gastrojejunal tubes designed for humans are unreliable in dogs because of the frequent reflux of the jejunal portion of the tube back into the stomach so for this reason 'weighted' tubes should be selected. Common complications of jejunostomy tubes include osmotic diarrhoea and vomiting. It is recommended that the jejunal tube be left in place for 7–10 days to allow adhesions to form around the tube site, preventing leakage into the abdomen. Completely changing the delivery equipment every 24 hours helps to prevent bacterial
growth within the system. Clogging is a common problem. Use of a syringe or intravenous pump and flushing the tube well every 4 hours may help to decrease the incidence of clogging. When removing the tube, it may simply be pulled out after the sutures are removed. The exit hole is allowed to heal by second intention. A light dressing should be applied for the first 12 hours following removal.

## Procedure

Unplug the tube, then flush the tube with 5-10 ml sterile water, 10-20 ml warm water after each feed. Avoid cold water as this can induce vomiting and diarrhoea and the animal also has to expend energy to warm it. The tube should be flushed regularly even when not in use.

## Feeding via a tube

It is important to start feeding any patient with a feeding tube in place gradually. The patient's full RER should be introduced over 2-3 days. This allows the patient's gastrointestinal tract and metabolism time to adjust to tube feeding. It is generally advised to start with one-third to half the calculated amount of food diluted with water and gradually increase the volume fed each day. A good protocol to use is 10 mL/kg every 2-3 hours on day 1, increasing gradually to 50 mL/kg 3-4 times per day. A minimum of three feeds should be given per day. Food must be iso-osmolar and given slowly (over 10-15 minutes) and warmed to approximately body temperature. During the early stages of introducing nutritional support, electrolyte monitoring should be carried out every 4-8 hours in order to detect the occurrence of refeeding syndrome.

## How long to feed?

Patients should be tube fed until they voluntarily eating more than 85% of their calculated daily requirements. Tube feeding should be withdrawn gradually, just as it was introduced gradually, to allow the necessary gastrointestinal and metabolic adjustments. It is important to continue feeding a specialist diet at increased requirements for a period after the patient goes home. The following periods are currently used by the author:

* 2 weeks following uncomplicated major surgery;

* 2-4 weeks after trauma;

* 4-12 weeks after major trauma including head trauma;

* Months in cases of chronic disease and neoplasia.

## Summary

Nutritional support in critical patients is all too often not considered a priority, but careful consideration needs to be given to the individual patient's nutritional status on presentation, the injuries the patient has sustained, any alterations in metabolic condition, requirement for periods of fasting to allow procedures to be performed during the hospitalisation period, and the provision of continued nutrition once the patient has been discharged from the hospital. Careful consideration of all these factors along with planning and execution of a nutritional plan can play a major role in the successful recovery of these patients.
# WHY YOUR PARVO (AND OTHER GI) PATIENTS SHOULD BE FED RIGHT AWAY

Kenichiro Yagi, MS, RVT, VTS (ECC, SAIM)

Cornell University College of Veterinary Medicine

Ithaca, New York, United States

Canine parvovirus (CPV) infections cause severe gastroenteritis, lead to dehydration, shock, disseminated intravascular coagulation, bacterial translocation and sepsis when left untreated. With aggressive treatment, the mortality rate can be reduced to between 0% and 30% from 90%. Therapeutic options in addition to fluid and pharmacologic therapy speeding gastrointestinal recovery are desirable to reduce patient mortality and morbidity, as well as financial strain to the clients for prolonged aggressive treatment. Use of elaborate treatment options such as oseltamivir (Tamiflu), interferon omega, recombinant bactericidal proteins, equine lipopolysaccharide antitoxin, human recombinant factors, and antibody rich plasma have not shown promising results. One simple to implement, therapeutic option that makes a significant difference in survival chance is enteral feeding started within hours of admission, even when vomiting.

## Feeding When Vomiting

Feeding a patient when they are vomiting goes against most traditional approaches to nutrition in a patient suffering from gastrointestinal ailments. A typical approach in such a case is to withhold food, designating an NPO (nil per os, or no food or water from the oral route) to prevent nausea from introduction of food and distension of the stomach. Small amount of easily digestible food is introduced, being increased to a normal amount gradually.

There are several reasons why withholding of food is thought to be beneficial. These include the idea of resting the bowel, as it is irritated and has a reduced ability to absorb the nutrients. Vomiting is also thought to be reduced in frequency when the stomach is empty, giving decreased chances of vomiting and potential aspiration in a critically ill animal. In addition, food contains fat and fibers that are difficult to digest potentially increasing the chances of vomiting even further. In a patient with dysfunctional gastrointestinal systems, food will pass into the intestines undigested, leading to bacterial proliferation and osmotic diarrhoea by pulling water into the intestinal lumen. All of these reasons combined, it may seem reasonable to withhold food in a patient with gastrointestinal issues. However, many of these beliefs actually might not be true.

One argument for feeding early, is that the guts are actually not able to rest when being fasted. Fasting causes a phenomenon called "hunger pains", which arises from intense peristaltic contractions migrating down from the pylorus to the ileum. The peristaltic activity is decreased when nutrients are present in the intestinal lumen, allowing for better rest of the guts, and nutritional absorption. If fasting leads to less rest and pain to the patient, feeding is the better option.

Does feeding actually lead to more vomiting? A study evaluating this with patients with haemorrhagic gastroenteritis indeed did observe an increased frequency of vomiting upon feeding when compared to fasting. However, they also saw that the frequency of vomiting decreased below the fasted dogs by day 2. Feeding creates a prokinetic effect, and reduces emesis, leading to an overall shortening of the time before the patient stops vomiting. The presence of food in the gastrointestinal lumen also
decreases insult to the mucosa from toxins, reducing vomiting. The concept behind food minimizing chances of vomiting when certain medication is given along with it applies here as well. Feeding causes more vomiting initially, but leads to a quicker subsiding of vomiting.

Food high in fat and soluble fibers and large volume feedings can indeed increase chances of vomiting. Maldigestion and gastrointestinal distention stimulates vomiting. Small, frequent feedings are recommended to reduce gastric acid release, leading to reduced vomiting. In many cases, employment of anti-emetic drugs help in preventing vomiting, allowing earlier enteral nutrition. Adequate antiemesis is especially important for inappetant patients requiring placement of NE or NG tubes.

Undigested food being present in the intestinal lumen does increase nutritional resources for microorganisms leading to bacterial proliferation. However, feeding increases levels of volatile fatty acids such as butyrate and propionate, reducing the population of bacteria sensitive to acidic environments (Campylobacter and Clostridium spp.). The presence of food helps maintain enteric barriers, preventing bacterial translocation (movement of bacteria from the guts into the blood stream) and subsequent sepsis. Diarrhoea in dogs is attributed to unabsorbed nutrients and endogenously derived osmotic elements instead of osmotic pressure created by undigested food. Insult to the intestinal mucosa preventing absorption of water and increased effusion through leaky blood vessels (increased vascular permeability) is alleviated with enteral nutrition, which helps reduce diarrhoea when compared to a fasted state.

Fasting causes a plethora of negative effects that outweigh the small benefits it may have. Fasting causes reduced expression of digestive enzymes, impairing digestive function when food is reintroduced. Presence of nutrients reduces inflammation by inhibiting expression of adhesion molecules, preventing activation of neutrophils which contribute to mucosal damage and impair immune response. Malnutrition leads to protein, essential fatty acid, mineral and vitamin deficiencies preventing healthy turnover of gastrointestinal mucosa. Feeding leads to faster intestinal recovery, even when compared to parenteral nutrition, indicating benefits of passive luminal nutrition. Feed those guts!

Specifically for parvoviral enteritis, early enteral nutrition reduced the time for patient to have normal attitude, appetite, ceasing of vomiting and diarrhoea, increased body weight, and improved mucosal permeability when compared with fasting.

## Nutritional Tubes

Nutritional interventions are a vital part of successful treatment of critical care patients, but often overlooked. An animal who is anorexic for as short as 3 days can develop nutritional deficiency related detrimental effects (metabolic derangements, depressed immune system, catabolic wasting, and deteriorating GI system, to name a few), and should receive nutritional support at latest by 5 days into anorexia. While enticing voluntary eating is most comfortable and beneficial for patients, this is not always sufficient to meet nutritional and caloric needs. When a patient is anorexic, there are several methods by which nutritional supplementation can be performed, divided into enteral and parenteral routes.
The least invasive of tubes utilized in nutrition are nasoenteral tubes. Nasoenteral tubes are inserted through the nares and down into the GI tract. Tubes terminating in the oesophagus are called nasooesophageal (NE) tubes, while nasogastric (NG) tubes terminate in the stomach. Nasoenteral tubes are used for short term feeding and are able to be used immediately after placement and typically no longer than 10 days. The tubes are typically too narrow to feed blended canned foods, and require a liquid diet to be infused. When a nasogastric tube is in use the gastric content may be evacuated and measured to determine the degree of functional gastric motility. The placement is typically well tolerated with none to minimal sedation. Contraindications include patients with intractable vomiting, poor mentation, respiratory distress, facial trauma, or nasal diseases. One of the most important aspects of nasoenteral tube placement lies in prevention of tracheal placement. Food infused into the trachea can very easily turn into life-threatening respiratory compromise. Radiographic confirmation of appropriate placement should always be performed to prevent this. Other complications include epistaxis, rhinitis, and vomiting. If vomiting occurs, the placement of the tube should be rechecked make certain the tube did not come up the oesophagus and inhaled into the trachea. The tube can also clog due to its narrowness, and requires constant infusions or flushing after bolus feedings.

Oesophagostomy tubes may be opted to be placed through the side of the neck in a surgical procedure for patients requiring longer term nutritional intervention. Oesophagostomy tubes can be used immediately upon placement and for up to 20 weeks when cared for properly. The larger diameter when compared to nasoenteral tubes allows for feeding of blended canned foods, providing the ability to meet nutritional needs more easily. It is also useful in patients with facial trauma or nasal diseases as it bypasses the muzzle into the GI tract. The procedure does require anaesthesia to perform. Another significant advantage is the ability for an owner to take a patient home with an oesophagostomy tube for long term care and relieving the need for hospitalization for nutritional management. The tube should be flushed with 5-10mL of water after feeding to prevent the tube from being clogged. Main complications include blocked tubes, displacement of the tube by vomiting or intentional removal by the patient, and stoma site infections. The stoma site (insertion site) of the tube requires regular monitoring for redness, swelling, and signs of infections.

Gastrostomy tubes (G tubes) are another surgically placed enteral feeding tube. G tubes extend from the skin on the side of the abdomen and into the stomach. G tubes are used for long term enteral feeding, capable of providing nutrition for years after placement. Polyurethane or silicone based G tubes are required for long term use as they are resistant to loss of integrity from digestive enzymes. Fibrin sealing of the stoma site will occur within 12-24 hours after placement, and feeding should not be started until this seal is formed to avoid contamination and infection of the site. This option may be taken when the patient has oesophageal disorders, facial or oral trauma. There is a higher cost associated with the procedure, which may make it cost prohibitive. As this is a more invasive surgical procedure, there is a higher anaesthetic risk involved, and should be avoided with patients with healing impairments. Patients vomiting consistently should be held off for the procedure until vomiting is under control. G tubes require similar attention to the stoma site as oesophagostomy tubes. Complications include vomiting, aspiration pneumonia, peritonitis, accidental tube removal, pressure necrosis, and stoma site infection.
Jejunostomy tubes are more rarely placed, bypassing the stomach and into the jejunum. The tube may be used from weeks to months, and is used when resting of the upper GI tract is necessary. These include patients with pancreatitis, uncontrolled vomiting, gastroparesis, and recent gastric surgery. Feeding can commence 12-24 hours after placement. Liquid diets are necessary since the tube diameter is narrow. Constant infusions alleviate the risks of cramping and diarrhoea. Patients with jejunostomy tubes require close monitoring and will need to be hospitalized. Complications include osmotic diarrhoea and vomiting. Obstruction of the tube is a common complication, and can be best avoided through periodic flushing (every 4 hours). If there is leakage of GI tract content, a peritonitis can develop and is a serious complication. When the GI tract is dysfunctional all together, parenteral nutrition should be used, and can be provided through a dedicated sterile port through a central line.

Enteral nutrition is very important in maintaining a healthy GI tract and mucosa. Many of the traditional thoughts of benefits to withholding food do not hold up to be as detrimental when compared to the benefits of early enteral feeding. Because of this, knowledge of use and maintenance of enteral feeding tubes will allow one to help influence a positive patient outcome. In the case of parvovirus gasteroenteritis, anything more invasive than nasoenteral tubes is rarely used.

## Nutritional Plan

When the decision is made to feed the patient, there are a few key points to consider. What will we feed? How much of it will be fed and how fast?

Current recommendations include oral rehydration over 3-4 hours, and then introducing food. It is unreasonable to attempt feeding their full maintenance energy requirement for patients suffering from acute diarrhoea or frequent vomiting. The amount that can reasonably be fed initially should be targeted for 1/4 resting energy requirement (RER), as a highly digestible, low-fat diet in order to ensure healthy gut recovery and minimal stimulation of vomiting and diarrhoea.

An animal's RER can be calculated by the formula: $RER = 70 \times (BW \text{ in kg})^{0.75}$ kcal per day. As an example, a patient that is 15kg would have a RER of $70 \times 15^{0.75} = 533.5$ kcal per day. ¼ of this will be 133.4 kcal, leading to a feeding rate of 5.6 kcal per hour. Depending on the energy density of the diet being fed, the volume will differ.

The type of food fed in these cases ideally should be highly digestible. There are many commercial diets available which are highly digestible (gastrointestinal diets). The diet should also be low in fat content, with less than 20% of metabolizable energy coming from fat. Excessive fibre content should be avoided since it can cause delayed gastric emptying, diarrhoea, flatulence, and abdominal pain. The recommended level is no more than 8% dietary fibre.

In critical care, especially for feeding through a nasoenteral tube, liquid diets are employed. Products such as Clinicare have been commonly used due to the simple calculation of the volume required to fulfill RER through its caloric density of 1 kcal/mL. The product also comes readily made as a liquid in a can, making preparation simpler. There are newer products on the market such as Emeraid Critical Care HDN specifically formulated for dogs and cats and being highly digestible. This product is formulated for critical care patients at a higher default caloric density of 1.5-2.4 kcal/mL
(concentration is adjustable as it is mixed with water on preparation), allowing for lower volume feeding. The choice of liquid diet may vary depending on clinician preference.

Regardless of what product is used, early implementation of nutrition is the key element to encouraging swift recovery of patients with parvoviral enteritis, providing passive nutrition for the enterocytes which prevents mucosal breakdown and bacterial translocation. Technicians play a large role in advocating for patients and their proper nutrition to influence patient outcomes.

## Outpatient vs Inpatient Strategies for Parvoviral Enteritis

When a patient presents with parvoviral enteritis and the client is given the choice of hospitalized care for their pet, the cost of hospitalization commonly become a point of concern, especially when multiple animals in a litter is considered. In these situations, the question of whether parvoviral enteritis can be managed through an outpatient protocol can provide a significant chance of survival.

A study comparing outpatient protocol and inpatient protocol for treatment of canine parvoviral enteritis which utilized IV crystalloids, replacement of ongoing loss, KCl supplementation, IV antibiotics and IV antiemetics for the inpatient protocol and subcutaneous fluids ignoring ongoing loss, no potassium supplementation, long duration subcutaneous antibiotics, and subcutaneous antiemetics saw that there was no significant difference in survival chance and hospitalization time between patients in the two groups.

The one common intervention both groups received was the providing of a canine convalescence diet via syringe until the appetite regained, which likely highlights the importance of early enteral nutrition in survival chance. The authors commented that early enteral nutrition leads to earlier clinical improvement and syringe feeding is realistic for an outpatient protocol.

## Oral Recuperation Fluids as a Supplement

An additional tool that has been added to our toolbox are oral recuperation fluids (ORFs). Oral recuperation fluids typically contain prebiotics, omega 3 and 6 fatty acids, and amino acids such as glutamine, arginine, and taurine and are provided to assist animals to recovery from illness. The intended effect of the fluid is to improve immune function and aid in regaining of normal mucosal morphology and permeability, as well as encouraging early regaining of voluntary appetite. The data associated with studies on ORFs shows significant decrease in time to regaining voluntary appetite and an increase in percent of RER consumed the first 24 hours after return of appetite. The ORF can be provided in place of, or alongside a bowl of water, fed via syringe, or through feeding tubes.

With the clear evidence of better patient outcome with institution of early enteral nutrition we should do everything we can to advocate for it to improve patient outcome in the GI patients.

## References

1. Harris, JP., Parnell, NK., Griffith, EH., et al. Retrospective evaluation of the impact of early enteral nutrition on clinical outcomes in dogs with pancreatitis: 34 cases (2010-2013). 2017;24:425-433.
2. Liu, DT., Brown, DC., Silverstein, DC. Early nutritional support is associated with decreased length of hospitalization in dogs with septic peritonitis: A retrospective study of 45 cases (2000-2009). J Vet Emerg Crit Care 2012;22:453-459.

3. Mohr, AJ., Leisewitz, AL., Jacobson, LS., et al. Effect of Early Enteral Nutrition on Intestinal Permeability, Intestinal Protein Loss, and Outcome in Dogs with Severe Parvoviral Enteritis. J Vet Intern Med 2003;17:791-798.

4. Tenne, R., Sullivan, LA., Contreras, ET., et al. Palatability and Clinical Effects of an Oral Recuperation Fluid During the Recovery of Dogs With Suspected Parvoviral Enteritis. Topics in Compan An Med 2016;31:68-72.

5. Venn, EC., Preisner, K., Boscan, PL., et al. Evaluation of an outpatient protocol in the treatment of canine parvoviral enteritis. 2017;27:52-65.

6. Will, K., Nolte, I., Zentek, J. Early Enteral Nutrition in Young Dogs Suffering from Haemorrhagic Gastroenteritis. J Vet Med 2005;52:371-376.

7. Yu, MK., Freeman, LM., Heinze, CR., et al. Comparison of compilation rates in dogs with nasoesophageal versus nasogastric feeding tubes. J Vet Emerg Crit Care 2013;23:300-304.
ANAESTHESIA AND ANALGESIA CONSIDERATION FOR THE GI PATIENT

Louise O'Dwyer MBA BSc(Hons) VTS(ECC) DipAVN(Medical&Surgical) RVN
Clinical Support Manager, Vets Now
louise.odwyer@vets-now.com

GI emergencies are one of the most common emergency presentations. Patients presenting with gastrointestinal disorders or dysfunctions - gastric dilatation volvulus, haemoabdomen, intestinal/abdominal foreign body, gastrointestinal perforation, etc - routinely require general anaesthesia to facilitate complete examination, obtain necessary diagnostic testing or imaging, or for surgical intervention. Specific considerations regarding the type of gastrointestinal dysfunction should be made for each step in the anaesthetic process from premedication and induction to the recovery and postoperative phases. Good anaesthetic monitoring during critical GI procedures can mean the difference between life and death.

All elements of the anaesthetic plan come into play when considering what monitors to use and knowing what values to expect from those monitors. Many premedicants have expected side effects and it is necessary to differentiate between what is caused by a drug and what is caused by the procedure or condition. It is also imperative to know what drugs are on board that could potentially be increased, decreased, or reversed.

When creating an anaesthetic plan the premedication combination typically consists of a sedative and an analgesic. The sedative or analgesic chosen will depend greatly on the type and severity of the gastrointestinal issue and the personality of the patient. Standard choices for sedatives include benzodiazepines, phenothiazines, and alpha-2 adrenergic agonists.

Benzodiazepines provide adequate sedation (but no analgesia) for most patients with calm personalities. They have little negative effect on cardiovascular, respiratory, or gastrointestinal systems. Benzodiazepines can be quickly reversed using flumazenil.

Phenothiazines provide good sedation (but again, no analgesia) for most animals and are a good choice for aggressive or anxious patients. They are potent anti-emetics, which is of benefit when dealing with patients who should not be vomiting (i.e., GDVs, foreign bodies with a sharp element, megaoesophagus, perforation, etc). Phenothiazines may decrease sensitivity to some ventricular arrhythmias and can decrease the seizure threshold. Phenothiazines have little effect on respiratory function, but can result in dramatic reduction in cardiovascular output. It may cause some decrease in the time of gastric emptying. There is evidence that phenothiazines can cause splenic enlargement. This can cause difficulty for surgeons working in the abdominal cavity. This category of drugs may also interfere with platelet aggregation. Phenothiazines are not reversible.

Alpha-2 adrenergic agonists provide excellent sedation for most patients and provide very minor analgesia (not enough for any surgical purpose). The level of respiratory depression can vary greatly and the response may be erratic. This class of drug can cause dark mucous membrane colour that is unrelated to oxygenation of tissue. In patients with respiratory compromise (if abdominal contents are restricting respiration) this can make it more difficult to visually assess potential hypoxaemia. It
can cause profound bradycardia and vasoconstriction. It is not an appropriate drug choice for any patient with cardiac compromise. It causes emesis in some dogs and most cats, though this is seen less often when administered intravenously. It may decrease gastric motility. Alpha-2 adrenergic agonists are reversible with atipamezole.

The second part of the premedication mixture is an appropriate opioid analgesic. There are many choices available for a variety of situations. Butorphanol is an agonist-antagonist and buprenorphine is a partial agonist. Both drugs provide some sedation and are less likely to cause vomiting. They can cause decreased gastrointestinal motility, but less markedly than other opioids. Both drugs can be reversed with naloxone, but this may be difficult as they bind tightly to receptor sites. The analgesia provided is mild and in the case of butorphanol, very short acting (30–60 minutes), so these drugs are only appropriate for short, relatively painless procedures like endoscopy, diagnostic imaging or minor biopsies.

Opioid agonists such as morphine, methadone and fentanyl are better choices for painful or invasive procedures such as an abdominal exploratory laparotomy or oesophageal foreign body removal. Morphine and hydromorphone, when given intramuscularly, usually cause vomiting and ptyalism. If given IV, the incidence of vomiting is dramatically decreased (if giving morphine IV it should be done very slowly to prevent sudden histamine release). Fentanyl given IV is the best choice for any case where risk of vomiting would be detrimental.

All opioid agonists can cause depression of the cardiovascular and respiratory centres and are known to slow gastrointestinal transit time. This drug class provides sedation and excellent analgesia for varying periods of time. All can be given intraoperatively as constant rate infusions and can be quickly reversed with naloxone.

The most common choices for anaesthetic induction are propofol, ketamine/diazepam, and etomidate. Propofol is a sedative-hypnotic that is relatively safe for use in most patients. It does cause transient apnoea and a dose-dependent cardiovascular depression. In cats it is known to cause Heinz body formation following repeated administration. Ketamine/diazepam is readily available and inexpensive. It is safe for use in most patients. Ketamine causes an increase in cardiac contractility, which can lead to an increase in heart rate and blood pressure. Etomidate is an imidazole derivative that has minimal cardiovascular or respiratory effect. It is expensive and tends to be used for extremely critical patients. Etomidate can cause suppression of adrenal functioning and acute haemolysis. Most importantly when considering this agent for gastrointestinally dysfunctional cases - it often causes nausea, retching and vomiting at induction. This side effect can be avoided if the patient is appropriately sedated and if an adequate amount of the drug is used.

Intubation of patients should be done quickly and the cuff of the endotracheal tube checked and sealed immediately. This group of patients is at high risk of regurgitation of stomach contents and it is important to avoid aspiration of any fluid or material. Check the seal on the endotracheal tube again after 15 or 20 minutes as further muscle relaxation usually occurs and can allow additional air/gas/fluid to pass around the endotracheal tube.

Considerations should be made if the patient has any co-morbidity that could make intubation
difficult, such as an oropharyngeal mass or oesophageal foreign body displacing the trachea; in challenging cases, supplies for a tracheostomy should be ready.

Abdominal distention, electrolyte imbalance, and haemorrhage are the biggest complications associated with GI emergencies that most directly impact anaesthetic monitoring. Each obstacle has a string of further difficulties tied to it. Abdominal distention affects cardiac and respiratory function, which in turn affect blood pressure, tissue perfusion, and oxygenation. Electrolyte imbalances affect organ function and cardiac rhythm. Haemorrhage affects cardiac function, blood pressure, and tissue perfusion.

The gold standard for anaesthetic monitoring of GI emergencies would include: pulse oximetry, capnometry, invasive blood pressure, blood gas sampling, and electrocardiography.

Pulse oximetry measures oxygen saturation of haemoglobin. It can give some degree of information about ventilation status and tissue perfusion. The pulse wave can alert an attentive anaesthetist to possible arrhythmias. A pulse-ox monitor can be placed in a number of areas - tongue, toes, ears, vulva, prepuce, or rectally. Pulse oximetry is a very popular monitoring choice for several reasons - it is simple to use, non-invasive, provides quick and constant information, and is relatively inexpensive. However, much of the information given by the pulse-ox must be taken with a grain of salt. There can be discrepancies in the readings given if the tissue where the probe is placed is too dry, dark, or thick. The readings are not always precise in terms of actual arterial oxygenation. The pulse-ox may still read high even though the arterial oxygenation level is falling. It isn't until the arterial oxygenation level has fallen far enough that the pulse-ox will begin to show lower readings.

Abdominal distention can impair cardiac function and impede appropriate ventilation. Mechanical ventilators are often needed for adequate ventilation. Capnometry is a vital monitor in these cases and will give information on the inspired and expired amounts of carbon dioxide. A capnograph can give information on cardiac function, respiratory function, and machine malfunction. The capnometry wave can highlight hypercapnia, hypocapnia, decreased cardiac output, poor pulmonary perfusion, airway obstruction, and anaesthetic system malfunctions. Capnometry is a simple, non-invasive tool that can give the anaesthetist vital information on ventilatory status.

Impaired cardiac function equals hypotension and decreased perfusion. Direct arterial pressure monitoring is the best way to obtain constant, accurate, real-time information about blood pressure. Arterial catheters can be placed in the dorsal pedal, lingual, auricular, or coccygeal arteries. Invasive blood pressure monitoring requires a higher level of skill and slightly more equipment than oscillometric monitoring, but provides a wealth of information. In addition to systolic and diastolic numbers, arterial monitors can highlight volume issues, ventilator induced cardiac depression, and cardiac dysrhythmias. Invasive blood pressure monitoring can often be the first to pick up haemorrhage or hypovolaemia.

Many patients that suffer dehydration from excessive vomiting/diarrhoea or those with a gastric dilation-volvulus may have electrolyte imbalances and/or acid base disturbances. These abnormalities should be corrected before anaesthesia if at all possible. If stabilization is not possible pre-anaesthesia, aggressive fluid therapy with appropriately balanced solutions should begin immediately. Electrolyte
panels and arterial blood gas parameters should be checked regularly during the intraoperative period. If an arterial line is in place, blood sampling is much more convenient.

Respiratory disturbances causing acidosis or alkalosis occur when a patient is hyperventilating (in response to pain, fever, overcompensation with manual/mechanical ventilation) or hypoventilating (as a result of drug administration, CNS trauma, or restricted thoracic movement). Metabolic disturbances causing acidosis or alkalosis occur in response to electrolyte imbalances. Acidosis is common in conjunction with shock, sepsis, pancreatitis, hypoxaemia, and some toxins. Alkalosis commonly occurs in conjunction with vomiting, hypokalaemia, steroid therapy or bicarbonate therapy. Serial blood gas analysis can highlight metabolic abnormalities, assess adequacy of ventilation, and monitor response to treatment.

Cardiac dysrhythmias are extremely common in volvulus cases, abdominal exploratory laparotomy with splenic involvement, and may be seen in patients with severe electrolyte imbalances so ECG monitoring is strongly recommended.

ECGs show electrical activity of the heart and can alert the anaesthetist to arrhythmias and dysfunctions, but in no way tells the level of cardiac output or tissue perfusion. ECGs are easy to use, non-invasive, and can be easily placed before anaesthesia if warranted. ECGs show common dysfunctions that can be linked to electrolyte imbalances, levels of anaesthesia, ventilation issues. Bradycardia is commonly associated with hyperkalaemia, anaesthetic drugs, extreme hypoxia, hypoglycaemia, and vagal stimulation. Tachycardia can be associated with pain, light anaesthetic plane, hypercapnia, hyperthermia, hypoxia, and haemorrhagic/hypovolaemic shock. VPCs are commonly associated with GDVs and splenic manipulation. Arrhythmias are associated with electrolyte imbalances and ECGs can be the first line to alert the anaesthetist to conductive issues.

Serious cases should be recovered and maintained in a critical care unit for continued fluid support and post operative monitoring. Cardiac dysrhythmias are common postoperatively in many surgical cases and ECG monitoring may be necessary. It is also essential to monitor for both electrolytes and acid-base disturbances in the postoperative period. Shock, hypo/hyperkalaemia, acidosis/alkalosis, respiratory impairment, and hypovolaemia can all be consequences associated with gastrointestinal dysfunction. Depending on the severity of the case additional analgesia may be needed. CRIs of fentanyl or morphine-lidocaine-ketamine are often used, as are fentanyl patches and IV or IM doses of opioid analgesics.
# GI MOTILITY AND ILEUS IN THE ICU: SHOULD WE BE WORRIED ABOUT IT?

Søren Boysen, DVM, DACVECC,

University of Calgary, Faculty of Veterinary Medicine, Canada (srboysen@ucalgary.ca)

In general, gastro-intestinal (GI) motility disorders can affect any part of the GI tract, from the oesophagus to the colon. The clinical impact of GI motility disorders in small animal ICU patients is unknown but likely significant. Contributing to the ambiguity of these disorders, particularly ileus, is the lack of evidence regarding the prevalence of these disorders in dogs and cats, controversy over efficacy of GI prokinetic drugs in small animals, and the challenges in clinically diagnosing the conditions. Although oesophageal and colonic motility disorders can occur in hospitalized ICU patients these conditions are more likely to exist prior to the patient being admitted to the ICU, and not as a result of ICU hospitalization. The majority of this presentation will therefore focus on conditions that are more commonly encountered in the ICU and which are associated with hospital interventions, treatments and stresses.

## Etiology of GI motility disorders

GI motility involves a series of complex co-ordinated events that store, grind and propel ingesta through the GI tract in such a way that absorption, fermentation, water reabsorption and elimination of unwanted metabolites can take place. The complex co-ordinated control of GI motility is a function of smooth muscle contraction regulated by myogenic, neural, and hormonal factors (readers are referred to other review articles on the subject). Given the complexity of regulation and co-ordinated efforts responsible for GI motility, there are a number of disorders that can contribute to GI dysmotility.

## Functional small intestinal ileus and delayed gastric emptying

Ileus is defined as a transient cessation or abnormal pattern of gastrointestinal (GI) motility. Some of the more common general causes of ileus include postoperative ileus, dysautonomia, muscular dystrophy, idiopathic pseudo-obstruction (intestinal leiomyositis), viral enteritis and hypothyroidism. Although the exact incidence is unknown in small animal patients, post-operative ileus is the most common ICU cause in human ICU patients, with a prevalence (depending on the definition used) as high as 25% following elective surgery. Principal underlying causes of postoperative ileus in ICU patients are believed to be the result of electromechanical dissociation of the intestinal musculature due to increased sympathetic tone, release of humoral inhibitory factors (catecholamines, vasopressin, endogenous opiates), impaired release of prokinetic hormones (neurotensin, motilin), and/or hypokalaemia. General conditions in both human and canine ICU patients associated with postoperative ileus include anaesthesia, analgesics (particularly opioids), prolonged surgery time, fasting, and surgery induced inflammation.

Postoperative ileus is known to cause vomiting, decreased tolerance of oral diets, prolonged recovery from surgery, and increased morbidity and mortality in human ICU patients. In addition to the discomfort reported in people, post-operative ileus may predispose patients to wound dehiscence, intussusception and pulmonary and thromboembolic complications. Therefore, efforts should be made to rapidly identify the condition and to treat when it is identified. Despite the importance of
recognizing ileus during the postoperative period in people, the veterinary literature is sparse regarding the diagnosis and treatment of postoperative ileus in dogs and cats.

## Diagnosis of Ileus and Delayed Gastric emptying

There are several invasive techniques to evaluate changes in GI motility which include serosal electrodes, strain-gauge force transducers, and wireless motility capsule devices. Scintigraphy is arguably the current gold standard for dogs and cats. Serosal electrodes and strain-gauge force transducers require surgical implantation of electrodes. Wireless motility capsule devices require oral administration and monitoring until they are expelled from the body, which can take several days and tend to be limited to patients > 15 kg. A more practical approach in the hospitalized clinical patient is ultrasound.

## Ultrasound Evaluation of GI Contractions

Transabdominal sonographic techniques have been used in both dogs and people to diagnose changes in GI motility. Abdominal ultrasound is safe and noninvasive and requires minimal patient preparation, making it a practical diagnostic tool in the clinical setting. The normal GI peristalsis in dogs is reported to be 4-5 contractions per minute in the stomach and proximal duodenum and 1-3 contractions per minute in the jejunum. Fasting and stress of hospitalization have been shown to decrease GI motility in dogs and should be considered in ICU patients

## Ultrasound Evaluation of Gastric Emptying Time

In addition to determining the presence and/or absence of GI contractions, qualitative evaluation of GI motility using ultrasonography can also be performed. Ultrasound has been shown to be a reliable and accurate quantitative method to measure emptying of liquids and solids from the stomach. Dogs are gently restrained while standing and the ultrasound transducer is placed in a longitudinal orientation on to the ventral midline, caudal to the xyphoid. Electronic calipers are used to measure the cranio-caudal and ventro-dorsal diameters of the gastric antrum. The antral area is calculated using the software incorporated in the ultrasound machine. Measurements are made at each of the following each time points: 30 min. prior to feeding, then every 20 min. post-prandially for 6 hours. Gastric half-emptying time (50% of AUC), time of maximal antral area, and time at which antral area was reduced by 50% can be calculated. This method is easily applicable to clinical patients but requires the availability of an experienced ultrasonographer.

## Treatment

Therapy of functional, nonobstructive disorders of gastric motility is based on identification and correction of factors contributing to decreased GI motility and promotion of GI motility through environmental changes, dietary modification, and judicious use of prokinetic drugs. Feeding soon after surgery should be implemented unless otherwise contra-indicated. Liquid diets have more rapid gastric emptying than solid foods and are often chosen in early post-operative phases. Medium calorie diets and low-fat diets also been reported to have shorter gastric emptying times. Given there is some evidence to suggest an increased number and smaller size meals may also be helpful in promoting more rapid gastric emptying, consideration of a continuous rate infusion liquid diet may prove beneficial, although there is no clinical evidence to support this theory. Other recommendations include early ambulation, epidural analgesia (decreases the need for systemic opioid analgesia which is often associated with ileus), non-steroidal anti-inflammatory agents and minimally invasive surgery.
If gastric emptying is significantly delayed and a fluid filled stomach is noted, some clinicians prefer to place a nasogastric tube to allow gastric emptying which may relieve patient discomfort, improve gastric motility and decrease the risk of aspiration. Gastric emptying is often used in conjunction with continuous rate nasogastric tube infusions or bolus liquid diet nasogastric tube feeding

The available published evidence on the effect of various prokinetic drugs in healthy dogs and cats is tenuous, while it is almost nonexistent for dogs and cats with functional ileus. Some of the more common prokinetic drugs that have been studied in small animals include metoclopramide, cisapride, erythromycin, azithromycin, and ranitidine.