Monthly Journal Round-Up - July/August 2018

Thanks as always to Lara Brunori DVM CertAVP MRCVS

Clinical review:

  • Nafe, L.A. et al. (2018) ‘Aspiration-related respiratory disorders in dogs’ Journal of the American Veterinary Medical Association, 253(3), pp. 292-301. See below.

Clinical studies:

Prospective:

  • Darnis, E. et al. (2018) ‘Establishment of reference values of the caudal vena cava by fast‐ultrasonography through different views in healthy dogs’. Journal of Veterinary Internal Medicine, 32(4), pp. 1308-1318.

  • Hogen, T. et al. (2018) ‘Evaluation of end‐tidal carbon dioxide as a predictor of return of spontaneous circulation in dogs and cats undergoing cardiopulmonary resuscitation’. Journal of Veterinary Emergency and Critical Care (Early view).

Retrospective:

  • Skulberg, R. et al. (2018) ‘Description of the Use of Plasma Exchange in Dogs With Cutaneous and Renal Glomerular Vasculopathy’. Frontiers in Veterinary Science, https://doi.org/10.3389/fvets.2018.00161

  • Ohad, D.G. et al (2018) ‘Constant rate infusion vs. intermittent bolus administration of IV furosemide in 100 pets with acute left-sided congestive heart failure: A retrospective study’. The Veterinary Journal, 238, pp.70-75.

  • Ruiz, M.D. et al. (2018) ‘Characterization of and factors associated with causes of pleural effusion in cats’. Journal of the American Veterinary Medical Association, 253(2), pp. 181-188.

  • DePompeo, C.M. et al. (2018) ‘Intra-abdominal complications following intestinal anastomoses by suture and staple techniques in dogs’. Journal of the American Veterinary Medical Association, 253(4), pp. 437-443.

  • Lux, C.N et al. (2018) ‘Factors associated with survival to hospital discharge for cats treated surgically for thoracic trauma’. Journal of the American Veterinary Medical Association, 253(5), pp. 598-605.

  • Walton, K.L. & Otto, C.M. (2018) ‘Retrospective evaluation of feline rodenticide exposure and gastrointestinal decontamination:146 cases (2000-2010)’. Journal of Veterinary Emergency and Critical Care (Early view).

Case series:

  • Teh, H. et al. (2018) ‘Medical management of esophageal perforation secondary to esophageal foreign bodies in 5 dogs’. Journal of Veterinary Emergency and Critical Care (Early view).

Case reports:

  • Bellamy, E.J. & Steele, H. (2018) ‘Abdominal wall rupture with gastric herniation in an 8‐week‐old puppy’. Journal of Small Animal Practice (Early view).

For a copy of any of the papers mentioned in this post (personal education purposes only), please email lara.brunori@gmail.com.

Pick of the Month

‘Aspiration-related respiratory disorders in dogs’

Nafe, L.A. et al. (2018) Journal of the American Veterinary Medical Association, 253(3), pp.292-300

Aspiration is defined as the intake of solid or liquid material into the airways and pulmonary parenchyma. The term aspiration is often used interchangeably with aspiration pneumonia, however other aspiration-related respiratory disorders exist and have been well characterised in human medicine.

This paper offers a comprehensive overview of all aspiration-related disorders involving canine patients based on the parallels recognised in human medicine.

An anatomical approach has been adopted to classify these disorders:

Airways

Upper-airway disorder secondary to gastroesophageal reflux (GER)

Repeated micro-aspiration of gastric contents in the upper airways can result in oropharyngeal, nasopharyngeal, laryngeal and proximal tracheal inflammation.

In humans clinical signs of reflux (heartburn, belching and nausea) in combination with visible evidence of laryngeal or oropharyngeal inflammation are often enough to make a diagnosis and institute treatment.

In dogs, however, diagnosis can prove challenging. Laryngeal dysfunction and hyperaemia are unspecific signs amongst the canine population and GER can act both as a cause and a consequence in the perpetuation of laryngeal disease.

Therapeutic trials with proton pump inhibitors resolving upper respiratory signs have been considered diagnostic for laryngeal dysfunction secondary to GER in dogs.

Alternatively, CT examination of the head often shows thickening of the soft palate without evidence of a nasal or nasopharyngeal mass and tracheoscopy might reveal a specific demarcation between an hyperaemic proximal tracheal region and a normally appearing mucosa in the distal portion.

Large airway obstructions

These are usually due to a foreign body inhalation and can represent a potentially life threatening situation. Common foreign bodies in dogs include food, plant material and various chewed objects.

Radiography can be a useful diagnostic tool, however its sensitivity is impaired when the aspirated object is radiolucent.

Evidence of atelectasis and air trapping in the lung tissue could be additional indicative findings. CT scan, although not always readily available provides a more reliable option.

Tracheoscopy with a flexible endoscope is likely the most effective diagnostic and therapeutic tool applicable in these situation. The foreign body can usu-ally be easily identified and subsequently removed via the additional use of alligator forceps.

Bronchiectasis

This is a structural change affecting the elastic and muscular components of the bronchi which leads to an irreversible widening of the airways. In dogs, aspiration pneumonia has been shown to be the most likely underlying cause of this pathological process.

Diagnosis can be achieved via thoracic radiography, CT and bronchoscopy. X-rays typically show a multifocal unstructured interstitial pattern with thickened bronchial walls and bronchi with a wide diameter that does not taper down to the periphery. CT scan provides a superior sensitivity and in some circumstances can even identify the presence of a well-circumscribed foreign material within a bronchus.

Other differentials for bronchiectasis are bacterial infections, eosinophilic infiltrate and ciliary dyskinesia.

Diffuse aspiration bronchiolitis (DAB)

DAB represents a chronic inflammation of the small airways caused by re-current aspiration. Diagnosis include the identification of a predisposing factor (i.e. megaesophagus) and the evidence on CT scan of bilateral diffuse bronchiolocentric lesions.

Since there are no available therapies able to specifically address small airway inflammation, treatment is focused on addressing the underlying causes.

Parenchyma

Aspiration pneumonia and pneumonitis

Aspiration pneumonia is the most commonly recognised pathological manifestation of aspiration disorders in veterinary medicine.

In human medicine there is an interesting distinction between aspiration pneumonia and aspiration pneumonitis.

The first one involves a bacterial infection and it’s usually associated with the aspiration of high pH (>2.5) material containing bacteria from the oropharyngeal or upper gastrointestinal tract. It has a slow and progressive development and it’s associated with a chronic predisposing condition (i.e. laryngeal paralysis).

Aspiration pneumonitis on the other hand is characterised by an hyperacute onset of hypoxia, pyrexia and radiographical changes occurring within hours from a major aspiration event. This presentation is due to the inflammatory reaction associated with the chemical damage caused by the aspirated material and it’s independent from bacterial infections.

This distinction in veterinary medicine is still not clearly recognised. How-ever the more extensive use of CT scans might enhance the specificity of diagnosis and could consequently help implementing more adequate treatments. This is particularly relevant in regards of a more cautious use of antimicrobials. Aspiration pneumonitis in humans is treated mainly with supportive care measures and does not require any antimicrobial interventions.

Acute respiratory distress syndrome (ARDS)

A recognised common consequence of aspiration pneumonitis in humans is ARDS. This is a syndrome defined by an acute onset of impaired gas exchanges and pulmonary vessels leakage without pulmonary hypertension. The radiographical evidence of bilateral infiltrates involving more than one lobe/quadrant is usually considered as a diagnostic confirmation.

This syndrome carries an extremely high mortality with pulmonary protective ventilation identified as the only therapeutic option.

Exogenous lipid pneumonia

This is very rarely described in veterinary medicine and it occurs when there’s inhalation/aspiration of animal, vegetable or mineral oil. Usually the history is quite indicative and radiographically it shows as a patchy pneumonic consolidation. Cytological evidence of lipid-laden macrophages is considered the definitive diagnostic evidence.

Interstitial lung diseases

This is a group of inflammatory disorders affecting the space between the pulmonary and vascular epithelium. Repetitive micro-aspiration is a recognised cause for this presentation in human medicine. In veterinary medicine this cause-effect relationship is still under investigation. However, if confirmed treatment at-tempts to reduce chronic micro-aspiration could prove very useful in slowing down the inevitable decline in lung function connected with these diseases.

Conclusion

In conclusion aspiration can result in a broad range of clinical presentations. A better understanding of the types of aspiration-associated respiratory disorders in dogs will improve early recognition, optimise therapeutic protocols and provide better clinical outcomes.

For a copy of any of the papers mentioned in this post (personal education purposes only), please email lara.brunori@gmail.com.

Lara loves to hear from you!

Pause, notice...and accept

Pause, notice...and accept.jpg

In our previous blogs we have discussed how wellbeing can be seen as a foundation on which we can build; a strong basis to help us to move towards fulfilment and achievement. 

By prioritising our physical and emotional wellbeing, as well as our happiness, we establish a springboard from which we can learn to thrive and succeed. As the first stage in this process, we have previously discussed the importance of ‘being’ and how we can overcome our ‘automatic pilot’ by simply pausing and consciously observing how we feel. This allows us to notice and acknowledge our physical and mental state in any given moment. 

Acknowledgement alone can be a great tool and can have an immediate effect on how we feel. But more significantly, it is an essential first step towards acceptance.

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Acceptance may be something that we try to avoid. Because sometimes, to accept can feel as though we have somehow given up and any hope of change has ceased to exist. But the reality is quite the opposite. Acceptance is actually the precursor for change and helps to reduce anxiety and improve self-esteem by appreciating ‘what is’ without judgement, especially of ourselves.  

Acceptance in this way can apply to many moments within our lives – both the big and the small. Seemingly small day-to-day issues such as irritation towards another road user as you navigate your journey to work or frustration as a result of running late might seem like just ‘one of those things’. You may not give it another thought.  But what could the alternative look like? Noticing, acknowledging and accepting feelings such as these is an opportunity to better understand our reaction in these moments. This helps to prevent any resulting feelings from negatively impacting our health and wellbeing. 

Acceptance can also apply to bigger issues that might be affecting us. For example, if we believe that we haven’t been looking after our body (we haven’t been paying attention to our diet, not exercising, relying on alcohol or substances for example), we may find ourselves either holding onto the judgemental feelings we have about ourselves, or repressing them altogether. However, by consciously acknowledging the issue, addressing it with kindness and allowing ourselves to accept the situation, we are far better placed to move forwards.

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And so, the big question is how do we help ourselves to be more accepting? Would it seem too simple if we said you begin by simply giving yourself permission? Whilst this might sound obvious, how often do we really take a moment to notice how we are feeling and (either silently or aloud) acknowledge that feeling along with a confirmation that it’s OK to feel that way. This conscious process is the starting point. It is fundamental to helping us to be OK in the present moment. 

And there are additional techniques which can further complement the practice. Emotional Freedom Technique (see here for more information), mindfulness training and guided meditation are good examples of other ways which can provide a basis for non-striving, non-judging acceptance. For further information on any of these and for further advise, please contact any of the VetLed team using the details below.

The great news is that improving your ability to notice, acknowledge and accept can better your sense of peace and wellbeing. The even better news is that it doesn’t end there. With acceptance comes a clarity and sense of freedom from which we can form an intention and a motivation to make change. This might mean, for example, that we become better able to accept former lifestyle habits and can now more objectively understand what we can change that might improve our health, without the burden of judgement or regret. An acceptance for ‘what is’ allows you to approach the next steps with kindness, curiosity and optimism. 

And anything done with kindness, curiosity and optimism is always good medicine for the mind, body and soul. 

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About VetLed

VetLed was founded to provide support to veterinary professionals who are faced with significant challenges every day. The VetLed team believe that creating a compassionate and professional workplace culture that puts people wellbeing and patient safety at the core of everything we do, will in turn, improve animal and people welfare. The VetLed performance approach supports veterinary professionals to maximise their own wellbeing and to fully utilise their skills to deliver optimal patient care. You can contact VetLed by emailing info@vetled.co.uk

Drowning Refresher

By Lisa Murphy DACVECC

Pathophysiology

Once the airway is below the surface of a liquid voluntary breath-holding occurs. This is then followed by involuntary laryngospasm as liquid enters the oropharynx and larynx. During both of these periods, the victim is not breathing gas and develops hypercapnia, hypoxaemia and acidosis. Once the arterial oxygen partial pressure drops sufficiently, laryngospasm stops and liquid is then actively aspirated. It is the hypoxaemia which leads to unconsciousness and apnea. 

Once aspirated, water leads to several severe side effects:

  • One of the most significant is surfactant dysfunction and washout which reduces lung compliance and leads to atelectasis.
  • Water also interferes with the normal osmotic gradient in the alveolar-capillary membrane thus directly injuring the pulmonary epithelium. Damage to these cells has several effects including the release of inflammatory mediators and increased membrane permeability worsening fluid accumulation in the lung parenchyma.

It was once believed that the type of water (salt versus fresh water) was a more important determinant of outcome than the volume aspirated, however, more recent studies have found this to be untrue. This is because it’s the volume of water which affects surfactant function regardless of the type aspirated. Pool water is interesting because it typically contains agents to limit bacterial growth so secondary pneumonia is uncommon with this type of aspiration. 

The temperature of the water aspirated can also play a role in survival. Cold water is associated with higher rates of survival. This is because it reduces cellular metabolism (and thus oxygen consumption) and activates the diving reflex (leading to bradycardia, hypertension, shunting of blood to the cerebral and coronary circulations). 

Diagnosis 

The history of a drowning episode is usually known. Common tests performed in these cases include:

  • Blood gas analysis (ideally arterial) – most cases have a mixed respiratory and metabolic acidosis
  • Thoracic radiography:
    • Pulmonary oedema is likely
    • In some cases, where the volume of water aspirated wasn’t large but they suffered a choking-like episode, non-cardiogenic pulmonary oedema (NCPO) may be identified. This is suspected where the pulmonary oedema is predominantly in the caudodorsal lung field.
    • In cases which don’t go on to develop pneumonia, there is usually radiographic resolution of oedema within 7-10 days.

Treatment

The focus should be on controlling the patient’s hypoxaemia.
The risk of pneumonia is low (estimated at 12% in humans) so empirical antibiotics are not recommended. In general, it is much more likely for these cases to develop pneumonia if they undergo mechanical ventilation.
Steroids also have not been shown to increase survival and their use is not recommended. 

Similarly, there is little evidence supporting the use of diuretics in cases of NCPO. Diuretics are most useful for hydrostatic oedema which is associated with congestive heart failure. In cases of NCPO, the oedema is due to changes in pulmonary epithelium permeability (permeability oedema). Fluid can still leak into the parenchyma despite diuretic use. And since diuretics have systemic effects, they put patients at risk of dehydration and potential renal compromise. 

There are several criteria that we can use to help identify those patients who could benefit from mechanical ventilation. The main indications are as follows:

  • Arterial partial pressure of carbon dioxide > 60 mmHg
  • Arterial partial pressure of oxygen < 60 mmHg despite non-invasive oxygen supplementation 
  • Excessive respiratory effort with impending respiratory fatigue

Prognosis is not known in veterinary medicine. In general, animals showing more organ systems negatively affected and those requiring positive pressure ventilation have a worse prognosis.