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.

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