Upper respiratory tract disease in dogs (Proceedings)

A variety of disorders can affect the upper respiratory tract of dogs; we will focus on the most common, namely laryngeal paralysis, brachycephalic syndrome and tracheal collapse.

Laryngeal paralysis

Signalment:

      - middle-aged to older, large-giant breed dogs

      - males > females in most studies

Etiology:

      - denervation of the recurrent laryngeal nerve results in atrophy of the cricoarytenoideus dorsalis muscle which prevent abduction of the arytenoids cartilage leading to airway obstruction

      - most dogs are bilaterally affected

      - congenital in certain breeds:

           o Siberian Husky

           o Dalmatian

           o Rottweiler

           o Bull Terrier

           o Bouvier des Flandres

      - acquired:

           o Idiopathic (most commonly)

           o Trauma (including surgery)

           o Diffuse neuromuscular disease (MG, polyneuropathy, polymyopathy)

           o Neoplasia

           o Hypothyroidism

Clinical signs:

      - Consistent with upper airway disease and include:

      - Stridor

      - Exercise intolerance

      - Voice change

      - Ptyalism

      - Upper airway obstruction in severely affected dogs (cyanosis, gagging, retching, collapse)

Diagnosis:

      - laryngeal examination:

           o either direct visualization or laryngoscopy

           o generally requires anesthesia, however transnasal laryngoscopy without anesthesia has been described

           o lack of abduction of arytenoid cartilages is diagnostic

           o anesthetic drugs may confounded evaluation of laryngeal function

           o thiopental may have the least effect on laryngeal function

           o doxopram may facilitate the diagnosis in dogs that are not breathing well after induction of anesthesia

      - rule out underlying and concurrent diseases:

           o screening CBC, biochemistry and TT4+TSH

           o thoracic radiographs (3 view 'met check')

           o thorough neurologic examination

Treatment:

      - medical management:

           o avoidance of stress, excitement and increased environmental temperatures

           o symptomatic management of upper airway obstruction in the setting of an acute crisis:

               ■ sedation (usually acepromazine)

               ■ cooling (if hyperthermic)

               ■ temporary anesthesia and intubation if necessary

           o treatment of underlying and concurrent diseases (e.g. MG, hypothyroidism etc.)

      - surgical management:

           o unilateral arytenoid lateralization ("tie-back") performed most commonly since it is associated with shortest surgical time, lowest complication rates and best overall survival time

           o variety of other surgical procedures have been evaluated

           o post-operative complications are common and include:

               ■ aspiration pneumonia ***** most commonly ******

               ■ continued respiratory distress

               ■ megaesophagus

               ■ vomiting

               ■ failure of surgical repair

               ■ seroma formation at the surgical site

               ■ unresolved coughing and/or gagging

               ■ persistent exercise intolerance

Brachycephalic syndrome

Definition:

      - brachycephalic syndrome describes a combination of primary and secondary anatomic abnormalities of the upper airways of brachycephalic breeds, that results in upper airway dysfunction and obstruction

Pathophysiology:

      - primary abnormalities include:

           o stenotic nares

           o elongated soft palate

           o enlarged tonsils

      - secondary abnormalities include:

           o everted laryngeal saccules

           o laryngeal collapse; and

           o tracheal collapse

      - secondary abnormalities result from the increase in negative pressure in the airways that is generated in order to overcome the increased resistance to airflow through the upper airways

      - inflammation, swelling and edema often exacerbate clinical signs

Diagnosis:

      - based on visual examination of the nares and evaluation of the oropharynx under light anesthesia (pre-oxygenate, rapid induction, etc.)

      - cervical and thoracic radiographs

Treatment is surgical:

      - widening of the stenotic nares

      - soft palate resection (now most commonly done with laser)

      - resection of everted laryngeal saccules

      - tonsillectomy

      - management of laryngeal and tracheal collapse as necessary

Tracheal Collapse

Signalment:

      - toy breed dogs, most commonly Yorkshire Terriers

Clinical Signs:

      - Cough

           o Harsh, goose-honking

           o Precipitated by excitement and exacerbated with tracheal palpation

Diagnosis:

      - lateral thoracic radiographs

      - fluoroscopy

      - tracheoscopy

Treatment:

      - depends on the severity of clinical signs, concurrent disease and location of tracheal collapse

           o medical management:

           o anti-tussives

           o stress reduction

           o avoiding tracheal pressure (e.g. Switch to chest harness instead of neck leads)

           o weight loss

      - surgical management:

           o indicated when dogs fail to respond to medical management

           o intraluminal self-expanding wall stents used most commonly for thoracic inlet and intrathoracic collapse

           o extraluminal tracheal rings used most commonly for cervical collapse

References available upon request.