Upper respiratory tract disease in dogs (Proceedings)

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Upper respiratory tract disease in dogs (Proceedings)

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Nov 01, 2010

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