Page 646 - WSAVA2018
P. 646

 25-28 September, 2018 | Singapore
Moderate to severely affected patients or patients with multiple defects may present with cyanosis and/or syncope.
Physical examination: Physical examination is generally normal except for patients with stenotic nares. In patients with stenotic nares the wings of the nostril (i.e., dorsolateral nasal cartilage) obstruct airflow resulting
in turbulent airflow and resultant noise.Examining the patient after exercise may exacerbate clinical signs (i.e., noise and exercise intolerance) making diagnosis of brachycephalic syndrome more likely. Oral examination of the awake patient is generally unrewarding as the laryngeal apparatus and related abnormalities cannot be seen without light general anesthesia.
Radiography: Diagnosis of brachycephalic syndrome is based on signalment, history, physical examination, and direct visualization of the laryngeal apparatus with the patient under light general anesthesia. Thoracic radiographs are generally recommended to rule out lower airway disorders such as tracheal hypoplasia and pulmonary abnormalities.
Differential diagnosis: Any disorder causing noisy respirations, exercise intolerance, cyanosis, and syncope. Included are laryngeal mass, laryngeal collapse and laryngeal paralysis.
Medical management: Medical management is directed at decreasing airway turbulence and subsequent inflammation and edema. Strict confinement, antiinflammatory medications (e.g., steroids, NSAIDS), and a cool environment are recommended. Obese patients should be placed on a weight reduction diet plan. As medical management does nothing to change the anatomic deformity of the disorder, it is considered palliative but not curative.
Surgical treatment: The objective of surgical treatment is to provide an adequate airway by relieving any anatomic obstruction.
Preoperative management: Use of anti-inflammatory medication preoperatively is generally recommended. Patients are given intravenous steriods (dexamethasone 0.5 - 1 mg/kg IV) at the time of anesthetic induction.
Anesthesia: Anesthetic management is somewhat dependent upon the severity of clinical signs at presentation and degree of airway abnormality.
Patients with mild signs may be anesthetized with
the clinicians standard anesthetic protocol. Careful evaluation of the laryngeal apparatus is performed prior to intubation and while the patient can still breath on its own (i.e., light general anesthesia). Laryngeal function is carefully evaluated during inspiration and expiration.
Patients with moderate clinical signs may need to be preoxygenated prior to induction. Induction should be
performed quickly, the laryngeal anatomy and laryngeal function examined thoroughly, and the patient intubated to establish an open airway.
Patients with severe clinical signs should be preoxygenated 5 to 10 minutes prior to induction. A vagolytic agent (i.e., atropine) should be considered 10 to 15 minutes prior to induction because vagal tone is generally increased and cardioinhibitory reflexes are enhanced. Induction should be quick, examination of the laryngeal anatomy and function performed, and the patient intubated to establish an open airway.
Laryngeal examination: Once the patient is under a light plain of anesthesia laryngeal function is evaluated. Care is taken to observe for evidence of laryngeal collapse, elongated soft palate, and everted laryngeal saccules.
Surgical anatomy: The soft palate in the dog forms a long and broad movable partition between the oral and nasopharynx. The cranial border is attached to the bony palate; the caudal margin forms the dorsal border of the opening from the mouth into the pharynx. This portion of the palate is in contact with the epiglottis during normal inspiration; during deglutition, the epiglottis moves
away from the soft palate to protect the opening of the glottis. At the same time the soft palate moves dorsally to close the nasopharynx and prevent regurgitation of material into the nasal cavity. The dorsal nasopharyngeal surface has a mucous membrane lining continuous with that of the nasal cavity and a slightly convex contour. The mucous membrane of the ventral concave surface is a continuation of the lining of the hard palate and is referred to as the oral surface of the soft palate.
Relevant pathophysiology: Protrusion of an elongated soft palate into the laryngeal inlet during respiration significantly obstructs air passage into the glottis. Stenotic nares, when present, contribute to the severity of the occlusion by increasing the inspiratory effort (and subsequent negative pressure) thus drawing the soft palate deeper into the larynx. Edema and inflammation result from friction against the epiglottis during each respiration. The resultant thickening further lessens airflow. As increased inspiratory effort continues, increased negative pressure in the airway encourages laryngeal saccules to evert.
Positioning: Patients may be positioned in ventral or dorsal recumbancy.Stenotic nares: The author prefers ventral recumbancy with the head supported on towels so the head position is normal and functional.
Elongated soft palate and everted saccules: Patients can be operated in either ventral or dorsal recumbancy. In dorsal recumbancy, the maxillary canine teeth are taped securely to the operating table. The mandibular canine teeth are taped to an ether stand situated
over the patients head. The mouth is opened wide to enhance visualization. This positioning is critical as oral

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