Veterinary Voice, June 2016 – Brachycephalic Airway Syndrome

Cassie Prpich, BVSc, MANZCVS (Internal Medicine), DACVS-SA
Fellow of Surgical Oncology
 

Brachycephalic airway syndrome (BAS) consists of both primary and secondary components. The three primary components are elongated soft palate, stenotic nares and hypoplastic trachea (most often seen in English Bulldogs). Secondary components occur due to chronic subatmospheric pressure in the airway that is generated to overcome increased resistance to airflow and include everted laryngeal saccules and laryngeal collapse.
 
Clinical Signs

Most dogs with brachycephalic airway syndrome have a history of stertorous breathing, especially on inspiration. Respiratory signs are often worse in hot or humid weather and after exercise. Some brachycephalic dogs present in acute respiratory distress with cyanosis or collapse.
 
A proportion of brachycephalic dogs also have a history of gagging or retching. These gastrointestinal signs can develop as a result of hiatal hernias, gastroesophageal reflex and esophagitis that can occur due to subatmospheric intrapleural pressures that are needed to overcome chronic partial upper airway obstruction.
 
Emergency Management

Emergency treatment for brachycephalic dogs involves oxygen supplementation, sedation with acepromazine +/- butorphanol, dexamethasone and cold IV fluids, taking care to minimize stress when placing an IV catheter.
 
Supplies for intubation should be at hand in case the patient continues to decompensate.
 
Diagnosis

Pre-operatively, the nares can be evaluated during routine physical examination. Thoracic radiographs should be performed to evaluate for hypoplastic trachea, as well as evidence of aspiration pneumonia, pulmonary edema or cardiac disease.
 
Evaluation of the soft palate, saccules and larynx requires general anesthesia and is usually performed under the same anesthetic episode as corrective surgery. A diagnosis of elongated soft palate is made when the soft palate extends past the tip of the epiglottis. To evaluate the saccules, the endotracheal tube needs to be temporarily removed – if everted, the saccules will be seen protruding medially and laterally, just caudal to the vocal folds. Laryngeal collapse, if present, is typically graded as follows;
 
Stage I: Laryngeal saccule eversion
Stage II: Medial displacement of the cuneiform process of the arytenoid cartilage
Stage III: Collapse of the corniculate processes, resulting in loss of the dorsal arch of the rima glottidis and subsequent airway obstruction

 

Surgical Treatment

Surgical treatment is recommended in patients as young as 6 months of age to try and prevent the development of secondary components of the syndrome, which are often far more difficult to treat.
 
Stenotic Nares

The most commonly performed techniques used to treat stenotic nares are;
1) Alar wing amputation “Trader’s technique”
A #11 scalpel blade is placed in the dorsal aspect of the nares with the blade facing ventrolaterally. The ventral alar wing is then amputated in a single incision and pressure is applied for 5-10 minutes to control hemorrhage. The wound is then allowed to heal via second intention.
2) Punch resection
A 2 – 6mm punch is inserted into the tissue of the rostral aspect of the nasal wing. After twisting the punch, the tissue is excised with Metzenbaum scissors. The size of punch is chosen to allow 2-3mm of tissue for suturing with simple interrupted suture.
3) Wedge resection
A lateral, horizontal or vertical wedge can be removed from the dorsolateral nasal cartilage with a #11 blade, ensuring that the overlying mucosa and epithelium is also excised. The wound is then closed with interrupted sutures
 
Elongated Soft Palate

The ideal level of resection of the soft palate is in line with the caudal border of the tonsillar crypts. Palate resection can be achieved using Metzenbaum scissors, a laser or a vessel-sealing device. For all techniques, it is helpful to retract the soft palate rostrally by placing stay sutures or Allis tissue forceps at the caudal edge of the palate on midline.
 
Scissor resection is performed with Metzenbaum scissors and suturing begins laterally using 3-0 or 4-0 monofilament rapidly dividing suture, apposing the nasal and oral epithelium. Laser and bipolar vessel-sealing devices typically do not require suturing.
 
Laryngeal changes

Everted laryngeal saccules can be removed at their base with Metzenbaum scissors and are then allowed to heal via second intention.
 
Stage II and III laryngeal collapse have a poor prognosis. Treatment typically involves aggressive medical management first with weight loss, exercise modification and glucocorticoids to decrease airway swelling. If signs are progressive then a permanent tracheostomy is usually required. A laryngeal tie back may be attempted but outcomes in dogs with laryngeal collapse have not been evaluated.
 
Peri- and post-operative care

Glucocorticoids are administered immediately pre- or peri-operatively (typically dexamethasone .05 – .1mg/kg IV) to minimize post-operative swelling. Anti-emetics can be started pre-operatively (I typically use metoclopramide CRI 1-2mg/kg/day) to limit gagging and vomiting.
 
Animals are typically recovered in oxygen or with oxygen therapy if an oxygen cage is not available. As should be the case with all brachycephalic anesthetic episodes, the endotracheal tube is left in place for as long as tolerated. It is important to ensure that patients are kept calm after the procedure to avoid further aggravation of swelling. If necessary, sedation with acepromazine +/- butorphanol is used to achieve this.
 

Patients are kept NPO for 12-24 hours and are initially offered small amounts of soft food and water under supervision. If there were any pre-existing gastrointestinal signs, these should be managed post-operatively with appropriate drugs (omeprazole / famotidine / sucralfate as needed).
 
Equipment for emergency re-intubation and/or temporary tracheostomy should always be available and nearby in the post-operative period. Typically the need for tracheostomy is greater in patients that are having multiple airway procedures and sacculectomy. If required, the temporary tracheostomy is usually left in place for 48 hours to allow time for resolution of swelling.
 
Prognosis

The prognosis for dogs after soft palate and nares resection is good to excellent in 90% of cases. The prognosis for laryngeal collapse is generally poor but aggressive medical management can be successful in some patients.

 
PRACTICE POINTS;

1) Primary conditions in BAS include stenotic nares, elongated soft palate and hypoplastic trachea. Secondary conditions in BAS include everted laryngeal saccules and laryngeal collapse.
2) Treatment of the primary components at a young age is recommended to try and limit development of secondary conditions, which are harder to treat.
3) A proportion of brachycephalic dogs also have gastrointestinal signs that will benefit from treatment in the pre- and post-operative period.
4) Emergency treatment consists of oxygen therapy, sedation (acepromazine +/- butorphanol), glucocorticoids and cold IV fluids.
5) The prognosis for soft palate and nares resection is good to excellent in 90% of cases. The prognosis for laryngeal collapse is generally poor but aggressive medical management can be successful in some patients.

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