Brachycephalic airway syndrome (Proceedings)

Disorders of the upper airway occur commonly in brachycephalic breeds of dogs. Chief client complaints include excessive respiratory noise, reduced exercise tolerance, heat intolerance, and dyspnea. Cyanosis also may be observed. Since multiple airway abnormalities may occur in the same dog, a systematic approach to patient evaluation is essential for proper management. Brachycephalic breeds with upper airway disorders present both anesthetic and surgical challenges to the veterinarian. The diagnosis and management of the following upper airway disorders are reviewed: stenotic nares, elongated soft palate, everted laryngeal saccules, and hypoplastic trachea.

Patient evaluation

Evaluation of the patient with upper airway disorders should include a thorough history, physical examination, radiographic examination, and pharyngoscopic, laryngoscopic and tracheoscopic evaluation of the anesthetized patient. The frequency, severity, and pattern of occurrence of dyspnea should be noted. The occurrence of cyanotic episodes usually indicates more severe abnormalities.

Physical examination focuses on the cardiopulmonary systems, yet does not exclude other body systems. External nares are inspected, and their function is evaluated. Observing the dog at rest and breathing with a closed mouth will help determine if air can be moved effectively through the nose. Placing a clean microscope slide in front of the nares with the animal breathing through the nose will also provide an estimate of air flow through each nostril. Auscultation of the thorax and upper airway should be performed.

Lateral cervical radiography emphasizing soft tissue detail may help delineate an elongated soft palate. Pharyngoscopy, laryngoscopy, and tracheoscopy should be performed in the anesthetized patient.

Presurgical management

Anesthesia in the brachycephalic breeds requires diligent preanesthetic preparation and attentiveness to detail during and after anesthesia. Points of emphasis include avoiding regurgitation or vomition, providing preanesthetic oxygenation, rapidly inducing anesthesia, gaining rapid control of the airway, and administering one dose of corticosteroid preoperatively.

Regurgitation is commonly observed following general anesthesia administration in brachycephalic breeds, particularly after pharyngeal or laryngeal surgery. Regurgitation poses two risks to the animal: aspiration pneumonia and reflux esophagitis. Postanesthetic regurgitation seems to be reduced by withholding food from the dog for at least 18 to 24 hours prior to anesthesia. Water is usually withheld for 4 to 6 hours before surgery, also. The use of preanesthetic metaclopramide (0.2-0.4 mg/kg, SQ) may have beneficial effects on reducing the incidence of postanesthetic regurgitation.

Use of a corticosteroid (e.g., dexamethasone, 0.1-0.2 mg/kg, IV or SQ) immediately prior to pharyngeal or laryngeal surgery in the brachycephalic dog may reduce postoperative swelling. Such practice seems to improve ventilation in the immediate postoperative period.

Anesthesia

Oxygen (5 L/minute) should be administered via face mask or rebreathing hose to dogs that do not resist its delivery for at least 5 minutes immediately prior to anesthetic induction. Anesthesia should be rapidly induced with an injectable agent (either thiobarbiturate or narcotic), to enable rapid and atraumatic endotracheal tube placement. Brachycephalic breeds are not good candidates for the use of inhalation anesthetics as induction agents, because they can develop significant difficulties before the endotracheal tube is positioned. Adequate laryngoscopic viewing is usually necessary to efficiently position the endotracheal tube. Choice of endotracheal tube size (diameter and length) should reflect the size of the trachea and the length of cervical region. Excessively large and/or long tubes should be avoided. When properly placed, the endotracheal tube should extend from the tip of the nose to the thoracic inlet and be slightly smaller than the tracheal diameter. After minimally inflating the endotracheal tube cuff, the tube is secured with a section of roll gauze placed and tied behind the animal's head. Endotracheal intubation is maintained as long as possible during recovery from anesthesia.

Diagnosis

The presence of the following conditions is determined.

Stenotic nares

Diagnosis of stenotic nares is made by physical examination. Reduced air flow through the stenotic nostrils is noted when the dog is closed mouth breathing. Reluctance to breathe through the nose may also be noted. Nares may be mildly, moderately, or severely deviated medially. Affected dogs often are restless and anxious, especially when restrained.

Elongated soft palate

An elongated soft palate usually produces signs of excessive respiratory noise, particularly when the animal is sleeping. The redundant soft tissue in the pharynx vibrates during inspiration and expiration, producing noise. Definitive diagnosis of elongated soft palate is made following pharyngoscopic evaluation. An elongated soft palate extends more than 3 mm caudal to the tip of the epiglottis. The elongated soft palate often is thickened and has an inflamed tip.

Everted laryngeal saccules

Everted laryngeal saccules are a secondary disorder of the upper respiratory tract. Everted saccules produce excessive noise with possible dyspnea, primarily on inspiration. This abnormality is thought to develop due to the generation of strong negative intra-laryngeal pressures during inspiration. Everted laryngeal saccules may accompany any or all of the other upper respiratory disorders. History is often not particularly helpful in presumptively diagnosing everted laryngeal saccules, although recent evidence of exercise or heat intolerance may be noted. Laryngoscopic examination in the anesthetized patient will reveal redundant mucosa just rostral to the vocal folds near the floor of the larynx. Everted saccules are usually white and glistening and obscure the vocal folds. Their prominence may vary with the degree of inspiratory effort. The laryngeal opening will be noticeably smaller, particularly at its ventral aspect.

Hypoplastic trachea

Hypoplastic trachea is observed fairly commonly in Bulldogs and other brachycephalic breeds. If the trachea is severely hypoplastic, the animal's respiratory function may be almost continuously compromised. Diagnosis is made following lateral cervicothoracic radiographs and/or tracheoscopy.

Management

Stenotic nares

Surgical repair of stenotic nares involves the excision of a portion of the lateral alar fold and approximation of the adjacent tissues. A vertical (or elliptical) wedge of tissue is excised from each lateral alar fold. Hemorrhage is controlled with local pressure and reapposing the wound edges. Simple interrupted or mattress sutures (e.g., 3-0 poliglecaprone 25) are placed to enlarge the size of the nostril.

Elongated soft palate

An elongated soft palate is repaired via an oral approach. A properly placed mouth gag and slight elevation of the patient's head assist the surgery. A soft palate is considered to be elongated if its free end extends beyond the caudal aspect of the palatine tonsils. Alternately, the end of the soft palate should not interfere with the movement of the epiglottis. Excision of the redundant portion of the soft palate is performed after stay sutures are placed in its lateral edges. These stay sutures help minimize trauma to the tissues and serve to guide the line of excision. Metzenbaum scissors are used to incise part of the soft palate starting laterally and proceeding medially. After about one-half of the width of the soft palate has been incised, sutures are placed in the incised edge of the palate. A synthetic absorbable suture (e.g., 4-0 polydioxanone) is placed in a simple continuous pattern to unite the oral and nasal pharyngeal mucosa over the incised edge. The remainder of the width of the soft palate is incised, the redundant portion of the palate is discarded, and the closure is completed. Accuracy of excision is verified prior to the removal of the stay sutures and mouth gag.

Everted laryngeal saccules

Everted laryngeal saccules are also excised through an oral approach. Use of a mouth gag and proper patient positioning assists the surgery. Long handled instruments (Allis tissue forceps and Metzenbaum scissors) are usually necessary to properly excise everted laryngeal saccules via the oral approach. Temporary removal of the endotracheal tube or tracheostomy endotracheation greatly improves visibility and surgical efficiency. The everted mucosa is grasped securely with Allis tissue forceps, excised as close to its base as possible using Metzenbaum scissors, and discarded. Any remaining remnants of the saccule are removed in a similar fashion. When employing gentle tissue handling, hemorrhage is usually minimal.

Hypoplastic trachea

There is no clinically tested surgical treatment for hypoplastic trachea. Owners should be notified that respiratory signs will probably persist in those animals with severely hypoplastic trachea, even following successful repair of other disorders. The veterinary clinician should also be prepared to modify endotracheal tube selection in those anesthesia patients with hypoplastic trachea.

Postoperative considerations

Brachycephalic patients require close observation during postanesthetic recovery. Recovery should be as smooth as possible. Preoperative tranquilization (e.g., 0.1 mg/kg acepromazine, IV) may help prolong the recovery process. Smoother, more controlled patient recovery usually results. Endotracheal tube removal should be delayed as long as possible. A temporary tracheostomy may be necessary in selected patients. Water is usually offered a few hours after the patient is awake. Food may not be offered until the following day.

Summary

The anesthetic and surgical management of the brachycephalic dog with upper airway disorder(s) require proper planning and diligence to be successful. Such planning and attentiveness to detail should include complete patient evaluation, proper selection and use of perianesthetic drugs, atraumatic surgery, and close observation during anesthetic recovery.

References

Monnet E. Brachycephalic airway syndrome. In Slatter D (ed) Textbook of Small Animal Surgery, 3rd ed. WB Saunders Co., Philadelphia, 2003, p 808.

Coyne BE, Fingland RB. Hypoplasia of the trachea in dogs: 103 cases (1974-1990). J Am Vet Med Assoc 1992;201: 768.

Hobson HP. Brachycephalic syndrome. Semin Vet Med Surg (Small Anim) 1995;10: 109.

Lorinson D, White RAS. Brachycephalic airway obstruction syndrome: a review of 118 cases. Canine Pract 1997;22: 18.