Subglottic Stenosis

Introduction

Subglottic stenosis (SGS) used to be primarily congenital in etiology, and managed conservatively with a tracheostomy tube. Long-term intubation, especially in premature infants, was introduced in the latter part of the 20th century and resulted in increasing rates of acquired SGS, which was associated with worse outcomes as compared with congenital SGS. Laryngotracheal reconstruction (LTR) was introduced in the 1970s, and has expanded to include various open and endoscopic techniques.

The larynx provides several functions, including air transport, phonation, and airway protection during deglutition. As in all surgical intervention, the sequelae of surgery must be weighed carefully, and patient selection is paramount. It is critical to ensure a safe and secure airway. Expansion of a stenotic airway should not come at the cost of dysphonia or dysphagia.

A diagnostic airway endoscopy is required in the evaluation of SGS to assess the location and severity of stenosis, as well as to identify synchronous lesions. Potential causes of airway obstruction must be evaluated, including choanal atresia, piriform aperture stenosis, adenotonsillar hypertrophy, microretrognathia, macroglossia, lingual tonsillar hypertrophy, hypotonia, laryngomalacia, vocal cord paralysis, vascular ring, or tracheobronchomalacia. The Myer-Cotton grading scale is used to describe the severity of SGS ( Table 194.1 ). During endoscopy, a nasopharyngeal and/or tracheal culture can be obtained to test for methicillin-resistant Staphylococcus aureus (MRSA). It is important to ensure adequate pulmonary function. An evaluation of swallow function is also recommended with a functional endoscopic evaluation of swallow (FEES) or modified barium swallow (MBS). Esophagoscopy with biopsy may also be considered to be sure that reflux esophagitis or eosinophilic esophagitis (EE) are not present prior to reconstruction, as they are associated with granulation, restenosis, or failed decannulation.

To ensure a safe airway, prerequisite skills include basic endoscopic airway techniques including suspension laryngoscopy, management of airway foreign bodies, cricothyroidotomy, and tracheotomy. Direct laryngoscopy with microscopic or endoscopic assistance improves visualization and enables photographic documentation. Bronchoscopy can be performed with either a telescope alone or a rigid bronchoscope. The diameter of the telescope alone is smaller than the bronchoscope, limiting tissue trauma. However, the rigid bronchoscope allows for passive oxygen insufflation, suctioning, or other endotracheal manipulations. Close communication with the anesthesiology team is required to ensure safety, since throughout the various portions of the procedures, it may be required to occlude the airway or tolerate intermittent apnea.

Endoscopic approaches to SGS are most appropriate for low-grade stenosis, and for immature stenosis. Continuous radial expansion (CRE) balloons have replaced traditional rigid laryngeal dilators secondary to decreased shearing trauma. Radial incisions (laser or cold knife) of the stenosis can be considered prior to dilation. Preservation of healthy mucosa between incisions aids in preventing cicatricial scarring. When serial dilations fail in an infant with SGS after prolonged intubation, an anterior cricoid split may be an option to expand the airway enough to allow for extubation and to avoid tracheostomy tube placement. This can be done endoscopically if exposure is adequate, or transcervically, as originally described. However, in higher grade or mature stenosis, LTR or cricotracheal resection (CTR) should be considered.

LTR creates vertical incisions of the anterior and/or posterior cricoid cartilage ring, and augments the diameter of the airway with cartilage grafts. This can be done as a single or multistaged procedure. Single-stage LTR (SS-LTR) requires prolonged sedation and hospitalization, whereas double-stage LTR (DS-LTR) maintains a tracheostomy tube after the first procedure, and places a trans-laryngeal stent that requires subsequent procedures for stent removal and eventual decannulation. DS-LTR is considered for patients with multilevel stenosis, high-grade stenosis, difficult oral intubation due to craniofacial anomalies or cervical spinal disorders, or patients with significant pulmonary disease.

Various cartilage donor sites have been described, but the most common are the thyroid ala or costal cartilage. The thyroid ala is accessible within the surgical site, but is best suited for patients age 2 or younger because of the limited size. When a larger graft, or both anterior and posterior grafts are required, costal cartilage is ideal. Often a single rib is adequate; a second rib is more likely to be required in patients less than 1-year-old due to size.

Restenosis is a risk, and more likely with higher Myer-Cotton grades. An alternative to LTR is partial CTR, in which the anterior cricoid and stenotic laryngotracheal segment is excised, resulting in thyrotracheal end-to-end anastomosis. This is more effective in high grade stenosis, but introduces the risk of dehiscence and increased risk of injury to the recurrent laryngeal nerve (RLN). CTR has been found to be more effective for Myer-Cotton grade 3 or 4, but may not be suitable in a high level or long-segment stenosis. A minimum distance between the stenotic segment and the true vocal folds of 3 mm, and resection length no greater than 30% of the trachea, has been recommended. Tension-free anastomosis is paramount for success.

Operative risks are numerous and include scarring, infection, dehiscence of the anastomosis, recurrent stenosis including posterior glottic stenosis, inability to extubate or decannulate, airway obstruction, pneumonia, pneumomediastinum, hypoxia, and cardiorespiratory arrest. Airway obstruction can occur due to occlusion or aspiration, edema, granulation tissue, or graft dislodgment. The RLN can be injured during dissection or retraction. Dysphonia and dysphagia may occur. Risks of costal cartilage harvest include scarring, infection, and pneumothorax. Postoperative myopathy and opioid withdrawal is common after prolonged sedation.

Proper postoperative management is critical. Patients who have had minor endoscopic procedures such as dilation may be observed overnight. Procedures that incise the airway and expose cartilage often require prolonged sedation to promote graft healing. Single-stage procedures require intubation for 7 to 10 days, which allows for stenting while securing the airway. During this time, daily sedation holidays with lifting of neuromuscular blockade limits muscle atrophy and atelectasis. Multistaged procedures create immature tracheostoma, with tube change planned on postoperative day 5. Antibiotic prophylaxis and proton-pump inhibitor treatment is recommended during the period of sedation/intubation or until graft mucosalization. Repeat endoscopy is recommended 2 weeks after extubation for single-stage procedures, and 4 weeks after multistaged procedures for removal of the stent.

Several alternative or adjuvant treatments are available. Topical Mitomycin C is an antineoplastic agent that prevents fibroblast proliferation, and has been used in the prevention of granulation and scarring. Several small studies have suggested improved healing, but a randomized control trial failed to demonstrate a discernible benefit. In addition, risks include myelosuppression, pulmonary toxicity, and possible carcinogenicity. Systemic or topical corticosteroids may improve inflammatory stenosis. Perioperative administration of Decadron is helpful as an adjuvant to airway procedures, and can facilitate extubation. Injection of corticosteroids into SGS is also a common adjuvant treatment. Finally, a tracheostomy may be required if the patient is not a candidate or fails reconstruction, or if the patient is unable to be decannulated.

Key Operative Learning Points

• Important goals are to create a safe airway, alleviate airway obstruction, and eliminate tracheostomy tube dependence, while preserving swallowing and phonation.

• Appropriate patient selection, preoperative evaluation, and surgical planning are critical.

• Daily sedation and paralytic holidays after reconstruction are important to limit muscular atrophy and atelectasis in the perioperative period.

Preoperative Period