Anesthetic management of the patient who requires surgical resection of a portion of the large airways continues to challenge the skills of even the most experienced anesthesiologist. The large airways, including the trachea, carina, and major bronchi, can harbor myriad pathologic conditions that necessitate surgical resection and reconstruction.^1–3 The patient presenting for airway surgery is often complex medically. Existing disease states frequently contribute to the development of lesions of the large airways. A specific perioperative plan should be developed in concert with the surgical team, including knowledge of the extent and location of the large airway pathology, as well as the planned surgical approach. The degree of existing airway compromise must be anticipated, as coordination and sharing of the airway occurs throughout airway resection and reanastomosis. Lastly, emergence and extubation needs to be carefully timed. Perioperative care of these patients requires a multidisciplinary team approach and exemplary communication.⁴

The goals of this chapter are to review the etiology of large airway lesions; preoperative evaluation, including pulmonary function testing and radiologic evaluation; and anesthetic management techniques for tracheal resection and reconstruction. Postoperative care of this patient population is outlined.^4–7

Historical Overview

Before 1960, management of patients with tracheal lesions was extremely conservative. Extrathoracic lesions required permanent tracheostomy, while distal lesions were managed by serial palliative dilation or, rarely, limited resection.⁴ Subsequent advances in diagnosis, medical management, anesthetic and surgical techniques, and postoperative intensive care have allowed the successful primary resection and reanastomosis of a wide variety of complex large airway lesions.

Pertinent Anatomy of the Upper Airway and Trachea

The lower airway in adults includes the trachea, bronchi, and bronchi terminating in alveoli.⁸ The trachea is tubular and comprised of 16 to 20 incomplete cartilages anterolaterally and a fibromuscular membrane posteriorly. As observed during bronchoscopy, the posterior fibromuscular wall of the trachea will bulge into the tracheal lumen during expiration and coughing.

The adult trachea measures 10 to 11 cm in length, and 2 cm in external diameter in males and 1.5 cm in females. It extends from the level of the sixth cervical vertebrae, which coincides with the laryngeal inlet, to the fifth thoracic vertebrae, which coincides with the carina. One-third of the length of the trachea is extrathoracic and resides above the level of the sternal notch. Flexion of the neck causes more of the trachea to reside within the mediastinum. Neck extension has the opposite effect and moves the trachea into a more cervical position. This anatomic relationship is crucial in both the surgical exposure and postoperative healing of patients undergoing tracheal resection and reconstruction.⁶

The blood supply of the trachea includes branches from the inferior thyroid, subclavian, innominate, internal thoracic, first intercostal, and bronchial arteries. These branches enter the trachea laterally. Avoiding circumferential dissection of the trachea during airway surgery maintains an adequate blood supply. Despite an extensive vascular supply and ample lymphatic drainage, the tracheal mucosa is pressure sensitive, such as those forces exerted by an endotracheal tube or its inflated cuff. Medical conditions, such as diabetes mellitus or prior radiation, may further compromise tracheal blood supply and jeopardize anastomotic healing.⁶

Lastly, the innervation of the larynx and trachea are vagally mediated via the superior and recurrent laryngeal nerves. The recurrent laryngeal nerve lies within the groove between the trachea and the esophagus. As a result, the recurrent laryngeal nerve can be injured because of tracheal pathology or surgical manipulation.⁶

Etiology of Tracheal Lesions

Tracheal lesions arise from a diverse array of pathologic causes (Box 42.1). Postintubation injuries, trauma, primary and secondary tumors, congenital anomalies, vascular lesions, infectious agents, and certain connective tissue diseases may lead to substantial tracheal pathology. Knowledge of the existing tracheal pathology is essential and invariably dictates the anesthetic regimen, as well as the surgical approach.

Postintubation injury was the leading cause of tracheal stenosis in a large series by Grillo and colleagues in a group of 503 patients. who underwent 521 tracheal resection and reconstructions for postintubation stenosis over a 27-year period.⁹ There were 251 cuff-related lesions, 178 stomal lesions, 38 lesions at two levels. and 36 of undetermined origin. Postintubation tracheal lesions may occur as a result of “traumatic” intubation or secondary to prolonged pressure from an endotracheal tube cuff or tracheostomy.⁹ Postintubation injuries may be apparent throughout the adult trachea, as illustrated in Fig. 42.1.¹ The locations of the postintubation injuries varied as well. Sixty-two patients with significant laryngeal injuries required complete resection of the anterior cricoid cartilage and anastomosis of the trachea to the thyroid cartilage. In 117 patients, the trachea was anastomosed to the cricoid cartilage.⁹

Factors predisposing to significant tracheal mucosal injury and the risk for the development of tracheal stenosis in an intubated patient include: (1) prolonged hypotension, (2) concurrent infection, and (3) persistent elevation of endotracheal tube or tracheostomy cuff pressures.

These factors predispose to tracheal damage by impeding mucosal blood flow, despite the widespread use of high-volume, low-pressure endotracheal tube cuffs.⁷ Posterior glottic stenosis and circumferential subglottic stenosis result from direct trauma from the endotracheal tube and cuff.⁷ High cuff pressures are entirely avoidable by the judicious use of the appropriate size of endotracheal or tracheostomy tube, as well as frequent monitoring of cuff pressures in all intubated patients. Cuff pressures should be maintained below 25 mm Hg whenever possible.⁴ The risk of tracheal injury increases with the length of time the patient remains intubated. However, mucosal injury leading to tracheal ulceration has been noted after 2 to 3 hours in certain patients.¹⁰

Neoplasms are the second major indication for primary tracheal resection and reconstruction.

Over a 26-year period, 198 patients with primary tracheal tumors were evaluated. Some 147 tumors were excised (74%); 70 patients had squamous cell carcinoma (36%), 80 had adenoid cystic carcinoma (40%), and the remaining 48 (24%) had a variety of lesions.¹¹

Secondary tumors of the trachea are also seen.¹² Metastatic cancers of the mediastinum comprise this group. Thyroid, esophageal, bronchogenic, and breast cancers can invade the trachea; thymomas, lymphomas, and carcinomas of the head and neck may be secondary tracheal neoplasms. Thyroid tumors occurred most frequently in this group. Such tumors cause extrinsic compression of the trachea or symptoms of upper airway obstruction by direct invasion of the trachea. Thyroid carcinomas are the most amenable to palliation and cure.

Trauma to the tracheobronchial tree may result from blunt or penetrating injuries. Failure to recognize acute airway injuries and provide an adequate airway may result in death or eventual laryngotracheal stenosis.¹³ Mathisen and Grillo reported a series of 10 patients with acute laryngotracheal injuries.¹³ Blunt trauma to the trachea and larynx occurred in 50% of patients with acute laryngotracheal injuries. Penetrating injuries, such as gunshot or stab wounds, affected 40% of these patients. Traumatic attempts at intubation composed the remaining 10% of acute laryngotracheal injuries. Blunt trauma to the head, neck, and chest were the most common associated injuries in patients with laryngotracheal injury. The laryngotracheal junction, the most frequent site of injury, occurred in six patients. Sudden deceleration injuries resulted in injury to the posterior membranous wall of the trachea involving the carina in two patients. All patients in this series underwent successful definitive primary repair of their airway injuries and maintained an excellent airway postoperatively. It is critical to remember that failure to identify acute laryngotracheal injury can result in progressive airway obstruction, as scarring occurs and stenosis develops.¹³

Cicala and colleagues reviewed the initial evaluation and management of upper airway injuries in a trauma population.¹⁴ Some 46 cases of upper airway injury admitted to a large, metropolitan, university-affiliated trauma center were reviewed retrospectively over a 4-year period. A total of 26 cases of upper airway injury were the result of penetrating trauma; 17 injuries were caused by gunshot wounds and nine were resulting from knife wounds. The remaining 20 patients sustained blunt trauma to their upper airway. Motor vehicle accidents, the leading cause of this trauma, occurred in 13 patients. Diagnostic findings were varied, as illustrated in Table 42.1. The location of the injury was the larynx in 13 cases, the trachea in 24 cases, the cricoid cartilage in five cases, and multiple sites in four cases. The overall mortality rate in this series was 24%, and this rate did not vary according to patient age or mechanism of injury. Appropriate initial airway management depends on the rapid accurate diagnosis of the extent and location of the upper airway injury.¹⁴

Thorough preoperative diagnostic evaluation of patients with obstructive lesions of the airway is mandatory. Chapter 8 describes preoperative evaluation of the thoracic surgical patient in detail. Diagnostic evaluation entails a detailed history and physical examination, pulmonary function studies, imaging studies, and bronchoscopy. The diagnostic regimen is often dictated by the severity and urgency of airway compromise. For example, in life-threatening situations in which there is a high index of suspicion as to the nature of the tracheal pathology, bronchoscopy may be the primary method of diagnosis, in addition to the detailed history and physical examination. On the contrary, the patient presenting for elective repair warrants a detailed evaluation.⁷

History and Physical Examination

A detailed history can be revealing in several areas. The physician should seek etiologies likely to produce airway compromise, such as an antecedent history of endotracheal intubation or tracheostomy. Such patients should be considered to have an organic lesion until proven otherwise.^4,6,7

The signs and symptoms of large airway obstruction are affected by several factors. The anatomic location of the lesion, the severity of airway obstruction, and the presence of preexisting cardiopulmonary disease are important variables to consider. Clinical symptoms of airway obstruction include dyspnea, especially with effort, and wheezing, which may present as frank stridor. Persistent cough, hoarseness, and difficulty in clearing secretions are other common symptoms. Complete airway obstruction may occur from inability to clear secretions because of an underlying organic lesion. Adult patients become symptomatic when the cross-sectional diameter of the airway is reduced to approximately 8 mm or roughly 50% of normal.¹⁵ Extremely active adults may have symptoms with a milder degree of airway obstruction. Stridor at rest is indicative of severe airway narrowing (5–6 mm).^16,17 Patients with stridor have extremely tenuous airways. Such patients deserve close monitoring, which may warrant preoperative admission to an intensive care unit. Vocal cord or recurrent laryngeal nerve pathology is indicated by hoarseness. Direct or indirect laryngeal examination is necessary.

The symptoms described earlier are frequently misdiagnosed. Several patients, especially those with tracheal tumors, have been diagnosed as having “asthma.” An alternative diagnosis is entertained only when “asthma” is unresponsive to conventional medical therapy, which often includes the use of corticosteroids.^18,19 The severity of the tracheal stenosis, graded from I to IV, is depicted in Fig. 42.2.

To review, a detailed history is essential in the patient with a known or suspected tracheal pathology. Salient points include a history of smoking, prior intubation, or tracheostomy. A precise evaluation of the patient’s exercise tolerance is warranted, including any recent onset of hoarseness or stridor, inability to tolerate the supine position, persistent cough, or inability to clear secretions. The severity of preexisting cardiopulmonary disease may limit the patient’s exercise tolerance. Tracheal lesions may present at an advanced stage when this occurs.

A careful physical examination entails a detailed examination of the airway. The trachea should be palpated for extrathoracic compression or deviation. Audible stridor, either at rest or with a maximal expiratory effort with an open mouth, is often elicited. Auscultation of the chest may reveal diffuse inspiratory and expiratory wheezing, which is difficult to differentiate from bronchospasm. Auscultation of the upper cervical airway may reveal high pitched inspiratory and expiratory sounds characteristic of air flow obstruction. The anesthesiologist’s preoperative evaluation should include assessment for anticipated difficulty with mask ventilation, intubation, or both; the degree of airway limitation because of tracheal pathology; and any anticipated perioperative issues.^6,20

The range of motion of the neck is an essential component of the physical examination. The patient should be able to tolerate both hyperextension and hyperflexion comfortably. Several disease states are associated with instability of the cervical spine (Box 42.2).^21,22 If the cervical spine motion limitation is in question, it should be evaluated radiographically before surgery in nonurgent cases. The type and function of the in situ tracheal appliance is important to ascertain preoperatively.²³ The patient may have a cuffed or cuffless tracheostomy tube in situ. The location of the tracheal appliance in relationship to the lesion is also important. The patient’s tolerance of decannulation should be determined. The stoma should be patent and stable, and the patient should give a history of relatively stable airway if decannulated. The existing tracheal appliance may then be removed and replaced with a cuffed tube before the induction of general anesthesia. A recent tracheostomy of less than 2 weeks should only be managed by qualified team.