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Tracheal resection

Peter Goldstraw

HISTORY

Early attempts at tracheal resection were timid, limited to 2 cm or less of the trachea and frequently less than circumferential. More extensive resections were attempted, exploring the use of various prostheses and homograft techniques. The results with such techniques were poor, adversely affected by failure of healing and granulation tissue ingrowth. The modern era of tracheal surgery began when Hermes. C. Grillo and colleagues undertook a series of cadaveric studies to establish the length of trachea that could be safely resected with end-to-end anastomosis. These studies were confirmed by a surgical series in which he and F. Griffith Pearson developed and expanded surgical techniques. These pioneers established the general principles of this surgery; the length of trachea that could be safely resected; and the ancillary measures required, allowing tension-free anastomosis. Although some have tried to extend these limits by developing newer prosthetic materials, these have not proven to be safe.

PRINCIPLES

Segmental resection of the trachea is appropriate for benign or malignant conditions affecting the trachea from the cricoid cartilage to the carina. Below this level, carinal resection and reconstruction is possible. Such conditions include fibrous stricture following intubation or tracheostomy; benign tumors of the airways such as carcinoid tumors; and malignant tumors, chiefly squamous carcinoma and adenoid cystic carcinoma. To be suitable for resection, the disease process has to be limited to a length of trachea that can be safely resected, and the patient must be sufficiently fit to tolerate such surgery safely. As a general rule, 50% of the trachea can be resected and repaired by end-to-end anastomosis. This length may be slightly greater in a young child and slightly less in an older person. As one approaches these limits, various release procedures are helpful to enable endto-end anastomosis without undue tension.

A cervical approach allows resection of airway pathology affecting the distal larynx, the cervical trachea, and all but the distal 2-3 cm of the intrathoracic trachea. If this segment is involved, a thoracic approach is to be preferred, allowing carinal reconstruction, if necessary. The approach used will be influenced somewhat by the pathology. The length of airway to be resected can be more reliably determined for benign pathology. The margins of resection for malignant disease are less predictable and the surgeon will have to plan to allow for wider resection if necessary.

The choice of relieving procedure will, to some extent, also be influenced by the incision used.

In planning the surgical approach, consideration must be given to the alternatives available to allow continued ventilation during resection and reconstruction. The use of cardiopulmonary bypass has been tried in the past but has been rendered obsolete by alternatives that do not require heparinization.

Prophylactic antibiotics should be given for any operation on the airway, and anaerobic cover be added if there is severe obstruction or necrotic tumor.

As the surgeon will understandably restrict the length of resection to the minimum, the use of frozen section examination is recommended when undertaking airway resection for tumors, especially adenoid cystic carcinoma with its propensity for microscopic intramural extension.

For patients who are unfit for surgery, or whose disease is too extensive to permit resection, there are many alternative techniques. The appropriate technique will vary depending on the site, length, and pathology of the stricture, and include radiotherapy and a wide range of surgical procedures that achieve disobliteration and the maintenance of a safe airway by the use of temporary and permanent stents. These techniques are beyond the scope of this chapter. The longterm results of such therapy are less satisfactory than those achieved by an operation and the opinion of an appropriate surgical specialist should be sought before denying the patient an operation.

PREOPERATIVE ASSESSMENT

The severity of airway narrowing can be assessed clinically, by spirometry and lung function testing and by radiology. The extent of disease, particularly its intramural and extramural components, is aided by computed tomography. However, bronchoscopy remains the most critical evaluation, and the use of the rigid bronchoscope under general anesthesia has the advantages of a wide field of view, temporary breath holding, and the ability to take multiple large biopsies. In the emergency situation, its use can prove lifesaving, allowing measures to achieve rapid relief of critical stenosis. Using the rigid bronchoscope, the surgeon can accurately measure the length of the trachea; the extent of the segment that would require resection; and the relationship of its proximal and distal margins from such key landmarks as the carina, larynx, and any tracheostome. This is best done by marking the bronchoscope with thin strips of adhesive applied at the level of the upper incisors. The assessment of any dynamic, malacic component is aided by examining the airway with the patient coughing at the end of the evaluation.

Basic oncological principles apply when evaluating the feasibility of airway reconstruction for malignant disease. Distant metastases and extensive nodal disease should be excluded. Mediastinoscopy may be of value but local, mediastinal extension does not carry the same import as when evaluating lung cancer, as long as resection is deemed feasible.

Patient fitness must be assessed carefully. A greater level of fitness is necessary if a thoracic approach is needed, especially if concurrent pulmonary resection is contemplated. It is less of an issue if a cervical approach is judged suitable. Lung function testing is not representative of the patient’s fitness in the presence of severe airway obstruction! Psychological and cerebral status may affect the patient’s ability to cooperate with the physiotherapist in the postoperative period, and to tolerate the neck flexion necessary to safeguard the anastomosis.

Tracheal resection should not be undertaken as an emergency procedure. Surgical disobliteration will allow measured evaluation, accurate staging of malignant disease, discontinuation of steroid medication, and clearance of distal infection. The patient can then be brought to elective surgery fully appraised of the risks and benefits of surgery, and in the best physical and psychological state. The surgeon can plan the surgery carefully and ensure expert anesthetic support and the availability of frozen section pathology services.

OPERATIONS

Segmental resection of the trachea by a cervical approach

1. Following induction of anesthesia, it is helpful to repeat the bronchoscopic assessment using a rigid bronchoscope. This will allow the anesthetist to assess the size of endotracheal tube that can be negotiated through the strictured area. The surgeon can assess the location of the stricture relative to the skin incision by inserting a narrow-bore needle percutaneously into the lumen and viewing its relationship to the stricture through the bronchoscope. Ventilation during tracheal mobilization is safer if an endotracheal tube can be placed across the stricture. If this is not possible, the airway is precarious and intermittent obstruction may be encountered. A size 5.5 or 6.0 Fr armored endotracheal tube can usually be negotiated through the stricture into the distal, normal trachea. The patient is positioned supine, with the neck extended by a sandbag under the shoulders and the head secured in a ring. (See Figure 7.1 .)
   
2. A curved, collar incision is made, centered on the tracheostomy scar, or midway between the thyroid cartilage and the suprasternal notch, extending between the lateral borders of the sternomastoid muscle on each side. The incision is deepened through platysma muscle using the diathermy, dividing superficial veins. The sternomastoid muscles are mobilized laterally from the suprasternal notch to the level of the thyroid cartilage. The trachea is identified in the midline and mobilized along its anterior aspect for the full length of the incision. The strap muscles may be divided but are usually reflected laterally. If necessary, the isthmus of the thyroid gland is divided between transfixion sutures. (See Figure 7.2 .)
   
3. One must now decide where to make the initial incision into the trachea. It is usually preferable to make the distal transection first, as this allows one to speedily transfer ventilation to an endotracheal tube inserted into the distal trachea, if this is thought to be necessary. However, if the proximal margin of resection is easier to define, one can easily start at this point. The limits of the stricture may be apparent from external examination of the trachea, but if this proves difficult, identification of this important point is aided by temporarily withdrawing the endotracheal tube over a flexible bronchoscope. The light is visible through the tracheal wall, and the precise point at which to make the first incision can be identified by passing a fine-gauge needle into the lumen under endoscopic control. The trachea is mobilized circumferentially at this level. Care must be taken to avoid the recurrent laryngeal nerves. Some experts would favor dissection to identify these nerves.

However, the surrounding inflammatory response can make this difficult and it is usually preferable to avoid damage to the nerves by keeping the dissection close to the diseased tracheal wall. The contralateral nerve is at greater risk and extreme care is needed when dissecting between the trachea and the esophagus around the far side of the trachea.

The anterior wall of the trachea is incised with a pointed blade and circumferential division undertaken using scissors. Stay sutures of 2-02 monofilament are inserted into the anterior wall of the distal trachea to prevent retraction of the distal lumen. Ventilation is not interrupted, as the cuff of the tube should lie distal to this level. A longitudinal incision is then made along the anterior wall of the trachea, until the normal lumen is identified at the other limit of resection. (See Figure 7.3 .)

• The endotracheal tube can be retracted anteriorly while the whole circumference of the diseased segment is mobilized. If this step is difficult or prolonged, the endotracheal tube should be withdrawn into the larynx. A suture into its tip facilitates retrieval into the trachea. Ventilation is then transferred to an endotracheal tube inserted into the distal lumen across the operating field. A Bain’s circuit is less intrusive for connecting this tube to the ventilator. This distal endotracheal tube is often in an unstable position and it is as well to delegate an assistant to focus entirely on maintaining satisfactory ventilation. Liaison with the anesthetist is essential during this type of ventilation. Care is necessary to keep close to the tracheal wall while undertaking this circumferential mobilization, avoiding damage to the esophagus and the recurrent nerves. Once the length of the tracheal defect is known, the surgeon should assess if further mobilization or release procedures are necessary to allow apposition of the tracheal ends without tension (see later). Mobilization of the distal airway should be limited to the anterior and posterior aspects of the trachea, preserving the lateral, vascular tissues. (See Figure 7.4a and b.)
  
• An end-to-end anastomosis is performed using continuous monofilament material, such as 3-0 Prolene on a 17 mm needle. The anastomosis is reinforced at each quadrant with interrupted sutures of 2-0 Prolene, which, ideally, should pass through the cartilages of the trachea and not penetrate the lumen of the trachea. The first interrupted suture is placed at the near posterior cornu of the tracheal cartilage. The continuous suture runs, over and over, through the full thickness of the posterior tracheal wall to the opposite cornu, where the second stay suture is inserted. Each of the stay sutures should be inserted just ahead of the running suture to avoid damage to the continuous suture. Once the posterior wall of the anastomosis has been completed, the sandbag beneath the shoulders is removed. Traction of the two stay sutures approximates the ends of the trachea and the continuous suture is drawn tight. The continuous suture continues around the far wall of the trachea to the anterior aspect of the anastomosis. A further stay suture is inserted at this point. The standing suture at the near side of the posterior wall is then used to run in an over-and-over full thickness fashion around the nearside of the trachea to the anterior wall. The fourth stay suture is inserted at the anterior quadrant, ahead of the continuous suture. The continuous suture is tied, and the four stay sutures are tied to complete the anastomosis. If an endotracheal tube has been inserted into the distal lumen, at some point during the anastomosis, it will become intrusive. The translaryngeal tube is retrieved into the trachea to continue ventilation, and the distal tube is removed. (See Figure 7.5 .)
  
• Postoperative problems with sputum clearance are uncommon, but if this occurs, there can be great difficulty inserting a minitracheostomy tube. It is best to insert such a tube, above or below the anastomosis, as a routine. (See Figure 7.6 .)

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