Adult Chest Surgery

Chapter 50. Tracheobronchial Injuries 

Tracheobronchial injuries are rare but potentially lethal injuries associated with blunt thoracic trauma. The injury is associated with a high-energy impact—typically, a motor vehicle accident or fall. These injuries are often associated with significant thoracic compression injuries, including fractures to the ribs and clavicle, as well as cardiac and pulmonary contusions.

There are several potential mechanisms for tracheobronchial injury. Based on the types of associated injuries, the most likely mechanism is related to shear forces created by rapid deceleration. The highest incidence of airway injury occurs at the sites of mediastinal attachment—within 2.5 cm of the carina. A plausible explanation is that shear develops between restrained and unrestrained airways, leading to disruption of the bronchus. Secondary sites of airway injury include the right middle lobe bronchus and the superior segmental bronchi bilaterally. These airways are relatively long and similarly susceptible to differential deceleration forces. Finally, spiral tears of the right main stem bronchus and bronchus intermedius can occur. These injuries presumably are caused by rotational as well as compressive forces.

DIAGNOSIS

The common presenting signs of blunt tracheobronchial injury include dyspnea, subcutaneous emphysema, and hemoptysis. Also, patients with blunt injury commonly present with sternal tenderness or focal rib pain. Patients presenting with these symptoms, in the context of a high-energy impact, should have a chest CT scan and bronchoscopic examination. Stridor generally is restricted to extrathoracic tracheal injuries, subglottic edema, or bilateral vocal cord dysfunction. These patients typically are intubated soon after the development of stridor.

The radiographic findings may include pneumothorax, pneumomediastinum, and fractures of the bony thorax. The chest CT scan in a patient who has survived a high-energy impact may reveal evidence of a pulmonary contusion and mediastinal hematoma, but free rupture of the airway into the pleural space is rare. In most cases, the soft tissues of the mediastinum and hilum contain the rupture. The airway discontinuity is reflected only by a small amount of extraluminal air and edema. These findings are missed often in a patient with multiple associated injuries.

Because of the difficulty in establishing a radiographic diagnosis of tracheobronchial injury, bronchoscopy is mandatory in any patient who has sustained a high-energy impact injury to the thorax and presents with any sign or symptom of intrathoracic injury. The procedure must be performed by an experienced bronchoscopist. The aspiration of blood and mucus in the proximal airways often complicates the initial trauma bronchoscopy. It is common for the airway injury to be missed at the time of the first bronchoscopy. In addition, airway injuries frequently present as a subtle separation in the airway cartilage that is contained by mediastinal soft tissue. Repeat bronchoscopy is often required to unequivocally establish the diagnosis of airway injury.

INDICATIONS FOR SURGERY

The absolute indication for surgery is the free rupture of a proximal bronchus into the pleural space. In most cases, the patient presents with a pneumothorax. The diagnosis of a proximal airway injury is readily established by the large air leak discovered when the tube thoracostomy is placed within the pleural space. It is common for patients with such an injury to have a pulmonary contusion that results in diminished pulmonary compliance over the ensuing 24–72 hours. Prompt repair has the potential advantage of using single-lung ventilation during the surgery—an option that may not be tolerated hours later. In addition, the repaired airway will allow greater flexibility in mechanical ventilation strategies as the patient recovers from the acute lung injury.

In general, all contained main stem bronchial injuries should be repaired as soon as the patient is hemodynamically stabilized and more life-threatening injuries have been excluded. Injuries to the right main stem bronchus have the potential to rupture into the right pleural space with prolonged or high-pressure ventilation. In contrast, injuries to the left main stem bronchus rarely rupture into the pleural space but are associated with larger gaps in the airway. In both cases, failure to repair the airway can result in functional pneumonectomy secondary to bronchomalacia, stricture, or both. Furthermore, failure to repair the injury promptly can lead to poor airway clearance, chronic infection, and contracted airways, further limiting repair options. Finally, chronic infection can lead to vascular erosion and a fatal bronchovascular fistula.

In patients with severe bilateral pulmonary contusions, hemodynamic and ventilatory instability may preclude any attempt at acute repair of the main stem bronchus. The only therapeutic option in these patients is to optimize ventilatory support and hope for the opportunity of a late repair.

The indication for repair of a middle lobe or superior segmental airway is less an attempt to salvage distal lung tissue than an attempt to prevent secondary complications of stricture and chronic infection. In some patients, the airway separation is minimal, and they can be managed without surgery. In other cases, semielective repair can be performed when the patient is stabilized and pulmonary compliance has improved. Although mechanical stents have been used successfully in this setting, an ongoing concern is the risk of erosion and bronchovascular fistula.

SURGICAL TECHNIQUE

For patients undergoing surgical repair, anesthetic management must avoid further disruption of the airway caused by endotracheal tube misplacement or high airway ventilatory pressures. In the spontaneously ventilating patient, the transition to positive-pressure ventilation may result in sudden rupture and decompression of the airway. Disruption of the airway can lead to massive subcutaneous emphysema, tension pneumothorax, or both. The disrupted bronchial segment must be rapidly and skillfully isolated to maintain adequate lung volumes and gas exchange. In most cases, single-lung ventilation will be required to facilitate repair of the injured airway. Because of the airway injury, bronchial blockers typically are unhelpful, and a double-lumen endotracheal tube is used. The skillful fiberoptic placement of a double-lumen endotracheal tube may be required to avoid aggravation of the airway injury.

Surgical repair of the injury requires a posterolateral thoracotomy to gain adequate control of the hilum and proximal airways. Regardless of the level of the injury, I recommend mobilization of an intercostal muscle pedicle to buttress the repair and minimize the risk of a bronchovascular fistula. The intercostal muscle pedicle is best mobilized at the outset of the procedure.

In most cases, the location of the injury is readily identifiable because of the air dissection and associated soft tissue trauma. Injuries to the right main stem bronchus are readily identifiable in the right hilum. Left main stem bronchial transections, however, can retract several centimeters under the aortic arch—a retraction that can be worsened by rightward displacement of the mediastinum (Fig. 50-1). Despite the problematic appearance of the proximal main stem bronchus, traction sutures can be used to deliver the bronchus into the field and facilitate the repair. On occasion, injuries of the right main stem bronchus may extend into the bronchus intermedius, reflecting a spiral tear. I have managed these injuries successfully by transecting the main stem bronchus separately, repairing the proximal and distal airways, and reconstructing the two repaired airways as a standard end-to-end anastomosis.

Figure 50-1.

 

Left main stem bronchial transections can retract several centimeters under the aortic arch, complicating the repair.

Main stem bronchial anastomoses are relatively easy to repair. The airways do not have the size-mismatch problems commonly associated with transplant anastomoses or sleeve reconstructions. Repair of the disrupted airway typically is achieved with a simple end-to-end anastomosis. Whereas absorbable sutures are used commonly, I prefer monofilament sutures in the context of trauma because of the risk of infection, the frequent need for prolonged ventilatory support, and the unpredictable nutritional status of the patient. In addition, I wrap the repair in an intercostal muscle pedicle to minimize pleural contamination and prevent a bronchovascular fistula.

EDITOR'S COMMENT

On occasion, the patient undergoing repair of a disrupted airway will desaturate with single lung ventilation. I have been able to manage this problem by placing a small catheter through the endotracheal tube and advancing it to the distal lumen of the transected lung, where it is used to deliver oxygen at high flow rates to improve oxygenation.

The intercostal muscle flap should not be used to wrap the repair circumferentially to avoid calcification of the periosteum and late obstruction. I prefer to cover a portion of the repair with the intercostal muscle, and if more is required, to use pericardium or the pericardial fat pad.



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