Tracheal Trauma

Introduction

In dogs and cats, trauma to the trachea can occur due to an internal injury or due to external trauma.

Internal injury due to intubation

Prolonged use of high-pressure, low-volume cuffed endotracheal or tracheostomy tubes can exert pressure on the tracheal wall and lead to ischemic necrosis of the mucosa or even the entire thickness of the wall.

Events that can lead to tears and injuries include: overinflation of the cuff, traumatic intubation, turning of the patient during anaesthesia without disconnecting the endotracheal tube, and removal of the tube without deflating the cuff.

This is most common in cats, and tears of the dorsal membrane are most widely seen.

If the defect is not full-thickness, the granulation tissue that forms may encroach on the lumen and result in stenosis by proliferation and contraction.

Management

If mucosal loss is observed at extubation, mitomycin C should be applied topically for 5 minutes, and antibiotics should be given to prevent deep infection.

See below for the treatment of tracheal rupture.

External injury

This can be caused by blunt or penetrating trauma to the cervical or thoracic regions.

This may result in a tracheal tear, or if it is complete, tracheal avulsion/rupture/transection.

The number of blunt trauma cases resulting in tracheal injury is small in dogs and cats. Because most blunt trauma is inflicted laterally on animals, the trachea is not crushed against the spine and can move with the impact.

Tracheal avulsion secondary to trauma often occurs just cranial to the carina, and an airway is still maintained with a pseudotrachea formed from adventitial tissue surrounding the trachea or from the mediastinum. There will be inflammation and narrowing over time, but clinical signs may not occur until 5-14 days after the initial trauma.

Clinical Signs

Dyspnoea is the major presenting sign of tracheal trauma.

If penetrating trauma is the cause of injury, there will be extensive tissue damage in the cervical or thoracic areas.

Cervical tracheal trauma may result in subcutaneous emphysema.

Intrathoracic tracheal trauma results in a primarily expiratory dyspnoea as the trachea is collapsed by the intrathoracic pressure.

There may be pneumomediastinum and pneumothorax, which may lead to cyanosis.

Signs of shock may also be present.

Diagnosis

Radiographs are essential in the diagnosis, but should only be performed if the patient is stable enough.

Loss of continuity of the trachea is commonly observed, and there may be a gas-filled diverticulum. Narrowing of the trachea may also be observed.

There may be signs of pneumomediastium or pneumothorax.

Bronchoscopy would enable to visualise the defect, but is usually not indicated due to the risk of the procedure.

Treatment

Cervical trachea: damage to a segment involving 35% of the trachea in adults can be resected and the ends of the trachea anastomosed. There is usually trauma and tissue loss, and drainage of the peritracheal area is required until the infection is controlled.

Intrathoracic trachea: a right 4th intercostal thoracotomy is made and the defect is visualised. The endotracheal tube should ideally be placed so that is goes into the segment aborad to the rupture. Maintaining an adequate airway is very important and may require specialist equipment such as sterile breathing circuits. Excision of the damaged rings and anastomosis of the two segments should then be completed. A mediastinal patch can be used to provide a seal for the anastomosis.

Post-operatively, to prevent tension of the trachea, tape can be sutured between the mandible and the manubrium for 1-2 weeks to prevent overextension of the neck to decrease the risk of dehiscence.

Prognosis

The prognosis for tracheal rupture cases is excellent when diagnosed and treated appropriately.

Concurrent injuries and penetrating trauma may hold a poorer prognosis.

Tracheal Trauma Learning Resources
Flashcards Test your knowledge using flashcard type questions	Small Animal Soft Tissue Surgery Q&A 04

References

Slatter, D. (2002) Textbook of small animal surgery Elsevier Health Sciences

King, L. (2004) Textbook of respiratory disease in dogs and cats Elsevier Health Sciences

Norsworthy, G. (2010) The Feline Patient John Wiley and Sons

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