TP3.2 - Blunt Aortic Injury

Question 1

Mechanisms of Injury?

Answer 1

❖ Blunt aortic injury most often occurs after sudden deceleration, usually in automobile crashes
❖ Other causes include crashes of motorcycles and aircraft, auto pedestrian collisions falls, and crush injury
❖ The descending aorta is fixed to the chest wall, whereas the heart and great vessels are relatively mobile
❖ Traditional views have held that sudden deceleration causes a tear at the junction between the fixed and mobile portions of the aorta, usually near the isthmus

Question 2

Pathophysiological Features?

Answer 2

❖ Stretching effect from sudden deceleration
❖ Aortic rupture during a sudden increase in intra-abdominal pressure
❖ A “water-hammer”effect, which involves simultaneous occlusion of the aorta and a sudden elevation in blood pressure
❖ A “osseous pinch” effect from entrapment of the aorta between the anterior chest wall and the vertebral column have also been theorized
❖ Most injuries probably involve a combination of forces

Question 3

Theoretical sequence of injury?

Answer 3

❖ Rupture of the intimal and medial layers
❖ After a period of unpredictable duration, rupture of the external, adventitial aortic wall occurs
❖ These findings suggest that sufficient residual strength exists after an intima-media injury before complete rupture to allow timely diagnosis and treatment

Question 4

Diagnosis?

Answer 4

❖ Computed tomography is now the diagnostic test of choice
❖ Other options for the diagnosis of blunt aortic injury include:
- Transesophageal echocardiography
- Intravascular ultrasonography
- Magnetic resonance imaging

Question 5

Perioperative Decision Making?

Answer 5

❖ Once the diagnosis is made, treatment must be properly timed
❖ Immediate operative repair used to be the rule
❖ However, patients often have multisystem injuries that complicate aortic repair
❖ Several studies have demonstrated the relative safety of a delayed approach, particularly if there are substantial co-injuries, using a regimen of beta-blockers and antihypertensive agents to decrease the shear force on the aortic wall

Question 6

Surgical Repair?

Answer 6

❖ Surgical repair requires intubation with a double lumen endotracheal tube and exposure of the injury through an incision in the left fourth intercostal space with unilateral ventilation of the right lung to improve access to the injury

Question 7

Clamp-and-sew technique?

Answer 7

❖ Included an interposition graft of woven or knitted Dacron to bridge the defect
❖ Associated mortality of 16% and a striking 19% incidence of paraplegia
❖ Various methods of distal aortic perfusion have evolved for use during the period of aortic clamping in order to protect the spinal cord

Question 8

Complications of Surgical Repair?

Answer 8

❖ Overall rate of death of 31% and rate of paraplegia of 8.7%
❖ The rate of death in patients who did not undergo surgery was 55%

Question 9

Limitations of Surgical Repair?

Answer 9

❖ Patients with severe brain injury require continuous monitoring of measures such as intracranial pressure
❖ Significant lung injury may also preclude early repair of blunt aortic injury; hypoxemia commonly occurs with single-lung ventilation
❖ Patients may have other competing priorities, such as the need for laparotomy to control intra-abdominal injury
❖ Patients with pelvic fractures may require angiographic embolization and can re-bleed when positioned for a thoracotomy

Question 10

Endovascular Repair?

Answer 10

❖ A guide wire is advanced under fluoroscopic guidance to the site of injury; the position is identified on angiography and the stent graft deployed across the injured aorta, excluding it from the circulation
❖ In these studies, there was a reduction in morbidity and mortality and no cases of paraplegia in the endograft groups