Thoracic Vascular Injury

Matthew J. Wall Jr.

Tammy Zapalac

Bradford G. Scott

PATHOPHYSIOLOGY

More than 90% of thoracic great-vessel injuries are caused by penetrating external or iatrogenic trauma.¹ Aortic injuries have caused or contributed to 15% of deaths following motor vehicle accidents (MVAs).²,³,⁴ Blunt injuries to the innominate artery are actually aortic arch injuries. At the aortic plate, the innominate artery may be “pinched” between the sternum and the vertebral column during anterior sternal impact.

Owing to the high density of vascular structures in the upper midline mediastinum, a common presentation for brachiocephalic vessel injuries is either a stab wound or gunshot wound to the suprasternal notch traversing the upper mediastinum. As expected, stab wounds most commonly injure the ascending aorta, whereas gunshot wounds injure the descending thoracic aorta. Lacerations of the thoracic great vessels, including the arch of the aorta, are reported complications of percutaneous central venous catheter placement.⁵,⁶

INITIAL EVALUATION AND MANAGEMENT

The patient with penetrating thoracic vascular trauma is often hemodynamically unstable, with hemorrhage into either pleural cavities or the mediastinum. These patients are rapidly taken for an urgent thoracotomy and the diagnosis of a vascular injury is made intraoperatively. Fortunately, in many patients with either penetrating or blunt trauma, a contained hematoma of the mediastinum develops. This permits the evaluation and planning of the operative approach.

For patients with penetrating thoracic trauma, information regarding the length of the knife, the firearm type and number of rounds fired, the patient’s distance from the firearm, and a history of previous gunshot wounds, although not always reliable, may be helpful if obtained from the patient or accompanying persons.

Historical information relating to potential blunt injury to the innominate artery/transverse arch include deceleration injury, fall from a significant height, the magnitude of energy transfer, vehicle crash dynamics, cockpit intrusion, and the amount of vehicle deformity. Emergency medical personnel can also provide medical information that is important in evaluating the potential for a thoracic great-vessel injury, such as the amount of hemorrhage at the scene, any history of neurologic deterioration following the accident, and hemodynamic instability during transport.

Physical Examination

The patient is evaluated using the standard Advanced Trauma Life Support approach. Specific findings such as hypotension; decreased, absent, or unequal peripheral pulses; unequal blood pressures in the extremities; expanding hematoma of the thoracic outlet or base of the neck; palpable fracture of the sternum; or proximity of missile or knife path to the brachiocephalic vessels. External signs of major chest trauma may increase suspicion for brachiocephalic vessel injury.

Chest Roentgenograms

In many cases of brachiocephalic injury, the radiologic findings on a supine film may be sufficient to warrant immediate arteriography. For penetrating injuries, it may be helpful to reconstruct trajectory by placing radiopaque markers to identify the entrance and exit sites. Radiographic findings that suggest penetrating thoracic great-vessel injury are noted in Table 1.

Fluid Resuscitation

The treatment of significant shock may include blood transfusion. However, rapid infusion of significant volumes of either blood or crystalloid before surgery may elevate the blood pressure. This may dislodge a protective clot and cause further exsanguination resulting in a cyclic hyper-resuscitation.⁷ The principles of permitting moderate hypotension (systolic blood pressure of 70 to 90 mm Hg) and limiting fluid administration until operative control of bleeding are principles established for ruptured abdominal aortic aneurysms, which may equally apply to acute thoracic vascular injury because the pathophysiology is remarkably similar.⁸,⁹ With both penetrating and blunt chest trauma, associated pulmonary contusion occur and provide additional rationale for limiting perioperative fluid administration.

Emergency Department Thoracotomy

Emergency department thoracotomy in patients presenting with signs of life and hemodynamic collapse may reveal injuries to major thoracic vessels. These injuries require rapid control of bleeding, allowing transfer to the operating room for definitive repair. For example, subclavian vessel injuries can be controlled by packing the apex of the chest or inserting a large balloon catheter. Major hemorrhage from the pulmonary hilum can be managed temporarily by clamping the entire hilum or twisting the lung 180 degrees after releasing the inferior pulmonary ligament.¹⁰ Fortunately, the brachiocephalic vessels are relatively anterior and accessible by extending the left thoracotomy into a clamshell incision. The goal is rapid vascular control so the patient can be moved to the operating room. Emergency center thoracotomies for brachiocephalic vessel injures are daunting procedures with a high mortality.

TABLE 1 X-RAY FINDINGS THAT SUGGEST PENETRATING BRACHIOCEPHALIC VESSEL INJURIES

Widened upper mediastinum

Large hemothorax

A trajectory with proximity to the thoracic outlet

Foreign bodies (bullets or shrapnel) in proximity to the great vessels

“Missing” missile in a patient with a gunshot wound to the chest, suggesting distal embolization

ADVANCED DIAGNOSTIC STUDIES

Computed Tomography/Transesophageal Echocardiography/Magnetic Resonance Imaging

Conventional computed tomography (CT) may demonstrate hemomediastinum but has not demonstrated the diagnostic capability of aortography. Therefore, we have reserved CT for patients who have a “normal”-appearing mediastinum on chest x-ray, a suggestive mechanism, and require a CT for other reasons such as a concomitant head injury. If a mediastinal hematoma is visualized on CT, formal aortography is still obtained to determine the site(s) of injury and to identify any vascular anomalies that may require a different operative approach.

Helical CT angiography may provide images that may be as accurate as arteriograms.¹¹,¹² Three-dimensional reconstruction of these images can produce representations of the vascular anatomy and pathology. This is being utilized by some to evaluate the aorta. Although compelling, technical limitations and artifacts occur often enough to currently limit its use for brachiocephalic vessels. Currently, its reliability is being evaluated.

Magnetic resonance angiography can generate similar images, but unfortunately its application in these potentially unstable trauma patients is not currently practical due to the difficulty in monitoring and managing the patient in the magnetic resonance imaging (MRI) coil. Transesophageal echocardiography has not been helpful in the management of brachiocephalic vessel injuries because it provides limited views of the aortic arch and brachiocephalic vessels.¹³,¹⁴

Arteriography

In penetrating thoracic trauma, if the patient is hemodynamically stable, arteriography is indicated for suspected innominate, carotid, or subclavian arterial injuries. Information gained from arteriography is important because different thoracic incisions are required for vascular control of each of these brachiocephalic vessels (see Fig. 1). The proximity of a missile trajectory to the brachiocephalic vessels, even without any physical findings of vascular injury, can be an indication for arteriography. Although arteriography of the aorta may be useful in hemodynamically stable patients with suspected penetrating aortic injuries, its limitations due to the large dye column obscuring small injuries in this setting must be recognized. Therefore, if performed, an effort must be made to
obtain views tangential to possible injuries for penetrating trauma.

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