Traumatic Aortic Injury

Traumatic aortic injury is disruption of the aortic wall from blunt or penetrating trauma, ranging from an intimal tear to free rupture. Most blunt injuries occur at the aortic isthmus, just distal to the left subclavian artery, from deceleration.

About 80% of patients with blunt aortic rupture die at the scene. Among those reaching hospital alive, untreated mortality is about 30% in the first 24 hours and rises steeply afterwards, so early recognition and repair save lives.

Mechanisms are high speed road traffic collisions (including side impact and ejection), falls from over 3 m, crush and blast. The injury often occurs with head, chest, abdominal and pelvic trauma, which dominate early management.

Injury grading:

• Grade I: intimal tear.
• Grade II: intramural haematoma.
• Grade III: pseudoaneurysm.
• Grade IV: free rupture.

Sites are the isthmus (about 90%), the ascending aorta and arch, the descending thoracic aorta and the abdominal aorta.

Pathophysiology.

Rapid deceleration shears the aorta between mobile segments (arch, heart) and fixed segments (ligamentum arteriosum, isthmus). Compression of the aorta between the sternum and the spine, and a sudden rise in intraluminal pressure, add to injury.

Intimal and medial tears allow blood to dissect or form a pseudoaneurysm contained by adventitia and mediastinal pleura. Containment is fragile, so rupture can occur within hours.

Rising blood pressure and heart rate (shear force) increase the risk of progression, which is the basis for anti-impulse therapy.

Recognition depends on mechanism and a high index of suspicion, since up to half of patients have no external chest signs. Features are chest or interscapular back pain, dyspnoea, hoarseness, upper limb hypertension with weak femoral pulses (pseudocoarctation), differing arm blood pressures, a systolic murmur over the precordium or between the scapulae, signs of chest wall injury, haemothorax, and hypotension (which usually has another source, such as abdominal or pelvic bleeding).

Rapid investigations (within the first 10 to 30 minutes, in parallel with resuscitation):

• Chest radiograph (supine): mediastinal widening over 8 cm, obscured aortic knob, left apical cap, rightward tracheal and nasogastric tube deviation, depressed left main bronchus, left haemothorax, first and second rib fractures. A normal film does not exclude injury.
• Extended focused ultrasound (eFAST) for haemopericardium, haemothorax and intra-abdominal bleeding.
• CT angiography of the chest, abdomen and pelvis (ECG-gated where available) is the definitive test, defining injury grade, length, relation to the left subclavian artery, branch vessels and aortic dimensions for planning.
• Transoesophageal echocardiography in an unstable patient who cannot go to CT, or intravascular ultrasound at the time of repair.
• Blood tests: group and cross-match with early activation of massive transfusion, full blood count, coagulation screen, fibrinogen, lactate, arterial blood gas, creatinine, troponin.

Differential diagnosis.

• Mediastinal haematoma from venous or small arterial bleeding, and ductus diverticulum (smooth contour, obtuse angles).
• Aortic dissection of atherosclerotic or connective tissue cause.
• Cardiac contusion, tamponade and tension pneumothorax.
• Haemorrhagic shock from other sources.

Minutes 0 to 10 (trauma team activation).

• Airway, breathing and circulation. Control external haemorrhage. Two large bore intravenous lines. Oxygen to SpO2 over 94%.
• Massive haemorrhage: red cells, plasma and platelets in a ratio of about 1:1:1, with fibrinogen if under 1.5 g/L, and calcium chloride 1 g intravenously for each 4 units. Tranexamic acid 1 g intravenously over 10 minutes within 3 hours of injury, then 1 g over 8 hours.
• Haemorrhagic shock: permissive hypotension (systolic 80 to 90 mmHg) until bleeding is controlled. Avoid permissive hypotension in severe head injury (aim for systolic 110 mmHg or more) and spinal cord injury (mean arterial pressure 85 to 90 mmHg).
• Intubation when needed: ketamine 1 to 2 mg/kg, rocuronium 1 mg/kg, with fentanyl 1 to 2 microgram/kg to blunt the pressor response. Avoid cough, straining and hypertensive surges.
• Chest drain for haemothorax. A left haemothorax of over 1500 mL at once, or continuing drainage over 200 mL/h, needs thoracotomy.

Minutes 10 to 60: anti-impulse therapy once the aortic injury is suspected and the patient is not in haemorrhagic shock.

• Target heart rate under 80 beats/min and systolic blood pressure 100 to 120 mmHg (mean arterial pressure 60 to 70 mmHg), without compromising cerebral and renal perfusion.
• Esmolol 500 microgram/kg intravenous bolus over 1 minute, then 50 microgram/kg/min, increased by 50 microgram/kg/min every 4 minutes to a maximum of 200 microgram/kg/min (avoid in bradycardia, block or asthma; reduce in heart failure). Alternative: metoprolol 2.5 to 5 mg intravenously every 5 minutes to a maximum of 15 mg.
• Add a vasodilator only after beta blockade to prevent reflex tachycardia: nicardipine 5 mg/h intravenously, increased by 2.5 mg/h every 5 to 15 minutes to a maximum of 15 mg/h.
• Analgesia: fentanyl 25 to 50 microgram intravenously, repeated by response, to reduce pain driven surges.

Definitive treatment by grade.

• Grade I: medical therapy with anti-impulse treatment and repeat CT angiography within 7 days (earlier with change); most heal or remain stable. Intervene for progression.
• Grade II to III: thoracic endovascular aortic repair, usually within 24 hours once the patient is stable, and delayed (hours to days) when severe head injury, pulmonary contusion or other injuries make early repair hazardous, with strict anti-impulse control meanwhile.
• Grade IV (free rupture or active extravasation): immediate repair, within the hour, by endovascular or open surgery.
• Endovascular technique: femoral or iliac access (conduit if vessels are small), minimal oversizing of the graft (0 to 10%, since the young aorta is not diseased and dilates), and coverage of the left subclavian artery when needed. Revascularise the left subclavian artery (carotid subclavian bypass or transposition) selectively for a dominant left vertebral artery, a left internal mammary graft, or a risk of spinal cord ischaemia. Heparin during stent graft placement only when bleeding risk allows, at a reduced dose (50 to 100 units/kg), and omit it with intracranial or uncontrolled bleeding.
• Open repair (clamp-and-sew, or with left heart bypass) for ascending aorta and arch injuries, for unsuitable access or aortic anatomy, and for failed endovascular repair.
• Spinal cord protection: avoid hypotension, keep mean arterial pressure over 80 mmHg after repair, and use cerebrospinal fluid drainage for long coverage or neurological signs.

After repair. Intensive care. Neurological checks of the legs hourly for 24 hours. Antithrombotic therapy is individualised (aspirin 75 to 100 mg daily when bleeding risk allows; many centres use none after trauma). Monitor for stroke, paraplegia, access complications, endoleak, stent graft collapse (bird beak configuration in small aortas), and contrast kidney injury.

Monitoring. Blood pressure and heart rate continuously for 48 to 72 hours. CT angiography at 1 month, 6 months and 12 months, then every 1 to 2 years (MR angiography where feasible in the young to limit radiation). Lifelong surveillance after stent graft in a young patient.

Referral and escalation. Transfer every suspected injury to a trauma centre with vascular and cardiothoracic surgery without delay. Activate the aortic team on CT confirmation. Treat any unstable patient with a suspected aortic injury as requiring immediate theatre or hybrid room assessment.

Special groups.

• Pregnancy: left lateral tilt; CT angiography is not withheld; early obstetric input; foetal monitoring; endovascular repair preferred to open surgery where possible.
• Children: small aortas limit stent graft use, so open repair or custom devices are used; anti-impulse therapy with dosing by weight.
• Older adults: atherosclerosis alters aortic wall and access; use lower anti-impulse targets.
• Kidney impairment: use contrast as needed but with hydration and minimal volume afterwards.