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Aortic Rupture, Traumatic (TAI), Emergency Medicine

Basics

Description

- Helical chest CT angiography: - Preferred confirmatory study in stable patients - Nearly 100% sensitivity and specificity for detecting aortic rupture with improved CT technology - Has largely eliminated need for aortography - Advantages over aortography include noninvasive, provides information on other thoracic structures, more rapid

- MRI: - High accuracy - Lengthy study time and difficulty monitoring patients limit use

- Intravascular US: - Newer modality, availability is limited - Preliminary data suggest high sensitivity and specificity.

  • Traumatic aortic rupture (also referred to as traumatic aortic injury or TAI) is the cause of death in an estimated 20% of lethal motor vehicle collisions.
  • An estimated 85% of patients with TAI die before reaching the hospital.
  • Patients surviving to the ED usually have a contained rupture as aortic blood is tamponaded by the adventitia.
  • Without proper treatment, of the 15% that survive the initial event, 49% will die within the 1st 24 hr, and 90% within 4 mo.
  • Mean age of patients sustaining aortic rupture is 33 yr, and 70% are male.
  • Most tears are transverse, not longitudinal.
  • Tears may be partially or completely circumferential.

Etiology

  • Most commonly results from motor vehicle collisions >30 mph
  • Unrestrained passengers, driver seat occupants (injuries from steering column and instruments), and ejected occupants.
  • Other mechanisms: Auto versus pedestrian, airplane crashes, falls from height >10 ft, crush and blast injuries, direct blow to chest
  • Proposed mechanisms of aortic injury:Shear forces arising from unequal rates of deceleration of the relatively fixed descending aorta and the more mobile arch"Bending"пїЅ stress at the aortic isthmus may cause flexion of the aortic arch on the left mainstem bronchus and pulmonary artery.Twisting of the arch forces it superiorly and causes it to stretch.Osseous structures (e.g., medial clavicles, manubrium, 1st rib) cause pinching of the trapped aorta as they strike the vertebral column."Waterhammer"пїЅ fluid wave causes explosive rupture of aorta just distal to the aortic valve.

Diagnosis

Signs and Symptoms

Despite the severe nature of the injury, clinical manifestations are often deceptively subtle or nonexistent as patients frequently present with multiple coexisting injuries. 1/3-1/2 of these patients do not have external signs of chest trauma. пїЅ

History

  • Substernal chest pain is the most common symptom, but only present in ~25% of cases.
  • Dyspnea, hoarseness, and stridor (tracheal compression from expanding hematoma) are less common.

Physical Exam

  • Neither sensitive nor specific for aortic injury
  • Generalized HTN may occur from stimulation of sympathetic afferent nerves located near aortic isthmus.
  • Harsh precordial or midscapular systolic murmur (1/3 of patients)
  • Ischemic pain in lower extremities, oliguria/anuria, paraplegia from decreased aortic blood flow distal to aortic arch
  • Swelling of base of neck (extravasation of blood)
  • Acute coarctation syndrome (1/3 of patients): Upper extremity HTN with decreased pressures in low extremities, caused by periaortic hematoma compressing aortic lumen

Essential Workup

Plain CXR is the primary screening tool with ~90% sensitivity, but low specificity. пїЅ

Diagnosis Tests & Interpretation

Lab

  • CBC
  • Chemistry
  • Prothrombin time/partial thromboplastin time
  • Type and cross-match (6-8 units PRBC)

Imaging

  • Plain CXR:Findings suggestive of mediastinal hemorrhage, hematoma, or associated injuries:Widening of the superior mediastinum at the level of aortic arch (defined as >8 cm on a supine film, >6 cm in an upright PA film, or >0.25 mediastinum-width to chest-width ratio) is the most sensitive sign.Obscuration of the aortic knob is also a sensitive sign.More specific, but less sensitive, signs include opacification of the aortopulmonary window, rightward displacement of nasogastric tube, widened paratracheal stripe, and widened right paraspinal interface.7-10% false-negative rate with normal mediastinum on x-ray; consider use of helical chest CT with high-speed deceleration mechanisms.In pediatric patients: The most common findings are a left apical cap, pulmonary contusion, aortic obscuration, and mediastinal widening.
  • Helical chest CT angiography:Preferred confirmatory study in stable patientsNearly 100% sensitivity and specificity for detecting aortic rupture with improved CT technologyHas largely eliminated need for aortographyAdvantages over aortography include noninvasive, provides information on other thoracic structures, more rapid
  • Aortography:Still considered by some to be the gold standard for diagnosis of TAIProvides precise anatomic localization of aortic tears, useful for aorta injured at >1 site (15-20% of cases)Risk of further damage to aorta from catheterNeed for this modality is declining given advances in CT imaging quality.
  • Transesophageal Echo (TEE):Can be done rapidly in the EDCan detect associated cardiac injuries (contusion, effusion, etc.)Reported 87-100% sensitivity and 98-100% specificityContraindicated in patients with cervical, maxillofacial, or esophageal injuries
  • MRI:High accuracyLengthy study time and difficulty monitoring patients limit use
  • Intravascular US:Newer modality, availability is limitedPreliminary data suggest high sensitivity and specificity.

Presence of large thymus may make diagnosis of widened mediastinum difficult. пїЅ

Differential Diagnosis

  • Supine CXR can lead to false positive for widened mediastinum; obtain upright PA if possible.
  • Mediastinal hematoma owing to other causes
  • Mediastinal lymphadenopathy or tumor
  • Redundant aorta resulting from HTN

Treatment

Pre-Hospital

Important information to retrieve at scene of injury: пїЅ

  • Vehicular speed
  • Patient in driver or passenger seat
  • Damage to steering column if driver is patient
  • Ejection or use of seat belt

Initial Stabilization/Therapy

  • Follow advanced trauma life support protocols.
  • Life-threatening intracranial, peritoneal, and retroperitoneal injuries take precedence.

Ed Treatment/Procedures

  • Immediate trauma surgery consultation
  • Immediate cardiothoracic or vascular surgery consultation (institution dependent)
  • Avoid maneuvers that may result in a Valsalva-like response (e.g., gagging, straining)
  • Aggressive pharmacologic treatment of BP and heart rate, as emerging data suggest delaying surgical repair may lead to improved outcomes
  • Goal of medical therapy is to target heart rate 60 пїЅ 5 bpm, systolic BP 100-120 mm Hg, and mean arterial BP 70-80 mm Hg to decrease risk of sudden free rupture and exsanguination:β-blockers such as esmolol and labetalol are 1st-line agentsCalcium-channel blockers in patients with contraindications to β-blockade (CHF, COPD, 2nd- or 3rd-degree atrioventricular block)Add vasodilator (nitroprusside) if needed to reach target BP and heart rate goals.Antihypertensives are relatively contraindicated in acute coarctation syndrome.
  • For significant hypotension, initiate rapid volume expansion, including blood.
  • Vasopressors for refractory hypotension; norepinephrine and phenylephrine are preferred
  • Central venous and arterial catheters

Only administer vasodilator after initiating negative inotrope (β-blocker or calcium-channel blocker), as vasodilator alone can cause an increase in shearing forces on the intact aortic adventitia. пїЅ

Medication

  • Esmolol: 500 Ојg/kg bolus IV (peds: 100-500 Ојg/kg bolus), then 50-150 Ојg/kg/min IV infusion (peds: 25-100 Ојg/kg/min IV infusion)
  • Labetalol: 20 mg IV, followed by additional doses of 40 mg and 80 mg (peds: 0.2-10 mg/kg per dose, max. 20 mg per dose) IV q10-15min, to 300 mg IV total; start infusion at 2 mg/min and titrate up to 10 mg/min (peds: 0.4-3 mg/kg/h infusion)
  • Diltiazem: 20 mg (0.25 mg/kg) IV over 2 min; 2nd bolus 25 mg (0.35 mg/kg) in 15 min if needed; infusion 5-15 mg/h
  • Norepinephrine: Start with 0.5-1 Ојg/min and titrate to desired response; 8-30 Ојg/min is usual dose (peds: Start 0.05-0.1 Ојg/kg/min, max. 2 Ојg/kg/min)
  • Phenylephrine: 0.1-0.5 mg IV boluses q10-15min, initial dose not to exceed 0.5 mg (peds: 5-20 Ојg/kg/dose q10-15min); 100-180 Ојg/min or 0.5 Ојg/kg/min titrated to desired effect (peds: 0.1-0.5 Ојg/kg/min, titrated to desired effect)

Follow-Up

Disposition

Admission Criteria

All patients with aortic injuries must be admitted to the ICU if not taken directly to the OR. пїЅ

Followup Recommendations

All patients with TAI are admitted to the hospital. пїЅ

Pearls and Pitfalls

  • Maintain a high degree of suspicion for TAI in patients with injuries from significant deceleration mechanisms.
  • Clinical signs and symptoms may be subtle or nonexistent, necessitating some reliance on radiologic imaging for diagnosis.
  • Special attention should be given to assessment of the mediastinum on CXR in trauma patients.
  • Early pharmacologic control of BP and heart rate is of utmost importance when diagnosis is confirmed.

Additional Reading

  • Demetriades пїЅD, Velmahos пїЅGC, Scalea пїЅTM, et al. Blunt traumatic thoracic aortic injuries: Early or delayed repair-Results of an American Association for the Surgery of Trauma prospective study. J Trauma. 2009;66(4):967-973.
  • Kwolek пїЅCJ, Blazick пїЅE. Current management of traumatic thoracic aortic injury. Semin Vasc Surg. 2010;23(4):215-220.
  • Moore пїЅMA, Wallace пїЅEC, Westra пїЅSJ. The imaging of paediatric thoracic trauma. Pediatr Radiol. 2009;39(5):485-496. Review.
  • Ng пїЅCJ, Chen пїЅJC, Wang пїЅLJ, et al. Diagnostic value of the helical CT scan for traumatic aortic injury: Correlation with mortality and early rupture. J Emerg Med. 2006;30(3):277-282.
  • Weidenhagen пїЅR, Bombien пїЅR, Meimarakis пїЅG, et al. Management of thoracic aortic lesions-the future is endovascular. Vasa. 2012;41(3):163-176.

Codes

ICD9

  • 901.0 Injury to thoracic aorta
  • 902.0 Injury to abdominal aorta

ICD10

  • S25.01XA Minor laceration of thoracic aorta, initial encounter
  • S25.02XA Major laceration of thoracic aorta, initial encounter
  • S25.09XA Other specified injury of thoracic aorta, initial encounter
  • S35.02XA Major laceration of abdominal aorta, initial encounter
  • S35.01XA Minor laceration of abdominal aorta, initial encounter
  • S35.09XA Other injury of abdominal aorta, initial encounter

SNOMED

  • 126037009 Traumatic rupture of aorta (disorder)
  • 59568004 injury of thoracic aorta (disorder)
  • 10392004 injury of abdominal aorta (disorder)