Rosen & Barkin's 5-Minute Emergency Medicine Consult (63 page)

• Monitor
  
• IV access
  
• Oxygen
  

• 2 large-bore IV lines
  
• Continuous cardiac monitoring
  
• Pulse oximetry
  
• Oxygen
  
• Type and cross
  

• BP reduction to reduce shearing forces on aortic wall and slow down the dissection process
  
• Medications: IV β-blockade and nitroprusside
  
  • Medications are used to control HTN and cardiac contractility and decrease shearing forces.
    
  • Esmolol (IV) or labetalol (IV):
    
    • Contraindications: Bradycardia, COPD, hypotension
      
  • Nitroprusside (commonly used in conjunction with IV β-blocker)
    
  • Caution when using the above together: To prevent an initial increase in shear forces, β-blocker therapy should be started prior to the addition of nitroprusside therapy
    
• Emergent surgery:
  
  • Treatment of choice for type A dissection
    
  • Treatment for type B dissections in those who have failed medical therapy
    
• Medical management:
  
  • Treatment of choice for stable type B dissections
    

• Esmolol: 500 μg/kg IV bolus, then 25--50 μg/kg/min drip
  
• Labetalol: 10–20 mg IV over 2 min q10–15min. Then 2–4 mg/min IV drip. Total dose not to exceed 300 mg.
  
• Nitroprusside: 0.5 μk/kg/min IV and titrate upward to desired effect. Dose should be based on IBW.
  

FOLLOW-UP

• All patients with acute aortic dissection should be admitted to the intensive care unit.
  
• Emergency cardiothoracic surgery consultation should be obtained, especially in cases of type A dissection.
  

None

Close follow-up with cardiology and/or cardiothoracic surgery is of paramount importance.

• Untreated, nearly 75% of patients with ascending aortic dissection can be expected to die within 2 wk, with a mortality of 1–3%/hr in the 1st 48 hr.
  
• Majority of patients present with pain (90%) of severe intensity (90%) that occurred suddenly (84%).
  
• Although some recent literature has suggested a role for
  D
  -dimer testing, there is insufficient evidence to support its use as the sole screening test for aortic dissection.
  
• Should consider the diagnosis in patients with chest pain in whom conventional therapy (nitrates, β-blockers) are ineffective, and in those who have chest pain in addition to another complaint (extremity weakness, back pain, paresthesias, abdominal pain).
  
• Identification of risk factors is critical. These include:
  
  • HTN
    
  • Male gender
    
  • Cocaine use
    
  • Advanced age
    
  • Pregnancy
    
  • Connective tissue disorders, such as Marfan syndrome or cystic medial necrosis
    
  • Bicuspid aortic valve
    
  • Turner syndrome
    
  • Family history
    
  • Previous cardiac or valvular surgery
    

• Harris KM, Strauss CE, Eagle KA, et al. Correlates of delayed recognition and treatment of acute type A aortic dissection: The International Registry of Acute Aortic Dissection (IRAD).
  Circulation
  . 2011;124:1911–1918.
  
• Khan IA, Nair CK. Clinical, diagnostic, and management perspectives of aortic dissection.
  Chest
  . 2002;122(1):311–328.
  
• Klompas M. Does this patient have an acute thoracic aortic dissection?
  JAMA
  . 2002;287:2262–2272.
  
• Sutherland A, Escano J, Coon TP. D-dimer as the sole screening test for acute aortic dissection: a review of the literature.
  Ann Emerg Med
  . 2008;52(4):339–343.
  
• Suzuki T, Distante A, Zizza A, et al. Diagnosis of acute aortic dissection by D-dimer: The International Registry of Acute Aortic Dissection Substudy on Biomarkers (IRAD-Bio) experience.
  Circulation
  . 2009;119:2702–2707.
  

CODES

441.01 Dissection of aorta, thoracic

BASICS

• 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.
  

• 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” 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” fluid wave causes explosive rupture of aorta just distal to the aortic valve.
    

DIAGNOSIS

• 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.
  

• 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
  

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

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

• 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 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
    
• Aortography:
  
  • Still considered by some to be the gold standard for diagnosis of TAI
    
  • Provides precise anatomic localization of aortic tears, useful for aorta injured at >1 site (15–20% of cases)
    
  • Risk of further damage to aorta from catheter
    
  • Need for this modality is declining given advances in CT imaging quality.
    
• Transesophageal Echo (TEE):
  
  • Can be done rapidly in the ED
    
  • Can detect associated cardiac injuries (contusion, effusion, etc.)
    
  • Reported 87–100% sensitivity and 98–100% specificity
    
  • Contraindicated in patients with cervical, maxillofacial, or esophageal injuries
    
• 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.