Rosen & Barkin's 5-Minute Emergency Medicine Consult (62 page)

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See Also (Topic, Algorithm, Electronic Media Element)

Tricyclic Antidepressant Poisoning

CODES

• 969.00 Poisoning by antidepressant, unspecified
  
• 969.02 Poisoning by selective serotonin and norepinephrine reuptake inhibitors
  
• 969.05 Poisoning by tricyclic antidepressants
  

BASICS

• Aortic dissection begins when there is an intimal tear.
  
• Blood then dissects through the media under aortic systolic pressure.
  
• It is thought that hypertension is a major factor in the dissection process.
  
• Dissections can start proximally at the root and dissect distally to involve any or all branches of the aorta, such as the carotid and subclavian arteries.
  
• The dissection process can also proceed proximally to involve the aortic root, the coronary ostia, and the pericardium.
  
• Dissection that progresses proximally may lead to occlusion of the coronary ostia, aortic valve incompetence, or cardiac tamponade.
  
• Classification related to portion of aorta involved:
  
  • Stanford classification:
    
    • Type A: Ascending aorta
      
    • Type B: Distal to ascending aorta
      
  • DeBakey classification:
    
    • DeBakey I: Intimal tear in aortic arch or root
      
    • DeBakey II: Ascending aorta
      
    • DeBakey III: Distal to takeoff of left subclavian artery
      
• Peak age for occurrence:
  
  • Proximal dissection: 50–55 yr
    
  • Distal dissection: 60–70 yr
    

Risk of dissection increases in the presence of pregnancy:

• In women <40 yr of age, 50% of dissections occur during pregnancy.
  

Any process that affects the mechanical properties of the aortic wall can lead to dissection:

• Hypertension (72% of patients in the Registry of Acute Aortic Dissection)
  
• Congenital heart disease (bicuspid aortic valve, coarctation)
  
• Aortic wall connective tissue abnormalities (cystic medial necrosis)
  
• Connective tissue disease (Marfan disease, Ehlers–Danlos syndrome)
  
• Pregnancy
  
• Infectious/inflammatory conditions that can cause vasculitis (lupus, syphilis, endocarditis, giant cell arteritis, rheumatoid arthritis, Takayasu arteritis)
  
• Previous cardiac surgery including CABG, aortic valve repair
  
• Tobacco use
  

DIAGNOSIS

• Chest pain:
  
  • May be absent in as many as 15% of patients
    
  • Substernal if type A dissection
    
  • Intrascapular if descending thoracic dissection
    
  • Lumbar if abdominal aorta involved
    
  • Starts abruptly
    
  • Usually described as sharp
    
  • Most severe at onset
    
• Back pain:
  
  • Commonly interscapular or lumbar
    
• Combination of chest, back, and abdominal pain
  
• Neurologic complaints:
  
  • Visual changes
    
  • Stroke symptoms
    
• Aortic dissection may present with atypical symptoms that can result in a delay of diagnosis
  
  • Abdominal pain
    
  • Chest pressure
    
  • Leg pain
    
  • Syncope
    
  • Fever
    
  • Nausea, vomiting
    

Elderly are less likely to undergo surgery and have a higher mortality rate

• Elderly are less likely to describe their pain as abrupt in onset, have a pulse deficit, or have aortic insufficiency
  

• HTN:
  
  • 35–40% may be normotensive.
    
• Pulse deficits:
  
  • Discrepancies in BP between limbs
    
  • Usually in upper extremities
    
• Neurologic/spinal cord deficits
  
• Murmur of aortic regurgitation:
  
  • Occurs in up to 31% of patients
    
  • Musical, vibrating quality with variable intensity
    
  • Heard best along right sternal border
    
• Shock
  
  • If pericardial rupture or myocardial infarction (MI) from dissection into a coronary artery
    
• Atypical presentations
  
  • Ischemic lower extremity
    
  • Altered mental status
    
  • Congestive heart failure
    

ECG:

• Useful in ruling in or out ST-elevation MI or ischemia
  
• Dissection may involve coronary ostia and cause MI:
  
  • Inferior MI (right coronary artery lesion) is more common than left coronary artery territory.
    
• Useful for evaluating the presence of left ventricular hypertrophy
  
• A normal ECG in the presence of severe, acute-onset chest/back pain should heighten one’s suspicion of an aortic dissection.
  

• Leukocytosis
  
• Hematuria
  
• Elevated BUN and creatinine
  
• Elevated amylase secondary to bowel ischemia
  
• Elevated cardiac enzymes due to myocardial ischemia
  
• D-dimer <500 ng/mL makes the diagnosis of dissection unlikely
  

• CXR:
  
  • Useful in excluding other etiologies such as pneumothorax and pneumonia
    
  • In dissection, there may be a widened mediastinum or abnormal aortic contour.
    
  • An enlarged heart secondary to pericardial fluid (blood) may be present.
    
  • May be completely normal in as many as 12–18% of cases
    
• Echo—transthoracic or transesophageal:
  
  • Transthoracic:
    
    • Not very helpful in the diagnosis of aortic dissection
      
    • May be used to evaluate for complications of a known dissection such as tamponade, valvular incompetence, or MI (from ostial occlusion)
      
  • Transesophageal:
    
    • May be performed in the ED
      
    • Patients may require intubation.
      
    • Provides information regarding extent of dissection and complications
      
• CT:
  
  • Very useful in defining extent of dissection
    
  • May also be used in diagnosing clinical entities such as pulmonary embolism
    
  • Has a high sensitivity for the diagnosis of aortic dissection and is the diagnostic modality of choice in many centers
    
• MRI:
  
  • Highly sensitive and specific
    
  • Requires patient transport out of ED for extended period of time
    
  • Lack of immediate availability may be a problem
    
  • Study of choice in those with renal insufficiency or dye allergy
    
• Aortography:
  
  • High sensitivity and specificity
    
  • Useful for preoperative planning
    
  • Difficult to obtain in many centers
    
• Cardiac catheterization:
  
  • Due of overlap of symptomatology with cardiac ischemia, some patients may have diagnosis made by cardiac catheterization when an intimal flap is visualized.
    

• MI/ischemia
  
• Unstable angina
  
• Pneumothorax
  
• Esophageal rupture
  
• Pulmonary embolism
  
• Pericarditis
  
• Pneumonia
  
• Musculoskeletal pain
  

TREATMENT