Abdominal aortic aneurysm

(Redirected from AAA)

Background

Aortic sebments.
Branches of the aorta.
CT reconstruction image of an abdominal aortic aneurysm (white arrows).
  • 2 Different types
    • Fusiform- Bulging or ballooning of all sides of the aorta; more common
    • Saccular- Bulging or ballooning of only one side of the aorta
  • Infrarenal diameter >3cm or >50% increase in size of diameter
    • 85% of cases are infrarenal [1]
  • M to F ratio is 4:1
  • Rupture Risk
    • <4cm: low risk for rupture
    • 4-5cm: 5 year risk 3-12%
    • >5cm: 25-41%
    • Rupture possible at any size, most commonly >5cm
    • Mortality with rupture: 85-90% [1]

Risk Factors

  • Smoking
    • Risk factor most strongly associated with AAA
    • Also promotes the rate of aneurysm growth
    • Direct relationship between risk and number of smoking years
  • Age (prevalence is negligible in age <50yrs)
  • Family history
  • Hypertension
  • Hyperlipidemia
  • Fluoroquinolone use [2]

Clinical Features

  • Classic triad (only 50% of cases) is pain + hypotension + pulsatile mass
    • Pain often described as sudden, severe, radiating to back, ripping quality
  • Syncope (10%)
  • Signs of Retroperitoneal hemorrhage
  • Massive GI bleed from aortoenteric fistula
  • Pain + AAA = rupture until proven otherwise
  • Acute abdomen + hypotension = possible rupture
  • Gross hematuria can be caused by an aortocaval fistula (very rare)
  • Unruptured aneurysms are frequently asymptomatic

Differential Diagnosis

Diffuse Abdominal pain

Lower Back Pain

Evaluation

AAA
Ultrasound of AAA with Thrombus (click to view).[3]
Abdominal aortic aneurysm seen on CT with a small area of remaining blood flow (white).
Sagital reconstruction of aortic aneurysm
  • Labs
    • Coagulation studies
    • Creatinine
    • Urinalysis
    • CBC
    • Type and cross-match blood


  • Imaging
    • Ultrasound
      • ~99% sensitive/98% specific for increased diameter[4]
      • Cannot reliably visualize rupture (only 4% sensitive)[5]
    • CT
      • ~100% sensitive for increased diameter and rupture
      • IV contrast is preferred but not essential

Management

Rupture

Ruptured AAA with an open arrow marking the aneurysm and the closed arrow marking the free blood in the abdomen.
  • Do not waste time in ED trying to "stabilize" patient
  • Immediate surgery consultation/ go to OR
  • Crossmatch 6 units of pRBC
  • Pain control (avoid hypotension)
  • Antihypertensives (use with caution, goal SBP 110-120 mmHg or MAP 70-80)[6]
    • Labetalol: 20mg IV, then 40-80mg IV q10 min (max 300mg)
    • Esmolol: Bolus 500 mcg/kg, then 50-200 mcg/kg/min
    • Nitroprusside: 0.3 - 0.5 mcg/kg/min, titrate to max 10 mcg/kg/min
  • Controversial
    • Too little (ischemia), too much (increased bleeding)
      • Consider allowing for permissive hypotension (SBP 70-90) in conscious patient[7]
    • Pressors
      • Norepinephrine 0.05mcg/kg/min IV; titrate by 0.02mcg/kg/min q5min
      • Phenylephrine 100-180mcg/min; titrate by 25mcg/min q10min
      • Dopamine 5mcg/kg/min; titrate by 5mcg/kg/min q10min

Asymptomatic

  • Aneurysm > 5 cm: Prompt (within days) vascular surgery outpatient follow-up appt
    • Endovascular (75%) vs open repair
  • Aneurysm 3-5 cm: Can likely follow up with PCP/surgeon on non-urgent basis
  • Screening frequency:
    • 3-4 cm diameter: 12 months
    • 4-5 cm diameter: 6 months
    • 5-6 cm diameter: 1 month
  • Elective Surgery indicated if:
    • AAA > 5.5 cm in men [1]
    • AAA > 5 cm in women [1]
    • increase in size > 1 cm/year
    • increase in size > 5 mm/6 months

Complications

Disposition

  • Admit to OR for ruptured or symptomatic AAA
  • May discharge asymptomatic cases with close vascular surgery follow up
    • Instruct to return immediately if symptoms manifest (abdominal/back pain, syncope, dizziness, extremity pain)

External Links

References

  1. 1.0 1.1 1.2 1.3 Kent, K. Abdominal Aortic Aneurysms. The New England Journal of Medicine. 2014; 371:2101-8. DOI: 10.1056/NEJMcp1401430
  2. P. Wendling for Medscape. FDA Warns of Aortic Aneurysm Risk with Fluoroquinolones. https://www.medscape.com/viewarticle/906867. Accessed 12/26/2018.
  3. http://www.thepocusatlas.com/aorta-1/
  4. Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med. 2013;20(2):128-138. doi:10.1111/acem.12080
  5. Rubano E, Mehta N, Caputo W, Paladino L, Sinert R. Systematic review: emergency department bedside ultrasonography for diagnosing suspected abdominal aortic aneurysm. Acad Emerg Med. 2013;20(2):128-138. doi:10.1111/acem.12080
  6. Reed, K. Aortic Emergencies, EB Medicine. 2006.
  7. Chaikof EL, Dalman RL, Eskandari MK, et al. The Society for Vascular Surgery practice guidelines on the care of patients with an abdominal aortic aneurysm. J Vasc Surg. 2018;67(1):2-77.e2. doi:10.1016/j.jvs.2017.10.044