REBEL Core Cast 82.0 – Abdominal Aortic Aneurysm

Jun 08, 22
REBEL Core Cast 82.0 – Abdominal Aortic Aneurysm

Take Home Points

  • Consider AAA in patients with acute onset of back or abdominal pain particularly in patients > 50 and in those with a history of hypertension
  • Consider ruptured AAA in patients (especially those > 50 years of age) with unexplained hypotension, back or abdominal pain
  • All ruptured AAAs should be considered unstable regardless of vital signs as rapid deterioration is common
  • A ruptured AAA is 100% fatal without surgical or endovascular intervention. Mobilize your surgical colleagues early

REBEL Core Cast 82.0 – Abdominal Aortic Aneurysm

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Definition: An abdominal aortic aneurysm (AAA) is localized dilation (> 3 cm) of the aorta caused by a weakening involving all three layers (intima, media and adventitia) of the aortic wall. It most commonly develops distal to the renal arteries.

Epidemiology: 

  • Uncommon in patients < 50 yo
  • Found in 2-5% of men > 50 yo
  • It is more common:
    • In men than women
    • In patients with coronary artery disease (CAD) or peripheral arterial disease (PAD)
    • Patients with a family history of AAA
    • Smokers
  • Up to 50% of AAA in patients < 65 occur in women
  • Mortality
    • 30-40% with open aortic repair
    • 20-25% with endovascular repair

Presentation

Unruptured Aneurysm

  • Signs and Symptoms
    • Most AAAs are asymptomatic until expansion or rupture occurs
    • Pain is a common symptom when symptoms are present
      • Abdominal, back and/or flank pain
      • Acute pain associated with a AAA can mimic renal colic
      • Acute pain may be an ominous sign of impending rupture
  • Physical Exam
    • Large aneurysms may be found on routine abdominal examination as pulsatile abdominal masses
    • May be limited secondary to patient body habitus and size of aneurysm
    • Abdominal bruits are uncommon findings
  • Complications of unruptured AAAs
    • Thromboembolic: lower extremity ischemia
    • Direct compression of adjacent structures (duodenum, ureters etc)

Ruptured Aneurysm

  • Classic Triad: Pain, hypotension and a pulsatile abdominal mass. Often will only see one or two features of the triad
  • Symptoms
    • Pain is the most common symptom
      • Abdominal, back and/or flank
      • Typically acute in onset, severe and can radiate to the chest, back or groin
      • Acute onset of pain in a patient with a AAA should be assumed to be secondary to rupture
    • Syncope (or near-syncope) is common though hemodynamic compensation may result in near-normalization of blood pressure
  • Physical Exam
    • Large, palpable abdominal mass
    • Aortic pulsation may be felt (may be absent if blood pressure is low)
    • Hypotension
      • Seen in 50% of ruptures on presentation (Gaughan 2009, Rose 2001)
      • Late finding suggestive of impending hemodynamic collapse and death
    • Tachycardia may be variably present
      • Many patients are on beta-blockers at baseline
      • Blood in the abdomen can stimulate vagal responses leading to lower than expected heart rate
  • AAA Variants
    • Aortoenteric fistula
      • Definition: AAA rupture into the GI tract that can be either primary (from an unrepaired AAA) or secondary (after prior aortic repair)
      • Consider diagnosis in any patient with a known AAA or prior repair who presents with GI bleeding
      • Can see both hematemesis and melena as the aortoenteric fistula commonly connects the AAA to the duodenum
      • Patients will typically experience rapid, massive exsanguination. Aortoenteric fistula has a very high morbidity and mortality
    • Aortocaval fistula
      • Definition: Periaortic inflammation leads to a connection between the AAA and the adjacent vena cava.
      • Free rupture of the AAA will present in same way as any ruptured AAA
      • Formation of a large arteriovenous (AV) fistula may occur if there is no external AAA leak
      • Signs and Symptoms (Cinara 2005)
        • Palpable mass (80-90%)
        • Abdominal bruit (75%)
        • Palpable thrill (25%)

Differential Diagnosis

  • Aortic Dissection
  • Ureteric Colic
  • Pancreatitis
  • Intestinal ischemia
  • Bowel obstruction
  • Diverticulitis

Diagnostics

  • Patients with ruptured aneurysms will often be diagnosed based on clinical presentation alone.
  • Ultrasound (INSERT IMAGES HERE)
    • Sensitivity for detecting AAA approaches 100% (Lederle 2003)
    • Detection of AAA rupture
      • Presence of free intraperitoneal fluid confirms rupture
      • Rupture may be retroperitoneal or small leading to a false negative US for free fluid
    • Advantages
      • Allows for rapid evaluation of the aorta as a cause for shock in the undifferentiated patient while resuscitation is ongoing
      • Obviates the need for the patient to be transported to the radiology department for imaging
      • Can provide alternative explanations for the patient’s presentation
    • Limitations
      • Prone to both technical (ultrasonographer skills) and interpretive error
      • Visualization of the aorta can be limited by obesity or the presence of bowel gas
      • Not as sensitive for detecting rupture
  • CT Scan
    • Abdominal CT has a sensitivity and specificity approaching 100% for both diagnosis of AAA as well as rupture (Hermsen 2004)
    • Addition of IV contrast can delineate the patent lumen of the AAA from the mural thrombus but is not necessary for identification of aneurysm or hemorrhage
    • More sensitive than US for detecting retroperitoneal hemorrhage of AAA
    • CT also helpful in identifying alternative diagnoses

Management

Regardless of vital signs, patients with ruptured AAA should be considered unstable and should be aggressively resuscitated. A ruptured AAA has a mortality rate > 80%. (Adam 1999)

Basics: ABCs, Large bore (> 16 gauge) IV X 2, Supplemental O2 (if needed), Cardiac 

Monitor + Immediate Surgical Consultation for repair

Aggressive Volume Resuscitation in Hypotensive patients

  • Target systolic blood pressure of 90-100 mm Hg pre-operatively
    • Exact target unknown
    • Over-resuscitation may contribute to increased bleeding from dilutional coagulopathy
    • Under-resuscitation harmful as prolonged hypotension can lead to end-organ damage (myocardial infarction, renal failure) and cardiac arrest
  • Start with administration of uncrossmatched blood
  • Activate massive transfusion protocol as patients often have large transfusion requirements
  • Consider administration of a 1:1:1 (PRBC:FFP:Platelets) ratio of blood products
  • Administer reversal agents for anticoagulant use if indicated

Take Home Points

  • Consider ruptured AAA in patients (especially those > 50 years of age) with unexplained hypotension, back or abdominal pain
  • All ruptured AAAs should be considered unstable regardless of vital signs as rapid deterioration is common
  • A ruptured AAA is 100% fatal without surgical or endovascular intervention. Mobilize your surgical colleagues early

Read More

  • Bessen HA, Poffenberger CM: Abdominal Aortic Aneurysm, in Marx JA, Hockberger RS, Walls RM, et al (eds): Rosen’s Emergency Medicine: Concepts and Clinical Practice, ed 8. St. Louis, Mosby, Inc., 2010, (Ch) 86: p 1129-1140.

References

  1. Adam DJ et al. Community and hospital outcome from ruptured abdominal aortic aneurysm within the catchment area of a regional vascular surgical service. J Vasc Surg 1999; 30:922-928. PMID: 10550191
  2. Cinara IS et al: Aorto-caval fistulas: A review of eighteen years experience. Acta Chir Belg 2005; 105:616-620. PMID: 16438071
  3. Gaughan M et al. Emergency abdominal aortic aneurysm presenting without haemodynamic shock is associated with misdiagnosis and delay in appropriate clinical management. Emerg Med J 2009; 26:334-339. PMID: 19386866
  4. Hermsen K, Chong WK. Ultrasound evaluation of abdominal aortic and iliac aneurysms and mesenteric ischemia. Radiol Clin North Am 2004; 42:365-381. PMID: 15136022
  5. Lederle FA: Ultrasonographic screening for abdominal aortic aneurysms. Ann Intern Med 2003; 139:516-522. PMID: 24957320
  6. Rose J et al. Ruptured abdominal aortic aneurysms: Clinical presentation in Auckland 1993-1997 ANZ J Surg 2001; 71: 341-4. PMID: 11409018

Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)

The post REBEL Core Cast 82.0 – Abdominal Aortic Aneurysm appeared first on REBEL EM - Emergency Medicine Blog.

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