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Classification

Abdominal aortic aneurysms may be classified based on the size of the aneurysm:

• Small aneurysm: Diameter < 4.0 cm
• Medium aneurysm: Diameter between 4.0 and 5.5 cm
• Large aneurysm: Diameter ≥ 5.5 cm
• Very large aneurysm: Diameter ≥ 6.0 cm

Abdominal aortic aneurysms may also be classified based on the rate of aneurysm expansion:

• Non-rapidly expanding aneurysm: Diameter increase of ≤ 0.5 cm within 6 months OR ≤ 1.0 cm within 12 months
• Rapidly expanding aneurysm: Diameter increase of > 0.5 cm within 6 months OR > 1.0 cm within 12 months

Causes

Life Threatening Causes

• Ruptured AAA
• Infected (mycotic) aneurysm
• Inflammatory AAA
• Aortovenous fistula
• Aortoenteric fistula
• Lower extremity thromboembolism

Risk Factors for Development of AAA

• Old age 50 > years
• Greater height
• Male gender
• Caucasian race
• Smoking
• History of CAD and atherosclerotic cardiovascular disease
• History of hypertension
• Dyslipidemia
• Family history of AAA
• Personal history of peripheral artery aneurysms

Risk Factors for Rapid Expansion or Rupture of AAA

• Female gender
• Advanced age > 50 years
• Smoking
• Advanced atherosclerosis
• History of prior stroke
• Hypertension
• Transplantation (cardiac or renal)
• Known reduced FEV1 (obstructive pulmonary disease)

FIRE: Focused Initial Rapid Evaluation

A Focused Initial Rapid Evaluation (FIRE) should be performed to identify patients in need of immediate surgical intervention. Boxes in red signify that an urgent management is needed.

Identify cardinal findings that increase the pre-test probability of abdominal aortic aneurysm (AAA) rupture and development of complications ❑ Known large AAA > 5.5 cm ❑ Known rapid AAA expansion rate > 0.5 cm/6 months OR 1.0 cm/year ❑ Known infective endocarditis (high risk for infected aneurysm) ❑ Acute abdominal/back pain that may radiate to buttocks, groin region, or lower extremities ❑ Tearing/sharp quality ❑ Increasing in intensity ❑ Pulsating abdominal mass ❑ Hypotension or shock ❑ Oliguria or anuria ❑ Muscular weakness ❑ Lower extremity numbness and/or tingling ❑ Cold extremities ❑ Peripheral cyanosis ❑ Acute limb pain ❑ Fever or sepsis ❑ Altered mental status ❑ Unexplained syncope ❑ Coma ❑ Presence of risk factors associated with rapid expansion or rupture of AAA ❑ Female gender ❑ Advanced age > 50 years ❑ Smoking ❑ Advanced atherosclerosis ❑ History of prior stroke ❑ Hypertension ❑ Transplantation (cardiac or renal) ❑ Known reduced FEV1 (obstructive pulmonary disease)

Rule out life threatening alternative diagnoses: ❑ Acute coronary syndromes (suggestive findings: Chest pain, Abdominal pain, back pain, interscapular pain, Hypotension, Dyspnea, Nausea, Cold sweats ❑ Peritonitis (suggestive findings: Abdominal pain, Abdominal guarding, Abdominal rigidity, Fever, Hypotension ❑ Bowel ischemia (suggestive findings: Abdominal pain, Vomiting, Fever, Absence of abdominal tenderness ❑ Perforated ulcer (suggestive findings: Abdominal pain, Vomiting, Hematemesis, Fever ❑ Intestinal obstruction (suggestive findings: Abdominal pain, Bilious vomiting, Abdmoninal tenderness, Fever, Abdmoninal distention ❑ Aortic dissection (suggestive findings: back pain, interscapular pain, aortic regurgitation, pulsus paradoxus, blood pressure discrepancy between the arms) ❑ Pulmonary embolism (suggestive findings: acute onset of dyspnea, tachypnea, hemoptysis, previous DVT) ❑ Cardiac tamponade (suggestive findings: hypotension, jugular venous distention, muffled heart sounds, pulsus paradoxus) ❑ Tension pneumothorax (suggestive findings: sudden dyspnea, tachycardia, chest trauma, unilateral absence of breath sound) ❑ Esophageal rupture (suggestive findings: vomiting, subcutaneous emphysema)

Stabilize and resuscitate the patient ❑ Attend to the patient's ABCs (Airway, Breathing, Circulation) ❑ Consider endotracheal intubation if the patient's airway is compromised, has a Glasgow coma scale (GCS < 8) or profound hemodynamic instability ❑ Administer oxygen and maintain a saturation >90% ❑ Secure 2 large-bore intravenous (IV) lines ❑ Administer fluids to reach a target systolic blood pressure (SBP) of 70 to 100 mm Hg. Excessive fluid administration in AAA is associated with worse outcomes ❑ Do NOT routinely administer vasopressors if patient is hypotensive at presentation. Vasopressor administration in AAA is controversial. Consider ANY of the following vasopressors only if patient remains hypotensive despite fluids ❑ Norepinephrine 0.05 microgram/kg/minute IV; titrate by 0.02 microgram/kg/minute every 5 minutes, OR ❑ Phenylephrine 100-180 microgram/minute; titrate by 25 microgram/minute every 10 minutes, OR ❑ Dopamine 5 microgram/kg/minute; titrate by 5 microgram/kg/minute every 10 minutes ❑ Obtain 12 lead ECG and place the patient on a cardiac monitor ❑ Place an indwelling urethral catheter and monitor urine output ❑ Frequently assess mental status and check for focal neurologic deficits ❑ Type and crossmatch 6 to 10 units of PRBC. FFP may also be needed in cases of massive transfusion ❑ Do not administer pre-op transfusions except if patient is unconscious or has signs or myocardial infarction ❑ Withdraw blood for CBC, electrolytes, BUN, serum creatinine, LFTS, PT, PTT, troponin I, CK, CK-MB, CRP or ESR, and multiple blood cultures Pain management ❑ Assess pain severity (self-report NRS scale 0 to 10; unconscious BPS 3-12 or CPOT 0-8). Pain considered significant if NRS≥4, BPS<5, or CPOT≥3 ❑ Administer IV opioids: Morphine 4-10 mg IV every 4 hours, infused over 4-5 minutes (dose range: 5-15 mg) ❑ Consider pre-op epidural catheter if patient meets ALL of the following criteria ❑ Patient hemodynamically stable, AND ❑ Contained leak, AND ❑ Satisfactory coagulation profile ❑ Maintain patient in a conscious state ❑ Monitor any significant undesired drop in blood pressure as pain medications are administered

Patient hemodynamically unstable despite resuscitation? ❑ Hypotension (SBP < 90 mm Hg) despite resuscitation ❑ Tachycardia (HR > 100 bpm) despite resuscitation

Yes. Patient is still hemodynamically unstable despite resuscitation.

No. Patient is hemodynamically stable following resuscitation

Is the patient known to have an AAA?

Can patient have CT scan with contrast?

Yes

No

Yes

No

❑ Proceed to operating room without further work-up

❑ Obtain focused bedside ultrasound

❑ Obtain CT scan with IV contrast of abdominal aorta and iliac arteries

❑ Obtain CT scan without IV contrast of abdominal aorta and iliac arteries

AAA confirmed on imaging?

Yes

No

Consider alternative diagnoses

Evaluate need for further management of the following AAA complications For patients suspected to have thromboembolism ❑ Obtain Duplex ultrasound of affected extremities ❑ Consider CT scan of aorta from aortic valves to iliac bifurcation For patients suspected to have infected (mycotic) aneurysm ❑ Consider gallium scanning or 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) to evaluate disease activity For patients suspected to have aortovenous fistula ❑ Obtain CT angiography For patients suspected to have aortoenteric fistula ❑ Perform EGD to rule out other possible etiologies of GI bleed among hemodynamically stable patients ❑ Obtain CT scan with IV contrast of the abdomen and iliac arteries ❑ Consider arteriography

Administer antimicrobial therapy Once diagnosis of complicated AAA is confirmed, all patients require blood cultures and empirical antibiotic therapy for gram-positive and gram-negative coverage (even if afebrile at presentation) ❑ Withdraw multiple sets of blood culture (if blood cultures were not withdrawn initially) ❑ Administer empiric combination antibiotic therapy ❑ Vancomycin 1-1.5g IV every 12 hours PLUS only one of the following: ❑ Ceftriaxone 2 g IV every 12 hours, OR ❑ Cefuroxime 1.5 g IV every 4 hours, OR ❑ Piperacillin-tazobactam

Proceed to further management

Treatment

Shown below is an algorithm summarizing the management of abdominal aortic aneurysm.

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Screening

Screening for AAA is currently recommended only once in the following patient groups:

• Men between the age of 65 and 75 years and who have ever smoked
• Men aged 60 years or older with a sibling or a parent with abdominal aortic aneurysm

There are currently no recommendations to screen AAA in women, but women are at increased risk of AAA expansion or rupture. Some experts recommend one-time screening in women with risk factors of developing AAA (such as smoking or positive family history)