Abdominal aortic aneurysm

Background

• Infrarenal diameter >3cm or >50% increase in size of diameter
• Rupture Risk
  • <4cm: low risk for rupture
  • 4-5cm: 5 year risk 3-12%
  • >5cm: 25-41%
  • Rupture poss at any size, most commonly >5cm

Risk Factors

• Age
  • Prevalence is negligible in age < 50 yrs
• Smoking
  • Risk factor most strongly assoc with AAA
  • Also promotes the rate of aneurysm growth
• Family history
• HTN

Clinical Features

• Triad: pain + hypotension + pulsatile mass
  • Pain often described as sudden, severe, radiating to back
• Syncope (10%)
• Pain + AAA = rupture until proven otherwise
• Acute abdomen + hypotension = possible rupture
• Signs of Retroperitoneal hemorrhage

Differential Diagnosis

Diffuse Abdominal pain

• Abdominal aortic aneurysm
  • Aortocaval fistula
• Acute gastroenteritis
• Aortoenteric fisulta
• Appendicitis (early)
• Bowel obstruction
  • Large bowel obstruction
    • Ogilvie's syndrome
  • Small bowel obstruction
  • Malignant bowel obstruction
• Bowel perforation
• Diabetic ketoacidosis
• Gastroparesis
• Hernia
• Hypercalcemia
• Inflammatory bowel disease
• Mesenteric ischemia
  • Mesenteric vein thrombosis
• Pancreatitis
• Peritonitis
• Sickle cell crisis
• Spontaneous bacterial peritonitis
• Volvulus

Lower Back Pain

• Spine related
  • Acute ligamentous injury
  • Acute muscle strain
  • Disk herniation (Sciatica)
  • Degenerative joint disease
  • Spondylolithesis
  • Epidural compression syndromes
    • Spinal cord compression (non-traumatic)
    • Cauda equina syndrome
    • Conus medullaris syndrome
    • Epidural abscess (spinal)
    • Epidural hematoma (spinal)
  • Thoracic and lumbar fractures and dislocations
  • Cancer metastasis
  • Spinal stenosis
  • Transverse myelitis
  • Vertebral osteomyelitis
  • Ankylosing spondylitis
  • Spondylolisthesis
  • Discitis
  • Spinal Infarct
• Renal disease
  • Kidney stone
  • Pyelonephritis
  • Nephrolithiasis
• Intra-abdominal
  • Abdominal aortic aneurysm
  • Ulcer perforation
  • Retrocecal appendicitis
  • Large bowel obstruction
  • Pancreatitis
• Pelvic disease
  • PID
• Other
  • Retroperitoneal hemorrhage/mass
  • Meningitis

Diagnosis

AAA

• Ultrasound
  • ~100% sensitive for increased diameter
  • Cannot reliably visualize rupture

• CT
  • ~100% sensitive for incr diameter and rupture
  • IV contrast is preferred but not essential

Management

Rupture

• Do not waste time in ED trying to "stabilize" pt
• 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)
      • Labetalol: 20 mg IV, then 40-80 mg 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 80-100) in conscious pt
    • Pressors
      • Norepi 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

• Prompt vascular surgery outpatient follow-up appt
• 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
  • AAA > 5 cm in women
  • increase in size > 1 cm/year
  • increase in size > 5 mm/6 months