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• An aneurysm is dilation of the arterial wall to >1.5 times it normal diameter.
• It can be either true, pseudo or mycotic aneurysm,

True aneurysm :

• The wall of true aneurysm consists of all layers of the vessel wall.
• Larger aneurysm is likely to rupture once the stress on the vessel wall exceeds its tensile strength.
• As the aorta dilates, the force on the aortic wall increases, which causes further aortic dilatation. Laplace law: wall tension x radius.

Pseudoaneurysm

• Consists partly of the vessel wall and partly of fibrous or other surrounding tissue.
• It can develop at the site of previous arterial cathetrisation or at anastomoses from prior vascular reconstruction, or due to trauma or infection.

Mycotic aneurysm

• It develops as a result of infection.
• Common in immunocompromised.

Popliteal artery aneurysm is the commonest peripheral aneurysm.

AORTIC ANEURYSM

Risk factors for aortic aneurysm

• Smoking

• High blood pressure
• Male
• Genetics Inherited conditions that adversely affects the supporting connective tissue.
• Aging: the aorta becomes less elastic and stiffer than age.
• Infections : can damage lining of the heart and aorta.
• Trauma: falls or motor vehicle collision can injure the aorta.

Aortic aneurysm can be either abdominal or thoracic aneurysm

Abdominal aneurysm

• Abdominal aortic aneurysm is defined as an aneurysm > 3.0cm in diameter and repair is considered for an aneurysm >5.0 cm in diameter.

Clinical Feature

• They present commonly with back pain or abdominal pain. It is often severe and abrupt in onset. It is usually described as a tearing pain.
• Syncope suggests rupture of aneurysm with cerebral hypoperfusion.
• GI bleeding from aortoduodenal fistula,
• Extermity ischemia from embolisation of a thrombus in the aneurysm.
• Pulsatile abdominal mass
• Tenderness on palpation may be a sign of aneurysmal expansion or rupture.
• Signs of aortic rupture include turners sign, cullens sign, scrotal or vulval hematoma or inguinal masses.

Differential Diagnosis

• Pancreatitis
• Hepatobiliary disorders
• Renal disorders
• Other differential diagnosis for syncope and chest pain.

Diagnosis

• Emergency bedside USG
  • >90% sensitivity
  • Aneurysm is measured from the outsside margin of one wall to outside margin of the opposite wall in both transverse and longitudinal planes.
• CT with IV contrast

Management

• Airway, Breathing
• Circulation
  • Secure two large bore IV cannulas
  • Cardiac monitoring

• Permissive Hypotension & bradycardia
  • Here the aim is to reduce the mean arterial pressure and aortic shear force.
  • Target mean arterial pressure is between 60 -70 mmHg
  • It is achieved by using sedatives, analgesics, vasodilators, beta blockers like esmolol.

• Definitive treatment
  • Open AAA repair using a prosthetic graft.
  • Endovascular stent graft
    

Update on 27/4/13

Reference

• Tintinalli
• Vascularsurgery.org