Buckley, Barbra A. RN
Open abdominal aortic aneurysm (AAA) repair has been performed successfully for decades. A newer, minimally invasive alternative to traditional open surgery, endovascular aneurysm repair (EVAR), is now being performed regularly for elective AAA repair. This article describes how EVAR can treat a potentially life-threatening AAA and what nurses can do to ensure a successful outcome.
An aneurysm is defined as a pathologic focal (localized) dilatation of a segment of a blood vessel. Aortic aneurysms are defined as a 50% increase in the diameter of a segment of the aorta compared to normal sections.1
Aneurysms can be described as true or false. True aneurysms involve all three layers of the vessel wall—the tunica intima (inner layer), the tunica media (middle layer), and the tunica externa or tunica adventitia (outer layer), which remain intact in an uncomplicated aneurysm.2 (See An inside look at vessel walls for more detail.) A true aneurysm is bounded by a complete vessel wall and the blood remains within the vascular compartment.3
A false aneurysm or pseudoaneurysm, unlike a true aneurysm, involves a disruption (dissection or tear) in the intima, or the intima and media layers, with extravascular hematoma formation that causes vessel enlargement. False aneurysms are bounded only by the outer layers of the vessel wall or supporting tissues.3
Aortic aneurysms may also be classified according to their appearance. A fusiform aneurysm involves the entire circumference of the vessel segment, giving it a fairly symmetrical appearance. Fusiform aneurysms are characterized by a gradual and progressive dilation of the vessel.3 A saccular aneurysm involves only a portion of the circumference, resulting in an outpouching of the vessel wall and a “saclike” appearance.3 (See Tracing aortic anatomy.)
Aortic aneurysms also are classified according to their location. About 25% of aortic aneurysms are thoracic; the remainder are abdominal.4 Ninety percent of AAAs are infrarenal (below the renal arteries). Fifty percent of AAAs involve one or both iliac arteries.4
Whether aneurysms are abdominal or thoracic, the risk of rupture increases with size.5 (See Increasing size raises the risk.) AAA rupture is a surgical emergency. Without immediate surgery, the mortality for patients with a ruptured aneurysm is nearly 100%. Each year, about 15,000 Americans die of ruptured AAAs. Many of those who survive after surgery face major complications, including stroke, acute myocardial infarction, acute kidney injury, paralysis, and peripheral embolization.6
Risk factors and causes
AAAs generally occur in White men age 55 and older.1 The most common causes include atherosclerosis, smoking, hypertension, diabetes, and advanced age. Less common causes include trauma, familial tendency, valvular disease, infection, arteritis, and genetic diseases such as Marfan syndrome or Ehlers-Danlos syndrome.1
Most patients with AAAs are asymptomatic. As the AAA expands, some patients may feel strong pulsations in their abdomen or pain in their chest, lower back, or scrotum.7
Small AAAs, defined as smaller than 5.5 cm (2.17 in.) in diameter, are often found incidentally on computed tomography (CT) scans, magnetic resonance imaging, X-ray, or ultrasound.2 They may require only surveillance because the risk of rupture is small.8 Large AAAs may be detected during physical assessment as a palpable, pulsatile, nontender abdominal mass.
Given the gravity of AAA rupture, elective repair is recommended for at-risk aneurysms. AAAs larger than 5.5 cm and AAAs of any size that are symptomatic or rapidly expanding require intervention, which includes open repair or EVAR.9
EVAR involves endovascular stent placement to prevent the aneurysm from rupturing. If you think of stents as forcing the vessel wall to expand to the widest extent possible, the use of a stent to treat an aneurysm with its dilated, thinned walls seems counterintuitive. However, unlike metal mesh endovascular stents used in percutaneous coronary intervention, EVAR uses a fabric-covered stent (endograft) that doesn't apply pressure to the walls of the aneurysm.
For patients with significant comorbidities, EVAR may be recommended by their healthcare provider. Other patients will be attracted to EVAR because it's minimally invasive and associated with shorter hospitalization and faster recovery time.
Contraindications for EVAR include a short proximal neck (the section of the aorta above the aneurysm); thrombus in the proximal landing zone (the portion of the proximal neck where the upper edge of the endograft will be placed); a conical proximal neck; angulation of the proximal neck of more than 120 degrees; an inferior mesenteric artery that lacks good circulation; significant iliac occlusive disease; and tortuous iliac vessels. Patients who aren't candidates for EVAR include those with a prior anaphylactic-type reaction to intravascular contrast media.10
EVAR in action
Review the patient's health history, including allergies. Evaluate renal function because of the potential for contrast-induced nephrotoxicity. Perform medication reconciliation. Patients prescribed anticoagulant therapy will need careful teaching regarding dose modifications. Some patients (such as those with atrial fibrillation or mechanical heart valves) may require outpatient low molecular weight heparin administration.
Advise patients to avoid using nonsteroidal anti-inflammatory drugs, such as aspirin and ibuprofen. Warn them about herbal supplements that may have anticoagulant effects, such as ginkgo.
Figure. An inside lo...Image Tools
EVAR may be performed under general, regional, or local anesthesia and generally requires bilateral femoral artery cutdowns.9 It's usually done by an endovascular surgeon in the OR. Following intravascular ultrasound, an arteriogram of the abdominal aorta and iliac arteries is performed, followed by angiographic evaluation of the AAA. Under fluoroscopic guidance, the proximal edge of the endograft is placed in a healthy portion of the aorta, and the distal edge is placed below the aneurysm in a healthy portion of the vessel.8 This careful placement is needed to seal off the aneurysm and eliminate pressure on the weakened portion of the aorta.
After the endografts are sized and deployed and proper placement verified, procedural catheters and guidewires are removed, the arterial access is closed and arteries are sealed. Bilateral femoral artery cutdowns are repaired or percutaneous arterial punctures are closed, and distal pulses are verified. The stent graft creates a new, smaller channel within the aneurysm. This channel restores linear aortic blood flow and eliminates the swirling cyclonic flow against the aneurysm's weakened walls. The blood, thrombi, and plaque trapped within the aneurysm are no longer part of the vascular flow, so they gradually shrink.11
Possible complications of EVAR include atelectasis, acute kidney injury, aortic or iliac dissection, thromboembolization, endograft malposition, mesenteric ischemia, and development of an endoleak (the presence of persistent blood flow into the aneurysm sac after endograft placement).12
Figure. Tracing aort...Image Tools
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Immediate postoperative care is provided in the postanesthesia care unit. Monitor the femoral artery access sites for bleeding and expanding hematoma and the lower extremities for alterations in neurovascular status, including pulses, color, temperature, and motor and sensory function for 24 hours. Hospitalization usually lasts 24 to 48 hours. This is a significant improvement over traditional open surgical repair, which often requires hospital stays of 4 to 7 days.2
Before discharge, instruct patients to monitor for and promptly report any signs and symptoms of infection at the femoral access sites, as well as changes in color, temperature, sensation, or motion of the lower extremities. Full activity generally can be resumed as tolerated after discharge, normally 2 to 3 days postprocedure.
Following a successful EVAR, patients will require follow-up for the rest of their lives, including periodic CT scans to detect endoleaks. Current protocols recommend CT scans at 3 months, 6 months, 12 months, and then yearly.3
Patients with AAAs require information and emotional support. By increasing your understanding of EVAR, you can better educate and support patients who are offered this minimally invasive alternative.
© 2013 Lippincott Williams & Wilkins, Inc.