Learning Outcome

• Recognize a patient presenting with sign and symptoms of an abdominal aortic aneurysm
• Outline nursing monitoring requirements for a patient with an abdominal aortic aneurysm
• State the desired blood pressure that should be targeted in a patient with an abdominal aortic aneurysm

Introduction

Abdominal aortic aneurysm (AAA), abnormal focal dilation of the abdominal aorta, is a life-threatening condition that requires monitoring or treatment depending upon the size of the aneurysm and/or symptomatology. AAA may be detected incidentally or at the time of rupture. An arterial aneurysm is defined as a permanent localized dilatation of the vessel at least 150% compared to a relative normal adjacent diameter of that artery.[1]

Nursing Diagnosis

• Abdominal aortic aneurysm
• Anxiety from pain
• The decreased cardiac output from rupture
• Shock if a rupture has occurred

Causes

Risk factors for AAA include atherosclerosis (most common), smoking, advanced age, male gender, Caucasian race, family history of AAA, hypertension, hypercholesterolemia, and prior history of aortic dissection. Other causes include cystic medial necrosis, syphilis, HIV, and connective tissue diseases (Ehlers-Danlos, Marfan, Loeys-Dietz syndromes). Non-Caucasian race and diabetes are associated with a reduced risk for AAA.

Aneurysm enlargement can be step-wise with the stability of the size for some time and then a more rapid enlargement. The rate of enlargement for small AAA (3-5 cm) is 0.2 to 0.3 cm/year and 0.3 to 0.5 cm/year for those > 5 cm.[2] The pressure on the aortic wall follows the Law of Laplace (wall stress is proportional to the radius of the aneurysm).  Because of this, larger aneurysms are at higher risk of rupture, and the presence of hypertension also increases this risk.

Risk Factors

Based on autopsy studies, the frequency of these aneurysms varies from 0.5% to 3%. The incidence of abdominal aortic aneurysms increases after age 60 and peaks in the seventh and eighth decades of life. White men have the highest risk of developing abdominal aortic aneurysms. They are uncommon in Asian, African American, and Hispanic individuals [3]. Data derived from Lifeline AAA screening and National Health and Nutrition Examination Survey (NHANES, 2003-2006)database reveals a prevalence of 1.4% or 1.1 million AAAs in those studied aged 50 to 84.[4] With the increased use of ultrasound, the diagnosis of abdominal aortic aneurysms is quite common. They tend to be more common in smokers and elderly white males. Although autopsy studies may under-represent AAA incidence, one study from Malmo Sweden found a prevalence of 4.3% in men and 2.1% in women detected on ultrasound.[5]

Assessment

The majority of abdominal aortic aneurysms are identified incidentally during an examination for another unrelated pathology. Most individuals are asymptomatic. Palpation of the abdomen usually reveals a non-tender, pulsatile abdominal mass. Enlarging aneurysms can cause symptoms of abdominal, flank, or back pain.  Compression of adjacent viscera can cause gastrointestinal (GI) or renal manifestations.

Rupture of an abdominal aortic aneurysm is life-threatening. These patients may present in shock often with diffuse abdominal pain and distension. However, the presentation of patients with this type of ruptured aneurysm can vary from subtle to quite dramatic. Most patients with a ruptured abdominal aortic aneurysm die before hospital arrival. On physical exam, the patient may have tenderness over the aneurysm or demonstrate signs of embolization. The aneurysm may rupture into adjacent viscera or vessels presenting with GI bleeding or congestive heart failure due to the aortocaval fistula. Physical exam should also look for other associated aneurysms. The most common associated aneurysm is an iliac artery aneurysm. Peripheral aneurysms are also associated in approximately 5 % of patients, of which popliteal artery aneurysms are the most common.

Evaluation

Most AAA are asymptomatic, but some patients may present with flank or abdominal pain, indigestion, or a bloating sensation-hence. One should be suspicious of this pathology.

The diagnosis of an abdominal aortic aneurysm is usually made with ultrasound (US), but a CT scan is needed to determine the exact location, size, and involvement of other vessels. The US can be used for screening purposes but is less accurate for aneurysms above the renal arteries because of the overlying air-containing lung and viscera. CTA requires the use of ionizing radiation and intravenous contrast. Magnetic resonance angiography can be used as well to delineate the anatomy and does not require ionizing radiation.

Most of these aneurysms are located below the origin of the renal arteries. They may be classified as saccular (localized) or fusiform (circumferential). Some people may develop an inflammatory abdominal aortic aneurysm, which is characterized by intense inflammation, a thickened peel, and adhesions to adjacent structures. Angiography is now rarely done to make the diagnosis because of the superior images obtained with CT scans.[6]

Medical Management

The treatment of unruptured abdominal aortic aneurysm has changed over time. Treatment is recommended when it reaches 5 cm to 5.5 cm, is demonstrated as rapidly enlarging > 0.5 cm over 6 months, or becomes symptomatic. Open surgical repair via transabdominal or retroperitoneal approach has been the gold standard. Endovascular repair from a femoral arterial approach is now applied for most repairs, especially in older and higher-risk patients.  Endovascular therapy is recommended in patients who are not candidates for open surgery. This includes patients with severe heart disease and/or other comorbidities that preclude open repair. A ruptured abdominal aortic aneurysm warrants emergency repair.  The endovascular approach for ruptured AAA has demonstrated superior results and survival compared to open repair if the anatomy is suitable, but the mortality rates remain high. The risk of surgery is influenced by the age of the patient, the presence of renal failure, and the status of the cardiopulmonary system.[7][8]

Data show that for unruptured abdominal aortic aneurysms, endovascular repair has no long-term differences in outcomes compared to open repair. All patients with small abdominal aortic aneurysms who do not undergo repair need periodic follow up with an ultrasound every 6 to 12 months to ensure that the aneurysm is not expanding.[9]

Nursing Management

The ultimate goal of treatment is to limit the progression of the AAA by modifying risk factors like controlling blood pressure, discontinuing smoking, and lowering levels of lipids. When the patient is admitted, the following assessments are necessary:

1. Check by palpation for a pulsating mass in the abdomen, at or above the umbilicus.
2. Auscultate for a bruit over the abdominal aorta.
3. Determine if there is tenderness on palpation (do not palpate too deep as there is a risk of rupture).
4. Ask if the patient has abdominal or lower back pain.
5. Check blood pressure to determine if a rupture has occurred.
6. Check distal leg pulses to ensure tissue perfusion.
7. Strict blood pressure control if high (may need oral or IV medications).
8. Ensure that the patient has been seen by anesthesia and the vascular surgeon.

When To Seek Help

1. If the patient has low blood pressure
2. There is the loss of distal leg pulses
3. Abdominal tenderness
4. Mottling and ecchymosis around the abdomen
5. Shortness of breath
6. Sudden abdominal of back pain
7. Signs of ischemia, like stroke or myocardial infarction

Outcome Identification

The patient's blood pressure should be within 120/90. By controlling blood pressure and reducing modifiable risk factors as mentioned above, one can lower the risk of progression and rupture.

Monitoring

1. Check blood pressure at every clinic visit after discharge
2. Ensure wound is clean, dry, and healed
3. Ensure patient has distal leg pulses
4. Continue to recommend avoidance of tobacco

Coordination of Care

Infrarenal abdominal aortic aneurysms are the most common aneurysm of the aorta. Screening ultrasound has helped detect AAA and surveillance in asymptomatic patients with a diameter < 5 cm.  In females, the repair should be considered at 5 cm and in males at 5.5 cm.  If the rapid enlargement is demonstrated (>5 mm over 6 months), repair should be considered. Education of first responders, primary care physicians, and emergency department physicians can facilitate diagnosis and reduce delays in treatment. A team approach of emergency nurses, emergency physicians, and a vascular surgeon will facilitate rapid evaluation and treatment and improve outcomes. Referral to a vascular center that can provide a standard of care management is appropriate. Once the decision for repair has been made, cardiology workup and clearance and optimization of other medical co-morbidities can improve outcomes. If the aneurysm is small, the patient and family should be educated regarding compliance with blood pressure control, a healthy diet, exercise, cessation of smoking, and follow up.

Health Teaching and Health Promotion

• Discontinue smoking
• Control blood pressure (120/90)
• Medication compliance
• Regular physical activity
• Follow up with primary care provider

Risk Management

Nurses should always consult with a clinician immediately if a patient has hypotension, sudden low back, or abdominal pain. These may be signs of AAA rupture, which is a surgical emergency.

Discharge Planning

Patients should be advised about the following:

• Appropriate wound care.
• Discontinue smoking.
• Take blood pressure medications as prescribed.
• Maintain blood pressure to 120/90.
• Seek immediate medical assistance if there is sudden abdominal or back pain.

Evidence-Based Issues

Surgery has been shown to lower the risk of rupture.

It is recommended that patients with an AAA with a diameter of 5 cm should undergo surgery.

Pearls and Other issues

Factors that increase the operative risk for abdominal aortic aneurysm repair include:

• Severe heart disease
• Severe chronic obstructive pulmonary disease
• Poor renal function
• Comorbidities such as stroke, diabetes, hypertension, and advanced age can increase open surgical risk. These individuals should be considered for endovascular stenting of the aneurysm if the aortic anatomy permits