Nursing

RN/AHC Media Home Study Program CE CENTER

CE credit is no longer available for this article. (Expired March 2009)

Originally posted March 2007

By HEATHER DELLA CROCE, RN, BSN, CCRN

HEATHER DELLA CROCE is is a staff nurse in the trauma/surgical ICU at Robert Wood Johnson University Hospital in New Brunswick, NJ. The author has no financial relationships to disclose.

Your quick intervention can mean the difference between life and death for patients with this condition.

Escorted by his son, a patient I'll call Thomas Campbell, 64, arrives at the ED. Sweating and breathing rapidly, Mr. Campbell complains of excruciating pain between his shoulder blades that came "out of no where," receded, and then started again.

His skin feels clammy as you detect a heart rate of 110 beats per minute and take his BP, which is 190/100 mm Hg. Doppler ultrasound reveals diminished pedal pulses. He explains that he was recently diagnosed with a small aortic aneurysm and was started on BP medication. When his CT scan confirms your suspicion that the aneurysm is larger and dissecting, you titrate vasodilators to keep his systolic BP between 90 and 120 mm Hg, administer fluids cautiously to maintain blood volume, give narcotics for pain, and prepare Mr. Campbell for transfer to the ICU where he'll be stabilized before undergoing surgery.

A relatively common vascular disorder, aortic aneu rysms typically affect older male patients like Mr. Campbell. The condition occurs five times more often in men than in women, and the risk increases with age, usually affecting patients in their 60s and 70s.^1,2 Additional risk factors include hypertension, smoking, and other conditions that contribute to atherosclerosis, as well as Marfan's disease, family history of aortic aneurysm, infection, trauma, and pregnancy.³ Mr. Campbell's son confirms that his dad takes medication for high blood pressure, but continues to smoke at least half a pack of cigarettes a day.

Pressure on damaged wall expands a bulge

As damage to the elastic tissue of the middle layer of the aorta weakens the vessel wall, a dilatation or bulge extends the wall beyond its normal 2 – 3.5 cm diameter. An expansion can occur anywhere along the aorta, from the ascending arch down to the abdominal section, and can bulge on one side of the aortic wall or completely around the circumference. The high pressure of blood flow on the damaged wall extends the bulge, compress ing adjacent organs and causing symptoms.

If the expansion continues, the weakened inner lining of the aorta may tear or rip. This allows blood to be pumped between the arterial wall layers, creating dissection. Should the outer wall rupture under the pressure, it can result in severe blood loss, nerve damage, stroke, MI, or death within hours.⁴ For a full explanation of how an aneurysm dissects or ruptures, see the box on page 29.

Aortic aneurysms and dissections claim nearly 15,000 lives each year.⁵ As a result, you'll need to educate pa tients about managing an asymptomatic aneu rysm and recognizing the signs and symptoms of a worsening condition. Meanwhile, the survival and re covery of patients like Mr. Campbell depend on your astute de tection and assessment of life-threatening symptoms.

Monitor closely to prevent disaster

Most aortic aneurysms grow slowly, so symptoms rarely develop early on. In fact, aneurysms are usually discovered as an incidental finding through a routine physical exam or diagnostic testing such as chest X-ray, CT scan, or MRI.^3,6

If the asymptomatic bulge is 4 – 5.5 cm, patients are typically managed medically and reassessed every six to 12 months.^3,7,8 For these patients, review the importance of a low-sodium diet, a smoke-free lifestyle, complying with medication to lower cholesterol and BP, and other measures that help to contain the aneurysm.⁶ Although adequate blood pressure control may eliminate the need for surgery, lifelong monitoring is required because the aneurysm may enlarge and dissect or rupture at any time. Explain the importance of periodic chest X-rays, sonograms, CT scans, and other diagnostic tests described in the box on page 30 to monitor the aneurysm's growth. Urge patients to report abdominal tenderness or chest or back pain, which might indicate a dissection or rupture.^3,7

If an aneurysm is at least 5.5 cm or grows more than 0.5 cm in six months, patients need surgery to resect and graft the affected portion of the aorta.^7,8 That's because the larger the aneurysm, the greater the risk of rupture.¹ Patients with mild symptoms, which vary by the location of the dilatation, are also surgical candidates.

When present, symptoms differ according to the location of the aneurysm and which vessels or organs are being compressed.⁴ For example, bloating and tenderness of the abdomen, back pain, nausea, or vomiting may occur with abdominal aortic aneu rysms, which develop below the diaphragm, typically beneath the renal arteries. Sometimes, a pulsating mass is palpable and a bruit may be heard over the abdominal aorta. In addition, patients with this type of aneurysm often sense throbbing near the navel,⁷ which feels tender when palpated.

Abdominal aneurysms are four times more common than thoracic aneurysms, which occur in the ascending aorta, aortic arch, or descending aorta above the diaphragm. With a thoracic aneurysm, patients typically have pain between the shoulder blades that radiates from the chest. Respiratory symptoms may include cough, dyspnea, and wheezing as the enlarged aorta compresses the trachea or bronchi.⁴ Patients may experience dysphagia when the aorta impinges on the esophagus, or hoarseness from pressure on the left laryngeal nerve.¹

Aneurysms of the ascending aorta or aortic arch may result in superior vena cava syndrome, manifested by increased central venous pressure (CVP), different BP readings in each arm, or edema of the arms and face.¹ Aneurysms located in the ascending aorta may damage the aortic valve, causing pulmonary edema. Watch for shortness of breath, cough, and swelling of ankles, feet, and legs.

Move swiftly to save your patient's life

Despite your efforts and a patient's diligence, aortic aneurysms can dissect or rupture suddenly. Some patients don't realize they have an aneurysm until serious signs and symptoms develop that warrant emergency treatment. You'll need to know what to look for to quickly assess the patient's condition and prep him for treatment.

The most common symptom of a dissection, which usually occurs in the thoracic aorta, is severe pain of sudden onset, frequently described as "tearing" or "ripping." The pain usually starts in the chest, ab domen, or back, and as the dissection extends, or worsens, the pain may radiate to the back or lower extremities.⁹ Other signs and symptoms occur when blood flow through the aorta is interrupted. Depending on the location and size of the dissection, patients may develop decreased peripheral pulses, paraplegia, or stroke-like symptoms. Although surgical intervention is indicated for dissections of the ascending aorta and aortic arch,⁹ surgery is often delayed until the patient's condition stabilizes. Patients like Mr. Campbell are typically managed in the ICU. Because of a high mortality rate associated with surgery, dissections of the descending aorta may be managed medically if there are no complications. Medical management includes close monitoring for worsening symptoms, controlling blood pressure and pain with medication.¹⁰ Analgesics are administered with caution, however, so as not to mask symptoms of further dissection or rupture.

Should a dissection continue despite medication or quickly progress to rupture, emergency surgery is required to prevent death.⁹ The classic presentation of a ruptured aneurysm includes the triad of hypotension, sudden onset of pain, and a pulsating mass in the abdomen.² Other signs and symptoms include tachycardia due to hypovolemia and de creased perfusion distal to the site of rupture. Patients need rapid fluid resuscitation to maintain blood pressure until surgery.

Emergency repair is usually done as an open procedure, which involves an incision in the abdomen or chest that provides direct access to the aorta. It allows resection of the affected area, placement of a prosthetic graft to restore blood flow through the aorta, and, in some cases, replacement of the aortic valve. Some patients may be candidates for the less invasive endovascular repair, which involves sev eral small incisions in the femoral artery that allow a graft to be threaded to the site of the aneurysm. Catheters guide and deliver the graft—a cloth tube supported by metal wire stents—to contain the aneurysm.¹¹ Determining whether open surgery or endovascular repair is more appropriate is based upon many factors, including the size and location of the aneurysm and the risks for complications related to conventional surgery.

While patients treated with open surgery spend about a week in the hos pital, including sev eral days in the ICU, pa tients who undergo end ovas cular grafting usually recover on a med/surg unit, with a total hos pital stay of two or three days.^10.11 Despite these benefits, the long-term advantages of endovascular compared to open aneurysm repair have not yet been established.^2,8

Protect the graft, minimize complications

Once Mr. Campbell undergoes surgery, you'll carefully monitor his cardiovascular status, remain alert for signs of bleeding, and keep him comfortable.⁹ Because the aneu rysm may have damaged arteries that originate in the aorta, perfusion may be altered. For this reason, you'll need to monitor for signs and symptoms of MI, stroke, bowel necrosis, and limb ischemia.³ To ensure adequate perfusion, decrease pressure on the repaired aorta, and prevent graft rupture, systolic blood pressure is usually maintained between 110 and 130 mm Hg.^3,12

You'll have to control high BP by admin istering antihypertensive medications, such as beta blockers, and possibly vasodilators such as nitroprusside (Nipride) or a nitroglycerin drip. Monitor BP using an arterial line. To further reduce pressure on the graft, keep the head of the bed below 45 degrees for the first two days postop.³

On the other hand, blood loss and antihypertensive medication can quickly lead to hypotension. You may need to administer vasoconstricting agents such as norepinephrine (Levophed) to maintain adequate blood pressure. To prevent occlusion of the new graft, Mr. Campbell's mean arterial pressure (MAP) should be maintained at a minimum of 70 mm Hg.¹²

Also check serial complete blood counts (CBC) to detect internal blood loss. Assess leaking at the site of entry or surgical repair, checking and marking the boundaries of drainage on the dressing. If the amount seems excessive, you should notify the surgeon. Watch for increased abdominal size and disten sion, which indicate internal bleeding at the surgical site. And assess the puncture site of patients who undergo the endovascular procedure, per hospital protocol.

In Mr. Campbell's case, you'll need to assess his vital signs and peripheral pulses every one to two hours until stable. Weakened pulses may indicate decreased distal perfusion from aortic bleeding or an occluded graft. If you can't palpate the pedal pulses, use Doppler ultrasound to assess blood flow. Monitor renal function, including creatinine and blood urea nitrogen (BUN). And measure urine output hourly for as long as ordered; a drop in urine output may indicate a decrease in renal perfusion caused by bleeding or graft occlusion.

Keep in mind, too, that pa tients who undergo repair of a thoracic aneurysm may have a chest tube. Be sure to monitor the output and dressing for in creased drainage that could indicate bleeding.

Pain management, an important means of managing anxiety, ultimately helps to control blood pressure and avoid excess pressure on the graft. Adequate pain control also allows patients to cough and deep breathe, which helps prevent atelectasis and pneumonia. Instruct Mr. Campbell to hug a pillow when coughing, and encourage him to use an incentive spirometer.

Preparing the patient to go home

Once he is stable, focus on discharge planning, which is the same for patients who have undergone open or endovascular procedures. Include family members in the discussion as you explain that he probably should not drive for one to two weeks and must avoid lifting anything heavier than 10 pounds for approximately four to six weeks.¹¹ Advise Mr. Campbell to keep the incision dry until it heals and encourage him to take a sponge bath or shower carefully as directed.¹¹

In addition, be sure to emphasize the importance of keeping follow-up physician and diag nostic appoint ments. Because of the risk of complications, endovascular repair patients should undergo follow-up CT scans at one, six, and 12 months and then yearly to check graft fixation.^2,13 Patients like Mr. Campbell who undergo open repair don't need follow-up scans because there's little risk for graft migration or leakage.²

To help him with lifestyle changes, provide written information on smoking cessation, a low-sodium, low-cholesterol diet, and the role of exercise in maintaining a healthy weight. And don't forget to discuss the need for aneurysm screening of at-risk family members, including those who are elderly, smoke, or have high blood pressure.

Thanks to your nursing care, Mr. Campbell is well equipped for his new lifestyle. By knowing what to look for and when to intervene, you can help to ensure better outcomes for all patients with aortic aneurysms.

REFERENCES

1. Klein, D. G. (2005). Thoracic aortic aneurysms. J Cardiovasc Nurs, 20(4), 245.

2. Upchurch, G. R., & Schaub, T. A. (2006). Abdominal aortic aneurysm. Am Fam Physician, 73(7), 1199.

3. Chulay, M., & Burns, S. M. (2006). AACN essentials of critical care nursing. New York: McGraw-Hill Companies.

4. The Merck Manual. "Aneurysms." 2006. www.merck.com/mmhe/sec03/ch035/ch035b.html (27 Dec. 2006).

5. Hoyert, D. L., Heron, M. P., et al. (2006). Deaths: Final data for 2003. Natl Vital Stat Rep, 54(13), 41.

6. Almahameed, A., Latif, A. A., & Graham, L. M. (2005). Managing abdominal aortic aneurysms: Treat the aneurysm and the risk factors. Cleve Clin J Med, 72(10), 877.

7. Mayo Clinic staff. "Aortic aneurysm." 2006. www.mayoclinic.com/health/aortic-aneurysm/DS00017 (11 Dec. 2006).

8. Hirsch, A. T., Haskal, Z. J., et al. "ACC/AHA guidelines for management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic): A collaborative report from the American Association for Vascular Surgery/Society for Vascular Society, Society for Cardiovascular Angiography and Interventions, Society for Vascular Medicine and Biology, Society of Interventional Radiology, and the ACC/AHA Task Force on Practice Guidelines." 2005. www.americanheart.org/presenter.jhtml?identifier=3036691 (19 Dec. 2006).

9. Urden, L. D., Stacy, K. M., & Lough, M. E. (2002). Thelan's critical care nursing: Diagnosis and management (4th ed.). St. Louis: Mosby.

10. Cleveland Clinic Heart & Vascular Institute. "Surgery for thoracic aortic aneurysm." 2006. www.clevelandclinic.org/heartcenter/pub/guide/disease/aorta_marfan/surgerythoracicaneurysm.htm (14 Dec. 2006).

11. Cleveland Clinic Heart & Vascular Institute. "Endovascular repair of thoracic aortic aneurysms." 2006. www.clevelandclinic.org/heartcenter/pub/guide/disease/aorta_marfan/endovascularaorticaneurysm.htm (14 Dec. 2006).

12. Stillwell, S. B. (2002). Critical care nursing reference (3rd ed.). St. Louis: Mosby.

13. Society for Vascular Surgery. "Endovascular stent graft for abdominal and thoracic aortic aneurysms." 2003. www.vascularweb.org/_CONTRIBUTION_PAGES/Patient_Informa tion/NorthPoint/Endovascular_Stent_Graft.html (30 Dec. 2006).

Anatomy of an aneurysm

The largest artery in the body, the aorta is comprised of three layers. Blood flows through the tunica intima, which is the thin, delicate, inner layer. The tunica media, or middle muscle layer, is comprised of intertwined tissue that gives the aorta its strength and elas ticity. When this layer weakens, the outer layer, called the tu nica adventitia, bulges to form an aneurysm. The pressure and velocity of blood pulsing through the aorta further weak ens the vessel walls and the aneurysm becomes larger. In a cyclical pattern, the growing aneurysm puts additional pressure on vessel walls. Without medical or sur gical intervention, the aneu rysm may dissect or rupture.

Aortic dissection begins when a lengthwise tear in the inner layer allows blood to flow between all three layers of the aorta. If the dissection continues, it separates the inner from the outer layers along the aorta. With ongoing pressure, the outer wall of the aorta may split open or rupture.

Two classification systems are used to categorize dissections by location of the aortic tear. According to the Stanford system, type A dissections involve the aortic arch and type B dissections affect the descending aorta. In the DeBakey system, type I involves the ascending aorta and descending aorta, type II is limited to the ascending aorta, and type III involves only the descending aorta.

Aneurysms are usually described by shape. Most aneurysms are fusiform, meaning the entire circumference of the artery is dilated symmetrically. In contrast, a saccular aneurysm is a bulge on one side of the aortic wall that looks like a pouch.

Sources: 1. Chulay, M., & Burns, S. M. (2006). AACN essentials of critical care nursing. New York: McGraw-Hill Companies. 2. Klein, D. G. (2005). Thoracic aortic aneurysms. J Cardiovasc Nurs, 20(4), 245.

Useful imaging studies

Several tests can diagnose an aneurysm or detect changes over time. They include:

• CT scans. Thanks to recent advances in technology, CT scanning has become the primary tool in diagnosing aortic dissections in many hospitals. By providing a quick, clear assessment of the type and location of the aneurysm, CT scanning assists the surgeon in planning operative repair. Faster scanners have de creased motion artifact associated with breathing. Spiral CT scanning provides high-quality 2D and 3D reconstructions and has better resolution and a higher rate of detection than incremental CT scanning. The use of contrast material, which may harm a patient with renal disease or allergies to iodine, is among the procedure's drawbacks.
• MRI scans. This modality is the most sensitive for diagnosing aortic dissection, with specificity similar to that of CT scans. In addition to showing the type and extent of dissection, MRI also visualizes aortic insufficiency and surrounding mediastinal structures. The preferred method for evaluating chronic dissections and postoperative follow-up, MRI doesn't require contrast medium. The downside: MRI is more time consuming than CT scans.
• Angiography. Accurately diagnosing dissection in more than 95% of patients, this procedure allows accurate visualization that aids in planning corrective surgery. Yet drawbacks include its invasive nature and the potentially harmful use of contrast media in patients with impaired renal function or allergies to iodine.
• Echocardiography. Transthoracic echocardiography (TTE) is a useful, noninvasive diagnostic tool with lower sensitivity and specificity than angiography. Most helpful in detecting ascending aortic dissections, especially those close to the aortic valve, TTE is less useful in detecting arch and descending aortic dissections. Transesophageal echocardiography (TEE) has greater sensitivity and specificity than TTE. Also noninvasive, TEE may produce false-positive results from reverberations in the ascending aorta and false-negative results due to poor visualization of the upper ascending aorta and arch.
• Chest X-rays. These radiographs typically detect ascending aortic dissections. A widening mediastinum greater than 8 cm on AP chest radiograph suggests an acute thoracic dissection.

Source: Wiesenfarth, J. "Dissection, aortic." 2005. www.emedicine.com/emerg/topic28.htm (26 Jan. 2007).