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Abdominal aortic aneurysm

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(AAA) Abdominal aortic aneurysm (AAA) , an abnormal dilation in the arterial wall, generally occurs in the aorta between the renal arteries and iliac branches . Rupture , in which the aneurysm breaks open , resulting in profuse bleeding , is a common complication that occurs in larger aneurysm . Dissection occurs when the artery’s lining tears and blood leaks into the walls. AAA is four times more common in men than in women and is most prevalent in whites ages 40 to 70. Less than half of people with a ruptured AAA survive.

Pathophysiology

Aortic aneurysms develop slowly . First , a focal weakness in the muscular layer of the aorta (tunica media), caused by degenerative changes , allows the inner layer (tunica intima) and outer layer (tunica adventitia) to AAAstretch outward. Blood pressure within the aorta progressively weakens the vessel walls and enlarges the aneurysm.

Nearly all AAAs are fusiform , which causes the arterial walls to balloon on all sides . The resulting sac fills with necrotic debris and thrombi .

About 95% of abdominal aneurysms result from arteriosclerosis or atherosclerosis ; the rest , from cystic medial necrosis , trauma , hypertension , blunt abdominal injury, syphilis, and other infections.

arteries

Complications

  • Rupture
  • Obstruction of blood flow to other organs
  • Embolization to a peripheral artery
  • Diminished blood supply to vital organs resulting in organ failure (with rupture)

Assessment findings

  • Most patients with abdominal aneurysms are asymptomatic until the aneurysm enlarges and compresses surrounding tissue.
  • A large aneurysm may produce signs and symptoms that mimic renal calculi, lumbar disk disease, and duodenal compression.
  • The patient may complain of gnawing, generalized, steady abdominal pain or low back pain that’s unaffected by movement. He may have a sensation of gastric or abdominal fullness caused by pressure on the GI structures.
  • Sudden onset of severe abdominal pain or lumbar pain that radiates to the flank and groin from pressure on lumbar nerves may signify enlargement and imminent rupture. If the aneurysm ruptures into the peritoneal cavity, severe and persistent abdominal and back pain, mimicking renal or ureteral colic, occurs. If it ruptures into the duodenum, GI bleeding occurs with massive hematemesis and melena.

abdominal pain

  • The patient may have a syncopal episode when an aneurysm ruptures, causing hypovolemia and a subsequent drop in blood pressure. Once a clot forms and the bleeding stops, he may again be asymptomatic or have abdominal pain because of bleeding into the peritoneum.

  • Inspection of the patient with an intact abdominal aneurysm usually reveals no significant findings. However, if the patient isn’t obese, you may notice a pulsating mass in the periumbilical area. If the aneurysm has ruptured, you may notice signs of hypovolemic shock , such as skin mottling , decreased level of consciousness (LOC), diaphoresis , and oliguria.

  • The abdomen may appear distended , and an ecchymosis or hematoma may be present in the abdominal, flank, or groin area.

  • Paraplegia may occur if the aneurysm rupture reduces blood flow to the spine.

  • Palpation of the abdomen may disclose some tenderness over the affected area . A pulsatile mass may be felt ; however, avoid deep palpation to locate the mass because this may cause the aneurysm to rupture. Palpation of the peripheral pulses may reveal absent pulses distal to a ruptured aneurysm.

Diagnostic test results

Because an abdominal aneurysm seldom produces symptoms , it’s typically detected accidentally on an X-ray or during a routine physical examination . Several tests can confirm suspected abdominal aneurysm :

  • Abdominal ultrasonography or echocardiography can help determine the size , shape , and location of the aneurysm.
  • Anteroposterior and lateral X-rays of the abdomen can be used to detect aortic calcification, which outlines the mass, at least 75% of the time.
  • A computed tomography scan can be used to visualize the aneurysm’s effect on nearby organs, particularly the position of the renal arteries in relation to the aneurysm.
  • Aortography shows the condition of vessels proximal and distal to the aneurysm and the extent of the aneurysm, but the diameter of the aneurysm may be underestimated because aortography shows only the flow channel and not the surrounding clot
  • Magnetic resonance imagining can be used as an alternative to aortography.
Aortic Aneurysm 1 Aortic Aneurysm

Treatment Usually, abdominal aneurysm requires resection of the aneurysm and Dacron graft replacement of the aortic section. If the aneurysm is small and produces no symptoms, surgery may be delayed; however, small aneurysms can rupture. A beta-adrenergic receptor blocker may be given to decrease the rate of growth of the aneurysm. Regular physical examination and ultrasound checks help monitor progression of the aneurysm. Large aneurysms or those that produce symptoms risk rupture and require immediate repair. In asymptomatic patients, surgery is advised when the aneurysm is 5 to 6 cm in diameter. In symptomatic patients, repair is indicated regardless of size. In patients with poor perfusion distal to the aneurysm, external grafting may be done.

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REPAIRING ABDOMINAL AORTIC ANEURYSMS WITH ENDOVASCULAR GRAFTING

pic1Endovascular grafting is a minimally invasive procedure used to repair abdominal aortic aneurysms . Such grafting reinforces the walls of the aorta to prevent rupture and prevents expansion of the aneurysm.

  • The procedure is performed with fluoroscopic guidance, with a delivery catheter with an attached compressed graft inserted through a small incision into the femoral or iliac artery over a guide wire.
  • The delivery catheter is advanced into the aorta, where it’s positioned across the aneurysm.
  • A balloon on the catheter expands the graft and affixes it to the vessel wall.
  • The procedure generally takes 2 to 3 hours to perform .
  • Patients are instructed to walk the first day after surgery and are discharged from the facility in 1 to 3 days.

For patients with acute dissection , emergency treatment before surgery includes:

  • resuscitation with fluid and blood replacement
  • I.V. propranolol (Inderal) to reduce myocardial contractility
  • I.V. nitroprusside (Nitropress) to reduce and maintain blood pressure to 100 to 120 mm Hg systolic
  • an analgesic to relieve pain
  • An arterial line and indwelling urinary catheter are inserted to monitor the patient’s condition.

Nursing interventions

  • NONACUTE SITUATION
  • ACUTE SITUATION
  • AFTER SURGERY

IN A NONACUTE SITUATION

      • Allow the patient to express his fears and concerns.
      • Help him identify effective coping strategies as he attempts to deal with his diagnosis.
      • Before elective surgery, weigh the patient, insert an indwelling urinary catheter and an I.V. line
      • assist with insertion of the arterial line and pulmonary artery catheter to monitor hemodynamic balance.
      • Give a prophylactic antibiotic as ordered.

IN AN ACUTE SITUATION

      • Monitor the patient’s vital signs on his admission to the intensive care unit (ICU).
      • Insert an I.V. line with at least a 18G needle to facilitate blood replacement.
      • Obtain blood samples for kidney function tests (such as blood urea nitrogen, creatinine, and electrolyte levels), a complete blood count with differential , blood typing and crossmatching , and arterial blood gas (ABG) levels.
      • Monitor the patient’s cardiac rhythm strip.
      • Insert an arterial line to allow for continuous blood pressure monitoring.
      • Assist with insertion of a pulmonary artery line to monitor for hemodynamic balance.
      • Give drugs , such as an antihypertensive and a beta-adrenergic receptor blocker to control aneurysm progression and an analgesic to relieve pain.
      • Look for signs of rupture , which may be immediately fatal.
      • Watch closely for signs of acute blood loss (such as decreasing blood pressure, increasing pulse and respiratory rates, restlessness, decreased sensorium, and cool, clammy skin).
      • If rupture occurs , get the patient to surgery immediately.
      • Medical antishock trousers may be used while transporting him to surgery.

AFTER SURGERY

      • Assess fluid status , and replace fluids as needed to ensure adequate hydration.
      • Watch for signs of bleeding (such as increased pulse and respiratory rates , and hypotension) , which may occur retroperitoneally from the graft site.
      • Check abdominal dressings for excessive bleeding or drainage.
      • Assess the wound site for evidence of infection.
      • Be alert for temperature elevations and other signs of infection.
      • Use sterile technique to change dressings.

DISCHARGE TEACHING

TEACHING THE PATIENT WITH AN ABDOMINAL AORTIC ANEURYSM

  • Review incisional care.
  • Instruct the patient to look at his incision daily and report any signs or symptoms of infection to the surgeon.
  • Make sure the patient knows when to see the surgeon for follow-up care.
  • Instruct the patient to take all drugs as prescribed and to carry a list of drugs at all times, in case of an emergency.
  • Tell the patient not to push, pull, or lift heavy objects until the practitioner indicates that it’s okay to do so.
  • After nasogastric intubation for intestinal decompression, irrigate the tube frequently to ensure patency. Record the amount and type of drainage.
  • Large amounts of blood may be needed during the resuscitative period to replace blood loss.
  • Thus, renal failure due to ischemia is a major postoperative complication, possibly requiring hemodialysis.
  • Assess for return of severe back pain , which can indicate that the graft is tearing.
  • Mechanical ventilation is required after surgery.
  • Assess the depth , rate , and character of respirations and breath sounds at least every hour.
  • Have the patient cough, or suction the endotracheal tube, as needed, to maintain a clear airway.
  • If the patient can breathe unassisted and has good breath sounds and adequate ABG levels, tidal volume, and vital capacity 24 hours after surgery, he will be extubated and will require oxygen by mask.
  • Weigh the patient daily to evaluate fluid balance.
  • Provide frequent turning, and help the patient walk as soon as he’s able (generally the second day after surgery).
منبع :

RN Expert Guides: Cardiovascular Care, 1st Edition

Copyright ©۲۰۰۸ Lippincott Williams & Wilkins

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Cardiovascular Care

 

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