abdominal aortic aneurysm

Abdominal aortic aneurysm

Description

Abdominal aneurysm, an abnormal di­lation in the arterial wall, generally occurs in the aorta between the renal arteries and iliac branches. More than 50% of all patients with untreated ab­dominal aneurysms die, primarily from aneurysmal rupture, within 2 years of diagnosis. More than 85% die within 5 years.

Causes

• Arteriosclerosis (by far the most common)

• Cystic medial necrosis

• Trauma

• Syphilis

• Other infections

Signs and symptoms

Nnnimminent rupture

.

—Asymptomatic pulsating mass in the periumbilical area

—Systolic bruit,over the aorta

—Possible tenderness on deep palpa­tion

Imminent rupture

Lumbar pain that radiates to the flank and groin from pressure on lumbar nerves

Rupture into peritoneal cavity

—Severe, persistent abdominal and .

back pain, mimicking renal or ureteral

colic

-Signs of hemorrhage. These signs, such as weakness, sweating, tachycardia, and hypotension, may be Subtle due to retroperitoneal bleeding.

Diagnostic tests

Several tests. can confirm suspected abdominal aneurysm.

• Serial ultrasonography allows deter­mination of aneurysm size/shape, and location.

• Anteroposterior and lateral X-rays of the abdomen can detect aortic cal­cification, which outlines the mass, in at least 75% of patients.

• Aortography shows the condition of vessels proximal arid distal to the aneurysm and the extent of the aneurysm but may underestimate aneurysm diameter, because it visualizes only the flow channel and not the surrounding clot.

Treatment

Usually, abdominal aneurysm requires resection of the aneurysm arid replacement of the damaged aortic section with a Dacron graft. If an aneurysm is small and asymptomatic, surgery may be delayed; however, small aneu­rysms may rupture. Regular physical examination and ultrasound checks are necessary to detect enlargement, which may forewarn rupture. Large aneurysms or those that, produce symptoms involve a significant risk of rupture and necessitate immediate re­pair. In patients with poor distal run­off, external grafting may be done.

Clinical Implications Abdominal aneurysm requires metic­ulous preoperative and postoperative care, psychological support, and comprehensive patient teaching/Following diagnosis, if rupture is not imminent, elective surgery allows time for additional preoperative tests to evaluate the patient's clinical status.

• Monitor vital signs, and type and cross match blood.

• As ordered, obtain kidney function tests (BUN, creatinine, electrolytes), blood samples (CBC with differen­tial), EKG and cardiac evaluation, baseline pulmonary function tests, and blood gases.

• Be alert for signs of rupture, which may be immediately fatal. .Watch closely for any signs of 'acute' blood loss (decreasing blood pressure, in­creasing pulse and respiratory rate; cool, clammy skin; restlessness; and decreased serisorium)

• If rupture occurs, the first priority is to get the patient to surgery .

im­mediately; Medical antishock trousers may be used during transport. Surgery allows direct compression of the aorta to control hemorrhage. Large amounts of blood may be needed during the resuscitative period to replace blood, loss. Renal failure due to ischemia is a major postoperative complication, possibly requiring hemodialysis.

• Before elective surgery, weigh the patient, insert an indwelling (Foley) catheter and I.V. line, and assist with insertion of an arterial line and pul­monary artery catheter to monitor fluid and hemodynamic balance. Give prophylactic antibiotics, as ordered.

• Explain the surgical procedure and the expected postoperative care in the ICU for patients undergoing complex abdominal surgery (l.V. lines, endo­tracheal and nasogastric intubation, mechanical ventilation).

• After surgery, in the ICU, closely monitor vital signs, intake and hourly output, neurologic.status (level of con­sciousness pupil size, sensation in arms and legs), and blood gases. As­sess lung Sounds and the depth, rate, and character of respirations at least every hour• Watch for signs of bleeding (increased .pulse rate and respirations, hypotension), which: may occur retroperitorieally from the graft site. Check abdominal dressings for exces­sive bleeding or drainage. Be alert for temperature elevations and other signs of infection. After nasogastric intu­bation for intestinal decompression, irrigate the tube frequently to ensure patency. Record the amount and type of drainage.

• Suction the endotracheal tube often. If the patient can breathe unassisted and has good lung sounds and ade­quate blood gases, 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.

• Help the patient walk as soon as he can (generally the 2nd day after sur­gery).

• Provide psychological support for the patient and family. Help ease their fears about the ICU.'the threat of impending rupture, and surgery by providing appropriate explanations and answering all questions.