CHAPTER 29

..... Physical Examination

Patients with ruptured AAA may present with evidence of

hemorrhagic shock: hypotension, tachycardia, and exam

findings of poor perfusion. However, the patient may be

normotensive or even hypertensive. Transient hypotension

may also occur and can be erroneously attributed to a vasovagal etiology. Abdominal examination may detect a pulsatile mass, but this can be difficult with small aneurysms or

obese patients and is subject to significant interobserver

variability. Absence of a pulsatile mass on exam does not

exclude the diagnosis of AAA. Lower extremity pulses should

be assessed, as lower limb ischemia is present in 5% of cases.

DIAGNOSTIC STUDIES

..... Laboratory

Any patient with a possible ruptured AAA should have

blood sent for type and crossmatch, although often

uncrossmatched blood will be required emergently.

Anemia can be seen in ruptured AAA, with hematocrit less

than 38 in 40% of patients. D-dimer assays have been

investigated as a possible screen for patients deemed to be

at low risk for AAA, but their use for this indication has not

yet been validated.

.... Imaging

Ultrasound has a sensitivity approaching 100% and can be

obtained at the bedside even in unstable patients. In addition to the aneurysm, ultrasound may reveal intraperito ­

neal free fluid in cases of rupture. However, because many

AAAs rupture into the retroperitoneum, ultrasound is

insensitive in detecting this complication, and a lack of free

fluid should not be reassuring. Ultrasound can also be

limited by obesity and by overlying bowel gas.

A

.&.Figure 29-1 . CT sca n showing a ruptured AAA. This

AAA is rupturing into the peritoneal cavity (a rrow). The

majority of ruptured AAAs are retroperitoneal (70%).

Abdominal computed tomography (CT) is helpful for

preoperative planning, is better at detecting suprarenal

aneurysms, and shows retroperitoneal bleeding not visible

on ultrasound. CT can also reveal alternative etiologies for

abdominal pain and can be considered a first-line diagnostic modality in stable patients (Figure 29-1) .

PROCEDURES

Bedside ultrasound allows for rapid detection of an aortic

aneurysm. Place the abdominal probe in the epigastric area in

the transverse plane (Figure 29-2). The aorta is located anterior and just to the left of the vertebral bodies. Move the probe

inferiorly until the aorta bifurcates at the umbilicus. Next,

rotate the probe 90 degrees to obtain a longitudinal view.

8

Figure 29-2. U ltrasound of an AAA. A. Transverse position of probe. 8. Transverse view of AAA.

ABDOMINAL AORTIC ANEURYSM

Elderly patient with:

Abdomina l/back/flank/ groin pain

± hypotension/syncope/pulsati le

abdominal mass

Suspect ruptured AAA

.A. Figure 29-3. AAA diagnostic algorithm.

MEDICAL DECISION MAKING

AAA must be ruled out in any elderly patient who presents

with abdominal, back, flank, or groin pain. Hemodynamically stable patients can be evaluated with CT, whereas

unstable patients are better assessed with a bedside ultrasound (Figure 29-3). Other emergent causes of abdominal,

back, and flank pain should be considered and evaluated

concurrently. Consider ruptured AAA in elderly patients

"found down" or with otherwise unexplained hypotension.

Any patient with abdominal pain and previous repair of

AAA, either open or endovascular, merits consultation

with the patient's surgeon.

TREATMENT

Patients with ruptured AAA require immediate treatment

in the ED with 2 large-bore ( 16-gauge) IV lines in the antecubital veins or a large-bore (SF) central line and subse ­

quent resuscitation with IV crystalloid and uncrossmatched

blood. The ideal goal blood pressure is not known, and

many practitioners will allow relative hypotension pending

definitive operative repair. A vascular surgeon should be

consulted immediately, and the patient should be taken to

the operating room or angiography suite as soon as possible to repair the AAA.

Unruptured, symptomatic AAAs require evaluation by

a vascular surgeon. These patients may benefit from early

elective repair, depending on the size of the aneurysm.

Patients with incidentally discovered asymptomatic aneu ­