36: Aorto-Occlusive Disease

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CHAPTER 36 Aorto-Occlusive Disease

Luke Osborne, MD

1 Define aortic vascular disease

Aorto-occlusive disease is characterized by atherosclerotic changes within the aorta (usually abdominal) that extend into the iliac and femoral arteries and result in hypoperfusion of vital organs and the lower extremities. Involvement at iliac bifurcation and renal arteries is common; aneurismal changes may be found as well. Seventy percent of aortic aneurysms are infrarenal, and 30% include the renal arteries.

2 What risk factors and coexisting diseases are common in these patients?

Risk factors include smoking, family history, obesity, atherosclerotic disease elsewhere, advanced age and male sex. Common diseases include hypertension, ischemic heart disease, heart failure (HF), chronic obstructive pulmonary disease (COPD), diabetes mellitus, chronic renal disease, and carotid artery disease.

3 What is the natural progression of aortic vascular disease?

The natural history of aneurismal disease is one of continuing enlargement. Operative or endovascular repair should be undertaken when the aneurysm is 6 cm or larger. The incidence of rupture increases with size (9.4% chance of rupture within 1 year for aneurysms 5.5 to 5.9 cm, increasing to 32.5% for aneurysms 7 cm and larger).

National mortality from elective open abdominal aneurysm repair is <5%. For repair of an acutely ruptured aneurysm, perioperative mortality remains high, about 50%. Mortality with open thoracic aneurysm repair ranges from 5% to 14%. Endovascular repair has decreased mortality. The survival rate is 92% at 1 year and 67% at 5 years.

Aorto-occlusive disease results in hypoperfusion distal to the occlusion. Unlike surgery for aneurismal disease, surgery for occlusive disease should be undertaken when the patient becomes symptomatic and fails medical therapy.

4 Describe preoperative preparation of such patients in the presence of concurrent disease

The goal of preoperative evaluation is to optimize any significant organ dysfunction.

image Coronary artery disease: This is the major cause of perioperative mortality and morbidity. Myocardial infarction occurs in 4% to 15% of patients, and HF is noted in 30% of postoperative aneurysm repairs. If the patient has an acute coronary syndrome, decompensated heart failure, severe valvular disease, or significant arrhythmias, he or she should undergo preoperative cardiac testing, including echocardiography, stress testing, and coronary angiography. Similarly coronary artery evaluation may be strongly indicated in the presence of renal insufficiency, history of HF or cerebrovascular disease, or if the patient has diabetes mellitus or cannot achieve a metabolic equivalent (MET) level of four.
image Pulmonary: It has been mentioned that COPD is common. Physical examination, pulmonary function testing, arterial blood gas analysis, and chest radiography may suggest the need for preoperative incentive spirometry and bronchodilator and antibiotic therapy.
image Renal: The incidence of postoperative renal dysfunction in elective infrarenal aorta repair is 3% and up to 30% in thoracic aorta repair. The primary cause of postoperative renal failure is preexisting kidney disease. The degree of renal dysfunction should be characterized, and the patient adequately hydrated. Poorly controlled hypertension should be optimized. If the patient requires a contrast study before surgery, he or she should be well hydrated before dye administration and exposed to a minimum amount of contrast; repeated studies should be avoided.
image Cerebrovascular disease: Signs and symptoms of cerebrovascular insufficiency should be elucidated. Cerebral hypoperfusion during surgery could result in stroke. If carotid stenosis is found, endarterectomy may need to precede aortic repair. Chronically hypertensive patients also have shifts in cerebral autoregulation, and this is a second justification for preoperative management of hypertension.
image Diabetes mellitus: This should be well controlled.

5 List the appropriate intraoperative monitors for aortic surgery

image Standard monitors include pulse oximetry and noninvasive blood pressure and temperature monitoring. Continuous cardiac rhythm monitoring for rhythm (lead II) and ischemia (lead V5) is essential.
image Also essential are the usual anesthesia machine monitors, including capnography and delivered oxygen concentration.
image Intra-arterial monitoring rapidly detects swings in blood pressure and facilitates laboratory analysis.
image Monitoring of urine output with a Foley catheter and urimeter is essential.
image Use of central venous pressures, pulmonary artery catheters, and/or transesophageal echocardiography is appropriate when myocardial dysfunction and valvular disease are present.
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