Aortic aneurysms is described as a permanent localized (i.e., focal) dilatation of the aorta having at least a 50% increase in diameter compared to the expected diameter of the artery. The clinical presentation of aneurysms relates to location, size, type, and comorbid factors affecting the patient. The majority of aneurysms are asymptomatic. Some present with rupture, others with embolism or thrombosis.

The natural history of abdominal aortic aneurysms depends on their size and the speed of expansion. Rupture of aneurysms is uncommon when they are less than 5.5 cm wide and are expanding slowly. Rupture is far more common in aneurysms that are over 5.5 cm wide and are expanding rapidly (>0.5 cm/year). Repair is therefore usually recommended for aneurysms over 5.5 cm wide.

Rupture is a feared problem. Rupture of an aneurysm is a catastrophe. It is highly lethal and is usually preceded by excruciating pain in the abdomen and back, with tenderness of the aneurysm. Rupture of an abdominal aneurysm causes profuse bleeding and leads to shock. Death may rapidly follow. Half of all persons with untreated abdominal aortic aneurysms die of rupture within 5 years. Aortic aneurysms cause more than 15,000 deaths per year in the U.S.A. It is the 10th leading cause of death in males over 55 and 13th leading cause of death overall in the U.S.

The Choice of Repair

There are approximately 40,000 patients undergoing elective repair of abdominal aortic aneurysm in the United States each year. Traditionally, repair of aortic aneurysms has been surgical. The surgery has usually consisted of opening the abdomen, removing (excising) the aneurysm, and sewing a synthetic (Dacron) tube in its place. Elective repair of abdominal aortic aneurysm has matured over the 45-year interval since the first direct surgical repair of abdominal aortic aneurysm was performed. While centers of excellence, such as Barnes-Jewish Hospital Washington University in St. Louis, consistently report mortality rates of less than 3.0% for aneurysm repair, multi-institutional community-based studies suggest that the mortality rate for elective aneurysm repair ranges from 6.0% to 10.0% each year. "Minimally invasive" procedures have been devised using stent grafts-endovascular repair of aortic aneurysms (EVAR) that can be guided to the site of the aneurysm without the need to cut open the abdomen. The first stent graft was installed in 1991 by Dr. Juan Parodi in Argentina (Dr. Parodi is currently a surgical faculty member at Barnes-Jewish Hospital, Washington University in St. Louis). To install the stent, a small incision is made in the thigh to gain access to the femoral artery. The stent, about 6 inches (15 cm) long, is guided inside a long plastic capsule through the arteries to the lower aorta. Once the stent is in place, the holding capsule is removed. Activated by heat, the stent expands like a spring and becomes anchored to the artery wall. The by-passed aneurysm then is shielded from the blood flow and typically shrinks over time. The advantages of EVAR V.S. open repair are shorter hospital stay (1 to 2 days V.S. 5 to 10 days), lower surgical mortality (<1% V.S. 3 to 10%), dealing with sicker patients (in the U.S. not in Europe), and relatively simple anesthetic monitoring system for less hemodynamic disturbance. The disadvantages of EVAR are higher long-term complications such as endo-leak and renal dysfunction. The EVAR is also limited by the anatomical structure of aneurysms. It mainly means the neck and distal angle of the aneurysm.

Preoperative Patient management

The predominant age of patients with aortic aneurysms is elderly (about 80% of our patients are 70s to 80s). The major causes are atherosclerosis, dysfunctional connective tissue diseases (e.g., Marfan's), and genetic. Most of patients are comorbid hypertension (HTN), coronary artery disease, COPD (often related to long-term of smoking history), diabetes (DM), chronic renal insufficiency, and peripheral vascular disease. Carefully preoperative patient evaluation is the key of successful perioperative management.

Open Repair 

Laboratory evaluation: Routine laboratory tests including ECG and chest x-ray. Stress cardiac echogram for cardiac functional test is recommended especially to those who are potentially subjected to higher (super-renal) clamp. Pulmonary functional test is not required but would be benefit in postoperative management to those who have history of COPD.

Treatment of Comorbidities

Optimizing HTN, DM, and cardiac function. Controlling the arrhythmia. The management of ischemic heart disease is controversial. In our institution patients with cardiac ischemia will be treated before open aneurysm repair.

EVAR

In the U.S. most of patients for EVAR are ASA PS III or IV which indicate severe comorbidities. Routine laboratory test should be checked. Special attention should be paid to renal function for large radial contrast usage. Knowing of coagulatory status will help to choose the methods of anesthesia.

Management of Anesthesia

Managing the anesthesia of patients undergoing open aortic surgical repair is a great challenge. The anesthesiologist's role in myocardial, renal, and neurological protection is crucial to the patient's overall outcome. Each case presents different challenges, and there is no one right way to manage the patient intraoperatively. The anesthetic choice of open repair is almost always general. Using invasive monitors will depend on comorbidities and the level of aortic clamp. Instruments for dynamically monitoring (such as TEE) have been more and more recognized but their effects on improving of outcomes are not very clear. EVAR has broad choices of anesthesia for its “minimal invasive” approach. Anesthetic choices can be from MAC to general. Most common approaches are spinal anesthesia or general end tracheal intubating anesthesia (for breathing control to make clear pictures). The requirement of anesthesia is often a single large-bore IV access and an arterial line for monitoring. Special consideration s are renal function protection, patients’ selection for lumbar drainage (spinal cord protection), and blood pressure control for higher level repair (No specific requirement for all the newer grafts).

Summery

Compared with open repair, endovascular surgery is less invasive and associated with shorter surgery, less bleeding, and shorter intensive care unit and hospital stay. Operative mortality and moderate and severe complications are less common but the difference is not statistically significant in European studies.

In the long term, other factors influencing clinical decision making include one-year failure rate, late mortality, conversion to open repair, outcomes for larger aneurysms, adverse effects, and costs associated with endovascular repair.