Aneurysms pose an ever-present threat to life because of their unpredictable tendency to rupture or embolize. Most centers are able to offer an endovascular approach to 60% to 70% of their patients needing repair of an infrarenal aortic aneurysm. (Higher involvement typically requires an open technique.)

1. Epidemiology and Pathophysiology of Abdominal Aortic Aneurysms
   1. Risk factors for aneurysm included advanced age, smoking for >40 years, hypertension, low serum high-density lipoprotein cholesterol, high level of plasma fibrinogen, and low blood platelet count.
   2. The risk of aortic rupture is related to the absolute diameter of the aortic aneurysm sac. The risk of rupture increases when the aneurysm is >4.5 to 5 cm in diameter (important to screen high-risk populations to permit elective repair at the appropriate time).
2. Endovascular Repair versus Open Repair versus Medical Management
   1. In general, EVAR has lower perioperative risk than open aortic repair (OAR) but a similar 2-year mortality rate. Also, EVAR has a higher incidence of leak, thus necessitating a lifetime of surveillance. OAR may be better suited for younger patients who do not want a lifetime of surveillance and who may have a better perioperative risk profile.
   2. It is important to understand that an AAA is one manifestation of widespread vascular disease caused by multiple medical comorbidities (not a discrete disease).
   3. EVAR has not reduced the cost of AAA repair despite a 3- to 5-day shorter hospital stay. (The cost of the device and the need for additional interventions, particularly radiologic follow-up of endovascular leaks, typically nullifies any cost savings.)
   4. More than half of patients undergoing emergency AAA repair and more than one quarter of those having elective repair suffer myocardial necrosis as determined by cardiac troponin levels (myocardial injury is less with EVAR than OAR).
   5. Renal function deterioration does not appear to be affected by the choice of surgical approach.
   6. Renal function deterioration does not appear to be affected by the choice of surgical technique.
   7. Monitoring and Vascular Access. Although the incidence of perioperative conversion from EVAR to OAR is <1%, there still remains a real risk for the need for emergent proximal arterial control, first with an EndoClamp and then with an aortic cross-clamp.
   8. Local and Regional Anesthesia. EVAR may be carried out under almost any type of anesthesia, including local, regional, neuraxial, and general techniques (depends on preoperative factors such as platelet inhibitor use, low-molecular-weight heparin use, comorbidities limiting a patient's ability to lie flat for extended periods such as with severe COPD and on intraoperative factors such as anticipated duration, difficult arterial access, or tortuous iliac arteries).
   9. Conversion from EVAR to OAR may occur in the setting of difficult arterial access, vessel dissection at the arterial access site, poor anatomic parameters for EVAR such as with tortuous iliac arteries, stent malposition, stent migration, and aneurysm rupture.
   10. Complications (Table 39-8: Complications of Endovascular Abdominal Aneurysm Repair)
3. Open aortic repair requires continuous arterial blood pressure measurement, large-caliber venous access, and the ability to reliably and quickly administer medications. It may also be helpful to monitor certain aspects of cardiac function (transesophageal echocardiography [TEE]), to increase spinal perfusion pressure (maintain higher arterial blood pressure and lower cerebrospinal fluid pressure with a drain), and to minimize postoperative pain (thoracic epidural).
   1. Aortic Cross-Clamping and Unclamping
      1. Infrarenal aortic clamping carries the lowest risk for patients; supraceliac clamping carries the highest. Clinicians should be aware that 10% to 20% of “infrarenal” aortic disease actually involves the suprarenal portion of the aorta, necessitating suprarenal clamping.
      2. Ruptured aneurysms often must be controlled initially by supraceliac clamping because of anatomic considerations.
      3. Reperfusion after unclamping the aorta causes systemic release of an acute load of potassium, acid, and other mediators. This can result in severe arterial hypotension unless aggressive therapy (no evidence one is superior to the other) is undertaken before unclamping (fluid loading with or without vasopressors or calcium) (Fig. 39-3: Systemic hemodynamic response to aortic unclamping). Much preferable to pharmacologic manipulation is gradual unclamping, unclamping with gradual sequential release of bilateral femoral pressure, or restoring flow to one leg at a time in aortobifemoral grafts.
   2. Management of Elective Open Aortic Repair
      1. Hemodynamic management during OAR requires the clinician to anticipate the sudden changes in intravascular volume and systemic vascular resistance seen during clamping, unclamping, and bleeding. Prehydration may limit variations in blood pressure during surgery. The patient's vital signs should be kept within 20% of his or her normal range as long as the heart rate does not exceed 80 to 90 beats/min and signs of organ ischemia are absent.
      2. Left ventricular end-diastolic volume can be assessed by TEE.
      3. It is important to maintain temperature homeostasis.
      4. The application of an aortic cross-clamp causes a sudden increase in system vascular resistance, which in turn may cause deterioration in myocardial function. At the time of occlusion, a vasodilating drug is available for immediate use if needed. Alternatively, the concentration of volatile anesthetic may be increased or a local anesthetic may be injected into the epidural catheter; both require careful attention to avoid hypotension.
      5. During emergence from anesthesia and in an effort to prevent hemodynamic variations outside the patient's normal range, the clinician can infuse nitroglycerin, esmolol, or other β-adrenergic blocking agents.
4. Thoracic and Thoracoabdominal Aneurysm Repair
   1. Coincident coronary artery disease and chronic obstructive pulmonary are common. Lung isolation is required to facilitate surgical access, and the need for postoperative ventilation is assumed.
   2. Distal perfusion can be used to limit the duration of renal and mesenteric ischemia. Partial bypass, with or without an oxygenator, can be used to direct part of the patient's blood flow from either a pulmonary vein or the left atrium to the femoral artery.
5. Management of Emergency Aortic Surgery. The most common cause of emergency aortic repair is a leaking or ruptured aortic aneurysm. (Symptoms of ruptured AAAs include pain, faintness or frank collapse, vomiting, and pain in the back or abdomen.)

Anesthesia for Vascular Surgery

1. Vascular Disease: Epidemiologic Medical and Surgical Aspects
2. Chronic Medical Problems and Management in Vascular Surgery Patients
3. Other Medical Problems in Vascular Surgery
4. Organ Protection in Vascular Surgery Patients
5. Carotid Endarterectomy
6. Aortic Reconstruction
7. Lower Extremity Revascularization