ENDOVASCULAR ANEURYSM REPAIR (EVAR)

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Endovascular Aneurysm Repair (EVAR) is a minimally invasive surgical procedure used to treat an abdominal aortic aneurysm (AAA), a bulging or weakened area in the wall of the aorta, the largest artery in the body. AAA is a potentially life-threatening condition, as the aneurysm can rupture and lead to severe internal bleeding and possibly death.

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EVAR is performed using a stent-graft, which is a specialized tube made of fabric and metal mesh. The procedure involves the following steps:

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1. Preparation: The patient is given general or regional anesthesia to ensure comfort during the procedure. The surgeon may also administer antibiotics to reduce the risk of infection.

2. Access: The surgeon gains access to the arterial system by making small incisions in the groin area. Through these incisions, catheters (thin, flexible tubes) are inserted into the femoral arteries on both sides.

3. Imaging: Using X-ray guidance and contrast dye, the surgeon navigates the catheters through the patient's arterial system and positions them near the aneurysm.

4. Deployment of the stent-graft: The stent-graft is compressed and loaded onto a delivery device, which is then inserted through the catheter. Once the stent-graft is properly positioned within the aorta, it is expanded to fit snugly against the walls of the artery, effectively creating a new path for blood flow and bypassing the aneurysm.

5. Verification: The surgeon verifies the correct positioning and functioning of the stent-graft using imaging techniques. This ensures that the aneurysm is excluded from blood circulation and reduces the risk of rupture.

6. Closure: Once the stent-graft is in place, the catheters are removed, and the incisions in the groin are closed with sutures or staples.

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EVAR offers several advantages over traditional open surgical repair, including shorter recovery time, reduced pain and blood loss, and a lower risk of complications. However, it may not be suitable for all patients, particularly those with complex aneurysms or other medical conditions that increase the risk of complications. Regular follow-up appointments and imaging studies are necessary to monitor the stent-graft and ensure the long-term success of the repair.

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An abdominal aortic aneurysm (AAA) is a localized, abnormal enlargement or bulging of the abdominal aorta, which is the largest artery in the body. The aorta is responsible for carrying oxygenated blood from the heart to the rest of the body. In the case of an AAA, the weakened section of the aortic wall becomes prone to rupture or dissection, potentially causing life-threatening internal bleeding.

                                                                                                 

                                                                Anesthetic Implications for EVAR

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Anesthesia type: General, regional, local infiltration with sedation.

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Airway: Endotracheal tube

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Preoperative:

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• Identify high-risk patients for preoperative optimization

• Risk factors of abdominal aortic aneurysm (AAA): increasing age, male gender, smoking, elevated plasma cholesterol levels, hypertension, and family history 

• Patients are vasculopathic

• Assume patients have disease of cerebral, cardiac, renal, and peripheral vasculature

• Smoking is the greatest risk factor

• The patient population undergoing EVAR have multiple underlying comorbidities

• Surgical repair of a AAA is recommended once the aneurysm expands to more than 5 cm

• Advances in endovascular procedures have made AAA repair less invasive

• EVAR should be conducted in a specialized radiology suite 

• The surgeon does not have to cross-clamp the aorta

• Major advantages of EVAR vs open repair: less blood loss, fewer transfusions, less hemodynamic perturbations, no cross-clamp of the aorta, fewer overall complications, faster ambulation, shorter hospital stay

•  Arterial line should be placed contralateral to the upper limb surgical access

• Large bore venous access should be placed

• Consider central venous access for longer procedures

• 5-lead electrocardiogram (monitor for ST changes) 

• Evoked potentials monitoring may be requested for high-risk of spinal cord ischemia (SCI) patients

• Have access to rapid infusion devices

• Have IV fluid warmers and blood transfusion tubing available

• Patients are commonly on antiplatelet medications

• Bladder catheterization is indicated to monitor urine output

• Prep from nipples to knees in case it converts to open repair

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Intraoperative:

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• An endograft is placed in the lumen of the aorta at the level of the aneurysm

• The device is advanced and deployed via the femoral arteries

• Endograft position is assessed under fluoroscopy

• Provide hemodynamic stability, perfusion to vital organs, avoid imbalance in myocardial oxygen supply and demand, maintain intravascular volume, maintain normothermia and manage bleeding

• Be prepared for open repair and massive bleeding

• Heparinization and activated clotting time (ACT) checks 3 min after heparin and every 30 min thereafter

• Minimizing renal impairment: adequate hydration, limiting contrast, avoidance of nephrotoxic drugs 

• Deployment of the stent graft within the aorta is normally pain free

• The artery of Adamkiewicz (supplies the anterior spinal arteries and perfuses the anterior third of the spinal cord) is at risk from occlusion with stent grafts that extend suprarenally​

• Spinal drains have been shown to be beneficial in the prevention and reversal of SCI 

• Stent deployment takes case during apnea (hold ventilation)

• Stent deployment can result in transient ischemia distal to the graft

• Muscle relaxation is indicated

• Position: Supine with arms tucked

• EBL: Minimal

• Marked hypotension may indicate a retroperitoneal bleed or intra-abdominal bleeding

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Postoperative:

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• Perform neurologic exam

• EVAR reduces the time spent in the intensive care unit

• Heparin reversal with protamine might be required at the end of the procedure

• Intensive care unit admission

• No flexion at the groin for several hours after removal of arterial sheath

• Regular lower limb arterial assessment

• Pain is usually minimal

• Postimplantation syndrome: pyrexia, leukocytosis and elevated inflammatory markers. Manifests as sepsis but without evidence of infection. 

• Avoid hypertension on emergence

• Avoid coughing and bucking on emergence

• Hospital stay is 2-3 days

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Complications:

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• Cardiac complications are the most common

• Endoleak

• Spinal cord ischemia (SCI) 

• Arterial rupture/arterial dissection

• Aneurysm rupture

• Damage to the femoral arteries

• Graft migration

• Infection

• Paralysis

• Venous thromboembolism

• Bowel ischemia

• Renal artery occlusion from stenting

• Stroke

• Arrhythmia

• Acute renal failure

• Acute coronary syndromes

• Postimplantation syndrome

• Reaction to contrast media

• Postoperative delirium in the elderly

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Sources:

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Macksey, L. F. (2011). Surgical procedures and anesthetic implications: A handbook for nurse anesthesia practice. 

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Jaffe, R. A. (2020). Anesthesiologist's Manual of Surgical Procedures (6th ed.). 

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Kothandan H, Haw Chieh GL, Khan SA, Karthekeyan RB, Sharad SS. Anesthetic considerations for endovascular abdominal aortic aneurysm repair. Ann Card Anaesth. 2016 Jan-Mar;19(1):132-41. doi: 10.4103/0971-9784.173029. PMID: 26750684; PMCID: PMC4900395.

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Singh-Radcliff, N. (2013). 5-Minute Anesthesia Consult.

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V Nataraj, MD FRCA, AJ Mortimer, BSc MD FRCA, Endovascular abdominal aortic aneurysm repair, Continuing Education in Anaesthesia Critical Care & Pain, Volume 4, Issue 3, June 2004, Pages 91–94, https://doi.org/10.1093/bjaceaccp/mkh025

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