- Repair of a simple infra-renal aneurysm involves catheterising the femoral or iliac arteries, or less commonly the brachial or subclavian arteries
- This can be achieved percutaneously or with a surgical cut-down
- One or more expandable grafts are then passed into the aorta under fluoroscopic guidance
- The stent is thus deployed, preventing blood flow into the aneurysmal sac, which will eventually thrombose
- Juxta- and supra-renal aneurysms require use of fenestrated grafts ('FEVAR') with orifices for the coeliac, superior mesenteric and renal arteries
- These fenestrated grafts are custom-made following 3D reconstruction of CT angiography
- More complex grafts lead to longer procedure and fluoroscopy time
- Patients are therefore submitted to higher doses of iodinated contrast
- Although carbon dioxide contrast can be used, it carries its own risks e.g. gas embolism and higher radiation doses
Endovascular Aneurysm Repair (EVAR)
Endovascular Aneurysm Repair (EVAR)
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- Endovascular aneurysm repair (EVAR) can be used for elective treatment of abdominal or thoracic ('TEVAR') aneurysms in lieu of an open repair
- The choice between open repair and EVAR depends on patient factors such as age, co-morbidities and aneurysmal morphology
- EVAR may be particularly useful for juxta- and supra-renal aneurysms, where the effects of cross-clamping during open repair are more deleterious
- Ultimately, the decision of open repair vs. EVAR will take place in the MDT setting
- EVAR can also be used for the emergency management of ruptured AAAs
- The evidence from multiple trials demonstrates no improvement in 30 day mortality with endovascular vs. open techniques
Benefits | Risks |
Less haemodynamic and metabolic physiological disturbance | Need for conversion to open procedure (~2%/yr) |
Reduced blood loss and need for large transfusion | Long-term complications (see below) and need for re-intervention |
Avoids short- and long-term complications of laparotomy | Lifelong, annual, ultrasound or CT surveillance required |
Less pain | No decrease in long-term all-cause mortality after 4yrs (EVAR1 study) |
Reduced length of stay (ICU and hospital) | No long-term survival benefit vs. surveillance in patients unfit for open surgery (EVAR2 study) |
Lower 30-day and medium-term mortality (EVAR1) |
- Pre-operative management of patients booked for EVAR is similar to those undergoing open repair
- EVAR should be carried out in a hybrid theatre (IR facilities with ability to convert to an open procedure if required)
- The risks associated with remote anaesthesia apply if the procedure is taking place in IR or if hybrid theatres aren't in the main theatre complex
Monitoring
- Access to the patient is more limited, so sufficient length on monitoring cables and IV lines is required
- Arterial line insertion should be on the side contralateral to surgical access, in case UL access is needed
- Large bore IV access is required, though central venous access is reserved for procedures predicted to be long or complicated
Anaesthetic technique
- No robust evidence for morbidity or mortality benefit of any one anaesthetic technique over another
- The technique used should be based on patient factors including preference, anticoagulant drugs, ability to lie flat and duration of surgery
- Breath-holds (i.e. apnoea) are required for brief periods to improve image quality for digital subtraction angiography, so mandatory ventilation is preferable in the patient under GA
- Neuraxial techniques are acceptable, though intra-operative heparinisation should prompt careful consideration of the timing of removal of epidural catheters
- Short, simple procedures may even be done under LA
- Blood loss in simple infra-renal EVAR is ∽200ml
- This may be greater in more complex and/or longer procedures
- An unexpected transfusion requirement should prompt suspicion of occult blood loss e.g. groins, retroperitoneal
Early & short-term complications
- Conversion to an open procedure (2%/yr), with a higher incidence in female patients or smaller patients
- Arterial rupture or dissection; the highest risk of rupture is during stent deployment
- Plaque rupture & embolisation
- Ischaemia of bowel, kidneys or buttocks/legs from prolonged femoral/iliac artery occlusion
- Spinal cord ischaemia
- Rare in infra-renal EVAR (0.21%) but higher in complex EVAR, supra-renal EVAR or TEVAR
- Occlusion of thoracic/lumbar collaterals to the spinal cord, particularly the artery of Adamkiewicz, by stent grafts may impair blood supply
- High-risk patients may have CSF drained pre-operatively (perfusion pressure = MAP – CSF pressure)
- Post-implantation syndrome (30 - 40%)
- A self-limiting, non-infectious rise in temperature, white cell count and CRP
- Due to endothelial reaction
Long-term complications
- Endoleak, of which there are five subtypes
- Infection
- Graft migration
- Delayed rupture