Endovascular Aneurysm Repair (EVAR)

The curriculum references this topic as: 'explains the management of patients for endovascular radiological procedures'.

It also makes explicit reference to the likelihood of remote anaesthesia for such cases.

Resources

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

The evidence from multiple trials demonstrates no improvement in 30 day mortality with endovascular vs. open techniques

Repair of a simple infra-renal aneurysm involves catheterising the femoral or iliac arteries, or less commonly the brachial or subclavian arteries

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

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

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

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)

Long-term complications