Endovascular aneurysm repair

aortic aneurysm
The stent occludes the aneurysmal sac allowing blood to flow across the aneurysm with eventual thrombosis of the aneurysmal sac

adv from ↓ invasive:

↓ physiological insult and stress response,
↓ blood loss
↓ haemodynamic instability,
no cross-clamping induced morbidity
quicker ambulation → ↓ LOS

aortic aneurysm#Key trials on Open vs Endovascular aneurysm repair EVAR for AAA

Older, frailer patients are more likely to be offered EVAR

younger, fitter patients with longer life expectancy will usually be offered OR, avoiding

long-term surveillance of grafts
- repeated radiation
- contrast exposure
potential longer-term complications of EVAR

Standard EVAR is classified as an intermediate risk procedure, complex EVAR is higher

similar consideration to open repair

CPET is routinely performed in many units. Results which indicate increased risk in the perioperative period include:

Peak oxygen consumption (pV02) of < 15ml/kg/minute
Anaerobic threshold of < 10.2 ml/kg/minute
Any cardiac ischaemia induced during testing.

Protamine is not usually required to reverse heparin unless there is excessive bleeding at the time of closing the groin wounds.

GA vs RA vs LA

IMPROVE trial identified that EVAR under LA is associated with a fourfold ↓ in mortality compared with GA, adjusted for age, sex, Hardman index and other factors

Increasingly, EVAR is performed without GA, which has the benefit of avoiding

haemodynamic disturbance
hypotension of anaesthesia
ventilation and weaning

Favour GA if:

Surgical factors
- longer duration
- vascular access via upper limbs
- ↑ potential of major blood loss
Patient factors
- ability to lie still for the duration of OT
  - affected by pain / anxiety / agitation
- compliant
- ability to breath hold
  - improves picture quality

Whichever anaesthetic mode is employed, the overall aims are the same:

maintaining patient comfort for 3–4 hours while supine
maintaining temp and hydration throughout
maintaining stringent BP control
- esp at time of stent deployment
preparation for major blood loss
monitoring anti-coagulation.

GA

adv of GA:

↓ patient anxiety and difficulties lying flat
Optimal positioning and ↓ patient movement
Controlled suspension of ventilation for stent deployment
↓ time pressure cf RA / LA

Cardiovascular stability must be maintained during airway manipulation and surgical stimulation

Given only two small groin incisions (or percutaneous approach) are required for EVAR, LA infiltration is usually sufficient to manage postoperative pain. Occasionally, opioids may be required

RA / LA

adv

avoids the sympathetic stimulation a/w airway manipulation
↓ need for cardiovascular depressant anaesthetic agents
↓ alteration in lung dynamics
possibly earlier detection of aneurysmal rupture,
- as patient may c/o retroperitoneal pain.

if CSE → removal of catheter needs to be timed ∵ given IV heparin

Complication

Postoperative renal dysfunction is common in EVAR patients. The main causes are:

emboli being dislodged during stent deployment
damage to renal arteries from catheter wires (stenosis or aneurysm)
stent grafts either blocking renal arteries or causing an inflammatory reaction
reperfusion injury from prolonged lower limb ischaemia
intraoperative hypotension or hypovolaemia
use of intravenous contrast agents.
To avoid postoperative renal dysfunction adequate hydration should be maintained, the use of contrast limited as much as possible and nephrotoxic drugs avoided

spinal cord ischaemia :
very rare complication following infra-renal EVAR and more likely with fenestrated or branched EVAR surgery
caused by

occlusion of spinal cord feeder vessels by the graft
- (largest being the artery of Adamkeiwicz arising from T9-T12),
thromboembolic event,
anaemia
perioperative hypotension

Complications specific to EVAR include

Immediate surgical Cx
- failed / mal-deployment of stent
- arterial rupture / dissection
- embolisation / ischaemia of spinal cord / kidneys / bowels
endoleak
- (persistent blood flow into the aneurysm sac)
post implantation syndrome
- Endovascular stent grafting → SIRS
  - ↑ inflammatory markers,
  - coagulopathy
  - pyrexia
- occurs in a mild form in ~30% of patients
  - usually self limiting & benign
- clinically apparent only in a much smaller percentage
thrombosis & complications of femoral artery access
- vessel injury
- haemorrhage.

References

Endovascular Aortic Aneurysm Repair A Review of Anesthesia Concerns and Perioperative Management

Anaesthesia for Ruptured Aortic Aneurysm - A&ICM

Anaesthesia for Endovascular Aneurysm Repair - A&ICM