Open AAA repair

Indications

Patients who cannot undergo EVAR
- Unfavourable anatomy for EVAR
  - No aortic neck/hostile aortic neck (main indication)
  - Proximal aortic necks that are short (<2cm), angled, trapezoidal, have a high burden of thrombus, or are heavily calcified can compromise seal
  - Iliac artery occlusive disease (especially chronic total occlusion) can mean EVAR Is hard
  - Concomitant CIA or EIA aneurysms (might still be able to do EVAR)
  - Horseshoe kidney
  - Where IMA patency needs to be preserved
- Coexisting disease processes
Emergency situations and endovascular unavailable
Younger patients (EVAR durability is questionable)
Patients with complex aortic neck anatomy (pararenal/suprarenal aneurysms)
Conversion of EVAR
- Failure of EVAR due to migration or recalcitrant endoleak that is unable to be resolved by endovascular means
- Tends to be a much more complex operation than de novo AAA repair
- Don't have to completely remove the previous EVAR graft unless it's infected
Infection of native aorta or previous repair
- Can't be done as open unless in certain situations

Outcomes

Mortality rates with pararenal/ruprarenal AAA repair approach 5-10%
- Infrarenal repair <5%

Preparation

Import external scans
Confirm intended proximal clamp zone and warn aesthetist
Confirm required aortic graft stock is in the hospital
Document lower limb pulses and neurologic status
Crossmatch 4 units
Book ICU bed
Book cell saver

Operative plan should include

Extent of resection
Location of cross-clamp application
Qualitative assessment of aorta
Evaluation of visceral vessel topography and patency
- IMA preservation may be indicated if there is significant SMA disease. Can be done by either re-implanting into graft, or from a sidearm attached to the graft
Identification of aneurysmal or occlusive iliac disease
Need for concomitant renovisceral reconstructions

Patient preparation

CARP trial - only patients with left main coronary artery disease, EF<20% and valvular disease should have that fixed prior to AAA.
Cell saver

Approach (essentially transperitoneal vs retroperitoneal)

Transabdominal approach favoured by most, through midline laparotomy
- Better in emergency - quicker and easier
- Good access to infra-renal AAA, but more difficult to expose visceral aorta
- Better access to iliacs and right renal artery this way

Transabdominal AAA repair

Setup

Supine with arms out
Prep from nipples to knees

Approach

Midline laparotomy
Omentum and transverse colon brought cephalad
Root of mesentery and small bowel retracted to right and maintained with retractor like Omnitract
Divide ligament of Treitz and retroperitoneum tissues over aneursym itself
- Avoid injury to IMV, but can be ligated if necessary
- Track the right of the aorta to avoid injury to IMA, sigmoid mesentery and autonomic nervous plexus at the bifurcation
If the aneurysm itself is covered by left renal vein, may need to ligate the branches to retract it superiorly

Supracoeliac clamping

Most useful in setting of ruptured AAA or juxtarenal AAA
Requires specific steps
Consider renal preservation therapy
Aim clamp time <30mins

Aortic repair

Aortic sac opened longitudinally, and mural thrombus and debris are evacuated with care
Reconstruction with appropriate Dacron or polytetrafluoroethylene (PTFE) tube grafts
Cover graft with aortic sac and omentum to reduce migration

Closing

Careful haemostasis - look at intercostals and lumbar vessels

Post-op:

Check distal perfusion in recovery
SCDS and enoxaparin, no TEDS
Monitor fluid balance carefully
NPO until any ileus resolved
Neurovasc obs
Antibiotics as per surgeon

Follow-up

Wound review 2-6 weeks
Aortoiliac USS at 6 months with clinic review
Surveillance imaging every five years, or more often in clinical concern
Check popliteals and thoracic aorta
Remind family members to be screened for AAA
Long term risk factor management with GP
Repeat duplex 2-5 years post-op for progressive suprarenal or iliac aneurysm. GP can arrange.

Complications

Early
- Cardiac
  - Up to 10%
  - Risk factors:
    - Recent MI, old age, diabetes, poor functional status, arrhythmia, or CCF
  - Ensure patients are on aspirin, statin, beta blockers (aim HR< 60, BP <100
- Pulmonary
  - Periop smoking cessation, optimal bronchodilator therapy, chest physio
  - Delayed extubation if more complex repair involving higher proximal aortic control
  - 17% get pneumonia
- Renal
  - AKI rate is 10%-20%
  - Consider failed renal artery reconstruction or cholesterol embolization
  - Close attention to volume status
- Colonic ischaemia
  - 0.2-6%
    - 4% for tube grafts
    - 2.7% for aorto-iliac grafts
    - 22% for an aortobifemoral graft
  - Operative risk factors:
    - Ligation of IMA
    - Failure to revascularise hypogastric arteries
  - Patient factors:
    - Pre-existing iliofemoral occlusive disease
    - Previous colonic resection
  - Signs:
    - Early post-op diarrhoea
    - Melaena
    - Haematochaezia
  - Investigation
    - Flex sig/colonoscopy
    - CT
  - Management
    - Aggressively resuscitatied
    - Broad-spectrum Abx
    - Partial-thickness ischaemia/stable patient: conservative. Mostly doesn't progress to full-thickness necrosis, but still can.
    - Full-thickness ischaemia/peritonitic/unstable: urgent laparotomy and bowel resection. Mortality 55%. Thorough assessment of IMA - if vigorous back-bleeding, probably ok.
- Lower extremity ischaemia
  - Operative factors:
    - Anastomotic complications
    - Clamp injury
    - Acute thrombosis
    - Acute embolic disease
  - Management:
    - Treat the cause
    - All the above causes need intervention
- Spinal cord ischaemia
  - Extremely rare
  - Extent of proximal coverage of aorta is the biggest risk factor
  - CSF drainage and pelvic revascularisation are main treatments
- Venous thrombosis
  - Clinically rare due to systemic anticoagulation