AMx - EVAR (Endovascular aneurysm repair)





Issues

Patient issues

  • Vasculopath
  • Patient may be too unwell for open surgery

Anaesthetic issues

  • Remote location / special-purpose theatres
  • Hypothermia
  • Changes in BP
    • Deployment of stent-grafts can use rapid increase in BP
      • Less with newer generation
    • Surgical team may request lower SBP to minimise movement of stent before final deployment with balloon

Surgical issues

  • Long duration
  • Blood loss
    • Risk of catastrophic blood loss if rupture
    • Loss around puncture site difficult to estimate
      • Normally a slow trickle around puncture site
    • May be accompanied by coagulopathy
  • Risk of periop organ failure
  • Intraop surgical requests
    • Heparin ± protamine
    • Breath holding
    • Lower BP



Assessment

HxPC

  • Size of aneurysm
  • Level
    • Thoracic or abdominal?
    • Relation to aortic branches (e.g. renal, celiac)
      • Above or below?
      • Distance from them
      • If <1.5cm away
        • Likely to need special stents
        • Longer procedure time
        • Higher risk of complications
  • Speed of growth
  • Any symptoms

PMHx

  • Co-morbidities
    • CVS disease
    • DM
    • Smoking
    • CVA / TIA
    • Renal function
  • Functional status
  • Meds
    • Potentially nephrotoxic
      • ACE inhibitors and AIIRA
      • Aminoglycosides
      • Diuretics
      • NSAIDs
    • Antiplatelet agents

Ix

  • ECG
  • CXR
  • CT imaging of the AAA ... with 3D reconstruction
  • If poor functional status or CVS symptoms
    → Strongly consider non-invasive cardiac stress test
    • e.g.
      • Stress myocardial perfusion
      • Dobutamine stress ehocardiography
    • If positive non-invasive stress test
      → Coronary angiography ± revascularisation
  • Blood tests
    • Routine
    • Cross-matching



Goal

  • Optimise myocardial O2 demand / supply ratio

  • Monitor and prepare for heavy blood loss

    • Adequate access and monitoring
    • Cross-matched blood
    • Consider blood salvage
    • Correct coagulopathy (including hypothermia)

  • Minimise risk of periop acute kidney injury

    • Avoid potentially nephrotoxic drugs
    • Minimise contrast exposure
    • Appropriate fluid therapy
    • Consider N-acetylcysteine

Plan

Preparation

Monitoring

  • Standard monitoring
  • AL
    • Use right radial artery if possible
    • Left brachial artery may be needed
      ... if chimney or branched endograft used
  • CVP monitoring may be necessary
  • Urinary catheter

Access

  • Large-bore IV access
  • Consider CVL for vasopressors and N-acetylcysteine (NAC)

Equipment

Make sure available...

  • Cross-matched bloods
  • Vasoconstrictors
  • Heparin
  • ? Vasodilators
    • Less likely than with open repairs
    • Usually a combination of bolus propofol, opioid, or increased volatile agent would be sufficient

Intraop

Choice of anaesthesia

GA + ETT → Normally necessary for patient comfort due to long duration

Intraop anticoagulation

  • Needs anticoagulation with heparin before the guidewire and the dilator is deployed
    • Usually 5000 IU of heparin is sufficient
    • Some may request 100 IU/kg

⦿ NB:

  • Reversal is usually unnecessary
  • If reversing with protamine is requested at the end of procedure
    • 0.5 to 1 mg for every 100 IU heparin used
    • Small risk of thrombosis in the stents and/or vessels

Deployment

  • Possible haemodynamic disruption
    • Rapid increase in BP
    • May need to lower BP to lower risk of stent migration
  • May require breath-holding

Postop

Consider HDU / ICU