Carotid Endarterectomy

Airway: ETT or spontaneous ventilation.
Access: Large IVC, arterial line.
Pain: Minimal
Position: Supine, neck extended and rotated
Time: ~90 minutes total
Blood loss: 100-300ml
Special: Additional monitoring may include stump pressure monitor, cerebral perfusion monitor, or patient interaction with regional techniques

Resection of ICA plaque to reduce the risk of embolic stroke in patients with ICA stenosis. Performed:

To reduce risk of embolic stroke
Indication (and risk) depends on degree of stenosis:
- No risk at 100% occlusion
- Symptomatic stenosis between 70-99%
  Symptomatic if:
  - Focal neurological disease
  - Sudden onset
  - Appropriate distribution
- Symptomatic moderate stenosis between 50-69%
  Depends on patient factors.
- Asymptomatic patient between 80-99%
  Provided surgical risk of CVA is ⩽3%.
Under GA or regional
Broadly; no major difference provided technique is done well.
- Regional:
  - Pros:
    - Best neurological monitoring
    - Reduces haematoma
      Lower BP during closure and emergence.
    - Avoids risks of airway intervention
    - Lower shunt rate
  - Cons:
    - Surgeon comfort
    - Patient compliance
    - Risk of conversion to GA with limited access to head
    - Risks of siting blocks
    - Anxious patient and myocardial stress
- GA:
  - Pros:
    - Immobility
    - Controlled ventilation
    - Attenuated stress response
  - Cons:
    - Limited neurological monitoring
    - Intraoperative hypotension
    - Delayed GA recovery may mask neurological complications

Considerations

Get SET:

Centre must have M&M of <6%
Stroke risk of procedure must be substantially less than that of doing nothing.
A
- LMA may reduce carotid blood flow - consider using ETT.
- Head is inaccessible during surgery
C
- Arterial line required
- Co-existing CVS disease
  Particularly HTN.
- Plan for management of cross-clamping
  - Accurate measurement of normal BP
    Measure in both arms, and target the highest intraoperatively.
- Haemodynamic management
  - Impaired autoregulation after VA
  - Altered baroreceptor activity following carotid surgery
D
- Use of cerebral perfusion monitoring
  - Regional techniques
    Deficits may present as:
    - Immediate unconsciousness upon clamping
    - Immediate subtle deficit
    - Delayed deficient
      Typically related to hypoperfusion.
  - EEG monitoring
    - Commence prior to anaesthesia
    - Usually requires an electrophysiologist
    - Less affected by TIVA than volatile
    - Best predictor of cerebral ischaemia with low-stump pressure
  - SSEPs
    Usually bilateral median nerve.
  - Transcranial doppler
    Monitors both flow and emboli. Disadvantages:
    - Operator dependent
    - Placed near surgical site
  - Cerebral oximetry
    - Monitors anterior circulation
    - Non-quantitative
  - Jugular venous bulb oximetry
  - Stump pressure
    Transducing distal carotid stump as an indicator of efficacy of cerebral perfusion.
    - Less commonly performed now
    - Ischaemia is rare when stump pressure is >40-50mmHg
  - Regional CBF
    Generally unavailable.
- CVA recency
  Reperfusion within one month of the original infarct may lead to haemorrhagic transformation of ischaemic brain.
  - Reasonable to perform surgery within 2 weeks if no specific contraindications
- Regional technique
  Involves:
  - Choice of anaesthesia
    Usually combination of superficial and deep cervical plexus block, but may include:
    - Layered block
      Local field block performed in each dissection plane by the surgeon.
      - Useful as a rescue for failed block
    - Cervical epidural
      Rarely performed.
    - Superficial cervical plexus block
      - Does not provide muscular relaxation
    - Deep cervical plexus block
      - Provides muscle relaxation
      - Greater incidence of complications

Preparation

Standard ANZCA monitoring
5-lead ECG
Arterial line
Transduce at the level of the EAM.
Bilateral blood pressure monitoring

Induction

Haemodynamically stable induction

Intraoperative

Patient comfort in regional technique:

Judicious conscious sedation
Options include:
- Propofol TCI
- Midazolam
- Clonidine
  1μg/kg, then 1μg/kg/hr.
- Dexmedetomidine 3μg/kg/min for 10 minutes to give a load of 0.5μg/kg, then ↓ to 0.1μg/kg/hr (titrated to effect).
Continual communication
Use of a non-heated mattress
Padding and support of all pressure areas
Ensure bladder emptied
Minimise IVT to prevent need to void
Water to wet the lips appropriate, but drinking may precipitate choking/coughing/aspiration, and is to be avoided

Complications:

Bradycardia
- Usually due to carotid baroreceptor manipulation
- Requires:
  - Cessation of surgical stimulation
  - Atropine
    CPR may be required in profound bradycardia.
  - Surgical infiltration of local anaesthetic

Surgical Stages

Can be divided into four stages:

Exposure
- Oblique neck incision
- Division of common facial vein
- Exposure of carotid artery
- Control of common carotid, internal carotid, and external carotid
- Administration of heparin
  Usually 5000 units prior to clamping.
Clamping
Sequential clamping of internal, external, and common carotid arteries above and below the stenosis.
- Clamping of internal carotid may significantly reduce cerebral perfusion
- Aim MAP greater than highest recorded awake level during clamping
  Consider ⩾20% above baseline to reduce POCD.
- Stimulation of carotid baroreceptors may lead to sudden haemodynamic instability
  Anticipate sudden ↓ HR or ↓ BP.
- Consider use of neuroprotective agents to achieve burst-suppression
- Evidence of impaired cerebral perfusion should be managed surgically with placement of a shunt
- Note total clamping time on record
Excision of atheroma
- Longitudinal excision along carotid
- Closure usually with patch
  Reduces risk of re-stenosis.
Emergence
- Avoid hypertension during extubation
- Deep extubation appropriate

Post-Operative

Stroke:

Major concern
Neurology should be assessed early

Hypertension:

Treat aggressively if SBP >160mmHg
- Hydralazine
- Labetalol
- Phentolamine
- Avoid GTN
  Headache and cerebral vasodilation is undesirable.
Multiple potential causes
- Disruption of baroreceptors
- Pain
- Bladder distension

Hypotension:

Disruption of baroreceptors

Neck haematoma:

Occurs in ~3% of patients post-operatively
- ↑ risk if poorly-controlled HTN
May lead to obstruction to VR and subsequent lymphoedema
May require emergency airway management

Vocal cord palsy:

Vagal nerve/recurrent laryngeal nerve palsy

Cerebral Hyperperfusion Syndrome:

Occurs in 1-3% of carotid surgery
Associated with:
- HTN
- ⩾80% stenosis
- Previous CVA
Occurs due to excessive flow through the now un-stenosed vessel
Cause of most ICH post-CEA
Presents as:
- Headache
- Focal seizures
- Impaired conscious state
- Up to 2 weeks post-operatively
  May occur in theatre or in recovery.
Unilateral cerebral oedema on CTB

References

Stoneham MD, Stamou D, Mason J. Regional anaesthesia for carotid endarterectomy. Br J Anaesth. 2015 Mar 1;114(3):372–83.