Carotid Endarterectomy

Question 1

A 65-year-old male patient is listed for a carotid endarterectomy 8 days afer a transient ischaemic attack. He is a smoker with moderate COPD and hypertension and has a hiatus hernia.

What are the indications for a carotid endarterectomy following a cerebrovascular event?

Answer 1

• The NICE 2019 guidelines state that stable patients should undergo urgent imaging to determine the next course of treatment following a stroke or TIA.
• Two large randomised controlled trials were carried out looking at the degree of carotid artery stenosis and intervention:
• North American Symptomatic Carotid Endarterectomy Trial
  (NASCET) – criteria determined that patients with 50%–99% stenosis should be considered for surgery.
• European Carotid Surgery Trial (ECST) – criteria suggested that
  patients with 70%–99% stenosis should be considered for surgery.
• The criteria used should be specified when the decision is made.

Question 2

What is a carotid endarterectomy?

Answer 2

• A procedure that enables removal of atheromatous plaque from the carotid artery.
• It involves dissection of the carotid artery following cross clamping above and below the affected area.

Question 3

How would you assess this patient preoperatively?

Answer 3

Patients suitable for this procedure benefit from surgery within 2 weeks of the onset of symptoms.

History:
* Take a full medical history focusing on cardiovascular and respiratory comorbidities and the risk factors for an anaesthetic and further cerebrovascular events.

• Determine the severity and any current symptoms of COPD, including the ability to lie flat and remain still for a prolonged period of time, as a regional anaesthetic technique may be an option.
• These patients are likely to have disease present in other organs; have a high suspicion for undiagnosed ischaemic heart disease and renal insufficiency.
• Explore any symptoms or further episodes since the primary TIA.
• Take a full drug and social history, including control with existing agents.
• Ask about previous anaesthetics and airway assessment.

Question 4

How would you assess this patient preoperatively?

Continued…

Answer 4

Examination:
* Cardiovascular and respiratory examination.

• Airway examination.
• Any neurological deficits due to the previous cerebrovascular event
  should be clearly documented to enable accurate postoperative monitoring.

Investigations:
* Note the oxygen saturation at rest and non-invasive blood pressure. The patient’s normal blood pressure should be clearly documented.

• Baseline blood tests: full blood count, urea and electrolytes and clotting.
• The severity of the patient’s comorbidities may dictate the need for further investigations such as an echocardiogram, pulmonary function tests and CPET.

Question 5

What are the options for cerebral monitoring perioperatively?

Answer 5

• An awake patient enables continuous sensory and motor function testing throughout the procedure.
• Cerebral oximetry can be used to monitor brain perfusion.
• A transcranial Doppler probe measures blood flow in the middle cerebral artery.
• Stump pressures can detect cerebral perfusion pressure.
• Electroencephalogram (waveform changes may indicate ischaemia).
• Somatosensory-evoked potentials.
• Near-infrared spectroscopy gives an indication of changes in cerebral
  oxygenation.

Question 6

What is the indication for a shunt?

Answer 6

• Cross clamping of the carotid artery relies on blood flow through the contralateral carotid artery and Circle of Willis to maintain cerebral perfusion. The restriction of flow in that artery may suggest the need for a shunt.
• A shunt can be inserted to bypass the area that has been cross-clamped if there are concerns about poor cerebral perfusion. However, the benefits of a shunt need to be weighed up against the potential risks e.g. air embolism and thrombus formation.

Question 7

What are the options and benefits of a regional anaesthetic technique in this patient?

Answer 7

• The options for a regional anaesthetic in this patient are:
• Local infiltration (usually inadequate).
• Superficial cervical plexus block.
• Deep cervical plexus block.
• A combination of the three techniques above (most common).
• Cervical epidural (rarely done in the UK).
• Benefits of a regional technique in this patient are:
• Allows gold standard monitoring of neurological function and cerebral blood flow perioperatively (assuming awake patient).
• Avoids the risks of a general anaesthetic in a high-risk patient.
• Reduced requirement for a shunt as the patient can be monitored throughout.
• Shorter recovery time and stay in hospital, leading to reduced postoperative complications.
• Avoidance of haemodynamic instability secondary to
  administration of anaesthetic agents, reducing the risk of further cerebrovascular events.

*It should be noted that the GALA study did not demonstrate a survival benefit with regional anaesthesia over a general anaesthetic.

Question 8

What is hyperperfusion syndrome?

Answer 8

• A collection of symptoms that may occur following a carotid endarterectomy due to a sudden increase in blood flow to that side of the brain, including an ipsilateral headache and seizures.
• It can lead to focal neurological deficits and intracranial haemorrhage.
• The patient’s blood pressure must be very closely monitored and maintained within a defined range to prevent patients developing
  hyperperfusion syndrome following this procedure.