202410052227

Status:

Tags: vascular

Carotid endarterectomy

The risk of disabling stroke or death is highest in the immediate period following the initial TIA. The current National Stroke Service Model endorsed by the NICE recommends urgent surgery within 7 days of symptom onset, posing challenges for preoperative assessment, optimization and service delivery

Surgery is beneficial in reducing five-year stroke risk and death with a stenosis >50%
This benefit is more marked in those with a higher degree of stenosis (70–99%)

Carotid stenting is currently performed in some centres as an alternative to open endarterectomy and is useful if surgical access is an issue, e.g.

Major trials

ECST (European Carotid Surgery Trial)
NASCET (North American Symptomatic Carotid Endarterectomy Trial)
ECST-2:

GALA

Pre-op

Due to the urgency of surgery, time is often limited but common comorbidities associated with stroke/TIA should be optimized as far as possible

2% of CEA have a peri-op CVA

Hypertension

Acute antiplatelet therapy consists of 300 mg aspirin for 2 weeks from presentation before switching to clopidogrel or alternative antiplatelet agent for secondary prevention. This should be continued through the perioperative period as stroke risk is usually higher than bleeding risk

High-dose statin therapy is also started acutely and is shown to lower stroke and cardiovascular risk perioperatively

Preoperative neurological assessment should be documented to aid recognition of postoperative changes in neurological function suggesting a cerebrovascular event

Intra-op

Heparin 3000–5000 units is given prior to clamping above the stenosis

internal carotid is clamped first to prevent distal emboli before the arteriotomy and removal of atheromatous plaque (endarterectomy)

Clamping causes a transient ↑ BP due to the effect on carotid baroreceptors but this is ablated by general anaesthesia.

The main risk of surgery is postoperative stroke
A proportion of awake patients will develop a transient neurological dysfunction during clamping

LA vs GA

The main advantage with RA is real-time neurological monitoring but if deep sedation is required for patient comfort this advantage is negated.

patient factor

Advantages Disadvantages
General anaesthesia Control of airway and ventilation No intraoperative and delayed postoperative neurological monitoring
Immobility Intraoperative hypotension
Patient comfort Postoperative hypertension
Regional anaesthesia Continuous neurological monitoring Patient anxiety and cooperation and risk of conversion to general anaesthesia
Preservation of cerebral autoregulation Reduced access to airway
Early recognition of cardiac ischaemia Complications of block – failure, haematoma, intravascular/subarachnoid/epidural injection, phrenic nerve palsy
Reduced use of shunt
GALA trial

GA

GA requires invasive BP pre-induction as hypotension/hypertension from induction and laryngoscopy is common plus 5-lead ECG monitoring, SpO2, capnography and temperature as a minimum

Intubation with controlled ventilation enables control of PaCO2 and its effects on cerebral blood flow

MAP should be kept within 10–20% of baseline, especially during cross-clamping when cerebral blood flow is dependent on collateral circulation

The aim is smooth emergence to

RA

The most common blocks used are the superficial or intermediate Cervical plexus block

Deep cervical plexus block has been used in the past but has a higher risk of potential complications due to intrathecal injection and its proximity to the vertebral arteries running through the transverse processes.
It blocks motor nerves but has no benefit over superficial cervical plexus block in blocking the sensory nerves

Cervical epidural is theoretically possible but is not commonly used

Rescue LA infiltration into the dissection layers or around the carotid sheath can be given by the surgeon.

Patients undergoing RA still require invasive BP, 5-lead ECG plus routine monitoring including capnography face mask if sedation is to be given

The patient needs to remain still for the 2–3 hour procedure in the beach chair position which may require sedation. However, quality of neurological assessment should not be impaired by this, or the benefit of a RA technique is lost.

Technique & consideration

Good IV (one large bore usually suffice)

usually head up / beach chair position → implication on BP

Wrist restraint (surgical side)

Bair hugger standby
too warm → ↑CMRO2
too cold → shiver → ↑myocardial O2 consumption

Fire risk

Sedation:
small, titratable doses of a reversible (or short acting) agent

A line

for beat-to-beat variability
freq blood gas & Hcue assessment
evaluate SVV

Anticoagulation

heparin usually 80mg/kg
target ACT 200-250s

NOT reversed after carotid artery stenting

Sudden brady

∵ stimulation of carotid sinus baroreceptor

  1. pause OT
  2. atropine / glycopyrrolate
    • (+) surgeon infiltrate carotid
  3. (chest compression)
  4. (transcutaneous pacing)

Ischaemia monitoring

Method of monitoring Technique Limitations
Stump pressure After common and external carotid clamping, pressure in internal carotid is measured and relates to pressure across circle of Willis from contralateral circulation Anaesthetic agents affect cerebral vasculature
Electroencephalogram (EEG)/Bispectral index Certain characteristic EEG patterns can be associated with cerebral ischaemia Full EEG interpretation requires expertise
Abrupt fall in BIS value after clamping may indicate vulnerability to ischaemia Lacks sensitivity (especially in subcortical ischaemia) and specificity
BIS threshold not known
Near infrared spectroscopy (NIRS) Non-invasive regional tissue O2 monitoring by measuring difference in infrared absorption between oxygenated and deoxygenated Hb Parietal lobe ischaemia missed as sensors are frontal

Low positive predictive value
Transcranial Doppler (TCD) Ultrasound Doppler used to evaluate flow in large cerebral vessels dynamically in real time Operator dependent

Acoustic window not found in 10–20% of patients
Somatosensory evoked potentials (SSEPs) Electrical activity measured over sensory cortex in response to stimulation of a peripheral nerve Affected by volatile anaesthetic agents

Extra equipment and expertise required

Documentation is important on how you react to the changes noted on monitor

EEG:

if Δ after clamp

cerebral oximetry

if ↓

Carotid shunt

Shunting across the clamped section of artery during GA has been shown in a Cochrane meta-analysis to ↓ stroke-related death within 30 days of surgery and ↓ stroke within 24 hours of surgery. However, evidence is of low quality and there remains a variation in practice between surgeons about when shunts are used

problems

The artery is usually reconstructed with a synthetic or autologous vein patch.

Carotid body denervation

Post-op

Haemodynamics

BP control is a major Postoperative issue due to

↓BP

∵ carotid sinus baroreceptor now "seeing" the pressure and responding
happening towards the end → have pressor ready

↑BP

if surgeons have infiltrated the carotid sinus
if BP ↑ >25% → control it to avoid hyperperfusion syndrome

Cerebral hyperperfusion syndrome

Areas of brain previously under perfused are subjected to high flow due to removal of the stenosis and hypertension and there is ischaemia–reperfusion injury

commonly p/w

leads to intracerebral haemorrhage / cerebral oedema

may occur wks later

Δ in mental status

ask surgeon to come
DDx:

Pain

LA infiltration by surgeon
panadol + small titrated dose of opioid
usually avoid NSAID ∵ risk of plt dysfunction & AKI

References

Regional Anesthesia for Carotid Endarterectomy by Jonathan Markley DO (youtube.com)

146. Carotid Endarterectomy

Anaesthesia for Carotid Surgery - A&ICM

Anesthesia for Carotid Endarterectomy, Angioplasty, and Stent