Carotid endarterectomy:

 

Surgery:

Indications

·      TIA and >70% stenosis (NNT 6)

·      TIA and >50% stenosis (NNT 22)

·      Asymptomatic: unclear

·      Urgent procedure

Procedure

·      Dissection

·      Clamp (I -> C- > E) – ischaemic period

·      ±Shunt

o  High risk anatomy

o  Sign of intra-op ischaemia

·      Endarterectomy

·      ±Shunt removal – ischaemic period

·      Unclamping

·      Closure

 

Airway issues:

Shared airway

·      ETT tube

·      Secure on contralateral side with tape and teggies

·      Beware accidental removal during surgical positioning

Post-op obstruction

·      Haematoma -> venous outflow obstruction -> swelling -> stridor

·      High index of suspicion post-op

·      Rx: open stitches, expect difficult re-intubation

RLN injury

·      Dx: stridor, FNE

·      Rx: IPPV, ICU care

 

Cardiovascular issues:

Lability

Key moments:

·      Induction (↑BP)

·      Intubation (↑BP

·      Cross-clamp (↑BP

·      Carotid sinus manipulation (↓↓HR)

·      Extubation (↑BP)

·      Recovery (↑BP)

Mitigation:

·      ↓BP: fluid, metaraminol

·      ↑BP: remifentanil, antihypertensive

·      Vagus: atropine, local infiltration

Bleeding

·      Pre-op: group + hold, consent for transfusion

·      Intra-op: large IVC, A-line, warming

AMI

Problem:

·      Coronary artery disease very common

·      Intra-op haemodynamic instability

Mitigation:

·      Monitoring: 5-lead ECG + arterial line

·      Remifentanil (avoid ↑↑HR/↑↑BP -> ↑perfusion time, ↓workload)

·      Metaraminol (↑coronary perfusion pressure)

Hyperperfusion syndrome

·      Rare but 40% mortality

·      Due to impaired cerebral autoregulation on the operative side

·      Hypertension -> headache, bleeding, swelling, seizure

·      Onset in first few days

·      Rx: anti-hypertensive, stop antiplatelet, monitor in ICU

 

Neuro issues:

Ischaemic stroke

Risk factors:

·      Bilateral disease

·      Incomplete circle of Willis

↑Oxygen supply:

·      Arterial line with transducer at brainstem height

·      Metaraminol infusion

·      mAP during maintenance: within 20% of baseline

·      mAP during clamping: 20% above baseline

·      Hb >80

·      SpO2 100%

·      PaCO2 40-50mmHg (i.e. luxury perfusion)

↓Oxygen demand:

·      Propofol -> burst suppression / isoelectricity

·      Temp not high

(Additional neuroprotection: avoid ↓BSL)

Neuro-monitoring options:

·      Awake neuro exam (GCS, hand squeeze, speech esp. dominant side)

·      Electrical: EEG, BIS, SSEP

·      Perfusion: carotid stump pressure, transcranial doppler

·      Oximetry: NIRS, jugular venous bulb sats

NIRS in particular:

·      Bilateral electrodes, each with one optode and two detectors

·      Shallow signal subtracted, deep signal collected

·      Arterial and venous blood from frontal cortex

·      Normal 60-80%

·      Significant drop is 20%

Haemorrhagic stroke

·      Arterial line

·      Remifentanil

·      Antihypertensives

Embolic stroke

·      Patient and surgical factors

·      Major cause of peri-op stroke in CEA patients

·      Ensure aspirin started pre-op

Rapid emergence

·      Need rapid assessment of neuro status

·      Remifentanil to spare propofol

 

General anaesthetic:

Goals

·      No stroke

·      No AMI

·      No airway disaster

·      No haemorrhage

Pre-op

Assessment:

·      Status of brain vessels: TIA, % stenosis, contralateral disease)

·      Status of heart vessels: angina, 12 lead ECG, ±cardiology consult

Treatment:

·      Anti-platelet

·      Statin

·      Anti-hypertensive: withhold on the day

·      Beta blocker: continue if already taking, otherwise wait

Intra-op

Preparation:

·      Anaesthetic: GA vs block

·      Airway: ETT very well secured

·      Access: large PIVC, A-line on the visible side

·      Drugs: prop/remi/met + relaxant + antihypertensive + heparin

·      Monitoring: standard + A-line, temp, BIS

·      People: standard

Targets:

·      Keep mAP 20% above baseline during clamping

·      Keep CO2 normal

·      Keep O2 normal

·      Keep temp normal

Communication:

·      Clamping and unclamping

·      Carotid manipulation

·      Anticoagulation (ACT 250-300) / time since heparin

Post-op

·      PRN oxycodone

·      PRN anti-hypertensive (expect rebound)

·      Monitoring in PACU: ABP, ABG,ECG, neuro-obs

·      Disposition: ward vs HDU for BP control

 

Regional anesthetic:

Sedation

·      Propofol Cet 1mcg/mL

·      Remifentanil 0.025-0.05mcg/kg/min

·      Patient comfortable lying still

·      Easy to convert to GA

LA mix

·      20mL syringe

·      10mL 0.75% ropivacaine, 10mL 2% lignocaine with adrenaline

Superficial plexus block

·      Enter skin behind SCM

·      Pierce prevertebral fascia

·      5mL

Deep plexus block

(blind)

·      Draw line from mastoid to Chaissaignac tubercle (C6)

·      Mark C2,3,4,5,6 with pen

·      50mm, 25g needle

·      Enter skin posterior to SCM

·      Hit transverse process of C3,4,5

·      5mL per level

Complications

·      Vertebral artery injection -> seizure

·      Subarachnoid injection -> LOC

·      Horner syndrome

·      Blockade of phrenic, (vagus) recurrent laryngeal

·      Need for conversion to GA

 

GA vs LA:

LA > GA

Logistics:

·      Neuro exam possible

Medical:

·      EEG unaffected

·      Preserved CNS autoregulation

·      ↓AMI, CHF in-hospital

GA > LA

Logistics:

·      Motionless

·      Comfortable

·      Avoid risk of conversion

Medical:

·      Decreased CMRO2

GA = LA

At 30 days:

·      Stroke

·      AMI

·      Death

Note:

·      Selection bias: LA patients older, comorbid

·      BP manipulation bias: more in GA group

·      Impression is that LA is neurologically safer in high risk patients

·      LA allows for awake neuro monitoring = gold standard