FRCA Notes

Thrombotic Ischaemic Stroke & Endovascular Thrombectomy

This topic was an SAQ in March 2019 (63% pass rate), with overall positive feedback from the examiners.

Resources

  • Stroke is the third leading cause of disability and mortality in the developed world; two-thirds of patients leave hospital with a disability

  • Acute, ischaemic stroke accounts for 85% of all cases
    • A critical reduction in blood flow results in ischaemia and cell death
    • The surrounding tissue (penumbra) is salvageable for several hours and therefore prompt restoration of blood flow is crucial
  • The remaining 15% is haemorrhagic e.g. intra-cerebral or sub-arachnoid haemorrhage

  • Historically the only option for reperfusion was IV thrombolysis
    • Only 10 - 40% of patients with large vessel occlusion and anterior circulation stroke will achieve good clinical outcome following IV thrombolysis
    • The efficacy of mechanical clot retrieval in this patient group is now established

National Institute of Health Stroke Scale (NIHSS) Score

  • Measures severity of stroke by scoring: level of consciousness, vision, sensation, movement, speech, language
Score Grade
0 No stroke
5-15 Moderate stroke
16-20 Moderate-severe stroke
21-42 Severe stroke

Modified Rankin Scale (mRS)

  • Measures degree of disability
Grade Description
0 No symptoms
1 No significant disability
2 Slight disability; independent but unable to carry out all previous activities
3 Moderate disability; walks independently but requires help with ADL's
4 Moderate-severe disability; not independent with ADLs
5 Severe disability; full-time nursing care
6 Death


  • Mechanical/endovascular thrombectomy aims to provide rapid recanalization of occluded large cerebral arteries
  • Multiple trials have found positive findings for anterior circulation EVT
  • Pooled data demonstrates the NNT to reduce mRS score by one level is 2.6

    • Inclusion criteria for EVT
    Patients with anterior circulation stroke of any age
    Presentation within 6hrs of symptom onset (anterior, inc wake up stroke), up to 24hrs if evidence of salvageable brain for ant and post strokes
    IV thrombolysis contra-indicated or inadequate response
    Proximal(large or medium) vessel occlusion: internal carotid or MCA segments M1 or M2
    No new ischaemic changes on CT/MRI brain
    NIHSS >5
    Previously independent ADLs i.e. mRS 0-2

  • The benefit of EVT diminishes with increasing time interval between onset and intervention
  • Beyond 6hrs the impact of intervention is less certain
  • Studies are still required to determine whether all patients with delayed presentation require advanced imaging and whether they may benefit from EVT

Pre-hospital

  • Increased public awareness of symptoms through education
  • Pre-hospital triage systems and regional stroke networks
    • Enable prompt patient assessment and stabilisation
    • Patients are delivered to units best able to provide appropriate specialist care
    • Hospitals should be pre-alerted to allow mobilisation of resources in time for arrival

In-hospital

  • Initial emergency department care should include:
    • Rapid assessment to establish time since stroke onset
    • Neurological evaluation with NIHSS
    • Baseline investigations:
      • Bloods: FBC, U&E, clotting, troponin (prognostication)
      • ECG
      • Rapid non-contrast CT scan, within 20mins of arrival in hospital
        • Exclude intracranial haemorrhage, tumour or other pathology which would preclude thrombolysis
        • ± Concurrent CT angiography

  • Thrombolysis should be administered ASAP in those for whom it is appropriate, and within 4.5hrs e.g. alteplase 0.9mg/kg

Transfer to EVT centre

  • Those who may benefit from EVT should be urgently transferred to closest centre, following discussion between stroke consultants and neuro-interventionalists
  • This model ('drip and ship') may be inferior in the long-term to a model whereby all patients are directly transferred to specialist centre ('mothership')

  • Patients undergo assessment by anaesthetic, neurology/stroke and neuroradiology teams to establish need for further investigations and optimal anaesthetic
  • Time is naturally crucial and there may not be time for further tests or detailed assessment

Performance of EVT

  • Typically femoral artery access and guide-catheter insertion into carotid artery
  • Clot retrieval is via stent retriever or alternative devices, the choice of which will depend on individual anatomy and pathology
  • Some interventionalists will use heparin to minimise risk of catheter-related embolism
  • Reperfusion is assessed using the mTICI grading system

Perioperative management of the patient undergoing endovascular thrombectomy


  • The key factor pre-operatively is to avoid unnecessary delay
  • Historical concern about the effect of GA on outcome persists, owing to the results of retrospective reviews of methodologically imperfect observational studies
  • Data from the recent GASS trial (2022) suggests no outcome diffference between GA or sedation
  • Consensus guidelines recommend an individualised approach based on patient factors, procedural performance and other clinical characteristics

Advantages Disadvantages
Airway protection with ETT Hypotension exacerbating ischaemic injury
Manipulation of ETCO2 & other physiology Inability to monitor neurological status intra-procedurally
Patient immobility reduces procedural injury risk Delays initiation of procedure (marginally)
↑ recanalisation rates Increased rate of POPC but no effect on morbidity/mortality
↑ functional recovery
↓ technical failure rate
↓ rate of arterial complications


Monitoring and access

  • AAGBI
  • Invasive arterial monitoring for those receiving GA due to higher frequency of haemodynamic instability
  • Extensions on tubing and lines due to limited patient access
  • Urinary catheterisation ideally, but this should not delay intervention and in-out catheter at the end may suffice

Conscious sedation

  • Short-acting agents with analgesic properties are recommended
  • Examples:
    • Remifentanil TCI ± propofol
    • Fentanyl boluses during painful phases including groin puncture, contrast injection and clot retrieval + midazolam sedation
    • Dexmedetomidine

General anaesthesia

  • GA is recommended in patients for whom conscious sedation is inappropriate or where conversion to GA may be suspected:
    • Agitation
    • Reduced GCS
    • Nausea/vomiting
    • Complicated anatomy
    • Large, dominant hemisphere strokes
    • Posterior circulation stroke

  • Patients should be intubated ± RSI technique
  • Propofol/remifentanil TCI or sevoflurane inhalational anaesthesia are equally viable maintenance techniques
  • Early extubation to facilitate neurological assessment

Physiological targets

  • Maintenance of normal physiology is important for patient outcome

  • Blood pressure
    • Consensus guidelines suggest an SBP target of 140 - 180mmHg
    • Maintenance of MAP within 10% of baseline or >70mmHg may be an equally appropriate target
    • Balance hyer- and hypo-tension with:
      • Metaraminol infusion
      • Labetalol infusion (neat 5mg/ml in 20ml syringe); start at 10mls/hr
    • A BP drop >10% for 10mins is associated with poorer prognosis
    • Be wary of GTN patches or nimodipine which may have been used by Stroke or IR teams to aid vascular access

  • Oxygenation: maintain SpO2 94 - 98%, with no role for hyperoxia
  • Ventilation: maintain PCO2 4.5 - 5.0kPa if mechanically ventilated
  • Normoglycaemia: 7 - 10mmol/L
  • Normothermia: no evidence of benefit for cooling in EVT

Haemodynamics

  • Ongoing neurological and haemodynamic monitoring is required
  • Blood pressure control should be maintained, with a target of <180/105mmHg
    • This may required agents such as labetalol, nicardipine or sodium nitroprusside
    • Resumption of pre-existing antihypertensive therapy after 48hrs may aid this

Analgesia

  • Pain is usually minor; headache or pain at groin puncture site
  • Paracetamol is safe and usually adequate
  • NSAIDs should be avoided owing to the increased risk of bleeding at the groin puncture site, intracranially or via haemorrhagic transformation
  • Opioids must be used with caution owing to:
    • Their ability to cloud neuromonitoring post-operatively
    • Hypoventilation-induced hypercapnoea affecting CBF

Homeostasis

  • Normothermia
  • Normoglycaemia
  • Neutral fluid balance
  • Electrolyte control to reduce risk of AF
  • Avoid NG tube if recent thrombolysis
  • NBM pending SALT assessment
  • Mechanical-only VTE prophylaxis initially
  • Antiplatelets after 24hrs

Disposition

  • Either to the hyperacute stroke unit (HASU), or critical care if they were I&V on arrival or have suffered complications

  • Incidence of complications can be reduced if EVT is only performed in units with high case volume (>200/yr) and regular assessment/audit of outcomes

Haemorrhagic

  • Intracranial haemorrhage (up to 10%)
    • May be device-related or occur spontaneously
    • Requires reversal of heparin with protamine
  • Puncture-site haemorrhage
  • Retroperitoneal haemorrhage (rare)

Device-associated

  • Intracranial haemorrhage (although newer devices have superior rates of device-related arterial injury)
  • Vessel dissection, requiring use of DAPT/anticoagulants
  • Vasospasm
  • Catheter-associated thromboembolism

Other

  • Orolingual angioedema (5%)
  • Contrast allergy
  • Contrast nephropathy
  • Puncture-site infection
  • Pseudoaneurysm formation