Clipping of Intracranial Aneurysm

Time: 3+ hours
Pain: Moderate
Position: Supine or head up, prone for posterior circulation lesions
Blood loss: May be substantial; G+H and crossmatch
Special Drugs

This covers factors unique to clipping of intracranial aneurysms. Factors relating to craniotomies in general are covered here.

Clipping of an intracranial aneurysm involves placing a spring clip across the aneurysmal neck to occlude it. Clipping is performed under GA. Approaches include:

Considerations

  • B
    • No coughing or movement is tolerated
      Dissection of vasculature and aneurysm are delicate.
      • Deep opioid analgesia with remifentanil
      • Deep muscle relaxation (TOF of 0)
  • C
    • Stable haemodynamics
      Avoid alterations in aneurysm transmural pressure critical to prevent re-bleeding.
      • Usually target 140-160mmHg; discuss with surgeon
      • Hypo- and hypertension can be disastrous
    • Consider two IV access sites:
      • One large volume line
      • One anaesthetic/remifentanil infusion line
    • Arterial line
    • Have a plan for:
      • Aneurysmal rupture
      • Management of temporary clipping
  • D
    • ICP control
      • Optimise CO2
      • Head up
      • Sodium
      • Vent EVD if in situ and appropriate
    • Cerebroprotective strategies may be required if a temporary clip is placed over a major vessel
      ↑ BP gently to at least that of pre-operative BP.
    • Vasospasm prophylaxis
    • Avoid N2O
  • E
    • Muscle relaxation
      Not technically required if using remifentanil, but paralysis recommended given the extreme requirement for immobility.
      • Aim ToF = 0
      • Consider relaxant infusion
        Cisatracurium reliable and will wear off adequately for extubation if ceased when skull replaced.

Preparation

  • Standard monitoring
  • Awake arterial line
  • Large venous access
  • Consider CVC
    For aspiration of gas in case of air embolism in patients in seated position.

Induction

  • Haemodynamic stability is vital
    Avoid ⩽ 10% change in SBP.
    • Propofol and remifentanil standard in most institutions

Intraoperative

Aneurysmal Rupture:

  • Call for help
  • Determine if the aneurysm is exposed or unexposed
  • Goals:
    • Keep ICP low
    • Balance maintaining CPP vs. exacerbating haemorrhage
      • Exposed aneurysm: Rapid reduction in BP to reduce bleeding to allow surgeon to clip quickly
      • Unexposed aneurysm: Induce a degree of hypotension
    • Requires urgent surgical control of source
    • Reverse heparin if in IR
  • Induce hypotension to reduce haemorrhage
    • Target:
      • SBP ⩽100mmHg if in IR
      • Aim SBP 60-80mmHg or adequate reduction of haemorrhage if in OT
    • Strategies
      Multiple options; will depend on severity of haemorrhage and what is currently running/drawn up/available. Some include:
      • Anaesthetic agents
        • Propofol
          Immediately available and intimately familiar, but may not be enough.
        • Remifentanil bolus (e.g. 1ug/kg)
        • Thiopentone
        • Volatile
      • Cardiac agents
        • Adenosine
        • Labetalol 5-10mg
        • Esmolol
        • GTN
          3-5mg/kg bolus, then 3-5mg/kg/hr, targeted to burst suppression.
      • Compress ipsilateral carotid artery to reduce bleeding
  • Volume resuscitation
    • ↑ IVT rate
    • Begin transfusion
  • Consider cerebroprotective strategies

Cerebroprotection:

  • May be requested if placing temporary clip on a major vessel
  • Goal is to maintain cerebral perfusion by collateral vessels
  • Gentle elevation in BP desirable

Surgical Stages

Haemodynamically critically points include:

  • Induction
  • Pins
  • Incision
  • Dural opening
  • Haematoma removal
  • Exposure and clipping
    • Dissection and exposure of aneurysm Delicate - ensure immobility.
    • Potential temporary clipping of vessels supplying aneurysm
      ↑ blood pressure to improve collateral circulation whilst temporary clip in situ.
      • ⩽15 minutes is well tolerated
      • ⩾30 minutes will have ischaemic injury
    • Clipping of aneurysm
      Multiple clips may be applied.
    • Potential aspiration of aneurysm
      To ensure that there is no further flow to the lesion.
  • Extubation

Postoperative

May require ICU care if:

  • Complicated intraoperative course
  • Vasospasm
  • Poor grade SAH prior

References