Aneurysm Clipping

Question 1

A 59-year-old female patient is undergoing an elective craniotomy for clipping of an aneurysm. She has severe COPD and a permanent pacemaker in situ. Her current medication includes captopril, tiotropium, salbutamol and simvastatin.
What added information would you like prior to this case?

Answer 1

1) Patient factors

2) Surgical factors

3) Anaesthetic factors

Question 2

Patient factors?

Answer 2

• A full and thorough anaesthetic history focusing on the patient’s known cardiovascular and respiratory comorbidities, any previous anaesthetics and an airway assessment.
• A focused pacemaker history, to include the reason for and date of insertion, the date of the most recent check and any malfunction, the pacemaker mode and how dependent the patient is on the pacemaker.
• A baseline neurological examination checking for signs of raised intracranial pressure (fluctuating GCS, headache, vomiting and visual changes), gross focal neurological signs and any symptoms of hydrocephalus.

Question 3

Surgical factors?

Answer 3

• The patient’s position during the procedure.
• The likelihood of diathermy use perioperatively, taking into account the permanent pacemaker.
• The urgency and likely duration of the procedure.
• Consideration of alternative procedures given the comorbid state
  of the patient - radiological coiling is minimally invasive; hence, there would be a decreased requirement for opioid analgesia and its associated side effects.

Question 4

Anaesthetic factors?

Answer 4

• This is a patient with numerous comorbidities undergoing a major operation. Te case should be supervised by a consultant neuroanaesthetist.
• Discuss the patient with the neurocritical care unit for the availability of postoperative level 2/3 care.

Question 5

Which of her medication, if any, would you stop prior to surgery?

Answer 5

• Continue nimodipine, inhalers and simvastatin.
• Omit captopril on the morning of surgery; administration of ACE
  inhibitors can cause signifcant uncontrollable intraoperative hypotension.

Question 6

What are the anaesthetic goals in this case?

Answer 6

• Maintenance of cerebral perfusion and gas exchange.
• Maintenance of haemodynamic stability, in particular avoiding the
  pressor response to laryngoscopy.
• Rapid postoperative emergence with good analgesia and prevention
  of coughing/vomiting.
• Reducing the risk of complications specific to neurosurgery e.g. air
  embolism.

Question 7

Which anaesthetic agent(s) would you use to anaesthetise this patient?
1) TIVA anaesthetic

Answer 7

TIVA anaesthetic

• Use the Marsh or Schneider model with propofol and the Minto model with remifentanil.
• Ensure appropriate effect site concentrations of the drugs in use.
• The concentrations should be titrated to overcome the hypertensive response to stimuli e.g. during the application of Mayfeld pins.

Question 8

2) Volatile agents

Answer 8

Volatile agents

• Induction with appropriate doses of propofol and fentanyl.
• Maintenance of anaesthesia with sevoflurane (note that sevoflurane uncouples the cerebral blood flow and cerebral metabolic rate of oxygen).
• Avoid nitrous oxide (can worsen pneumocephalus postoperatively).
• Control the hypertensive response to stimuli using an opioid (alfentanil bolus, remifentanil infusion) and/or a short-acting beta
  blocker (esmolol infusion).

Question 9

If using a TIVA method, what features are important for safety?

Answer 9

• Ensure adequate training and competence of the anaesthetist.
• Use a TCI-specific infusion pump that has been checked and serviced.
• Ensure that the pump alarms are enabled to alert the anaesthetist to high pressures and an empty syringe.
• Consider two person checking of the drugs.
• Use Luer-lock connectors and anti-syphon valves.
• Ensure that there is a visible cannula during the procedure. A crystalloid solution can be used to maintain patency perioperatively (0.9% saline).

Question 10

The surgeon states that the brain appears tight and swollen intra-operatively. What is your immediate management?

Answer 10

• Raise the patient to a head-up position if possible.
• Optimise the cerebral blood flow by adjusting the PaCO2 to allow-normal range and ensuring normoxia.
• Judicious use of mannitol 0.5–1 g/kg (or hypertonic saline, as long as serum sodium adjustment occurs at a safe rate) after a discussion
  with the surgeon.
• Re-assess the patient using an ABCDE approach and facilitate further
  procedures or treatment as directed by the surgical team.