Epilepsy

Question 1

A 26-year-old male patient is listed for shoulder surgery following an injury while playing cricket last year. He has a history of epilepsy. You are asked to review him prior to his procedure.

What is epilepsy

Answer 1

• A neurological condition caused by excessive or abnormal electrical activity in the brain.
• This leads to a spectrum of symptoms including a predisposition to behavioural changes and seizures.
• Epilepsy is diagnosed following two separate episodes of seizure activity.
• It is classified according to the cause and type of seizures:
• Focal (simple or complex).
• Generalised (absence, tonic-clonic, myoclonic or atonic).
• Mixed.

Question 2

How would you assess this patient?

1) History

Answer 2

• Take a full history including any cardiovascular and respiratory comorbidities, regular medication and allergies and a social history.
• Ask the patient about any previous anaesthetics.
• Take a focused history regarding the diagnosis of epilepsy, to include:
• The date of diagnosis.
• The cause of epilepsy, if known.
• Any previous and current treatment (including the timing of doses).
• Seizure frequency and type.
• Known seizure triggers.
• Comorbidities secondary to the diagnosis or treatment.

Question 3

How would you assess this patient?

2) Examination
3) Investigations

Answer 3

Examination

• Routine examinations including an airway assessment. Specific examinations would not usually be indicated unless there was an obvious reason noted from the history.

Investigations
* Baseline observations.
* Anti-epileptic medication levels only if poor compliance with treatment is suspected or a prolonged procedure/inpatient stay is expected.
* Further blood tests or investigations should be guided by the history and examination and would not usually be necessary for routine
day-case surgery.

Question 4

What are the key concerns when anaesthetising this patient?

Answer 4

1) Adequate anti-epileptic medication levels:

• Continue regular anti-epileptic medication during the peri-operative period, factoring in timings for each dose.
• Avoid prolonged fasting.
• Minimise peri-operative nausea and vomiting.

2) Minimising risk of seizures:

• Avoid drugs that decrease the seizure threshold.
• Ensure optimal oxygenation and avoid hypocapnia, which may
  provoke seizures.
• Plan peri-operative analgesia, discussing with the surgical team.

3) Awareness of drug interactions:

• Some anti-epileptic drugs act as enzyme inducers or inhibitors, which needs to be taken into account when choosing anaesthetic and analgesic agents.

Question 5

Which commonly used agents should be avoided in patients with epilepsy?

Answer 5

• Enfurane has been associated with abnormal EEG activity, but is not commonly used in the UK.
• Methohexitone may provoke seizures, but is not used in the UK.
• Dopamine receptor antagonists e.g. metoclopramide can cause dystonia and may mimic seizures, thus introducing diagnostic
  challenges postoperatively and should be avoided.
• Alfentantil, tramadol and pethidine increase EEG brain activity and
  lower the seizure threshold.

Question 6

During the procedure, the surgeon notes a sudden increase in muscle tone, which is associated with a heart rate of 145 and a blood pressure of 189/101. How do you proceed?

Answer 6

• This may be seizure activity under general anaesthetic. Alert the theatre team, call for urgent help and conduct a rapid ABCDE assessment to determine the cause of the patient’s symptoms and rule out other potential causes.
• Apply 100% oxygen and manually ventilate the patient to assess compliance. Ensure that the patient has a normal-high end tidal carbon dioxide level.
• Check and correct electrolyte levels, acid–base balance, temperature and glucose (an arterial blood gas would be prudent when possible).
• Ensure adequate anaesthesia, muscle relaxation and analgesia.
• If the suspected seizure activity does not terminate, consider benzodiazepines, phenytoin or other anti-convulsants, noting what the patient has already taken preoperatively. Escalate to specialist care
  for further advice.
• Once the patient is stable, have a discussion with the surgeons
  regarding the expected duration of the procedure and the plan for postoperative care.