General anaesthesia

Question 1

What are the two main categories of anaesthesia?

Answer 1

General anaesthesia - making the patient unconscious

Regional anaesthesia - blocking feeling to an isolated area of the body

Question 2

Why do we fast the patient?

Answer 2

Reduce the risk of stomach contents refluxing into the oropharynx, then being aspirated into the trachea.

Question 3

What happens if gastric contents get into the airways during intubation?

Answer 3

Inflammatory response, causing pneumonitis.

Question 4

When is risk of aspiration highest?

Answer 4

Before and during intubation, and when they are being extubated

Question 5

Major causes of morbidity and mortality in anaesthetics

Answer 5

Aspiration pneumonia and pnuemonia

Question 6

How do you fast a patient?

Answer 6

• 6 hours no food or feeds before operation
• 2 hours no clear fluids (fully ‘nil by mouth’)

Question 7

What is preoxygenation?

Answer 7

Before being put under GA, the patient will breathe 100% oxygen for several minutes.

This gives them a reserve of oxygen for the period between losing consciousness and successful intubation and ventilation.

Question 8

What is premedication?

Answer 8

Meds given before the patient is put under GA to relax, reduce anxiety, reduce pain and make intubation easier.

These may include:
* Benzodiazepines - relax muscles and reduce anxiety (also causes amnesia)
* Opiates - reduce pain, reduce hypertensive response to laryngoscope
* Alpha-2-adrenergic agonists - help with sedation and pain

Question 9

What is RSI?

Answer 9

Rapid sequence induction/intubation

Gain control over airway asap in emergency scenario and detailed pre-planning is not possible.

Also used in non-emergency situations where the airway needs to be secured quickly to avoid aspiration, eg. patients with GORD or pregnancy.

Question 10

Triad of GA

Answer 10

• Hypnosis
• Muscle relaxation
• Analgesia

Question 11

Hypnotic agents and how are they given?

Answer 11

IV:
* Propofol (the most commonly used)
* Ketamine
* Thiopental sodium (less common)
* Etomidate (rarely used)

Inhaled options:
* Sevoflurane (most common)
* Desflurane (less favourable as bad for environment)
* Isoflurane (very rarely used)
* Nitrous oxide (combined with other anaesthetic meds - may be used for gas induction in kids)

Question 12

Volatile anaesthetic agents?

Answer 12

Sevoflurane
Desflurane
Isoflurane

Are all volatile agents, need to be vaporised into a gas to be inhaled.

Question 13

Common order of administration of anaesthetics?

Answer 13

Intravenous med first as induction agent (induce unconsciousness) and inhaled med used to maintain GA during the operation.

Question 14

What is TIVA?

Answer 14

Total intravenous anaesthesia

Involves using IV medication (most commonly propofol) for induction and maintenance - gives a nicer recovery (as they wake up) compared with inhaled options.

Question 15

What are the two categories of muscle relaxants?

Answer 15

• Depolarising (e.g. suxamethonium)
• Non-depolarising (e.g. rocuronium and atracurium)

Question 16

How to reverse the effects of muscle relaxants?

Answer 16

Cholinesterase inhibitors (e.g. neostigmine) can reverse the effects of neuromuscular blocking meds.

Sugammadex is used to reverse the effects of non-depolarising muscle relaxants (rocuronium and vecuronium).

Question 17

Commonly used opiates for analgesia?

Answer 17

• Fentanyl
  *.Alfentanil
• Remifentanil
• Morphine

Question 18

Common antiemetics given to prevent post-op N+V?

Answer 18

• Ondansetron - avoid in patients at risk of prolonged QT interval.
• Dexamethasone - used with caution in diabetic or immunocompromised patients.
• Cyclizine - caution with HF and elderly patients.

Question 19

What is ‘awareness under anaesthesia’?

Answer 19

Patient regains consciousness while still paralysed.

Question 20

Risks of GA?

Answer 20

Sore throat and post-op nausea and vomiting are common adverse affects of GA.

Significant risks:
* Accidental awareness (waking during the anaesthetic)
* Aspiration
* Dental injury, mainly when the laryngoscope is used for intubation.
* Anaphylaxis
* Cardiovascular events (e.g. MI, stroke and arrhythmias)
* Malignant hyperthermia (rare)
*Death

Question 21

What is malignant hyperthermia?

Answer 21

Rare but potentially fatal hypermetabolic response to anaesthesia. (Main risk with volatile anaesthetics and suxamethonium)

Malignant hyperthermia:
* Increased body temp
* Increased carbon dioxide production
* Tachycardia
* Muscle rigidity
* Acidosis
* Hyperkalaemia

Question 22

How do you treat malignant hyperthermia?

Answer 22

Dantrolene

Dantrolene interrupts the muscle rigidity and hyper metabolism by interfering with the movement of calcium ions in skeletal muscle.