Anaesthetics - Introduction to anaesthesia 1

Question 1

What is the difference between anaesthesia and sleep?

Answer 1

When patients are anaesthetised they are not asleep but they are unconscious. Patients who are asleep can move, respond to main, swallow (prevents pharyngeal secretions) and maintain there own airway.

Anaesthetised patients do not. Importantly, they cannot respond to pain (although may develop a tacchycardia or move slightly if under light anaesthesia) and cannot maintain there own airway.

Neither are anaesthetised patients hypnotised.

Question 2

What are the 3 components of general anaesthesia?

Answer 2

1) Need to provide sleep (!), hypnosis or a state of unawareness
2) Need to prevent movement (muscular relaxation) which could interfere with surgery
3) Need to obtund painful stimuli (analgesia)*
* Pain is a conscious sensation (requires both a sensory input and emotion) so strictly speaking anaesthetised patients do not feel pain because they are unconscious. But they can still respond to noxious stimuli so analgesia is given to prevent this.

Question 3

What is a “balanced” anaesthesia?

Answer 3

Achieving the components of anaesthesia can either be done using:
i) Large dose of IV or inhalational anaesthetic, or

ii) A combination of drugs ( = an anaesthetic at a much lower dose + analgesia +/- muscle relaxant) - this is balanced anaesthesia

Question 4

What are the advantages/ disadvantages of single agent anaesthesia?

Answer 4

• simple: only one agent and therefore one delivery system required
• respiratory and cardiac depression: due to large doses of agents required to produce muscle relaxation
• death: most likely due to profound cardio-respiratory depression
• can be used for short procedures - e.g. #wrist resetting

Question 5

Summarise the different types of anaesthesia?

Answer 5

Anaesthesia can be delivered as i) local, ii) regional or iii) general.

i) Local - topical (e.g. emla cream), or infiltration (e.g. subcutaneous injection for dental procedures)
ii) Regional - peripheral nerve block, epidural, spinal or intravenous regional (Bayer’s block)
iii) General - single agent anaesthesia or balanced anaesthesia, both of which can be given by inhalation or total intravenous anaesthesia (TIVA)*
* The important thing to remember about GA is that it can be induced by intravenous or inhalational agents, it can be maintained by intravenous or inhalational agents, they can be combined with other drugs as part of a balanced anaesthesia and with the patient breathing spontaneously or with ventilatory support