Anaesthetics

Question 1

What are the 2 main types of anaesthesia?

Answer 1

General

Local

Question 2

What is conscious sedation?

Answer 2

When small amounts of anaesthetic are used to produce a ‘sleep-like’ state and make the patient feel comfortable, but the patient is still awake and conscious.

Question 3

What is Guedel’s signs? What 3 factors are the stages based on?

Answer 3

Describes the 4 stages of anaesthesia based on:

• muscle tone
• breathing
• eye movement

Question 4

Which stage of Guedel’s signs is surgery usually started at?

Answer 4

Stage 3 - muscle tone is relaxed and breathing is steady.

Question 5

What is Minimum Alveolar Concentration (MAC)?

Answer 5

The concentration of vapour in the alveoli that is needed to prevent movement in 50% of subjects in response to surgical stimulus.

Question 6

What is the relationship between MAC, potency and side effects?

Answer 6

The lower the MAC, the more potent that anaesthetic and the fewer side effects there are as less of the drug is required.

Question 7

Name some factors affecting MAC, and say for each whether they increase or decrease MAC.

Answer 7

• age (increased in infants, decreased in elderly)
• hyperthermia (increased) and hypothermia (decreased)
• pregnancy (increased)
• alcoholism (increased)
• other anaesthetics and sedatives (decreased)

Question 8

What is the effect of nitrous oxide on MAC?

Answer 8

Nitrous oxide reduces the MAC, meaning you need less of the anaesthetic and therefore have fewer side effects.

Question 9

What is induction?

Answer 9

Puts the patient to sleep, can be IV or inhalation.

Question 10

Name 2 factors affecting induction and recovery.

Answer 10

• solubility of gas in fat - obese people have a slower induction and recovery as the anaesthetic accumulates in fat
• solubility of gas in the blood - a low solubility coefficient means a faster induction and recovery as the anaesthetic wants to leave the blood quicker

Question 11

Apart from Xe, N20 and ketamine, what is the MOA of anaesthetics?

Answer 11

Bind to and activate GABA receptors (ligand-gated Cl- ion channels), which blocks excitation.

Question 12

Name 3 local anaesthetics

Answer 12

Lidocaine
Bupivacaine
Ropivacaine

Question 13

What is the MOA of local anaesthetics?

Answer 13

Block Na+ channels, which blocks pain transmission.

Question 14

What is bupivacaine used for?

Answer 14

Local anaesthetic often used for wound analgesia.

Question 15

Name some factors that make local anaesthetics very effective.

Answer 15

• high potency - lower dose needed
• low pKa = low dissociation constant = faster onset
• high protein binding - lasts for longer

Question 16

What is regional anaesthesia?

Answer 16

A type of local anaesthesia where local anaesthetic is put into a nerve root, selectively anaesthetising part of the body.
Patient remains awake
E.g. Epidural

Question 17

Name some side effects of general anaesthesia.

Answer 17

• PONV (post-operative nausea + vomiting)
• POCD (post-operative cognitive decline)
• chest infection

Question 18

Name some side effects of local anaesthesia.

Answer 18

-cardiovascular toxicity (because locals are Na+ channel blockers)