16) Anaesthetics

Question 1

Describe general anaesthetic:

Answer 1

IV, inhalational or volatile

Affects the whole body - patient unconscious

Question 2

Describe regional anaesthetic:

Answer 2

Involves rendering larger, specific regions of the body insensate, patient conscious

Question 3

Describe local anaesthetic:

Answer 3

More defined, peripheral nerve block

Question 4

What is conscious sedation?

Answer 4

Use of small amounts of anaesthetic or benzodiazepines to produce a sleepy like state

Question 5

Describe the main stages of anaesthetic procedure over the course of a surgery:

Answer 5

Pre-medication 
Induction 
Intra-operative analgesia
Muscle paralysis to facilitate intubation or ventilation 
Reversal and recovery

Question 6

What are some examples of volatile anaesthetics?

Answer 6

N20, chloroform, fluranes, xenon

Question 7

What are some examples of IV anaesthetics?

Answer 7

Propofol, barbiturates, etomidate, ketamine

Question 8

What are Guedel’s signs (stages of anaesthesia)?

Answer 8

Stage 1: analgesia
Stage 2: unconscious, breathing erratic, increased muscle tone
Stage 3: surgical anaesthesia - decreasing muscle tone and breathing
Stage 4: respiratory paralysis

Question 9

What are the main effects of anaesthesia?

Answer 9

Analgesia
Hypnosis
Muscle relaxation

Question 10

How is the potency of volatile anaesthetics described?

Answer 10

Minimum alveolar concentration

Question 11

What is the MAC (minimum alveolar concentration)?

Answer 11

Alveolar concentration at which 50% of subjects fail to move to surgical stimulus

Question 12

How does the MAC relate to potency?

Answer 12

Lower the MAC, the more potent the inhaled anaesthetic

Question 13

What is the absorption of an anaesthetic determined by?

Answer 13

Blood:gas co-efficient (water solubility)

Question 14

What does the lipid solubility of the anaesthetic determine?

Answer 14

Potency (greater lipid solubility = greater potency

Question 15

What factors can affect the MAC?

Answer 15

Age (lower in elderly)
Pregnancy (increased)
Central stimulants (increased)
Opioids (decreased)
Hyperthermia (increased|)
Alcoholism (increased)

Question 16

What are some receptor targets of anaesthetics?

Answer 16

GABAa receptors

NMDA receptors

Question 17

What anaesthetics don’t potentiate GABAa receptors?

Answer 17

Xenon, N2O, ketamine

Question 18

What effects do anaesthetics have in the brain?

Answer 18

Depression of:
Reticular system
Hippocampus
Brainstem
Spinal cord (dorsal horn and motor neurones)

Question 19

When are local and regional anaesthetics often given?

Answer 19

Dentistry
Obstetrics
Regional surgery
Post op
Chronic pain

Question 20

What is the main target of local anaesthetic?

Answer 20

Voltage gated sodium channels

Question 21

Where can regional anaesthetic be administered?

Answer 21

Applied to peripheral nerves
Extradural (around spinal cord)
Intrathecal (through meninges

Question 22

What are the main side effects of general anaesthetics?

Answer 22

PONV
Hypotension
Post op cognitive dysfunction
Chest infection

Question 23

What are the main side effects of local anaesthetics?

Answer 23

Cardiovascular toxicity