General Anaesthetics

Question 1

Intravenous generals

Answer 1

Propofol
Thiopentone
Etonidate

Question 2

Inhalation generals

Answer 2

Nitrous oxide
Isoflurane
Sevoflurane
Desflurane

Question 3

Definition of a general

Answer 3

Reversible, drug induced loss of consciousness, usually to allow a surgical procedure to be performed

Question 4

How are inhalation generals delivered

Answer 4

Gas or vapour via a breathing circuit which are used to INDUCE anaesthesia in children (sevoflurane) and maintain it in adults

• nitrous oxide
• desflurane
• isoflurane

Question 5

Entenox

Answer 5

This is 50:50 nitrous oxide and oxygen

Used as an analgesic, labour pain and trauma

Question 6

What is the trend for inhalation agents

Answer 6

The more lipid solvable the more potent but the lower the MAC

Question 7

What is MAC

Answer 7

Minimum alveolar concentration at which 50% of the population fail to reposed to surgical stimulus

INVERSLEY PROPORTIONAL TO POTENCY

Question 8

How to general anaesthetics work

Answer 8

They act on ion channels by promoting ion channels which inhibit synaptic transmission they also inhibit excitatory ion channels

They act allosterically and augment inhibitory signals

Act on GABA

Question 9

What is the arrangement of GABA A receptors

Answer 9

• Pentameric arrangement
• Central ion channel pore
• 18 possible sub units
• Approx 30 forms of receptor
• Some subunits location specific
• Anaesthetics allosterically activate the receptor

Question 10

Why is ketamine used in the field

Answer 10

It doesn’t inhibit respiration

Question 11

What receptors does ketamine act on

Answer 11

NMDA

Question 12

What are the consequences of ketamine misuse

Answer 12

• Special K
• Sniffed / snorted
• Increasing misuse
• Reclassified as class B
• Bladder problems
• Dissociative “k-hole”

Question 13

How are most drugs metabolised

Answer 13

Drug redistribution

Question 14

Why does ketamine differ from other anaesthetics when it comes to the cardiovascular system

Answer 14

It causes vasoconstriction and increases BP

Question 15

What do we want it to do?

Answer 15

• Act rapidly
• Pleasant
• Cheap to manufacture
• Stable (soda lime)
• Analgesic effect
• Amnesic effect
• Minimal “hangover”

Question 16

What do we want it NOT to do

Answer 16

• Irritant on veins or airways
• Emetic
• Minimal effects on other systems
• Breathing
• Cardiovascular
Produce toxic metabolites
Cause histamine release / anaphylaxis

Question 17

Balanced anaesthesia what things are considered

Answer 17

Selection of drugs and techniques bearing in mind the
1. health & requests of the patient
2. the properties of the drugs
3. the requirements of surgery
to minimise patient risk and maximise patient safety and comfort.