Principles of pharmacology

Question 1

What is the triad of anaesthesia?

Answer 1

Relaxation (local/general anaesthetics, muscle relaxants)
Analgesia (Local/general
anaesthetics. opiates)
Hypnosis (General anaesthetics, opiates)

Question 2

What is a drawback of muscle relaxation?

Answer 2

Paralyse skeletal muscle indiscriminately
Requirement of artificial ventilation
Airways must be managed

Question 3

What causes awareness under anaesthesia?

Answer 3

Paralysed with muscle relaxant yet insufficiently anaesthetised

Question 4

How do general anaesthetics work?

Answer 4

Hyper polarise neurons by so they’re less less likely to fire
Mostly through opening chloride channels

Question 5

What is the onset and recovery with IV anaesthesia like?

Answer 5

Rapid
Act v quickly
One off bolus will wear off quickly

Question 6

Name an important characteristic of thiopentone and propofol (IV agents)?

Answer 6

Highly fat soluble so can cross BBB rapidly

Question 7

Which tissues pick up IV anaesthesia fastest?

Answer 7

Viscera
Then muscle
Then fat

Question 8

What is a consequence of high fat solubility of IV anaesthetics?

Answer 8

After lengthy surgery there will be large amounts of anaesthetic drug stored in fatty tissue which leaks out slowly

Question 9

What is TCI?

Answer 9

Target Controlled Infusion (TCI) pump system

Allows very accurate infusion to achieve specific blood or brain concentrations of agents

Question 10

What is MAC?

Answer 10

Minimum alveolar concentration
Measure of potency
Low number means high potency

Question 11

Describe the onset of inhalational anaesthetics.

Answer 11

Slow induction

Question 12

How is general anaesthesia usually administered?

Answer 12

IV induction

Inhalational maintenance

Question 13

What are the respiratory effects of general anaesthesia?

Answer 13

Respiratory depressant
Reduce hypoxic and hypercarbic drive
Decrease tidal volume and increase rate
Paralyse cilia

Question 14

What are the CV effects of general anaesthesia?

Answer 14

Depresses CV centre
Negatively ionotropic
Vasodilation resulting in decreased VR and CO

Question 15

What is a post-op problem with muscle relaxants?

Answer 15

Airway obstruction and ventilatory insufficiency in immediate post-op period

Question 16

Why may analgesia be given to a patient who is already unconscious?

Answer 16

Prevents reflex response to painful stimuli (Tachycardia, sudden movement)
Stops pain waking them up
Opiate analgesics have a direct sedative effect which contributes to general anaesthesia

Question 17

Is fentanyl short or long acting?

Answer 17

Short

Potent

Question 18

How do local anaesthetics work?

Answer 18

Block Na+ channels to prevent axonal action potential propagating

Question 19

Why may regional anaesthesia be preferred in patients with concomitant resp problems?

Answer 19

Main physiological effects are cardiovascular and spare the resp function

Question 20

How has US affected general anaesthesia?

Answer 20

US guided needle placement allows safer and more effective delivery of the local anaesthetic (LA) drug with less likelihood of the LA going intravenously or direct nerve or vascular injury

Question 21

What are some medications which may be reduced or halted pre-op?

Answer 21

Anti-diabetic medications

Anticoagulants

Question 22

What are some major lifestyle factors which should be improved on pre-surgery?

Answer 22

Smoking
Alcohol
Obesity
Exercise

Question 23

What are METs?

Answer 23

Measurement of exercise tolerance

15% reduction in mortality risk per MET