Anaesthetics- Principles of Pharmacology

Question 1

What is general anaesthesia?

Answer 1

A state of controlled unconsciousness.

Question 2

How is General anaesthetic administered?

Answer 2

Via centrally acting drugs, such as Hypnotics or Analgesia

Question 3

What does regional anaesthesia do?

Answer 3

Produce insensibility in an area or region of the body

Question 4

How does regional anaesthesia work?

Answer 4

• Nerve and plexus blocks

* Applied to nerves supplying relevant areas

Question 5

What does local anaesthesia do?

Answer 5

• Produces insensibility on the relevant part of the body

Applied directly to the tissue

Question 6

What is the ASA score used for?

Answer 6

To work out if someone is healthy enough for anaesthesia and surgery

Question 7

What is the triad of anaesthesia?

Question 8

What is the triad of anaesthesia?

Answer 8

Hypnosis
Analgesia
Relaxation

Question 9

What is hypnosis?

Answer 9

Unconsciousness.

Done via opiates or general anaesthetic agents (main)

Question 10

What is analgesia?

Answer 10

Pain relief.

Done via opiates, local anaesthetic and general anaesthetics

Question 11

What is relaxation?

Answer 11

Skeletal muscle relaxation.

Done via muscle relaxants (mainly), general anaesthetic agents and local anaesthetic agents

Question 12

What are the 3 main problems of anaesthetics?

Answer 12

Polypharmacy
Muscle relaxation
Separation of relaxation and hypnosis

Question 13

What is the problem with polypharmacy?

Answer 13

Increases chances of drug reactions and allergies

Question 14

What is the problem with muscles relaxation?

Answer 14

Artificial ventilation, patients airways need managed

Question 15

What is the problem of Separation of relaxation and hypnosis?

Answer 15

Awareness

Question 16

What is the main effect of general anaesthetic agents?

Answer 16

Hypnosis/ unconsciousness

Question 17

How do general anaesthetic agents work?

Answer 17

• Interfere with neuronal ion channels

* Hyperpolarise neurones- Less likely to fire

Question 18

How do general anaesthetic inhalation agents work?

Answer 18

Dissolve in membranes

Have a direct physical effect

Question 19

How do general anaesthetic IV agents work?

Answer 19

Allosteric binding

GABA receptors open chloride channels

Question 20

What type of drugs are used for intravenous anaesthesia?

Answer 20

Fat soluble drugs

Question 21

Why are fat soluble drugs used for IV anaesthesia?

Answer 21

Rapid onset of unconsciousness

Rapid disappearance of drug from circulation

Question 22

How is the onset of unconsciousness measured?

Answer 22

1 arm-brain circulation time

Question 23

What type of drug are inhalation anaesthetics?

Answer 23

Halogenated hydrocarbons

Question 24

How are inhalation anaesthetics taken up and excreted?

Answer 24

Via the lungs

Question 25

Why are inhalation anaesthetics given in high concentrations?

Answer 25

To create a partial pressure gradient between the lungs > blood > brain

Question 26

What does MAC stand for?

Answer 26

Minimum alveolar pressure

Question 27

What is MAC?

Answer 27

The concentration of inhaled agent that is required to achieve a certain level of anaesthesia

Question 28

What is MAC a measure of?

Answer 28

Potency- high number, low potency

Question 29

Is the induction of inhalation slower or faster than IV?

Answer 29

Slower | It takes longer to build up effective concentrations

Question 30

Is the duration of inhalation longer or shorter than IV?

Answer 30

Longer-prolonged duration

Question 31

What effect does general anaesthetic have on the cardiovascular system?

Answer 31

Depress cardiovascular system

Question 32

What are the central effects of general anaesthesia on the CVS?

Answer 32

* Reduce sympathetic outflow * Negative iontropic/chronotropic effect on the heart * Reduced vasoconstrictor tone->Vasodilation

Question 33

What are the direct effects of general anaesthesia on the CVS?

Answer 33

* Negatively inotropic * Vasodilation- Decreased peripheral resistance * Venodilation- Decreased venous return and decrease cardiac output

Question 34

What is the effect of general anaesthesia on the respiratory system?

Answer 34

All anaesthetic agents are respiratory depressants • Reduce hypoxic and hypercarbic drive • Decreased tidal volume & increase rate Paralyse cilia Decrease FRC- Lower lung volumes, VQ mismatch

Question 35

What are the indications for using muscle relaxants?

Answer 35

* Ventilation & Intubation * When immobility is essential-microscopic surgery, neurosurgery * Body cavity surgery

Question 36

What are the problems of muscle relaxants?

Answer 36

* Awareness * Incomplete reversal → airway obstruction, ventilatory insufficiency in immediate post op period * Apnoea = dependence on airway and ventilatory support

Question 37

What are the effects of local and regional anaesthesia?

Answer 37

* Retain awareness/ consciousness * Lack of global effect of G? * Derangement of CVS physiology * Relative sparing of respiratory function