Principles and Pharmacology

Question 1

What is general anaesthesia?

Answer 1

Produces insensibility in the whole body, usually causing unconsciousness
Centrally acting drugs- hypnotics/analgesics

Question 2

What is regional anaesthesia?

Answer 2

Produces insensibility in an area or region of the body, local anaesthetic applied to nerves supplying relevant areas

Question 3

What is local anaesthetic?

Answer 3

Producing insensibility in only the relevant part of the body, local anaesthetic applied directly to the tissues

Question 4

What types of drugs are used as anaesthesia?

Answer 4

Inhalational anaesthetics 
Intravenous anaesthetics 
Muscle relaxants
Local anaesthetics 
Analgesics

Question 5

What types of techniques and equipment are used in anaesthesia?

Answer 5

Tracheal intubation 
Ventilation 
Fluid therapy 
Regional anaesthesia 
Monitoring

Question 6

Why are hypnotics needed in anaesthesia?

Answer 6

Provides unconsciousness for general anaesthesia

Question 7

Why are analgesics used in anaesthesia?

Answer 7

Pain relief, still required under GA to suppress reflex autonomic responses to painful stimulus

Question 8

Why are muscle relaxants used in anaesthesia?

Answer 8

Provide immobility for certain procedures to allow access to body cavities and to permit artificial ventilation amongst other things

Question 9

What problems can arise with anaesthesia?

Answer 9

Polypharmacy
Muscle relaxation
Separation of hypnosis and relaxation

Question 10

How do general anaesthetic agents work?

Answer 10

Interfere with neuronal ion channels
Hyperpolarise neurones - less likely to ‘fire’
Inhalational agents dissolve in membranes
IV agents- allosteric binding on GABA receptors, open Cl channels

Question 11

What type of molecules are inhalation anaesthetics formed of?

Answer 11

Halogenated hydrocarbons

Question 12

What part of the body uptakes and excretes inhalation anaesthesia?

Answer 12

Lungs

Question 13

What is MAC?

Answer 13

Minimum alveolar concentration- the concentration of the drug required in the alveoli which is required to produce anaesthesia with any particular agent

Question 14

What does a low MAC number mean?

Answer 14

High potency

Question 15

What is the main role of inhalation anaesthesia?

Answer 15

Extension or continuation of anaesthesia

Question 16

What effects does GA have centrally on the cardiovascular system?

Answer 16

Depresses cardiovascular centre
Reduces sympathetic outflow
Negative inotropic/ chronotropic effect on heart
Reduced vasoconstrictor tone

Question 17

What effects does GA have directly on the cardiovascular system?

Answer 17

Vasodilation - decreased peripheral resistance

Venodilation - decreased venous return, decreased cardiac output

Question 18

What is the equation for mean arterial pressure?

Answer 18

MAP= Cardiac output x systemic vascular resistance

Question 19

What effects does GA have on the respiratory system?

Answer 19

Respiratory depressants
Reduce hypoxia and hypercarbic drive
Decreased tidal volume and increase rate
Paralyse cilia
Decrease FRC - lower lung volumes, VQ mismatch

Question 20

What are the indications for muscle relaxants?

Answer 20

Ventilation and intubation
When immobility is essential
Body cavity access needed

Question 21

What are the problems with muscle relaxants?

Answer 21

Awareness
Incomplete reversal (airway obstruction, ventilatory insufficiency)
Apnoea

Question 22

What are non-polarising NMBs?

Answer 22

Competitive block of nicotinic acetylcholine receptors at NMJ that prevents the opening of sodium channels

Question 23

What are depolarising NMBs?

Answer 23

Depolarise motor end plate

Renders post-junctional membrane refractory to further stimulus

Question 24

What depolarising NMBs is commonly used?

Answer 24

Suxamethonium

Question 25

What are the benefits of using suxamethonium?

Answer 25

Very rapid onset | Short duration of action (<5min)

Question 26

What are the risks of using suxamethonium?

Answer 26

Myalgia Anaphylaxis Malignant hyperthermia

Question 27

What is the reason for intraoperative analgesia?

Answer 27

Prevention of arousal Opiates contribute to hypnotic effect of GA Suppression of reflex responses to painful stimuli

Question 28

What are some examples of local anaesthetic drugs?

Answer 28

Lignocaine Bupivacaine Prilocaine

Question 29

How do local anaesthetic drugs work?

Answer 29

Sodium channel blockers | Prevent propagation of action potential

Question 30

What is the main factor that limits how much LA can be used?

Answer 30

Toxicity

Question 31

What does LA toxicity depend on?

Answer 31

Dose used Rate of absorption Patient weight Drug

Question 32

What are the signs and symptoms of LA toxicity?

Answer 32

``` Circumoral and lingual numbness and tingling Light-headedness Tinnitus, visual disturbances Muscular twitching Drowsiness Cardiovascular depression Convulsions Coma Cardiorespiratory arrest ```

Question 33

What are the benefits of regional and local anaesthesia?

Answer 33

Retain awareness/ consciousness Lack of global effects of GA Relative sparing of respiratory function

Question 34

What are the physiological effects of regional anaesthesia?

Answer 34

Inspiratory function relatively spared Expiratory function relatively impaired Decrease FRC Increased VQ mismatch

Question 35

What are the indications for spinal and epidural anaesthesia?

Answer 35

Avoidance of GA Severe respiratory disease Avoid airway problems Allergies/reactions to GA agents

Question 36

What are the contraindications for spinal and epidural anaesthetic?

Answer 36

``` Patient refusal Fixed cardiac output (aortic/ mitral stenosis) Infection Bleeding diathesis/ anticoagulation Technical difficulties Spinal problems/neurology ```

Question 37

What is the location used in spinal anaesthesia?

Answer 37

Subarachnoid | T4 3-4ml LA

Question 38

What is the usually duration of a spinal anaesthesia?

Answer 38

2-3 hours

Question 39

What is the usually duration of an epidural anaesthesia?

Answer 39

Extradural | Block to T4 20+ml LA

Question 40

What is the usually duration of an epidural anaesthetic?

Answer 40

3-4 hours