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2.1 T1: Fundamental Neuroscience and the Brain > T1 L21: Anaesthetic agents > Flashcards

T1 L21: Anaesthetic agents Flashcards

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1
Q

What is the definition of an anaesthetic agent?

A

A reversible drug that induces absence of sensation and awareness.

It’s any lipid soluble agent that causes depression of the brain in a predictable order

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2
Q

What is the predictable order in which anaesthesia depresses the brain?

A
  1. Cortex
  2. Midbrain
  3. Spinal cord
  4. Medulla
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3
Q

What is the order of levels of intoxication by Ethanol?

A 
Tranquilisation
Excitation
Dysarthria 
Ataxia
Sedation/Hypnosis
Anaesthesia
Coma
Medullary depression
Death
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4
Q

What is Dysarthria?

A

Slurring speech

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5
Q

What is Ataxia?

A

Falling over

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6
Q

What is the difference between sedation and being anaesthetised?

A

Sedated people can wake up and talk to you.

Someone who is anaesthetised won’t wake up. You can preform surgery on them

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7
Q

What structures does anaesthesia work on?

A
  • Cell membranes
  • Membrane proteins - modulation of ligand-gated ion channels
  • Global depression of neuronal activity
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8
Q

How does Anaesthesia work?

A

By stimulation of inhibitory receptors (GABA A and Glycine

By inhibition of excitatory receptors (Nicotinic, Serotonin, Glutamate, NMDA)

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9
Q

How do anaesthetic agents work on GABA A?

A

They cause an influx on Cl- which hyperpolarises the cell

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10
Q

What are the 2 methods of administrating aneasthesia?

A

Inhaled or injected

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11
Q

What are some rare side effects of administrating O2?

A

O2 free radicals
CNS convulsion
Pulmonary oxygen toxicity
Retrolateral fibroplasia

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12
Q

What is Retrolateral fibroplasia?

A

An abnormal proliferation of fibrous tissue immediately behind the lens of the eye, leading to blindness. It affected many premature babies in the 1950s, owing to the excessive administration of oxygen

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13
Q

Why is Nitrous oxide not used as an anaesthetic?

A

Because it has a MAC of 105% meaning it can’t fully sedate you

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14
Q

What is MAC?

A

Minimal alveolar concentration. It indicated how powerful an anaesthetic is

A minimum of 20% of O2 is needed so a sedative can’t have a MAC of >80% for it to fully sedate you

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15
Q

What is an analgesic agent?

A

A painkiller

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16
Q

What is the onset/offset of nitric oxide?

A

Quick

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17
Q

What are some complications from using nitric oxide as an anaesthetic?

A

It causes cardiorespiratopry depression
Neuropathy
BM depression

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18
Q

Why is nitric oxide not used with a pneumothorax?

A

Because it’s so small and soluble that it will go into the affected area making the pneumothorax worse

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19
Q

What is Nitric oxide used for clinically?

A

As an analgesic agent

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20
Q

What are some physical properties of inhalational agents?

A 
They are chemically stable
Non-flammable/explosive 
Vaporizable
Environmentally stable 
Have an impact on the environment  
They're non-irritant 
Low blood : gas solubility 
High potency (MAC)
Minimal side effects
Non-toxic
Biotransformation
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21
Q

What is the benefit of Inhalational agents being vaporizable?

A

It’s a liquid at room temperature so it’s vapour can be passed through tubing

22
Q

What is the benefit of a low blood : gas solubility?

A

It leads to a rapid induction and recovery due to less retention following tissue distribution

23
Q

What is biotransformation?

A

The alteration of the drug within the body

24
Q

Why can’t Isoflurane be inhaled?

A

Because it causes irritation

25
Q

What are some properties of Isoflurane?

A 
Inhaled
Cheap
Stable
Non-flammable 
Irritable to airways
MAC of 1.1%
0.2% metabolised
26
Q

What are the side effects of Isoflurane?

A

Causes CV and RS depression

27
Q

What are some properties of Sevoflurane?

A 
Inhaled
Non-irritable
Quick onset/offset
MAC 2%
5% metabolised 
CVS stability 
Gives emergence phenomena
Expensive (less so now because it's been out for a while)
No nasty side-effects
28
Q

What is meant by emergence phenomena?

A

You wake up very quickly after anaesthesia and that’s confusing. This mostly happens in children

29
Q

What are some properties of Desflurane?

A 
Inhaled
Very quick onset/offset
0.02% metabolised 
Moderately expensive
Irritant to airways
Needs a special vaporiser because of the boiling point
MAC 6.35%
Environmentally damaging
30
Q

Which patients is Desflurane used on?

A

On larger patients because it wears off quickly. It’s only used on special occasions because it’s so environmentally damaging

31
Q

What are some properties of intravenous agents?

A 
Rapid and pleasant 
They are redistributed throughout the body 
Metabolised
CVS/RS depression 
Short acting
32
Q

What are intravenous agents used for?

A

For inducing a patient. Inhaled agents are then used to maintain

33
Q

What is meant by redistribution of intravenous agents?

A

They aren’t broken down. They end up in muscles and fat where they cause anaesthetic effects

34
Q

What are some properties of Thiopentone

A 
Injected
Smells like garlic
Antiepileptic
CVS/RS depression 
Cause anaphylaxis in arteries 
Half-life of 10 hours
35
Q

Why can’t Thiopentone be injected into arteries?

A

Because it will precipitate due to changes in pH which occur when mixed with blood (pH 7.4) and may eventually block smaller vessels

36
Q

What are some properties of 2,6-diisopropyphenol (propofol)?

A 
It's a solvent
4min redistribution half-life
4hr elimination half-life 
Minimal accumulation
Anti-emetic
Anti-epileptic
Painful to inject
abnormal movements
CVS/RS side effects
37
Q

Why is Propofol used in TIVA (total intravenous anaesthesia)?

A

It has minimal accumulation

38
Q

What is meant by abnormal movements with Propofol?

A

These are common in children.

It makes it hard to tell if the patient is actually sedated

39
Q

When is Ketamine used as a sedative?

A

In the field because it doesn’t cause airway depression unlike other drugs. It can be given intravenous/intramuscular.
But it has lots of side effects

40
Q

When is Midazolam used as a sedative?

A

When children are often in the hospital because it erases memory.
Also a date-rape drug

41
Q

What are the 2 types of muscle relaxants?

A

Depolarising and non-depolarising

42
Q

Why are muscle relaxants gievn?

A

They cause muscle paralysis so can:
Facilitate intubation
Maintain paralysis throughout surgery/ventilation

43
Q

Why do muscle relaxants have to be given after the anaesthetic?

A

Because the paralysis process can be painful

44
Q

Which type of muscle relaxant will cause the patient to contract all over before they relax?

A

Non-depolarising

45
Q

What are some properties of depolarising muscle relaxants?

A

They mimic acetylcholine
Short half-life (2min)
Multiple side-effects
Metabolised by plasma cholinesterase

46
Q

Where is cholinesterase found?

A

In nerve endings and red blood cells

47
Q

What type of drug is Suxamethonium?

A

A depolarising muscle relaxant

48
Q

What are some properties of non-depolarising muscle relaxants?

A

They are competitive with ACh (blockers)
Duration is variable
Slow onset/offset
Last about 30min

49
Q

Which are more commonly used: depolarising or non-depolarising muscle relaxant?

A

Non-depolarising

50
Q

What are the 2 types of non-depolarising muscle relaxants?

A

Steroid group Eg. Rocuronium

Benzylisoquinoliniums Eg. Atracurium

51
Q

Why is awareness more common with TIVA?

A

Because depth of sedation is harder to measure

52
Q

What is TIVA?

A

Total intravenous anaesthesia used to induce anaesthesia. Most frequently used is Propofol

2.1 T1: Fundamental Neuroscience and the Brain (24 decks)

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