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NSB Lectures > Anaesthetic Drugs > Flashcards

Anaesthetic Drugs Flashcards

1
Q

Do anaesthetics work in the same way?

A

No - is no universal mechanism. Different anaesthetics work in different ways.

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2
Q

What is the triad of anaesthesia?

A

The use of drugs to produce amnesia, analgesia and akinesia - which in turn lightens the load of amnesia (anaesthetic) drugs that need to be given to the patient.

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3
Q

What is the medical term for unconsciousness?

A

Anaesthesia

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4
Q

What is the medical term for muscle relaxation?

A

Akinesia

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5
Q

What is the medical term for pain relief?

A

Analgesia

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6
Q

Do we know how anaesthetic drugs work?

A

No

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7
Q

Name four potential sites that anaesthetic drugs are thought to target in the body.

A

Cerebral cortex
Thalamus
Reticular activating system
Spinal cord

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8
Q

Which receptors do we think anaesthetic drugs potentially have an impact upon?

A

GABA & glutamate receptors
Voltage-gated ion channels
Glycine & serotonin receptors

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9
Q

What do anaesthetic agents do to excitable tissues?

A

Suppress them to varying degrees

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10
Q

What type of solubility do anaesthetic drugs need to have?

A

Need to be lipid soluble

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11
Q

What is the name of the correlation between lipid soluble drugs and potency?

A

Meyer-Overton correlation

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12
Q

What does the Meyer-Overton correlation say?

A

The more lipid-soluble a drug the more potent it is.

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13
Q

Name three inhaled anaesthetic drugs

A

Sevoflurane
Isoflurane
Desflurane

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14
Q

What are propofol, thiopentone, etomidate & ketamine used for?

A

IV anaesthetic drugs

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15
Q

Which is the main IV anaesthetic drug used?

A

Propofol

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16
Q

What is balanced anaesthesia?

A

Using the triad of drugs (analgesia, akinesia & anaesthetics) meaning that you dont have to use too much of one drug and therefore kill the patient.

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17
Q

Why is it important that anaesthetic drugs are lipid soluble?

A

It means that they can cross the BBB

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18
Q

What chemical family are inhaled anaesthetics from?

A

Halogenated ethers

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19
Q

What are the advantages to propofol as a drug?

A

Easy to administer
Doesnt harm the vein
Lipid soluble
Rapidly perfuses the brain & relaxes the larynx
Antiemetic & Antiepileptic
Can maintain anaesthestia with infusion or repeated bolus
Does not accumulate
Rapidly metabolised by the liver

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20
Q

What are the disadvantages to propofol as a drug?

A

Can cause pain on injection & abnormal movements
Can cause hypotension
Is an infection risk due to the lipid it is stored in

21
Q

How does propofol wear off and allow P to wake up?

A

It is redistributed into the tissues - this allows P to wake up.

Ps DO NOT wake up because it is metabolised.

22
Q

Where is propofol redistributed to?

A

Less perfused tissues - such as muscle. However fat levels of the drug remain low because fat is very poorly perfused

23
Q

What is the name of the effect that is used in vaporiser bottles?

A

Plenum effect

24
Q

Name three types of inhalational anaesthetics

A

Halogenated ethers
Nitrous oxide
Xenon

25
Q

How are inhalational anaesthetics administered?

A

Through specific vaporisers which heat up the drug to its specific boiling point and vaporise it.

26
Q

What is the theoretical maximum inspired concentration?

A

70-80%

27
Q

What happens to the patient initially when using a halogenated ether? What is this termed?

A

Analgesia
Excitement (may fight the mask)
then Surgical anaesthesia

Termed etherisation

28
Q

What are the risks of using inhaled anaesthetics?

A

Post-op nausea & vomiting (PONV)
If irritation - can make gas induction difficult (e.g. coughing)
Emergence phenomena - awaking during operation but being unable to move

29
Q

Why is it important that the ideal inhalational agent is not metabolised?

A

Because to metabolise it runs an increased risk of acute hepatitis

30
Q

What do muscle relaxants do?

A

Block neuromuscular junction receptors and stop muscles from working - thereby causing paralysis and cessation of breathing

31
Q

Who should be given muscle relaxants?

A

Unconscious patients only

32
Q

Why do we use muscle relaxants?

A
  • To assist with intubation
  • To facilitate surgery or ventilation
33
Q

What are the two classes of muscle relaxants?

A

Depolarising and non-depolarising

34
Q

How do depolarising muscle relaxants work?

A

Depolarising muscle relaxants bind to the ACh receptor on the post-synaptic membrane. They cause initial depolarisation of this membrane, and then as they do not release - this means the post-synaptic receptor is blocked and cannot be stimulated again.

35
Q

Name one depolarising neuromuscular blocking agent (NMBA).

A

Succinylcholine

36
Q

How rapid is succinycholine in its action?

A

Binds rapidly
Half-life of about 2 mins
Wears off in around 5 mins

37
Q

What is succinylcholine metabolised by?

A

Plasma cholinesterase

38
Q

What are the negatives to using succinylcholine?

A

Has multiple side effects
- Fasciculations
- Anaphylaxis
- K+
- Cholinesterase abnormality…

  • Causes fasciculations which can cause post-op pain for the patient
  • Higher rate of anaphylaxis
  • Can increase levels of K+ in the blood
  • If P has abnormality and doesnt produce cholinesterase - means P can remain paralysed for a few hours (rare)
39
Q

How do non-depolarising NMBAs work compared to depolarising ones?

A

Non-depolarising compounds bind to the post-synaptic receptors competitively but DO NOT cause depolarisation of the post-synaptic membrane

40
Q

What type of compounds are used as non-depolarising agents?

A

Quaternary ammonium compounds

41
Q

How do non-depolarising agents vary in speed from depolarising agents?

A

Non-depolarising agents have slower onset and offset times

42
Q

Name one non-depolarising agent used.

A

Rocuronium

(aslo - vecuronium, pancuronium, benzylisoquinolinium and atracurium)

43
Q

What are NMBAs used for?

A

Intubation
Surgery
Ventilation
ECT
Transfer of patients
Lethal injection

44
Q

Do we usually reverse depolarising agents?

A

Usually not - as effects wear off quickly.

However if there is prolonged paralysis due to cholinesterase deficiency then yes - may need to reverse

45
Q

Which drug do we commonly use to reverse non-depolarising agents?

A

Neostigmine

46
Q

How does neostigmine work?

A

Binds to acetylcholinesterase - thus preventing the breakdown of ACh in the cleft

47
Q

Which drug is used for reversal of NMBAs but is very expensive?

A

Sugammadex

48
Q

How does botulinum work?

A

Prevents vesicles containing ACh from binding to the membrane - therefore preventing the release of ACh into the synaptic cleft

49
Q

What is Botulinum used for?

A

Relief of muscle spasms and contractions
Neuropathic pain
Aesthetic uses

NSB Lectures (48 decks)

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