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5: Y5 - ESA 5 - Pharmacology > Anaesthetics > Flashcards

Anaesthetics Flashcards

1
Q

What are the broad categories of anasthesia?

A
  • General
  • Local
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2
Q

What are the methods of administration of general anasthesia?

A
  • Inhalation, or volatile
  • Intravenous
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3
Q

What is the difference in onset of action between inhalational and intravenous general anaesthesia?

A

Intravenous is quicker

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4
Q

What is conscious sedation?

A

The use of small amounts of anaesthetics or benzodiazepines to produce a ‘sleepy-like’ state

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5
Q

What are the stages in general anaesthesia?

A
  1. Premedication
  2. Induction
  3. Intraoperative
  4. Muscle paralysis
  5. Maintenenance
  6. Reversal of muscle paralysis and recovery, which includes post-operative analgesia
  7. Provision for PONV
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6
Q

What is often used in the premedication stage of anaesthesia?

A

A hypnotic, typically benzodiazepine

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7
Q

How is anaesthesia induction normally performed?

A

Usually IV, but may be inhalational

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8
Q

Give an example of a drug used in anaesthesia induction

A

Barbituates

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9
Q

What class of drug is usually used for intraoperative analgesia?

A

Opioids

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10
Q

What is the purpose of muscle paralysis in surgery?

A

To facilitate intubation/ventilation/stillness

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11
Q

Why is intubation important in anaesthesia?

A

Analgesia can cause respiratory depression, so you need a relaxant to allow airway access

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12
Q

How is maintenance anaesthesia administered?

A

Intravenous and/or inhalation

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13
Q

What is used for postoperative analgesia?

A
  • Opioids
  • NSAID
  • Paracetamol
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14
Q

How is volatile general anaesthesia administered?

A

You fill a reservoir with the liquid drug which then evaporates. Fresh gas flows across evaporated liquid and the patient inahles it

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15
Q

What molecules will act as anaesthetics?

A

Any molecule with a volitile compononet

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16
Q

Describe the use of xenon as an anaesthetic

A

It is a very good anaesthetic in very high concentrations, and is good in neonates to prevent cerebral ischaemia

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17
Q

Give four examples of intravenous anaesthetic agents

A
  • Propofol
  • Barbiturates
  • Etomidate
  • Ketamine
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18
Q

What are the stages in Guedel’s signs?

A
  • Stage 1 - Analgesia and consciousness
  • Stage 2 - Unconscious, breathing erratic. Delirium could occur, leading to an excitement phase
  • Stage 3 - Surgical anaesthesia
  • Stage 4 - Respiratory paralysis and death
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19
Q

Describe the muscle tone in Guedel’s stage 1

A

Normal

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20
Q

Describe the eye movements in Guedel’s stage 1

A

Slight

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21
Q

How long does Guedel’s stage one last?

A

Only the first few breaths

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22
Q

Describe the muscle tone in Guedel’s stage 2

A

Normal to markedly increased

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23
Q

Describe the eye movements in Guedel’s stage 2

A

Moderate

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24
Q

Describe the muscle tone in Guedel’s stage 3

A

Progresses from slightly relaxed to markedly relaxed

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25
Q

Describe the eye movements in Guedel’s stage 3

A

Progresses from slight to none

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26
Q

Describe breathing in Guedel’s stage 3

A

Decreases until significantly reduced respiratory effort

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27
Q

What are the options once a patient reaches Guedel’s stage 4?

A
  • Wake patient
  • Ventilate the patient
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28
Q

What is anasthesia a combination of?

A
  • Analgesia
  • Hyponosis
  • Depression of spinal reflexes
  • Muscle relaxation
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29
Q

What is the end point of anasthesia dependant on?

A

Concentration

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30
Q

In what order to functions go under anaesthesia?

A
  1. Memory
  2. Consciousness
  3. Movement
  4. Cardiovascular response
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31
Q

What measure is used to describe potency for volatile anaesthetics?

A

MAC - Minimum Alveolar Concentration

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32
Q

What is MAC?

A

The alveolar concentration of the anaesthetic at which 50% of subjects fail to move to surgical stimulus

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33
Q

What is the alveolar concentration of anaesthetic equal to at equilibrium?

A

The concentration of anaesthetic in the spinal cord

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34
Q

What is the anatomical substrate for MAC?

A

The spinal cord

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35
Q

What important factor affects induction and recovery?

A

The partition coefficients (solubility)

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36
Q

What are the potential partitions in anaesthetics?

A
  • Blood:gas partition
  • Oil:gas partition
37
Q

What does the blood:gas partition coefficient measure?

A

The solubility of gas in the blood

38
Q

What effect does a low blood:gas partition have on induction and recovery?

A

Means it will be fast

39
Q

What does the oil:gas coefficient measure?

A

The solubility of gas in fat

40
Q

What does the oil:gas partition coefficient determine?

A

The potency

41
Q

Why does the oil:gas partition coefficient determine potency?

A

Because target sites are in membranes

42
Q

What factors affect MAC?

A
  • Age
  • Body temperature
  • Pregnancy
  • Alcoholism
  • Central stimulants
  • Other anaesthetics and sedatives
  • Opiods
43
Q

How does age affect MAC?

A

It is high in infants, and low in the elderly

44
Q

How does body temperature affect MAC?

A

It is increased in hyperthermia and decreased in hypothermia

45
Q

How does pregnancy affect MAC?

A

Increases it

46
Q

How does alcoholism affect MAC?

A

Increases it

47
Q

How do central stimulants affect MAC?

A

Increase it

48
Q

How do other anaesthetics and sedatives affect MAC?

A

Decrease it

49
Q

How do opiods affect MAC?

A

Decrease it

50
Q

How does administering anaesthetic agents with nitrous oxide affect MAC?

A

Significantly reduced

51
Q

What is the advantage of reducing MAC using nitrous oxide?

A

Can provide an extra window of safety

52
Q

Other than lipid solubility, what does anaesthetic potency correlate to?

A

GABAA activity

53
Q

What is GABAA?

A

A major inhibitory neurotransmitter

54
Q

What kind of receptor is the GABAA receptor?

A

Ligand gated ion channel

55
Q

What happens when GABAA binds to its receptor?

A

It causes the opening of the ion channel, allowing flow of Na+ and therefore the membrane becomes more difficult to excite, leading to CNS depression

56
Q

What are the effects of GABAA receptor activation?

A
  • Anxiolysis
  • Sedation
  • Anaesthesia
57
Q

Which anaesthetics potentiate GABAA mediated Cl- conductance to depress CNS activity?

A

All except for Xe, N2O and ketamine

58
Q

What receptors do Xe, N2O and ketamine act on?

A

Probably NMDA receptors

59
Q

What balance exists in the conscious brain?

A

Excitation (glutamate) and inhibition (GABA)

60
Q

What effect do anaesthetics have on the balance in the brain?

A

They modulate it

61
Q

What effect do anaesthetics have on brain structures?

A
  • Reticular formation (hindbrain, midbrain, and thalamus) are depressed
  • Hippocampus depressed, reducing memory
  • Brainstem depressed, reducing respiratory and some CVS functions
  • The dorsal horn of the spinal cord is depressed in analgesia
  • The motor neuronal activity of the spinal cord is depressed with MAC
62
Q

What does the reticular system normally do?

A

Increase arousal, hence it is called the activating system

63
Q

What does the thalamus normally do?

A

Transmits and modifies sensory information

64
Q

What are the main intravenous anaesthetics?

A
  • Propofol
  • Barbiturates
  • Ketamine
65
Q

What is the use of intravenous anaesthetics?

A
  • Induction
  • Can be used as the sole anaesthetic in TIVA (Total Intravenous Anaesthesia)
66
Q

What happens in TIVA?

A

An infusion pump continues adminsteration, typically using propofol

67
Q

How is intravenous anaesthetic potency described?

A

As the plasma concentration to acheive a specific end point, e.g. loss of eyelash reflex, BIS value

68
Q

What is the end point used to determine in mixed anaesthesia?

A

The point at which to switch to volatile anaesthesia after induction

69
Q

How does TIVA determine what dose to be giving?

A

It uses a defined PK based algorithm to infuse at a rate to maintain the set point

70
Q

What are the uses of local and regional anaesthetics?

A
  • Dentisty
  • Obstetrics
  • Regional surgery
  • Post-op
  • Chronic pain management
71
Q

Give 4 examples of local anaesthetics

A
  • Lidocaide
  • Bupivacaine
  • Ropivacaine
  • Procaine
72
Q

What factors determine the characterstics of local anaesthetics?

A
  • Lipid solubility
  • Dissociation constant
  • Chemical link
  • Protein binding
73
Q

What does the solubility of local anaesthetics determine?

A

The potency - the higher the lipid solubility, the higher the potency

74
Q

What does the dissocation constant determine in local anaesthetics?

A

The time of onset - lower the pKa, the faster the onset

75
Q

What does the chemical link determine in local anaesthetics?

A

The rate of metabolism - ester links don’t last as long, as tissues possess lots of esterases, whereas amides last longer

76
Q

What does protein binding effect in local anaesthetics?

A

Duration - the more the binding, the longer the duration

77
Q

What is regional anaesthesia?

A

Selectively anaesthetising a part of the body

78
Q

What is regional anaesthesia often described as?

A

A ‘block’ of a nerve

79
Q

What agents to regional anaesthetics use?

A

A local anaesthetic, with or without an opiod

80
Q

What are the sites of regional anaesthesia in the upper extremity?

A
  • Interscalene
  • Supraclavicular
  • Infraclavicular
  • Axillary
81
Q

What are the sites of reginal anaesthesia in the lower extremity?

A
  • Femoral, sciatic, popliteal, saphenous
82
Q

What regional anaesthetics are used in labour?

A
  • Extradural
  • Intrathecal
  • Combined
83
Q

What are the main side effects of general anesthesia?

A
  • PONV (with opiods)
  • Hypotension
  • Post-operative cognitive dysfunction
  • Chest infection
84
Q

What increases the risk of post-operative cognitive dysfunction?

A

Increasing age

85
Q

What do side effects of local and regional anaesthesia usually result from?

A

Systemic spread

86
Q

What might result in systemic spread of anaesthetics?

A
  • Wrong dose
  • Wrong site of administration
87
Q

Give an example of a systemic side effect of local anaesthetics

A

Cardiovascular toxicity, as locals are sodium channel blockers

88
Q
A

5: Y5 - ESA 5 - Pharmacology (28 decks)

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