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MODULE 14 - Patient Support > PHARMACOLOGY - Anaesthetics > Flashcards

PHARMACOLOGY - Anaesthetics Flashcards

1
Q

Give three examples of injectable anaesthetic agents

A

Propofol
Alfaxalone
Ketamine

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2
Q

What is the mechanism of action for propofol?

A

Propofol potentiates the activity of inhibitory GABAa receptors

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3
Q

Which species’ is propofol liscenced in?

A

Dogs
Cats

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4
Q

How should propofol be administered?

A

Intravenous (I.V.)

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5
Q

Why is it recommended not to infuse propofol for more than 30 minutes?

A

Propofol is formulated with benzyl alcohol and infusion of propofol for more than 30 minutes increases the risk of benzyl alcohol toxicity

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6
Q

What else can be done to reduce the risk of benzyl alcohol toxicity?

A

To reduce the risk of benzyl alcohol toxicity, don’t administer more than 24mg/kg of propofol per anaesthetic

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7
Q

Why does propofol have such a rapid onset and a quick duration of action?

A

Propofol has a high lipid solubility and thus travels rapidly to the brain to carry out the desired effects. However, propofol is also rapidly redistributed to other blood rich organs and lipid stores where the drug will accumulate. Propofol is also rapidly metabolised

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8
Q

Which organs metabolise propofol?

A

Liver
Unknown site

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9
Q

What are the effects of propofol on the central nervous system (CNS)?

A

Rapid loss of consiousness
Anti-epileptic

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10
Q

What are the five side effects of propofol?

A

Transient hypotension
Post-induction apnoea
Occasional muscle twitching
Heinz body anaemia in cats
Pain on injection

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11
Q

What are the two main indicators for the use of propofol?

A

Intravenous induction of anaesthesia
Management of refractory seizures

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12
Q

Why should you be cautious when using propofol in hypovolaemic patients?

A

Propofol is highly plasma protein bound and since hypovolaemic patients have fewer plasma proteins, there will be more free drug within the circulation and thus there will be a more profound pharmacological effect. Furthermore, propofol can cause vasodilation and hypotension, which will have a more profound effect in hypovolaemic patients

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13
Q

Why should you be cautious when using propofol in cats with hepatic dysfunction?

A

Cats metabolise propofol slower than dogs which can result in the increased accumulation of propofol in the body, especially in cats with hepatic dysfunction who cannot metabolise the drug as effectively as a healthy animal

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14
Q

Why should you be cautious when using propofol in cats that require repeat anaesthetics?

A

There is an increased risk of heinz body anaemia in cats with repeated or continuous infusions of propofol

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15
Q

What is the mechanism of action for alfaxalone?

A

Alfaxalone potentiates the activity of inhibitory GABAa receptors

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16
Q

Which species’ is alfaxalone liscenced in?

A

Dogs
Cats
Rabbits

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17
Q

How can alfaxalone be administered?

A

Intravenous (I.V.) preferably
Intramuscular (I.M.)
Subcutaneous (S.C.)

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18
Q

Why does alfaxalone have such a rapid onset and a quick duration of action?

A

Alfaxalone has a high lipid solubility and thus travels rapidly to the brain to carry out the desired effects. However, alfaxalone is also rapidly redistributed to other blood rich organs and lipid stores where the drug will accumulate. Alfaxalone is also rapidly metabolised

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19
Q

Which organ metabolises alfaxalone?

A

Liver

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20
Q

Why is alfaxalone tolerated better in cats compared to propofol?

A

While alfaxalone is metabolised slower in cats compared to dogs, it is not as significant as with propofol and thus there is less accumulation of alfaxalone in the body and thus it is more well tolerated in cats compared to propofol

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21
Q

(T/F) Alfaxalone has higher plasma protein binding than propofol

A

FALSE. Alfaxalone has a lower plasma protein binding than propofol

Could be a better choice for induction of hypovolaemic patients

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22
Q

What is the effect of alfaxalone on the central nervous system (CNS)?

A

Rapid loss of consiousness

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23
Q

What are the two side effects of alfaxalone?

A

Mild hypotension
Post-induction apnoea

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24
Q

What are some of the other effects of alfaxalone?

A

Alfaxalone can result in a poor quality anaesthetic recovery especially if there has been limited premedication

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25
Q

What are the three main indicators for the use of alfaxalone?

A

Intravenous administration to induce anaesthesia
Intravenous administration to maintain anaesthesia
Occasionally IM/SC administration for sedation

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26
Q

When can IM/SC alfaxalone be benefical as a sedative?

A

IM/SC alfaxalone can be useful to sedate old/sick cats which are difficult to handle. Alfaxolone has less of a significant cardiovascular effect as other sedatives which is useful in sick animals and provides a level of sedation which is beneficial in animals that are difficult to handle

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27
Q

What are the drawbacks for using IM/SC alfaxalone for sedation?

A

Not authorised
Requires a large volume of alfaxalone for injection

28
Q

What is the mechanism of action for ketamine?

A

Ketamine is a glutamate-gated NMDA receptor antagonist

29
Q

Ketamine is a dissociative anaesthetic. What are the five features of dissociative anaesthesia?

A

Eyes remain open
Active reflexes
Hypertonicity
Analgesia
Decreased cardiovascular and respiratory depression

30
Q

Which species’ is ketamine liscenced in?

A

Dogs
Cats
Horses
Sheep
Goats
Small mammals

31
Q

How can ketamine be administered?

A

Intravenous (I.V.)
Intramuscular (I.M.)
Subcutaneous (S.C.)

32
Q

Which organ metabolises ketamine?

A

Liver

33
Q

What are the effects of ketamine on the central nervous system (CNS)?

A

Loss of consiousness
Analgesia
Proconvulsant
Emergence delirium

34
Q

In which two species does ketamine act as a proconvulsant?

A

Dogs
Horses

35
Q

What are the effects of ketamine on the cardiovascular system?

A

Ketamine results in an increased sympathetic drive which results in an increased heart rate, cardiac contractility, cardiac output and blood pressure

36
Q

What are the effects of ketamine on the respiratory system?

A

Transient apneoa following intravenous (I.V.) administration

37
Q

What is the effect of ketamine on the musculoskeletal system?

A

Hypertonicity

38
Q

(T/F) Ketamine should never be used as a sole anaesthetic agent

A

TRUE.

39
Q

What are the three main indicators for the use of ketamine?

A

Intravenous induction of anaesthesia
Intramuscular induction and maintenance of anaesthesia
Provide analgesia

40
Q

What drug is ketamine combined with for IV induction of anaesthesia?

Can be done in dogs, cats and horses

A

Benzodiazepines

41
Q

Which drug is ketamine combined with for IM induction and maintenance of anaesthesia?

Can be done in dogs and cats

A

α2 agonist and opioid

42
Q

When is ketamine indicated as an analgesic drug?

A

Pre-existing pain
In situations predisposed to developing chronic pain
Adjunct to other analgesics for difficult to manage pain

43
Q

When may you choose ketamine as your anaesthetic agent over propofol or alfaxalone?

A

Haemodynamically unstable patients
If IM anaesthesia is required

44
Q

When should you be cautious when using ketamine?

A

In patients with a history of seizures
In patients with an elevated intracranial pressure (ICP)
In patients with pre-existing tachycardia

45
Q

What is total intravenous anaesthesia (TIVA)?

A

Total intravenous anaesthesia (TIVA) is the use of intravenous anaesthetic agents for both induction and maintenance of anaesthesia

46
Q

Which intravenous anaesthetic drugs are appropriate for total intravenous anaesthesia (TIVA) in dogs?

A

Propofol
Alfaxalone

47
Q

Which intravenous anaesthetic drug is appropriate for total intravenous anaesthesia (TIVA) in cats?

A

Alfaxalone

48
Q

What is the main advantage of using inhalational general anaesthetics as maintenance drugs?

A

Allows for rapid adjustment of anaesthetic depth

49
Q

What are the two disadvantages of using inhalational general anaesthetics as maintenance drugs?

A

There is a lot of equipment required
Environmental pollution

50
Q

What is indicated by a high oil:gas partition coefficient?

A

A high oil:gas partition coefficient indicates that an inhalational anaesthetic has a higher lipid solubility and thus a higher potency (lower quantity of drug is required to achieve the desired effect)

51
Q

What is indicated by a low blood:gas partition coefficient?

A

A low blood:gas partition coefficient indicates that an inhalational anaesthetic has a more rapid induction, recovery and rate of change of anaesthetic depth

52
Q

What is the minimum alveolar concentration (MAC)?

A

The concentration of the drug required so 50% of patients will not respond to a particular stimulus

53
Q

What is indicated by a low minimum alveolar concentration (MAC)?

A

A low minimum alveolar concentration (MAC) indicates that the inhalational anaesthetic has a higher potency as a lower concentration is required to produce the desired effect

54
Q

Which organ metabolises inhalational general anaesthetics?

A

Liver

55
Q

How are inhalational general anaesthetics eliminated?

A

Expiration

56
Q

What is the risk of more highly metabolised general anaesthetics?

A

General anaesthetics are metabolised into toxic metabolites which can be eliminated through expiration and thus pose a risk to the staff in the operating theatre

57
Q

Give two examples of halogenated inhalational anaesthetic drugs

A

Isoflurane
Sevoflurane

58
Q

What is the effect of isoflurane and sevoflurane on the central nervous system (CNS)?

A

Loss of consiousness

59
Q

What is the effect of isoflurane and sevoflurane on the cardiovascular system?

A

Vasodilation and hypotension

60
Q

What is the effect of isoflurane and sevoflurane on the respiratory system?

A

Respiratory depression

Less respiratory depression with sevoflurane compared to isoflurane

61
Q

Compare the phamacokinetic properties of isoflurane and sevoflurane

A
  • Sevoflurane has a lower oil:gas partition coefficient and thus a higher MAC value compared to isoflurane meaning sevoflurane is less potent than isoflurane
  • Sevoflurane has a lower blood:gas partition coefficient than isoflurane so sevoflurane has a more rapid induction, recovery and rate of change of anaesthetic depth compared to isoflurane
  • Sevoflurane is more highly metabolised than isoflurane so they is a higher risk of the expiration of toxic metabolites
62
Q

Why is isoflurane not an appropriate induction drug?

A

Isofluorane has an unpleasant odour which will cause animals to resist the mask induction

63
Q

Why is sevofluorane an appropriate induction drug?

A

Sevofluorane has a pleasant odour, causes minimal airway irritation and has a rapid onset

64
Q

How does sevoflurane interact with CO2 absorbents?

A

Sevoflurane interacts with CO2 absorbents to generate Compound A which has been shown to cause renal injury in laboratory rodents

65
Q

What are the three factors which increase the risk of Compound A formation?

A

CO2 absorbents containing strong bases
Long duration of sevoflurane exposure
Low fresh gas flow

MODULE 14 - Patient Support (24 decks)

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