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Flashcards in Volatile anaesthetic agents Deck (80)
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1
Q

What is the molecular weight of halothane?

A

197

2
Q

What is the molecular weight of isoflurane?

A

184.5

3
Q

What is the molecular weight of enflurane?

A

184.5

4
Q

What is the molecular weight of desflurane?

A

168

5
Q

What is the molecular weight of sevoflurane?

A

200.1

6
Q

What is the molecular weight of nitrous oxide?

A

44

7
Q

What is the molecular weight of xenon?

A

131

8
Q

What is the boiling point of halothane?

A

50.2

9
Q

What is the boiling point of isoflurane?

A

48.5

10
Q

What is the boiling point of enflurane?

A

56.5

11
Q

What is the boiling point of desflurane?

A

23.5

12
Q

What is the boiling point of sevoflurane?

A

58.5

13
Q

What is the boiling point of nitrous oxide?

A

-88

14
Q

What is the boiling point of xenon?

A

-108

15
Q

What is the SVP of halothane?

A

32.3

16
Q

What is the SVP of isoflurane?

A

33.2

17
Q

What is the SVP of enflurane?

A

23.3

18
Q

What is the SVP of desflurane?

A

89.2

19
Q

What is the SVP of sevoflurane?

A

22.7

20
Q

What is the SVP of nitrous oxide?

A

5200

21
Q

What is the SVP of xenon?

A

unknown

22
Q

What is the MAC of halothane?

A

0.75

23
Q

What is the MAC of isoflurane?

A

1.17

24
Q

What is the MAC of enflurane?

A

1.68

25
Q

What is the MAC of desflurane?

A

6.6

26
Q

What is the MAC of sevoflurane?

A

1.8-2.2

27
Q

What is the MAC of nitrous oxide?

A

105

28
Q

What is the MAC of xenon?

A

71

29
Q

What is the blood:gas partition coefficient of halothane?

A

2.4

30
Q

What is the blood:gas partition coefficient of isoflurane?

A

1.4

31
Q

What is the blood:gas partition coefficient of enflurane?

A

1.8

32
Q

What is the blood:gas partition coefficient of desflurane?

A

0.42

33
Q

What is the blood:gas partition coefficient of sevoflurane?

A

0.7

34
Q

What is the blood:gas partition coefficient of nitrous oxide?

A

0.47

35
Q

What is the blood:gas partition coefficient of xenon?

A

0.14

36
Q

What is the blood:oil partition coefficient of halothane?

A

224

37
Q

What is the blood:oil partition coefficient of isoflurane?

A

98

38
Q

What is the blood:oil partition coefficient of enflurane?

A

98

39
Q

What is the blood:oil partition coefficient of desflurane?

A

29

40
Q

What is the blood:oil partition coefficient of sevoflurane?

A

80

41
Q

What is the blood:oil partition coefficient of nitrous oxide?

A

1.4

42
Q

What is the blood:oil partition coefficient of xenon?

A

1.9

43
Q

What is the odour of halothane?

A

Sweet

44
Q

What is the odour of isoflurane?

A

Irritant

45
Q

What is the odour of enflurane?

A

non-irritant

46
Q

What is the odour of desflurane?

A

Pungent

47
Q

What is the odour of sevoflurane?

A

non-irritant

48
Q

What is the odour of nitrous oxide?

A

odourless

49
Q

What is the odour of xenon?

A

odourless

50
Q

Which factors increase MAC?

A

Infancy Hyperthermia Hyperthyroidism Catecholamines Sympathomimetics Chronic EtOH Chronic opiate use Acute amphetamine use Hypernatraemia

51
Q

Which factors decrease MAC?

A

Neonatal period Advanced age Pregnancy Hypotension Hypothermia Hypothyroidism Alpha-2 agonists Sedatives Acute EtOH Acute opiate use Chronic amphetamine use Lithium

52
Q

Which factors decrease the time taken to reach equilibrium of anaesthetic agent?

A

Increased alveolar ventilation Decreased FRC Increased FiAA Reduced cardiac output Reduced blood:gas partition coefficient Second gas effect

53
Q

Which metabolic system is responsible for metabolising the C-(halogen) bond?

A

CYP450

54
Q

In which order do volatile agents affect cardiac contractility (most -> least)

A

Halothane > Enflurane > Isoflurane > Sevoflurane > Desflurane

55
Q

What is xenon?

A

An inert, odourless, noble gas that makes up about 8.7 x10-6% of the atmosphere.

56
Q

How is xenon produced?

A

By fractional distillation of air

57
Q

How expensive is xenon?

A

Very. Over 2000x the cost of an equivalent amount of N20

58
Q

What is the atomic number of xenon?

A

54

59
Q

What is the critical temperature of xenon?

A

16.6

60
Q

What is the mechanism of action of xenon?

A

Inhibition of glutamate at the NMDA receptor producing anaesthesia and analgesia. Also blocks 5HT3 receptors, although is hasn’t been shown to have an effect on PONV.

61
Q

What are the effects of xenon on the cardiovascular system?

A

Minimal effects on CO, although mildly vagolytic producing a small decrease in HR. Has some ischaemic preconditioning properties

62
Q

What are the effects of xenon on the respiratory system?

A

Reduction in RR Increase in TV Overall unchanged MV Will produce apnoea in high enough concentration

63
Q

What are the effects of xenon on the CNS?

A

Likely neuroprotective Small variable increases in CBR, so not recommended for neurosurgery.

64
Q

What is the critical pressure of N2O?

A

72 bar

65
Q

Is N2O a vapour or a gas?

A

Both, it is inhaled as a vapour, and exhaled as a gas.

66
Q

How is N2O produced?

A

Thermal decomposition of ammonium nitrate (NH4NO3) at 250°C

67
Q

What other compounds are produced alongside N2O?

A

Nitric oxide Ammonia Nitrogen dioxide Nitrogen Nitric acid Water

68
Q

How are the unwanted side products removed during N2O production

A

Acid/Alkali wash.

69
Q

How is N2O stored?

A

As a liquid with a pressure of 52 bar (the SVP of the vapour above the liquid)

70
Q

What colour cylinders are used to store N2O?

A

French blue

71
Q

Define filling ratio?

A

The ratio of the mass of liquid N2O compared to if filled with water.

72
Q

What is the filling ratio of N2O?

A

0.75 in the UK 0.67 in the tropics

73
Q

What is the mechanism of action of N2O

A

Inhibition of NMDA receptor resulting in analgesia and sedation.

74
Q

What are the effects of N2O on the cardiovascular system?

A

Decreased myocardial contractility offset by increase in central sympathetic outflow. In heart failure this can cause decompensation. No sensitisation to catecholamines.

75
Q

What are the effects of N2O on the respiratory system?

A

Small reduction in TV Small increase in RR no net change in MV

76
Q

What are the effects of N2O on the CNS?

A

Increase in CRF and CMRO2 - avoid in neurosurgery and head injury.

77
Q

Give some undesirable side effects of N2O.

A

Inhibition of B12 -> The cobalt ion at the centre of B12 is oxidised making it unsuitable to act as a cofactor in methionine synthesise. This can lead to reduced DNA synthesis and megaloblastic anaemia. Subacute combined degeneration of the cord occurs by a similar mechanism.

78
Q

What is entonox?

A

a 50:50 mix of N2O and O2

79
Q

How is entonox stored?

A

French blue cylinders with a white and blue checkered shoulder at 137 bar

80
Q

What is the metabolism of isoflurane?

A

0.2%