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Medical Specialties > Anaesthetics > Flashcards

Anaesthetics Flashcards

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USMLE® Step 1 flashcards
1
Q

what three components make up the anaesthetic triad?

A
  • relaxation
  • hypnosis
  • analgesia
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2
Q

what are the main classes of drugs used to provide the components of analgesia?

A
  • muscle relaxants
  • local anaesthetics
  • general anaesthetics
  • opiates
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3
Q

in anaesthetics, which classes of drugs achieve muscle relaxation?

A
  • muscle relaxants
  • local anaesthetics
  • general anaesthetics
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4
Q

in anaesthetics, which classes of drugs achieve hypnosis?

A
  • general anaesthetics

- opiates

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5
Q

in anaesthetics, which classes of drugs achieve analgesia?

A
  • local anaesthetics
  • opiates
  • (general anaesthetics)
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6
Q

what’s the name of the scoring system used to assess how fit a patient is for anaesthesia?

A

ASA classification

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7
Q

explain the concept of balanced anaesthesia

A

using small doses of two ore more agents instead of one large dose of a single agent

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8
Q

name some benefits balanced anaesthesia

A
  • lower risk of overdosage
  • different drugs do different jobs rather than one drug to do everything
  • flexibility
  • maintain low doses of separate drugs
  • alter dosages depending on necessity
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9
Q

what are some of the downsides of balanced anaesthesia?

A
  • polypharmacy: more drugs involved so higher risk of drug reactions
  • awareness: risk of patient being paralysed with insufficient analgesia
  • relaxation: paralysing skeletal muscles requires manual ventilation of patient
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10
Q

what two types of general anaesthesia exist?

A

intravenous and inhalational

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11
Q

what is the main mechanism of action of general anaesthetic agents?

A

hyperpolarisation of neurones

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12
Q

in general terms, what is the mechanism of action of inhalational anaesthetic agents?

A

interference with neuronal ion channels, dissolve in membrane - not entirely understood

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13
Q

in general terms, what is the mechanism of action of intravenous anaesthetic agents?

A

allosteric binding to GABA-ergic receptors: cause chloride channels to open

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14
Q

which general anaesthetic agents work quickly, and which ones slowly?

A

intravenous act quickly, inhalational act slowly

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15
Q

if given as a bolus, intravenous anaesthetic agents wear off after a few minutes. why?

A

highly fat soluble, cross through membranes: leave circulation quickly and effects wear off

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16
Q

after an initial bolus of intravenous anaesthetic is given, what happens to the molecules?

A

they leave the circulation and enter tissues, fat and muscle

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17
Q

where are intravenous anaesthetics metabolised?

A

in the liver

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18
Q

due to their fast action, what is the main purpose of intravenous anaesthetics?

A

they are mainly used for induction of anaesthesia

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19
Q

what are inhalational anaesthetics normally composed of?

A

halogenated hydrocarbons

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20
Q

how do inhalational anaesthetics reach their full effect?

A

a patient breathes in a gas mixture containing the anaesthetic until its concentration rises in the alveoli, then in the blood, lastly in the brain. once its concentration reaches a certain level in the brain, the patient becomes unconscious

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21
Q

what is the consequence of inhalational anaesthetics’ dependence on concentration gradients?

A

it is slow to take effect

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22
Q

due to their slow action, what is the main purpose of inhalational anaesthetics?

A

they are used mainly for the maintenance of anaesthesia, after the initial effect is achieved with an intravenous bolus

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23
Q

how is the effect of inhalational anaesthetics reversed?

A

anaesthetic gas is removed from gas mixture breathed by the patient, until molecules are breathed out again down a concentration gradient, from brain to blood to alveoli

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24
Q

why can general anaesthesia be likened to a drawn out resuscitation?

A
  • because the patient is unconscious
  • because cardio and respiratory systems are compromised
  • because it requires ABC monitoring throughout
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25
Q

in anaesthetics, what is MAC?

A

the minimum alveolar concentration required for an inhalational anaesthetic to cause effect

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26
Q

what does a low MAC value mean compared to a high MAC value in anaesthetics?

A

low MAC value - very potent anaesthetic

high MAC value - less potent anaesthetic

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27
Q

what is the most commonly used sequence for induction and maintenance of general anaesthetic?

A

intravenous anaesthetic for induction

inhalational anaesthetic for maintenance

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28
Q

how do general anaesthetics affect the cardiovascular system?

A

cause vasodilation - leads to reduced SVR, MAP, CO and preload
negative inotropic effect on heart - leads to reduced HR

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29
Q

how do general anaesthetics affect the respiratory system?

A

depress hypoxic and hypercarbic drive
reduce tidal volume
increase respiratory rate
reduce lung volumes: leads to VQ mismatch

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30
Q

why are patients given oxygen for a few days after surgery with general anaesthetic?

A

because general anaesthetic can reduce lung volumes for a prolonged period, causing VQ mismatch in the lungs

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31
Q

which anaesthetic agent is an exception and doesn’t depress the CVS and resp systems?

A

ketamine

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32
Q

respiratory depression caused by general anaesthetics results in reduced tidal volume and increased respiratory rate. how does this compare with opiate respiratory depression?

A

opiate respiratory depression maintains normal tidal wave and instead reduces respiratory rate

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33
Q

what is the main reason for the depressed cardiovascular function by general anaesthetics?

A
  • impact of cardiovascular and respiratory centres in the brainstem
  • reduced sympathetic drive
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34
Q

which area of the CNS is mainly affected by general anaesthetics, causing it to depress CVS and resp function?

A
  • cardiovascular and respiratory centres in the brainstem

- sympathetic system

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35
Q

what is the mechanism of action of muscle relaxants?

A

they block activity at the nicotinic cholinergic receptors at the NMJ

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36
Q

when are muscle relaxants required?

A

if procedure requires:

  • immobility
  • intubation/ventilation
  • body cavity access
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37
Q

name some of the complications that can arise from using muscle relaxants in anaesthesia

A
  • airway obstruction
  • reduced ventilation post-operatively
  • awareness
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38
Q

which components of the anaesthetic triad are achieved by general anaesthetics?

A
  • muscle relaxation
  • hypnosis
  • analgesia
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39
Q

which components of the anaesthetic triad are achieved by local anaesthetics?

A
  • muscle relaxation

- analgesia

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40
Q

which components of the anaesthetic triad are achieved by muscle relaxants?

A
  • relaxation
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41
Q

which components of the anaesthetic triad are achieved by opiates?

A
  • hypnosis

- analgesia

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42
Q

what is the mechanism of action of local and ragional anaesthesia?

A

blocks Na+ channels and stops action potential from propagating

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43
Q

what is the consequence of local anaesthesia’s mechanism of action?

A

it can have lots of side effects if administered wrongly

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44
Q

how should local anaesthetic be administered? what should always be avoided?

A

directly into the tissues or around the nerve bundle to be anaesthetised.
always avoid injecting intravenously

45
Q

how can intraoperative analgesia be beneficial?

A

it can reduce risk of reflex reactions
it can reduce risk of patient waking up
it can provide additional pain relief or hypnosis

46
Q

how can local and regional anaesthetics be beneficial?

A

preserves awareness
respiratory system spared
doesn’t have the same post-operative effects as general anaesthetic

47
Q

name a benefit and a downside to the use of local anaesthetic

A

benefit: differential blockade, will affect unmyelinated fibres more and thick myelinated motor fibres less
downside: absorption rate higher than metabolic rate - results in high plasma levels (toxicity)

48
Q

why can local and regional anaesthetics have a similar impact on CVS and resp to general anaesthetics?

A

because blockade can impact sympathetic bundles as well, depending on site of injection

49
Q

name a few types of regional/local anaesthesia

A

local anaesthetic
limb block
plexus block
neuraxial block (epidural, spinal)

50
Q

name some symptoms/signs of local anaesthetic toxicity

A 
lingual/oral numbness
visual and auditory disturbance
dizziness/lightheadedness
reduced CVS
metallic taste
drowsiness
convulsions
coma
51
Q

how is respiratory failure managed in critical care?

A

type 1 resp failure: high flow nasal cannulas
type 2 resp failure: non-invasive ventilation masks
unconscious/unable to breathe: intubation

52
Q

when is a patient intubated in HDU?

A

if they can’t breathe for themselves

if they are unconscious

53
Q

name two benefits of intubating a patient in terms of manipulating their breathing

A
  • you can tightly control the pressure of air going in

- you can control the amount of oxygen

54
Q

name two downsides of intubating a patient in critical care

A
  • patient may get ARDS if intubated at too high a pressure for too long
  • patient can only tolerate intubation if unconscious
55
Q

which type of shock is most commonly seen in critical care?

A

septic shock

56
Q

how is cardiovascular failure managed in critical care?

A
  • fluids
    if fluids don’t work:
  • vasopressors to cause vasoconstriction
  • positive inotropes to increase heart contractility
57
Q

which vasopressors are administered in critical care for patients in cardiovascular failure?

A

metaraminol

noradrenaline

58
Q

which inotropes are administered in critical care for patients in cardiovascular failure?

A

adrenaline

dobutamine

59
Q

what is the difference between crystalloid fluids and colloid fluids?

A

crystalloids: contain small molecules
colloids: contain large molecules

60
Q

what is given to resuscitate a patient with cardiovascular failure in critical care?

A

plasmaLyte

61
Q

what is plasmaLyte?

A

a crystalloid solution similar to human plasma given in critical care to resuscitate patients in cardiovascular failure

62
Q

what are some signs you can look for to tell if a patient is in neurological failure?

A

uneven pupils
cushing’s reflex (bradychardia, HTN, irregular breathing)
GCS <8

63
Q

how is neurological failure managed in critical care?

A

supportive measures until specialists arrive

maintain temperature, O2, CO2, glucose, BP

64
Q

which three main organ failures are managed in critical care?

A

respiratory failure
cardiovascular failure
neurological failure

65
Q

in which cases is gas anaesthetic induction given to patients prior to surgery?

A

in children

in adults with special needs

66
Q

what are the main ways to maintain a patent airway when general anaesthesia is induced?

A
  • triple airway manoeuvre (head tilt, chin lift, jaw thrust)
  • face masks
  • intubation (oropharyngeal, laryngeal, nasotracheal)
67
Q

name some factors which are monitored by an anaesthetist during surgery

A 
ECG
BP
temperature
NMJ
urine output
anaesthesia levels
glucose
EEG
O2/CO2
68
Q

name the planes of anaesthesia

A

analgesia/sedation
excitation
anaesthesia (light to deep)
overdose

69
Q

why is it important to have a dedicated recovery area after surgery?

A

to monitor the patient’s CVS and resp system before discharge to ward/home

70
Q

name a few ways to monitor the level of anaesthesia after induction

A 
loss of verbal contact
loss of movement
respiratory rate
EEG
planes of anaesthesia
71
Q

with which anaesthetic induction are the planes of anaesthesia more noticeable?

A

with inhalation anaesthetic induction

72
Q

which drugs are commonly used to induce IV and inhalation general anaesthesia?

A

IV - propofol

inhalation - halothane

73
Q

what is the difference between maintaining an airway and protecting an airway?

A

maintaining - maintaining patency of airway

protecting - avoiding aspiration during anaesthesia

74
Q

in what order is general anaesthetic reversed at the end of the procedure?

A
  • muscle relaxants reversed
  • anaesthetic agents removed
  • airway control returns
  • extubation
75
Q

list some reasons for why pre-ops are important

A
  • patient assessment
  • identify high risk patients
  • optimisation of comorbidities
  • minimise risk
  • informed consent
76
Q

what information from the history is important to obtain in a surgery pre-op?

A
  • PMHx and control
  • risk factors
  • DHx and allergies
  • past surgery/anaesthesia
77
Q

what information from the clinical examination is important to obtain in a surgery pre-op?

A

Heart function
Lung function
Kidney function

78
Q

why is it important to check heart and lung function in a pre-op assessment?

A

important to assess patient’s ability to withstand stress of surgery

79
Q

name some potential anaesthetic complications that can be obtained from the history

A 
obesity
airway problems
reflux
spine problems
familial conditions
80
Q

explain the concept of optimising in the context of pre-op patient assessment

A

ensuring optical medical control of comorbidities prior to surgery

81
Q

explain the concept of minimising risk in the context of pre-op patient assessment

A

reducing chance of complications by addressing co-morbidities and risk factors

82
Q

what anaesthetic classifications can be used to predict the extent of pre-op investigations needed for a patient?

A

ASA score
Cardiac risk Index
Surgery grade

83
Q

what is the importance of MET scores in anaesthesia?

A

measures level of exercise tolerance - the higher the MET, the higher the ability to withstand stress of surgery

84
Q

what is the importance of Cardiac Index in anaesthesia?

A

measures level of cardiac fitness - identifies high risk patients

85
Q

what is pre-abilitation?

A

increasing a patient’s fitness prior to surgery to maximise their ability to withstand stress during surgery

86
Q

why is it important to stop smoking cannabis prior to surgery?

A

because it can cause bullae to form in the lungs - can lead to pneumothorax

87
Q

why is it important to stop drinking alcohol prior to surgery?

A

because it carries a higher risk of infection and sepsis

88
Q

why is it important to lose weight prior to surgery?

A

to reduce infection and cardiovascular risk

89
Q

why is it important to increase exercise prior to surgery?

A

improved fitness leads to higher ability to withstand stress of surgery

90
Q

which medications are stopped prior to surgery?

A

anticoagulants

diabetic medication

91
Q

what is the difference between nociceptive and neuropathic pain?

A

nociceptive pain is a physiological response to a painful stimulus, whereas neuropathic pain is an abnormal pain signal caused by nerve damage

92
Q

which type of pain doesn’t always have physical evidence of tissue damage?

A

neuropathic pain

93
Q

does neuropathic pain normally respond to traditional pain medication eg paracetamol and NSAIDS?

A

no

94
Q

can tramadol be safely used alongside simple analgesics?

A

yes

95
Q

what are the two main disadvantages to morphine?

A

constipation

addiction

96
Q

how do tricyclic antidepressants (eg amitriptyline) reduce pain?

A

amitryptiline reduces pain by increasing the inhibitory pathway

97
Q

why are anticonvulsants good for neuropathic pain?

A

because they are membrane stabilisers, so will stop abnormal nerve firing

98
Q

what are the main non-drug methods to reduce pain at peripheral level?

A

RICE: rest, ice, elevation

99
Q

what are the main non-drug treatments to reduce pain at spinal level?

A

TENS, acupuncture, massage

100
Q

what is the main non-drug treatment to reduce pain at brain level?

A

psychology

101
Q

what is the theory behind spinal level non-pharmacological treatments?

A

gate theory - massages and TENS will “distract” the brain from the noxious stimulus

102
Q

how should a patient on long-term tramadol be taken off it?

A

taper down the dose, immediate cessation causes severe withdrawal

103
Q

describe the three steps of the pain relief ladder

A

step 1: non-opioids
step 2: mild opioids +/- non-opioids
step 3: strong opioids +/- non-opioids

104
Q

give examples of pain treatment for the first step in the pain relief ladder

A

paracetamol
aspirin
NSAIDS

105
Q

give examples of pain treatment for the second step in the pain relief ladder

A

codeine
co-codamol
tramadol

106
Q

give examples of pain treatment for the third step in the pain relief ladder

A

morphine

107
Q

can the pain relief ladder be used in the treatment of neuropathic pain?

A

no

108
Q

give examples of pain treatment for neuropathic pain

A

amitryptiline
gabapentin
duloxetine

109
Q

what is the best approach to decide what type of pain management to put someone on?

A

RAT approach:
Recognise
Assess
Treat

Medical Specialties (4 decks)

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