Anaesthetics Flashcards
1
Q
what three components make up the anaesthetic triad?
A
- relaxation
- hypnosis
- analgesia
2
Q
what are the main classes of drugs used to provide the components of analgesia?
A
- muscle relaxants
- local anaesthetics
- general anaesthetics
- opiates
3
Q
in anaesthetics, which classes of drugs achieve muscle relaxation?
A
- muscle relaxants
- local anaesthetics
- general anaesthetics
4
Q
in anaesthetics, which classes of drugs achieve hypnosis?
A
- general anaesthetics
- opiates
5
Q
in anaesthetics, which classes of drugs achieve analgesia?
A
- local anaesthetics
- opiates
- (general anaesthetics)
6
Q
what’s the name of the scoring system used to assess how fit a patient is for anaesthesia?
A
ASA classification
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
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
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
10
Q
what two types of general anaesthesia exist?
A
intravenous and inhalational
11
Q
what is the main mechanism of action of general anaesthetic agents?
A
hyperpolarisation of neurones
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
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
14
Q
which general anaesthetic agents work quickly, and which ones slowly?
A
intravenous act quickly, inhalational act slowly
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
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
17
Q
where are intravenous anaesthetics metabolised?
A
in the liver
18
Q
due to their fast action, what is the main purpose of intravenous anaesthetics?
A
they are mainly used for induction of anaesthesia
19
Q
what are inhalational anaesthetics normally composed of?
A
halogenated hydrocarbons
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
21
Q
what is the consequence of inhalational anaesthetics’ dependence on concentration gradients?
A
it is slow to take effect
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
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
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
25
in anaesthetics, what is MAC?
the minimum alveolar concentration required for an inhalational anaesthetic to cause effect
26
what does a low MAC value mean compared to a high MAC value in anaesthetics?
low MAC value - very potent anaesthetic
| high MAC value - less potent anaesthetic
27
what is the most commonly used sequence for induction and maintenance of general anaesthetic?
intravenous anaesthetic for induction
| inhalational anaesthetic for maintenance
28
how do general anaesthetics affect the cardiovascular system?
cause vasodilation - leads to reduced SVR, MAP, CO and preload
negative inotropic effect on heart - leads to reduced HR
29
how do general anaesthetics affect the respiratory system?
depress hypoxic and hypercarbic drive
reduce tidal volume
increase respiratory rate
reduce lung volumes: leads to VQ mismatch
30
why are patients given oxygen for a few days after surgery with general anaesthetic?
because general anaesthetic can reduce lung volumes for a prolonged period, causing VQ mismatch in the lungs
31
which anaesthetic agent is an exception and doesn't depress the CVS and resp systems?
ketamine
32
respiratory depression caused by general anaesthetics results in reduced tidal volume and increased respiratory rate. how does this compare with opiate respiratory depression?
opiate respiratory depression maintains normal tidal wave and instead reduces respiratory rate
33
what is the main reason for the depressed cardiovascular function by general anaesthetics?
- impact of cardiovascular and respiratory centres in the brainstem
- reduced sympathetic drive
34
which area of the CNS is mainly affected by general anaesthetics, causing it to depress CVS and resp function?
- cardiovascular and respiratory centres in the brainstem
| - sympathetic system
35
what is the mechanism of action of muscle relaxants?
they block activity at the nicotinic cholinergic receptors at the NMJ
36
when are muscle relaxants required?
if procedure requires:
- immobility
- intubation/ventilation
- body cavity access
37
name some of the complications that can arise from using muscle relaxants in anaesthesia
- airway obstruction
- reduced ventilation post-operatively
- awareness
38
which components of the anaesthetic triad are achieved by general anaesthetics?
- muscle relaxation
- hypnosis
- analgesia
39
which components of the anaesthetic triad are achieved by local anaesthetics?
- muscle relaxation
| - analgesia
40
which components of the anaesthetic triad are achieved by muscle relaxants?
- relaxation
41
which components of the anaesthetic triad are achieved by opiates?
- hypnosis
| - analgesia
42
what is the mechanism of action of local and ragional anaesthesia?
blocks Na+ channels and stops action potential from propagating
43
what is the consequence of local anaesthesia's mechanism of action?
it can have lots of side effects if administered wrongly
44
how should local anaesthetic be administered? what should always be avoided?
directly into the tissues or around the nerve bundle to be anaesthetised.
always avoid injecting intravenously
45
how can intraoperative analgesia be beneficial?
it can reduce risk of reflex reactions
it can reduce risk of patient waking up
it can provide additional pain relief or hypnosis
46
how can local and regional anaesthetics be beneficial?
preserves awareness
respiratory system spared
doesn't have the same post-operative effects as general anaesthetic
47
name a benefit and a downside to the use of local anaesthetic
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
why can local and regional anaesthetics have a similar impact on CVS and resp to general anaesthetics?
because blockade can impact sympathetic bundles as well, depending on site of injection
49
name a few types of regional/local anaesthesia
local anaesthetic
limb block
plexus block
neuraxial block (epidural, spinal)
50
name some symptoms/signs of local anaesthetic toxicity
```
lingual/oral numbness
visual and auditory disturbance
dizziness/lightheadedness
reduced CVS
metallic taste
drowsiness
convulsions
coma
```
51
how is respiratory failure managed in critical care?
type 1 resp failure: high flow nasal cannulas
type 2 resp failure: non-invasive ventilation masks
unconscious/unable to breathe: intubation
52
when is a patient intubated in HDU?
if they can't breathe for themselves
| if they are unconscious
53
name two benefits of intubating a patient in terms of manipulating their breathing
- you can tightly control the pressure of air going in
| - you can control the amount of oxygen
54
name two downsides of intubating a patient in critical care
- patient may get ARDS if intubated at too high a pressure for too long
- patient can only tolerate intubation if unconscious
55
which type of shock is most commonly seen in critical care?
septic shock
56
how is cardiovascular failure managed in critical care?
- fluids
if fluids don't work:
- vasopressors to cause vasoconstriction
- positive inotropes to increase heart contractility
57
which vasopressors are administered in critical care for patients in cardiovascular failure?
metaraminol
| noradrenaline
58
which inotropes are administered in critical care for patients in cardiovascular failure?
adrenaline
| dobutamine
59
what is the difference between crystalloid fluids and colloid fluids?
crystalloids: contain small molecules
colloids: contain large molecules
60
what is given to resuscitate a patient with cardiovascular failure in critical care?
plasmaLyte
61
what is plasmaLyte?
a crystalloid solution similar to human plasma given in critical care to resuscitate patients in cardiovascular failure
62
what are some signs you can look for to tell if a patient is in neurological failure?
uneven pupils
cushing's reflex (bradychardia, HTN, irregular breathing)
GCS <8
63
how is neurological failure managed in critical care?
supportive measures until specialists arrive
| maintain temperature, O2, CO2, glucose, BP
64
which three main organ failures are managed in critical care?
respiratory failure
cardiovascular failure
neurological failure
65
in which cases is gas anaesthetic induction given to patients prior to surgery?
in children
| in adults with special needs
66
what are the main ways to maintain a patent airway when general anaesthesia is induced?
- triple airway manoeuvre (head tilt, chin lift, jaw thrust)
- face masks
- intubation (oropharyngeal, laryngeal, nasotracheal)
67
name some factors which are monitored by an anaesthetist during surgery
```
ECG
BP
temperature
NMJ
urine output
anaesthesia levels
glucose
EEG
O2/CO2
```
68
name the planes of anaesthesia
analgesia/sedation
excitation
anaesthesia (light to deep)
overdose
69
why is it important to have a dedicated recovery area after surgery?
to monitor the patient's CVS and resp system before discharge to ward/home
70
name a few ways to monitor the level of anaesthesia after induction
```
loss of verbal contact
loss of movement
respiratory rate
EEG
planes of anaesthesia
```
71
with which anaesthetic induction are the planes of anaesthesia more noticeable?
with inhalation anaesthetic induction
72
which drugs are commonly used to induce IV and inhalation general anaesthesia?
IV - propofol
| inhalation - halothane
73
what is the difference between maintaining an airway and protecting an airway?
maintaining - maintaining patency of airway
| protecting - avoiding aspiration during anaesthesia
74
in what order is general anaesthetic reversed at the end of the procedure?
- muscle relaxants reversed
- anaesthetic agents removed
- airway control returns
- extubation
75
list some reasons for why pre-ops are important
- patient assessment
- identify high risk patients
- optimisation of comorbidities
- minimise risk
- informed consent
76
what information from the history is important to obtain in a surgery pre-op?
- PMHx and control
- risk factors
- DHx and allergies
- past surgery/anaesthesia
77
what information from the clinical examination is important to obtain in a surgery pre-op?
Heart function
Lung function
Kidney function
78
why is it important to check heart and lung function in a pre-op assessment?
important to assess patient's ability to withstand stress of surgery
79
name some potential anaesthetic complications that can be obtained from the history
```
obesity
airway problems
reflux
spine problems
familial conditions
```
80
explain the concept of optimising in the context of pre-op patient assessment
ensuring optical medical control of comorbidities prior to surgery
81
explain the concept of minimising risk in the context of pre-op patient assessment
reducing chance of complications by addressing co-morbidities and risk factors
82
what anaesthetic classifications can be used to predict the extent of pre-op investigations needed for a patient?
ASA score
Cardiac risk Index
Surgery grade
83
what is the importance of MET scores in anaesthesia?
measures level of exercise tolerance - the higher the MET, the higher the ability to withstand stress of surgery
84
what is the importance of Cardiac Index in anaesthesia?
measures level of cardiac fitness - identifies high risk patients
85
what is pre-abilitation?
increasing a patient's fitness prior to surgery to maximise their ability to withstand stress during surgery
86
why is it important to stop smoking cannabis prior to surgery?
because it can cause bullae to form in the lungs - can lead to pneumothorax
87
why is it important to stop drinking alcohol prior to surgery?
because it carries a higher risk of infection and sepsis
88
why is it important to lose weight prior to surgery?
to reduce infection and cardiovascular risk
89
why is it important to increase exercise prior to surgery?
improved fitness leads to higher ability to withstand stress of surgery
90
which medications are stopped prior to surgery?
anticoagulants
| diabetic medication
91
what is the difference between nociceptive and neuropathic pain?
nociceptive pain is a physiological response to a painful stimulus, whereas neuropathic pain is an abnormal pain signal caused by nerve damage
92
which type of pain doesn't always have physical evidence of tissue damage?
neuropathic pain
93
does neuropathic pain normally respond to traditional pain medication eg paracetamol and NSAIDS?
no
94
can tramadol be safely used alongside simple analgesics?
yes
95
what are the two main disadvantages to morphine?
constipation
| addiction
96
how do tricyclic antidepressants (eg amitriptyline) reduce pain?
amitryptiline reduces pain by increasing the inhibitory pathway
97
why are anticonvulsants good for neuropathic pain?
because they are membrane stabilisers, so will stop abnormal nerve firing
98
what are the main non-drug methods to reduce pain at peripheral level?
RICE: rest, ice, elevation
99
what are the main non-drug treatments to reduce pain at spinal level?
TENS, acupuncture, massage
100
what is the main non-drug treatment to reduce pain at brain level?
psychology
101
what is the theory behind spinal level non-pharmacological treatments?
gate theory - massages and TENS will "distract" the brain from the noxious stimulus
102
how should a patient on long-term tramadol be taken off it?
taper down the dose, immediate cessation causes severe withdrawal
103
describe the three steps of the pain relief ladder
step 1: non-opioids
step 2: mild opioids +/- non-opioids
step 3: strong opioids +/- non-opioids
104
give examples of pain treatment for the first step in the pain relief ladder
paracetamol
aspirin
NSAIDS
105
give examples of pain treatment for the second step in the pain relief ladder
codeine
co-codamol
tramadol
106
give examples of pain treatment for the third step in the pain relief ladder
morphine
107
can the pain relief ladder be used in the treatment of neuropathic pain?
no
108
give examples of pain treatment for neuropathic pain
amitryptiline
gabapentin
duloxetine
109
what is the best approach to decide what type of pain management to put someone on?
RAT approach:
Recognise
Assess
Treat
