L31 - general anaesthetics Flashcards
1
Q
triad of balanced general anaesthesia
A
amnesia
analgesia
akinesis
2
Q
amnesia
A
lack of response and recall to noxious stimuli - unconsciousness
3
Q
analgesia
A
pain relief
4
Q
akinesis
A
muscle relaxation / paralysis
5
Q
general anaesthesia
A
total loss of sensation
6
Q
brain arm circulation time
A
time it takes for drug to travel from site of injection to brain
10-20s
7
Q
how many brain arm circulation times induce loss of consciousness
A
2
8
Q
IV agents for amnesia drugs
A
- quick onset
- short duration (terminates due to redistribution from muscle to fat)
9
Q
Cp50
A
the concentration of the agent in the blood that prevents movement after a skin incision in 50% of patients
10
Q
timeline of events
A
- monitoring
- IV access to give anaesthetic agents
- start the process
- maintain the process
- reverse the process
11
Q
what do IV GAs do
A
- hyperpolarise nerve cells, preventing conduction of action potentials alone neurones
12
Q
action of GAs on inhibitory and excitatory neurones
A
- excite inhibitory neurones
- inhibit excitatory neurones
13
Q
ideal properties of IV induction agents
A
- Simple preparation
- Compatible with other agents and IV fluids
- Painless on administration
- High potency and efficacy
- Predictable action within one circulation time
- Minimal cardiovascular effects or other toxicity
- Depression of airway reflexes for intubation
- Rapid and predictable offset of effect
- Rapid metabolism for minimal hangover
14
Q
most common IV induction agent
A
propofol
15
Q
propofol
A
- lipid based
- excellent suppression of airway reflexes (prevents gag reflex or vomiting when equipment inserted into mouth)
- decreases incidence of post-op nausea and vomiting (PONV)
16
Q
unwanted effects of propofol
A
- marked drop in HR and BO
- pain on injection
- involuntary movements
17
Q
thiopentone
A
- barbiturate (anti-epileptic properties)
- faster than propofol
- used for rapid sequence induction
- protects brain
18
Q
unwanted effects of thiopentone
A
- drops BP and increases HR
- rash / bronchospasm
- intra-arterial injection (thrombosis and gangrene as travels up arteries and blocks blood flow)
19
Q
best drug for minor procedures
A
ketamine
muscle relaxation not required
20
Q
ketamine
A
- dissociative anaesthesia
- slow onset (90s)
- rise in HR/BP
- bronchodilation
21
Q
unwanted effects of ketamine
A
- nausea and vomiting
- emergence phenomenon
22
Q
dose of propofol used
A
1.5-2.5mg/kg
23
Q
dose of thiopentone used
A
4-5mg/kg
24
Q
dose of ketamine used
A
1-1.5mg/kg
25
drug with the quickest onset
etomidate
26
dose of etomidate
0.3mg/kg
27
lowest incidence of hypersensitivity reaction
etomidate since it is steroid based
28
unwanted effects of etomidate
- pain on injection
- spontaneous movements
- adrenal-cortical suppression
- high incidence of PONV
29
how to maintain amnesia
- propofol induction (total IV anaesthesia)
| - inhalation agents (inhalation anaesthesia)
30
how long do amnesia induction agents last without maintaining them
4-10mins
31
when to give amnesia agents (Vapours)
immediately after induction
32
how are amnesia agents administered
vaporisers
| breathing circuits
33
physical properties of the ideal inhalation agent for amnesia
- non-flammable
- stable
- long shelf life
- environmentally friendly
- cheap and easy to manufacture
34
biological properties for the idea inhalation agent for amnesia
- pleasant to inhale
- non-irritant
- fast onset
- high potency
- minimal effect on other systems
- no biotransformation
- non-toxic to theatre personnel
35
neurological effects of anaesthetics
amnesia
hypnosis
immobility
36
agents of amnesia
isoflurane
sevoflurane
desflurane
37
MAC
concentration of the vapour which prevents the reaction to the standard surgical stimulus in 50% of patients
38
what does a low solubility of a GA mean
fast equilibrium = fast recovery
39
what does a highly fat soluble GA mean
GA given for a long time accumulates in far = hangover effect for hours
40
sevoflurane
- sweet smelling
| - inhalation induction
41
desflurane
- low lipid solubility
- rapid onset and offset
- long operations
42
isoflurane
- least effect on organ blood flow
43
adverse effects on amnesic agents
- vasodilation
- decrease cardiac contractility
- can affect organ perfusion
- malignant hyperthermia
- hepatotoxicity
44
preferred inhalation amnesic agent for a long surgery
desflurane
45
preferred inhalation amnesic agent for a chubby child with no IV access
sevoflurane
46
preferred inhalation amnesic agent for an organ retrieval from a donor
isoflurane
47
what is analgesia required for
- insertion of airway
- laryngeal mask airway
- intubaiton
- intra-op pain relief
- post-op pain relief
48
akinesis
muscle relaxant required for intubation and surgery
49
depolarising akinesia agent
suxamethonium
50
non-depolarising akinesia agent
short acting: mivacurium
intermediate acting: vecoronium
long acting: pancoronium
51
assessing unconsciousness
- lineal signs
- measure MAC
- BIS monitor
- isolated forearm
- Evoked potentials
52
BIS monitor
A bispectral index (BIS) monitor is commonly utilized to assess depth of sedation when administering sedative, hypnotic, or anesthetic agents during surgical and medical procedures. The depth of sedation is calculated by measuring cerebral electric activity via an electroencephalogram (EEG).
53
most commonly used opioid induction agent
Fentanyl
54
Best Induction agent for a patient with a history of heart failure requires a general anaesthetic
Etomidate
| as causes least harm-dynamic changes
55
best induction agent for a burn change
ketamine
56
Best Induction agent for a patient undergoing arm operation under GA with an laryngeal mask airway (LMA).
propofol
| as it causes suppression of airway reflexes
57
what does MAC stand for
Minimum alveolar concentration
58
Most commonly used non-opiod analgesic agent in anaesthesia is
paracetamol
