General anaesthetics Flashcards
Objective of anaesthesia?
Inducing a lack of feeling (lack of sensation and pain)
Who was the father of surgical anaesthesia?
Hua Tuo
Who was the first surgeon who used N2O as a GA?
Crawford Long
Triad of general anaesthetics?
Unconsciousness, analgesia, muscle relaxation
How many stages of anaesthesia are there?
4
What is stage 1 of anaesthesia?
Analgesia
Conditions of stage 1 of anaesthesia?
conscious, drowsy, anticonception, amnesia
What is stage 2 of anaesthesia?
Excitement
Conditions of stage 2 of anaesthesia?
loss of consciousness, delirium, irregular cardiorespiration, apnea, spasticity, gagging, vomiting
What is stage 3 of anaesthesia?
Anaesthesia
Conditions of stage 3 of anaesthesia?
regular respiration, loss of reflex and muscle tone
What is stage 4 of anaesthesia?
medullary paralysis
Conditions of stage 4 of anaesthesia?
Depression of cardiorespiration, death
Why is stage 1 of GA used for childbirth?
Want some lack of sensation but still need to be awake
How do you go from one stage of GA to a higher stage?
Increase the dose or potency of the GA
Which compound is used to induce stage 1 GA?
N2O
Which stage of GA causes erratic breathing?
2
What is a warning sign to an anaesthetist that a patient is too deeply anaesthetised?
Action of intercostal muscles decreasing
What are the four stages of stage 3 of GA?
Planes 1,2,3, and 4
When is the pupilary light reflex visible?
S3, planes 2-end of 3
When during GA does the corneal reflex stop?
S3P2
Precise aim of GA?
S3, P1 OR 2
When in GA is the respiratory response to skin inscision lost?
Midway through S3P2
When during GA are the muscles tense and struggling?
S2
Super ideal GA?
Stable, potent, non toxic, controllable, rapid on off, adjustable, minimal cardio and respiratory depressant
Why does the ideal GA need to be rapid on?
Through S2 quickly
Why does the ideal GA need to be rapid off?
Able to titrate dose depending on their reaction, to keep them in S3
Why is xenon not used as a GA?
V expensive
2 main types of administering GAs?
Inhalation and intravenous
Best aspect of inhaled GAs?
V controllable as the dose in the air is v quickly transferred
Main inhaled GAs?
Halogenated ethers, halogenated hydrocarbons
Halogenated hydrocarbon example?
Halothane, isofluorane
Advantages of halothane and isoflurane?
V potent and stable
Main pro of intravenous GAs?
V rapid
Which type of general anaesthetic is used for induction of GA?
Intravenous
Which type of anaesthetic is used for maintenance of GA?
Inhaled
Major surgery general anaesthetic order?
Benzazepine, then intravenous (thiopental), then inhaled (halothane)
Rapid unconsciousness anaesthetic?
thiopental (short acting)
General anaesthetic to maintain GA?
N2O, halothane, sevofluorane
When are analgesic drugs used?
post operative care
What is fentanyl used for?
analgesic effect after surgery when the general anaesthetic has worn off
Which compounds are used for paralysis of skeletal muscle?
Suxamethonium
How does Suxamethonium work?
It is a nicotinic ACh receptor antagonist
What drugs are people given pre-op?
Benzodiazepines, midazolam
Examples of inhaled anaesthetics?
N2O, halothane, enflurane, isoflurane, desflurane, sevoflurane
Side effect of halothane?
Toxic to liver
Which inhaled GA is used more in veterinary than human surgery?
Halothane
Why is sevoflurane used the most?
Has the least side effects
Types of intravenous GAs?
Thiopental, etomidate, propofol, ketamine, benzodiazepines
Most widely used intravenous GA?
propofol
Mechanism of local anaesthetics?
Voltage-gated sodium channel block
Two main theories of how GAs work?
lipid theory, and protein theory
Lipid theory of GAs?
good GAs are more lipophilic (can soak into lipids) and so soak into the lipid bilayer and block membrane spanning proteins (Na+ channels in neurons etc)
Protein theory of GAs?
More potent a GA is, less of it is needed to inhibit luciferase proteina action, so GAs might generally inhibit protein action
What type of proteins do GAs target?
Transmitter receptors, ion channels, transporters and release
What do GAs do regarding inhibitory receptors?
Potentiate them, meaning they are stronger (more hyperpolarisation)
What do GAs to to excitatory receptors?
Block them
How do GAs affect ion channels?
They reduce the frequency of them opening
