Anaesthetics Flashcards
What is the difference between local and general
General loses sense of consciousness aswell as sensation/pain
What 2 types of general anaesthetics are there
Inhalation
IV
What is the lipid theory to how anaesthetics work
They interact with the lipid bilayer and cause membrane expansion which disrupts protein signalling
What is the ion channel theory
They target ligand channels like gaba and nmda
What does blood/gas partition coefficient mean for inhaled anaesthetics
How blood soluble the anaesthetic is
What does it mean if a drug has high blood/gas partition coefficient
They are very soluble in blood
Causing slow induction and recovery
What happens if a drug has a lower blood gas partition coefficient
Faster induction (less drug needed) and also fast recovery
What is oil/gas partition coefficient mean for inhalation anaesthetics
How lipid soluble the drug is
What happens if anaesthetics have a higher oil/gas partition coefficient
High lipid solubility = high potency of drug
How does vascularisation determine levels of Anaesthesia
If somewhere in highly vascularised like the brain = higher levels
Does ventilation rate affect induction and removal of inhalation anaesthetics?
Yes
How are inhaled anaesthetics removed
Via veins back to the alveoli and exhaled
Where does some anaesthetics (inhaled) get metabolised into toxic waste
Kidney
What is the effect of inhaled anaesthetics of respiration
Depression of respiratory rate
What is the CVS effect of inhaled anaesthetics
Decreased BP (hypotension)
Via decreased cardiac output
Are IV general anaesthetics fast induction?
Yes
What are the names of the IV anaesthetics which are GABA agonists (hyperpolarisation)
Thiopental and etomidate and propofol
Why is etomidate a good GABA agonist / IV anaesthetic
It has a large TI
Why is propofol GABA modulator bad
Has rapid metabolism and therefore fast elimination
Also has a low TI
What are propofol, thiopentol and etomidate
Allosteric modulators of GABA
What is the only IV anaesthetic which is an NMDA antagonist
Ketamine
Why is ketamine rarely used as IV anaesthetic
Causes hallucinations and psychosis
Do IV anaesthetics like thiopentol and etomidate cause hypotension
Yes — they also lower BP like inhalation ones do
Which channel is targeted by local anaesthetics to stop AP
Voltage gated na channels
Which subunit do local anaesthetics bind to at voltage na channels
A subunit
What do B1 and B2 subunits on the na channels do
Hold the a subunit in the membrane 4 pass
What happens when voltage changes to the a subunit
Changes position causing opening and influx of na
Which state must local anaesthetics be in to bind to a subunit
Ionised
Which state must local anaesthetics be in first to pass myelin sheath
Unionised state
What are the 3 components of local anaesthetics
Aromatic ring
Amide or ester bond
Side chain (alkaline)
What determines duration of action of local anaesthetics
Hydrolysis of ester or amide bond
Where are amide bonds metabolised and do they have a longer half life than esters?
In the liver Via CYP
They do have a longer half life
Why are anaesthetics unionised when they enter via injection
They are weak bases which cause increased PH so causes unionisation
The base is then released
Where is the free base from anaesthetics ionised due to lower ph
At the axon
Which part can then when ionised at the acidic axon cause blocking of a subunit
The alkaline side chain
How can the body restrict site of action of anaesthetics
Via vasoconstriction at A1
How does the alkaline side chain cause faster induction
Faster absorption into the tissue being unionised
Which fibres are the most sensitive to local anaesthetics
Small diameter and myelinated
Why does increased AP firing cause better blockage via local anaesthetics
Channels are more in their open or inactive state rather than testing
The anaesthetic has higher affinity for these stages
What are the negatives of local anaesthetics if they get into the circulation
In the brain they’d cause confusion
In the heart they lower BP (hypotension)
How do inhalation anaesthetics cause increased BV
Stop glomerular filtration and less urine released
