Lecture 9 Flashcards
NO
Laughing gas used as a GA= NMDA inhibitor
ether
Gas (volatile) used as a GA- very flammable
Chloroform
Volatile drug administered to pregnant women during labour. Very flammable.
isoflurane
Halogenated hydrocarbon used as an intravenous anaesthetic
thiopental
barbiturate used as an intravenous anaesthetic
alphaxalone
steroid used as an intravenous anaesthetic
What are chemical and physical GA?
chemical= gas and intravenous physical= decrease in pressure and temperature
What determines how potent drugs are?
the oil: gas partition coefficient- the more lipid soluble the more potent it is which gives a rise in MAC
How do volatile GAs work?
Bind to alpha and beta subunits on GABAa Rs
They activate a 2 pore domain in K+ channels to hyperpolarise the neurons
How to intravenous GAs work?
Bind only to the beta subunit of the GABAa R
Why do GAs need to be lipid permeable?
They need to interact with aas on receptors/ channels
What effect does isoflurane have on neurotransmission?
It decreases the amount of fusion of NT vesicles making APs more spread out due to less excitation
Where is there a decrease in vesicle numbers when GAs are administered?
hippocampus= amnesia
spinal cord= inhibition of spinal reflexes
thalamus= analgesic
reticular formation= loss of consciousness
Why are high concs of GA bad?
They inhibit all brain regions= loss of autonomic control e.g. breathing which leads to death
What are the 4 stages of anaesthesia?
1) Analgesia
2) excitement
3) surgical anaesthesia
4) medullary paralysis- need lipophillics to reverse which is difficult in obese people
propofol
Intravenous general anaesthetic- rapidly metabolised and rapid recovery
What are the properties of intravenous GAs?
They are rapidly perfused, easily cross BBB
pain at site of administration, complex pharmacokinetics
thiopental
Complex pharmacokinetics- results in hangover due to being very lipid soluble
short duration of action
intravenous GA
Ketamine
is a dissociate anaesthetic= not complete loss of consciousness but powerful analgesic
similar to BZD which is used in vets
What do you do if state of ana is too deep when on inspiratory GA
Decrease the concentration and increase ventilation rate to remove the gas from the lungs
Why is there quick equilibrium between target and conc
because they are not very soluble in blood so they partition quickly into lipid- blood:gas
Dantrolene
Ryanodine antagonist
