Anaesthetics (year 2) Flashcards
what is the triad aims of anaesthesia?
muscle relaxation
unconsciousness
analgesia
what are the three main injectable agents used in anaesthesia?
propofol, alfaxalone, ketamine
what injectable agents can be used in anaesthesia?
propofol, alfaxalone, ketamine, thiopental, etomidate
what are the two main anaesthetic agents used as inhalation agents?
isoflurane and sevoflurane
what are the positives of injectable agents compared to inhalation agents?
injectable requires simple equipment and once administered it has to be metabolised and excreted to get rid of it
what are the positives of inhalation agents compared to injectables?
inhalation the depth can easily be adjusted and it is delivered with oxygen
what is the mode of action of propofol?
GABA agonist - reduces excitation in the brain
describe the appearance of propofol
not water soluble so is an emulsion
how is propofol administered?
IV
propofol is lipid soluble what does this mean it can easily cross in the CNS?
blood-brain barrier
where is propofol metabolised?
mainly the liver but also extrahepatic sites such as GIT
what are the effects of propofol?
anaesthesia, sedation, muscle relaxation, anti-seizure
what are the side effects of propofol?
vasodilation and blocks baroreceptor reflex so don’t get reflex tachycardia
respiratory depression due to altered carbon dioxide response
can cause oxidative damage to RBCs in cats
what is the mechanism of action of alfaxalone?
GABA agonist
what group of drugs is alfaxalone apart of?
neurosteroids
is alfaxalone water soluble?
no but is made water soluble by addition of cyclodextrin
why is alfaxalone made water soluble?
so it can be administered IV, IM or SC
where is alfaxalone metabolised?
liver - no extrahepatic metabolism
what are the effects of alfaxalone?
anaesthesia, sedation, muscle relaxation
what are the side effects of alfaxalone?
vasodilation - baroreceptor reflex is maintained so get reflex tachycardia
respiratory depression
excitability on recovered with animals often being noise sensitive
describe the mode of action of ketamine
NMDA antagonist
what type of anaesthesia do you get with ketamine?
dissociative - disconnection of higher brain function from the body
is ketamine water soluble?
yes
how is ketamine administered?
IV, IM, SC, orally
where is ketamine metabolised?
liver - except in cats it is excreted unchanged
what are the effects of ketamine?
anaesthesia and analgesia
what are the side effects of ketamine?
myocardial depression, increased HR, vasoconstriction, respiratory depression, muscle hypertonicity, cranial nerve reflexes maintained
what does it mean if the cranial nerve reflexes are maintained when using ketamine?
animal will continue to swallow and blink
what is the mechanism of action of thiopental?
GABA agonist
how is thiopental administered?
IV - it is an irritant if administered extravascularly
where is thiopental metabolised?
slowly in the liver
what are the effects of thiopental?
anaesthesia, muscle relaxation, anti-seizure
what are the side effects of thiopental?
myocardial depression, arrhythmogenic, respiratory depression
what is MAC when relating to inhalation anaesthesia?
minimum alveolar concentration of an agent at which 50% of patients won’t respond to noxious stimuli
what is MAC measured as?
% of atmospheric pressure
what time MAC is usually needed for surgery?
1.2-1.5 x MAC
what effects MAC?
age, species, agents acting on CNS, pregnancy, low BP, body temperature
what are the side effects of isoflurane and sevoflurane?
respiratory depression and potent vasodilation
isoflurane is more pungent than sevoflurane what does this mean for the animals breathing?
tend to not breath as well on isoflurane
is isoflurane or sevoflurane cheaper?
isoflurane
