PHARMACOLOGY - Anaesthetics Flashcards
Give three examples of injectable anaesthetic agents
Propofol
Alfaxalone
Ketamine
What is the mechanism of action for propofol?
Propofol potentiates the activity of inhibitory GABAa receptors
Which species’ is propofol liscenced in?
Dogs
Cats
How should propofol be administered?
Intravenous (I.V.)
Why is it recommended not to infuse propofol for more than 30 minutes?
Propofol is formulated with benzyl alcohol and infusion of propofol for more than 30 minutes increases the risk of benzyl alcohol toxicity
What else can be done to reduce the risk of benzyl alcohol toxicity?
To reduce the risk of benzyl alcohol toxicity, don’t administer more than 24mg/kg of propofol per anaesthetic
Why does propofol have such a rapid onset and a quick duration of action?
Propofol has a high lipid solubility and thus travels rapidly to the brain to carry out the desired effects. However, propofol is also rapidly redistributed to other blood rich organs and lipid stores where the drug will accumulate. Propofol is also rapidly metabolised
Which organs metabolise propofol?
Liver
Unknown site
What are the effects of propofol on the central nervous system (CNS)?
Rapid loss of consiousness
Anti-epileptic
What is the effect of propofol on the cardiovascular system?
Transient hypotension
What is the effect of propofol on the respiratory system?
Post-induction apneoa
What are some of the other effects of propofol on the body?
Occasional muscle twitching
Heinz body anaemia in cats
What are the two main indicators for the use of propofol?
Intravenous induction of anaesthesia
Management of refractory seizures
Why should you be cautious when using propofol in hypovolaemic patients?
Propofol is highly plasma protein bound and since hypovolaemic patients have fewer plasma proteins, there will be more free drug within the circulation and thus there will be a more profound pharmacological effect. Furthermore, propofol can cause vasodilation and hypotension, which will have a more profound effect in hypovolaemic patients
Why should you be cautious when using propofol in cats with hepatic dysfunction?
Cats metabolise propofol slower than dogs which can result in the increased accumulation of propofol in the body, especially in cats with hepatic dysfunction who cannot metabolise the drug as effectively as a healthy animal
Why should you be cautious when using propofol in cats that require repeat anaesthetics?
There is an increased risk of heinz body anaemia in cats with repeated or continuous infusions of propofol
What is the mechanism of action for alfaxalone?
Alfaxalone potentiates the activity of inhibitory GABAa receptors
Which species’ is alfaxalone liscenced in?
Dogs
Cats
Rabbits
How can alfaxalone be administered?
Intravenous (I.V.) preferably
Intramuscular (I.M.)
Subcutaneous (S.C.)
Why does alfaxalone have such a rapid onset and a quick duration of action?
Alfaxalone has a high lipid solubility and thus travels rapidly to the brain to carry out the desired effects. However, alfaxalone is also rapidly redistributed to other blood rich organs and lipid stores where the drug will accumulate. Alfaxalone is also rapidly metabolised
Which organ metabolises alfaxalone?
Liver
Why is alfaxalone tolerated better in cats compared to propofol?
While alfaxalone is metabolised slower in cats compared to dogs, it is not as significant as with propofol and thus there is less accumulation of alfaxalone in the body and thus it is more well tolerated in cats compared to propofol
(T/F) Alfaxalone has higher plasma protein binding than propofol
FALSE. Alfaxalone has a lower plasma protein binding than propofol
Could be a better choice for induction of hypovolaemic patients
What is the effect of alfaxalone on the central nervous system (CNS)?
Rapid loss of consiousness
What is the effect of alfaxalone on the cardiovascular system?
Mild hypotension
What is the effect of alfaxalone on the respiratory system?
Post-induction apneoa