Anaesthetic Drugs Flashcards
What is the triad of anaesthesia?
Consciousness (amnesia)
Pain Relief (analgesia)
Muscle relaxation (akinesia)
Why do anaesthetic drugs need to be lipid soluble?
Lipid soluble - important to act in CNS as they can cross the BBB rapidly by diffusion, rather than requiring specific transport mechanisms.
The more lipid soluble the drug is - the more potent it is.
Apart from anaesthesia, what is propofol also used for?
Antiemetic
Anti-epileptic
How long does propofol last?
5-10 mins - so need to give IV infusion or add inhaled volatile agent
Why are fat levels of propofol poor compared to other areas, despite the drug being lipid soluble?
Fat has a poor blood supply - so its less perfused and less drug reaches here
What happens initially when putting Ps under with halogenated ethers?
They get excited & may struggle - can take a few minutes before they go under.
= Etherisation signs
What is the mode of action of Succinylcholine?
Depolarising neuromuscular blocking agent
Mimics the effects of ACH - binds strongly to the receptor causing depolarisation. ACh cannot bind, Sux remains bound to the receptors so no further depolarisations can take place - muscles relax.
What is the half life of succinylcholine?
2 minutes
Metabolised by plasma cholinesterase
What are the SEs of succinylcholine?
Causes fasciculation - thought to be cause of myalgia after surgery
Higher rate of anaphylaxis
Can inc serum K+
Is also a congenital abnormality meaning there is no cholinesterase - therefore the Sux doesn’t get metabolised - means P can be paralysed for hours (rare)
What is the MOA of Rocuronium?
Is a non-depolarising neuromuscular blocking agent. Competes with ACh and blocks Na+ channel. Rapid onset but 20-30mins to reverse.
Which agents can be used to reverse rocuronium?
Neostigmine
Sugammadex (v expensive - emergency use)
What is the MOA of neostigmine?
Binds to acetylcholinesterase and prevents breakdown of ACh in the synaptic cleft - means more ACh to bind to receptors.
What must you give with neostigmine?
Most give Atropine!
Otherwise can cause severe bradycardia - this is because heart muscarinic receptors (PSS) get activated
