Anaesthesia Flashcards
The 2 types of neuromuscular drugs
Depolarising
Non-depolarising
Key chemical property of all anaesthetic agents
highly lipid soluble as they need to cross the BBB
General side effects of anaesthetics
- Decreased cardiac contractility
- Respiratory depression
- Sympathetic inhibition
Give 3 examples of anaesthetics administered intravenously
Thiopental
Propofol
Ketamine
Site of metabolism of IV anaesthetics
Liver
Site of metabolism of volatile anaesthetics
volatile agents are NOT metabolised
3 examples of volatile anaesthetics
Nitrous oxide
Isoflurane
Sevoflurane
Why are local anaesthetics less effective in acidic tissues?
Because they’re weak bases
MoA of local anaesthetic drugs
Block voltage sensitive Na+ channels
The effect of local anaesthetic agents depends on:
- diffusion gradient
- fibre size
- myelination
Why can local anaesthetics potentially be toxic?
they may block Na+ channels in all excitable tissues incl:
- heart - cardiac arrest
- brain - seizures, resp. arrest + loss of consciousness
When and why are NMJ blocking drugs given in anaesthesia?
to paralyse patients once sedated
Depolarising neuromuscular blocking drug
Suxamethonium
MoA of Suxamethonium
binds nicotinic ACh receptor –> depolarisation –> slower ACh hydrolysis –> prolonged depolarisation til no further transmission –> profound relaxation
MoA of non-depolarising muscle relaxants
bind cholinergic Rs but do not stimulate them
cause conformational change in R shape tht prevents ACh binding
fewer side effects than depolarising NMJ blocking drugs
Side effects of depolarising NMJ blocking drugs
- K+ efflux
- muscle fasciculations
- bradycardia
Give examples of non-depolarising neuromuscular blocking drugs
- Turbocurarine
- Rocuronium
- Atracurium
- Vercuronium
Why must patients fast before going under general anaesthetic?
to prevent aspiration of gastric contents
Why is caution advised when putting smokers or patients w Asthma under general anaesthetic
it may be difficult to intubate + thus ventilate these patients once sedated
Reliable clinical signs of anaesthesia
CNS signs:
- movement
- muscle tone
- light reflex
- eyelid reflex
- lacrimation
- eye position
Period immediately after adminsitering of induction agent
Induction
Features of Excitement stage of anaesthesia
- RR + HR become irregular
- uncontrolled movements
- vomiting
- breath holding
4 stages of anaesthesia
Stage 1 - induction
Stage 2 - Excitement
Stage 3 - Surgical/operative
Stage 4 - overdose/danger
MoA of Fentanyl
- binds kappa + delta-type opioid receptors
- opens calcium-dependent inwardly rectifying potassium channels
- causes hyperpolarisation + prevents further neuronal excitability
