Anaesthesia Flashcards
Name 4 Drugs given IV for general anaesthesia
Propofol
Ketamine
Barbiturates
Etomidate
Name 5 inhaled anaesthetics used for general anaesthesia
Sevoflurane Desflurane Isoflurane Xenon Nitrous oxide
What is concious sedation?
Where a small amount of anaesthetic/benzodiazepines are used to create a sleepy state where the patient is concious but comfortable.
Name the two ways general anaesthetics work
By enhancing inhibitory signals (activating GABA)
By inhibiting excitatory signals (inhibiting glutamate/NMDA)
List 2 general anaesthetic that works by activating GABA
Propofol
Barbiturates
List 3 general anaesthetics that work by inhibiting glutamate/NMDA
Ketamine
Nitrous Oxide
Xenon
What are the 5 steps in anaesthesia, excluding end of procedure anaesthesia?
1) pre medication- (send you to sleep) usually benzo eg Lorazepam
2) induction (usually IV)
3) intra-operative analgesia (usually opioid)
4) muscle paralysis (allows to intubation)
5) maintenance (IV or inhalation)
What two steps of anaesthesia are at the end of a procedure?
1) reversal of muscle paralysis
2) provision for post op N+V and analgesia
What is MAC? (Minimum alveolar concentration)?
Alveolar concentration at which 50% of patients fail to move to stimuli (where [alveolar] = [spinal cord])
List 7 things that can affect MAC and their effect
Age (infants have higher MAC, elderly have lower)
Temperature (hyper increases, hypo decreases)
Alcohol (increases MAC)
Pregnancy (increases MAC)
Central Stimulants (increases MAC)
Other anaesthetics/sedatives (decrease MAC)
Opioids (increase MAC)
What can you use to decrease MAC? (Meaning you can use lower doses of anaesthetic)
Using N2O instead of O2 allows MAC to decrease
What brain circuits are being targeted by general anaesthesia?
Reticular formation
Brainstem (therefore decreases resp and cvs drive)
Analgesia depresses anterior horn and motor neuronal activity
What are the 4 levels of anaesthesia? (Guedes sign)
1) analgesia- normal muscle tone, analgesia but concious
2) excitement is a short phase, not always seen. Muscle tone is normal or increased, breathing can be erratic.
3) surgical anaesthesia (has 4 levels from slightly relaxed to markedly with weak breathing and no eye movements)
4) respiratory paralysis- flaccid and no breathing or eye movements
What level of anaesthesia is regularly not seen? Why? And what are the features?
Excitement phase (2nd)
Usually too quick to be seen
Erratic breathing, normal to increased muscle tone.
Name 5 local anaesthetics
Amide- lignocaine, bupivicaine, prilocaine, procaine
Ester- cocaine, amethocaine
Why are amide anaesthetics better than Ester?
They have a stronger bond and are heat stable and so more stable and so last longer.
Also Ester anaesthetics when metabolised result in PABA production, which can cause allergy.
In what state can local anaesthetics cross the cell membrane?
Unionised
In which state, acidosis or alkalosis, does the local anaesthetic last longer?
Alkalosis
If patient is more acidotic, LA becomes ionised very quickly and therefore ineffective
Why are local anaesthetics given with adrenaline?
Many LAs have vasodilator effects which therefore increases systemic absorption (rather than local).
Adrenaline is a vasoconstrictor.
Where shouldn’t you deliver local anaesthetics with adrenaline?
Small digits due to risk of ischaemic necrosis due to vasoconstrictor effects of adrenaline.
Need to aspirate first to check not in vein/artery.
How are local anaesthetic metabolised?
Esters: metabolised quickly by plasma esterases
Amides: metabolised in liver
Why does bupivicaine have a longer duration of action?
It is more proteinbound therefore has a longer duration of action as drug is made available for metabolism more slowly.
