L09: Local Anaesthetics Flashcards
What is the definition of local anaesthetics
Local anaesthesia reversible block nerve conduction when applied to an area for a procedure to be carried out without the loss of consciousness
Which sensory receptor detects pain
Nociceptors
What is the role of local anaesthetics to reduce pain
Interfere with voltage-gated sodium channels to stop action potential from occurring and pain
What is the end name for local anaesthetics
-Caine
What is the common chemical structure of all local anaesthetics
Aromatic ring
Amide group
Linkage group
What bond does the linkage group involve
Amide or ester bonds
Does an amide or ester bond get metabolised quick
Ester
Name 4 local anaesthetics
Procaine
Lidocaine
Prilocaine
Bupivacaine
What is the linkage group of procaine
Ester
What is the linkage group of lidocaine
Amide
What is the linkage group of prilocaine
Amide
What is the linkage group of bupivacaine
Amide
Which named local anaesthetics has the shortest duration
Procaine
Which named local anaesthetics has a medium duration
Lidocaine
Prilocaine
Which local anaesthetics has the longest duration
Bupivacaine
What is the property of the aromatic ring
Lipid soluble
What does a lipid soluble aromatic ring mean
The drug can pass through the membrane
What is an amine group
NH2
What can happen to the amine group which makes the drug non-lipid soluble
Add H+
What determines the status of the amine group
Acidity
What happens during pain at nociceptors in normal circumstances without general anaesthetics
At a pain stimulus Sodium voltage gated ion channels open
Sodium influx occurs
Depolarisation occurs
What happens during pain with local anaesthetics
1) The unionised form of local anaesthetics diffuses through the lipid membrane
2) the pH inside the cell sets up an equilbrium to get an ionised form of local anaesthetics
3) charged local anaesthetics blocks the sodium voltage gated channels so depolarisation cannot occur
What is the block of sodium voltage gated ion channel by local anaesthetics called
Use-dependent block
Which factors affect the action of local anaesthetics
Infection/ acidic conditions
How does increasing acidity affect local anaesthetics
Increase in local anaesthetic causes an ionised form of local anaesthetic so it cannot get into the cell
This gives poor anaesthesia
What is the best way of getting a greater area anaesthetised
Closer to the spinal cord
What are the 5 ways of administrating local anaesthetics
Topical anaesthesia Infiltration anaesthesia Nerve block anaesthesia Epidural anaesthesia Spinal anaesthesia
What is topical anaesthesia
You rub the drug on a thin membrane
What is infiltration anaesthesia
Injection onto wound
What is nerve block anaesthesia
The anaesthesia covers a lot of axons
What is epidural anaesthesia
Anaesthesia into the epidural space
What is spinal anaesthesia
Anaesthesia at the spinal cord
What are the common side effects of local anaesthetics
Allergic reaction due to preservatives within the drug
Respiratory failure if injected into the wrong place such as vessels
Which drugs are administered with local anaesthetics
Vasoconstrictors
Name a vasoconstrictor
Adrenaline
What is the purpose of giving adrenaline with local anaesthetics
Stops vasodilation and keeps the drug where we have put it and makes it last longer
What are the 4 properties of a good anaesthetics
Reversible
Block nerve conduction in nociceptive neurones
Long lasting
Low toxicity
Which sensory neurones have the highest sensitivity to local anaesthetics
Alpha delta
C
Which neurones have low sensitivity to local anaesthetic
Somatic motor neurones
Is alpha delta neurone myelinated or unmyelinated
Myelinated
