Local Anaesthetics Flashcards
What are the commonly used local anaesthetics?
Lidocaine
Bupivacaine
What is the mechanism of action for local anaesthetics?
Non-ionised form of local crosses phospholipid bilayer
Combines with hydrogen ion to become ionised
Ionised form blocks sodium channel in afferent nerves
How does pH effect local anaesthetics?
pH affects proportion ionised:non-ionised
At 7.4 lidocaine has more non-ionised - acts quicker
How does infection effect local anaesthetics?
Infection lowers the pH
More in ionised form
Takes longer to work
What effects the duration of action of local anaesthetics?
Lipid solubility
Protein binding
Bupivacaine - 95% protein bound - longer
Lidocaine - shorter
What is the effect of adrenaline on local anaesthetics?
Cause vasoconstriction
Decreases tissue distribution
Decreases bleeding
What are contra-indications of local anaesthetics?
Allergy
Infection
What are signs of local anaesthetic toxicity?
Neuronal
- tingling lips
- tinnitus
- agitation
Cardiovascular
- tachyarrythmias
- bradycardia
What does 1% mean?
1% = 10mg/ml
What is the dose of lidocaine?
3mg/kg
What is the dose of bupivicaine?
2mg/kg
