Local Anaesthetics Flashcards
How do LAs work?
Reversibly bind to sodium channels in peripheral nerves
Inactivate sodium channels
No depolarisation = no impulse propogation = no sensation
Cocaine and amethocaine are what type of LA?
Esters
Lignocaine, bupivavaine and prilocaine are what type of LA?
Amides
Which are more likely to cause an allergic reaction?
Esters
Which are more toxic?
Amides
Which amide is most cardiotoxic? Why?
Bupivavaine
Binds better to sodium channels on the heart
Max doses of lignogaine (mg/kg)
without and with ADR
3
7
Max doses of bupivicaine/ levobupivicaine (mg/kg)
without and with ADR
2
2
Max doses of lignogaine (mg/kg)
Without and with ADR
6
9
Why use ADR?
LAs are vasodilators. ADR is a vasoconstrictor, so slows absorption of LA into the bloodstream, meaning it has a longer duration
Why is bicarb sometimes used with LA?
Acidic LA injection burns, bicarb reduces this
How may LA toxicity present?
pins and needles in lips, mouth and feet
Arrhythmias
CNS e.g. seizures
How do you manage LA toxicity?
INTRALIPID: creates area of low conc so LA moves into plasma
ADRENALINE: to protect the heart
SEIZURE CONTROL: e.g. propofol/ diazepam
How may ADR toxicity present?
tachycardia
anxiety
flushing
Why would you avoid adding ADR when operating on a finger/ toe/ nail etc
May lead to digital ischaemia
