Local anesthesia Flashcards
1
Q
short acting local anaesthesia
A
procaine (ester type)
2
Q
medium acting local anaesthesia
A
lidocaine (amide type)
3
Q
long acting local anaesthesia
A
bupivacaine (amide type)
4
Q
How are local anesthesias cleared?
A
ester type -> butyrylcholinesterases in circulating blood plasma
amide type -> cyp450 in liver
5
Q
Mechanism of action of local anaesthesia
A
- passes lipid membrane and enters neurons to bind to receptors near intracellular end of sodium channels
- effect more marked in rapidly firing fibres (pain fibres fire more rapidly, hence more affected)
- reduction of polarisation, prolongation of repolarisation
- neurons kept more inactive
- other effects include anti-inflammatory effects
6
Q
How to increase onset timing of local anesthesia?
A
- Add sodium bicarbonate
- local anesthetics are weak bases hence increasing pH = more UNionised = pass through lipid membrane easier - choose anaesthetics with rapid penetration through skin
7
Q
How to prolong local anaesthetic effect
A
- higher dose
- add vasoconstrictors -> reduce adsorption and distribution into systemic circulation
- eg add epinephrine !
8
Q
sensory / pain fibres have xxxx firing rates than motor fibres
A
faster !
9
Q
motor fibres have xxxx firing rates than sensory / pain fibres
A
slower !
10
Q
how are local metabolites excreted?
A
via kidney
11
Q
Local anaesthetic chemical properties :
A
- most local anesthetics consist of lipophillic group connected via ester/amide to an ionisable group
- ester links more prone to hydrolysis → shorter duration of action
- weak bases
12
Q
what is local anaesthetic for?
A
- loss of noiciception
- induce local insensitivity / loss / absence of sensation to specific body part
- blocks afferent activity in peripheral and CNS
- analgesia , pain relief , surgical , dental procedures
