Local Anesthetics Flashcards
Function of LA
Prevent transmission of nerve impulse in region to which its applied without affecting consciousness
Which are the topical LAs
Lignocaine
Prilocaine
Tetracaine
Benzocaine
Oxybuprocaine
Which are the injectable LAs
Bupivacaine
Levobupivicaine
Lignocaine
Mepivacaine
Ropivacine
MOA of LAs
block voltage gated Na channels and reduce infux of Na ions
=prevention of depolarisation of membrane by blocking AP
Steps in LA MOA
Unionised LA diffuses across CM
LA becomes ionised due to lower intracellular pH
Ionised LA blocks NA channel=prevent propagation of APs
Effects of infected tissue on LA
Infected tissue have decr. pH
therefore, fraction of ionised LA is reduced
=reduced effect
Infected tissue have incr. blood supply
= more LA removed from local area before it can have an effect
How does diameter influence LA
Smaller diameter nerve fibre= more blocade as compared to Larger diameter fibres
How does myelination affect LA
Myelinated fibres are more susceptible to blockade compared to unmyelinated fibres of same size
Order in Fibers blockade
- Sympathetic and pain
- Temperature
- Light touch and Proprioception
- Motor
Order in fiber recovery
- Motor
- Light touch and Proprioception
- Temperature
- Sympathetic and pain
DOA of LA depends on
-uptake into general circulation
-addiction of vasoconstrictor (AE/E, Levonodefrine)
Effects of adding vasoconstrictor to LA
Localise LA at desired site
Prolonged DOA
Reduced local hemorrhage
Reduce amount of LA absorbed into SC
Decrease toxcity
DI of Vasoconstrictor
TCAs: potentiate HT effect
Non-selective B-Blockers: incr. BP, reflex decr. HR, monitor BP
Cocaine, Methamphetamine abusers:
incr. risk HT crisis, stroke, MI
Digoxin: narrow TI=cardiac arrythmias
CI of Vasoconstrictors
Severe Heart disease
Uncontrolled Hyperthyroidism
Sulphite allergies
Asthmatics (corticosterioid-dependent)
Pheochromocytoma
Topical anaesthesia provide
Short term relief
High LA conc. in an oily vehicle slowly penetrate skin or mucous membrane
Infiltration anaesthesia provide
numbness faster than topical anesthesia.
LA is injected transdermally/subcutaneously by the area to be anaesthetised
Peripheral nerve block anesthesia provide
provide fields of anaesthesia distal to site of injection
Injection of LA around a nerve trunk
Which are the nerve block LAs
Bupivacaine
Lignocaine
Ropivacine
Mepivacaine
Central nerve block anaesthesia provide
produce anaesthesia above and below site of injection
LA is injected near the spinal cord
E.g of Central nerve block anaesthesia
Epidural anesthesia
Which are the Central nerve block LA
Bupivacaine
Lignocaine
Ropivacaine
IV regional anaesthesia allow for
Manipulation of fractures and minor surgical procedures
LA is injected into a limb after application of tourniquet
Which are the IV regional LA
Lignocaine
Which LAs are esters
Benzocaine
Oxybuprocaine
Tetracain
