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BDS2 BAMS Local Anesthetic > Local Anaesthetics > Flashcards

Flashcards in Local Anaesthetics Deck (63)
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1

How do LA work

They stop nerve conduction by blocking the voltage gated sodium channels

2

What does LA work on

The first order afferent receptors - not the CNS but the PNS

3

What do the connective tissue barriers in the peripheral nerves act as

A diffusion barrier

4

What does a greater number of membrane mean for the LA

Will take longer to anesthetize

5

What is the general rule for weaning out

Nerves that will be anesthesized first will wean out first

6

What is the effect of position of the nerve in the bundle to LA

The further it is from the LA the longer it will take to be anaesthetised

7

What is the order of block in different fibres

Adelta, C, Abeta, Aalpha

8

What group do A alpha sensorial nerves belong to

group I

9

What group do A beta nerves belong to

group II

10

What group do Adelta nerves belong to

group III

11

What group do sensorial C nerves belong to

group IV

12

What is the function of A Alpha nerves

sensory (proprioception)
motor (skeletal muscle)

13

What is the function of A Beta nerves

sensory (mechanoreception)

14

What is the function of A gamma

Motor (muscle spindles)

15

What is the function of A delta

Sensory (mechanic-, thermo-, noci and chemoreceptors)

16

What is the function of C fibres

Sensory (noci-termo and chemoreceptors)
autonomic (post ganglionic)

17

What fibres do we want to anesthetize

Delta
A beta
C

18

What fibres do we not want to anaesthetise

autonomic

19

What is the mechanism of action of LA

binds to a site in the sodium channel
LA blocks the channel and prevents sodium influx
This blocks the action potential generation and propagation
Block persists so long as a sufficient number of NA channels are blocked

20

What other Na channels does LA block

in other excitable tissues e.g heart muscle

21

What are possible side effects of LA

bradycardia
hypotension

22

Do we need all sodium channels blocked

We don’t need to have absolutely all sodium channels blocked but enough to avoid AP reaching the maximum level

23

What are the 3 components of the organic molecule in lLA

aromatic region (hydrophobic)
ester or amide bond
basic amine side chain (hydrophilic)

24

How is LA presented as

hydrochloride (B.HCl)

25

What does the B.HCl allow

renders the amine base more water soluble

26

Why are LA partly dissociated

As they are active in the ionized form
They can cross the membrane only in the unionized form

27

In what form is B.HCl pharmacologically active but non diffusible

B.H+

28

In what form is B.HCl diffusible but not active

B. + H+

29

What molecule binds the sodium channel

B.H+

30

Why are small diameter axons more susceptible to LA block

Same concentration of LA will act better on small diameter axons because there are less sodium channels to block