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Anaesthesia > Pharmacology To LA > Flashcards

Pharmacology To LA Flashcards

0
Q

What topical preparions For la are there?

A

Lidocaine

Benzocaine

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1
Q

What are the two types of LA techniques?

A

Topical: provides LA to soft tissues
Injectable: provides nerve block and infiltration

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2
Q

How can topical LA affect dose absorbed?

A

Lidocaine: well absorbed so must be included in max dose to pt
Benzocaine: poorly absorbed and works faster and have choice of flavours, less important in total dose

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3
Q

How far dose topical anaesthetise to?

A

2-3mm depth

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4
Q

What type of tissue does topical work on?

A

Non keratinised so little use on palate

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5
Q

Why is topical not effective on keratinised mucosa?

A

Tissues deeper tha 2-3 means thr pain is produced by rapid rate of injection

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6
Q

How long should you leave topical to work?

A

2 mins

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7
Q

What is the difference between anaesthesia and analgesia ?

A

Anaesthesia: absence of all sensation
Analgesia: abscence of pain sensation

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8
Q

Which LA do we mainly use as dentists in UK?

A

Lidocaine

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9
Q

Which anaesthetic agents do we use as dentists?

A
  • Lidocaine 2% with adrenaline 1:80,000
  • Prilocaine 3% with felypressin 0.031IU/ml
  • Articaine 4% adrenaline 1: 1/2/400,000
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10
Q

What is the max dose of lidocaine?

A

4.4mg/kg up to 300mg

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11
Q

When would u use Prilocaine?

A

When epinephrine contraindicated but not as effective as lidocaine

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12
Q

Hat is the max dose for Prilocaine?

A

8mg/kg

400mg

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13
Q

What is the issue with felypressin?.

A

Can cause coronary artery constrictionso limit dose in patients with IHD to 3 cartridges

Not to be used in preg

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14
Q

T/Farticaine has a short half life?

A

T

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15
Q

What is the max dose of Articaine?

A

7mg/kg

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16
Q

T/F Articaine can be used for ID block

A

T

However until further evidence should use other anaesthitics

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17
Q

T/F LA is inherently water soluble?

A

F

to make it water soluble it is combined with HCL

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18
Q

What is the purpose of adding adrenlaine?

A

vasconstricor

pronlongs duration

19
Q

What s the effect of adrenlaine?

A

this causes the pH of the anaestehtic to drop even more and become smore acidic which means aneasthetic stings upon entry and it has a slower onset

20
Q

What is pKa?

A

this is the dissociation constant

the pH at which 50% of the LA will be in the ioned form and 50% will be in the unionesed for,

21
Q

What form iones or unionised does LA need to be in to cross across the nerve membrame?

A

un ionised

22
Q

if the pKa of lidocaine is 7.9 what does this mean?

A

below 7.9 more than 50% will be ionised

above 7.9 less then 50% will be ionsed i.e more unionsed

23
Q

What is adde to the LA solution to help try an increase the number of unionsed particles?

A

Sodium bicarbonate

24
Q

What is an alternative to adrenalin?

A

Felypressin

Allergies
Cocaine users

25
Q

What is blocked by the LA?

A

LA blocks the sodium poassium voltage gated channels. it binds to the sodium portion and prevents sodium from rushing inside also by membrane expansion (10% of effect)

two therories: non specific and specific

non: membrane expansion, where the lipophilic aromatic ring is incoporated into the nerve cell membrane, this then causes the nerve cell memenrae to swell and makes the sodium channells smaller and thus harder for sidum to pass through
specific: charged hydrophilic portion binds to the some areas os the sodum channel to obstucy sodum ion passage

26
Q

What is the resting potentil of the nerve membrane?

A

-70mV

27
Q

What happens when an action potental is fired?

A

sodium rush in making the rsting potentil more postive to +40mV(depolarisation)
postassium rush out in the repolarisation making it more negative again (repolarisation)

28
Q

What is the threshold value for depolarisation?

A

-55mV

29
Q

What is the molecular structure of LA?

A

Aromatic ring

intermidiate linkage (amids or ester)

terminal amine

30
Q

Wwhich portion is lipophilic?

A

AROMATIC RING

31
Q

Which portion is hydrophilic?

A

terminal amine

32
Q

WHich LA are amides?

A

Lidocaine
prilocaine
mepivaein
bupivicaine

33
Q

Where are amides metabolised?

A

liver

34
Q

What LA are esters?

A

articane
procaine

Benxocaine (topical)

35
Q

Wheere are esters matbalised/

A

plasta cholinesterarses

36
Q

Whcih LA is both amide and ester?

A

articaone

37
Q

What is the half life, time of onset and duration of action for lidocaine?

A

Onset – 2-5 mins
Half life 90 mins
Duration pulpal – 45 - 60 mins
soft tissue - 2- 3 hrs

38
Q

What is the half life, time of onset and duration of action for articaine?

A

Onset 1-6 mins
Half life 20 mins*
Duration pulpal – 75 mins
soft tissue – 20 to 175 mins

39
Q

What is the half life, time of onset and duration of action for prolicaine

A

Half life 90 mins
Duration pulpal – 60-90 mins
soft tissue – 2-4 hrs

40
Q

What are the contents of LA?

A 
LA base
HCL salt
Vasocontrictor
buffering agents eg sodium bicarbonate
preservatives eg methyl paraben, soduim suplphite which stabilises adrenaline
41
Q

Name an example of a catecholamine vasocontrcirt?

A

aderenaline

42
Q

NAme an example of a non catecholamine vaso?

A

felyprssin

43
Q

Why is LA less effective in infeted tissues?

A

infmaked tissues: acidic therefore less LA is ionised form
increased vasculaiurty: which means more solution is removed away
prostaglandins lower the threshold for nerve firing and higher concentration of LA is needed

44
Q

Why do children with abscess on upper molars always present with faciall sweeling?

A

because they have a low attatchent of buccinator

Anaesthesia (11 decks)

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