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Intro to OS and Pain Management > Local Anesthesia > Flashcards

Local Anesthesia Flashcards

1
Q

what percentage of adults fear the dentist

A

21%

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2
Q

what percentage of the US population avoid dental care due to fear

A

10%

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3
Q

what are the top 10 fear evoking dental situations

A
  • dentist laying out instruments
  • sitting in the waiting room
  • dentist squirts air into a cavity
  • dentist laughs as he looks at your mouth
  • dentist places a probe in a cavity
  • dentist is giving you a shot
  • dentist hold needle in front of you
  • dentist tells you your teeth are bad
  • dentist is drilling your tooth
  • dentist is pulling your tooth
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4
Q

what are the desirable properties for local anesthesia

A
  • no irritation to tissue
  • no permanent alteration
  • low systemic toxicity
  • effective if injected into tissue or mucous membranes
  • short onset
  • long enough duration of action for procedure
  • potent yet not harmfully concentrated
  • not elicit allergic reaction
  • readily undergo biotransformation
  • sterile or capable of being sterilized by heat without deterioration
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5
Q

what are the ways to control pain and anxiety in dentistry

A
  • local anesthesia
  • oral sedation
  • I.M. sedation
  • NO sedation
  • I.V. sedation
  • general anesthesia
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6
Q

what does local anesthesia do

A

prevent generation and/or conduction of a nerve impulse
- decrease permeability of ion channels to Na
- nerve block by local anesthesia is a non depolarizing block

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7
Q

what is pain threshold

A

the least experience of pain which a subject can recognize

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8
Q

what is pain tolerance

A

the greatest level of pain which a subject is prepared to tolerate

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9
Q

what is a sensory neuron made of

A
  • CNS
  • trigeminal ganglion
  • foramen
  • nerve fiber
  • pain receptors
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10
Q

what is the charge of ECF

A

more positively charged

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11
Q

what is the charge of the axoplasm

A

more negatively charged

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12
Q

describe nerve impulse transmission

A
  • nerve axon membrane channel closed
  • fiber stimulated, channel opens sodium enters
  • cell depolarized and channel closes
  • potassium exits down concentration and electrical gradients
  • fiber repolarized, Na/K pump restores balance
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13
Q

where do local anesthetics work

A

nerve membrane

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14
Q

what is the specific receptor theory

A

local anesthesia bind to specific receptor on the Na channel

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15
Q

what are the different theories that try to explain how local anesthetics work

A

-acetylcholine theory
- calcium dependent
- surface charge
- membrane expansion but failed

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16
Q

what is the conduction rate of C fibers vs Alpha and delta fibers

A

C fiber is 1.2 m/sec
alpha and delta is 120 m/sec

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17
Q

what channel is in the node of ranvier

A

sodium channel

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17
Q

what is the basic structure of local anesthetics

A
  • lipophilic group and hydrophilic group attached by amide or ester link
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17
Q

which fiber type is myelinated

A

alpha and delta fibers

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17
Q

to ensure effective anesthesia:

A

-2-3 nodes need to be blocked
- 8-10 mm length needed

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17
Q

what does myelin sheath do

A

insulates axons electrically and pharmacologically

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17
Q

what are the majority of active forms of local anesthetics

A

tertiary amine except prilocaine and hexylcaine

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17
Q

all local anesthetics are ____ except ____

A

amphipathic; benzocaine

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18
Q

which anesthetics have weak local anesthetic properties

A

antihistamine and anticholinergic

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19
Q

what are the two types of local anesthetics and describe both

A

-amide: resist hydrolysis , excrete unchanged in urine
-ester: readily hydrolyzed in aqueous solution

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20
Q

what are the ester anesthetics

A

-procaine
- propoxycaine
- tetracaine
- cocaine
- benzocaine
- dyclonine

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21
Q

what are the amide anesthetics

A
  • lidocaine
  • etidocaine
  • mepivacaine
  • bupicacaine
  • prilocaine
  • articaine
22
Q

why is benzocaine a topical and not an injector

A

it doesnt have a hydrophilic group

23
Q

how does local anesthesia dissociate

A
  • they are weak basic compounds
  • combine with acids to from local anesthetic salt (HCl)
24
Q

what is the chemical formula for dissociation of local

A

RNH+ -> RN + H+
where RNH+ is cation and RN is uncharged molecule (free base)

25
Q

what does the relative proportion of ionic form depend on

A

pKa

26
Q

what is the henderson- hasselbalch equation

A

log base/acid = pH - pKa

27
Q

when pH of a solution = pKa you have:

A

50/50 RN/RNH+

28
Q

what are the two factors involved in the action of local anesthesia

A

-diffusion through nerve sheath
- binding at receptor site

29
Q

what is the normal tissue pH of etidocaine and how much acid and base is there

A

7.4
- 25% free base (RN), 75% cation (RNH+)

30
Q

if theres 1000 molecules available of etidocaine how many will diffuse through the membrane

A

250 lipophilic RN

31
Q

once at intracellular level etidocaine will re- equilibrate into

A

70 RN and 180 RNH+

32
Q

high pKa will translate to ____ because

A

slow onset because few base molecules available to diffuse

33
Q

why is inflamed or infected tissue much more difficult to get adequate anesthesia to

A

because of lower pH or high H+

34
Q

what does low pH equate to in local anesthesia

A

longer shelf life

35
Q

what is the optimum pH for most anesthesia

A

5.5 to 7

36
Q

what is sodium bisulfite added with

A

vasoconstrictor

37
Q

what difference does adding a vasoconstrictor make

A

slower onset

38
Q

most topical anesthesia is prepared in _______ compared to injectable local anesthesia

A

more concentraated

39
Q

why is topical anesthesia more concentrated compared to injectable

A

poor buffering capacity of mucous membrane

40
Q

what is the order of layers the anesthesia crosses in the nerve

A

endoneurium -> perineurium -> epineurium

41
Q

which layer of the nerve is the greatest barrier of diffusion for the anesthesia and why

A

perineurium because it is thickest

42
Q

where do mantle fibers innervate

A

proximal region of molars

43
Q

what does the core fiber innervate

A

distal points such as incisors

44
Q

what does complete conduction blockade require

A

volume and concentration

45
Q

what happens to injected local anesthesia

A
  • absorbed by nonneural tissue
  • diluted by interstitial fluid
  • removed by capillaries and lymphatic system
  • for ester type: immediate enzymatic hydrolysis
46
Q

how does lower pKa affect onset of action

A

faster

47
Q

how does lipid solubility relate to potency

A

greater potency if more lipids

48
Q

how does protein binding affect duration of anesthetic

A

increased protein binding increases duration

49
Q

nerve membrane is ____ lipid

A

90%

50
Q

nerve membrane is ____ protein

A

10%

51
Q

how does the tissue recover from nerve block

A
  • reverse of anesthetic induction pattern
  • intraneural concentration exceeds extraneural concentration
52
Q

what is meant by recurrence of immediate profound anesthesia

A
  • reduced concentration at mantle fibers
  • residual local + newly deposited supply = immediate profound anesthesia
53
Q

when is it difficult to reestablish profound anesthesia

A
  • surgical procedure outlasts effectiveness of med
  • tachyphylaxis
54
Q

what is tachyphylaxis

A

increased tolerance to frug after repeated administration

55
Q

what are the factors that affect tachyphylaxis

A
  • edema
  • localized hemorrhage
  • clot formation
  • transudation
  • hypernatremia
  • decreased pH of the tissue
56
Q

what are the 3 main physiochemical properties of local anesthetics

A
  • lipid solubility
  • pKa
  • protein binding
57
Q

when is pain tolerance the highest? lowest?

A
  • highest: 8 am
  • lowest: 4 pm
58
Q

what does lipid solubility influence

A

potency

59
Q

what does pKa influence

A

onset

60
Q

what does protein binding influence

A

duration

61
Q
A

Intro to OS and Pain Management (9 decks)

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