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Clinical skills - IPE & local anesthesia > 1. local anaesthesia in dentistry > Flashcards

1. local anaesthesia in dentistry Flashcards

1
Q

What is local anaesthesia?

A

“a loss of sensation in a circumscribed area of the body by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves”

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2
Q

DEFINITION OF LOCAL ANALGESIA

A

Localised loss of Pain sensation

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3
Q

DEFINITION OF LOCAL ANAESTHETIC

A

A drug which reversibly prevents transmission of nerve impulses in the region applied without affecting consciousness

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4
Q

Why Use LA?

A

✓ Controlling operative pain
✓ The control of postoperative/post-surgical pain
✓ Control of operative haemorrhage
✓ As a diagnostic tool
✓ Symptomatic relief of orofacial pain

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5
Q

Why Master LA?

A

✓ The most common procedure/ drug you will use
✓ One of the most feared / anxiety inducing procedures
✓ Fundemental to the practice of dentistry.
✓ Anaesthetists as well as dentists
✓ Duty of care to ensure optimal pain control for patients.
✓ Early control of acute pain can shape its subsequent progression

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6
Q

types of LA consent

A
  • Implied
  • Verbal
  • Written
  • Explain LA procedure, benefits & risks
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7
Q

physiology

A
  • Voltage-gated sodium channels are required for action potential generation
  • Action potentials are required to signal information in all (most) nerves
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8
Q

how does LA prevent information being signalled to nerves

A
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9
Q

what is differential block? (what does it affect and depend on?)

A

*Affects small diameter axons preferentially
*Affects un-myelinated axons preferentially
*Affects those axons on the outside more
*Depends on the type of sodium channel

*Therefore C>Aδ>Aβ>Aα

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10
Q

PHARMACOLOGY OF SPECIFIC BINDING THEORY

A

MECHANISM OF ACTION

  • Injected as acidic ionised water soluble hydrochloride salt
  • pH rises molecule dissociates to non-ionised free base
  • Lipid soluble free base diffuses through membrane
  • Once inside the nerve pH is lower#
  • Molecule re-ionises and blocks sodium channel
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11
Q

pH (make Q’s)

A

LAs cannot block sodium channels from outside the axon

  • Only uncharged LA can cross the axon membrane
  • Most LAs are weak bases pKa 8-9 (except benzocaine)
  • pKa = pH at which 50% LA charged & 50% not charged
  • LA + H+ LAH+
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12
Q

what is henderson hasselbalch equation?

A
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13
Q

chemistry / structure of LA

A
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14
Q

Types of LA used in Dentistry & Pharmacokinetics

  • what they consist of (structure)?
  • amides and esters metabolised by?
A
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15
Q

classifications of LA and examples

A

AMIDES:
- Lidocaine
- Prilocaine
- Bupivicaine
- Articaine

ESTERS:
- Cocaine
- Benzocaine

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16
Q

ACTION OF LA

1- Speed of action depends on?

A
  • Tissue pH and pKa of aneasthetic
  • Diffusion to site
  • Nerve morphology
  • Concentration
  • Lipid solubility
17
Q

ACTION OF LA

2 - Rate of diffusion away from the
nerve depends on

A
  • Protein binding
  • Concentration of anaesthetic
  • Lipid solubility
17
Q

ACTION OF LA

3 - Duration of action increased by
addition of

A
  • Vasoconstrictor e.g. adrenaline
18
Q

What’s in the LA Solution ?
- Function of each?

A
19
Q

Common Injectable Formulations in the UK
(2.2ml cartridges)

a) generic name
b) conc
c) vasoconstriction
d) brand name

A
20
Q

Common Topical ( surface ) Anaesthetics (with %)

A
  • Benzocaine 20%
  • Xylocaine 4%
  • Lignocaine ointment 5% or spray 10%
  • EMLA – lignocaine 2.5% & prilocaine2.5%
  • Oraqix TM mixture of 5% prilocaine & lidocaine. Periodontal probing & scaling
  • Ethyl Chloride Spray
21
Q

features of an Ideal Local Anaesthetic

A
  • 100% effective
  • Safe with no side effects
  • Painless and easy to administer
  • Quick effect
  • Last only for duration of procedure (?)
  • Well localised
  • Cheap
22
Q

features of 2% lidocaine with 1:80000 adrenaline ( EPINEPHERINE)

A
  • Most popular local anaesthetic agent
  • Safe and effective
  • Good vasoconstrictor properties
  • Cheap to use
  • Adrenaline should be used with care in pts who have had a recent MI, cardiac arrhymia,intravascular injection must be avoided
23
Q

features of 3% Prilocaine with felypressin or 4% Prilocaine (Plain)

A
  • Marketed as Citanest with Octapressin
  • Theoretical risk of inducing labour in late pregnancy/associated with methemoglobinemia as adverse reaction.
  • Use if do not wish to use adrenaline containing LA/allergy to lignocaine(rare)or if allergy to latex as non latex bung
  • Felypressin vasoconstrictor effect not as good as adrenaline, less effective at reducing operative bleeding and less depth and duration of anaesthesia.
24
Q

features of 4% Articaine with 1:100,000 adrenaline

A
  • Introduced UK 1999
  • Amide-type LA but metabolised by plasma esterases (decreases toxicity)
  • Half life about 20 mins (lignocaine 90 mins)
  • 4% solution (2.2ml cartridge has 88mg – max dose 500mg)
  • 1:100,000 adrenaline (epinephrine) as vasoconstrictor
25
Q

features of Bupivacaine 0.25% 0 or 1:200,000 adrenaline

A

*Longer acting
*Higher incidence of dysrythmias when compared to lidocaine
*Good for post operative pain control

26
Q

how do you know the max dose of a LA

A
  • The maximum dose varies depending on the product - Information given in SPC (Summary of Product Characteristics)
  • The maximum dose you can give without inducing a toxic reaction in a healthy male in his 20s
  • Therefore, the dose needs to be adjusted in:
  • Children /elderly
  • Patients with liver/ kidney disease
27
Q

MAXIMUM DOSE chart eg

A
28
Q

TOXIC DOSES for an Adult 70 Kg

*ASSUME 2.2ml CARTRIDGES

A
  • Lignocaine 2% and adrenaline 11 Cartridges
  • Prilocaine 3% and felypressin 8 Cartridges
  • Articaine 4% and adrenaline 5.5 Cartridges
  • Marcaine 0.5% with adrenaline 10 Cartridges

Clinical skills - IPE & local anesthesia (3 decks)

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