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BDS2 OSCE > LA > Flashcards

LA Flashcards

1
Q

How do LAs work?

A

They stop never conduction by blocking the voltage-gated Na+ channels

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2
Q

In what order are nerve axons blocked?

A

A-Delta
C
A-Beta
A-Alpha

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3
Q

What senses are blocked first?

A

A-delta : sensory (mechano-, thermo-, noci- & chemoreceptors)

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4
Q

What is the mechanism of action for LA?

A

LA binds to site in NA+ channel
LA blocks channel & prevents Na+ influx
This block action potention generation & propagation
Block persists as long as sufficent # Na+ channels are blocked

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5
Q

What can LA cause?

A

Bradycardia and hypotension

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6
Q

Wjhat are the 3 components of LA molecules?

A

Aromatic region
Ester or amide bond
Basic amine side chain

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7
Q

Which part of LA molecules is hydrophilic and which part is hydrophobic?

A 
Aromatic region (Hydrophobic)
Basic amine side chain (Hydrophilic)
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8
Q

How is LA presented, and what does this do?

A

Presented as hydrochloride (B.HCl)

renders the amine base more water soluble

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9
Q

Does LA cross membrane in ionised or un-ionised form?

A

Only in un-ionised form

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10
Q

What % solutions are used in dental injections?

A

2-4%

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11
Q

What is the reducing agent used in LA preparations?

A

sodium metabisulphide

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12
Q

What else, other than reducing agents, are in LA preparations?

A

Preservatives and fungicide, ± vasoconstrictor

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13
Q

What can cause an allergic reaction between different LA brands?

A

Different preservatives/fungicides

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14
Q

What are esters used for?

A

Topical

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15
Q

What are Amides used for?

A

Injections

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16
Q

Examples of esters

A

Benzocaine

Cocaine/Procaine but these aren’t used any more

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17
Q

Examples of amides

A

Lignocaine
Prilocaine
Articaine
Mepivicaine (not used in UK)

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18
Q

What is the first choice amide?

A

Lignocaine

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19
Q

Are most LAs vasodilators or vasoconstrictors?

A

Vasodilators

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20
Q

When in LA preparations, what do vasoconstrictors do?

A

increase duration of action of LA

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21
Q

What are common LA preparation vasoconstrictors?

A

Adrenaline

Felypressin (synthetic vasopressin)

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22
Q

When can LAs containing felypressin not be used, and why?

A

Cannot be used on pregnant woment as can induce labour

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23
Q

What effect does adrenaline have on Alpha adrenoreceptors?

A

Vasoconstriction

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24
Q

What effect does adrenaline have on Beta-2 adrenoreceptors?

A

Vasodilation

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25
Q

What effect does adrenaline have on Beta-1 adrenoreceptors?

A

Cardiac muscle:
+ve chronotropic effect = >rate
+ve inotropic effect = >force

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26
Q

What receptors does vasopressin affect?

A

ADH receptors

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27
Q

What receptors do vasoconstrictors act on?

A

Vascular smooth muscle

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28
Q

Is adrenaline more effective on alpha or beta receptors?

A

Equally effective on both

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29
Q

What effect does adrenaline have when given locally?

A

vasoconstrictor effect - action on Alpha-receptors

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30
Q

What systemic effect does adrenaline have?

A

it lowers TPR (total peripheral resistance)

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31
Q

What effect does adrenaline have on mean arterial BP?

A

little to no effect

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32
Q

Which receptor is nodrenaline more effective on?

A

Alpha-receptors

33
Q

Systemically, noradrenaline has what effect on TPR?

A

Icreases TPR (alpha>Beta)

34
Q

What effects does noradrenaline have on mean arterial BP?

35
Q

Does adrenaline or noradrenaline sometimes cause a fall in BP

A

noradrenaline

36
Q

What are ester types of LA broken down by?

A

tissue esterases - action of esters is quite brief

37
Q

What are amide types of LA broken down by?

A

Liver amidases - action of amides has a longer duration

38
Q

What modes of administration are used in dentistry?

A

Surface application - topical
Local infiltration
Regional nerve block

39
Q

What LA preparations are used in dentistry?

A

Lignocaine:
2% lignocaine HCl,
2% lignocaine HCl + 1:80,000 adrenaline

Prilocaine:
4% prilocaine HCl,
3% prilocaine HCl + felypressin (0.03 U/ml)

40
Q

What is the formula for % solutions?

A

X% solution = X mass / volume

eg.
3% prilocaine HCl solution
3% = 3g/100ml
=30mg/1ml

so 2ml cart. of 3% prilocaine HCl will contain 2 x 30 = 60mg prilocaine HCl

41
Q

What is the maximum dose of lignocaine allowed?

A

approx 4mg per kg bodyweight

42
Q

What preservatives are used in LA preparations?

A

Bisulphite and Propylparaben

43
Q

Which preservative can cause an issue in patients that have asthma?

A

Bisulphite

44
Q

What is the process of preparing to giving LA? (8)

A 
Collect syringe handle & needle
Collect LA cartridge(s)
Unpack everything
Record decontamination details
Make up syringe handle 
Attach rubber bung
Cartridge into barrel & connect handle until clicks
Pull safety sheath back to 1click
45
Q

How should the patient be prepared for LA?

A

Position in chair (usually dependant on technique)
Dry mucosa with cotton wool roll or gauze
Apply pea sized amount of topical for 1-2 mins

46
Q

What is the technique for giving an injection?

A 
Stretch mucosa
Puncture mucosa quickly (use distraction - eg breathing)
Position needle tip @ target area
Bevel of needle towards bone
ASPIRATE
Inject slowly - no less than 30s
47
Q

Injection site for buccal infiltration?

A

Below apex of tooth

48
Q

What are the limitation of infiltrations?

A

Infection may limit effect

Dense bone may limit effect

49
Q

What are positives of buccal infiltrations?

A

High success rate
Technically easy
Atraumatic

50
Q

Buccal infiltration technique?

A 
Stretch cheek
Puncture mucosa, bevel open towards bone
Advance to needle to over apex of tooth
Withdraw slightly if bone contact
Aspirate
51
Q

What is the technique for a palatial injection? (6)

A

Are of needle penetration is 5-10mm palatial to centre of crown
Apply pressure behind injection site with cotton swab/mirror
Insert needle at 45* angle to the injection site with bevel angled towards soft tissue
Advance needle until contact with bone
Depth of penetration usually no more than few mm
No more than 0.2-0.4mL of cart req

52
Q

What os the Posterior Superior Alveolar branch effecting in achieving anaesthesia for?

A

Pulpal anaesthesia for First, second and third maxillary molars

53
Q

Where is the needle inserted for PSA injection?

A

MB fold over 2nd maxillary molar

54
Q

What percentage of population has Middle Superior alveolar nerve?

55
Q

What is the target injection area for Anterior superior alveolar anaesthesia?

A

MB fold over 1st premolar - target is infraorbital foramen

56
Q

What buccal approach blocks are there for maxilla?

A

PSA - posterior superior alveolar
MSA - middle superior alveolar
ASA - anterior alveolar nerve

57
Q

What is anaesthetised through greater palatine injection?

A

Posterior part of hard palate and overlying soft tissues as far as first premolar & medically to midline

58
Q

What is anaesthetised through nasopalatine injection?

A

Anterior portion of hard palate (soft & hard tissue) bilaterally from mesial of right first premolar to the mesial of left first premolar

59
Q

What LA injections are performed as buccal infiltrations in the mandible?

A

Mental nerve block

Buccal injection

60
Q

What is the target area for mental nerve block?

A

Between apices of lower premolars

61
Q

What is the target area for buccal injection in the mandible?

A

Lower buccal gingivae, slightly distal to the tooth to be treated

62
Q

What are the important landmarks for Inferior alveolar nerve block?

A

Coronoid notch of mandibular ramus
Posterior border of mandible
Pterygomandibular raphe
Lower premolar teeth of opposite side

63
Q

IANB - what is the site of anaesthetic deposition?

A

Region of the mandibular foramen

64
Q

What are the limitations of Inferior Alveolar nerve block?

A

Increased onset time
Increased lingual nerve injury
No change in intramuscular injection

65
Q

What is the technique for IANB?

A

Place thumb at anterior notch
Needle entry at junction of buccal fat pad/pterygomandibular raphe
Syringe lies over contra lateral 5-6
Advance to bony contact (1cm of needle visible)
ASPIRATE
Inject slowly

66
Q

IANB - What should be done if bone contact too soon or not at all?

A

Too soon - reposition syringe barrel mesial lay

Not at all - reposition syringe barrel distally

67
Q

How could a patient describe feeling anaesthetised?

A

Rubbery
Numb
Tingly
Swollen

68
Q

Via infiltration, how long does pulpal anaesthesia last? (List w/times)

A

Articaine 4% - up to 120 mins
Lignocaine HCl 2% - 60 mins
Prilocaine HCl 3% - 30-45 mins
Mepivicaine 3% - 20mins

69
Q

Via block, what is the duration of pulpal anaesthesia? (List w/times)

A

Lignocaine HCl 2% - 90 mins
Articaine HCl 4% - 75mins
Prilocaine HCl 3% - 60 mins
Mepivicaine 3% - 40 mins

70
Q

What is the duration of soft tissue anaesthesia with different anaesthetics?

A

Prilocaine HCl 3% - 3-6 hours
Articaine HCl 4% - 3-5hours
Lignocaine HCl 2% - 3-5 hours
Mepivicaine 3% - 2 hours

71
Q

Mepivicaine - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.

A 
Pulpal anaesthesia 
	Infiltration  - 20mins
	Block - 40 mins
Soft tissue 
	2 hours
72
Q

Lignocaine HCl 2% - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.

A 
Pulpal anaesthesia
	Infiltration - 60mins
	Block - 90mins
Soft tissue anaesthesia 
	3-5hours
73
Q

Articaine HCl 4% - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.

A 
Pulpal anaesthesia 
	infiltration - up to 120 mins
	Block - 75mins
Soft tissue anaesthesia 
	3-5 hours
74
Q

Prilocaine HCl 3% - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.

A 
Pulpal anaesthesia 
	Infiltration - 30-45mins
	Block - 60 mins
Soft tissue anaesthesia
	3-6 hours
75
Q

Mepivicaine - vasoconstrictor?

76
Q

Lignocaine HCl 2% - vasoconstrictor?

A

1:80,000 Adrenaline

77
Q

Articaine HCl 4% - vasoconstrictor?

A

1:100,000
1:200,000
1:400,000
all adrenaline

78
Q

Prilocaine HCl 3% - vasoconstrictor?

A

Felypressin (octapressin)

BDS2 OSCE (21 decks)

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