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LA Flashcards

(78 cards)

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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
What effect does adrenaline have on Beta-1 adrenoreceptors?
Cardiac muscle: +ve chronotropic effect = >rate +ve inotropic effect = >force
26
What receptors does vasopressin affect?
ADH receptors
27
What receptors do vasoconstrictors act on?
Vascular smooth muscle
28
Is adrenaline more effective on alpha or beta receptors?
Equally effective on both
29
What effect does adrenaline have when given locally?
vasoconstrictor effect - action on Alpha-receptors
30
What systemic effect does adrenaline have?
it lowers TPR (total peripheral resistance)
31
What effect does adrenaline have on mean arterial BP?
little to no effect
32
Which receptor is nodrenaline more effective on?
Alpha-receptors
33
Systemically, noradrenaline has what effect on TPR?
Icreases TPR (alpha>Beta)
34
What effects does noradrenaline have on mean arterial BP?
Raises it
35
Does adrenaline or noradrenaline sometimes cause a fall in BP
noradrenaline
36
What are ester types of LA broken down by?
tissue esterases - action of esters is quite brief
37
What are amide types of LA broken down by?
Liver amidases - action of amides has a longer duration
38
What modes of administration are used in dentistry?
Surface application - topical Local infiltration Regional nerve block
39
What LA preparations are used in dentistry?
Lignocaine: 2% lignocaine HCl, 2% lignocaine HCl + 1:80,000 adrenaline Prilocaine: 4% prilocaine HCl, 3% prilocaine HCl + felypressin (0.03 U/ml)
40
What is the formula for % solutions?
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
What is the maximum dose of lignocaine allowed?
approx 4mg per kg bodyweight
42
What preservatives are used in LA preparations?
Bisulphite and Propylparaben
43
Which preservative can cause an issue in patients that have asthma?
Bisulphite
44
What is the process of preparing to giving LA? (8)
``` 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
How should the patient be prepared for LA?
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
What is the technique for giving an injection?
``` 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
Injection site for buccal infiltration?
Below apex of tooth
48
What are the limitation of infiltrations?
Infection may limit effect | Dense bone may limit effect
49
What are positives of buccal infiltrations?
High success rate Technically easy Atraumatic
50
Buccal infiltration technique?
``` Stretch cheek Puncture mucosa, bevel open towards bone Advance to needle to over apex of tooth Withdraw slightly if bone contact Aspirate ```
51
What is the technique for a palatial injection? (6)
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
What os the Posterior Superior Alveolar branch effecting in achieving anaesthesia for?
Pulpal anaesthesia for First, second and third maxillary molars
53
Where is the needle inserted for PSA injection?
MB fold over 2nd maxillary molar
54
What percentage of population has Middle Superior alveolar nerve?
28%
55
What is the target injection area for Anterior superior alveolar anaesthesia?
MB fold over 1st premolar - target is infraorbital foramen
56
What buccal approach blocks are there for maxilla?
PSA - posterior superior alveolar MSA - middle superior alveolar ASA - anterior alveolar nerve
57
What is anaesthetised through greater palatine injection?
Posterior part of hard palate and overlying soft tissues as far as first premolar & medically to midline
58
What is anaesthetised through nasopalatine injection?
Anterior portion of hard palate (soft & hard tissue) bilaterally from mesial of right first premolar to the mesial of left first premolar
59
What LA injections are performed as buccal infiltrations in the mandible?
Mental nerve block | Buccal injection
60
What is the target area for mental nerve block?
Between apices of lower premolars
61
What is the target area for buccal injection in the mandible?
Lower buccal gingivae, slightly distal to the tooth to be treated
62
What are the important landmarks for Inferior alveolar nerve block?
Coronoid notch of mandibular ramus Posterior border of mandible Pterygomandibular raphe Lower premolar teeth of opposite side
63
IANB - what is the site of anaesthetic deposition?
Region of the mandibular foramen
64
What are the limitations of Inferior Alveolar nerve block?
Increased onset time Increased lingual nerve injury No change in intramuscular injection
65
What is the technique for IANB?
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
IANB - What should be done if bone contact too soon or not at all?
Too soon - reposition syringe barrel mesial lay Not at all - reposition syringe barrel distally
67
How could a patient describe feeling anaesthetised?
Rubbery Numb Tingly Swollen
68
Via infiltration, how long does pulpal anaesthesia last? (List w/times)
Articaine 4% - up to 120 mins Lignocaine HCl 2% - 60 mins Prilocaine HCl 3% - 30-45 mins Mepivicaine 3% - 20mins
69
Via block, what is the duration of pulpal anaesthesia? (List w/times)
Lignocaine HCl 2% - 90 mins Articaine HCl 4% - 75mins Prilocaine HCl 3% - 60 mins Mepivicaine 3% - 40 mins
70
What is the duration of soft tissue anaesthesia with different anaesthetics?
Prilocaine HCl 3% - 3-6 hours Articaine HCl 4% - 3-5hours Lignocaine HCl 2% - 3-5 hours Mepivicaine 3% - 2 hours
71
Mepivicaine - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.
``` Pulpal anaesthesia Infiltration - 20mins Block - 40 mins Soft tissue 2 hours ```
72
Lignocaine HCl 2% - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.
``` Pulpal anaesthesia Infiltration - 60mins Block - 90mins Soft tissue anaesthesia 3-5hours ```
73
Articaine HCl 4% - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.
``` Pulpal anaesthesia infiltration - up to 120 mins Block - 75mins Soft tissue anaesthesia 3-5 hours ```
74
Prilocaine HCl 3% - what is the duration of pulpal anaesthesia (via infiltration & block) & soft tissue anaesthesia.
``` Pulpal anaesthesia Infiltration - 30-45mins Block - 60 mins Soft tissue anaesthesia 3-6 hours ```
75
Mepivicaine - vasoconstrictor?
None
76
Lignocaine HCl 2% - vasoconstrictor?
1:80,000 Adrenaline
77
Articaine HCl 4% - vasoconstrictor?
1:100,000 1:200,000 1:400,000 all adrenaline
78
Prilocaine HCl 3% - vasoconstrictor?
Felypressin (octapressin)

BDS2 OSCE (21 decks)

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