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BDS2: Anatomy > Local Anaesthetic > Flashcards

Local Anaesthetic Flashcards

0
Q

Name the connective tissue layers of peripheral nerves.

A

Epineurium
Perineurium
Endoneurium

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1
Q

What is the function of local anaesthetic?

A

Stop nerve conduction by blocking the voltage-gated Na+ channels. This blocks action potential generation and nerve propagation. The block persists so long as a sufficient number of Na+ channels are blocked.

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2
Q

What is the order in which the different nerve fibres are blocked by LA?

A

A delta (blocked first)
C
A beta
A alpha (blocked last)

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3
Q

What is the function of A alpha nerve fibres?

A

Sensory - proprioception
Motor - skeletal muscle
(myelinated)

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4
Q

What is the function of A beta nerve fibres?

A

Sensory - mechanoreception

myelinated

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5
Q

What is the function of A gamma nerve fibres?

A

Motor - muscle spindles

myelinated

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6
Q

What is the function of A delta nerve axons?

A

Sensory - mechano, thermo, chemo and nociceptors

myelinated

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7
Q

What is the function of C nerve axons?

A

Sensory - noci, thermo, chemoreceptors
Autonomic - postganglionic
(unmyelinated)

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8
Q

What are the three organic molecule components of LA?

A

Aromatic region (hydrophobic)
Ester or amide bond
Basic amine side chain (hydrophilic)
Mnemonic - BAE

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9
Q

How many nodes of ranvier should be blocked to ensure the LA will effectively block the AP?

A

At least 3

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10
Q

What is the general concentration used for dental LA injections?

A

2-4%

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11
Q

Name three esters.

A

Benzocaine (most commonly used)
Procaine (not often used due to allergies)
Cocaine (not often used as it’s hard to obtain)

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12
Q

What are esters used for?

A

Topical anaesthesia

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13
Q

Name 6 amides.

A

Lignocaine/Lidocaine - most commonly used
Prilocaine - used in cardiac patients & pregnant women
Articaine - lasts longer
Bupivacaine - lasts longer
Mepivacaine - not commonly used
Ropivacaine - difficult to access in the UK

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14
Q

Why are vasoconstrictors added to LA?

A

To increase duration of action. Most LA’s are vasodilators which will increase ‘wash out’ of LA due to increased blood flow. Vasoconstrictors contradict this effect.

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15
Q

Name the vasoconstrictors commonly used in LA.

A

Adrenaline

Felypressin (synthetic vasopressin)

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16
Q

How is ester type LA broken down?

A

By tissue esterases.

Action of ester LA is quite brief, broken down quickly.

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17
Q

How are amide type LA broken down?

A

By liver amidases.

Broken down more slowly so duration is longer.

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18
Q

What are the modes of administrating LA?

A 
Surface application (topical)
Injection
Local infiltration
Regional nerve block
Nerve root block (e.g. spinal, epidural)
Intravenous
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19
Q

What is the maximum dose for lignocaine?

A

4mg per kg of body weight

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20
Q

What is the maximum dose for adrenaline?

A

500 ug (B.N.F.)

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21
Q

What are the LA preparations for dental injections?

A 
Lignocaine:
2% lignocaine HCl
2% lignocaine HCl + 1:80000 adrenaline
Prilocaine:
4% prilocaine HCl
3% prilocaine HCl + felypressin (0.03U/ml)
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22
Q

What is an adrenergic receptor?

A

G-protein coupled cell membrane receptors which receive neuronal impulses from postganglionic adrenergic fibres of the sympathetic nervous system.
Two main types:
Alpha - which act in response to sympathomimetic stimuli, in general is excitatory of the function of the host organ/tissue
Beta - which block sympathomimetic activity, in general is inhibitory

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23
Q

What does a posterior superior alveolar nerve block anaethnetise?

A

The pulpal tissue, corresponding alveolar bone, and buccal gingival tissue to the maxillary 1st, 2nd and 3rd molars.

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24
Q

What is meant by infiltration anaesthesia?

A

LA produced by injection of the anaesthetic solution directly into the area of terminal nerve endings.
Used to anaesthetise soft tissues.
Used to produce pulpal anaesthesia where alveolar bone is thin.
Cannot achieved in the mandible due to the thick cortical bone - except in the anterior teeth.

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25
Q

What possible complications can arise from LA?

A

Needle breakage, pain on injection, burning on injection, persistent anaesthesia/parathesia, trismus, haematoma, infection, oedema, tissue sloughing, facial nerve paralysis, post-anaesthetic intra-oral lesion (herpes simplex, aphthous stomatitis), toxicity, allergic reaction

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26
Q

What tissues would you anaesthetise when restoring a tooth?

A

Pulp

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27
Q

What tissues would you anaesthetise when scaling?

A

Gingivae and maybe pulp

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28
Q

What tissues would you anaesthetise when extracting a tooth?

A

Pulp and gingivae

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29
Q

How would you anaesthetise mandibular lingual gingivae?

A

Inferior alveolar nerve block.

Infiltration - of the mental nerve?

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30
Q

What effect does LA have on the CVS?

A 
Myocardial depression
Decreased excitability
Decreased force of contraction
Vasodilation (arterioles)
Direct effect of vascular smooth muscle
Inhibition of sympathetic system
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31
Q

What is the maximum dose of lignocaine, with and without adrenaline?

A

With - 4.5mg/kg

Without - 3mg/kg

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32
Q

What is the effect of adrenaline on the heart?

A

Increased HR, force, output, excitability (Beta 1 receptors)

33
Q

What is the effect of adrenaline on blood vessels?

A 
Coronary dilation
Skin contraction (alpha receptors)
Muscle dilation (beta 2 receptors)
34
Q

What is adrenaline’s effect on blood pressure?

A

Systolic - increase
Diastolic - decrease
Overall little effect

35
Q

What are the signs of adrenaline overdose?

A 
Fear and anxiety
Trembling
Weakness
Dizziness
Pallor and sweating
Palpitations
Headache
36
Q

What would happen if you injected LA into the parotid gland (too far posteriorly) when trying to do an inferior alveolar nerve block?

A

LA acts on facial nerve resulting in facial palsy

37
Q

What are the signs that you have injected LA into an artery by mistake?

A

Skin blanching
Visual disturbance - temp blinds, diplopia
Aural disturbances

38
Q

What are the signs you have injected LA into a vein by mistake?

A 
Mostly adrenaline effects:
Palpitations
Anxiousness
Restlessness
Headaches
Sweating
Pallor
39
Q

What can you do to avoid injecting LA into a vein or artery?

A

Aspirate the needle before you inject to see if it draws back blood.

40
Q

What is more serious, injecting LA into a vein or an artery?

A

Artery.
Persistence of symptoms requires rapid specialist referral.
Arteries are v deep/not near the site of injection so it would be difficult to inject them.

41
Q

What length of needle would you use for infiltration LA?

A

Short - 25mm

42
Q

What length of needle would you use for a nerve block?

A

Long - 35mm

43
Q

What is a nerve block?

A

Anaesthetic deposited beside nerve trunk.
Abolishes sensation distal to the site.
Used to produce soft tissue anaesthesia.
Used where bone is to thick to allow infiltration.
e.g. Inferior alveolar nerve block

44
Q

What preservatives can be added to LA?

A

Bisulphite

Propylparaben

45
Q

What is the purpose of adding preservatives to LA?

A

Prolongs the shelf life

46
Q

What is the issue with adding preservatives to LA?

A

Potential to cause allergies

47
Q

When would you anesthetise the palatal gingivae?

A

Extraction
Large restoration requiring a matrix band or clamp
Subgingival scaling
6 Point Pocket Chart

48
Q

How would you anesthetise the buccal gingivae in the maxilla?

A

Buccal infiltration

49
Q

How would you anesthetise the dental pulp in the maxilla?

A

Buccal infiltration

50
Q

How would you anesthetise the lower premolars and canine?

A

Mental (incisive) nerve block

51
Q

How would you anesthetise the lower canine and incisors?

A

Buccal/labial infiltration

52
Q

What injection should be used in conjunction with the IAN block to anesthetise the buccal soft tissue?

A

Long buccal nerve block

53
Q

How do you apply topical anaesthetic?

A

Dry mucosa
Apply with cotton wool
Leave for 1-3 minutes to allow it to take effect

54
Q

What is the purpose of topical anaesthetic?

A

Reduces patient discomfort and pain when you apply the needle.

55
Q

What temperature should LA be?

A

Patients cannot detect it if it is between 15 and 37 degrees C. If it is stored in a fridge then you must allow it to warm before it is used.

56
Q

If you get bony contact too soon when conducting an IAN block, what should you do?

A

Reposition syringe barrel mesially

57
Q

If you don’t get bony contact when conducting an IAN block what should you do?

A

Reposition syringe barrel distally

58
Q

When would you use intraligamental anaesthesia?

A

When the standard measures haven’t worked.

As an alternative to a nerve block if the patient cannot undergo one e.g. haemophiliac.

59
Q

What are the alternative IAN block techniques?

A

Gow Gates - anesthetises most of the V3 nerve branches

Akinosi - closed mouth technique

60
Q

What is LA used for?

A

Operative pain control
Diagnostic tool
Haemorrhage control

61
Q

What preparations of lidocaine is there for intraoral topical agents?

A

2% gel
10% spray
5% ointment

62
Q

How deep will intraoral topical agents anesthetise?

A

2-3mm

63
Q

What are the uses for intra-oral topical anaesthesia?

A 
Pre-injection
Rubber dam clamp
Placing matrix band
Suture removal
Exfoliating primary teeth
Subgingival scaling
Incision of abscess
64
Q

What are the different topical anaesthetic options?

A

EMLA cream - amide
Ametop gel - ester
Controlled release devices - patches

65
Q

What are the advantages of topical jet injectors?

A

LA up to 1cm

Bleeding diatheses - deep injections contraindicated

66
Q

What are the disadvantages of topical jet injectors?

A

Could cause soft tissue damage if careless
Frightening sight and sound
Taste of solution
Expensive

67
Q

What is TENS?

A

Transcutaneous electrical nerve stimulation.

Blocks large myelinated nerve fibres and closes the gate to central transmission of smaller unmyelinated pain fibres.

68
Q

When would you use prilocaine instead of lidocaine?

A

When the patient is allergic to latex as prilocaine is latex free.

69
Q

Which anaesthetic should you avoid using in nerve blocks?

A

Articaine as it is known to cause prolonged anaesthesia.

70
Q

When should you avoid using LA containing adrenaline?

A

Patients on diuretics - risk of reduction in potassium conc
Beta-blocker patients
Hypertensive patients?

71
Q

What is the lingula?

A

A ridge on the medial surface of the body of the mandible, just anterior to the mandibular foramen. If it is large you can mistake it for the mandibular foramen. If injected here the LA would not work as it would not reach the nerves.

72
Q

What is the pterygomandibular raphe?

A

A tendinous band between the hamulus of the medial pterygoid plate superiorly and the mandible inferiorly. It is the point of attachment for the buccinators and superior pharyngeal constrictor muscles.

73
Q

Where does V3 exit the skull?

A

Foramen ovale

74
Q

Where does V2 exit the skull?

A

Foramen rotundum

75
Q

Where does V1 exit the skull?

A

Superior orbital fissure

76
Q

What passes through the mandibular foramen?

A

Inferior alveolar nerve and artery

77
Q

What is the mental foramen?

A

Hole where the mental nerve and vessels exit the skull

78
Q

What are common complications of LA?

A

Fainting
Trismus
Facial palsy
Intravascular injection (intravenous or intra-arterial)

79
Q

When would you avoid using LA containing adrenaline?

A

CVD
Hyperthyroidism
Phaechromocytoma
Drug interactions - mono amine oxidase inhibitors, tricyclic antidepressants, beta blockers, non potassium sparing diuretics, halothane, cocaine

80
Q

What is the action of adrenaline?

A

Heart (beta 1 receptors) - FORE, increases force of contraction, increases cardiac output, increases heart rate, increases excitability
Blood vessels - coronary dilation, skin contraction, muscle dilation
Blood pressure - increases systolic, decreases diastolic, overall no effect
Lungs - bronchial muscle relaxation

BDS2: Anatomy (2 decks)

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