1
Q
Define local anaesthesia
A
Loss of sensation to specific anatomical area
2
Q
What are the 2 main uses of LA in dentistry
A
- Enable surgical procedures to be undertaken
2. Provide analgesia
3
Q
Name the different way we can produce local anaesthesia
A
- Cooling sensation of topical application of ethyl chloride
- Pressure
- Try LA agents injected into nerve fibres
- Irreversabel blockades
4
Q
How can we administer local anaesthesia
A
- Topical
- Subcutaneous injection
- Nerve blockers
- Epidural
- Intrathecal
5
Q
What is an Intrathecal injection
A
Injecting directly into the subarachnoid space
6
Q
Name the first known substance used as LA
A
Cocaine
7
Q
Give examples of different local anaesthetics
A
- Lidocaine
- procaine
- Pilocaine
- Mepivicaine
- Ropivacaine
- Bupivicaine
- Articaine
8
Q
What do we often give alongisde the anaesthetic agents
A
A vasoconstrictor
9
Q
What are the benefits of administrating a vasoconstrictor
A
- Longer duration of LA
- Can reduce risk of CNS effects
- Greater anaesthetic affect so lower dose can be given
10
Q
Where should we not administer LA with a vasoconstrictor? why?
A
into extremities as there is a risk of significant local tissue hypoxia
11
Q
Name the 2 most common vasoconstrictors use din dentistry
A
- Adrenaline
2. Felypressin
12
Q
What us another name for adrenaline
A
Epinephrine
13
Q
What is another name for felypressin
A
Vasopressin
14
Q
How do adrenaline work
A
It stimulates alpha adrenoreceptors to constrict blood vessels
15
Q
Name the most common dental LA solution
A
2% lidocaine with 1:80,000 adrenaline
16
Q
What dow e mean by 2% lidocaine
A
20mg per ml
17
Q
When might LA with adrenaline be contraindicated
A
In patients with severe hypotension or an unstable cardiac rhythm
18
Q
If we can’t use adrenaline as a vasoconstrictor what can we use instead
A
Felypressin
19
Q
List the ideal properties of an LA
A
- Be reversible
- Have a high therapeutic index
- Have a short time of onset
- Last for a suitable amount of time for treatment
- Not have local irritant effects
- No side effects
- No potential to induce allergy
- Be applicable to any site
- Be cheap to manufacture, stable and soluble
20
Q
List some possible adverse effects of LA
A
- Hypersensitivity
- CNS effects
- Cardiac arrest
- Methaemoglobinaemia
21
Q
What is an allergic reaction to LA usually due to
A
The preservatives rather than the local
22
Q
List some early CNS effects LA can have
A
- light-headedness,
- dizziness,
- tinnitus,
- circumpolar numbness,
- abnormal taste,
- confusion,
- drowsiness
23
Q
List some late CNS effects LA can have
A
- tonic-clonic seizures,
- loss of consciousness,
- respiratory depression
- arrest
24
Q
What is Methaemoglobinaemia a very rare side effect to
A
Felypressin
25
What are the symptoms of Methaemoglobinaemia
1. Cyanosis
2. lethargy
3. Respiratory distress
26
When can Methaemoglobinaemiabe more risky
In a patient With angian or anaemia
27
How do we treat Methaemoglobinaemia
Be treated as a medical emergency give oxygen and call an ambulance
28
What is the max dose of lidocaine we can give for infiltration
4mg/kg
29
What is the max dose of lidocaine with adrenaline we can give for infiltration
7mg/kg
30
What is the max dose of Bupivicaine we can give for infiltration
2mg/kg
31
What is the max dose of Bupivicaine with adrenaline we can give for infiltration
3mg/kg
32
What is the max dose of Prilocaine we can give for infiltration
6mg/kg
33
What is the max dose of Prilocaine with adrenaline we can give for infiltration
8mg/kg
34
What is LA made up of
1. Aromatic ring
2. Intermediate linkage
3. Terminal amine
35
What does the aromatic ring do
It determines the degree fo solubility in the lipid membrane
36
What is the intermediate linkage
It usually consist of the amide or ester portion of the molecule
37
How can the terminal amine exist
In 2 forms:
1. Unionised
2. Ionised
38
What does an unionised terminal amine suggest
Lipid soluble molecule
39
What does an ionised terminal amine suggest
A water soluble molecule
40
Is LA an acid or base
A chemical weak base
41
What is the pKa of LA
8-10
42
What does pKa mean
The pH at which half the molecule is ionised and half is unionised
43
What does a pKa of 8 suggest
The the solution is mostly ionised at physiological pH.
44
What can affect how well LA is absorbed
Presence of infection or inflammation
45
How does the local anaesthetic produce an anaesthesia
Binds to the sodium channels so the rate of rise of the action potential is limited
The threshed for the receptor can therefor not be stimulates decreasing the rate of conduction of electrical impulse
46
How can inflammation affect LA effect
Can reduce LA effect
47
Why can inflammation affect lA effect
As inflammation produces an acidic environment
48
List the order of how LA creates a physical sensation
1. Cold
2. Warmth
3. Pain
4. Touch
5. Deep pressure
6. Motor function
49
What does the degree of neuronal blockade depend on
1. Neurone type,
2, concentration of LA use,
3. position of the fibres within the nerve
4. frequency of incoming impulses
50
List some local and regional effects of LA
1. Skin Blanching
2. Nerve function effected
3. Cranial nerve 7 effects
4. Cranial nerve 5 effects
5. Cranial nerve 6 effects
6. Further eye effects
51
What can skin blanching immediately upon placement indicate
Intrea arterial infection
52
For a fixed dose of LA nerve fibres with a small or large diameter more affected
Small diameter
53
Name cranial nerve VII
Facial
54
Is cranial nerve 7 sensory or motor
Both
55
When can their be cranial nerve 7 effects in dentistry
If you accidentally inject the parotid gland when giving an ID block
56
What can happen if you inject LA into the parotid gland when giving an iD block
Facial nerve palsy
57
What do the motor neurones of the facial nerve supply
1. Muscles of pharyngeal arch
| 2. Secretomotor to lacrimal, submandibular, sublingual and some minor salivary glands
58
What do the sensory neurones of the facial nerve supply
1. Taste fibres to the anterior 2/3rds of the tongue
| 2, Small area around the external auditory meatus
59
How can we mange facial nerve palsy
1. Recognition
2. Explain to the patient and reassure them
3. Protect the eye with an eye patch
4. Ensure safe discharge from the practice
5. Follow up
60
Name cranial nerve V
Trigeminal nerve
61
Is cranial nerve V sensory or motor
Both
62
What do the motor neurones of cranial nerve V supply
1. Muscles of the 1st pharyngeal arch (muscles of mastication)
2. Extra-cranial passage to neurones from cranial nerve 7 and 9
63
What do the sensory neurones of cranial nerve V supply
1. Extracranial passafe to neurones from cranial nerve VII
2. Nociception
3. Light touch sensation
4, temperature
5. Pressure
6. Proprioception to TMJ and muscles of the face
64
When might cranial nerve V effects occur
Inadvertent injection of LA into the lingual or IDN
65
Give examples of cranial nerve V effects
1. Immediate electric shock pain sensation
2. Direct trauma
3. Secondary haemorrhage
4. neurotoxicity
66
How can we mange cranial nerve V effects
1. Recognition
2. Explain to the patient and reassure them
3. Protect the eye with an eye patch
4. Ensure safe discharge from the practice
5. Follow up
67
Name cranial nerve VI
Abducens
68
What does cranial nerve VI supply
Visceral motor inner action to lateral rectus muscle
| Abducts the eyeball
69
When can cranial nerve VI effects occur
Inadvertent anaesthesia of the inferior orbital nerve may lead to transient lateral rectus palsy with diplopia
70
During which procedure are we most likely to have cranial nerve VI effects
Extraction of the upper third molar where we require LA placement in the posterior superior alveolar nerve
71
How can we manage cranial nerve VI effects
1. Recognise
2. Explain and reassure
3. Protect eye with eye patch
4. Ensure safe discharge
5. Follow up
72
Name a rare complication if infraorbital nerve block
Diminished accommodation of the lens of the eye leading to transient blurred vision
4th yr- CMS- Pharmacology and drugs
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