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FINALS - Pharmacology > Local Anaesthetics > Flashcards

Local Anaesthetics Flashcards

1
Q

Which type of nerve fibre is responsible for only mechanoreception?

A

A-beta fibres.

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2
Q

Which type of nerve fibre is responsible for chemoreceptors and nociceptors?

A

A-delta fibres.

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3
Q

Which type of nerve fibre is responsible for dull aching nociception?

A

C-fibres.

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4
Q

What is the mechanism of action by which local anaesthetics work?

A

They block voltage gated sodium channels, preventing sodium influx - thus stopping an action potential from being generated.

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5
Q

In which order will nerve fibres be affected by local anaesthetic?

A
  1. A-Delta fibres
  2. C-fibres
  3. A-Beta fibres
  4. A-Alpha fibres
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6
Q

What constituents can be found in a typical cartridge of 2% lidocaine?

A

Lidocaine Hydrochloride
Reducing agent
Preservatives
Vasoconstrictors

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7
Q

Why do local anaesthetics normally contain vasoconstrictors?

A

LAs tend to be vasodialators, which encourages diffusion of the active molecule.

A vasoconstrictor can be used to keep the LA in the targeted area.

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8
Q

What is the mechanism of action for adrenaline when given systemically - in relation to blood pressure?

A

Activates a-1 receptors, causing vasoconstriction.

However it also activates b-2 receptors causing vasodialation.

Overall little effect on blood pressure overall.

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9
Q

What is the mechanism of action for adrenaline when given locally?

A

It triggers both a-1 and b-2 receptors, however when given locally it acts more on a-1 receptors.

This leads to vasoconstriction in the local area.

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10
Q

What is the key clinical distinction between articaine and lidocaine?

A

Articaine is an ester based LA, lidocaine is an amide based LA.

Amide based LAs are typically safer and more predictable - with a lower chance of allergic reaction.

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11
Q

When is felypressin/octapressin contracindicated for use in LA?

A

Pregnent women as it may induce labour.

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12
Q

Why might preservatives within LA cartirgdges be of risk ro a patient?

A

Allergic reactions can happen, and bisulphite can trigger a patients asthma.

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13
Q

How does the gauge of needle relate to the size of lumen?

A

The lower the gauge, the greater the diameter of the lumen will be - and also the lower the risk of breakage.

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14
Q

What is the purpose of pulling back on the plunger before injecting LA into a patient?

A

Aspiration - you can check whether you are in a blood vessel before injecting.

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15
Q

What would you do in the event of positive aspiration?

A

Reposition the needle and aspirate again.

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16
Q

What areas of the mouth does an IDB with a lingual block anaesthetise?

A

Teeth up to the central incisor.
Buccal and Lingual soft tissue.
Lower lip and chin.

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17
Q

If you wanted to restore a lower 6 and use dental dam, what LA would you perform?

A

IDB or B/L Infiltrations

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18
Q

Why might a long buccal infiltration be advisable when giving an IDB for working on lower molar teeth?

A

The IDB isn’t that effective at numbing posterior buccal tissue - so invasive procedures involving the tissue could justify it.

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19
Q

What are the landmarks involved in performing an IDB?

A

Coronoid notch
Post. border of the mandible
Pterygomandibular raphe
Barrel over opposite premolars

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20
Q

Where is the mental foramen located?

A

Typically between the apex of the 4 and the 5.

21
Q

What does a mental block anaesthetise?

A

Lower teeth 5-1
Labial soft tissues
Lip and chin

22
Q

What is the target site for a nasopalatine block?

A

Incisive papilla

23
Q

What complications can arise from delivering local anaesthetic?

A

Psychogenic (fainting)
Interaction with drugs
Cross infection issues
Allergy
Collapse
Toxicity

24
Q

What causes a patient to faint due to psychogenic stress?

A

Lack of oxygenated blood to the brain.

25
Q

What are the clinical features of someone experiencing a faint?

A

Lightheadeness
Pallor
Beads of sweat
Bradycardia
Nausea
Pupil dialation

26
Q

How do you manage a faint?

A

Lay flat and raise legs
Loosen neck clothing
Ventilation
Sugar

27
Q

Which drugs can interact with LA when accidentally injected systemically?

A

MAOI Anti-deps
Tri-cyclics
B-Blockers
Non-potassium sparing diuretics
Cocaine

28
Q

Why might a patient have an allergic reaction to an LA injection?

A

Rarely allergy to the LA itself
Historically due to latex bung
The preservatives/anti-oxidents within the LA.

29
Q

What are the symptoms of a toxic LA overdose?

A

Convulsions
Loss of conciousness
Respiratory depression
Circulator collapse

30
Q

How many mg of lidocaine is there in a 2.2ml cartridge of 2% concentration?

A

2% = 2g/100ml
= 20mg/ml

Therefore there is 44mg in a 2.2ml cartridge.

31
Q

What is the maximum safe dose of lidocaine with adrenaline that can be given to a fit and healthy patient?

A

5mg/kg
or
50mg/10kg
Maximum dose in a 70kg male is 350mg.

32
Q

What is the maximum number of cartridges of lidocaine with adrenaline that can be given?

A

1 cartidge per 10kg body weight, approximately 7 in a 70kg man.

33
Q

What is the maximum dose of 4% articaine that can safely be given to a fit and healthy individual?

A

7mg/kg
or
70mg/10kg

34
Q

How many cartridges of articaine can be given to a 70kg male healthy patient?

A

5.

35
Q

How many mgs of 4% articaine is there in a 2.2ml cartridge?

A

88mg.

36
Q

What is the adrenaline concentration found in 4% articaine cartridges?

A

1:100,000

37
Q

What is the adrenaline concentration found in 2% lidocaine cartridges?

A

1:80,000

38
Q

What effect does adrenaline have on the sympathetic nervous system?

A

Increase in:
- HR
- MCF
- MCO
- Systolic BP

Decrease in:
- Diastolic BP
- Bronchial constriction

39
Q

What is a safe way of using adrenaline containing LAs in patients with cardio-vascular disease?

A

Use <3 x 2.2ml cartridges

40
Q

What risk is involved in giving LA to patients with hyperthryoidism?

A

Thryoid crisis.

41
Q

What risk is involved in giving LA to patients with phaeochromocytoma?

A

Hypertension

42
Q

List the potential local complications of giving LA intra-orally.

A

Failure to achieve anaesthesia
Prolonged anaestesia
Trismus
Haematoma
Intra-vascular injection
Blanching
Facial paresis
Broken needle
Infection
Soft tissue damage

43
Q

Why should articaine be avoided when performing an IDB?

A

There is evidence to suggest that 4% articaine has a higher risk of causing nerve damage than 2% lidocaine.

44
Q

Why might prolonged anaestesia occur?

A

Direct trauma from needle
Blunt needle
Chemical trauma from LA
Type of LA used

45
Q

How might an LA cause trismus?

A

Most likely damage to medial pterygoid, injection may be too low or forceful.

46
Q

What causes facial palsy when giving an IDB?

A

Injecting too far back, and therefore injecting into the parotid gland.

This causes VII-Facial nerve ganglion to be numbed, causing paralysis of one side of the face.

47
Q

How would you manage someone who has just been given a facial palsy from an IDB?

A

Reassure patient
Cover eye with pad until blink reflex has returned.

48
Q

What are the symptoms of an intravascular injection?

A

Heart palpatations
Anxiousness
Restlessness
Headache
Sweating
Pallor

FINALS - Pharmacology (10 decks)

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