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Local Anaesthetic > Local Anaesthetic > Flashcards

Local Anaesthetic Flashcards

Definition

1
Q

Define Local Anaesthetic

A

A drug which makes nerve tissue incapable of transmitting an impulse on stimulation by blocking the nerve conduction along the nerve axon.

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2
Q

How does local anaesthetic work

A

Local anaesthetic causes a reversible block to conduction along nerve fibres by blocking the entry of sodium ions into the sodium channels within the nerve axon membrane wall therefore preventing depolarisation and the transmission of pain stimulus

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3
Q

Action of Local Anaesthetic

A

Diffusion across plasma membrane then:
1) Ionized anaesthetic binds to sodium channel

2) Sodium entry is blocked into theses channels
3) Sodium channel blockade prevents initiation of action potentials
4) Lack of initiation blocks pain sensation due to signal not being transmitted to brain

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4
Q

Action of Local Anaesthetic

A

1) Ionized anaesthetic binds to sodium channel
2) Sodium entry is blocked into theses channels
3) Sodium channel blockade prevents initiation of action potentials
4) Lack of initiation blocks pain sensation due to signal not being transmitted to brain

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5
Q

Nerve supply

A

Upper 8,7,6 - PSD - Buccal gingiva & tooth, greater palatine - palatal gingiva

Upper 5, 4 - MSD - Buccal gingiva & tooth, Greater palatine - palatal gingiva

Upper 3,2,1 - ASD - Labial gingiva, tooth, nose & lip, nasopalatine - Palatal gingiva

Lower 3,2,1 - Incisive - Labial gingiva, tooth, chin & lip, Lingual - lingual gingiva, Mental nerve - buccal gingiva

Lower 4,5 - ID block - tooth, Mental nerve - tooth/buccal gingiva, Lingual - lingual gingiva

Lower 6, 7, 8 - ID block - tooth, Long buccal - buccal gingiva, Lingual - lingual gingiva

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6
Q

What are Esters

A

Topical anaesthetic which is metabolised in blood plasma by cholinesterase, has higher incidence of allergic reaction, is less effective and is shorter acting than amides

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7
Q

What are Amides

A

Injectable anaesthetic which is metabolised via the liver (approx. 70%), has low incidence of allergic reaction, is potential for toxicity and overdose and can causes vasodilation of blood vessels

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8
Q

Reasons for LA usage

A

Controls pain, controls haemorrhage (vasoconstrictor), controls post operative pain, and can be used as a diagnostic tool

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9
Q

Define Analgesia & Anaesthesia

A

Analgesia is lack of pain

Anaesthesia is lack of sensation

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10
Q

Contents of an LA cartridge

A
  • Local anaesthetic agent
  • Vasoconstrictor
  • Reducing agent ( antioxidant)
  • Buffering agent
  • Ringers solution
  • Sterile water
  • Preservative
  • Fungicide
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11
Q

Local anaesthetic agent

A

an active agent which blocks the transfer of sodium ions across the nerve membrane and stops the transmission of pain messages.

Active LA agents are:

  • Lidocaine (Xylocaine, Lignospan)
  • Articaine (Septanest)
  • Mepivacaine (Scandonest)
  • Prilocaine (Citanest)
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12
Q

Vasoconstrictor

A

drug which decreases blood flow by constricting blood vessels, slows absorption into cardiovascular system, reduces systemic toxicity and increases duration of LA

Vasoconstrictors are:

  • epinephrine/adrenaline
  • felypression
  • no vasoconstrictor ( Plain LA)
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13
Q

Reducing agent (Antioxidant)

A

an antioxidant, sodium metabisulphite, which prevents oxidation of adrenaline resulting in a lower pH of LA solution

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14
Q

Ringer Solution

A

the LA vehicle containing sodium chloride to give an isotonic solution and sterile water as the dilutant making it soluble

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15
Q

Fungicide

A

the fungicide, Thymol, is use to reduce fungal growth

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16
Q

Common LA drugs

A

with vasoconstrictor- Epinephrine:

  • lidocaine 2% 1:80 000
  • Articaine 4% 1:200 000
  • Articaine 4% 1:100 000

with vasoconstrictor - Felypression:
- Prilocaine 3%

without vasoconstrictor -
- Prilocaine 4%

17
Q

Lidocaine 2% with 1:80 000 Epinephrine

A

Gold standard, 2.2ml cartridge, 60 - 90mins pulpal anaesthesia, 3-4hrs mucosal anaesthesia
Caution: (as it increases heart rate and blood pressure):
- severe hypertension
- unstable angina
- unstable cardiac rhythm

contraindications:

  • significant renal impairment
  • significant liver dysfunction
  • heart failure
18
Q

Articaine 4% with 1: 100 000 or 1: 200 000 Epinephrine

A

effective as lidocaine, is an amide and ester, shorter duration, diffuses through soft and hard tissue better, metabolised in blood plasma, decreases systemic toxicity
Caution:
not to be used in pregnancy
not to be used for ID blocks (tissue necrosis)

19
Q

Prilocaine 3% with Felypressin

Prilocaine 4%

A

3% with felypression - similar to lidocaine but not as effective, reduces ability of blood to transport oxygen
Caution: to be avoided in pregnancy as it causes uterine contractions.
contraindications:
- significant renal impairment
- significant liver dysfunction
- heart failure

4% Plain - as above, can be used on pregnant & sickle cell anaemia patients

20
Q

Reasons for incomplete anaesthesia

A
  • local anaesthetic solubility and tissue pH factors
  • needle to jaw discrepancy i.e. Long-ID, Short- Infiltration
  • needle deflection, prevented by ensuring bevel toward bone
  • volume factors - large patient, thicker nerves
  • skeletal and neuroanatomic variations
  • LA or vasoconstrictor degraded
  • uncooperative/overwrought patient
21
Q

Ideal properties of LA agent

A
  • Specific action only on peripheral sensory nerves
  • Reversible action
  • Rapid onset
  • suitable duration of action
  • non-irritant
  • causes no permanent damage
  • no systemic toxicity
  • chemically stable
  • non- allergenic
  • non-addictive
  • sterilisable
22
Q

Efficacy of LA

A

Dependable on:

patient ( fears, phobias, past experience)
patient-operator relationship 
supplementary management (sedation)
operator technique
patient anatomy (can vary)
23
Q

LA Absorption

A

Topical - onto mucous membrane

Injection - into oral tissues

24
Q

Factors of anaesthetic dosage

A

1) patients physical condition (kidney/liver function for metabolic and excretory competence)
2) body weight

25
Q

Medically compromise indications

A 
Epinephrine/adrenaline:
 - use for everyone (+ cardiac patients)
large doses should be avoided in
- significant cardiovascular disease & if taking beta-blockers
- taking antidepressants
- taking anti-hypertensives and non-potassium diuretics
Avoid in:
uncontrolled hyperthyroidism
cocaine abusers
Felypression:
- hyperthyroidism 
- taking antidepressants
Avoid in:
- patients where you want control bleeding
- pregnancy
26
Q

Topical Anaesthetics

A

maybe indicated to minimize sensation from needle insertion or very brief relief from painful mucosal lesions

27
Q

Cartridge checks

A 
Date 
Cloudiness
Partly used
Large air bubbles
Pierced seal
Silicone rubber stopper - leakage, bulging- frozen/expanded 
Cartridge chipped
Contents stated clearly
28
Q

Allergies reaction more likely to Ester

A

The ester Procaine changes to para-aminobenzoic acid (PABA)and it’s the products from this that is associated with allergic reactions

Local Anaesthetic (1 decks)

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