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BDS2; Integrated Clinical Practice > ICP L31: LA Pharmacology and equiptment > Flashcards

ICP L31: LA Pharmacology and equiptment Flashcards

1
Q

Define anaesthesia

A

The loss of all sensation to a circumscribed area of the body by depression of excitation in nerve endings/ inhibition of conduction process in peripheral nerves

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2
Q

Define analgesia

A

The loss of pain sensation ONLY (nociception)

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3
Q

What is LA

A

Drug which reversibly prevents transmission of the nerve impulses to a region in which it is applied without affecting consciousness like GA

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4
Q

How does LA work

A

Produces loss of sensation as it prevents pain in a defined area by

  1. Blocking conduction of APs along nerve fibres
  2. Blocking entry of Na+ ions needed for membrane depolarisation (and so APs) meaning that the pain sensation from the tooth is not transmitted to the brain
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5
Q

Outline the structure of LA

A
  • Aromatic lipophilic part
  • Intermediate amide/ester chain
  • Hydrophobic amine portion
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6
Q

What is the metabolism of LA dependant on

A

The intermediate carbon chain between aromatic lipophilic and amine hydrophobic portions (whether it is an ester or amide)

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7
Q

How do amide intermediate carbon chains affect LA metabolism

A

These remain stable in the blood and are metabolised in the liver therefore if the patient has reduced hepatic function it will predispose toxicity

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8
Q

Give examples of amide LAs

A
  1. Lidocaine
  2. Bupivacaine
  3. Articaine
  4. Mepivacaine
  5. Prilocaine

All UK LA dental cartridges are amides

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9
Q

How do ester intermediate carbon chains affect LA metabolism

A

These are rapidly broken down by pseudocholinesterase in the plasma so have a short duration of action and an increased allergy potential

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10
Q

Give examples of ester LAs

A
  1. Procaine (Novocaine)

2. Benzocaine (used as a topical anaesthetic gel)

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11
Q

Describe the mechanism of action of LAs in regards to charges

A

They are weak bases so in solution some molecules are charged and others uncharged -

Uncharged molecules pass through nerve cell membranes which re-equilibriates to charged/uncharged molecules inside the nerve

Inside nerve cells the molecules must be charged to bind to specific receptors and block sodium entry

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12
Q

List the constituents of LA

A
  1. LA agent
  2. Vasoconstrictor (adrenaline/epinephrine/felypressin)
  3. Reducing agents (stabilise vasoconstrictor by preventing oxidisation)
  4. Isotonic solution (modified Ringer’s solution)
  5. Preservatives
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13
Q

Why is adrenaline included in LA (3)

A

It is a local vasoconstrictor which controls blood flow by reducing the vessel size - thus ensuring less bleeding at the operative site (local infiltration) and less systemic absorption (lowers toxicity which allows higher dosages) and it also prolongs the duration of action

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14
Q

When can the vasoconstrictor part of LA be contraindicated

A
  1. Adrenaline in unstable angina and uncontrolled arrhythmias
  2. Felypressin in late-stage pregnancy because it causes uterine contraction
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15
Q

What are the adverse effects of adrenaline in LA

A

Adverse effects occur due to B1 adrenergic stimulation

  1. Increases HR + stroke volume = increased CO
    - this can cause cardiac arrhythmias
    - take caution with those who have heart disease
  2. Exposure to XS hear/light causes adrenaline breakdown so needs to be stored carefully
  3. Plain solution LAs don’t contain vasoconstrictor
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16
Q

Describe what lidocaine contains, its advantages and its duration

A

2% sol (20mg/ml) aka. Linospan/Xylocaine
1:80000 Adrenaline

  • most widely used LA
  • highly effective and low toxicity
  • has good tissue tolerance

Infiltration/block injections
Pulpal analgesia = 45-60mins
Soft tissues = 3-5hrs

17
Q

Describe what prilocaine contains and its duration

A

3% sol (30mg/ml) aka Citanest
Felypressin vasoconstricter (less effective at haemorrhage control than adrenaline)
Available as 4% plain solution

Pulpal analgesia = 45-60 mins
Soft tissues = 2-3 hours

18
Q

Describe what articaine contains, its usage and why

A

4% sol (40mg/ml) aka Septocaine/Septanest
1:200000/1:100000 Adrenaline

This is used when repeated injections are needed for a long procedure because it is partially metabolised in plasma and has a half life of 20 mins

19
Q

What is included in an LA cartridge and what should be checked before use

A

3 components = cylinder, plunger, cap (contains 2.2ml)

Check the

  • [anaesthetic]
  • [vasoconstrictor]
  • expiry date
  • manufacturers name
  • batch number
20
Q

What are the different types of syringe

A

This is what accepts the LA cartridge and can be

  1. Conventional (separate needle and syringe)
  2. Safety syringe = reduces chances of injury by avoiding the need to resheath the needle
  3. Intraligamental
  4. Computerised
  5. Power injections

White handles = disposable
Black handles = sterilised and reused

21
Q

What should the cartridge be checked for

A

Shouldn’t contain air bubbles and should be cloudy (indicates bacterial contamination)

22
Q

Describe the LA needle

A 
Sterile stainless steel (coated silicon)
Beveled (chevron)
Plastic sheath 
- Short = 25mm
- Long = 35mm
23
Q

When is a finer gauge (30) needle used (BLUE)

A

For infiltration anaesthesia

24
Q

When is thicker gauge (27) needle used (YELLOW)

A

Inferior dental blocks

25
Q

What is topical anaesthesia and what does it contain

A

Applied to the mucus membrane = Benzocaine ester gel or Lignocaine spray/ointment

26
Q

What is infiltration anaesthesia

A

A submucosal injection to act on local nerve endings adjacent to the tooth apex and where the bone is porous enough to allow for this

27
Q

What is a nerve block/ regional anaesthesia

A

Used for blocking the passage of pain along nerve trunks by injecting anaesthetic solution around it at a site where the nerve is normally unprotected by bone

28
Q

Why would a nerve block/regional anaesthesia be used

A

When the cortical plate of bone is too thick to allow for infiltration anaesthesia

29
Q

When is topical anaesthesia used

A
  • Prior to needle penetration
  • Reduces the discomfort of infiltration anaesthesia
  • Makes no difference when used for nerve vlocks
30
Q

What does the volume of LA required depend on

A

The administration route of LA

31
Q

How much LA is needed for an infiltration

A

0.5ml

32
Q

How much LA is needed for a block

A

2ml

33
Q

How much LA is needed for a long buccal injection

A

0.2-0.5ml

34
Q

How much LA is needed for a palatal injection

A

0.2-0.5ml

35
Q

What does the onset and action of LA depend on (6)

A
  1. pH of tissue
  2. pKa of drug
  3. Time of diffusion from needle tip to nerve
  4. Nerve morphology
  5. Drug concentration
  6. Lipid solubility of drug

BDS2; Integrated Clinical Practice (25 decks)

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