Pharmacology and Equipment

Question 1

Define anaesthesia

Answer 1

• Loss of sensation to circumscribed are of body by depression of excitation in nerve endings or an inhibition of conduction process in peripheral nerves
• Includes all sensation

Question 2

Define analgesia

Answer 2

Loss of only pain sensation

Question 3

Define local anaesthetic

Answer 3

Drug which reversibly prevents transmission of nerve impulse in region to which it is applied, without affecting consciousness

Question 4

How do LAs work?

Answer 4

Blocking conduction of action potentials along nerve fibres

Question 5

Describe the 3 parts to the structure of a LA

Answer 5

• A lipophilic aromatic portion
• An intermediate chaine (Amide or Ester)
• A hydrophilic amine portion

Question 6

What does the metabolism of an LA depend on?

Answer 6

Whether it is an amide of an ester

Question 7

Give some examples of amide LAs (5)

Answer 7

• Lidocaine
• Prilocaine
• Articaine
• Mepivacaine
• Bupivacaine

Question 8

How are amide LAs metabolised?

Answer 8

Metabolised mainly by the liver

Question 9

How are ester LAs metabolised?

Answer 9

Metabolised by pseudocholinesterase to PABA and excreted in urine

Question 10

What 2 factors affect proportion of charged to uncharged molecules following a LA injection?

Answer 10

• pH of tissues

- Dissociation constant (pKa) of the LA agent

Question 11

Comment on the link between infection and LA

Answer 11

Infection within the tissue can reduce pH and reduce effectiveness of LA

Question 12

What are the components of a LA? (5)

Answer 12

• LA agent
• Vasoconstrictor
• Reducing agents
• Isotonic solution
• Preservatives

Question 13

What is the role of reducing agents in LAs?

Answer 13

Stabilises vasoconstrictor by preventing oxidation

Question 14

What agents can act as vasoconstrictors in LA? (2)

Answer 14

• Adrenalin

- Felypressin

Question 15

What are some advantages of adrenaline as a vasoconstrictor? (3)

Answer 15

• Less bleeding at site
• Less systemic absorption, consequently lower toxicity
• Prolonged duration of action

Question 16

What are some disadvantages of adrenaline as a vasoconstrictor? (2)

Answer 16

• Potential to cause cardiac arrhythmia

- Caution needed in those with Heart Disease

Question 17

Explain the relationship between heat/light and LA storage

Answer 17

Exposure to excess heat or light causes breakdown of adrenaline so LA cartridges should be stored carefully

Question 18

When can felypressin be considered instead of adrenaline as a vasoconstrictor? (2)

Answer 18

• Patient has heart or blood pressure problems

- Patient has tendency to fainting

Question 19

What is a disadvantage of felypressin?

Answer 19

Causes uterine contraction and initiates labour

very unlikely in such a small dose

Question 20

What percentage lidocaine is used in practice?

Answer 20

2% (20mg/ml)

Question 21

How much adrenaline is in lidocaine?

Answer 21

1:80000

Question 22

What is the anaesthetic times provided by Lidocaine?

Pulp tissue?
Soft tissue?

Answer 22

• 45-60 mins pulp tissue

- 3-5 hours soft tissue

Question 23

What percentage prilocaine is used in practice?

Answer 23

3% (30mg/ml)

Question 24

What percentage articaine is used in practice?

What is its half life?

Answer 24

• 4% (40mg/ml)

- 20 mins

Question 25

Describe what you would you find on a LA cartridge (8)

Answer 25

• Contents
• Concentration
• Vasoconstrictor
• Expiry date
• Manufacturers name
• Batch number
• Plunger (rubber)
• Cap

Question 26

What are blue fine needles used for?

Answer 26

For infiltrations

Question 27

What are yellow thick needles used for?

Answer 27

For inferior alveolar nerve blocks

Question 28

What is the onset and duration of LA action dependant on? (5)

Answer 28

• pH of tissue
• Time of diffusion from needle tip to nerve
• Time of diffusion away from nerve
• Nerve morphology
• Concentration on drug, lipid solubility of drug