LA symposium

Question 1

What are the 3 uses of local anaesthesia?

Answer 1

• operative pain control
• haemorrhage control
• diagnostic tool

Question 2

What are the different types of topical anaesthesia?

(4)

Answer 2

• intraoral topical agents
• topical anaesthetics for skin
• conntrolled-release devices
• jet injectors

Question 3

What intraoral topical agents are available?

Answer 3

• lidocaine: 2% gel, 10% spray and 5% ointment
• benzocaine: 20% gel

Question 4

What topical anaesthetics for skin are available?

Answer 4

EMLA cream
* 5% eutectic mixture of prilocaine (amide) and lidocaine (amide)
* applied for at least 45 mins
* useful prior to GA or IV sedation

Ametop gel
* tetracaine (amethocaine) 4% gel (esther)
* faster onset than EMLA

Question 5

What non-pharmacological pain control options are available?

Answer 5

TENS (Transcutaneous Electrical Nerve Stimulation)
* blocks large myelinated nerve fibres and closes the gate to central transmission of smaller unmyelinated pain fibres

Hypnosis
* adjunct to LA

Question 6

List common LA solutions.

Answer 6

• Lidocaine 2% with 1:80 000 ephinephrine (amide)
• Lidocaine 2% plain (amide) (shorter acting)
• Prilocaine (Citanest) 3% with felypressin (octapressin) 0.03IU/ml (amide)
• Articaine 4% with 1:100 000 ephinephrinen (amide)
• Mepivicaine 3% plain (Scandonest)

Question 7

What are the contra-indications for lidocaine?

Answer 7

• heart block and no pace-maker
• allergy to LA (or corn)
• hypotension
• impaired liver function

Question 8

What is the function of ephinephrine in LA?

Answer 8

• vasoconstriction
• tachycardia
• increased blood pressure

Question 9

What is the anaesthetic drug choice for nerve blocks, and why?

Answer 9

Lignocaine 2% as articaine 4% carries higher risk of non-surgical paraesthesia

Question 10

Which anaesthetic drug should be avoided in sickle cell patients?

Answer 10

articaine

Question 11

What are the general complications of LA?

(5)

Answer 11

• psychogenic stress
• allergy
• toxicity
• drug interactions
• infections

Question 12

What is the maximum safe dose for lidocaine?

Answer 12

4.4mg/kg

plain and with adrenaline

Question 13

What is the maximum safe dose for prilocaine?

Answer 13

6.0mg/kg

plain and with felypressin

Question 14

What is the maximum safe dose for mepivicaine?

Answer 14

4.4mg/kg

plain and with adrenaline

Question 15

What is the maximum safe dose for articaine?

Answer 15

7.0mg/kg

Question 16

How to prevent LA complications?

Answer 16

• aspiration
• slow injection
• dose limitation

Question 17

Which classes of drugs may interact with LA?

Answer 17

• MAOIs (mono amine oxidase inhibitors)
• Tri-cyclic antidepressants
• Beta-blockers
• Non potassium sparing diuretics
• Cocaine

Question 18

Which LA should be avoided in pregnant mothers?

Answer 18

Avoid octapressin as this has the potential to induce labour

Question 19

What are local LA complications?

Answer 19

• failure to achieve anaesthesia
• prolonged anaesthesia
• trismus
• intra-vascular injection
• facial paresis