Local anaesthetic

Question 1

How do local anaesthetic work?

Answer 1

Block sodium channels preventing nerve depolarisation

Question 2

What is formula of lidocaine and safe dose?

Answer 2

2% lidocaine + 1:80,000 adrenaline (2.2ml)
4.4mg/kg safe dose
2.2ml = 44mg lidocaine
20kg child = 88mg (2 cartridges)

Question 3

What is the formula of prilocaine and safe dose?

Answer 3

3% prilocaine 0.03IU felypressin (citanest 3%)
6mg/kg
2.2ml = 66mg prilocaine

Question 4

What is the formula of articaine and safe dose:

Answer 4

4% articaine + 1:100,000 adrenaline
7mg/kg
2.2ml = 88mg articaine

Question 5

What bodily system does local anaesthetic affect first?

Answer 5

Neurological system

Question 6

What are the most common side effects of LA?

Answer 6

Light headedness
Fainting (vasovagal)
Allergy = very rare usually due to preservatives

Question 7

What medications can interact with adrenaline?

Answer 7

Tricyclic antidepressants
Non cardio selective beta blockers - propranolol
Diuretics - non potassium sparing
SSRI’s and SNRI’s

No more than 2x2.2ml cartridges as higher doses may cause hypertension and arrhythmia

Question 8

Why should prilocaine not be used in pregnancy?

Answer 8

Can lead to methaemoglobinaemia leading to cyanosis and induce labour.

Question 9

What is the max dose of 4% articaine 1:100,000 adrenaline for 50kg patient?

Answer 9

350mg

= 7mg/kg x50

Question 10

What are the signs and symptoms of lidocaine over dose?

Answer 10

Circumoral numbness
Tinnitus
Facial tingling 
Restlessness
Vertigo 
Slurred speech 
Tonic clinic seizures