Local Anaesthesia Flashcards
How do local anaesthetics work
Block the conduction of electrical impulses along the nerve fibers by decreasing the permeability of the ion channels to sodium ions
What is local anaesthesia ?
Loss of sensation in a circumscribed area of the body caused by a depression of excitation in nerve endings or an inhibition of the conduction process in peripheral nerves
What 3 molecules does local anaesthesia have?
Lipophilic end
Hydrophilic end
Link between the ends
Lidocaine properties ?
- potency of 2
- toxicity of 2
- onset of action is rapid within 2-3 mins
- long duration (1hr with vasoconstrictor)
Mepivacaine properties
- potency of 2
- toxicity of 1.5-2 (lower than lidocaine)
- onset of action is rapid within 1.5-2 mins
- moderate duration of action
- produces a longer duration of anaesthetic than most other LA without a vasoconstrictor
Prilocaine properties ?
- potency of 2
- toxicity of 1
- onset of action is 2-4mins
- less toxic than lidocaine
- great vasodilator properties
What are vasoconstrictors?
Drugs that constrict blood vessels and thereby control tissue perfusion.
Why are vasoconstrictors added to LA
To oppose vasodilator actions of LA. Vasoconstrictors contrarest the effects of anaesthetics as they are vasodilators
What is the importance of vasoconstrictors in dental procedures?
- decrease blood flow (perfusion)
- slow the absorption of LA into the cardiovascular system
- requires minimal anaesthetic solution -minimal risk of toxicity
- prolongs the anaesthetic in injected site
- decreases bleeding at administration site
What are systemic complications of LA
- fainting
- adverse drug reaction
- toxic reaction to LA -overdose
- allergic problems
- problems with vasoconstrictors
- cross infection
- bleeding disorder
- cardiovascular disorders
What are local complications of LA
•failure of anaesthesia
To operator : needle stick injury
To patient : soft tissue injury -lip bite
- nerve damage
- needle fracture
- oedema
- cartridge failure
- facial palsy
- infection
- haematoma
- pain of injection
Why do we not inject in an infected site ?
The acid in the pus counteract LA and therefore LA will NOT work
Get antibiotics to minimize abscess
How can a hematoma be prevented ?
By using an aspirating syringe and aspirating the area before injecting the anaesthetic
- not just an aspirating syringe
- remove thumb to allow pressure from inside the tissues to get into the cartridge
- when you reach a blood vessel aspirate first
The rule of thumb for LA is?
Uses to know the maximum number of LA (in cartridges) you can give to a patient according to the patients weight
1cartridge for every 10kgs
What is the rule of 10 for mandibular blocks in children ?
Add the tooth number to the age of the child
If the sum is more than 10= IDB is given
If the sum Is less than 10= infiltration is given
Tells us wether a mandibular block may be used for a child.
Eg 7yo child with 75
So 7 +5=12 therefore a block is needed
