Local Anaesthetic Flashcards
What is local anaesthetic?
It is the loss of sensation in an area of the body caused by a depression in the excitation of the nerves, or an inhibition of the conduction process in the peripheral nerves.
How does LA work?
LA blocks the conduction if electrical impulses along the nerve fibres by decreasing the permeability of the ion channels to sodium ions (Na+).
What are the 3 parts of LA molecules?
Lipophilic end
Hydrophilic end
Link between the ends (ester or amide)
What is vasodilation?
It is the widening of the blood vessels. It results from the relaxation of smooth muscle cells in the vessel walls.
Vasodilation decreases blood pressure.
What is vasoconstriction?
It is the narrowing of blood vessels from contraction of the muscular walls of the vessels.
The opposite of vasodilation.
All LA’s have vasodilation effects. What are these?
Increased perfusion at the site.
Increased absorption of LA.
Higher plasma levels of the LA.
Decreased depth of LA and decreased duration of action.
Increased bleeding at the site of treatment.
Why are vasoconstrictors added to LA?
They control tissue perfusion and oppose the vasodilatory actions of LA.
They decrease perfusion (blood flow).
Slow the absorption of LA into the cardiovascular system.
Prolongs anaesthesia in the site, meaning less LA needs to be used, therefore lowering toxicity levels.
Decreases bleeding at the administration and treatment site.
Most common vasoconstrictors used in dentistry..
Epinephrine Norepinephrine Phenylephrine Levonordefin Octapressin
5 things about epinephrine and adrenaline…
They are hormones produced by the medulla of the adrenal gland
Powerful vasoconstrictor.
Allow more anaesthetic molecules to diffuse to the nerve membrane and thus improves depth and duration of anaesthesia.
It is the most commonly used in dentistry
Primary action of epinephrine is on the smaller arterioles and pre-capillary sphincters.
5 things about norepinephrine and noradrenaline…
Hormone produced by the adrenal medulla.
Similar chemical and pharmacological properties to epinephrine
Produces intense peripheral vasoconstriction with possible dramatic elevation of the blood vessels.
Use of norepinephrine in dentistry is not recommended
Mixing epinephrine and norepinephrine should be absolutely avoided
What is phenylephrine used for?
Used as a nasal decongestant
Reduces the size of blood vessels (Vasoconstrictor)
Used in patients with hypotension to increase blood pressure
Not recommended for use in patients with high blood pressure.
Things about levonordefrin
Only found in cartridges containing mepivacaine 1:20,000
Levonordefrin weaker than epinephrine but 1:20,000 is 5x stronger than standard concentration of epinephrine.
Things about octapressin
Similar properties to vasopressin
Does not predicted ischemia (blanching) at the injection site
Comes in citanest 3% with octapressin
Name the esters and amides
Esters: procaine
Amides: articaine, bupivacaine, lidocaine, mepivacaine, prilocaine
3 things about LA
LA reversibly blocks conduction alone a nerve distal to the application site.
They are generally classified into chemical structure, rate of onset, potency and duration of action.
Chemically they are either aminoamides or aminoesters.
Procaine
Brand name novoacaine
Relatively weak with long onset of action and short duration
Ester (high risk of allergy).
Plain procaine provides no pupal anaesthesia.
Pot-1
Tox-1
Duration-15-30mins of s/t
Onset-6-10mins
High vasodilating properties - the most of all LA’s
Lidocaine
Brand names lignocaine, xylocaine, xylocar
Amide Most versatile and most used due to high potency, rapid onset of action and long duration. Has topical activity. Pulpal anaesthesia with plain LA is 5mins Pot-2 Tox-2 Onset-2-3mins Duration- 1 hour with vasoconstrictor 3-5hours s/t
Lidocaine 2% with epinephrine 1:50,000 and lidocaine 2% with epinephrine 1:100,000
1:50,000 is stronger and provides better haemostatic properties.
Mepivacaine (brand name scandonest)
Amide Pot-2 Tox-1.5-2 Onset- 1.5-2mins Pulpal anaesthesia- 20-40mins (plain) 60mins with vasoconstrictor 2-3 hours s/t plain 3-5hours s/t with vasoconstrictor
Mepivacaine 3% plain recommended for patients who cannot have vasoconstrictor and for short length appointments where pulp anaesthesia isn’t needed.
Mepivacaine 2% with levonordefrin 1:20,000 or epinephrine 1:100,000
Prilocaine (Brand name citanest)
Amide Pot-2 Tox-1 Onset 2-4mins Prilocaine plain pulpal anaesthesia 10-15mins, 1.5-2hours s/t, nerve block 60mins. Prilocaine with epinephrine 1:200,000 pulpal anaesthesia 60-90mins, 3-8hours s/t Less toxic than lidocaine Can be used as topical with lidocaine.
Don’t use in patients with idiopathic or congenital methamoglobinemia or patients taking acetaminophen
What is methemoglobinemia?
It is a blood disorder in which an abnormal amount of methemoglobin (a form of haemoglobin) is produced.
Methemoglobin cannot release oxygen.
Articaine (Brand name septanest, ubistesin)
Amide
Contains both amide linkage and Ester chain) more potent and lipid soluble. Short metabolic half-life.
Pot-1.5
Tox-0.6
Onset 1-5mins
Can cause methemoglobinemia and increased risk of mandibular paralysis.
Not for kids under 4y/o
Articaine 4% with epinephrine 1:100,000 pulp anaesthesia 60-70mins
Articaine 4% with epinephrine 1:200,000 pulpal anaesthesia 45-60mins
Bupivicaine (Brand name marcaine)
Amide Long duration Chemically similar to mepivacaine but more lipid soluble = more potent Tox- 4x less than lidocaine Pot-4x more than lidocaine Onset - 6-10mins Duration- 3-10hours
Bupivacaine 0.5% with epinephrine 1:200,000 pulpal anaesthesia 90-180mins, s/t 240-540 (good for full mouth reconstructions, implant surgery, extensive perio treatment and management of post op pain)
Not recommended for kids - biting!
Types of syringes
- Non disposable
- Safety syringes
- Breech loading-aspirating syringe and self aspirating
- pressure syringes
