Local Anaesthetics Flashcards
Purpose of LA
-Pain control
Method of action of Local anaesthetics
- Block voltage gated sodium channels
- Block depolarisation of cell and inhibit neural activity
Structure of sodium channel
- Alpha 1 (pore through which sodium enters)
- Beta 1
- Beta 2
Number of variations of sodium channel
-9 different variations
Techniques of local Anaesthesia
- Topical
- Infiltration
- Regional block
- Intraosseous
- Intraligamentary
- Intrapulpal
Two types of local anaesthetics
- Esters
- Amines(mostly used)
Differences between esters and amines
- In metabolism and allergy production
- Esters metabolised in plasma
- Amines primarily undergo hepatic metabolism (prilocaine breakdown also in lungs, articaine metabolism in plasma)
Lidocaine
- Gold standard
- Plain solution of 2%-> short lasting
-Epinephrine vasoconstrictor common 1:200 000 to 1:80 000(5μg/m to 12.5μg/m)
Mepivicaine
-Concentration of 2% 1:100 000 epinephrine→ similar to 2% epinephrine lidocaine
3% plain (better anaesthesia than lidocaine when vasoconstrictor free solution required)
Prilocaine
- 4% plain solution
- 3% solution w/ vasocontrictor felypressin(if epinephrine free required)
Formulations of topical anesthetics
- Creams
- Ointments
- Sprays
Local anaesthetics agents commonly used as topical
- Lidocaine and Benzocaine
- Oraqix-Lidocaine and prilocaine
Technique for infiltration anaesthesia
- Mouth partly open
- Needle to depth of buccal sulcus(if bone contacted-slight withdrawal)
- Injection site supraperiosteal
- Aspiration and injection of 1-2 ml
Benefits of slow injection
- Reduces discomfort
- Increases success
- Lessens systemic problems
How long do infiltration injections last?
Pulps 45 mins and soft tissues 1.5-2 hours
Anaesthetic used in those allergic to amides
Procaine
Amide metabolised in plasma and therefore has shorter half life and is safer
Articaine
Articaine
4% 1:100 000 or 1:200 000 epinephrine
-Better mandibular infiltration anaesthesia than lidocaine
Bupivacaine
- long lasting
- 1:200 000
- Supplementary intraoral injection during general anaesthesia
- Reduces number of post-op analgesics required
Effect of Epinephrine in La
🔹Vasoconstriction
🔹Reduced bleeding
🔹Prolonged anaesthesia
Effects of Epinephrine injection into vessel
🔷Systemic absorption-systemic toxicity
🔹Cardiovascular effects- tachycardia , Hypertension, arrhythmias
🔹CNS effects- dizziness, tremors, seizures
🔹Local tissue ischemia->necrosis
Epinephrine effect on heart
🔹Secreted by adrenal glands
🔹Binds to beta adrenergic receptors on heart muscle cells
🔹Increases HR and strength of contractions->increased blood supply
🔹Raises Bp
Role of epinephrine in allergic reactions
🔸Inhibits release of inflammatory mediators
🔸Histamine, leukotrienes
How epinephrine counteracts effects of vasodilation and increased vascular permeability during allergic reactions
🔸Induces vasoconstriction and reduces vascular permeability
