Local Anesthesia Flashcards
How do local anesthetics work?
By blocking sodium ion channels and decreasing sodium permeability in nerve cells.
What effect does blocking sodium have on nerve conduction?
Prevents depolarization and action potential propagation.
What is the result of local anesthetic action?
Nerve impulse transmission is blocked, resulting in no pain.
What does local anesthetic bind to in nerve membranes?
Calcium and sodium receptors.
What is a local infiltration?
Anesthetic deposited near nerve endings to numb a small area (1–2 teeth), e.g., maxillary infiltration.
What is a nerve block?
Anesthetic deposited near large nerve trunks to numb a larger area, e.g., inferior alveolar (IA) block.
What are ideal properties of a local anesthetic?
No adverse reactions, rapid onset, satisfactory duration, low cost, long shelf life, potent, reversible, non-irritating, easily metabolized and excreted.
Where are amide local anesthetics metabolized?
In the liver.
What are examples of amide anesthetics?
Lidocaine, Articaine, Mepivacaine.
What is a concern with amide anesthetics?
Impaired metabolism in liver disease (e.g., CHF, cirrhosis).
Where are ester anesthetics metabolized?
In the plasma by pseudocholinesterase.
What are examples of ester anesthetics?
Benzocaine, Tetracaine, Cocaine.
What is a concern with ester anesthetics?
Unstable; higher chance of allergic reactions.
How is local anesthetic absorbed?
Related to tissue vascularity; vasodilation occurs without epinephrine.
Are topical anesthetics effective on intact skin?
No, only effective on mucosa.
What tissues absorb anesthetic first?
Highly vascular tissues: brain, head, liver, kidneys, lungs, spleen.
Which tissue stores the largest percentage of local anesthetic?
Skeletal muscle.
Where are amide anesthetics metabolized?
In the liver.
Where are ester anesthetics metabolized?
In the plasma.
How are all local anesthetics excreted?
Via the kidneys.
What conditions pose a relative contraindication for local anesthetics?
Liver or kidney disease.
What are four benefits of adding epinephrine to local anesthetic?
Decreases systemic toxicity, slows absorption, prolongs duration, produces hemostasis.
What are three possible side effects of epinephrine?
Local ischemia, increased heart rate, anxiety.
What drugs can interact with epinephrine?
Beta-blockers and tricyclic antidepressants.
How can you reduce the risk of anesthetic toxicity?
Aspirate, avoid injecting into a vessel, use the lowest effective dose, inject slowly.
What is the recommended injection rate for local anesthetic?
1 cartridge per minute.
What is the primary use of topical anesthetics?
Pre-injection or site-specific anesthesia.
What is the typical depth of topical anesthetic penetration?
2–3 mm.
Give an example of a commonly used topical anesthetic.
18–20% benzocaine.
How long do topical anesthetics usually last?
10–15 minutes max.
Should topical anesthetic be rubbed onto tissue?
No, it should not be rubbed.
What makes topicals more risky than injectables?
Higher concentrations.
What are possible adverse reactions to topicals?
Excessive absorption, hypersensitivity, tissue trauma.
What are examples of local reactions to topical anesthetics?
Tissue sloughing, redness, burning, delayed hypersensitivity.
Are allergies more common with ester or amide topicals?
Esters.
What preservative in multidose topicals may cause allergic reactions?
Methylparaben.
What affects injection reliability?
Patient anatomy and proper use of palpation and landmarks.
What type of syringe is used for dental local anesthesia?
Breech-loading, metallic syringe.
What are dental needles made of and how many uses are recommended?
Stainless steel, pre-sterilized; change after 4 injections.
What does the blue needle (30 gauge) indicate?
Least rigid, smallest diameter.
What does the yellow needle (27 gauge) indicate?
Moderate rigidity and diameter.
What does the red needle (25 gauge) indicate?
Most rigid, largest diameter.
What is the typical length of a short dental needle?
25 mm, used for infiltrations.
What is the typical length of a long dental needle?
32 mm, used for mandibular blocks.
How much solution is in a dental cartridge?
1.8 mL (36 mg anesthetic).
What are the contents of a dental anesthetic cartridge?
Local anesthetic, vasoconstrictor (if included), sodium chloride, sterile water, sodium metabisulfite.
What is sodium metabisulfite used for in a cartridge?
It is an antioxidant that preserves the vasoconstrictor.
What are examples of supplemental armamentarium?
Topical anesthetic, gauze, applicator sticks, cotton pliers, hemostat.
What is the correct order for loading a syringe?
Inspect syringe → insert cartridge (rubber end first) → engage harpoon → attach needle → expel drops → ensure bevel faces bone → resheath needle.
What is the proper way to unload a syringe?
Resheath needle using scoop or safety device → retract piston → remove cartridge and needle then dispose in sharps
What type of sedation does nitrous oxide provide?
Conscious sedation (analgesic/sedative), not a true anesthetic.
How is nitrous oxide eliminated from the body?
99% is eliminated via the lungs.
What cardiovascular effect does nitrous oxide have?
It depresses myocardial contractility.
Is nitrous oxide metabolized in the liver?
No.
What respiratory effect does nitrous oxide have?
Minimal depression.
What can prolonged N₂O use cause?
Vitamin B12 depression, anemia, and neuropathy.
What are some nitrous oxide delivery safety features?
Alarm systems, pin indexes, oxygen fail-safe valves, minimum oxygen flow of 30%.
What are signs of ideal sedation with nitrous oxide?
Slightly depressed or unchanged BP & HR, vasodilation (flushing), decreased muscle tone.
