Local Anesthesia Flashcards
How does local anesthesia work?
Blocks conduction of nerve impulses (action potentials) by selectively binding to voltage dependent Na ions
Types of local anesthesia agents
Amides and esters (acids)
Which types of local anesthesia agents are MC used?
Amides (i-caines like lidocaine, dibucaine, prilocaine)
Order of sensory blockade in nerves
- Pain
- Heat
- Cold
- Touch
- Pressure
- Motor
(nerves recover in REVERSE order)
What is the onset, action, duration, and intensity of anesthesia determined by?
- Nerve fiber diameter
- Presence of myelin
- pKa of the solution
- Total dose and rate of metabolism
In what direction does blockade move?
Proximal to distal
Which types of solutions diffuse more rapidly into tissue?
Non-ionized
How are amides metabolized?
Liver
caution w/CYP interactions
Are anesthetics vasodilators or vasoconstrictors?
Vasodilators EXCEPT cocaine
What does adding epi to an anesthetic achieve?
- Decreased blood flow
- Reduces systemic absorption
- Shortens onset
- Extends duration of action
- Allows larger doses by decreasing toxic potential
Where should epi be avoided on the body?
Penis Nose Fingers Toes (and ear)
What is the antidote to epi?
Phentolamine mesylate
Describe direct infiltration
- Inject dermis and subQ fat junction (immediate block)
- Inject epidermis or dermal-epidermal junction (block slow and painful)
- Digital nerve block (slower onset, larger nerve fibers)
When is topical cocaine used as an anesthetic?
For adult nasal mucosa, nowhere else!
Contraindications to topical anesthetics
- Infants, neonates
- Known hypersensitivity to catecholamines
- In combo w/MAO inhibitors
- Penis, Nose, Fingers, Toes (ear)
