Local Anesthetics Flashcards
cocaine procaine chloroprocaine tetracaine benzocaine
esters:
hydrolysis by plasma and tissue cholinesterase
higher allergy incidence - cross allergy to all esters
shorter acting
lidocaine prilocaine ropivacaine bupivicaine articaine mepivacaine
amides
metabolized by liver CYP1A2 CYP3A4
low allergy incidence - no cross allergy
longer acting - more lipophilic and protein bound
general structure of local anesthetic
hydrophilic (quaternary amine)
lipophilic (benzene ring)
intermediate chain
local anesthetic ionization
hydrophilic side can become ionized
need to be non-ionized to pass through cell membrane, then need to ionize to attach to Na channel receptor
local anesthetic pKa tells _____
onset time
the closer to 7.4, the faster the onset
addition of epinephrine
decreased absorption into systemic circulation
decreased onset time and peak plasma concentration
increased motor and sensory blockage, duration, and area
procaine
1%
14 mg/kg
short
chloroprocaine
3%
11 mg/kg (14)
tetracaine
1%
1 mg/kg
long
cocaine
4%
3 mg/kg (topical)
200 mg total
*high toxicity, use only as topical
blocks reuptake of epinephrine
lidocaine
1% or 2%
4 mg/kg (7)
medium
mepivacaine
2%
4 mg/kg (7)
medium
prilocaine
3%
7 mg/kg (8.5)
medium
bupivicaine
- 75% - not allowed in US
- 5 mg/kg (3.2)
**binds preferentially to cardiac receptors
long
ropivicaine
0.75%
3 mg/kg (3.5)
long
local anesthetic - ion trapping
trapped in acidic locations - fetal pH lower, in acidosis trapper in brain
give with CO2, lowers pH in nerve cell thereby ionizing anesthetic once in cell
give with bicarbonate, more non-ionized to transport into cell
local anesthetic toxicity
- lightheadedness, tinnitus, circumoral and tongue numbness
- visual disturbances
- muscular twitching
- convulsions
- unconsciousness
- coma
- respiratory arrest
- CVS depression
usually occurs within first 5 minutes
local anesthetic toxicity treatment
- airway management
- benzos for seizures
- during CPR: small doses of epi, no vasopressin or calcium channel/beta blockers
- lipid emulsion therapy: 1.5 ml/kg 20% bolus, infusion 0.25 ml/kg/min for 10 minutes — if not stable, repeat bolus, increase infusion to 0.5
tumescent anesthesia
used by plastic surgeons - 35-55 mg/kg of lidocaine with epinephrine for liposuction, 28 mg/kg for others
monitor for 12-16 hours
max dose of epinephrine
3-4 mcg/kg
epinephrine metabolism
- monoamine oxidase
- roughly 20 minutes
