37: Local Anesthetic Agents Flashcards
loss of sensation limited to a local area or region of the body
local anesthesia
drug that blcoks generation and propagation of nerve impulse that results in reversible, regional loss of function
local anesthetic
advantages and disadvantages of perineural infiltration v. nerve block
- perineural requires larger amounts of drug
+ perineural is easy to do - nerve block requires more skill
+ less drug used in nerve block
injection of agent into CSF in lumbar subarachnoid space to reach the roots of spinal nerves that supply specific region
spinal block
more reliable than epidural, but time limited
injection of agent into extradural space and blockade of the nerve root as it passes through the space
epidural block
not time limited, can be used 4-7 days post op
primary MOA of local anesthetics
blockade of voltage-gated sodium channels
site of action of most clinically used drugs =
intracellular receptor and membrane expansion
“caine” =
local anesthetic
caine with two “i” in name =
amides
esters usually only have one i
t or f: all local anesthetics are acids
false
all local anesthetics are weak bases
most active form at sodium receptor =
form important for lipid penetration of membranes =
cationic form
uncharged base
smaller and more lipophilic local anesthetics are…
more potent
have faster rate of interaction with sodium channels
have longer duration of action
which of the two categories of local anesthetics is metabolized in the liver and has a longer-half life (longer duration of action)?
amides
esters are metabolized in the plasma and have a short duration of action
minimum anesthetic concentration Cm =
minimum concentration of drug for standard block
this is a relative standard of potency
increasing fiber size —> _______ Cm
increasing
smallest fibers are most sensitive and myelinated nerves are more sensitive than non-myelinated
increasing pH —> ________ Cm
decreasing
____ frequency nerves are more sensitive to anesthetics
higher
increasing Ca2+ concentration –> ______ Cm
increasing
why would you use a vasoconstrictor such as epinephrine with anesthetics?
vasoconstrictors reduce local blood flow and reduce systemic absorption and reduce toxicity, increased duration of action
**never inject LA with vasoconstrictor into areas with end arterioles (digits, toes, ear lobe, penis)
most important factor affecting the reversal of local anesthesia
absorption into circulation
drugs with _____ protein binding produce less toxicity
little
esters are metabolized in the plasma via ______ into ______
BChE
PABA * prone to allergic reactions
what is the treatment for LAST local anesthetic toxicity
intravenous lipid emulsion aka IntraLipid
forms a lipid sink to absorb circulation lipophilic toxin
which anesthetic can be given topically AND by injection?
lidocaine
most common epidural going to C-section when total motor block also desired
2% lidocaine
toxicity of lidocaine
potential for transient neurological symptoms TNS with spinal administration- pan and/or increased sensitivity to touch
clinical use for bupivacaine
- agent of choice for epidural infusion used for labor analgesia and postoperative pain
- excellent spinal anesthetic
clinical use for articaine
dental anesthetic
current use for cocaine
topical anesthetic for ENT procedures
topical only anesthesia due to enhanced lipid solubility
benzocaine
clinical use for chloroprocaine
used as epidural agent for labor anesthesia (especially cesarean section) due to lower risk of systemic toxicity or fetal exposure
encased bupivicaine that provides relief for up to 72 hr post op given as single dose injectio
exparel-liposome
lidocaine + prilocaine
EMLA eutectic mixture of local anesthetics
used as topical anesthetic on intact skin
tetracaine + adrenalin + cocaine =
TAC
topical used in pediatric emergency rooms
neurolytic agents are not reversible and achieve a permanent local anesthesia. what are their uses?
permanent block in terminal cancer or some other chronic condition
ethyl alcohol and phenol
