Local Anesthetics Flashcards
3 components of the LA molecule
lipophilic
intermediate
hydrophilic
aromatic portion of LA molecule
membrane penetration
lipophilic
ester/amide portion of LA molecule
metabolic pathway
alter tonicity
intermediate
amine portion of LA molecule
ionizable
determine charge
hydrophilic
2 types of LA
ester A
amide B
at normal body pH, LA are largely in the __ form
charged cationic
metabolic pathway of ester A
plasma
AND
liver
metabolic pathway of amide B
liver → CYP450
LA are classified as weak __
bases
uncharged LA are __ and cross membranes
lipophilic
injected LA are __ and block Na channels
hydrophilic
effect of infxn/inflammation on LA
infxn/inflammation → decreases pH → increased cationic/charged LA form → decreased membrane passage → decreased pain relief → increased dose required
t/f: buffered LA are more effective
T!
2 esters A
tetracaine
benzocaine
3 amides B
lidocaine
mepivacaine
bupivacaine
bc esters are metabolized by plasma and liver, they have __ duration than amides
and higher risk for __
shorter
allergic rxn
what 2 conditions increase t½ of amides 3x
liver dz
HF
3 factors that affect differential nerve block effectiveness
fiber size
firing rate of fibers
location of fibers
most important factor in effectiveness of differential nerve block
fiber size
which type of fiber is affected first in differential nerve block
small
2 smallest pain fibers
sensory pain
PG sympathetic
affected 1st in nerve block
what increases the effect of nerve bocks
neuron firing rate
what type of pain fiber has the fastest firing rate
active sensory pain fibers
what do you think when you see, dose dependent blockade
increased effectiveness of nerve block with faster firing rate of active sensory pain fibers
in terms of location, which type of pain fiber is affected first
periphery
2 types of pain transmission fibers
A delta
C
describe A delta fibers (2)
myelinated
big
describe C pain fibers (2)
unmyelinated
small
3 factors that decrease absorption of LA
oral
topical
intact skin
3 factors that increase absorption of LA
broken skin
injxn → SC/IM/IV - not infiltration
vasoconstrictors
which has higher distribution, amides or esters
amides →
cross bbb/placenta
distribution of amides is __ in healthy people,
which causes initial __ blood levels
increased
lower
esters are metabolized __ than amides,
resulting in __ potential for toxicity
faster
lower
__ have higher potential for liver toxicity
amides
blood concentration of LA depends on (4)
injxn rate/route/site
dose
liver dz
vasoconstrictors
s.e of esters
allergic rxn
common s.e of lidocaine
dizzy
drowsy
s.e of lidocaine at higher doses
convulsions
CNS dpn
death
tx for convulsions caused by lidocaine
diazepam
midazopam
route of amide administration w. highest risk of methemoglobinemia
topical
2 LA w. highest risk for methemoglobinemia
lidocaine
benzocaine
tx for methemoglobinemia
IV methylene blue
surface use of LA
mucous membranes
large dose of LA under skin w. epi
infiltration
regional use of LA
nerve block
spinal use of LA
subarachnoid
2 types of epidural
lumbar
caudal
lumbar LA is used for
obstetrics
caudal LA is administered __
and used for __
above the coccyx
perineal/rectal procedures
esters to know
cocaine
chloroprocaine
tetracaine
benzocaine
least toxic ester
chloroprocaine
ester w. fastest onset
chloroprocaine
ester w. slowest onset
tetracaine
ester w. highest topical value
tetracaine
administration routes of tetracaine (3)
spray
solution
ointment
which ester is used topically at the dentist
benzocaine
s.e of benzocaine
methemeoglobinemia
which LA can be used topically on intact skin (2)
LMX-4
EMLA
which has faster onset, LMX-4 or EMLA
LMX-4
LMX-4 contains
lidocaine
EMLA contains
lidocaine/procaine
amides to know
lidocaine
mepivicaine
bupivicaine
lidocaine is same-same
xylocaine
which amide is mc administered via infiltration
lidocaine
meipivicaine is same-same
carbocaine
which amide has the slowest onset
bupivicaine
which amide has the longest duration
bupivicaine
list the amides in order of lowest to highest vasodilatory action
mepivicaine
lidocaine
bupivicaine
list the amides in order of safety in pregnancy from least to highest
mepivicaine
bupivicaine
lidocaine
which amide is cardiotoxic
bupivicaine
3 effects of vasodilation
increased blood to injection site
decreased effects locally
increased toxic systemic effects
4 effects of vasoconstrictors
decreased blood flow to injection site
decreased hemorrhage risk
decreased toxic effects of LA
epi dose for ASA I
1:100,000
200 mg
epi dose for ASA II-III
1:100,000
40 mcg
(cardiac comorbidities)
