Local Anesthesia Flashcards

Local anesthetic
Terms Definitions
1 cartridge
resting membrane potential
Topical Atiseptic
Topical Anesthetic
Applicator Sticks
Cotton Pliers are all examples of?
Additional armamentartium
Maxillary injection techniques include
Max. nerve block
Greater palatine
atypical pseudocholinesterase=no esters
methemoglobinemia=no prilocaine
liver disfunction=no amides
renal disfunction=no amides or esters
CVD=no vasoconstrictors in high dose (like racemic epi ging. cords)
hyperthyroid=no vasoconst. in high dose (like racemic epi. ging. cords)
muscle relaxant
produces respiratory arrest for 2-3 min
Name ester-linked LA:-hydrolyzed by plasma esterases-there is no esterase activity in the CSF so ester-linked LAs used for spinal anesthesia have a long duration of action (good)
pKa is?
dissociation constant
measure of molecules affinity for hydrogen ions.
Most common Syringes in Dentistry?
Vasodilation _______ duration of LA.
Vasoconstriction _______ duration of LA.
goes in incisive foramen
provides pulpal anesthesia from canine to canine!
Mepivacaine HCl
class: amide
metabolized: liver
*mild vasodilation (so more duration than other plain LA)
*rapid onset with 7.6 pKa
Multiple systemic diseases or moderately controlled syst. diseases
*Medical consult, review labs & meds
above 4.5 signs and symptoms are...
Amide LA's are biotransformed in the...
most paresthesias resolve within ___ weeks without tx
after oral (swallow) administration of LA, the gi tract hardly (if at all) absorbs the LA with the exception of one LA... which is it?
insertion of needle into foramen ________ liklihood of nerve injury
No systemic disease
*Can have conscious sedation
without PCP consult
Topical LA
greater concentration that injected LA
vascular absorption is rapid (no vasoconstrictor)
Concentration of VC
.01 mg/ml
.005 mg/ml
.02 mg/ml
1:100,000 is preferred over 1:50,000 for hemostasis unless really needed
doses of LA in
mg/kg or mg/lb
with only the hydroxyl (OH) =
Articaine HCl
class: amide
metabolized: both plasma & liver
pKa 7.8, rapid onset
*possess a thiopene ring
*claims: faster onset, increased success, increased parasthesia, diffuses through tissues better, infiltrate mandible (these haven't been proven)
*used to have paraben--now paraben free
• Larger gauge preferred because:
o Less deflection
o Greater accuracy
o Easier aspiration
o Less chance of breakage
The more lipophlic the LA, the _________ it will stay at a local site instead of spreading systemically?Longer/shorter
positively charged LA molecules exist as
(cation form)
(slow & rapid) increase in Na+ permiability thus Na+ rushes in
what does LA do to blood vessels?
malignangt hyperthermia
disorder where genetic variant alters response to certain drugs
mantle fibers tend to innervate more proximal regions... for the IA, what would that be?
signif. renal disease is a _______ contraindication to LA
What is the closed mouth technique called?
Problems with needles
Pain on insertion: use topical
Breakage: from bending typically
Pain on withdrawal: fishhook barb needle
Injury to pt. or operator:
Local infiltration
smaller area flooded with LA
terminal nerve endings
Depends on diffusion/bone (max. more effective)
treatment in same area as injections (ie interprox. papilla)
Tingling of lip indicates anesthesia of...
mental nerve
Which branch has both sensory and motor function?
The opthalmic nerve divides into three branches... name them...
Field block
near larger nerve branches
above apex of tooth
supraperiosteal (incorrectly called infiltration)
Maxillary Nerve Block:

for Premolars
ASA (0.9mL)

Greater Palatine (0.45mL)
Surface anesthesia for skin
Benzocaine-most lipophilic because you want to avoid rapid absorption from wounds and ulcerated surfaces and avoid dissemination into systemic circulation
Supraperiosteal points of interest
anesthetizes large terminal branches of dental plexus
not as effective w inflammation
high success
easy to do
usually atraumatic
.6 mL of solution
Can TA diffuse through broken skin and mucous membranes?
What is the earliest symptom of MH?
What is the key for managing MH in the dental office?
*dantrolene sodium and the use of "safe" drugs=successful dental experience
Antibiotic Prohylaxis Recommended in
prosthetic valves & grafts
previous endocarditis
complex congential heart disease
pulmonary shunts/conduits
other congenital malformities
valvular dysfunction
hypertrophic cardiomyopathy
mitral valve prolapse w regurgitation
What factors affecting induction time are NOT under the operators control?
diffusion constant
anatomical barriers
documented LA allergy=no LA of that chemical class
Bisulfite allergy=no vasoconstrictor anesthetic
25 gauge
preferred for all injections with high risk of positive aspiration
Even though all the heart responses are increased, there is an overall decrease in..?
cardiac efficiency
Class D Local Anesthetic
combination of receptor and receptor-independent mechanisms
most clinically useful anesthetic
exist in both charged and uncharged forms
90% of blocking cause by cationic form of drug (10% produced by base form)
Class C Local Anesthetic
Physico-chemical mechanism
exist ONLY in uncharged form (RN)
Membrane expansion
i.e. benzocaine
Nerve block produced by local anesthetic is called...
nondepolarizing nerve block
If solution runs into patients mouth during long buccal injection what should you do?
penetrate deeper
Continue injection
Name the ingredients of the anesthetic solution?
LA drug
Preservative for Vasopressor
Sodium Chloride
Distilled Water
Maxillary Nerve block:

PSA (0.9ml)

Greater Palatine (0.45mL)
people with atypical psuedocholinesterase can't hydrolyze
succinylcholine at normal rate cuasing prolonged apnea.
long tube of metal from tip of needle through the hub and penetrating diaphram
Topical Antiseptic's function is to?
decreause bacteria at injection site
Posterior Divisions of V3 include...
auriculortermporal, lingual nerve, IA, mylohyoid nerve,
Some LA have anticonvulsant properties ... which are they?
procaine, lidocaine, prilocaine, mepivacaine, and even cocaine
methemoglobin is
the ferric form of hemoglobin which is more firmly attached to the RCB and can't be released into the tissues
Which form is responsible for blocking Na+ channels?
RNH+ (cationic form)
core fibers tend to innervate more distal points of nerve distribution... for the IA, what would that include?
incisors and canines
epineural sheath/nerve sheath
surrounds the nerve
not a barrier to LA
Vazirani-Akinosi (closed mouth), aka tuberosity technique
situations w limited opening
difficult to visualize
no bony contact
ONLY closed mouth techn.
25 guage Long
BEVEL AWAY FROM RAMUS BONE (so toward midline)
25mm in
Factors in selecting a VC
length of procedure
need for hemostasis
medical status of patient
Surface anesthesia for the cornea:
must be non-irritating, water soluble, not causing mydriasis or corneal injury-Tetracaine, Proparacaine-water soluble because nerve endings not v deep, doesn't have to be lipophilic,plus you don't want the drug to get thru cornea into the iris and ciliary muscle disturbing vision
Larger needles (e.g. 25 gauge) have advantages over smaller needles... they are...
less deflection, easier aspiration
Local infiltration of the palate
anesthetizes soft tissue in area adjacent to injection
for hemostasis or sub ging procedures on one tooth
potentially traumatic
27 gauge rcommended
.2-.3 ml of solution
Buccal Nerve Block
Long Buccal points of interest
anesthetizes buccal tissue of molars
it's easy and successful
25 gauge
usually done right after IANB
long needle since you're going way back in the mouth (not way into tissues)
bevel toward bone
taut tissue =atruamatic
.3 ml
Care & Handling of Syringe
wash and rinse, autoclave, clean harpoon with brush, & every 5 autoclaves parts should be lubricated
Class A Local Anesthetic
agents acting on outer surface,
i.e. "biotoxins" (tetrodotoxin & saxitoxin)
Selection of LA based on
length of procedure
need for post-op pain
need for hemostasis
any contraindications
What are the average needle lengths of short & long needles?
20mm & 32mm
MSA points of interest?
high success
includes MB root of 1st molar
above max. 2nd premolar
.9 to 1.2 mL of solution (half to 2/3)
will fail if not at apex
hematoma may develop (RARE)
Trismus is caused by
injection trauma to muscles of\r blood vessels in the infratemporal fossa.
High pKa = ______ diffusibility

Low pKa=_______diffusibility
low (slow onset)
high (quick onset)
significant renal impairment ______ the potential for toxicity.
(because more accum. in the blood) --esp. cocaine
Relative refractory period
an impulse can be initiated, but only by a stronger than normal stimulus
Supraperiosteal or
any max tooth (1-2 teeth)- B
soft t & supporting bone NO

0.6 mL
27 short

target: apex of tooth
pt not expected to live 24 hrs w or wout operation
*hospitalized & dental care limited to palliative only
according to the author, what is the most important factor in preventing overdose reactions?
the rate of deposition
Which parts of a peripheral nerve are the biggest anatomical barriers to diffusion of LA?
perineurium and perilemma
(preineurium greates barrier to "penetration")
Greater Palatine Canal Approach to the maxillary nerve block
insert through greater palatine foramen
advance needle 30 mm
never force needle against resistance
deposit 1.8 ml
T or F:
Greater palatine, nasopalatine, and palatal infiltrations injections provide pulpal anesthesia to the teeth near the injection site.
False--but the AMSA and PASA provide extensive areas of pulpal and palatal
increasing pH (more alkaline) of LA solution can
(but it is unstable so ill suited for clinical use)
speed onset of action
increase effectiveness
be more comfortable
sympathomimetic drugs are classified by
presence or absence of a catechol nucleus
Order of sensitivity to LAs is as follows:
Pain > Temperature, Sympathetic postganglionic > Touch, Pressure, Motor
low pH of inflammed tissue=
low amount of RN form (slow onset & not much to blockade)
icreased toxicity
lower pH can produce two things.. they are...
burning on injection
slightly slower onset of anesthesia
sloughing of tissue might be caused by?
topical (normal reaction or from prolonged period)
sensitivity to LA
Metallic Breech loading adv. and disadv.
Adv: visible cartr. one hand aspir., autoclavable, rust resistant, long lasting
DIS: heavier than plastic, may be too big or small for operators, poss of infection w improper care
If the centrals or laterals are not anesthetized...
infiltrate supraperiostally into the muccobuccal fold below the apex of the tooth (27 gauge reccommended)
what enzyme is missing in a pt with methemoglobinemia?
methemoglobin reductase (erythrocyte nucleotide diaphorase)
*when present, it converts iron from ferric form back to ferrous form which can be released into tissues
what is the most common cause of post injection infection?
needle contaimation
*other possible causes=improper handling of equipment and tissue prep.
What area contains the highest percentage of LA in the body?
skeletal muscle (because it makes up the largest mass in the body)
What type of fibers is described by this:-Readily blocked by LA because conduction is continuous not saltatory-therefore critical length is very short
Unmyelinated C fibers (pain, sympathetic postganglionic)
4 sites within the Na+ channel where drugs can alter nerve conduction
1. within channel (tertiary amine LA)
2. outer surface (tetrodotoxin, saxitoxin)
3-4. either activation or inactivation gates (scorpion venom)
The Cartridge aka carpule (which is registered trade name)
1.8 ml solutions (could actually hold 2 ml)
T or F:
Topical anesthetic is less concentrated than injection.
False.. It is more concentrated (5-10% lidocaine compared to 2% lidocaine)
Describe how LA action is dependent upon frequency and voltage of AP
-the higher the frequency of AP firing and the more positive the membrane potential, the GREATER the degree of block by LA(because LAs work by binding to and dissociating from the open state of the Na+ channel)-pain fibers fire at high freq and have prolonged APs, therefore they are preferentially blocked by LAs
recovery from a nerve block (coming off) is slower than onset because...?
the LA is bound to the nerve membrane
norepi does not act on B2 Rc and has a side effect ratio....
9 x higher than epi
Vaz,-Aki. anesthtizes...
(looks same as IANB in picture)
Esters LA
Causes of tachyphylaxis
clot formation
*these four isolate the nerve from contact with LA
*raises Na+ gradient counteracting decrease in Na+ conduction brought on by LA
decreased pH
* brought on by first injection (fewer molecules in RN form on reinjection)
pH of normal tissue
beta Rc response
smooth muscle relaxation
binds fibers together into fasciculi
the thicker the perineurium the slower the rate of LA diffusion
innermost layer of perineurium
main barrier to diffusion into a nerve
greater concentration=
faster diffusion
more rapid onset
Lidocaine for cardio therapy
life support
management of premature ventricular contraction's
Topical Anesthetic
strongly recommended
Benzocaine most common
Lidocaine also used
Ointments and sprays
*Use gauze to dry, apply topical, 1 minute
Cocaine hydrochloride
class: ester
exclusively for topical
rapid acting, lasts long
metabolized: liver (even though it's an ester)
schedule II drug
*abuse potential-not recommended in dentistry
hemoglobinopathies (sickle cell)
cardiac/resp. failure
pts taking acetaminophen or phenacetin
Needle gauge:
blue 30
yellow 27
red 25
Amphipathic means
possessing both lipophilic and hydrophilic parts
pain sensation to usually nonnoxious stimuli
Dental Nerves
Interdental Branches
Interradicular Branches
Enter apical foramen
Innervate gingiva
Innervate PDL
Antibiotic Prophylaxis Recommended for (dental procedures)
perio procedures
endo work
subging. anything
ortho bands (not brackets)
intraligamentary injections
cleaning where bleeding is anticipated
The semi-lunar/gasserian ganglion is housed where?
Meckels Cavity
acts on alpha Rc with some beta
*same as epi, but to lesser degree
diameter of lumen
smaller number = larger diameter
25, 27, 30 most common
• Shelf life:
Plain 3 yr

vasopressor 1.5-2yr
Infiltration anesthesia for minor surgery and dentistry:
Lidocaine, Bupivacaine(dentist//Lip Balm//Lidocaine Bupivacaine)
where do LA's exert their pharmacological actions?
nerve membrane
Action potential
depolarizations from a brief increase in Na permiability
in high concentration of H+ ions (acidic/low pH) most of the solution exists in which form?
which is more of a vasodilator... procaine or lidocaine?
eutectic mixture of LA
cream: 2.5 lido 2.5 prilo
*designed to penetrate intact skin
tube or disc for application
NOT FOR methemoblobinemia pts, allergic to amide pts.
LA have direct action on myocardium, however the CVS is more ______ to the effects of LA than the CNS
the two types of adrenergic Rc are
Prilocaine HCl
*Citanest Forte
class: amide
metabolized: liver & lungs (CO2 major biproduct of prilocaine metabolism)
*methemoglobinemia (reversed with methylene blue IV)
*rapid metabolism (thus less toxic)
*pKa 7.9, onset slower than lido
*part of EMLA (lido-prilo)
*longer acting with NB & shorter with infiltration
*prilo plain NB can get same anesthesia as lido or mepiva
resting plasma epi levels are _______ after one carp of 1:100,000 epi
no longer available in US
cant be imported
no longer available in US
Lidocaine Topical
two forms
lido base-use on ulcerated, abraded, or lacerated tissue & lido hydrochloride-penetrates better, but toxicity is higher
High LA blood levels can induce...?
toxic reactions
tetanic spasm of jaw
normal opening of mouth restricted
induction time
period from deposition to complete conduction blockade
centbucridine (a quinoline derivative) is 5-8 times as potnent as lido .. It is special because it does not affect the _____ or ______ adversely except in very high doses.
when drug passes through tissue that tends to restrict free molecular moverment
Trismus is...
prolonged tentanic spasm of jaw muscles by which opening of mand. is restricted
Gives slight soreness when opening the mandible
Palatal Anesthesia
traumatic for many
use pressure at site before & during
deposit SLOWLY
recommended 27 gauge
believe it can be painless
Lingual nerve innervates what?
anterior 2/3 of tongue
Ratio solution of vasopressor
1:100,000 = 10 mcg/mL
Paresthesia is one of the most frequent causes of ...
malpractice litigation
Is the trigeminal nerve a sensory or motor nerve?
What nerves are anesthetized with an IA
Inferior Alveolar
what for tx of trismus?
heat therapy
warm saline rinse
muscle relaxant
physiotherapy (open & close & lateral excursions)
chewing gum
Major factor influencing ability to aspirate?
gauge of needle
Duration of Action:
2. Articaine
4. Prilocaine
2. intermediate
3. plain it's short, c epi it's intermediate
4. plain it's short, c epi it's intermediate
5. plain it's short, c eip it's intermediate
alpha Rc response
smooth muscle contraction in blood vessels
Which tissues seems to be more sensitive to LA than other tissues?
skeletal muscle
hydrochloride or LA salt is both __________ & _________. It exists as ___________ molecules and ___________ molecules.
water soluble
poitively charged molecules
Sensory nuerons (afferent) have three major portions--(traditional nueron). They are...
cell body
dendritic zone
Rationale for Addition of vasoconstrictions:
o Primary rationale:
 Incr duration of effect –Alpha1 stim–arteriolar constriction–decr redistribution
o Secondary rationale:
 Reduce systemic toxicity – reduced uptake – safer
 Reduced bleeding at operative site if local infiltration, not NB given
Two components of needle
diameter of lumen (gauge)
length of shaft
Maxillary nerve block
is not a PSA
anesthetizes all but buccal ging of molars in one quad!
Care of Cartridges
stored at room temp in original container
not be permitted to soak in sterilizing solutions (can leak in & contaminate)
warmers not needed
no sunlight
what is the PRIMARY effect of LA on blood pressure?
which branch of V3 exits the mental foramen?
mental nerve
Dyclonin HCl
good for pts with allergy to other LA
potent like cocaine
slow onset (up to 10 minutes)
low toxicity because of poor H2O solubility
elimination half-life is...
time necessary for 50% reduction in blood level
Which is injected higher? IA or Gow Gates?
Gow Gates
What intraoral injection has the highest rate of aspiration?
IA 10-15% positive aspiration
is there ever a time that 100% of nerve fibers are blocked?
What nerves are anesthtized by the Gow Gates Block?
inferior alveolar
• Henderson Hasselbach:
pKa = pH + log [+] / [-]
Rate of absorption of LA is often reduced by coadministration of
vasoconstrictoreg epinephrine, phenylephrine (alpha 1 agonists)* CANNOT use on places w end arteries eg fingers toes or penis ==> gangrene
eleveated blood levels of LA may result from ...
slow bitransformation
slow elimination from body
too large total dose
rapid absorption into blood stream
inadvertant IV administration occurs
to increase safety one should always use the...
smallest clinically effective dose
difference between allergy and overdose
allergy is exaggerated response of immune system (symptoms the same in every allergy)
overdose is exaggerated response of clinical action of drug (symptoms depend on the drug you took)
relative contraindication implies that
drug may be used after carefully weighing risk and benefit if better alternative isn't available
*smallest clinically effective dose should be used and there is an increase of adverse reaction
Care of needles
never use on more than one pt
change needle after 3-4 pentrations
cover with protector when not in use
always be aware of uncovered needle
Mylohyoid enters which canal through which foramen?
mandibular canal through mandibular foramen (to reach the mylohyoid muscle)
if you go too deep on a PSA it increases risk of what?
what causes trismus?
trauma to muscles or blood vessels in the infratemporal fossa
LA which alcohol or cold sterile has diffused
low grade infection
multiple needle penetrations
succinylcholine produces apnea for a brief time with ventilation returning when...
succinylcholine is hydrolyzed by plasma cholinesterase
*when atypical psc is present, apnea is prolonged
Epidural anesthesia eg during delivery/labor-action on spinal nerve roots
Epidural cannula allows a variety of LAs to be used
MSA innervates which teeth?
Pre-molars & the MB root of the 1st molars
Which is larges and strongest bone in face?
Mandible--cortical bone & dense
what is the most common antioxidant/preservative?
sodium bisulfite (this acidifies the solution)
Incisive Nerve Block points of interest...
terminal branch of IA anteriors
pulpal and buccal soft tissue of premolars to midline
NO lingual (more comfy)
25 gauge short
just anterior to mental foramen
should slightly balloon
maintain pressure over site to push solution into mental foramen
hematoma risk at injection site
the preconvulsant stage of LA blood levels are produced because ...
depression of inhibitory neurons
*(the reason symptoms are excitatory is because depression of inhibitory impulse leaves the facilitatory(excitatory) free and uninhibited)
why are LA containing a vasopressor acidified?
to retard oxidation of the vasoconstrictor
which increases period of effectiveness
What are warning signs of possible toxic blood anesthetic levels
excitation or sedation 5-10 minutes arter administration of LA
what are pathognuemonic signs of methemoglobinemia?
cyanosis that doesn't respond to O2 &
brown arterial blood
PDL points of interest...
aka intraligamentary (ILI)
and peridental (original)
good to sub for failed blocks
with use of supraperiosteal injections in maxilla, PDL is not used as much
Good for kids because there is little to no soft tissue anesthesia
Causes slight damage to tissues in region of injection ONLY
Safe to periodontium
There is no need for speical PDL injectors
Not good for primary teeth when perm. tooth bud is present
27 gauge short
bevel toward the root
keep needle against tooth, go slowly, give only .2ml, and don't inject to to highly inflammed tissues
which appears more in urine?
amides or esters?
amides (because ester is mostly metabolized in the plasma)
what makes a solution c epi more acidic?
sodium (meta) bisulfite --the preservative
LA effects on CVS:
nonoverdose levels
at the very beginning there is a slight increase or no change in blood pressure
LA blood levels > theraputic level =
further decrease in contraction & output which lead to circulatory collapse
Pain is blocked more readily than other modalities in a mixed nerve because:
1) critical length is short2) pain fibers fire APs at rel high freq3) pain fibers have rel broad APs
Felypressin recommended for ASA III and IV CVD risk patients because...
it has minimum CV stimulation and is non-dysrhythmogenic
is 1:100,000 as effective for hemostasis as 1:50,000?
for pain control it is great, but hemostasis is greater in a 1:50,000 concentration
what is a theraputic use of LA on the CVS?
and which of the LA's are most useful in humans?
treating hyperexcitable
procaine & lidocaine
1.8 to 6 ug/ml
With the IANB and Gow-Gates, should you contact bone?
YES- Do not deposit until bone is contacted!
Where does a hematoma from a Long buccal/ buccal nerve block occur?
at injection site
blood may pool in vestibule
For the 3 injection technique what sites and in what order are the injections administered?
.3 ml to the labial frenum
.3 ml to labial aspect of papilla between max. central incisors
.3 ml to lateral to incisive papilla (if needed. Often the first two will provide adequate anesthesia)
What is the pre med for those who can't take oral medicine?
2grams IV or IM within 30 minutes of procedure
If you give an IA, what areas are anesthetized?
all pulpul for one mand. quad, and all soft tissue except for the buccal of the molars
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