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88 Cards in this Set
- Front
- Back
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all LA molecules are composed of three components
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aromatic ring
intermediate chain terminal aminie (N containing) |
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aromatic ring
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provides LIPOPHILIC properties (lipid solubility)
will help get into nerve mem. more than getting into tissue |
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intermediate chain
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determines if the anesthetic is an ester or an amide
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terminal amine
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provides HYDROPHILIC properties (water solubility)
get into pulp tissue well |
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aromatic ring char.
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improves lipid sol.
helps LA penetrate into nerve mem. determines the potency of drug! |
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intermediate chain char.
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(linkage)
provides spatial separation between the lipophilic and hydrophylic ends of the LA molecule classifies drug as either an ester or an amide!! |
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terminal amine char
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hydrophilic end
ensures drug will diffuse into soft tissues |
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two main chemical classifications
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ester and amide
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ester anesthetics
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allergenicity- it is metabolized to PABA which a lot are allergic to
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procaine (ester)
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not used anymore
poor diffusion properties, poor efficacy, slow acting and short duration not available in dental cart. but medical vials available, used if ct is allergic to all amides (never has happened) |
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ALL injectable LA used in dentistry are amides
5 generic groups of amides |
lidocaine
articaine mepivacaine bupivacaine prilocaine LAMBP epi will add longer duration |
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amides LA
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virtually non-allergenic
excellent diffusion into tissues/onset times |
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LA must block Na channels over..
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3-4 nodes to get profound block anesthesia
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la sol. has an equilibrium of molecules:
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25% uncharged/unionized molecules called anions or BASE molecules (lipid soluble)
75% charged/ionized molecules called cations (water soluble) = ACID (molecule has hydrogen ion) |
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healthy tissue pH
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7.4 (basic)
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acid LA enters tissue..
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the tissue pH will change the LA equilibrium; more base molecules are produced (H ion dissociates from the acid molecules)
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base molecules are..
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lipophilic- they can penetrate the nerve membrane
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the more base molecules there are, the better..
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diffusion through nerve membrane
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the proportion of base and cation molecules in anesthetic solution is determined by
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ph of the local anesthetic
ph of the tissues pka of the LA |
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if local anesthetic is less acidic (plain), onset is
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faster
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if local anesthetic is more acidic, onset is
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slower
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all anesthetics with a vasoconstrictor have a
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lower pH (~3.3)
because of sodium bisulfite, it needs acidic environ |
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healthy tissue pH
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7.4
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inflamed tissue pH
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3-6 (more acidic)
infected tissues have lower pH |
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what will dilated BV's and edema do to LA?
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increased blood flow will carry anesthetic away decreasing duration
edema will dilute the solution |
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pKa represents...
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the proportion of base molecules to cation molecules in the solution when made
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a lower pKa =
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more base molecules and faster onset
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a higher pKa =
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fewer base molecules and slower onset
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pKa 7.7
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2-4 min onset
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pKa 8.1
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5-8 min onset
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T or F
lidocaine has the slowest onset |
T
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lipid solubility determines
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potency
if LA has high lipid sol. then it can diffuse thru membrane quicker, making it more potent |
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T or F
prilocaine is the most lipid soluble |
F
Bupivacaine is |
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If LA has a high degree of PROTEIN BINDING then the LA will
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bind to receptor sites for longer time, increasing duration
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pulpal anesthesia
short acting |
10-30 min
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intermediate acting
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60min
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long acting
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90min+
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absorption/distribution of LA depend on
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vasodilating properties of sol.
presence of epi (vasoconstrictor) |
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all amide LA are peripheral..
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vasodilators
we don't want this |
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articaine, bupivacaine and lidocaine are...
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potent vasodilators
you MUST add epi to prevent rapid uptake of drug |
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prilocaine and mepivacaine are..
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weak vasodilators
they MAY be used without adding a vasoconstrictors |
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distribution of LA
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LAs are distributed to all tissues in the body
highly vascular organs have higher conc. CROSSES THE PLACENTA |
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biotransformation (metabolism)
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reduces toxicity by eliminating drug
most are metabolized either in the blood or liver liver metabolism is slower than metabolism in the blood |
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bupivacaine, lidocaine and mepivacaine are metabolized by..
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liver enzymes
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prilocaine is metabolized in the..
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lungs & kidneys first, then in the liver
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articaine: only 5-10% is metabolized in the liver, most is metabolized by..
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blood plasma esterases
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benzocaine, procaine and tetracaine are metabolized in blood plasma by enzyme:
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pseudocholinersterase
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T or F
benzocaine and tetracaine are used in topicals only |
T
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Lidocaines half-life is
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~90 min
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T or F
Articaine has long half-life |
F
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both esters and amides are eliminated through the..
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kidneys
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supreperiosteal injection aka local infiltration injection is
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an injection that anesthetizes a small area, 1 or 2 teeth and associated structures, it's near terminal nerve endings
field block? |
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dental plexus
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small terminal nerve endings of the psa, msa, and asa
innervates pulps of the teeth and buccal/facial periodontium (not the linguals) |
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mandible has dense cortical bone except in the..
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mandibular incisors
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this injection is often used for soft tissue anesthesia and especiallg good when
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hemostasis is needed
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depth & angle for insertion of max supraperiosteal injection
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3-5mm
20 degrees with bevel facing bone (red dot should be opposite big window) |
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type of needle and amount deposited
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25 or 27 gauge, short
0.6mL to 0.9mL (1/3 of cart.) amount deposited will depend on tooth, procedure, ct size and density of bone |
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rate of deposition
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20-30sec
expect anesthesia in 3-5min |
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T or F
rare positive aspirations |
T
less than 1% |
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max central incisors can be hard to anesthetize because of the ANS so you should
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insert slightly distal to the long axis of the tooth
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cross-over innervation in central incisors
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when nerve fibers from one central goes to the other central, so both get numb
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complications with max first molar injection
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injecting directly over roots can be ineffective because of the dense zygomatic process
so give two injections, one over apex of 2nd pm, and second over buccal roots of the 2nd molar |
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LA vasoconstrictors
vasodilation will |
increase the rate of systemic absorption of the drug; increases blood levels of LA
decrease the drug's effectiveness, short duration increase bleeding at site |
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all local anesthetics cause
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vasodilation
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adding a vasoconstrictor to a local anesthetic will
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counteract the vasodilation activity of LA
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vasoconstrictor's beneficial effects
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decrease blood flow in area, producing profound effects
slows absorption of LA into CVS, reducing systemic toxicity |
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degree of vasodilation varies w/the LA drug
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lidocaine & articaine have significant vasodilation
prilocaine & mepivacaine have little (they don't require vasoconstrictor) |
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T or F
epi and levo are sympathomimetic |
T
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vasoconstrictors mech. of action
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activates adrenergic receptors found in most tissues
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two major groups of adrenergic receptors
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alpha and beta(w/subtype)
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alpha receptor activation causes vasoconstriction of the
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smooth muscle walls of BVs
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two types of beta receptors
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B1- found in heart
B2- found in bronchi in lungs |
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T of F
you cannot be allergic to epi |
T
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levonordefrin (Neo-Cobefrin)
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an alternative agent used only with 2% mepivacaine
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not as potent as epi and is used in 1:20,000 concen. to produce similar effects as
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1:100,000 epi
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when someone cannot tolerate the use of epi use..
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2% mepivcaine
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hyperresponsive reaction s&s to epi go away within
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5-10min because half-life of epi is 1-3min
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don't give epi or levo if
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uncontrolled type 1 diabetes
daily unstable angina recent MI or CVA within 6mo uncontrolled hypertension uncontrolled arrhythmias coronary bypass surgery within past 6mo recent cocaine use sulfite allergy (shellfish, red wines)!!! common in pts with steroid dependent asthma give plain anesthesia! all are ASA IV |
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use cardiac dose(0.04) of epi/levo with
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controlled diabetes
cardiovascular disease controlled hypertension hyperthyroidism glaucoma cocaine abuser |
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if ct is ASA III due to cardiovascular problems, epi is..
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INDICATED for better pain control. use cardiac dose and 1:50,000 should not be used
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if ct has bp readings that are asa II treat as
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healthy patient
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use cardiac dose of epi if pt is taking
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tricyclic antidep. - elavil, sinequan
nonselective beta blockers- inderal, corgard MAOIs- nardil Phenothiazides- thorazine |
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all antidepressants are red flags for epi use except..
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SSRI's
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epi is metabolized by the...
and excreted by the... |
liver, kidneys
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most commonly used concentration of epi
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1:100,000
0.01mg/mL |
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most diluted conc. of epi
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1:200,000
good for cardiac cts, (articaine) 0.005mg/mL |
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MRD of epi for normal ct
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0.2mg
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limiting factor
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the drug that limits the total amount of LA administered
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