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ANESTHESIA

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afferent neurons
sensory neurons
myelin
insulating lipoprotein neural membrane layer
nodes of ranvier
regularly spaced intervals along axon with constricted myelin sheath causing exposure of nerve membrane to extracellular environment
site of local anesthetic action on myelinated nerves
NERVE MEMBRANE @ nodes of ranvier
saltatory conduction
constant strength impulse that leaps from node to node FAST
--nerve impulses can skip several nodes therefore we must anesthetize a complete block up to 8-10mm to ensure pain control
resting potential
negative charge in nerve due to K+, positive extracell tissues due to Na+
depolarization
Na+ moves into nerve cell = cell becomes less negative
firing threshold
once Na+ completely moves into nerve cell and reaches the appropriate electrical magnitude in which an AP impulse can be initiated
repolarization
nerve pumps Na+ out of nerve cell to get back to resting state
local anesthetic
1. diffuses to NERVE MEMBRANE
2. displaces Ca+ ions from binding to Na+ channel receptor site
3. binds to Na+ channel receptor site
4. blocks Na+ channel from opening = NO Na+ move in
5. BLOCKS DEPOLARIZATION = no impulse propagation
base
local anesthetic molecule that is UNCHARGED = allows anesthesia to DIFFUSE through the tissues/nerve membrane and into the Na+ channel
cation
local anesthetic molecule that is CHARGED = allows BINDING of anesthesia to specific Na+ channel receptor site to block the channel from opening
base & cation factors
exist simultaneously within local anesthetic at different proportions according to:
--pH of solution
--pH of surrounding tissues
--pKa of anesthetic
pKa (dissociation constant)
affects ONSET of anesthetic
low pKa
FAST onset of local anesthetic (MORE base present)
high pKa
SLOW onset of local anesthetic (LESS base present)
lipid solubility
affects POTENCY of anesthetic
--more soluble = more effective at lower conc.
protein binding
affects DURATION of anesthetic
--better binding to receptors = longer duration of action
vasoactivity
affects POTENCY & DURATION
low/acidic pH of extracellular tissues
SLOWS onset of anesthetic

increased cation: base ratio→ less molecules intracellular→ fewer cations can bind

inflammation
--redness = dilated vessels = faster absorption into blood
--inject farther away from infected areas or treat infection with antibiotics before

vasoconstrictors
--sodium bisulfate preservative is acidic = tissues take time to buffer back to normal pH
--can burn upon injection
--pH with = 3..3, without = 5.5
perineurium nerve covering
GREATEST barrier to local anesthetic penetration
2 types of local anesthetic
esters & amides
esters
TOPICAL anesthetics (benzocaine)

hydrolyzed in the PLASMA by PSEUDOCHOLINESTERASE ENZYME = short acting, some people can't break it down if they have atypical enzyme

by-product = PABA = source of allergic rxns
Amides
CARTRIDGE anesthetics

metabolized in the LIVER by hepatic microsomal enzymes = longer acting
--liver damage pts = longer acting anesthetic

by-product of prilocaine= ortholuidine = can cause methemoglobinemia (rare)
5 cartridge anesthetics used in US (amides)
Articaine/Septocaine
Bupivicaine/Marcaine
Prilocaine/Citanest
Mepivicaine/Carbocaine
Lidocaine/Xylocaine
max dose of Bupivicaine/Marcaine
0.6mg/lb = 90 mg max
max dose of Mepivicaine/Carbocaine
3mg/lb = 400mg max
max dose of Lidocaine/Xylocaine
2mg/lb for pedo
3.2mg/lb for adult
500mg max
max dose of Articaine/Septocaine
3.2mg/lb
max dose of Prilocaine/Citanest
4mg/lb = 600mg max
significant renal disease
relative contraindication for local anesthetics --> reduce dose

see patient 1 day after dialysis because there metabolites & chemicals will be at optimal levels so they can handle anesthesia best
local anesthetics are CNS, CVS and respiratory ____________
depressants
--but can cause convulsions (excitation) at high/overdose levels
--take caution if patients are taking other CNS depressants like opioids, anti-anxiety or phenothiazine drugs = potentiate CNS effect
CNS depressant drugs
opioids-codeine, demerol, percodan
anti-anxiety-valium, librium
phenothiazines- thiazine
___________ induce the production of hepatic microsomal enzymes = increase the rate of local anesthetic (amide) metabolism
barbiturates
vasodilation via local anesthetic
increases rate of absorption = increases anesthetic blood level = increases potential for overdose & decreases duration of pain control
--this is why we ADD vasoconstrictors to local anesthetic
ALL local anesthetics are VASODILATORS, except ________ which is a vasoconstrictor.
cocaine (ester)
vasoconstrictors/vasodepressors
adrenergic

--decrease blood flow to injection site
--slows absorption of anesthetic into the CVS = lowers anesthetic blood level --lower risk of toxicity/OD
--longer duration of pain control (6-10x)
--hemostasis

should be included in ALL anesthetics unless there is a contraindication (medical hx or short procedure/pedo)
vasoconstrictors used in injectable anesthetic
Epinephrine (Adrenaline) & Levonodefrin (Neo-Cobefrin)

= catecholamines
does concentration of vasoconstrictor affect the duration of pain control
no
alpha receptors
stimulation causes peripheral vasoconstriction

site of action for Levonordefrin
beta receptors
stimulation of B1 causes bronchodilation (increase oxygen), vasodilation of coronary arteries and stimulation of B2 causes increased HR/contraction
--fight or flight

site of action for EPI
hemostasis
must deposit vasoconstrictor in local area where bleeding is to be effective
Levonodefrin
15% as potent as epi = use higher concentration (1:20,000) to have same effect

max dosage = 1mg
vasoconstrictor overdose
throbbing headache, palpitations, tremor

NOT an allergic reaction, probably due to IV injection
vasoconstrictor absolute contraindication
sodium bisulfate allergy (preservative) -- ANY sulfite allergy
Levonodefrin absolute contraindication
tricyclic anti-depressants
max dosage of EPI
0.2mg/200mcg for HEALTHY patient

0.04mg/40mcg for CARDIAC patient (2 cartridges max)
how much epi is in 1 cartridge of anesthesia
0.018mg
epi concentrations
1:50,000 or 1:200,000
Epi is added to which anesthetic ?
Lidocaine, Artisane, Bupivicaine, Mepivicaine & Prilocaine
Levenodefrin is added to which anesthetic?
Mepivicaine/Carbocaine ONLY
which medical condition requires you to REDUCE the amount of vasoconstrictor used
hyperthyroidism = more sensitive to catecholamines & more exaggerated response to vasoconstrictors
(relative contraindication)
use of local anesthetic on patient with significant CV disease
limit treatment & REDUCE anesthetic dose
(relative contraindication)
local anesthetic absolute contraindication
allergy
non-selective beta blockers + local
relative contraindication
--"olol" drugs EXCEPT cardio selective beta blockers (MAABBE: metropolis, atenolol, acebutolol, bispoprolol, beteaxolol, esmolol)
factors influencing duration of anesthetic/pain control
--Individual response (normal, hyper, hypo)
--accuracy of deposition
--tissue status (pH, vascularity)
--anatomical variations
--technique (nerve block vs infiltration)
when do you pre-medicate
artificial heart valve
unrepaired heart defect
previous endocarditis
sickle cell anemia
moore's rating 1
probably occurrence of a MAJOR reaction to anesthesia
-- + vasoconstrictor
--+ opioids
--+ cocaine
-- using different anesthetics together
--non-selective beta blockers + vasoconstrictors
--tricyclic antidepressants + vasoconstrictors
moose's rating 5
unlikely occurrence of a minor reaction
needle length
short = 20mm
long = 32 mm
needle recapping methods
needle guards
scoop technique (1 hand)
25 gauge needle
RED (largest internal diameter barrel)
27 gauge needle
YELLOW
30 gauge needle
BLUE (smallest internal diameter barrel)

MOST likely to break
hub
weakest point in the needle = DONT insert all the way to this or it can break (unless absolutely necessary)
how often should you change the needle out for single use
after 3 injections
preventing needle breakage
NEVER pre-bend a needle
NEVER redirect needle if deeply embedded in tissue

have hemostat ready to go in case of breakage
cartridge parts
glass cylinder
stopper
cap
diaphragm
needle parts
syringe parts
contents in anesthetic cartrdige
local anesthetic

vasoconstrictor + preservative

sodium chloride (tissue isotonic)

distilled water (volume)
dialogue history
To obtain as much information as possible

Assess degree of risk of patient

Determine any treatment modification
pre-op BP
To establish baseline bp in event of medical emergency

Screen out patient on which dental procedures might constitute a greater risk

Refer those patients with an abnormal reading for medical exam
CN V
trigeminal nerve

3 branches: V1, V2, V3
CN V1
ophthalmic nerve
sensory only
CN V2
maxillary nerve
sensory only
exits via foramen rotundum
over pterygopalatine fossa
out IO foramen

branches
--orbital
--nasal
--palatine = NP, GP
--PSA
--MSA (branches in IO canal)
--ASA (branches in IO canal)
CN V3
mandibular nerve
sensory & MOTOR
exits foramen ovale

branches
--ant: long buccal
--post: lingual (sensory ant 2/3), inferior alveolar
branches in pterygopalatine fossa
V2: nasal, palatine & PSA branches
anesthesia to the ____________ nerve can be caused by penetrating TOO DEEP during inferior alveolar nerve block = patient CANT close eyes
facial
normal pH 7.4 -- what is the cation: base ratio?
3:1
calculating max dose/cartridges
1.8 mL fluid in a cartridge
5% bupivacaine = 5mg/mL
bupivicaine max recommended dose is 90 mg

1.8 x 5 = 9mg

90/9 = 10 cartridges MAX
during PSA injections, a ________ can occur if you nick the vessel due to going too deep = use short needle
hematoma
what should you do if you have a positive aspiration
back up a little and reaspirate, don't inject if still getting positive aspiration (in blood vessel)