Term
What type of cells are voltage-gated sodium channels found in? |
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Definition
excitable cells - neurons, myocytes, cardiac cells |
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Term
What type of channel is essential for AP generation? |
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Definition
voltage-gated sodium channels |
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Term
Name two things that block voltage-gated sodium channels. |
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Definition
1) neurotoxins 2)local anesthetics |
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Term
sensation, emotion, thought, and movement all depend on _________ channels. |
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Definition
voltage-gated sodium channels |
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Term
What acts as the inactivation h-gate for voltage-gated sodium channels? |
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Definition
linker peptide between hexamers III and IV of the alpha subunit |
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Term
what forms the voltage-sensing m-gate for voltage-gated sodium channels? |
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Definition
S4 segment of each hexamer in the alpha subunit |
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Term
How many hexamers make up the alpha subunit of the v-gated sodium channel? |
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Definition
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Term
Where do local anesthetics bind to the v-gated sodium channel? |
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Definition
in the carboxy terminus - between F1764 and Y1771 ALWAYS ACT ON HEXAMER IV AT S6 TRANSMEMBRANE SEGMENT OF THE ALPHA SUBUNIT |
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Term
sodium channels disorders in the brain can cause what two problems? |
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Definition
1) epilepsy.febrile seizures 2) myoclonic seizures |
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Term
primary erythermalgia can be caused by a disorder of ________ channels in peripheral nerves? |
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Definition
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Term
what is the mechinism of tetrodotoxin and saxitonin? |
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Definition
pore-occlusion of v-gated sodium channels |
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Term
How do brevetoxins (from red tide) work? |
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Definition
persistent activation of v-gated sodium channels |
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Term
When v-gated sodium channels are in the resting state, the m-gate is _______ and the h-gate is _______. |
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Definition
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Term
When v-gated sodium channels are in the activated state, the m-gate is _______ and the h-gate is _______. |
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Definition
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Term
When v-gated sodium channels are in the inactivated state, the m-gate is _______ and the h-gate is _______. |
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Definition
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Term
The _____ you use the v-gated sodium channels, the _______ the percentage of blocked channels in the presence of a local anesthetic/channel blocker. |
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Definition
more, greater
= "use-dependent block" |
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Term
What are the two theories for use-dependent block of local anesthetics? |
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Definition
1)Guarded receptor theory 2)Modulated receptor theory |
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Term
The guarded receptor theory proposes that the use-dependent block of local anesthetics is due to a change in ________ |
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Definition
drug accessibility to receptor |
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Term
The modulated receptor theory states that use dependent block of v-gated sodium channels is due to a change in ________ |
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Definition
receptor AFFINITY for the drug |
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Term
where are v-gated sodium channels found on nerves? |
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Definition
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Term
In order for local anesthetics to work, they must block ___________ |
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Definition
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Term
What are the two main types of pain fibers? |
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Definition
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Term
What are C fibers responsible for carrying? (4) |
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Definition
1)SLOW pain 2)temp 3)mechanoreception 4)reflex responses |
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Term
What are Adelta fibers responsible for carrying? (3) |
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Definition
1)FAST pain 2)cold temp 3)touch |
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Term
Where do C fibers synapse? |
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Definition
substantia gelatinosa of the dorsal horn |
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Term
Where do Adelta fibers synpase? |
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Definition
rexed lamina I and dorsal horn |
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Term
Thicker fibers have ________ internodal distance than thin fibers. |
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Definition
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Term
What fibers are first blocked by local anesthetics and why? |
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Definition
B fibers because they are the thinnest |
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Term
what effect results from anesthetic action on B fibers? |
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Definition
vasodilation with associated hypotension (decrease in BP) ** OCCURS BEFORE PAIN BLOCKING TAKES EFFECT! |
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Term
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Definition
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Term
what is respionsible for the cardiotoxicity of local anesthetics? |
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Definition
the effect on potassium channels in the myocardium |
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Term
What channels do lidocaine and bupivacaine bind? |
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Definition
1)sodium 2)potassium 3)calcium
bind with lower affinity to K and Ca channels |
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Term
Name two drugs that increase the effect of bupivacaine. |
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Definition
nifedipine and nicardipine (L-type VGCC blockers) |
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Term
what is responsible for the de-esterification of local anesthetics with an ester link? |
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Definition
plasma pseudocholinesterases |
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Term
Name four local anesthetics that are esters. |
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Definition
procaine tetracaine benzocaine cocaine |
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Term
what kind of link is found in procaine and tetracaine HCl? |
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Definition
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Term
what type of link is found in lidocaine and bupivacaine? |
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Definition
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Term
how are local anesthetics with amide links inactivated? |
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Definition
hydrolysis in hepatocytes by mixed function oxidase |
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Term
ester local anesthetics are ______ acting and amide local anesthetics are _______ acting. |
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Definition
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Term
lidocaine, mepivacaine, bupivacaine, ropivacaine, and prilocaine are ______ local anesthetics |
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Definition
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Term
what does cocaine inhibit? |
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Definition
reuptake of catecholamines |
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Term
Cocaine enhances the action of ________ |
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Definition
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Term
What is the ONLY local anesthetic that produces VASOCONSTRICTION? |
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Definition
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Term
what is the potency of procaine? |
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Definition
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Term
what is the potency of tetracaine? |
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Definition
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Term
procaine interacts with what type of drugs? |
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Definition
antibacterial - sulfonamides |
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Term
what metabolic product of procaine is responsible for the inhibition of sulfonamides? |
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Definition
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Term
What should be given with tetracaine in a spinal block and why? |
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Definition
10% dextrose - to increase the specific gravity |
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Term
Why do you need to incease the specific gravity when gicing tetracine in a spinal block? |
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Definition
To prevent the drug from traveling to the brain where it would block respiration
*need to tilt patients bed upright to prevent travel to brain |
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Term
what two ester anesthetics are for topical use only? |
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Definition
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Term
What can cocaine be used for? |
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Definition
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Term
what two amide anesthetics are long-acting and very potent so used for surgery? |
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Definition
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Term
what amide anesthetics are used topically? |
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Definition
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Term
what amide anesthetic is used for an epidural in labor? |
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Definition
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Term
what are the modes of administration for procaine? |
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Definition
nerve block infiltration spinal |
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Term
what does it mean if a drug is administered by infiltration? |
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Definition
it is injected into tissue but no specific nerve is targeted |
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Term
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Definition
inject drug into tissue while targeting a specific area * usually only done in lower body |
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Term
Where are nerve blocks given? |
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Definition
lower body *try to avoid upper body because of important structures such as the diaphragm (would paralyze breathing) |
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Term
Where are drugs injected when administered via epidural? |
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Definition
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Term
In what mode of local anesthetic administration does the drug remain localized? |
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Definition
epidural administration - remains in the DRG allowing for lower dosing |
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Term
Where are drugs injected in a spinal block? |
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Definition
into the CSF surrounding the spinal cord |
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Term
What do you have to worry about if topical or infiltrative anesthetics are applied in high concentration over large areas? |
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Definition
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Term
What are topical anesthetics ineffective on? |
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Definition
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Term
What is Lidocaine used topically for? |
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Definition
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Term
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Definition
eutectic mixture of local anesthetics lidocaine +prilocaine for venepuncture |
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Term
What three local anesthetics can be injected into tissue around incision for minor operation (via infiltration)? |
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Definition
lidocaine procaine (short-acting) bupivacaine (long-acting) |
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Term
what is given in addition to local anesthetics (lidocaine/procaine/bupivacaine) in order to offset their effect of vasodilation? |
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Definition
epinephrine - vasoconstriction |
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Term
Where should epinephrine not be used with local anesthetics for minor surgery and why? |
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Definition
fingers, toes, ears, nose, penis *they are end-artery supplied so EPI could cause gangrene |
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Term
Would could be a side effect of administering lidocaine + EPI via infiltration for finger surgery? |
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Definition
gangrene/ necrosis coould occur - SHOULD NOT USE EPI |
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Term
When using IV regional anesthesia, how long should you wait before releasing the pressure cuff and why? |
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Definition
20 min - to prevent systemic toxicity |
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Term
Intravenous regional anesthesia is used for ______ surgery? |
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Definition
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Term
In IV regional anesthesia, the drug should be injected ______ to pressure cuff |
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Definition
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Term
Why is the injected IV distal to the pressure cuff in IV regional anesthesia |
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Definition
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Term
what two drugs can be used in IV regional anesthesia? |
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Definition
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Term
what are the adverse effects of a nerve block? |
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Definition
1)onset of anesthesia is slower 2)need high accuracy of injection |
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Term
what is a good mode of anesthesia administration for an episiotomy? |
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Definition
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Term
nerve block are good for what type of procedures? |
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Definition
surgical and dental - injected near specific peripheral nerves |
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Term
what are spinal blocks used for? |
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Definition
surgery of abdomen, pelvis, leg obstetrics |
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Term
what two drugs are used for spinal blocks? |
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Definition
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Term
drugs given in a spinal block act on ______ and _______ |
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Definition
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Term
When giving a spinal block of tetracaine or lidocaine, how do you minimize cranial spread? |
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Definition
elevate head and use 10% dextrose to make it heavier that CSF |
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Term
What are the adverse effects of a spinal block? |
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Definition
1)bradycardia.hypotension - symp. block 2)respiratory depression - phrenic n. or resp center block 3)urinary retention - pelvic parasymp. block |
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Term
drugs injected into peridurral space act on _______ and _______ |
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Definition
nerve roots and spinal roots |
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Term
what two drugs can be administered via epidural? |
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Definition
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Term
what can epidural administration of local anesthetics be used for? |
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Definition
surgery of abdomen, pelvis, leg obstetrics (painless birth)
*same as spinal block |
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Term
why are adverse effects lees likely with epidural than with spinal? |
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Definition
because cranial spread is limited in epidural - drug stays in DRG
*still see urinary retention with epidural |
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Term
what are the adverse effects common to all local anesthetics? |
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Definition
1)resp depression, coma, death 2)decreased myocardial excitability, conduction rate, contraction force 3)profound hypotension (due to vasodilation) |
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Term
neurotxocity occurs at _______ doses than cardiotoxicity when using local anesthetics. |
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Definition
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Term
What is the CC:CNS ratio? |
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Definition
used for local anesthetics to describe the dose causing cardiovascular collapse/dose causing CNS collapse |
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Term
If a local anesthetic has a CC:CNS ratio of 10 and it causes seizures at 5 mg/kg than at what dose with it cause cardiac arrest? |
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Definition
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Term
The first sign of local anesthetic neurotoxicity is _________ |
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Definition
excessive talkativeness or total silence |
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Term
what are the signs seen in neurotoxicity? |
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Definition
change in thought processes perioral parasthesias whole body flushing feeling tinnitus generalized seizures |
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Term
what part of the limbic system is involved with convulsions seen in neurotoxicity of local anesthetics? |
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Definition
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Term
coma, resp and cardiac arrest are found in what phase of neurotoxicity? |
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Definition
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Term
what is seen in the excitation phase or neurotoxicity? |
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Definition
tinnitus numbness nystagmus dizziness restlessness tremor convulsions |
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Term
what is important to do while administering local anesthesia? |
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Definition
keep the patient talking!! |
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Term
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Definition
constant flow of words - may or may not make sense *can be the 1st sign of local anesthetic neurotoxicity |
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Term
what are the effects of cardiotoxicity due to local anesthetics? |
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Definition
hypotension decreased myocardial contractility bradycardia w/ long PR interval widened QRS increased Q-T dysrhytmias |
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Term
how do local anesthetics cause decreased myocardial contractility? |
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Definition
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Term
cardiotxocity of local anesthetics involves a ____________ in refractory perios,firing threshold, and conduction time |
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Definition
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Term
what is the hematologic side effect of prilocaine, lidocaine, and benzocaine? |
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Definition
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Term
what metabolite of prilocaine is resonpsible for the oxidation of Hb to MetHb? |
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Definition
O-toluidine - liver metabolite of prilocaine |
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Term
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Definition
liver metabolite of prilocaine - oxidizes Hb |
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Term
what are the efefcts of MetHb? |
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Definition
*cyanosis dyspnea dizziness/syncope gray cutaneous discoloration tachypnea fatigue weakness exercise intolerance |
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