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