local anesthetics

Question 1

what happens with local anesthetics?

Answer 1

inhibit nerve conduction by blocking Na+ channel

Question 2

how many functional amines and what are they

Answer 2

lipophilic group
tertiary amine
intermediate chain connecting the two

Question 3

what was the first local anesthetic?

Answer 3

cocaine- causes vasoconstriction

Question 4

pharmacokinetics of local anesthetics

Answer 4

pKa is 8-9
pH(7) is < pKa so it will be charged
need a transporter
hendersen haslbach figures percentage of D vs DH

drug is in cell binds to Na and inhibits it which inhibits depolarization

Question 5

Absorption

Answer 5

dose
site of injection
drug/tissue interaction
local blood flow (use epi to target alpha 1– vasoconstriction)
physio chem drug properties–inflamation… acidosis… more acid region when molecules are basic…

Question 6

what happens when there is myelination?

Answer 6

sensitivity of nerves to local anesthetic is less

frequency of Na+ channel is spaced out
> distance
< time

Question 7

what happens when there is no/low myelination?

Answer 7

sensitivity of nerves to local anesthetic is more

Question 8

metabolism and excretion

Answer 8

ester: via blood esterases
amide: liver via P450 isozymes (up to 15 hr duration)

2-15 min onset for both

liver disease caution

Question 9

Adverse effects: CNS

Answer 9

CNS: excite followed by depression; convulsions can occur durring excite stage

low dose: sleepy, light head, visual/audio, restless, numbness in toungue

high dose: nystagmus; muscle twitch; convulsions

Question 10

Adverse effects: Cardiac

Answer 10

suppress excitability in myocardium and conduction
bradycardia
heart block
reduce force
cardiac arrest
relax vasc SM vasodilation and hypotension

Question 11

what is PABA

Answer 11

para amino benzoic acid… increase risk for allerge

Question 12

greater chance for allergic rxn in ester or amide

Answer 12

ester – metabolized to PABA which triggers it

Question 13

topical administration

what drugs

Answer 13

applied to skin/mucous membrane
releive pain, itch, soreness

lidocaine/tetrocaine/procaine

Question 14

Pramoxine

Answer 14

itching

Question 15

pramoxine

Answer 15

used with hydrocortisone for rectal hemrrhoids

Question 16

diclonine

Answer 16

in cough meds; oral anesthetic for cough lozenges/ throat spray

Question 17

proparacaine

Answer 17

opthalmic local anesthetic

Question 18

dibucaine

Answer 18

topical anesthetic used in hemmrhoid cream

Question 19

infiltration (injection) anesthesia

Answer 19

injection of local anesthetic into immediate area of surgery

articaine, bupivicaine (cardio depressant), levobupivicaine(less cardiotoxic), chlorprocaine

Question 20

how does duration of anesthesia increase?

Answer 20

w/ epinephrine contraindicated in end tissues (toes, fingers, penis) due to restriction of blood flow causing gangrene

Question 21

nerve block anesthesia

Answer 21

injection of local anesthesia into or near nerve that supplies the surgical area

lidocaine, mepivicaine, levobupivicaine, and ropivicane(3-15 hr duration)

amides have londer duration are chemically stabel

Question 22

IV anesthesia

Answer 22

• used on extremities
• limit systemic circulation
• lidocaine w/o epi is preferred

Question 23

epidural anesthesia

Answer 23

avoid preservatives
after inj of local anesthetic into epidural space, which is in spinal column but outside dura mater.

diffusion of anesthetic across dura into subarachnoid space blocks conduction of nerve roots and conduction in spinal cord

lidocaine bupivicaine levobupivicaine

Question 24

spinal anesthesia

Answer 24

in cerebral spinal fluid in subarachnoid space in the lumbar region below termination of spinal cord

lidocaine, tetracaine, bupivicaine, and levobupivicaine

Question 25

how does epi act on spinal cord

Answer 25

acts on cord to prolong and enhance local anesthetic induced spinal anesthesia by alpha 2 to inhibit substance P neurokinin 1 release

clonidine and precedex are used to augment local anesthetic effect in subarachnoid space

Question 26

concerns regarding use of local anesthetics

Answer 26

esters are contraindicated in pt with allergic rxns

L&D can cause bradycardia and CNS depression

self injury: prevent from happening pt cant feel injury

urine/fecal retention: due to block of autonomic nervous system