local anesthetics nagelhout

Question 1

T/F Myelinated nerves are larger, conduct impulses faster, and are more difficult to block with local anesthetics than are unmyelinated nerves.

Answer 1

TRUE

Question 2

what are the two opposing forces that influence K movement into and out of the neuron?

Answer 2

a concentration gradient pushes K outward. an electrostatic gradient, created by the impermeability of the membrane to cations, tends to keep the K in the cell.

Question 3

local anesthetics bind to the ___ and ___ states, but not the ___ state

Answer 3

open and inactivated.

not the closed

Question 4

what is the order of differential blockade?

Answer 4

autonomic, superficial pain, touch, and temp, motor function, and proprioception

Question 5

the ___ fibers are the largest in diameter and most heavily myelinated

Answer 5

A

Question 6

which fibers have the fastest conduction velocity?

Answer 6

Alpha

Question 7

the __ fibers, which conduct pain and temp impulses, are the smallest of all fibers.

Answer 7

C

Question 8

T/F C fibers are myelinated

Answer 8

FALSE.

Question 9

The small, unmyelinated C fibers are more or less resistant to blockade than the larger A delta or B fibers?

Answer 9

MORE

Question 10

diffusion across the membrane is influenced by what three factors?

Answer 10

PKA, concentration of local anesthetic, ph of surrounding tissue and nerve fiber

Question 11

which part of the structure provides lipophilic characteristics?

Answer 11

aromatic ring

Question 12

which part of the structure provides hydrophilicity to the molecule?

Answer 12

tertiary/ quaternary amine

Question 13

what is the major difference among local anesthetics chemically/

Answer 13

the major diff is in their ester or amide linkage that binds the aromatic ring to the amine group

Question 14

how can you tell if a drug is an amide?

Answer 14

has 2 letter i’s in the name

Question 15

how are esters metabolized?

Answer 15

catalyzed by plasma and tissue cholinesterase via hydrolysis, occurs throughout the body and is rapid

Question 16

how are amides metabolized?

Answer 16

in the liver by cyp1A2 and cyp3A4 (and thus a significant blood level may develop with rapid absorption)

Question 17

which class has a higher allergic potential?

Answer 17

esters.

Question 18

ester drugs are long or short acting? why

Answer 18

esters are shorter acting d/t their metabolic, tetracaine is the longest acting ester

Question 19

amides are short or long acting? why

Answer 19

amides are longer acting bc they are more lipophilic and protein bound and require transport to the liver for metabolism

Question 20

the higher the concentration of drug injected into the area of nerve or nerves to be blocked, the ___ the onset of action. if multiple nerves are being blocked, a ____ intensity might also be evident.

Answer 20

faster, greater

Question 21

Systemic absorption away from the deposition site results in the ___ and ___ of the drug effect, rather than the ___ as with most other drugs.

Answer 21

offset & termination. rather than onset

Question 22

what are the factors that influence duration of action?

Answer 22

factors that affect absorption such as vascularity and blood flow of the injection area, lipid and protein binding, and addition of vasoconstrictors

Question 23

Increased lipid solubility correlates with ___ protein binding, ____ potency, ____ DOA, _____ tendency for severe cardiac toxicity

Answer 23

increased, increased, longer, higher

Question 24

LA’s are ___ (strong/weak) _____ (acid/base)

Answer 24

weak base

Question 25

LA's bind mainly to ____

Answer 25

a1-acid glycoprotein | secondary binding to albumin also occurs

Question 26

the more ___ LA is, the slower it will penetrate a nerve

Answer 26

ionized

Question 27

because their ionization is less, LA's with lower pKa (7.6 to 7.8) such as lidocaine, mepiviacine, and prilocaine tend to have a ___ onset of action than drugs with a greater pKa (8.1 to 8.6). the exception to this is _____

Answer 27

rapid chloroprocaine

Question 28

the closer to pka is to 7.4, the more __ the onset

Answer 28

rapid

Question 29

T/F the total dose of LA rather than the volume or concentration linearly determines the peak plasma concentration.

Answer 29

TRUE. | volume doesn't matter - dose does

Question 30

does using epi increase or reduce the risk of systemic toxicity of LA?

Answer 30

reduce.

Question 31

what does the addition of bicarb do to local anesthetics

Answer 31

it increases the non-ionized portion of the drug which facilitates the drug's passage across the neuronal membrane and speeds onset. it also prolongs the duration and reduces pain on injection

Question 32

what are the 3 major factors contributing to the negative chronotropic and inotropic effect's of LA's?

Answer 32

hypoxia, hypercarbia, acidosis

Question 33

In adults, the subarachnoid space extends from the foramen magnum to __ and extends to ___ in children.

Answer 33

S2, S3

Question 34

The spinal cord itself extends to __ in adults and __ in children.

Answer 34

L1, L3

Question 35

during a spinal, the first pop is the needle penetrating the ____ and the second is ___

Answer 35

lig flavum, dura mater

Question 36

what is the specific gravity of CSF?

Answer 36

1.003 to 1.008

Question 37

acidosis ___ plasma protein binding, which ____ the free form of the drug in the bloodstream, which results in ___ amt available for diffusion in the brain

Answer 37

decreases, increases, increases

Question 38

the standard concentration of epi added to a local anesthetic to prolong the duration of an epidural block is __mcg/ml, which represents a _:_____ solution

Answer 38

5 mcg/ml, 1:200000

Question 39

the addition of epi to what drugs significantly affects duration of action?

Answer 39

mepivacaine, lidocaine..

Question 40

all locals cause vasodilation except for which 3?

Answer 40

cocaine, lido, ropivacaine

Question 41

what are the two principal determinants of the duration of action of a spinal

Answer 41

the anesthetic drug used and the total dose given

Question 42

which locals are associated with the highest risk of allergic reaction?

Answer 42

esters - procaine, cholorprocaine, tetracaine, benzocaine... PABA, patients have previous exposure in lotions sunscreens cosmetics etc

Question 43

what things added to a LA makes it hyperbaric

Answer 43

dextrose. sterile water makes it hypobaric

Question 44

0.1 to 0.2 mL of 1:1000 (1 mg/mL) epinephrine is the dose typically added to the local anesthetic to prolong the duration of the spinal.

Answer 44

learn how to divide these out.........

Question 45

mechanism of action of LA's

Answer 45

Local anesthetics bind to the alpha-subunit on sodium channels on the inside of the cell membrane and block the large influx of sodium into the cell associated with depolarization.

Question 46

which needles reduce the incidence of PDPH

Answer 46

24-27g pencil point needles

Question 47

what landmark it T4 associated with

Answer 47

superior aspect of the iliac crest

Question 48

what is most important in terms of onset/

Answer 48

ionization- the charged or ionized form of a drug does not penetrate membranes well

Question 49

what is the MOA of bicarb in theory?

Answer 49

addition of bicarb increases the ph of the PA resulting in the presence of more drug in the non-ionized state. this form of the drug readily diffuses across cell membranes, therefore speeds onset

Question 50

explain ion trapping in the fetus

Answer 50

fetal ph is lower than maternal ph which may result in high fetal levels of LA

Question 51

why is injecting local into an acidic environment ineffective

Answer 51

because the loss of lipid solubility prevents absorption into the nerve, therby preventing access to the site of action

Question 52

which ester has a slow metabolism

Answer 52

tetracaine

Question 53

hepatic clearance is a function of ___ and __ and is the primary factor that determines the rate of elimination of ___ LA's

Answer 53

hepatic extraction ration and hepatic blood flow... amides

Question 54

what 2 LA's cause methemoglobinemia?

Answer 54

benzocaine and procaine | nagel also says prilocaine bc of its metabolite

Question 55

what 2 are in the eutectic mixture

Answer 55

lidocaine and prilocaine