Local Anesthetics

Question 0

Local anesthetics are poorly __ soluble unless prepared as HCl salts

Answer 0

water

Question 1

What is the Gold Standard of Local Anesthetics?

Answer 1

Lidocaine

Question 2

HCl salts contribute to local anesthetic __

Answer 2

stability

Question 3

LA’s containing epi may have pH lowered to __ with sodium bisulfate

Answer 3

4.0

Question 4

Lower pH’s prevent oxidative decomposition of __

Answer 4

epinephrine

Question 5

the hydrophilic portion of LA’s is a tertiary __

Answer 5

amine

Question 6

the lipophilic portion is an unsaturated aromatic ring like __

Answer 6

PABA

Question 7

is the lipo or hydrophilic portion essential for anesthetic activity?

Answer 7

lipo-philic, because it can pass the lipid bilayer

Question 8

what does an ester linkage look like?

Answer 8

-CO-

Question 9

what does an amide linkage look like?

Answer 9

-NHC-

Question 10

Name all the esters

the one eyed ester bunny

Answer 10

Chloe drank four coke’s like a pro

Chloro Tetra Cocaine Procaine

Question 11

Pipecoloxylidides like mep, bup, and rop are __ molecules that have assymetric carbon atoms and result in both left and right handed configurations.

Answer 11

chiral

Question 12

“S” enantiomers are __ than “R” enantiomers which are __

Answer 12

“S”safer

“R”risky

Question 13

How do LA’s work?

Answer 13

inhibit passage of sodium ions through channels in nerve membranes

Question 14

LA binding to sodium channels is __ specific

Answer 14

stereo

Question 15

sodium channels are __ when activated AND closing

Answer 15

open

Question 16

sodium channels are __ when OPENING and RESTING

Answer 16

CLOSED

Question 17

resting is an equilibrium between __-closed and __-closed

Answer 17

rested-closed and inactivated-closed

Question 18

LA’s work on sodium channels in the __ open and __ closing states

Answer 18

final open

intermediate closing

Question 19

Sodium channels partially recover from LA blockade BETWEEN action potentials, but LA’s strengthen their blockade each time sodium channels open DURING subsequent action potentials

Answer 19

recover between AP’s but

deeper block with subsequent AP’s

Question 20

the more actively firing a nerve, the easier it is to block. again, LA’s have easiest access to sodium channels in the __ open and __ closing states

Answer 20

final open

intermediate closing

Question 21

Cm = MAC for local anesthetics

Answer 21

minimum concentration needed to block

Question 22

bigger nerves have __ Cm

Answer 22

bigger

Question 23

Acidic tissues have __ Cm

Answer 23

higher

Question 24

how does pKa affect Cm?

Answer 24

the further the pKa from physiologic pH, the more Cm you're gonna need.

Question 25

Faster firing nerves have __ Cm's

Answer 25

lower | because there are more opportunities for the LA to block when the channels are constantly opening and closing.

Question 26

motor fibers have 2x the Cm of sensory fibers so...

Answer 26

you're gonna need twice the LA to block motor as you do to block sensory

Question 27

how many nodes of ranvier must be blocked for adequate conduction blockade?

Answer 27

2-3

Question 28

pain fibers (A delta and C) require similar Cm's for blockade, but B fibers (sympathethic) require less

Answer 28

so you're gonna knock out the sympathetic nervous system before you block the pain signals

Question 29

In order, what tissues are LA's absorbed and metabolized into first to last

Answer 29

``` lungs VRG skeletal muscle fat metabolism elimination ```

Question 30

the greater the protein binding, the __ the plasma drug concentrations

Answer 30

lower, because all of the drug is going to be bound up and none will be available.

Question 31

who has greater systemic absorption, amides or esters?

Answer 31

amides | what do you use for bier blocks? lidocaine which is an amide for better absorption

Question 32

the greater the protein binding, the __ can transfer through the placenta

Answer 32

less, because it's all bound up and too big to fit through the placenta.

Question 33

you don't even have to worry about esters crossing the placenta because__

Answer 33

hydrolyze very quick, ester hydrolysis.

Question 34

how do amides metabolize?

Answer 34

hepatic microsomal enzymes prilocaine fast lido/mepi middle etido, bup, rop slooooow

Question 35

is systemic toxicity more likely with amides or esters?

Answer 35

amides, because esters under quick ester hydrolysis

Question 36

what's so special about prilocaine?

Answer 36

metabolite orthotoulidine can convert hemoglobin to methemoglobin -give methylene blue

Question 37

what is the most slooooowly eliminated amide?

Answer 37

dibucaine | that's why we use a dibucaine number to define a person with atypical plasma cholinesterase

Question 38

why should you consider tetracaine if you want a really loooong acting spinal?

Answer 38

CSF lacks cholinesterase, so the block will last until it is systemically absorbed.

Question 39

what is the cause of most allergic reactions to LA's

Answer 39

the ester bunny's papa | ester metabolite PABA

Question 40

patient allergic to esters may receive amides

Answer 40

and vice versa

Question 41

what is the number one cause of systemic toxicity?

Answer 41

intravascular injection - duh

Question 42

systemic absorption from greatest to least

Answer 42

intercostal epidural brachial plexus ribs, spine, arms ieb - in emergency break glass

Question 43

the lower the PaCO2, the higher the seizure threshold, so_

Answer 43

hyperventilate your patient

Question 44

hyperkalemia (as in end stage renal pt in for shunt revision) has a higher probability of seizing.

Answer 44

don't try a block with a K of 7.0 and a biphasic qrs

Question 45

transient radicular irritation symptoms usually disappear in one __

Answer 45

week

Question 46

__ has a lower incidence of transient radicular irritation than lido

Answer 46

bup

Question 47

hyperbaric 5% lido is the LA implicated in the horse's tail

Answer 47

cauda equina from 5% lido

Question 48

high doses of LA's produce hypotension due to __ and __ by blocking sodium channels and decreasing cAMP

Answer 48

arteriolar relaxation and myocardial depression

Question 49

limit epidural bup concentrations to ___% due to cardiac toxicity

Answer 49

0.5% bup, pretty standard concentration of bup

Question 50

can you use EMLA cream on someone with methemoglobinemia?

Answer 50

Nope, cause it's prilo and lido

Question 51

LA's diffuse from the mantle (outside) to the core (center). Are fibers in the mantle proximal or distal

Answer 51

proximal, they are added to the top layer as the nerve ascends to the spinal cord, thus anesthesia develops proximally and spreads distally

Question 52

what LA's can you use for bier block

Answer 52

lido or prilo, same as in EMLA cream

Question 53

during epidural, the motor blockade may extend 4 segments __ the block

Answer 53

below

Question 54

for spinals, the SNS block may extend 2 segments __ than the sensory block, but the motor block may extend 2 segments __ than the sensory block

Answer 54

SNS 2 segments higher | motor 2 segments lower

Question 55

even though capacitance vessel dilation does occur below the level of spinal anesthesia, compensatory vasoconstriction occurs in the upper extremities and DOES NOT involve the central vasculature

Answer 55

DOES NOT

Question 56

__ circulation alterations are the most important physiologic events occurring with spinals

Answer 56

venous | because unlike arterioles, they cannot maintain intrinsic tone. SO tank em up first with a liter or two

Question 57

where are the cardiac accelerators?

Answer 57

T1-T4

Question 58

what is the bainbridge reflex?

Answer 58

decreased venous return = lower heart rate I know it doesn't make any sense, that just the way it is.