Local Anesthetic

Question 1

Local/regional anesthetics:

Answer 1

SNEIS: 
These are drugs used to prevent or relieve pain in specific regions of the body without loss of consciousness
Reversibly block pain sensation by blocking nerve
conduction
1. Surface /Topical
2. Nerve, Regional or Field/Conductive
3. Epidural
4. Infiltration
5. Spinal/Intrathecal

Question 2

Amides and Esters

Answer 2

3 parts
Lipophilic: benzene ring
Intermediate
hydrophilic (lipophobic)

Question 3

all amides have ____ while all esters have _____

Answer 3

2 i’s, 1 i

Question 4

Esters have a half life of _____ metabolized by _______, while Amides have a half life of _____ and are metabolized by _____

Answer 4

seconds to minutes, plasma esterases, hours, microsomal p-450 enzymes in the liver

Question 5

LAs are favored by:

Answer 5

depolization, open or inactivated Na channels, frequent impulses

Question 6

LAs prefer to act upon:

Answer 6

rapidly-firing nerves, so-called “state-dependent blockade” so it is better to have the patient move their arm while you give them the numbing agent

Question 7

the three types of nerve fibers are :

Answer 7

A (alpha, beta, gamma, delta) B, and C (Dorsal Root and Spinal thalamic)

Question 8

The C fibers are ____ and ____ size is _____

Answer 8

smallest, both unmyelinated, and DR>Sym

Question 9

The B fibers are _______ and are _____

Answer 9

myelinated, and are preganglionic autonomic fibers

Question 10

the A fibers are ______ and the order is:

Answer 10

myelinated, proprioception>motor>touch/pressure>muscle spindles>pain and temp

Question 11

S a mple Q: You just finishe d pla cing a S A B (spina l) in a 68 y o ma le for a urologic proce dure using 0.5%
bupivacaine. Which of the following is true concerning the sequence o f blockage by the local
anesthetic?
a ) S y mpa the tics > pa in > te mpe ra ture > touch > pre ssure > motor
b) S ma ll unmy e lina te d > sma ll my e lina te d fibe rs > la rge unmy e lina te d fibe rs> la rge my e lina te d fibe rs
c) A -fibe rs> B -fibe rs> C -fibe rs
d) A ll of the a bov e

Answer 11

A ns we r : A : C -S y m –> C -D R –> D e lta –> B e ta –> A lpha
(Sy m pa the tic ne r v e s , C ty pe fibe r s , a r e v e r y s m a ll)

Question 12

• LA ‘s like myelinated fibers. LA ‘s also like small fibers.
• Small a regenerally blocked before large fibers.
• Size predominates over myelination.

Answer 12

S ympathetics > P ain > Temp > Touch > Pressure > Motor

(S- PT T P- M

Question 13

Cha nne ls c a n e ithe r b e o p e n, c lo s e d o r

s o m e whe r e in b e twe e n.

Answer 13

This means that active
channels (during use /AP propagation)
are easier to block. In theory, if you
wanted to block the brachial
plexus the bes t thing to do would be to have the patient move
their arm around while you
administer the anesthesia
(this is not done in practice )
because you want the channel to be in the depolarized state

Question 14

at low pH, the LA does not work because:

Answer 14

it stays ionized and cannot cross the membrane (it is protonated )

Question 15

A t a hig h p H, the LA will c r o s s the m e m b r a ne (unio niz e d
f o r m = m o r e l i p i d s o l ub l e ), b ut wi l l no t g a i n a f r e e H+ i o n
a nd wi l l no t b i nd the Na + c ha nne l s s o i t wi l l no t wo r k
e i the r .

Answer 15

will c r o s s the m e m b r a ne (unionized form = more lipid soluble ), but will not gain a free H+ i o n
and will no t b i nd the Na + channels s o it will not work
either .

Question 16

The c lose r the ______ the more rapid the onset tim e . (pKa is the pH a t whic h ionized and unionized forms exist in equa l c onc e ntra tions ).

Answer 16

pKa of the LA is to tissue pH,

Question 17

adding a vasoconstrictor:

Answer 17

epinephrine:

fingers, nose, penis, toes, using LAs are a no-go!

Question 18

vasoconstriction:

Answer 18

slows the rate of systemic absorption, therefore a larger amount can be added to solution

Question 19

Ester LAs - metabolized by

Answer 19

plasma esterases.

Question 20

Amide LAs - metabolized (N-dealkylation and hydroxylation) by

Answer 20

microsomal P-450 enzymes in the liver.

Potency correlates with solubility, which in turn reflects the ability of LAs to permeate lipid membranes.

Question 21

LAs are ______, with pKa’s ranging from ______.

Answer 21

weak bases 7.6 9.0; Both the ionic (protonated) and anionic forms are present at physiologic pH. Only the non-anionic form can cross the membrane and gain access to the intracellular domain of the Na+ channel. A low pH (acidotic environment) favors the ionized or ineffective form of theLA. Thus, it won’t work!
LAs bind a specific region of the α subunit and inhibit voltage-gated Na channels, preventing channel activation and the Na influx associated with membrane depolarization. LAs preferentially bind to the open Na+ channel; LAs prefer to act upon rapidly-firing nerves, so-called “state-dependent blockade.

Question 22

Both the ionic (protonated) and anionic forms are present at :

Answer 22

physiologic pH.

Question 23

Only the non-anionic form can cross the membrane and gain access to the

Answer 23

intracellular domain of the Na+ channel.

Question 24

A low pH (acidotic environment) favors the

Answer 24

ionized or ineffective form of theLA. Thus, it won’t work!

Question 25

LAs bind a specific region of the α subunit and

Answer 25

inhibit voltage-gated Na channels, preventing channel activation and the Na influx associated with membrane depolarization.

Question 26

LAs preferentially bind to the

Answer 26

open Na+ channel; LAs prefer to act upon rapidly-firing nerves, so-called "state-dependent blockade.

Question 27

The addition of ______ to LAs is useful to detect intravascular injection, to

Answer 27

The addition of epinephrine to LAs is useful to detect intravascular injection, to increase duration of the blockade, and to prevent systemic absorption and toxicity.

Question 28

Sensitivity of nerve fibers to inhibition by LAs is determined by

Answer 28

axonal diameter, myelination, and other anatomic and physiological factors.

Question 29

These properties explain

Answer 29

the predictable sequence of nerve function blockade -sympathetics, progressing to pain and temperature, followed by proprioception, then touch and pressure, before finally, motor transmission impairment. 

Question 30

The rate of systemic absorption is related to

Answer 30

the vascularity of the site of injection: intravenous (or intra-arterial) > tracheal > intercostal > paracervical > epidural > brachial plexus > sciatic > subcutaneous.

Question 31

The central nervous system is vulnerable to

Answer 31

LA toxicity and is the site of premonitory signs of rising blood concentrations in awake patients.

Question 32

Unintentional intravascular injection of bupivacaine during regional anesthesia may produce

Answer 32

severe cardiovascular toxicity, including left ventricular depression, atrioventricular heart block, and life-threatening arrhythmias such as ventricular tachycardia and fibrillation

Question 33

surface: nerve, regional or field block epideral or spinal blocks infiltration

Answer 33

``` nasal epithelium large area of block small amount of local anesthetic lower concentration higher volume before needle goes in use sub q lidocaine ```

Question 34

mnemonic for fibers:

Answer 34

sympathetic, pain temperature, touch, pressure, motor

Question 35

small unmylinated vs bigger mylinated

Answer 35

always the smaller, then the mylinated

Question 36

what are the layers for getting to the epidural space?

Answer 36

get your skin and fat through the window sil (skin, fassa, supra spinus ligament, infraspinus, ligamentum flava, epidural, dura, subdural, arachnoid, subarachnoid, pia

Question 37

epidural: stick in and add a tiny amount of ____ to see if _____

Answer 37

norephinephrine to see if there is any tachycardia (Beta receptors)

Question 38

differential block is:

Answer 38

analgesia without motor block

Question 39

if pH is too ____ the LA will _____

Answer 39

low, not be able to enter cell,

Question 40

if the LA is not in the _____ it will ______

Answer 40

free base state, not be able to get in the nerve

Question 41

with _____ and an infection, the ph will be ______, and thus the balance between ____ and _____ will be______

Answer 41

diabetes, too low, ph and pka

Question 42

in infected tissue, the LA is ______ and ________ thus the need for sedation

Answer 42

completely ionized, won't work (pka = tissue pH, the faster it will work)

Question 43

all LA are _____

Answer 43

weak bases,

Question 44

_____ are used to prolong the effect and prevent reapsorbtion of the LA into the blood

Answer 44

vasoconstrictors (epinephrine) (epinepherine is prefered) reduces neph

Question 45

the further away the pka is from the _______, the ______

Answer 45

physiologic pH, slower it is to act

Question 46

vasocontrictors are contraindicated for:

Answer 46

end organs i.e. fingers nose, earlobes, penis toes: can cause hypoxic tissue

Question 47

epinephrine works on:

Answer 47

alpha 1 and beta 1

Question 48

early sign of cns toxicity of la?

Answer 48

tinnitus, vertigo, loss of feeling in lips, etc- sign that you injected into vessels

Question 49

what influences LA blood levels?

Answer 49

drug type (ester or amide due to rapid metabolism) pattern of absorption site of administration (with injection near vascular region)

Question 50

influence of LA concentration in blood depending on injection site?

Answer 50

sub q lowest, iv highest

Question 51

cns toxicity:

Answer 51

don't treat minor reactions

Question 52

ester LA metabolized by______, amide LAs metabolized ______ by ________

Answer 52

plasma esterases, n-deakylation and hydroxylation) by microsomal p-450 enzymes in the liver

Question 53

once across the membrane the LA is in the ______ form which binds the ______ domain of the _______

Answer 53

ionic form, intracellular domain of the Na+ channel

Question 54

LA bind a specific region of the _____ and inhibit ______

Answer 54

alpha subunit and voltage gated sodium channel

Question 55

_______ is added to LA to detect ________

Answer 55

epinephrine, intravascular injection

Question 56

halogenated anesthetics may produce malignant hyperthermia in patients with:

Answer 56

a genetic defect in muscle calcium regulation

Question 57

children with asthma undergoing surgery are given ____ bc:

Answer 57

sevoflurane, it does not irritate the airway

Question 58

sevoflurane does not irritate the airway bc:

Answer 58

it is an inhalation anesthetic with low pungency that is nonirritative and therefore it is less likely to cause laryngospasm

Question 59

the volatile general anesthetic that is most likely to require administration of a muscle relaxant:

Answer 59

nitrous oxide

Question 60

no requires a muscle relaxant bc:

Answer 60

it has virtually no muscle-relaxing properties

Question 61

which iv general anesthetic is a potent intravenous anesthetic but a weak analgesic?

Answer 61

thiopental

Question 62

thiopental is ________acting barbiturate that has a ______ solubility

Answer 62

ultrashort-acting, high lipid

Question 63

which volatile anesthetic is a potent analgesic but a weak anesthetic?

Answer 63

NO

Question 64

NO is constantly combined with ______ for _______

Answer 64

oxygen: 70/30 for an analegesic especially for dental surgery

Question 65

order of nerve depolatization with anesthetics:

Answer 65

symPatheTic (sym-pain-tem) propriocepTouch Pressure Motor