Local Anesthesia

Question 1

A group of drugs that can be used in regional anesthesia for their ability to block nerves and eliminate sensory and motor responses are _

Answer 1

Local anesthetics

Question 2

What are the 2 classes of local anesthetics? How can you tell them apart based on their names?

Answer 2

Amides and esters

Amides will have an “I” before the “caine”

Question 3

Where are amides metabolized? Where is tetracaine metabolized?

Answer 3

In the liver

By plasma esterases

Question 4

What are 2 topically available ester local anesthetics?

Answer 4

Cocaine and benzocaine (OTC)

Question 5

How is lipid solubility associated with potency of local anesthetics?

Answer 5

Increased potency with increasing hydrophobicity (requires smaller doses)

Question 6

Local anesthetics are weak bases. This means they are easily _

Answer 6

Protonates and deprotonates at close to neutral pH

Question 7

What is the mechanism by which local anesthetics mediate their actions?

Answer 7

They are administered, cross the membrane, become charged and the block sodium channels from the inside of the cell.

Question 8

What ion movement is required to initiate the action potential? In what direction?

Answer 8

Inward flow of sodium

Question 9

Relative to the axon, how is a drug like lidocaine administered? How much is needed?

Answer 9

Administer along the axon

Need to administer large volumes of the drug

Question 10

How does an acidotic tissue, e.g. pH of 7.2, affect the amount of non-ionized local anesthetic? What is a clinical condition where this may be a consideration?

Answer 10

Decreased pH means less drug in non-ionized form

In cases of ischemia

Question 11

What is a potential reason for anesthesia failure regarding local anesthetic? How can this be circumvented?

Answer 11

In acidotic tissue, not enough drug in uncharged form to cross the membrane and have effect
Can be circumvented by moving away from the acidotic tissue

Question 12

For a theoretical local anesthetic, will majority of the drug be charged or uncharged at pH=6? pH=8?

Answer 12

pH=6 - most drug is in charged form

pH=8 - most drug is in uncharged form

Question 13

True or false - a local anesthetic may be alkalinized to increase its effectiveness?

Answer 13

True

Question 14

True or false - anesthesia failure due to acidotic tissue can generally be overcome with volume?

Answer 14

False

Question 15

Seizures, trouble breathing, a lot of muscle activity and increased lactic acid build up are associated with _

Answer 15

Local anesthesia toxicity

Question 16

What are the 2 nerve types associated with pain transmission? Which is more resistant to local anesthetic?

Answer 16

A-delta and C fibers

C-more resistant to blockade

Question 17

True or false, local anesthetics block sensory, motor and autonomic nerves

Answer 17

True

Question 18

A funny taste in mouth, ringing in ears, audio disturbances are all associated with _. Why can this easily happen?

Answer 18

Local anesthesia toxicity

Veins are closely situated with nerves

Question 19

What drug can be used to blunt the plasma levels of a local anesthetic?

Answer 19

Epinephrine

Question 20

What are 2 drug classes used to treat seizures associated with local anesthetic toxicity? What can be used to sequester local anesthetic in cases of cardio-toxicity?

Answer 20

Barbiturates and benzodiezapines for seizures

Intralipid to sequester lipid soluble anesthetic

Question 21

Which of the 2 types of local anesthetics is most likely to cause an allergic reaction? What other substances may contribute to allergic reaction to local anesthetics?

Answer 21

Esters

Epinephrine and preservatives

Question 22

What are 2 topical anesthesia preparations? Which is associated with methemaglobinemia?

Answer 22

Lidocaine 
Benzocaine (methemaglobinemia)

Question 23

What drug is used for inflitration anesthesia to start IVs and minor surgeries? How is it administered?

Answer 23

Lidocaine

Administered IV and subQ

Question 24

What is a technique used for administration of IV regional anesthesia to reduce toxicity by preventing drug escaping extremity?

Answer 24

Bier Block

Question 25

How can you find the nerve that you want to anesthetize?

Answer 25

Use electrical stimulation to locate the nerve in question

e.g. sciatic or femoral nerve blockade

Question 26

What is a major effect associated with topical cocaine?

Answer 26

Major vasoconstrictor

Question 27

Myocardial ischemia and infarction, arrhythmias, seizures, hypertension, intracerebral hemorrhage are all associated with the use of _

Answer 27

Topical cocaine

Question 28

What is ropivacaine? What is an advantage?

Answer 28

S-isomer of racemic ropivacaine mix

Less toxicity than racemic bupivacaine

Question 29

What is a way to control the level at which an anesthetic may act within the spine?

Answer 29

Use an additive to increase baricity (e.g. 8.5% dextrose)

Question 30

How does bupivacaine compare to lidocaine?

Answer 30

Bupivacaine more lipid soluble and more potent