Local anesthetics/amides/esters

Question 1

What are nociceptors?

Answer 1

Free nerve endings of primary afferent neurons

Question 2

What is the difference between pain and nociception?

Answer 2

Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, whereas nociception is the detection of a noxious stimulus at the tissue level by nociceptors.

Question 3

What are the 5 nociception pathways?

Answer 3

transduction, transmission, modulation, projection, perception.

Question 4

What nociceptors are present on the distal terminus of primary sensory nerve fibers?

Answer 4

ABeta fibers, A-delta fibers, and C fibers

Question 5

Which nociceptors are responsible for sensing “first pain”?

Answer 5

A-delta fibers

Question 6

What is chronic pain?

Answer 6

pain that persists longer than is providing protection.

Question 7

Neuron alteration occurs through which 2 main changes?

Answer 7

peripheral sensation and central sensitization.

Question 8

What is hyperalgesia?

Answer 8

exaggerated perception of pain produced by a noxious stimulus.

Question 9

What is allodynia?

Answer 9

non-noxious stimulus that elicits pain.

Question 10

Where does central sensitization occur and what receptors does it involve?

Answer 10

It ooccurs in the dorsal horn of the spinal cord and involves NMDA receptors.

Question 11

Does central pain sensitization occur in chronic and acute pain, or just chronic?

Answer 11

chronic and acute

Question 12

What enables low intensity stimuli to produce pain?

Answer 12

changes in sensory processing in the spinal cord.

Question 13

What receptor plays a central role in chronic pain?

Answer 13

NMDA

Question 14

What is the result of increased glutamate in the synaptic cleft?

Answer 14

activates normally closed NMDA receptors.

Question 15

What parts of the pain pathway are affected by local anesthetics?

Answer 15

transduction, modulation, and transmission.

Question 16

Perception is affected by what type of anesthetics?

Answer 16

general anesthetics

Question 17

What are the main effects of local anesthetics?

Answer 17

they cause the reversible blockade of transmission in peripheral nerves or spinal cord to stop pain signaling from progressing.

Question 18

T/F: local anesthetics are any drugs that cause the reversible blockade of nerve impulse conduction when applied locally to nerve tissue.

Answer 18

True.

Question 19

What are 2 classes of local anesthetics?

Answer 19

Amides and esters

Question 20

T/F: all local anesthetics are weak acids.

Answer 20

False. They are weak bases.

Question 21

What is the mechanism of action of local anesthetics?

Answer 21

neurologic blockade occurs by preventing depolarization and blocking the propagation of an action potential by inhibiting the influx of sodium through voltage-dependent Na+ channels.

Question 22

How is the duration of action of local anesthetics usually terminated?

Answer 22

By redistribution.

Question 23

What affects the onset of action of local anesthetics?

Answer 23

physiochemical properties, site of administration, and drug dose.

Question 24

What affects the duration of action of local anesthetics?

Answer 24

lipophilicity, ability to bind the sodium channel, underlying disease, and drug to drug interactions.

Question 25

Where are amides mainly metabolized?

Answer 25

liver

Question 26

what breaks downs esters?

Answer 26

plasma esterases

Question 27

T/F: amide local anesthetics have short half lives.

Answer 27

False. Their half life is long because they are metabolized by the liver.

Question 28

What are some routes of administration for local anesthetics?

Answer 28

topical, local infiltration, or IV regional anesthesia

Question 29

What are some examples of regional analgesia?

Answer 29

Brachial plexus block or an intercostal nerve block.

Question 30

When would a wound soaker catheter be used?

Answer 30

After surgery requiring regional analgesia.

Question 31

What are some contraindications of epidurals and epidural catheters?

Answer 31

coagulopathy, anatomy, skin infection/sepsis, and neurologic disease.

Question 32

What are some complications/adverse effects of epidurals?

Answer 32

local irritation, CNS stimulation, CNS depression, cardiovascular depression, and other less common effects.

Question 33

This drug is the most commonly used local anesthetic in vet med, has a rapid onset of action, and is metabolized by the liver.

Answer 33

Lidocaine.

Question 34

About how long does it take lidocaine cream to take effect?

Answer 34

20-30 minutes.

Question 35

Would you use epi with lidocaine when using lidocaine systemically?

Answer 35

No.

Question 36

What other use does lidocaine have?

Answer 36

antiarrhythmic (ventricular arrhythmias)

Question 37

T/F: lidocaine is used to stimulate intestinal motility in the horse.

Answer 37

True

Question 38

This local anesthetic is potent, has a longer duration of action, and is the most cardiotoxic of the local anesthetics.

Answer 38

Bupivacaine.

Question 39

When should you be weary of using bupivacaine?

Answer 39

in post-op pericardectomy patients.

Question 40

How is bupivacaine infused?

Answer 40

through thoracostomy tubes or soaker catheters.

Question 41

What is mepivacaine used for?

Answer 41

diagnosing nerve blocks in horses and for epidurals.

Question 42

This drug is less irritating and has a longer duration of action than lidocaine, and is preferred for distal limb/intraarticular injections.

Answer 42

Mepivacaine.

Question 43

This drug is an ester, is used topically, has a rapid onset, and allows for corneal and conjunctival manipulation.

Answer 43

Proparacaine.

Question 44

T/F: proparacaine can be used intranasally for nasal-oral feeding tube placement.

Answer 44

True.

Question 45

This ester is not used as a local anesthetic, but is a class 1a antiarrhythmic.

Answer 45

Procainamide

Question 46

Is procaine used as a local anesthetic?

Answer 46

No, but it is present in some penicillin G preparations.