6th lecture - local anesthetics

Question 1

local anesthetics are

Answer 1

Substances that cause reversible local anaesthesia by affectingg sensory nerve fibres and endings, inducing absence of sensation.

They prevent the conduction of nerve impulses from the peripheral nervous system to the brain.

All types of sensation are switched off, including the sensation of pain.

Question 2

The order in which sensation disappears:

Answer 2

pain, cold, warmth, touch and pressure sensation.

Question 3

local anesthetic substances can be divided into (2)

Answer 3

esters & amides

Question 4

local anesthetic esters (3)

Answer 4

Cocaine (not a medicinal product anymore)
Procaine (novocaine)
Tetracaine (Dicaine)

Question 5

local anesthetic amides (4)

Answer 5

lidocaine
mepivacaine
bupivacaine
ropivacaine

Question 6

Mechanism of action of local anesthetics

Answer 6

They inhibit the function of various ion channels.

Most important is the prevention of the movement of Na+ ions, which increases the depolarization threshold.

Depending on the pH of tissue, local anaesthetics in the organisms mainly take the form of cations.

Non-ionised forms are capable of penetrating cell membranes.

Question 7

local anesthetics reduce the permeability of the cell membrane to

Answer 7

Na+ ions, closing Na+ channels, thereby preventing membrane depolarization, this leads to anaesthesia.

According to some theories Ca2+ ions are also involved in the mechanism of action.

Question 8

Pharmacokinetics of local anesthetics
Metabolized in the

Answer 8

liver and in blood plasma by way of hydrolysis, catalyzed by non-specific pseudocholinesterase.

Question 9

After metabolism, local anesthetics are excreted through the kidneys. Excretion depends on

Answer 9

urine pH.

Excretion is slowed down in alkaline urine because metabolites are not ionized.

Excretion is enhanced in case of acidic urine.

Question 10

Describe Procaine

Answer 10

was the most used local anaesthetic before the amide-type local anesthetics were launched on the market (procaine is an ester), lately authorised again, used widely.

Reduces cardiac excitability, has an antiarrhythmic effect.

In case of large doses, a sharp decrease in blood pressure will occur.

Question 11

Procaine is used to perform what type of anesthesia?

Answer 11

infiltration, epidural and paravertebral anaesthesia.

Question 12

What is infiltration anesthesia?

Answer 12

Infiltration anesthesia is accomplished with administration of the local anesthetic solution intradermally (ID), subcutaneously (SC), or submucosally across the nerve path that supplies the area of the body that requires anesthesia.

e.g. local blocking a surgical wound

Question 13

When procaine is used in combination with penicillin intramuscularly, it does what

Answer 13

it slows/prolongs the release of the penicillin.

Question 14

lidocaine Effect is 2 times stronger than that of

Answer 14

novocaine.

Question 15

Lidocaine is used for

Answer 15

infiltration, epidural and topical anaesthesia.

Question 16

Lidocaine metabolism occurs in the

Answer 16

liver, excretion with urine. It quickly penetrates the placental barrier.

Question 17

Lidocaine sideffects/signs of overdose

Answer 17

Muscular tremor,
hypotension,
nausea,
vomiting and
cramping may occur in case of overdose.

The toxicity of lidocaine increases depending on concentration.

Question 18

What substance increases the toxic effect of lidocaine.

Answer 18

Pentobarbitone (pentobarbital)

Question 19

Which local anesthetic substance can be used to treat heart rhythm disorders in dogs.

Answer 19

Lidocaine because it Has a strong antiarrhythmic effect

Question 20

what is Etidocaine

Answer 20

A long-acting derivative of lidocaine.

It is suitable as a component of surgical anaesthesia, its postoperative analgetic effect is weaker.

Rarely used in veterinary medicine.

Question 21

describe Mepivacaine

Answer 21

Its effect is similar to that of lidocaine but it is less toxic.

Onset of action is slower and duration of activity is longer than that of lidocaine.

It is not an effective topical anesthetic.

Question 22

describe Bupivacaine

Answer 22

Long duration of action.

It is 4 times more potent than lidocaine but more toxic.

It is used for infiltration, nerve blocks, spinal and intrathecal techniques.

Because of cardiotoxicity its use in intravenous regional anaesthesia is contraindicated.

Question 23

liquid nitrogen also known as?

Answer 23

Chloroethane

has been used as a local anesthetic for small areas of skin. used for removal of small skin lesions too.

Question 24

describe local anesthetic toxicity/ side effects

Answer 24

Primarily related to systemic toxicity or hypersensitivity.

Toxic doses also cause a decreased cardiac output, slowdown in impulse transmission, decrease in blood pressure, dysarrhythmias (although lidocaine is used for stabilizing ventricular dysarythmias).

Cause of death is respiratory arrest.

Question 25

What should you consider in the case of Animals that experience disturbed blood flow to the liver (hypotension, heart failure, old animals)?

Answer 25

they are more sensitive to local anaesthetics.

Reduce local anesthetic dosage by 40-60%.

Question 26

which are more sensitive to local anesthetics, cats or dogs

Answer 26

Cats are more sensitive, doses are lower compared to dogs.

Question 27

side effect/complication of Epidural administration may cause

Answer 27

intercostal nerve and diaphragm paralysis.