Local anesthetics

Question 1

What are local anesthetics

Answer 1

Substances that cause reversible local anesthesia by touching sensory nerve fibres and endings - inducing absence of sensation

Question 2

How do local anesthetics work?

Answer 2

They stop the movement of nerve impulses from peripheral nervous system to the brain.W

Question 3

In which order does sensation disappear?

Answer 3

Pain
Cold
Warm
Touch and pressure

Question 4

Representatives of local anesthetics

Answer 4

Esters
-Cocaine, Procaine, Tetracaine
Amides
- Lidocaine
- Mepivacaine
- Bupivacaine
- Ropivacaine

Question 5

Mechanism of action

Answer 5

Inhibit function of various ion channels
- Preventing movement of Na ions, increasing the
depolarisation threshold.
- Reduce permeability of cell membrane to Na ions, closing
Na channels - thereby preventing membrane
depolarisation, leading to anesthesia

Question 6

Pharmacokinetics

Answer 6

Metabolism in liver and in blood plasma occurs by way of hydrolysis, catalyzed by pseudocholinesterase
-Excreted via kidneys - depending on urine pH
>Slowed down in alkaline urine (metabolites not ionized)
>Enhanced in case of acidic urine

Question 7

Infiltration anesthesia

Answer 7

Like when you inject lidocaine underneath the skin before cutting into it

Question 8

Procaine

Answer 8

Weak organic base
Used to perform infiltration, epidural and paravertebral anesthesia
Reduces cardiac excitability - has an antiarrhythmic effect
In large doses, sharp decrease in bp occurs

Question 9

Lidocaine

Answer 9

2x stronger effect than novocaine
Used for block, infiltration, epidural and topical anesthesia
Quickly penetrates placental barrier
Strong antiarrhythmic effect
Pentobarbitone increases the toxic effect

Question 10

Symptoms of lidocaine overdose

Answer 10

Muscular tremors, hypotension, nausea, vomiting and cramping

Question 11

Block anesthesia

Answer 11

Anesthetic is injected around the nerve; it inhibits the impulses that are being transmitted via it

Question 13

Bupivacaine

Answer 13

Long duration of action
4x more potent and toxic than lidocaine
Used for infiltration, nerve blocks and spinal & intrathecal techniques

Question 14

Substances with local anesthetic effect

Answer 14

Chrloroethane, liquid nitrogen
Suitable for anesthetics for small areas of skin - if administered to large; frozen site will be painful afterwards
->Not in mouth or nose; may cause deep anesthesia resulting in death

Question 15

Local anesthesia toxicity; side effects

Answer 15

Primarily related to system toxicity or hypersensitivity
Stimulation of CNS, muscle tremors & cramps - followed by depression
->Cause of death is respiratory arrest