Hadzics Chapter 2

Question 1

What is the resting potential range in neurons?

Answer 1

–60 to –70 mV

Set by the Na⁺/K⁺ ATPase pump.

Question 2

What determines the resting potential in neurons?

Answer 2

High intracellular K⁺, low intracellular Na⁺

The membrane is more permeable to K⁺, leading to a negative interior.

Question 3

List the steps of action potential.

Answer 3

• Stimulus → threshold reached
• Depolarization: Na⁺ influx
• Repolarization: K⁺ efflux
• Refractory period: Na⁺ channels reset

Question 4

What is saltatory conduction?

Answer 4

Myelin speeds conduction allowing impulses to ‘jump’ at Nodes of Ranvier

These nodes have high Na⁺ channel density.

Question 5

How do local anesthetics (LAs) affect nerve conduction?

Answer 5

Block Na⁺ entry → stop depolarization → nerve conduction halts

Question 6

Where do local anesthetics bind?

Answer 6

Inside the sodium channel (α-subunit)

Question 7

What is the process for local anesthetics to bind to the sodium channel?

Answer 7

Unionized form crosses lipid membrane → converts to ionized form in axoplasm → binds channel

Question 8

What is meant by ‘use-dependent block’ in local anesthetics?

Answer 8

LAs preferentially bind open and inactivated states during repeated firing

Question 9

Which nerves are less sensitive to local anesthetics?

Answer 9

Resting nerves are less sensitive than active/repeatedly stimulated nerves

Question 10

What are the three essential components of local anesthetics?

Answer 10

• Aromatic ring (lipophilic)
• Intermediate chain (ester or amide)
• Amine group (hydrophilic)

Question 11

What does the pKa of local anesthetics affect?

Answer 11

Proportion of ionized vs unionized forms

Most LAs have a pKa of 7.6–9.0.

Question 12

How does infection affect local anesthetic efficacy?

Answer 12

More ionized drug in acidic tissue → poor block

Question 13

What is the relationship between lipid solubility and local anesthetics?

Answer 13

Lipid solubility = potency and toxicity risk

Question 14

What determines the duration of action of local anesthetics?

Answer 14

Protein binding

Question 15

What factors influence the onset of local anesthetics?

Answer 15

Lower pKa → faster onset

Question 16

Which local anesthetic has a faster onset, lidocaine or bupivacaine?

Answer 16

Lidocaine (pKa 7.8) is faster than bupivacaine (pKa 8.1)

Question 17

What is the order of nerve fiber sensitivity to local anesthetics?

Answer 17

• Pain (Aδ, C fibers)
• Temperature
• Touch & pressure
• Motor (Aα fibers)

Question 18

Which function typically disappears first when using local anesthetics?

Answer 18

Pain disappears first, motor function lasts

Question 19

What is the typical order of recovery from local anesthetic block?

Answer 19

• Motor function (Aα)
• Proprioception & pressure (Aβ)
• Touch (Aβ)
• Temperature (Aδ)
• Pain (C fibers, Aδ)

Question 20

True or False: Patients regain motor function before feeling temperature or pain after local anesthesia.

Answer 20

True

Question 21

What are the two main types of local anesthetics?

Answer 21

Esters and Amides

Esters have one ‘i’ in the name, while Amides have two.

Question 22

What is the metabolism process for Esters?

Answer 22

Plasma cholinesterase metabolism

Esters have a higher allergy risk due to the PABA byproduct.

Question 23

What is the main characteristic of Chloroprocaine?

Answer 23

Rapid onset, short duration, very low toxicity

Good for short cases.

Question 24

What is Procaine known for?

Answer 24

First synthetic LA, slow onset, short duration, vasodilator

Rarely used now.

Question 25

What are the properties of Tetracaine?

Answer 25

Potent, long-acting, high toxicity risk ## Footnote Commonly used in spinal anesthesia.

Question 26

What is unique about Cocaine as a local anesthetic?

Answer 26

Inhibits catecholamine reuptake → vasoconstriction, abuse potential, ENT use ## Footnote It is the only local anesthetic with these properties.

Question 27

What is the metabolism process for Amides?

Answer 27

Hepatic metabolism ## Footnote Amides have a rare allergy risk.

Question 28

What is Lidocaine known as?

Answer 28

Gold standard local anesthetic ## Footnote It has intermediate duration and versatility in use.

Question 29

How does Mepivacaine compare to Lidocaine?

Answer 29

Similar to lidocaine, less vasodilation, slightly longer duration ## Footnote Both are commonly used local anesthetics.

Question 30

What potential side effect is associated with Prilocaine?

Answer 30

Can cause methemoglobinemia ## Footnote This is due to its metabolite o-toluidine.

Question 31

What is notable about Bupivacaine?

Answer 31

Very potent, long duration, highly cardiotoxic ## Footnote It is advised to avoid large doses.

Question 32

What is Levobupivacaine?

Answer 32

S-enantiomer of Bupivacaine, less cardiotoxic ## Footnote Considered a safer alternative.

Question 33

What are the characteristics of Ropivacaine?

Answer 33

Long-acting, less lipid soluble than bupivacaine → less motor block, less cardiotoxic ## Footnote This makes it a preferred option in certain situations.

Question 34

What is the effect of adding Epinephrine to local anesthetics?

Answer 34

Epinephrine causes vasoconstriction, which decreases absorption, prolongs duration, and lowers toxicity risk. ## Footnote It also serves as a marker for intravascular injection (↑HR, BP).

Question 35

What is the role of Opioids in neuraxial anesthesia?

Answer 35

Opioids provide synergistic analgesia when added to local anesthetics (e.g., morphine, fentanyl).

Question 36

What is Clonidine and its effects when added to local anesthetics?

Answer 36

Clonidine is an α2 agonist that prolongs the block and may cause some hypotension and bradycardia.

Question 37

What is Dexmedetomidine and its effects when added to local anesthetics?

Answer 37

Dexmedetomidine is a more potent α2 agonist that extends the block by approximately 4 hours and can cause sedation and bradycardia.

Question 38

What is Dexamethasone's role in local anesthesia?

Answer 38

Dexamethasone is a corticosteroid that prolongs the block, especially perineural, with a low risk of side effects.

Question 39

What are the early signs of CNS toxicity from local anesthetics?

Answer 39

Early signs include circumoral numbness, tinnitus, metallic taste, and seizures.

Question 40

What are the signs of CV toxicity from local anesthetics?

Answer 40

CV toxicity can manifest as hypotension, arrhythmias, and cardiac arrest, with the worst effects seen with bupivacaine.

Question 41

What is the treatment for severe Local Anesthetic Systemic Toxicity (LAST)?

Answer 41

The treatment for severe LAST is lipid emulsion therapy, also known as 'lipid rescue.'