Regional Lecture Test

Question 0

What reverses a local anesthetic?

Answer 0

Time

Question 1

What are the three characteristic segments all local anesthetics have?

Answer 1

• intermediate carbon group (ester/amide)
• unsaturated ring system
• amine end

Question 2

What is the most prominent problem of local anesthetics?

Answer 2

inadvertent vascular injection

Question 3

What is responsible for the classification of a local anesthetic and why?

Answer 3

• The ester or amide linkage

- the only difference between the aromatic ring and amine end

Question 4

How can you differentiate between an ester and amide by looking at the name?

Answer 4

• Esters have one i (procaine,cocaine)

- Amides have two i’s (lidocaine, mepivacaine)

Question 5

What does lipid solubility relate to?

Answer 5

High lipid solubility is proportional to potency of a local anesthetic

Question 6

Definition of Lipophilic/Hydrophobic

Answer 6

Lipophilic-fat loving

Hydrophobic-water fearing

Question 7

Why does lipid solubility affect potency?

Answer 7

Nerve sheath covering is lipid based so other lipids pass through easily

Question 8

What type of binding is related to the duration of action?

Answer 8

Protein Binding

Question 9

Between duration of action and potency, which is more related to lipid solubility?

Answer 9

Potency

Question 10

Sodium channels have what three functional states?

Answer 10

Resting (closed)
Inactive
Open

Question 11

What are the two parts to a local anethestic?

Answer 11

Nonionized (fat soluble

Ionized (water soluble)

Question 12

How does LA work? Part 1

Answer 12

• -Once injected LA dissociates into its active(non-charged) and inactive(charged) forms
• -the non-charged(lipid soluble) part passes through the lipid soluble membrane

Question 13

How does LA work? Part 2

Answer 13

• -the lipid portion that passes through, binds with minerals in axoplasm
• -the reassociated LA blocks the action potential by blocking Na pump and prevents the pain stimulus from moving down the nerve

Question 14

What is the definition of pKa?

Answer 14

pKa is the pH at which 50% of the drug is in the charged (ionized, inactive) form and the remaining half is the uncharged (active) state

Question 15

What is the correlation of pKa and potency?

Answer 15

–the lower the pKa the greater the potency

Question 16

How does pKa work?

Answer 16

• -the lower the pH of the environment the drug is placed into compared to it pKa, the more ionized (inactive) it becomes
• -so the higher the pKa the more inactive it becomes
• -the lower the pKa the more active drug left to work

Question 17

Why are vasoconstrictors added to LA’s?

Answer 17

To decrease the spread , vascular uptake of the drug

Question 18

What 4 helpful things happen when adding a vasoconstrictor to the LA?

Answer 18

• higher local concentration of the LA
• longer duration of effect
• reduced systemic absorption
• hemostasis for improved visualization

Question 19

When should we not use a vasoconstrictor?

Answer 19

• fingers
• toes
• nose
• hose

Question 20

What drug reverses the negative results of a vasoconstrictor in a given area?

Answer 20

-phentolamine 1.5-5mg

Question 21

How are LA with epi packaged?

Answer 21

Red top with red lettering on label

Question 22

What does adding NaHCO3 do to the LA?

Answer 22

• stored at pH of 4-6 for shelf life (decreases unionized/active form)
• buffering with NaHCO3 increases the unionized/active form to increase speed of penetration to nerve tissue

Question 23

All LA, except which three, produce vascular smooth muscle relaxation?

Answer 23

• Cocaine (topical)
• Ropivacaine (parenteral)
• Lidocaine (parenteral)

Question 24

If VSM relaxation occurs, it increases the risk of ________?

Answer 24

toxic effects

Question 25

Which type of tissue receives the most amount of LA if it enters blood stream and why?

Answer 25

Muscle because it is highly perfused

Question 26

How are esters metabolized?

Answer 26

- Ester hydrolysis occurs through esterase - Occurs in plasma, RBC's, and liver - Primarily, Plasma Cholinesterase rapidly metabolizes LA

Question 27

How are amides metabolized?

Answer 27

- occurs primarily in liver - microsomal cytochrome P-450 enzyme - dependent on hepatic blood flow and enzyme availability

Question 28

What are the two most common ways that toxicity occurs?

Answer 28

- inadvertent intravascular injection | - absorption of large amounts of drug from a nerve block that requires large volume

Question 29

LAST stands for what and what 5 things are affected?

Answer 29

- Local anesthetic systemic toxicity (seen 5-10min) - CNS - CV - Allergic Reaction - Methemoglobinemia - Local tissue

Question 30

CNS effects of LAST

Answer 30

Mild = tongue numbness, apprehension, restlessness Moderate = peri-oral tingling, tremors, slurred speech, drowsiness Severe = Seizures, cardiorespiratory depression, coma, death

Question 31

CV LAST effects

Answer 31

- palpitations - HTN - ventricular dysrhythmias - myocardial depression - bradycardia - hypotension - CV collapse

Question 32

PVS LAST effects

Answer 32

- low concentrations-vasoconstriction and increased SVR | - as doses increases significant vasodilation and hypotension occurs

Question 33

Arrythmias with LAST

Answer 33

-LAST effects electrophysiologic and contractile forces - increased PR interval and QRS durations - complete AV block, bradycardia, cardiac arrest

Question 34

What preservative is associated with allergic reactions to LA?

Answer 34

More common in esters due to para-aminobenzoic acid

Question 35

Which three LA can cause Methemoglobinemia?

Answer 35

- Prilocaine (citanest) - Benzacaine - Cetacaine

Question 36

What is the metabolite that causes methemoglobinemia and what are the s/s?

Answer 36

- o-toluidine oxidizes hgb to met-hgb - tachypnea - metabolic acidosis - brownish-gray cyanosis

Question 37

Met-Hgb treatment

Answer 37

- Spontaneous is 2-3 hrs | - methylene blue 1mg/kg

Question 38

LAST treatment

Answer 38

- Airway mgt - seizure suppresion - CPR - alert nearest facility with bypass capabilities - give IV intralipid

Question 39

Intralipid dosing

Answer 39

- Bolus: 20% intralipid 1.5ml/kg over 1 min - Cont: 0.25ml/kg/min - Double infusion if BP returns but stays low - Continue infusion for a minimum of 30 min