Local Anesthetics

Question 1

Nerve Effects

Answer 1

Small Fibers easier to block
Heavily Myelinated nerves easier
Nerve bundles are harder to block
Resting sodium channels have low affinity
Cardiac cells can be susceptible to blockade

Question 2

Lipophilic group

Answer 2

Benzene Ring

Question 3

Hydrophilic group

Answer 3

Tertiary Amine

Question 4

Ester vs amide linkage

Answer 4

classification

Question 5

Amide Vs Ester Classification

Answer 5

Amides have an I before the “caine” and metabolized by the liver
Esters (except cocaine) are metabolized by plasma cholinesterase

Question 6

Potency

Answer 6

Lipid solubility

More lipid soluble is more potent

Question 7

Onset

Answer 7

Lipid solubility and pKa

More lipid solubility is faster onset and closer to tissue pH is faster onset

Question 8

Cm (minimum concentration)

Answer 8

Measurement of the potency. Minimum concentration for anesthetic to work.

Question 9

Para-aminobenzoic Acid (PABA)

Answer 9

Metabolite of Ester local anesthetic metabolism.
This is generally what people are allergic to when they are allergic to LA
Also in sunscreen

Question 10

Methemoglobinemia

Answer 10

Prilocaine/Benzocaine: Ortholuidine
Normal metHgB <1%
Pulse oximeter will go down to 85%
Treat with 1-2mg/kg of methylene blue

Question 11

Vasoconstrictor

Answer 11

Used to increase duration of action by limiting absorption

Common epinephrine 5mcg/mL (1:200,000) mixed in

Question 12

Systemic Toxicity Causes

Answer 12

IV Injection (Most Common)
Absorption from injection site
Depends on: Dose administered, vascularity of site, presence of epi, properties of the drug.

Question 13

Vascularity (From top to least)

Answer 13

Tracheal
Intercostal
Caudal
Paracervical
Epidural
Brachial Plexus
Sciatic
Subcutaneous

Question 14

CNS Systemic Toxicity

Answer 14

Circumoral numbness
Restlessness
Slurred Speech
Seizure

Question 15

CV Systemic Toxicity

Answer 15

Hypotension
Decreased Cardiac Conduction
Ventricular Arrythmias
Bupivicaine (most cardiotoxic)
Treatment is 1.5 mg/kg IV over 10 minutes

Question 16

Systems in order

Answer 16

Circumoral Numbness
Tinnitus
Lightheadedness
Visual Disturbances
Muscle Twitching
Unconsciousness
convulsions
Respiratory Depression
Cardiovascular Collapse

Question 17

Toxic Doses

Answer 17

Lidocaine: 5mg/kg or 7mg/kg with epi
Bupivicaine: 2.5mg/kg

Question 18

Cocaine

Answer 18

Blocks sodium channels, but crosses the BBB easily
Also a vasoconstrictor by blocking reuptake of norepinephrine
IV/smoked onset is 5 minutes
30 minute onset nasal

Question 19

Spinal Anesthesia Lidocaine

Answer 19

Duration: 1.5 hours
5% with 7.5% dextrose
Transient Neurologic Symptoms

Question 20

Spinal Anesthesia Bupivicaine

Answer 20

2-2.5 hours

0.5% and 0.75% with or without dextrose

Question 21

Spinal Anesthesia Tetracaine

Answer 21

2-3 hours up to 5 with epi

1% solution, can be mixed with 10% dextrose

Question 22

Bier Block

Answer 22

Unknown Mechanism of Action
50mL 5% lidocaine or prilocaine
Dose of prilocaine not sufficient for methemoglobinemia

Question 23

EMLA (eutectic mixture of local anesthetic)

Answer 23

Onset: 45-60 minutes
Duration: about an hour
Contraindications: broken skin or baby <12 months]
Dose: 1-2gm/cm^2