Local Anesthetics

Question 1

sodium potassium pump ion conc

Answer 1

3 Na+ out, 2 K+ in

Question 2

*mechanism of action of local anesthetics

Answer 2

bind to a subunit and inhibit voltage-gated Na+ channels; depedent blockage: depolarization encourages more LA binding

Question 3

effect of LA on action potential

Answer 3

slows rate of depolarization of AP so threshold pattern is not reached

Question 4

axonal diameter and myelination related to sensitivity to LA

Answer 4

small diameter-increased sensitivity

myelination- decreases sensitivity

Question 5

*spinal nerve sensitivity relative values

Answer 5

autonomic > sensory > motor

Question 6

two types of local anesthetics and examples of each

Answer 6

amides- lidocaine, bupivacaine, prilocaine

esters- cocaine, benzocaine

Question 7

3 structural features of LA

Answer 7

lipophilic group (benzene ring)

hydrophilic group (tertiary amine)

intermediate chain (amide or ester)

Question 8

the structural component of the LA that acts on Na+ channels

Answer 8

water soluble fraction (hydrophilic part)

Question 9

higher lipid soluble drugs have…

Answer 9

longer duration of action

Question 10

*absorption of LA at the site of injection from method with greatest absorption to least

Answer 10

IV> tracheal> intercostal> paracervical> epidural> brachial plexus> sciatic> subcutaneous

Question 11

vasoconstrictors: less toxic or more toxic?

Answer 11

less toxic b/c decreased absorption and lower peak blood conc

Question 12

the tissue perfusion phases

Answer 12

a phase: rapid initial uptake by brain lung, liver, kidney, heart

B phase: slower redistribution to muscles, bowels.

Question 13

factors affecting distribution

Answer 13

tissue perfusion, tissue/blood partition coefficient, tissue mass

Question 14

biotransformation and excretion of esters vs amides

Answer 14

esters: pseudocholinesterase/plasma cholinesterase
amides: by microsomal P450 enzymes in liver

Question 15

*biotransformation and excretion of prilocaine and benzocaine can cause

Answer 15

methhemoglobinemia via Hb Fe++ becoming Fe+++

Question 16

treatment of methhemoglobinemia

Answer 16

methylene blue (converts Fe+++ to Fe++)

Question 17

LAs administered with epinephrine

Answer 17

lidocaine, mepivacaine

Question 18

LA toxicities

Answer 18

CNS precede CV effects

early: circumoral numbness, tongue paresthesia, dizziness, tinnitus, blurred vision
late: restlessness, agitation, seizures, respiratory arrest, coma

selective blockade of inhibitory pathways

Question 19

treatment for LA toxicities

Answer 19

benzodiazepines, propofol

Question 20

lidocaine IV effects on organ systems

Answer 20

decrease cerebral blood flow, stops rise in ICP during intubation, reduces requirement of volatile anesthetics, decreases inflammation, reduces post op pain and narc requirement, reduces post op hospital stay

Question 21

lidocaine effects on respiratory system

Answer 21

lidocaine depresses the respiratory response to low blood oxygen level; its a bronchodilator

Question 22

*treatment for lidocaine toxicity in cardiovasculature

Answer 22

intralipids IV bolus

Question 23

*cocaine’s CV effects

Answer 23

tachycardia, hypertension, ventricular arrhythmias, vasoconstriction

Question 24

which more commonly causes allergies: amides or esters?

Answer 24

esters (procaine, benzocaine)

Question 25

lidocaine muscle toxicity

Answer 25

myotoxic when directly injected into muscle; depresses coagulation

Question 26

treatment for toxicity of LA

Answer 26

IV intralipids given early!

Question 27

*the pH at which the fraction of ionized and non-ionized fractions are equal

Answer 27

pKa