Katzung Chapter 26 Local Anesthetics

Local anesthesia

complete loss of sensation (analgesia) in a limited region of the body

Local anesthesia

Reversibly block impulse conduction along nerve axons and other excitable membranes

Used to block pain sensation

causes Muscle paralysis

Local anesthesia

lipophilic group, intermediate chain and a ionizable hydrophilic group (usually a tertiary amine) make up

more potent

Anesthetics that are more lipid soluble are generally

have a longer duration of action

Anesthetics that are more lipid soluble are generally

take longer to achieve their clinical effect

Anesthetics that are more lipid soluble are generally

higher blood levels

Highly perfused tissue the absorption is more rapid with

Highly perfused organs

brain, liver, kidney and heart are

vasoconstricting substances

_________Decrease systemic absorption and therefore reduce toxic effects

ii. Higher local concentration of drug from enhanced local uptake of the anesthetic

iii. Epinephrine

liver or plasma

Local anesthesia is converted in__________o more water-soluble metabolites

kidneys

Local anesthesia is excreted by the

Local anesthesia

________Blockade of voltage-gated sodium channels

Local anesthesia

_________Bind to intracellular portion of channels and block the channel in a time and voltage dependent manner

higher

Local anesthesia has a _____ affinity for activated and inactivated than resting channels

Prolongs inactivation and lengthens the refractory period

Bind to intracellular portion of channels causes

Local anesthesia

_______Elevated extracellular calcium antagonizes the effects of local anesthetics by increasing the membrane potential which favors the resting state of the sodium channel

Local anesthesia

________Elevated extracellular potassium depolarizes the membrane and favors the inactivated state of the sodium channel and therefore increases the effects of local anesthetics

a. Threshold for excitation increases

b. Impulse conduction slows

c. Rate of rise of the action potential declines

d. Action potential amplitude decreases

e. Ability to generate an action potential is abolished

effects after administration of higher and higher concentrations resulting in

sodium channels

Local anesthesia Recovery from drug-induced block is 10-1000 times slower than recovery of _______ from normal inactivation.

Biological toxins

act as sodium channel agonists and prevent inactivation of the channel

Marine toxins

bind to extracellular surface of sodium channels and block channel activity

faster rates of interaction

smaller more lipophilic agents have

More

lidocaine, and mepivacaine are ______water soluble

Less

tetracaine, ropivacaine and bupivacaine are _______water soluble

on small diameter

Local anesthesia has a Greater action _____nerve fibers

blocked

Myelinated nerves are ________ by local anesthesia before unmyelinated

more efficiently

High frequency fibers are blocked ________ (pain fibers vs. motor fibers)by Local anastesia

on the circumference

large mixed nerve trunks fibers _______ are affected first by local anastesia

1. Surface anesthesia
2. Topical injection
3. Injection near peripheral nerve endings and major nerve trunks
4. Epidural injections
5. Subarachnoid injections

these are Routes of administration

Carbon dioxide

can accelerate the onset

depress pacemaker activity, excitability and conduction

local anesthesia Cardiovascular effects

Transient pain of dysesthesia- can be quite severe

local anesthesia neurotoxic effects can cause

Benzocaine

______ has Pronounced lipophilicity

Benzocaine

_____ is a Topical anesthesia

Cocaine

______is a Intense vasoconstriction limits bleeding

Prilocaine

______ has Highest clearance and reduced risk of systemic toxicity

Ropivacaine

_______High-volume peripheral nerve blocks

2. Epidural infusions to control labor and postoperative pain

EMLA

____ is a Lidocaine and prilocaine topical mixture

EMLA

______Penetrates keratinized skin and produces numbness