Local Anesthesia Flashcards
A group of drugs that can be used in regional anesthesia for their ability to block nerves and eliminate sensory and motor responses are _
Local anesthetics
What are the 2 classes of local anesthetics? How can you tell them apart based on their names?
Amides and esters
Amides will have an “I” before the “caine”
Where are amides metabolized? Where is tetracaine metabolized?
In the liver
By plasma esterases
What are 2 topically available ester local anesthetics?
Cocaine and benzocaine (OTC)
How is lipid solubility associated with potency of local anesthetics?
Increased potency with increasing hydrophobicity (requires smaller doses)
Local anesthetics are weak bases. This means they are easily _
Protonates and deprotonates at close to neutral pH
What is the mechanism by which local anesthetics mediate their actions?
They are administered, cross the membrane, become charged and the block sodium channels from the inside of the cell.
What ion movement is required to initiate the action potential? In what direction?
Inward flow of sodium
Relative to the axon, how is a drug like lidocaine administered? How much is needed?
Administer along the axon
Need to administer large volumes of the drug
How does an acidotic tissue, e.g. pH of 7.2, affect the amount of non-ionized local anesthetic? What is a clinical condition where this may be a consideration?
Decreased pH means less drug in non-ionized form
In cases of ischemia
What is a potential reason for anesthesia failure regarding local anesthetic? How can this be circumvented?
In acidotic tissue, not enough drug in uncharged form to cross the membrane and have effect
Can be circumvented by moving away from the acidotic tissue
For a theoretical local anesthetic, will majority of the drug be charged or uncharged at pH=6? pH=8?
pH=6 - most drug is in charged form
pH=8 - most drug is in uncharged form
True or false - a local anesthetic may be alkalinized to increase its effectiveness?
True
True or false - anesthesia failure due to acidotic tissue can generally be overcome with volume?
False
Seizures, trouble breathing, a lot of muscle activity and increased lactic acid build up are associated with _
Local anesthesia toxicity
What are the 2 nerve types associated with pain transmission? Which is more resistant to local anesthetic?
A-delta and C fibers
C-more resistant to blockade
True or false, local anesthetics block sensory, motor and autonomic nerves
True
A funny taste in mouth, ringing in ears, audio disturbances are all associated with _. Why can this easily happen?
Local anesthesia toxicity
Veins are closely situated with nerves
What drug can be used to blunt the plasma levels of a local anesthetic?
Epinephrine
What are 2 drug classes used to treat seizures associated with local anesthetic toxicity? What can be used to sequester local anesthetic in cases of cardio-toxicity?
Barbiturates and benzodiezapines for seizures
Intralipid to sequester lipid soluble anesthetic
Which of the 2 types of local anesthetics is most likely to cause an allergic reaction? What other substances may contribute to allergic reaction to local anesthetics?
Esters
Epinephrine and preservatives
What are 2 topical anesthesia preparations? Which is associated with methemaglobinemia?
Lidocaine Benzocaine (methemaglobinemia)
What drug is used for inflitration anesthesia to start IVs and minor surgeries? How is it administered?
Lidocaine
Administered IV and subQ
What is a technique used for administration of IV regional anesthesia to reduce toxicity by preventing drug escaping extremity?
Bier Block
How can you find the nerve that you want to anesthetize?
Use electrical stimulation to locate the nerve in question
e.g. sciatic or femoral nerve blockade
What is a major effect associated with topical cocaine?
Major vasoconstrictor
Myocardial ischemia and infarction, arrhythmias, seizures, hypertension, intracerebral hemorrhage are all associated with the use of _
Topical cocaine
What is ropivacaine? What is an advantage?
S-isomer of racemic ropivacaine mix
Less toxicity than racemic bupivacaine
What is a way to control the level at which an anesthetic may act within the spine?
Use an additive to increase baricity (e.g. 8.5% dextrose)
How does bupivacaine compare to lidocaine?
Bupivacaine more lipid soluble and more potent
