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47 Cards in this Set

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Give the order of nerve suseptibility to block for myelinated somatic A fibers
Small size >>> large: delta>gamma> beta> alpha
Given that the order of block is from delta>gamma>beta>alpha for somatic A fibers, give the corresponding block associated with somatic A fibers.
delta:fast pain, temp, touch> gamma:muscle tone > beta: touch, pressure > alpha: motor proprioception, reflexes
Which fibers are most sensitive to block? Place in order
C > B > A
which are blocked first myelinated or non-myelinated nerves?
which Na channel can bind anesthetic better, closed (resting), open, or open/inactive (desensitized)?
open/inactive (desensitized)
What effect does the binding of anesthetic have on desensitized Na channels?
It stabilizes it in the desensitized state
Which nerves in large nerve trunks are blocked first?
the outer nerves are blocked first
What form of an anesthetic can pass through the cell membrane?
uncharge, thus pH and the drug pKa determine the relative amounts of drug on either side of the membrane
When is the anesthetic effect of a drug terminated?
when the drug is removed from the tissues
What effect do vasoconstrictors, such as epinephrine, have on anesthetic action?
they prolong action through reduced loss to the blood
Once an anesthetic is in the blood what 2 things determine its distribution in different tissues?
blood flow, hydrophobicity of the drug and tissues
What effect do plasma esterase have on ester anesthetics such as procaine and tetracaine?
produce inactive products, which are generally non-toxic, but can produce allergic responses
what effect do hepatic enzymes have on amides, such as lidocaine and bupivacaine?
Produces some active and/or toxic intermediates
How can high plasma levels of anesthetic be produced? (3 ways)
intravascular injection, repetitive admin, and impaired metabolism
What are two toxicities related to high anesthetic plasma levels?
CNS and cardio
Which toxicity correlates with anesthetic potency, CNS or cardiac?
CNS - potency is related to lipophilic properties, thus since the CNS is more lipophilic it will receive more drug --> more toxicity
which anesthetic is most cardiotoxic?
which occurs at lower plasma levels of anesthetic, CNS or cardiac?
Which produces more allergic responses esters or amides anesthetics?
ester anesthetics
What are the symptoms of esters?
red and itchy eczematoid dermatitis or vesiculation
What exactly causes the allergic rxn in ester use?
the metabolite, PABA, which is also found in sunscreen
How does a hydrophobic anesthetic effect the following? 1. onset... 2. potency... 3. tissue binding... 4. rate of metabolism
1. Faster onset of block (with partitioning to the site of action), 2. greater potency (with greater toxicity), 3. inceased tissue binding, 4. decreased rate of metabolism
What is the pKa of a hydrophilic anesthetic?
between 8 and 9
What is the state of most hydrophilic anesthetics at physiologic pH?
How are hydrophilic anesthetic drugs supplied?
in a acid pH so they will be neutral
Local diffusion, Local pH, Tissue binding, local blood flow, and cardiac output, but NOT enzymatic half-life... all effect __________ of local anesthetic action.
Local diffusion, Local pH, Tissue binding, local blood flow, and cardiac output, but NOT enzymatic half-life... all effect DURATION of local anesthetic action.

What two things are associated with the function of total body clearance of anesthetics?
liver and blood flow
what is the formula for determining charged and uncharged form of anesthetics?
log (cationic form/uncharged) = pKa -pH.. Thus a lower pKa with respect to higher pH will be neutral and able to cross the membrane... since most locals are weak bases, most of the drug will be in the form of a cation and not cross the membrane.


a negative number will produce more charged molecules = less available to cross the membrane... so infected tissue is less accessible to locals.
What helps trap drug in cells?
carbonate anhydrase (CO2 + H2O)
What effect does a thicker myelin sheath have?
greater nodal distance --> faster
which are blocked faster, non-myelinated C fibers or mylinated A fibers?
non-myelinated C fibers
Which types of nerves are more sensitive to block, fast or slow firing frequency?
Fast > slow (small>large, mylinated>non-myelinated, outer>inner)
What effect does epinephrine have on anesthetics for the following? Duration, toxicity, extremeties
epinephrine effects on… duration: increase, toxicity: decreases systemically, extremities: not in distal (vasoconstriction)
What effect does calcium have on anesthetics for the efficacy?
calcium decreases anesthetic efficacy
What effect does hyperkalemia have on anesthetics for the effect?
hyperkalemia increases anesthetic effect
What effect does Low CO2 have on anesthetics for clearance?
low CO2 produces decreased clearance of anesthetics
What effect does infection have on anesthetics for tissue pH?
lower pH --> see Henderson-hasselblach equation
What drugs are used for anesthetic: tropical?
benzocaine, tetracaine (systemic abs)
What drugs are used for anesthetic: infiltration?
procaine, lidocaine, bupivicaine, + epi ( at site, nerve ending)
What drugs are used for anesthetic: field block?
procaine, lidocaine, bupivicaine + epi (proximal nerve - less drug)
What drugs are used for anesthetic: Nerve?
procaine, lidocaine, bupivicaine, + epi (large bundle, damage if injected into the nerve)
What drugs are used for anesthetic: spinal?
tetracaine + lidocaine or bupivicaine (below L2… sympathetic > parasympathetic = hypotention… not very safe
What drugs are used for anesthetic: epidural?
lidocaine, bupivicaine (nerve roots, limited pH buffer)
Name the 3 Locals that are ester metabolized. Name the 2 amine metabolized Locals
Esters: procaine, tetracaine, benzocaine… Amine: Bupivicaine, lidocaine
Which local is most CNS toxic?
Which 2 drugs fall into these catagories: 1.Rapid onset/short acting… 2. Rapid onset/long acting.
1.Rapid onset/short acting: Benzocaine… 2. Rapid onset/long acting: Bupivicaine.
(1) Which 2 drugs fit into the following: 1. Short acting Local… 2. Intermediate acting Local... (2) what are the two short onset long long acting local anesthetics? why?
(1) 1. Short acting Local: Procaine… 2. Intermediate acting Local: Tetracaine... (2) lidocaine and Bupivicaine, because the are metabolized by liver enzymes.