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31 Cards in this Set
- Front
- Back
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Besides an anesthetic, what can lidocaine be used for?
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An anti-dysrhythmic drug
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What two anesthetic drugs are used in obstetrics? why?
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Bupivicaine and ropivacaine. Do not cause a motor block, but allow for sensory elimination
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Are locals irreversible or reversible?
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Reversible
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What is the goal of anesthetic research?
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To find a drug that blocks pain only
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How does a local anesthetic work?
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It decreases sodium permeability so a neuron never reaches it's threshold potential.
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What channel do locals block?
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Sodium
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What are the three states of a sodium channel?
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Rested, activated, inactivated
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Which sodium channel state has low affinity for locals?
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Rested
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What must a neuron do before it is completely neutralized? Why is this clinically relevant?
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It must fire, so the channels will cycle between the three cycles. The physician/dentist must stimulate the nerves to numb them.
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What is the general structure of locals?
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Two groups (lipophilic and hydrophilic) seperated by a chain.
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How do you know if a drug is an amide or an ester?
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Any drug with an i is an amide
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How is it that a local can dissolve in water, but also cross the lipidy myelin.
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Ionization. Recall that they are aphiphatic.
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How is pKa important in drug onset time?
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The closer the pKa is to physiological pH, the more drug will be in the base form and thus will have a faster onset time.
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What two types of people do you not want to use locals on?
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Aseptic or acidotic in the area you are working in
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How is the hydrophobicity coefficient related to drug potency.
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The higher the coefficient, the more potent.
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What are the two main things that affect the duration of action of locals?
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1. Protein binding...lasts longer with high binding
2. Vasodialation (diffusion)...lasts longer with less vasodialation |
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What is differential blockade? What are two examples?
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The ability of a local to block sensory but not motor. Bupivacaine and ropivicaine for OB.
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What is the most important in the effective use of a local anesthetic.
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Location
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What is the most dangerous local block? Intermediate? low?
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intercostal, epidural, peripheral
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Is the toxic dose higher or lower with epinephrine use?
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Higher...it takes more to be toxic because it is harder to get into the circulation.
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Where are amides metabolized?
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In the liver. There is an i in amide and liver
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Which are more toxic, amides or esters?
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Amides
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When are amides contraindicated?
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Liver disease
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What compound are the metabolites of esters similar to? Why is this a problem?
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PABA, people can be allergic to it.
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What is Cm?
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Minimum concentration
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Is the Cm higher or lower in a stimulated nerve?
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Lower...harder to block a nerve that is resting
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Is the Cm higher or lower at a low pH?
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Higher
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Is the Cm higher or lower for a myelinated nerve?
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Lower
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Is it harder to block bigger or smaller nerves?
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Generally, the bigger the fiber is, the easier it is to block. Really hard to block burny pain.
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What is the order of events in local use toxicity?
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CNS excitiation then depression, then CV depression
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Why are locals cardiotoxic?
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Because they block sodium channels.
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