Term
| Local Anesthetics are weak ________. They are ________ to a pH of ________. |
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Definition
*Bases
*Acidified
*4.4-6.4 |
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Term
| What are the three parts of a local anesthetic? |
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Definition
*Lipophilic portion (Benzene ring)
*Hydrophilic portion (tertiary amine)
*Hydrocarbon intermediate chain (Either an ester or amide) |
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Term
| What is the MOA of Local anesthetics? |
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Definition
*LAs bind to the Na+ channels in their inactive state, preventing the large influx of Na+ associated with membrane depolarization
*Need both ionized and unionized portion of the LA in order for it to work
*Nerve axon is where this takes place (Voltage gated Na+ channels are found here) |
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Term
| What is the order of fibers blocked? |
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Definition
*B-fibers (Preganglionic)
*C-fibers (Postganglionic)
*A delta (sharp pain)
*A gamma (Touch and pressure)
*A alpha (largest and fastest)
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Term
| What property of a LA determines potency? |
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Definition
*Lipid solubility
*Increased # of carbons increases potency |
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Term
| What property of a LA controls DOA? |
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Definition
*Protein binding
*Most important factor for DOA |
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Term
| What property of a LA determines Speed of onset? |
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Definition
*pKa
*The higher the pKa the slower the onset
*LA must be non ionized to cross the lipophilic nerve membrane. |
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Term
| What is the only exception to to the rule for speed of onset and pKa? |
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Definition
| *Chloroprocaine with a pKa of 9.1 |
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Term
| What influences absorption of a local anesthetic? |
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Definition
*Total dose
*Addition of vasoconstrictors
*Local protein binding
*Additional drug therapy
*Renal or hepatic disease
*Tissue perfusion
*Site of injection
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Term
| Rank injection sites from highest to lowest amount of vascular absorption of LA. |
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Definition
*IV>Tracheal>Intercostal>Caudal>Paracervical>Epidural>
brachial Plexus>Subarachnoid>Subcutaneous |
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Term
| What are potential side effects of LAs? |
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Definition
*Allergic reactions
*Systemic toxicity
Neurotoxicity
*Cardiac toxicity
*Cauda equina syndrome
*Anterior spinal artery syndrome
*Transient radicular irritation
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Term
| What are some signs and symptoms of CNS toxicity with LAs? |
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Definition
| *Numb tongue, lightheaded, visual, muscle twitching, unconsciousness, seizures, coma, respiratory arrest, death |
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Term
| What increases cardiac toxicity with LA use? |
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Definition
*Hypoxia
*Acidosis
*Pregnancy
*Hyperkalemia |
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Term
| What are some considerations for choosing an anesthetic agent? |
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Definition
*Duration of surgery
*Regional technique administered
*Skill of the anesthetist
*Potential for side effects
*Needs of the block |
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Term
| Why are greater than 2 sprays with a duration of 2 seconds contraindicated with topical anesthetics? |
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Definition
*risk of methemoglobinemia
*Treatment is 1-2mg/kg of Methlene Blue |
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Term
| What is the toxic dose of Cocaine? |
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Definition
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Term
| What is the toxic dose of Procaine (novocaine)? |
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Definition
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Term
| What is the toxic dose of tetracaine? |
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Definition
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Term
| What is the toxic dose of 2-Chloroprocaine (Nesacaine)? |
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Definition
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Term
What are the special properties of cocaine?
Doses? |
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Definition
*Only naturally occurring LA
*Vasoconstrictor
*Blocks reuptake of NE --> Euphoria
*Present for 24-36 hours
*only used as topical 4% solution |
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Term
| What are the special properties of tetracaine? |
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Definition
*Slower rate of hydrolysis than procaine
*Not used for epidurals (Profound motor/patchy sensory)
*Can be good for spinals for long cases |
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Term
| What are the special characteristics of Chloroprocaine? |
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Definition
*Halogenated procaine
*Fast onset 60 sec
*Short acting, fast hydrolysis
*Low placental transfer good for OB |
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Term
| What is the toxic dose of Dibucaine (Nupercaine)? |
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Definition
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Term
| What is the toxic dose of Lidocaine with and without Epi? |
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Definition
*With Epi: 7mg/kg
*Without: 4mg/kg |
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Term
| What is the max dose of Mepivacaine (Carbocaine)? |
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Definition
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Term
| What is the max dose of Bupivicaine (Marcaine, sensorcaine)? |
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Definition
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Term
| What is the max dose of etidocaine (Duranest)? |
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Definition
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Term
| What is the max dose of Prilocaine (Propitocaine, Citanest)? |
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Definition
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Term
| What is the max dose of Ropivacaine (Naropin)? |
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Definition
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Term
| What is the max dose of Levobupivicaine (Chirocaine)? |
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Definition
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Term
| What is the most toxic anesthetic and is more toxic than procaine? |
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Definition
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Term
| What is a normal, heterozygous, and homozygous dibucaine number? |
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Definition
*N= 75-80
*Hetero= 30-70
*Homo= <20 |
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Term
| What is the gold standard to which all other LAs are compared? |
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Definition
*Lidocaine
*Most popular related to its versitility |
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Term
| What is the active metabolite of lidocaine after it undergoes N-demethylation by CYP450? |
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Definition
*Monoethylglycinexylidide
*80% as effective as lidocaine |
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Term
| What is the duration of Lidocaine? How is this affected by coadministration of Epi? |
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Definition
*1-3 hours
*Increases DOA by 75-100% |
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Term
| What are doses of lidocaine for a T4 and T12 block? |
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Definition
*5'0"
-T12: 40mg
-T4: 60mg
*6'0"
-T12: 50mg
-T4: 80mg |
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Term
| What agent is knowns as psuedo-lidocaine and has a slower onset and slightly longer duration than lidocaine? |
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Definition
*Mepivacaine
*No vasodilator effects
*Good for axillary blocks
*Good alternative to lidocaine when addition of epi is contrainidicated |
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Term
| What is widely used in OB and is highly protein bound (95%) with little placental transfer? |
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Definition
*Bupivicaine
*Slow onset
*Epi dose not prolong the duration of action
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Term
| Why is bupivicaine so cardiotoxic? |
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Definition
| *Highly lipid soluble and dissociation from cardiac Na+ channels is slow. |
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Term
| What LA has a rapid onset with the longest 1/2 life of all LAs? |
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Definition
*Etidocaine
*Profound sensory and motor block
*Will not prolong duration
*Very cardiotoxic
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Term
| What causes seizures at lower concentrations than any other anesthetic? |
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Definition
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Term
| What is the least toxic amide LA but can cause Methemoglobinemia? |
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Definition
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Term
| What has similar properties to bupivicaine and was developed in response to bupivacaine's cardiotoxicity? |
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Definition
*Ropivacaine
*slightly better sensory, less motor than bupivicaine |
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