Term
| Name the two commonly used local anesthetics. |
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Definition
-amides (Lidocaine)
-esters (Procaine) |
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Term
| Mechanism of action of local anesthetics: |
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Definition
-prevent neuronal depolarization
-block the function of Na channels (physically plug; alter conformation "Frequency dependent blockade") |
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Term
| Local anesthetics bind to NA channels when channel is_________________ conformational state and stabilizes the channel in this conformation. |
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Definition
| -inactivated-closed (however, LAs gain access to Na channel when channel is in activated-open state) |
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Term
| True or False: Myelinated nerve fibers are more sensitive to LAs than non-myelinated fibers. |
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Definition
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Term
| Why are LAs poorly absorbed through skin? |
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Definition
| Because LAs are poorly water soluble |
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Term
| LAs are marked primarily as water soluble hydrochloride salts. List other formulations: |
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Definition
-continuous release path
-liposomal encapsulation
-creams, gels, sprays
-EMLA cream |
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Term
| Remember: Local anesthetics act locally so ______________ signals the end of their action. |
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Definition
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Term
| Pharmacokinetics-absorption of LAs |
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Definition
1. injection site-more vascular site: faster absorption and a higher peak of blood concentration
2. drug-tissue interaction-more potent, more lipid soluble, lower blood concentration
3. addition of vasoactive agent (epi)-vasoconstriction: less aborption, longer duration
4. Dose-greater dose: higher local concentration, then higher peak blood concentration |
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Term
| Pharmacokinetics-Metabolism (Esters) |
|
Definition
-pseudocholinesterase
-rapid (minutes)
-PABA (allergic rxn) |
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Term
| Pharmacokinetics-Metabolism (Amides) |
|
Definition
-hepatic cytochrome P450
-slower (lidocaine t1/2-1.5 hrs, Bupivacaine t 1/2-3.5 hours
-first pass pulmonary uptake
-prilocain-> ortho-toluidine (methemoglobinemia) |
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Term
| Lidocaine vs. Mepivacaine vs. Bupivacaine |
|
Definition
1. lidocaine-amide LA; rapid onsent, short duration (1-2 hours)
2. mepivacaine-amide; rapid onset (5-10 min); slightly longer duration (2-3 hours); used primarily in equine for lameness evaluation b/c it produces less inflammatory rxn
3. Bupivacaine-amide; slower onset (10-30 min), long duration of action (3-4 hours) |
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Term
| Which of the following LAs would likely have the slowest absorption, all else being equal? |
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Definition
|
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Term
|
Definition
1. Neurotoxicity (lidocaine)
2. CV toxicity (bupivacaine)
3. Allergic reactions (malignant arrhythmias)
4. Methemaglobinemia |
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Term
| Cetocaine spray is not recommended in cats b/c it can cause the following problems: |
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Definition
|
|
Term
|
Definition
-sole anesthetics
-adjuncts to general anesthesia
-diagnostic exams |
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|
Term
|
Definition
-absorb across mucous membranes (corneal, laryngeal)
-generally poorly absorbed by intact skin-exceptions: EMLA Cream, Lidoderm Patch |
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Term
|
Definition
-infiltrate SQ w/ LA around/under surgical site (small lumps/bumps; small lacerations)
-ring blocks
-inverted L block
-watch total dose! |
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Term
|
Definition
-infiltrate LA adjacent to peripheral nerve
-block area innervated by that nerve (know your anatomy!)
-large number of blocks available
-dental blocks
-intercostal nerve blocks
-proximal/distal paravertebral blocks
-limb blocks (equine lameness)
-"carpal blocks" |
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Term
| Intravenous regional block. |
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Definition
-"Bier Block"
-useful for lesions on distal extremities: place IV catheter, place tourniquet, inject lidocaine, block is gone shortly after removal of torniquet, time limited by tourniquet |
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Term
|
Definition
-epidural
-intrathecal
-brachial plexus
-nerve stimulation
-ultrasound-guided |
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Term
|
Definition
-CRI's (lidocaine, NOT IN CATS)
-intraarticular (analgesia-e.g. arthroscopy; controversial-chondrotoxic; lameness eval)
-intrapleural/peritoneal |
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