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VW Local Anesthetics
IS-B2-Local Anesthetics
| Question | Answer |
|---|---|
| Local anesthetics work by blocking what? | Na+ channels from depolarizing, Ca++ from entering cell and causing synaptic vesicle docking and release of NT's/glutamate into synaptic cleft to promote conduction. |
| Muscarinic, Dopaminic and Adrenergic 2 agonists do what? | inhibit Adenyl Cyclase (MAD 2's) |
| What is the MOA for A2 agonists? | prevents phosphorylation of Ca++ channels which prevents Ca++ from entering cell and causing synaptic vesicle docking and release. |
| Describe the basis for referred pain. | Neurotransmitters from dense core vesicles released during neuron conduction can drift away from synaptic cleft. |
| True or False - all local anesthetics are tertiary amines. | TRUE |
| Why would a low pH prevent the action of a local anesthetic? | A low pH environment means that there are free ions nearby and that means the local anesthetic will get charged. It can't cross the membrane into the neuron if it's charged, and it can't work if it's stuck outside neuron. |
| True or Fales - Amides have a shorter T1/2 than Esters. | False - Esters have a shorter T1/2 |
| True or False - Amides rely on Cytochrome P450 to be broken down. | True |
| True or False - a local anesthetic is generally more effective at low extracellular pH? | False - low pH = high ion concentration |
| True or False - charged form of the local anesthetic is actively transported across the lipid bilayer? | False - must be uncharged to get across |
| True or false - local anesthetics are weak acids with very low pKa's? | False - they are weak bases |
| True or false - protonated and unprotonated forms are required for local anesthesia? | True - unprotonated outside, protonated in |
| True or false - systemic circulation is required to produce the effects of local anesthetics? | False - systemic circulation can be bad |
| What is the benefit of adding Epinephrine when administering local anesthetics? | epinephrine prevents the vascularization from carrying away the anesthetic by causing vasoconstriction that reduces systemic absorption. |
| This drug has an A2 receptor presynpatic activation that inhibits glutamate or substance P, which is an added benefit for local anesthetics. | Epinephrine |
| How are esters metabolized? | Cholinesterase in the blood |
| Do esters or amides occasionally produce allergic metabolites? | Esters |
| How are amides metabolized? | Cyt P450 - liver |
| Regarding block selectivity, is it easier to block a myelinated or unmyelinated nerve? | Myelinated - impulse usually jumps from myelinated spot to spot, so turning off a few early Na+ channels stops the whole show. |
| Regarding block selectivity, is it easier to block a larger or smaller diameter nerve? | Smaller is easier - more anesthetic necessary to block a larger neuron. |
| Regarding the location of the fibers in a neuron, which are most outside, which in the outer core and which in the inner core? | Motor outside, proximal sensory outer core, distal sensory inner core (protected having to travel farthest) |
| True or false - C fibers fire rapidly? | TRUE |
| True or false - C fibers are most easily blocked. Why? | True - small diameter |
| True or false - T/C seizures are a result of systemic toxicity of local anesthetics? | True - unopposed excitatory activity due to inhibition of GABA tone |
| Why would you want a patient to hyperventilate if they are having seizures due to local anesthetic systemic absorption? | increase blood pH, decrease local anesthetic movement into neurons. |
| Which local anesthetic is highly cardiotoxic? | Bupivacaine |
| Which local anesthetic is the only one that causes hypertension? | Cocaine |
| If you've got a toxic dose of prilocaine on board, how do you reverse it? | Methylene blue or Vitamin C |
| Which dosage is higher - to treat arrhythmia systemically, or to use as a local anesthesia? | Injected locally |
| Tetracaine, Lidocaine and Cocaine are used in which method - injection, IV or topical? | Topical - for vasoconstriction too |
| True or false - the local anesthetics work better with a low pKa? | True |
| Describe the difference between a spinal nerve block and an epidural nerve block. | Spinal Nerve Block - into CSF at level of T12, Epidural - Into Epidural space, outside spinal cord, injected at level you want to anesthetize. |
| Esters: Tetracaine, Cocaine, Procaine and Benzocaine. Which is the long, medium, short or surface acting drug? Which is the only one to block norepinephrine and cause vasoconstriction, hypertension, cerebral hemorrhage and arrhythmias? | Tetracaine - Long Cocaine - Medium - responsible for hypertension Procaine - Short Benzocaine - Surface |
| Are Bupivacaine, Ropivacaine, and Etidocaine the long or medium acting amides? | Long Acting |
| Which Amide can be metabolized to products which can cause methemoglobinemia and how do you reverse the effects? | Prilocaine - methylene blue |
Created by:
cherubicsiren
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