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Pharm; Kaplan Section IV - CNS
Ch4 - Anesthesia
15
Accounting
Pre-School
04/08/2013

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Cards

Term
What are the two numbers that matter in inhaled anesthetics?
Definition
-MAC (minimal alveolar anesthetic concentration); basically ED50, but as a percentage
-Has to do with lipid solubility

-Blood-Gas ratio; is actually the bound/free gas ratio
-Lower values mean faster onset & recovery
-Has to do with blood solubility
Term
Give the major inhaled anesthetics?
Definition
-Nitrous oxide; MAC = 104%, B-GR = 0.5 (fast, but weak)
-Spontaneous abortion, diffusional hypoxia, no metabolism

Halothane & "-furanes "; MAC = 0.8%, B-GR = 2.3 (slow, but very strong)
-Malignant hyperthermia, liver damage, arrhythmias (from catecholamine sensitization)
Term
List the intravenous anesthetics?
Definition
-Thiopental (a barbiturate)
-Midazolam (a benzodiazepine)
-Propofol
-Fentanyl (an opiate)
-Ketamine

-See 151 for memory tools and specific info
Term
What is the mechanism of action of local anesthetics?
Definition
1. Non-ionized form goes into nerve terminal (RNH2)
-Usually inject with basic solution to help this (carbonated)

2. Ionized form inside cell is the active form
-Slightly acidic in cells

3. Binds to inactivated sodium channel and blocks it
Term
What are the two kinds of local anesthetics?
Definition
-Esters; procaine, cocaine, benzocaine (all have one "i")
-Amides; lidocaine, bupivacaine, mepivacaine (two "i"s)

-All of them have "-caine"
Term
What nerve types do local anesthetics effect more?
Definition
-Lower diameter fibers more (easier to enter)
-Dull pain is unmyelinated C fibers
-Sharp pain is lightly myelinated A-delta fibers
Term
What do we administer with local anesthetics? What drug do we not need this for?
Definition
-α1 agonist are given to vasoconstrictor prolongation of effect and avoidance of toxicity from going systemic

-Otherwise would be neurotoxic and cardiotoxic

-Cocaine inhibits NE uptake, and so indirectly stimulates α1 receptors without need of coadministration of α1 agonist
-Used as topical gel
Term
What about allergies and local anesthetics?
Definition
-They are metabolized to PABA, which commonly causes allergic reactions in skin (para amino benzoic acid)

-Side note; sulfonamides are an antimicrobial class of drugs that also give PABA and have sulfur (big for allergies)
Term
What are some naturally occurring toxins that act like local anesthetics?
Definition
-**Tetrodotoxin; from puffer fish (Fugu fish)
-Saxitoxin; from red tide algae
-Ciguatoxin; exotic fish
-Batrachotoxin; frogs

-All of them act on the voltage dependent Na+ channels
Term
Where does ACh usually bind on skeletal muscle receptors? How many blockers to shut them off?
Definition
-Nm receptors bind two ACh at two **α subunits in order to be activated?
-We only need one blocker per receptor, however
Term
What are the two kinds of muscle relaxants? Antidote?
Definition
-Nondepolarizing (competitive); "-curium" family
-Can reverse with AChE inhibitors-->*neostigmine

-Depolarizing (noncompetitive); succinylcholine
Term
What are the two major nondepolarizing skeletal muscle relaxants and attributes?
Definition
Atracurium
-*Safe for liver and kidney because it is not metabolized
-Spontaneously becomes *laudanosine, which may cause *seizures (Hoffman degradation)

Mivacurium
-Metabolized by an **esterase (fast & slow metabolizers)
-Usually *short duration, but not if slow metabolizer
Term
What is the depolarizing muscle relaxant and how does it act? Cautions (3)?
Definition
-Succinylcholine is a nonreversible agonist that essentially puts them into cholinergic crisis, eventually causing *flaccid paralysis
-No antidote, but quickly metabolized by pseudocholinESTERASE*

-Have to worry about *slow metabolizers
-Hyperkalemia; lengthens hyperpolarization
-Malignant hyperthermia (from extreme muscle rigidity)
Term
What does extreme muscle rigidity cause? Who is at risk? How do we treat? What are three drug types that can cause it?
Definition
-Causes acidosis and hyperthermia (just like exercise)-->SANS response-->inc. HR/arrhythmia & BP [called **malignant hyperthermia**]
-**Ryanodine receptor mutations are usually seen
-**Dantrolene to treat (Dan needs to relax about Ryan); blocks Ca++ release for sarcoplasmic reticulum

1. Inhaled anesthetics
2. Skeletal muscle relaxants
3. Antipsychotics (in neuroleptic malignant syndrome)
Term
What are two centrally acting muscle relaxants and what do they bind? Used for?
Definition
-Benzodiazepines (binds GABA-A receptors)
-Baclofen (binds GABA-B receptors)
-Used for spasticity
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