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91 Cards in this Set
- Front
- Back
What is general anesthesia?
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a drug-induced LOC in which pts are not arousable, even by painful stimulation
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Explain the steps in the spectrum of consciousness.
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awake --> minimal sedation (anxiolysis) --> moderate sedation --> deep sedation --> GA
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What are the major stages in GA?
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Premedication
Induction Maintenance Emergence |
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What is emergence?
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reversal of neuromuscular blockade, anti-emetic, analgesia
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What is important in the maintenance phase of GA?
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sedative/hypnotic, analgesia, autonomic stabalization
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What is important in the induction phase of GA?
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sedative/hypnotic, analgesia, muscle relaxation
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What is important in the premedication phase of GA?
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anxiolysis, antisalagogue, autonomic stabilization, analgesia
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What is the mechanism of action of inhalation anesthetics?
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it is LARGELY unknown (but probably something to do w/ inhibition of glutamate receptors and increased activity of GABA receptors)
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What affects the pharmacokinetics of inhaled anesthetics?
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CO and ventilation rate
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What determines the clinical effect of inhaled anesthetics?
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partial pressure of volatile anesthetic at the CNS
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What are the major pharmacokinetic principles of inhaled anesthetics?
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Absorption/Uptake (from alveoli to systemic circ)
Distribution Metabolism/Biotransformation Excretion/Elimination from the lungs |
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What determines the transition from the vaporizer to tissue?
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Series of partial pressure gradients
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What is the key determinant of anesthetic uptake into the blood and distribution t/o the body?
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solubility
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__ agents have fast rise in alveolar concentration b/c they are not easily taken up by the blood
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insoluble (like nitrous)
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There is a __ relationship b/w blood solubility and rate of induction
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inverse
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T or F: Breathing and cardio systems are impaired in GA
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TRUE
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What is anxiolysis?
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taking the edge off
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Hyperventilation __ rate of anesthetic onset
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increases
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___ slows rate of anesthetic onset
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hypoventilation
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What are the 4 cornerstones of GA?
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LOC
Amnesia Analgesia Muscle relaxation |
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What are some classes of inhalational anesthetics?
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Ether, N2O, halogenated hydrocarbons
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Less soluble -->
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faster onset of action
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More soluble -->
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slower onset of action
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Anesthetics that depress ventilation __ the rate of rise of alveolar concentratoin and create a negative feedback loop.
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decrease
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Higher CO/PBF --> __ alveolar partial pressure
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lowers
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__ relationship b/w CO/PBF and rate of induction
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inverse
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What are partition coefficients?
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the relative solubility of an anesthetic in air, blood, or tissue.
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Transfer from blood to tissue depends on __ and __ of gas in different tissues
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perfusion and solubility
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T or F: Areas w/ less blood flow have slower rate of rise of tissue gas concentration
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TRUE
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Which agent undergoes the greatest metabolism in the CYP P-450 system?
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halothane
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metabolism of halogenated anesthetics to free inorganic fluoride -->
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nephrotoxicity
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The majority of elimination occurs at the __
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alveolus
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Recovery from anesthesia depends on what?
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lowering the conc of anesthetic in brain tissue
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What is MAC?
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Minimum Alveolar Concentratoin of inhaled anesthetic that prevents movement in 50% of pts in response to a surgical stimulus
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T or F: MAC compares the potency of agents
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TRUE
The lower the MAC, the more potent the drug |
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T or F: MAC values are additive
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TRUE
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What is the most insoluble agent?
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Nitrous oxide
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T or F: All agents cause dose-dependent myocardial depression (decreased contractility)
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TRUE
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What is the classic breathing response to GA agents?
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Increased RR and Decreased TV
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Which agent stimulates the SNS (by catecholamine release)?
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Nitrous oxide
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Why do you avoid nitrous oxide in pts w/ air containing cavities?
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b/c it is 25 times more soluble than nitrogen in blood and moves into and expands these spaces
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Which agent inhibits B12 dependent enzymes?
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N2O
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Which agent is the most potent bronchodilator?
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halothane
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Which agent causes reflex tachycardia?
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isoflurane
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which agent irritates upper airway reflexes, but is a potent bronchodilator?
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isoflurane
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Which agent has a low solubility in blood and tissue and low blood/gas partition coefficient which makes it good for fast onset and recovery?
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desflurane
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Which agent is a pungent, potential airway irritant?
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desflurane
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Which agent is nonpungent and has rapid increase in alveolar concentration making it good for mask induction?
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sevoflurane
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What causes malignant hyperthermia?
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mutation in ryanodine receptor Ryr1 in skeletal muscle
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What is malignant hyperthermia?
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uncontrolled Ca release from skeletal muscle triggered by volatile anesthetics leading to sustained muscle contractions producing a hypermetabolic response
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What is the major inhibitory NT in the CNS?
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GABA
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What is Ketamine?
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NMDA receptor antagonist (subtype of the glutamate receptor)
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Which agent is a "dissociative" anesthetic?
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ketamine
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What is a dissociative anesthetic do?
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dissociates the thalamus from the limbic cortex
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What is ketamine used for?
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central stimulation of SNS cause CV stability, maintained ventilatoin, increased CBF, ICP, CMRO2
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What does etomidate do?
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depresses the RAS and mimics inhibitory effects of GABA
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What is a side effect of etomidate?
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myoclonus (disinhibits the extrapyramidal motor activity) and adrenocortical suppression
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T or F: Propofol has a rapid onset and recovery
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TRUE
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How does dexmedetomidine work?
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lipophylic alpha-methylol derivative w/ a high affinity for the alpha-2 receptor
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HTN w/ rapid administration --> which drug
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dexmedetomidine
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Which drug can cause hypotension and bradycardia during ongoing therapy?
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dexmedetomidine
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T or F: Neuromuscular blockade contributes to the depth of anesthesia
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FALSE
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What is NMJ blockade used for?
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facilitate tracheal intubation
improves surgical condition and surgical exposure prevents potential movement during critical surgical interventions DOES NOT CONTRIBUTE TO ANESTHESIA |
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__ are quaternary ammonium compounds w/ affinity for nicotinic ACh receptors due to positively charged N.
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neuromuscular blockers
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Which drug closely resembles ACh generateing muscle APs?
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succinylcholine
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What are the two classes of neuromuscular blockers?
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depolarizing and non-depolarizing
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What is an example of a depolarizing neuromuscular blocker?
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succinylcholine
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What are some non-depolarizing neuromuscular blockers?
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pancuronium, cisatracurium, vecuronium, rocuronium
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T or F: succinylcholine is metabolized by acetylcholinesterase.
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FALSE
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agonist or antagonist: succinylcholine
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ACh agonist
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How do non-depolarizing neuromuscular blockers work?
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bind ACh receptors but are incapable of opening ion channels <--> they are competitive antagonists
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How are depolarizing NMBs reversed?
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they diffuse from NMJ and are hydrolyzed in plasma and liver by pseudocholinesterase
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Which inhaled agent has a dose-dependent reduction of arterial blood pressure and direct myocardial depression?
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halothane
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what is a serious complication of halothane?
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hepatitis
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___ sensitizes the heart to the arrhythmogenic effects of epi
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halothane
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Which agent has minimal cardiac depression w/ mild beta-adrenergic stimulation?
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isoflurane
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Which drug gives elevation in HR, BP and catecholamine release with a rapid increase in concentration?
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desflurane
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Which agent directly dilates the cerebral vasculature leading to increased CBF and ICP?
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desflurane
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How do you treat malignant hyperthermia?
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Dantrolene Sodium and supportive care
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How are most GA agents administered?
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IV
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Which nonvolatiles agent may suppress adrenocortical function?
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etomidate
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Which nonvolatile agent can give myoclonus?
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etomidate
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Which nonvolatile agent is distributed in an oil-water immersion making it susceptible to bacterial growth? It also causes substantial pain on injection.
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propafol
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What is propafol approved for?
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moderate-deep sedation and GA (induction and maintenance)
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Which nonvolatile agent is a lipophilic alpha-methyol derivative with a high affinity for the alpha-2 receptor?
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dexmedetomidine
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How do you reverse nondepolarizing NMBs?
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cholinesterase inhibitors increase ACh at NMJ and compete with them.
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What are some anticholinesterase drugs?
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Neostigmine, Pyridostigmine, Physostigmine, Edrophonium
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Why do you give an anticholinergic when you give an anticholinesterase?
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to minimize the muscarinic effects and maximize the nicotinic effects
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What are some "antimuscarinics" (i.e. anticholinergics)?
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atropine, scopolamine, glycopyrolate
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Muscarinic -->
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sympathetic
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Nicotinic -->
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parasympathetic
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