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Anes. Pharm I Test 3

IV Anesthetics

QuestionAnswer
What are the two ways in which an IV anesthetic drug can change the patient's level of consciousness? by depressing the reticular activating system either by enhancing the inhibition properties of GABA or by inhibiting the NMDA excitatory synapse
Which IV anesthetic agents are stable in aqueous solution, with chemical stability and IV fluid compatibility? Methohexital (Brevital), Etomidate, Fospropofol, Ketamine
Which IV anesthetic agent is antiemetic? propofol
Which IV anesthetic agent is analgesic? ketamine
Which IV anesthetic agents are amnestic? Ketamine, propofol, thiopental (pentathol), Methohexital (Brevital), Etomidate
Which IV anesthetic agents are anticonvulsant? ketamine, thiopental (pentothal)
Which IV anesthetic agents have a rapid and predictable recovery? propofol, etomidate
Which IV anesthetic agents have a rapid onset without unwanted movement or unpredictable CV or CNS side effects? thiopental (pentathol)
Which IV anesthetics can be considered emetic? etomidate (highly), thiopental (pentathol), methohexital (brevital)
Which IV anesthetic agents are contraindicated in patients with porphyria? thiopental (pentothal), methohexital (brevital); etomidate is suggested to NOT be used either but ketamine is OK.
Which IV anesthetic agents do not cause pain on injection? thiopental (pentothal), methohexital (brevital), ketamine
Which IV anesthetic agents are rapidly metabolized to inactive substances with minimal accumulation? etomidate, propofol
Which IV anesthetic agents is considered to be "dial-able"? propofol
Which IV anesthetic agents decrease CMRO2 proportional to the decrease in cerebral blood flow with no increase in ICP? thiopental (pentathol), methohexital (brevital), etomidate
Which IV anesthetic agents does not cause a hangover effect? propofol
In can of an emergent OB delivery situation, which IV anesthetic is a good option to have close by? Why? Ketamine; no teratogenic effects, still depresses neonate but not to degree of pentathol; rapid onset
An IV anesthetic drug begins to lose its effect is it due to elimination half time or redistribution half time? redistribution half time
The primary mechanism for terminating the central effect of IV induction agents is their ________ from the central, highly perfused compartment (blood, brain) to the larger and less-well perfused "peripheral" compartments (skeletal muscles). redistribution
Large or repeated doses of lipid soluble barbiturates produce a cumulative effect because of what? the storage capacity of fat
Which IV anesthetic drug can basically achieve an isoelectric EEG? thiopental (pentathol)
Rank etomidate, pentothal and propofol in terms of best to worst cardiac profile. etomidate > pentathol > propofol (the worst, anticipate drop in BP)
Which IV anesthetic drug is the best choice for trauma patients, a.k.a. the guns and knife club? ketamine
Despite the fact that ketamine is a direct myocardial depressant, it is still the best choice for hypovolemic trauma patients. Why? the sympathetic stimulation that is causes enhances catecholamine effects, canceling out the myocardial depressant effect; NOT a good choice for people with exhausted catecholamine stores (drug abuse crisis, sepsis)
Though thiopental (pentathol) causes a transient decrease in blood pressure, this can be masked by another effect of this drug. What is it? What patients would experience an exaggerated drop in blood pressure? pentathol causes an accompanying increase in HR due to carotid sinus baroreceptor stimulation; this does not occur in patients with a beta-blockade or hypovolemia - so they will experience a greater drop in BP
5 mg/kg dose of pentathol causes a __________ decrease in BP, but a ________ increase in HR. 10 - 20 mmHg drop in BP; 15 - 20 beat increase in HR
What is the mechanism of action of pentathol? increases the duration of GABA; mimics GABA at its receptor; activates glutamate, adenosine, and nicotinic ACh receptors
Pentathol causes vasodilation of cutaneous and skeletal muscle blood vessels, which can lead to what? heat loss and a reduction in temperature
Does slowing the rate of administration of pentathol change the decrease in BP or HR asserted with possible histamine release? NO.
Overall, pentathol's CV effects are considered __________ minimal
What effects does pentathol have on the respiratory system? decreases sensitivity of medullary ventilatory center to stimulation from CO2; apnea more likely when used in combo with other depressant drugs; reflexes remain intact with apnea, but when respirations return = small TV, slow RR
To what degree does pentathol decrease CMRO2? by 55%
In terms of CPP, why would you be cautious in giving large doses of pentathol to a hypovolemic patient? It could decease CPP below adequate level since CPP = MAP - ICP
What is the onset and duration of thiopental? onset: 30 seconds; duration: 5 - 10 minutes
If thiopental is mixed with a NMB, catecholamine, opioids, or LR fluids in the IV tubing, what will happen? a precipitate akin to concrete will form in the tubing!
The metabolism of methohexital (brevital) occurs three to four times faster than that of thiopental. Why? Decreased lipid solubility of methohexital allows more of the drug to stay in the plasma (smaller volume of distribution).
Compare and contrast the distribution 1/2 times and elimination 1/2 times of thiopental and methohexital. distribution 1/2 times are about the same (2-4 min vs. 5-6 min) but the methohexital's elimination 1/2 time is much shorter (10-12 hrs vs. 2-5 hrs)
What is the advantage of methohexital? more rapid recovery
What are some disadvantages of methohexital? more excitatory activity, myoclonus, hiccoughs
Methohexital is ___ times more potent than thiopental due to higher percentage nonionized at blood pH of 7.4 2.5 x more potent
Where was methohexital used the most? in cataract procedures before the MD did the retrobulbar block
What is the dose of thiopental? 3 - 5 mg/kg IV
What is the dose of methohexital? 1 - 2 mg/kg IV
What is the rectal dose of methohexital? 25 mg/kg
What is the sedation dose of methohexital? 0.2 - 0.4 mg/kg IV
What is the onset and duration of methohexital? onset: 30 seconds IV; < 5 min rectal; duration: 5 - 10 minutes IV, 30 - 90 minutes rectal
Which IV anesthetic is chemically unrelated to any of the other IV anesthetic drug? etomidate
What is unique about the chemical structure of etomidate and what is its significance? carboxylated imidazole-containing compound; so it is water-soluble at an acidic pH and lipid soluble at a physiologic pH
What is etomidate's mechanism of action? mimics the inhibitory effects of GABA by increasing the receptor's affinity to GABA and thus depressing the reticular activating system
Etomidate causes myoclonus in what percent of patients? 30 - 60%
What makes etomidate a great choice for patients with cardiac issues? minimal changes in HR, stroke volume, CO; only slight decrease in MAP; no histamine release; no decrease in renal blood flow; depresses myocardium less than thiopental
How does etomidate affect the patient's respiratory system? dereases TV but increases RR; apnea doesn't always occur; less effect on respiration than barbiturates
How much does etomidate decrease CMRO2? by 35 - 45%
The myoclonic activity of etomidate can be minimized with preop ________ administration opioid
How does etomidate cause adrenocortical suppression? by inhibiting the conversion of cholesterol to cortisol, essentially decreasing steroid production
What patient populations probably should not receive etomidate due to its adrenocortical suppression and why? septic and bleeding patients, because they need to have a appropriate stress response in order to survive
How is etomidate metabolized? by hepatic microsomal enzymes and plasma esterases (clearance is 5x faster than thiopental)
What is the dose of etomidate? 0.3 mg/kg IV
What is the onset and duration of etomidate? onset: 14 - 45 seconds; duration: 3 - 12 minutes
Which IV sedative drug is an alpha 2 agonist? dexmedetomidine (precedex)
Dexmedetomidine is ___ times more selective for alpha 2 receptors than clonidine 8 x more selective
What is dexmedetomidine's mechanism of action? decreased cAMP, which results in altered ion channel activity; hyperpolarization from K+ efflux suppresses neuronal firing and decreased Ca++ release means decreased NE release
Is dexmedetomidine approved for general anesthesia? No; but it is approved for MAC sedation and 24 hour infusions in ICU
Dexmedetomidine decreases MAC by what percentage? by 90%
What are the effects of dexmedetomidine? some analgesia, augments opioid effect, limited amnesia, reduction in shivering, antisialogogue, sympatholytic
Why should you never give dexmedetomidine as a bolus dose? hypertension can occur
Dexmedetomidine causes less delirium than ____________ and does not cause delusions like _________ benzodiazepines; ketamine
What is the context sensitive half time of dexmedetomidine after an hour? After more than 6 hours? after 1 hour: 25 - 120 minutes; after > 6 hours: 87 - 250 minutes
In terms of excitatory effects, which 2 IV anesthetic drugs are the worst offenders? methohexidine and etomidate
Which drug can offset the respiratory depressant effect of propofol if given in conjunction with propofol? ketamine
In terms of respiratory depression rank these 4 IV anesthetics from least to worst: etomidate, pentothal, propofol, ketamine. ketamine < etomidate < pentothal < propofol
What is the pH of propofol? 7.0 - 8.5 (large variation due to pH adjusters and stabilizers)
What is propofol classified as? a sedative-hypnotic
What is the 1/2 time for blood-brain equilibration? 1 - 3 minutes
What is the mechanism of action of propofol? inhibits neuronal activity at the post-synaptic GABA receptors by increasing chloride conductance
What is the half life of propofol? 2 - 8 minutes
What is the rate of clearance of propofol? 30 - 60 ml/kg/min
How does renal failure affect the metabolism of propofol? Only affects elimination of metabolites; clearance of parent drug is done by the liver
How does propofol affect the CV system? decreases arterial BP, decreases SVR
What are the respiratory affects of propofol? profound ventilatory depressant - apnea after induction; inhibits hypoxic drive; depresses upper airway reflexes
Which IV anesthetic is the best choice for placement of an LMA? Why? propofol; depresses upper airway reflexes so it prevents laryngospasm
Does propofol cause histamine release? yes; however, it is NOT contraindicated in asthmatics unless they are exhibiting signs of bronchospasm and wheezing
In terms of histamine release, where does propofol rank when compared with barbiturates and ketamine? propofol releases less histamine than barbiturate and ketamine
What is the logic behind giving large doses of propofol to treat status asthmatics? the strength of the dose will overcome the bronchospasm (despite the fact that propofol causes histamine release...)
Propofol reduces ICP and cerebral blood flow. Explain how this effect can be dangerous in patients with elevated ICP. A significant drop in BP coupled with a drop in ICP can decrease CPP to a point that could cause brain damage
True or False: propofol is associated with both convulsant and anti-convulsant effects True (avoid in patients with seizure disorders? despite fact that it can break status epileptics)
True or False: propofol may worsen parkinsonism true
What is the time frame in which administration of propofol should be completed, ampules should be used, etc...? within 6 hours
What is the general induction dose of propofol? 1 - 2.5 mg/kg
What is the MAC dose of propofol? 0.5 mg/kg
How do dosages of propofol compare to fospropofol? 2.5 mg/kg of propofol = 12.5 mg/kg of fospropofol
What are fospropofol's metabolites? propofol, formaldehyde, and phosphates
What is the mechanism of action of ketamine? binds non-competitively to N-methyl-D-aspartate (NMDA) receptors; also exerts some effect on opioid receptors
What is the occurrence of emergence delirium with ketamine without pre-op versed? 5 - 30%
Ketamine is partially antagonized by ___________ drugs because it binds to muscarinic receptors anticholinesterase
What two drugs are used as pretreatment for ketamine and why? Versed - prevents delirium; Robinul - prevents sympathomymetic action & spit
What is the name of ketamine's active metabolite and what is it presumed to be responsible for? Norketamine: attributed as analgesic component
Ketamine is metabolized by cytochrome P450 system. Since it is inducible, what patient populations may require larger doses? alcoholics, drug abusers, chronic smokers
True or false: ketamine depresses upper airway reflexes. false! airway reflexes are maintained
Intense analgesia can be accomplished with subasesthetic doses of ketamine. What is this dose range? 0.2 - 0.5 mg/kg IV
What are the onset times for IV and IM doses of ketamine? 30 - 60 seconds IV; 2 - 4 minutes IM
Ketamine is a myocardial depressant; however, it is a good choice for hypovolemic patients. Why? masking of myocardial depression through direct CNS stimulation which increases HR, BP, CO in patients with normal catecholamine levels
What patient populations would experience the myocardial depressant effects of ketamine? patients with sympathetic block (spinal, spinal cord injury); patients with low catecholamines (shock, drug abuse crisis)
Does ketamine stimulate malignant hyperthermia? No
How does ketamine increase ICP? potent vasodilator (although less increase with mechanically ventilated patient)
True or false: ketamine altars the body's response to increasing CO2. False! maintains CO2 drive for respirations
Does ketamine provoke histamine release? no
When used with aminophylline drugs, ketamine can cause what? seizures
Ketamine given with non depolarizing NMB on board enhances or inhibits the blockade? enhances
Created by: Mary Beth