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Anes. Pharm I Test 3
IV Anesthetics
| Question | Answer |
|---|---|
| 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
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