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What is the mechanism of action of propofol?
How is propofol eliminated from the body?
Which formulation of propofol requires the presence of a preservative to prevent bacterial growth?
What is the context-sensitive half-time of propofol after infusions up to 8 hours duration?
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What contributes to the rapid clearance of propofol from the body?
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What is the mechanism of action of propofol?
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What is a potential side effect of propofol infusion syndrome?
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Which statement is true about propofol's pulmonary effects?
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What best describes the handling recommendation for propofol in the ICU?
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Which clinical feature is associated with propofol infusion syndrome?
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Which benzodiazepine has the highest hepatic clearance?
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What is the primary metabolite of midazolam?
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Which benzodiazepine has delayed elimination in the presence of drugs that inhibit cytochrome P450?
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In which patient population does midazolam exhibit prolonged elimination?
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Which benzodiazepine has the highest volume of distribution in obese patients?
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What is the recommended dose of propofol for induction of anesthesia in healthy adults?
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Which population requires a 25-50% reduction in propofol dose for anesthesia maintenance?
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What is the mechanism of propofol's antiemetic effect?
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What effect does propofol have on intraocular pressure (IOP)?
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What is the effect of propofol on systemic blood pressure?
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What effect does etomidate have on cerebral blood flow?
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How does etomidate affect cortisol and mineralocorticoid production?
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What is the primary impact of etomidate on cardiovascular function?
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What is the mechanism of action of flumazenil?
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What is the effect of etomidate on respiratory function?
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Which of the following is a mechanism of neuroprotective effect of barbiturates?
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What is the primary mode of metabolism of barbiturates?
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In what way do barbiturates affect intracerebral pressure (ICP)?
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What is a contraindication for the use of barbiturates?
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Which barbiturate has a high context sensitivity and may lead to accumulation of the active metabolite pentobarbital with prolonged infusion?
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Which drug has been used as a pediatric rectal premedicant?
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Which drug is often the drug of choice for Electroconvulsive Therapy (ECT)?
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Which drug has been used in low doses to induce seizure discharges in temporal lobe epilepsy?
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Which drug resembles phencyclidine in its chemical structure?
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Which drug has a greater affinity for the phencyclidine binding site on the NMDA receptor?
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Which drug has been associated with decreased salivation and decreased incidence of emergence reactions?
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Which drug is not known to produce analgesia, but not antianalgesic?
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Which drug is supplied in three strengths: 1%, 5%, and 10%?
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What type of state does ketamine produce depending on dose, where the individual may remain conscious or may be unconscious but appear awake in a cataleptic state?
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What receptor does ketamine inhibit to produce intense analgesia and amnesia?
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Study Notes
- Barbiturates act on GABAA receptors: At low concentrations, they enhance the effect of GABA and decrease its dissociation rate. At high concentrations, they directly activate the opening of chloride channels and act on glutamate, adenosine, and neuronal nicotinic acetylcholine receptors.
- Barbiturates are metabolized primarily by hepatic oxidation. Their metabolism can be influenced by drugs that induce hepatic oxidative microsomes, such as barbiturates themselves.
- Barbiturates have various organ system effects:
- Central Nervous System (CNS): They cause proportional decreases in CMRO2 and CBF, reducing intracerebral pressure. They decrease mean arterial pressure less than ICP, improving cerebral perfusion. Maximum decrease in CMRO2 is around 50-55%, which requires hypothermia.
- Cardiovascular: Barbiturates induce peripheral vasodilation and decreased contractility, increasing heart rate and decreasing cardiac output.
- Respiratory: All intravenous induction agents except ketamine and etomidate cause dose-dependent respiratory depression, making respiratory parameters return to near normal within 15 minutes, with awakening occurring before normal respirations return.
- Barbiturates have been used in the past for neuroprotection during neurosurgery and following acute brain injuries. However, they have not been shown to be superior to other techniques for decreasing ICP following acute brain injury.
- Barbiturates were previously used for neuroprotection in procedures like carotid endarterectomy, temporary occlusion of cerebral arteries, profound induced hypotension, and cardiopulmonary bypass.
- Mechanisms of neuroprotective effect of barbiturates include reverse steal (Robin Hood) effect, free radical scavenging, and liposomal membrane stabilization. They can also block excitatory amino acids (EAA) at higher concentrations, functioning as anticonvulsants.
- Barbiturates have various contraindications: severe cardiovascular instability or shock, porphyria, and allergic reactions. Porphyria is a group of disorders with multiple subtypes, including acute intermittent porphyria, which is triggered by induction of heme synthesis.
- Barbiturate use has side effects and complications: cardiovascular and respiratory side effects are dose-dependent, and no significant differences exist between the barbiturates in terms of cardiovascular or respiratory side effects. At low blood levels, thiopental has been described as having an antianalgesic effect.
- Barbiturates have other uses: as a lethal injection combination, in truth serum, as a recreational drug, and as an intravenous induction agent.
- Thiopental, a commonly used barbiturate, has a high context sensitivity and may lead to accumulation of the active metabolite pentobarbital with multiple bolus dosing or prolonged infusion.
- Dosages for barbiturates vary for adults, children, and infants, and must be reduced in premedicated patients.
- Barbiturates can affect pregnancy, hypovolemia, obesity, females, and the elderly by decreasing the volume of the central compartment and the intermediate compartment.
- Thiopental infusions are used to treat status epilepticus and methohexital dosing is approximately 2 mg/kg.
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Description
Test your knowledge of the mechanism of action and pharmacokinetics of GABAA receptors. Explore how different concentrations affect the receptor and their metabolism. Challenge yourself with this quiz!
