Sedatives and hypnotic agents
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Questions and Answers

What is the primary mechanism of propofol metabolism?

  • Reductive pathways
  • Oxidation by CYP450 hepatic enzymes (correct)
  • Glucuronidation
  • Sulfation

    • What is the characteristic of propofol that allows it to be used in patients with hepatic or renal dysfunction?

  • Dose-dependent elimination
  • High protein binding
  • Induction of CYP450 enzymes
  • Dysfunction of hepatic or renal systems does not negatively impair propofol (correct)

    • What is the benefit of using propofol for general anesthesia maintenance?

  • Increased risk of postoperative nausea and vomiting
  • Increased risk of respiratory depression
  • Prolonged recovery time
  • Minimal PONV and prompt awakening (correct)

    • What is the effect of propofol on bronchomotor tone in healthy and asthmatic patients?

    <p>Bronchodilation</p> Signup and view all the answers

    What is the effect of high doses of propofol and barbiturates on EEG activity?

    <p>Burst suppression</p> Signup and view all the answers

    What is the mechanism of decreased systemic blood pressure caused by propofol?

    <p>Decreased SVR and decreased CO</p> Signup and view all the answers

    What is the effect of propofol on intracranial pressure?

    <p>Decreased ICP</p> Signup and view all the answers

    What is the effect of propofol on pharyngeal contractile force?

    <p>Decreased pharyngeal contractile force</p> Signup and view all the answers

    What is the effect of propofol on cerebral autoregulation in response to changes in CO2?

    <p>Preserved cerebral autoregulation</p> Signup and view all the answers

    What is the primary mechanism of action of neuraxial neostigmine in producing analgesia?

    <p>Stimulation of muscarinic cholinergic receptors to produce analgesia</p> Signup and view all the answers

    What is a significant advantage of dexmedetomidine over clonidine?

    <p>Higher receptor affinity and selectivity for α2 receptors with a shorter duration of action</p> Signup and view all the answers

    What is a major side effect of epidural dexmedetomidine in cesarean sections?

    <p>Hypotension and bradycardia</p> Signup and view all the answers

    What is the benefit of using epidural dexmedetomidine in cesarean sections?

    <p>All of the above</p> Signup and view all the answers

    What is the primary mechanism by which benzodiazepines interact with GABA receptors?

    <p>By binding between the alpha and gamma subunit to increase the affinity of the receptor for GABA</p> Signup and view all the answers

    What is the result of increased chloride conductance in post-synaptic cells following benzodiazepine binding?

    <p>Hyperpolarization of the post-synaptic cell membrane</p> Signup and view all the answers

    What is a characteristic of the effects of benzodiazepines on adenosine degradation?

    <p>They decrease adenosine degradation, leading to increased cardioprotection</p> Signup and view all the answers

    What is a potential side effect of benzodiazepines when combined with other CNS depressants?

    <p>Loss of coordination and diminished cognitive function</p> Signup and view all the answers

    What is a characteristic of etomidate's effect on the cardiovascular system?

    <p>It has minimal changes in heart rate, stroke volume, or cardiac output</p> Signup and view all the answers

    What is a effect of etomidate on hepatic and renal function?

    <p>It has little impact on hepatic and renal function</p> Signup and view all the answers

    What is the effect of baclofen on neuronal transmission in the cerebral cortex, basal ganglia, thalamus, cerebellum, and spinal cord?

    <p>Suppression via agonism of GABA-B receptor</p> Signup and view all the answers

    What is the primary mechanism of action of ketorolac?

    <p>Cyclo-oxygenase inhibition to decrease prostaglandins</p> Signup and view all the answers

    What is the effect of magnesium sulfate on NMDA receptors?

    <p>Antagonizing calcium - inhibition</p> Signup and view all the answers

    What is the functional role of glutamate at the spinal cord level?

    <p>Excitatory</p> Signup and view all the answers

    What is the therapeutic use of intrathecal baclofen?

    <p>Treatment of pain associated with MS, CRPS type I, and low back pain</p> Signup and view all the answers

    What is the primary concern with the use of magnesium sulfate?

    <p>Neurotoxicity</p> Signup and view all the answers

    What is the effect of baclofen on electrolyte movement resulting in hyperpolarization and inhibition of glutamate and substance P?

    <p>Increase potassium conductance</p> Signup and view all the answers

    Which of the following neurotransmitters are inhibitory at the spinal cord level?

    <p>GABA and glycine</p> Signup and view all the answers

    What is Aquavan?

    <p>A more potent and soluble formulation of propofol with a larger Vd</p> Signup and view all the answers

    What is the mechanism of action of propofol?

    <p>Allosteric GABA-A agonist (a-b site) and modulates glycine receptors</p> Signup and view all the answers

    What are GABA receptors?

    <p>Ligand-gated chloride channels</p> Signup and view all the answers

    What is the result of propofol's high lipid solubility?

    <p>Fast onset and large Vd</p> Signup and view all the answers

    What is unique about the clearance of propofol?

    <p>Its clearance exceeds its hepatic blood flow</p> Signup and view all the answers

    What is unique about the context sensitive half time of propofol?

    <p>It is relatively unaffected by the duration of infusion - 40 mins after 8 hour infusion</p> Signup and view all the answers

    What characteristics make propofol neuroprotective?

    <p>Dose-dependent decrease in CRMO2 and thus CBF and ICP</p> Signup and view all the answers

    Which of the following are beneficial side effects of propofol?

    <p>Antiemetic</p> Signup and view all the answers

    What are the clinical manifestations of PRIS?

    <p>Metabolic acidosis, rhabdomyolysis, hyperkalemia, lipidemia, and cardiac dysfunction</p> Signup and view all the answers

    Which patient population tends to be affected by propofol-related infusion syndrome (PRIS)?

    <p>Critically ill children</p> Signup and view all the answers

    How does propofol have antioxidant properties?

    <p>Propofol's phenolic hydroxyl group scavenges free radicals</p> Signup and view all the answers

    How do propofol and etomidate enhance the affinity of GABA for GABAA?

    <p>They allosterically modulate the GABAA receptor to increase its affinity for GABA</p> Signup and view all the answers

    What is commonly observed after etomidate injection?

    <p>Myoclonus</p> Signup and view all the answers

    Etomidate has a longer CSHT than propofol

    <p>True</p> Signup and view all the answers

    How are propofol and etomidate metabolized?

    <p>Propofol - oxidation by hepatic enzymes</p> Signup and view all the answers

    What is a common side effect of etomidate?

    <p>Adrenal cortical suppression - dose-dependent inhibition of cholesterol to cortisol</p> Signup and view all the answers

    What effect does etomidate have on the respiratory system?

    <p>decreased Vt and increased RR</p> Signup and view all the answers

    Where do benzodiazepines bind on the GABA-A receptor?

    <p>Between the alpha and gamma subunit</p> Signup and view all the answers

    What is common amongst all benzodiazepines?

    <p>Highly protein bound to albumin and highly lipid soluble</p> Signup and view all the answers

    What effect do benzodiazepines have on opioids?

    <p>They decrease the analgesia of opioids</p> Signup and view all the answers

    What is unique about the solubility of midazolam?

    <p>It is water soluble at low pH but lipid soluble at physiologic pH</p> Signup and view all the answers

    What are the CNS effects of propofol?

    <p>Decreased CMRO2 with preserved cerebral vascular response to CO2</p> Signup and view all the answers

    What are the respiratory effects of propofol?

    <p>Ventilatory depressant and decreased swallowing reflex</p> Signup and view all the answers

    What effect does propofol have on the cardiovascular system?

    <p>Decreases CO (negative inotropy) and SVR (smooth muscle relaxation)</p> Signup and view all the answers

    CSHT in midazolam infusions reflect the duration of infusion

    <p>True</p> Signup and view all the answers

    Why has midazolam replaced diazepam in clinical anesthesia? (select 2)

    <p>Midazolam has a more rapid onset of action with a short duration</p> Signup and view all the answers

    What is unique about the duration of action for diazepam?

    <p>Its duration of action is a reflection of metabolism and elimination rather than redistribution</p> Signup and view all the answers

    What effect does diazepam have on the cardiovascular system?

    <p>Has minimal effects, similar to sleep</p> Signup and view all the answers

    What is the drug of choice for delirium tremens?

    <p>Diazepam</p> Signup and view all the answers

    Which benzodiazepine is more potent than midazolam or diazepam?

    <p>Lorazepam</p> Signup and view all the answers

    Ativan is ____ lipid soluble with a ___ onset than Versed

    <p>less, slower</p> Signup and view all the answers

    Why is Ativan not typically used in anesthesia induction?

    <p>Because of its long duration of action</p> Signup and view all the answers

    What is remimazolam?

    <p>An ultrashort-acting benzodiazepine that is metabolized by non-specific tissue esterases</p> Signup and view all the answers

    What is the mechanism of action of flumazenil?

    <p>Competitive antagonist of GABA receptors</p> Signup and view all the answers

    What is a precaution when administering flumazenil?

    <p>Using it in patients with seizure disorders</p> Signup and view all the answers

    What is the main difference in the mechanism of action between benzodiazepines and barbiturates?

    <p>Barbiturates increase the duration of opening of CL channels</p> Signup and view all the answers

    High doses of which sedative drug class can directly activate the GABA-A receptor?

    <p>Barbiturates</p> Signup and view all the answers

    What compound do thiobarbiturates have?

    <p>Sulfur</p> Signup and view all the answers

    What are the benefits of propofol compared to barbiturates?

    <p>Rapid onset and rapid awakening due to rapid distribution</p> Signup and view all the answers

    Which of the following anesthetics is thought to possess 'neuroprotective' properties and can be used for cerebral protection during incomplete brain ischemia?

    <p>Thiopental</p> Signup and view all the answers

    What is the mechanism of action of ketamine?

    <p>NMDA antagonist - Binds to the NMDA receptor to inhibit glutamate activation</p> Signup and view all the answers

    Ketamine is a racemic mixture. Which isomer is associated with faster clearance and more analgesia?

    <p>S(+) isomer</p> Signup and view all the answers

    How does ketamine produce sedation?

    <p>through a dissociative mechanism rather than CNS depression</p> Signup and view all the answers

    What are the cardiovascular effects of ketamine?

    <p>Increased heart rate, blood pressure, cardiac output, and peripheral vascular resistance</p> Signup and view all the answers

    How is ketamine metabolized?

    <p>Hepatically by CYP2B6 and CYP3A4 to normketamine, an active metabolite</p> Signup and view all the answers

    What precautions should be taken when using ketamine?

    <p>All of the above</p> Signup and view all the answers

    Ketamine possesses anticonvulsant activity

    <p>True</p> Signup and view all the answers

    Ketamine is a potent cerebral vasodilator.

    <p>True</p> Signup and view all the answers

    What is the mechanism of action of dexmedetomidine?

    <p>A highly selective alpha-2 agonist that inhibits activity in the locus ceruleus</p> Signup and view all the answers

    What are some potential side effects of dexmedetomidine?

    <p>Decreased plasma catecholamine supply, which may cause hypotension and bradycardia</p> Signup and view all the answers

    Study Notes

    Propofol

    • Propofol is taken up by lungs and then distributed to fat
    • Clearance exceeds hepatic blood flow, and volume of distribution (Vd) is very large
    • Pulmonary uptake is significant, and it is metabolized by CYP450 hepatic enzymes via oxidation
    • Conjugated to water-soluble metabolites and excreted by kidneys
    • Dysfunction of hepatic or renal systems does not significantly impair propofol

    Clinical Applications

    • Induction drug of choice for anesthesia: 1.5-2.5 mg/kg, with children needing larger doses and geriatrics needing smaller doses
    • Sedation: 25-100 mcg/kg/min, with prolonged infusion in pediatric patients leading to metabolic acidosis, lipemic plasma, bradycardia, and heart failure
    • Maintenance: 100-300 mcg/kg/min, often combined with a short-acting opioid or inhalation agent, and associated with minimal PONV and prompt awakening

    Side Effects

    • Reduced PONV
    • Antipruritic and anticonvulsant activity
    • Attenuation of bronchoconstriction in healthy and asthmatic patients, resulting in bronchodilation
    • Synergistic with other CNS depressants, e.g., synthetic opioids
    • Decreases CMRO2, CBF, ICP, and preserves cerebral autoregulation in response to changes in CO2
    • High doses produce burst suppression, and cortical SEE potentials are not significantly affected
    • Amnestic effects are similar to Versed

    Cardiovascular Effects

    • Decreases systemic BP due to decreased SVR and CO
    • Decreased SVR is due to relaxation of vascular smooth muscle and inhibition of sympathetic vasoconstriction
    • Decreased CO is due to negative inotropic effect and inhibition of the trans-sarcolemnal calcium influx
    • No change in HR, but CV effects are potentiated in hypovolemia, elderly, and LV dysfunction
    • Effects are reversed by laryngosenephrine, which stimulates and can reverse the decreased BP/SVR and CO effects

    Respiratory Effects

    • Dose-dependent depression of RR and Vt, and central depressant response to hypoxemia
    • Apnea frequently occurs, and respiratory effects are potentiated by opioids
    • Hypoxic pulmonary vasoconstriction remains intact, but decreases pharyngeal contractile force, relaxing muscles in the pharynx that keep the airway open

    Other Effects

    • Hepatic and renal function rarely affected
    • Lowers IOP during induction and intubation
    • No effects on coagulation and platelet function
    • Does not produce seizure activity, has anticonvulsant properties, and enhances SSE potential monitoring
    • Carries a significant abuse potential, supports bacterial growth, and increases frequency of excitatory spikes

    Benzodiazepines

    • Provide anxiolysis, sedation, anticonvulsant actions, spinal cord-mediated relaxation, and anterograde amnesia
    • GABA receptors concentrated in CNS
    • Mechanism of action involves binding between the alpha and gamma subunit to increase the affinity of the receptor for GABA, resulting in increased chloride conductance and hyperpolarization of the post-synaptic cell membrane
    • Ceiling effect and low toxicity, with differences in onset and duration of action reflecting differences in potency, lipid solubility, and pharmacokinetics
    • All are highly protein bound to albumin and highly lipid soluble, with a decrease in adenosine degradation having cardioprotective effects
    • Side effects include fatigue and drowsiness, loss of coordination and diminished cognitive function, profound amnesia, and synergistic effects with other CNS depressants

    Dexmedetomidine

    • A selective α2 receptor agonist with higher receptor affinity and selectivity for α2 receptors than clonidine
    • Fewer hemodynamic systemic effects, with intrathecal dose: 3 ug, and no neurotoxicity reported for intrathecal or epidural administration
    • Major side effects are bradycardia and hypotension

    Epidural Dex

    • Prolongs neuraxial sensory and motor blockade, decreases intraoperative anesthetic requirements, and improves postoperative analgesia
    • Decreases heart rate and BP in C-sections, with a black box warning for hypotension and bradycardia in C-sections

    Neuraxial Neostigmine

    • Inhibits acetylcholinesterase and prevents the metabolism of acetylcholine, with analgesic effects due to stimulation of muscarinic cholinergic receptors
    • Prolongs analgesia and minimal side effects with intrathecal (10-100 ug) or epidural (100-200 ug) use, and approved for treatment of neuropathic pain
    • Side effects include dizziness, confusion, ataxia, abnormal gait, memory impairment, and suicidal ideation

    Baclofen

    • A GABA-B receptor agonist suppressing neuronal transmission in the cerebral cortex, basal ganglia, thalamus, cerebellum, and spinal cord
    • Actions at laminae II & III, increasing potassium conductance and inhibiting calcium conductance, resulting in hyperpolarization and inhibition of glutamate and substance P release
    • Intrathecal baclofen is effective in treating pain with MS, CRPS type I, and low back pain

    Ketorolac

    • A cyclo-oxygenase inhibitor, with COX1 and COX2 facilitating production of prostaglandins leading to hyperalgesia and allodynia after injury
    • Intrathecal ketorolac appears to have little analgesia benefit

    Magnesium Sulfate

    • Acts on NMDA receptors by regulating calcium influx into cells, with magnesium being the natural antagonist to calcium
    • Does have some analgesic effect when administered intrathecally or in the epidural space, but animal studies have reported neurotoxicity, and human safety is not proven

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