Barbiturates and Anesthesia
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Questions and Answers

Which barbiturate revolutionized the practice of anesthesia in 1934?

  • Diethyl ether
  • Thiopental (correct)
  • Propofol
  • Etomidate
  • Why do we still include a discussion of barbiturate pharmacology in this chapter?

  • Because shipments of these drugs may resume
  • Because barbiturates are the prototypes for all IV anesthetics (correct)
  • Because anesthesiologists outside the United States still use these drugs
  • Because barbiturates are commonly used in capital punishment
  • Why have overseas manufacturers ceased exporting barbiturates to the United States?

  • Due to a shortage of barbiturates
  • To avoid competition with US manufacturers
  • To protest their use in lethal injection (correct)
  • Due to the high cost of exporting
  • Which position substitution on barbituric acid increases the anticonvulsant potency?

    <p>Phenyl group at the fifth position</p> Signup and view all the answers

    Which substitution on barbituric acid results in thiobarbiturates?

    <p>Sulfur at the second position</p> Signup and view all the answers

    Which substitution on barbituric acid increases hypnotic potency but lowers the seizure threshold and causes myoclonus during induction?

    <p>Methyl group on the nitrogen</p> Signup and view all the answers

    Which receptors do barbiturates act on, in addition to GABAA receptors?

    <p>Glutamate receptors</p> Signup and view all the answers

    Which subunits of GABAA receptors are responsible for the immobilizing activity of pentobarbital?

    <p>β3 subunits</p> Signup and view all the answers

    How do barbiturates increase the duration of the GABAA-activated opening of chloride channels?

    <p>By increasing the affinity of GABA for its binding site</p> Signup and view all the answers

    Which organ is primarily responsible for the elimination of thiopental from the body?

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

    What is the main reason for the rapid onset and awakening after a single IV dose of thiopental?

    <p>Rapid redistribution out of the brain</p> Signup and view all the answers

    What happens to the plasma concentration of thiopental after discontinuation of a prolonged infusion?

    <p>It slowly decreases</p> Signup and view all the answers

    Which organ is primarily responsible for the metabolism of thiopental?

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

    What is the basis for the short action of most highly lipophilic drugs, including thiopental?

    <p>Rapid redistribution out of the brain</p> Signup and view all the answers

    Why is recovery after large or repeated doses of thiopental more rapid for infants and children compared to adults?

    <p>Infants and children have a higher metabolism of thiopental in the liver</p> Signup and view all the answers

    Which class of drugs has replaced barbiturates for preanesthetic medication?

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

    What is the advantage of using benzodiazepines over barbiturates for treatment of grand mal seizures?

    <p>Benzodiazepines have a more specific site of action in the CNS.</p> Signup and view all the answers

    In what situation has rectal administration of barbiturates, specifically methohexital, been used to induce anesthesia?

    <p>In uncooperative or young patients</p> Signup and view all the answers

    Which drug has replaced barbiturates for induction of anesthesia in most cases?

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

    What is the principal disadvantage of methohexital?

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

    Which drug produces less nausea and faster recovery milestones compared to barbiturates?

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

    Which barbiturate has the highest potency for IV induction of anesthesia?

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

    At a blood pH of 7.4, which barbiturate has a higher percentage of nonionized form?

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

    Which barbiturate is effective in inducing seizure activity in patients with psychomotor epilepsy undergoing temporal lobe resection?

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

    Which barbiturate is the only one with pharmacodynamic effects different enough from thiopental and thiamylal to offer an alternative for IV induction of anesthesia?

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

    At a blood pH of 7.4, which barbiturate has a higher percentage of nonionized form?

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

    What is one advantage of using methohexital over thiopental for IV induction?

    <p>Lower seizure threshold</p> Signup and view all the answers

    What is the effect of thiopental dose requirements with age?

    <p>Dose decreases with age</p> Signup and view all the answers

    How does the dose of thiopental needed to produce anesthesia in early pregnancy compare to that for nonpregnant females?

    <p>Decreased by 18%</p> Signup and view all the answers

    In what situation has methohexital been used to induce anesthesia?

    <p>In patients with psychomotor epilepsy</p> Signup and view all the answers

    Which barbiturate has the highest potency for IV induction of anesthesia?

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

    Which drug has replaced barbiturates for induction of anesthesia in most cases?

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

    What is the principal disadvantage of methohexital?

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

    Why is recovery after large or repeated doses of thiopental more rapid for infants and children compared to adults?

    <p>Higher metabolism in infants and children</p> Signup and view all the answers

    What is the main reason for the rapid onset and awakening after a single IV dose of thiopental?

    <p>Higher lipid solubility</p> Signup and view all the answers

    What happens to the plasma concentration of thiopental after discontinuation of a prolonged infusion?

    <p>It decreases</p> Signup and view all the answers

    Which class of drugs has replaced barbiturates for preanesthetic medication?

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

    Which drug produces less nausea and faster recovery milestones compared to barbiturates?

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

    What is the advantage of using benzodiazepines over barbiturates for treatment of grand mal seizures?

    <p>Lower incidence of side effects</p> Signup and view all the answers

    Which drug can be administered to decrease refractory increased intracranial pressure (ICP)?

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

    How do barbiturates decrease intracranial pressure (ICP)?

    <p>By inducing cerebral vascular vasoconstriction</p> Signup and view all the answers

    Which barbiturate is commonly used for induction of anesthesia in patients with increased ICP?

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

    What is the effect of barbiturates on cerebral metabolism?

    <p>They decrease cerebral metabolism</p> Signup and view all the answers

    What is a potential disadvantage of barbiturate therapy for head trauma patients?

    <p>Improved outcome has not been demonstrated</p> Signup and view all the answers

    What is the efficacy of barbiturate therapy for brain survival after global cerebral ischemia due to cardiac arrest?

    <p>It has not been proven either way</p> Signup and view all the answers

    In what situation has barbiturate therapy been used to improve neuropsychiatric complications after cardiopulmonary bypass?

    <p>After embolism</p> Signup and view all the answers

    In what type of cerebral ischemia do animal studies consistently show improved outcome with barbiturate therapy?

    <p>Focal cerebral ischemia</p> Signup and view all the answers

    What is the effect of barbiturates on cerebral blood flow and cerebral metabolic rate of oxygen (CMRO2)?

    <p>They decrease cerebral blood flow and decrease CMRO2 proportionally</p> Signup and view all the answers

    What is the main advantage of using barbiturates for treatment of incomplete (focal) cerebral ischemia?

    <p>They provide protection to poorly perfused areas of the brain</p> Signup and view all the answers

    Which of the following is a common side effect of barbiturates on the cardiovascular system?

    <p>Peripheral vasodilation</p> Signup and view all the answers

    What is the compensatory response to the decrease in blood pressure caused by thiopental?

    <p>Increased heart rate</p> Signup and view all the answers

    Which part of the central nervous system is primarily affected by barbiturates, leading to the decrease in blood pressure?

    <p>Medullary vasomotor center</p> Signup and view all the answers

    Which part of the central nervous system is primarily affected by barbiturates, leading to the decrease in blood pressure?

    <p>Medulla oblongata</p> Signup and view all the answers

    What happens to the sensitivity of the medullary ventilatory center to carbon dioxide stimulation in the presence of thiopental?

    <p>It decreases</p> Signup and view all the answers

    When are laryngeal reflexes and the cough reflex depressed after administration of barbiturates?

    <p>After large doses</p> Signup and view all the answers

    Which type of evoked responses does thiopental affect?

    <p>Somatosensory evoked responses</p> Signup and view all the answers

    Is thiopental an acceptable drug to administer when the ability to monitor somatosensory evoked potentials is desirable?

    <p>No, because it completely eliminates somatosensory evoked potentials</p> Signup and view all the answers

    What is the effect of thiopental on brainstem auditory evoked responses?

    <p>It prolongs the latency of brainstem auditory evoked responses</p> Signup and view all the answers

    Which substances may have accelerated metabolism due to barbiturate-induced enzyme induction?

    <p>Oral anticoagulants</p> Signup and view all the answers

    What is the immediate effect of inadvertent intra-arterial injection of thiopental?

    <p>Intense vasoconstriction and excruciating pain</p> Signup and view all the answers

    What is the most likely cause of allergic reactions associated with IV administration of barbiturates for induction of anesthesia?

    <p>Antigen-antibody interaction</p> Signup and view all the answers

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