61 Questions
Which barbiturate revolutionized the practice of anesthesia in 1934?
Thiopental
Why do we still include a discussion of barbiturate pharmacology in this chapter?
Because barbiturates are the prototypes for all IV anesthetics
Why have overseas manufacturers ceased exporting barbiturates to the United States?
To protest their use in lethal injection
Which position substitution on barbituric acid increases the anticonvulsant potency?
Phenyl group at the fifth position
Which substitution on barbituric acid results in thiobarbiturates?
Sulfur at the second position
Which substitution on barbituric acid increases hypnotic potency but lowers the seizure threshold and causes myoclonus during induction?
Methyl group on the nitrogen
Which receptors do barbiturates act on, in addition to GABAA receptors?
Glutamate receptors
Which subunits of GABAA receptors are responsible for the immobilizing activity of pentobarbital?
β3 subunits
How do barbiturates increase the duration of the GABAA-activated opening of chloride channels?
By increasing the affinity of GABA for its binding site
Which organ is primarily responsible for the elimination of thiopental from the body?
Liver
What is the main reason for the rapid onset and awakening after a single IV dose of thiopental?
Rapid redistribution out of the brain
What happens to the plasma concentration of thiopental after discontinuation of a prolonged infusion?
It slowly decreases
Which organ is primarily responsible for the metabolism of thiopental?
Liver
What is the basis for the short action of most highly lipophilic drugs, including thiopental?
Rapid redistribution out of the brain
Why is recovery after large or repeated doses of thiopental more rapid for infants and children compared to adults?
Infants and children have a higher metabolism of thiopental in the liver
Which class of drugs has replaced barbiturates for preanesthetic medication?
Benzodiazepines
What is the advantage of using benzodiazepines over barbiturates for treatment of grand mal seizures?
Benzodiazepines have a more specific site of action in the CNS.
In what situation has rectal administration of barbiturates, specifically methohexital, been used to induce anesthesia?
In uncooperative or young patients
Which drug has replaced barbiturates for induction of anesthesia in most cases?
Propofol
What is the principal disadvantage of methohexital?
Myoclonus
Which drug produces less nausea and faster recovery milestones compared to barbiturates?
Propofol
Which barbiturate has the highest potency for IV induction of anesthesia?
Methohexital
At a blood pH of 7.4, which barbiturate has a higher percentage of nonionized form?
Methohexital
Which barbiturate is effective in inducing seizure activity in patients with psychomotor epilepsy undergoing temporal lobe resection?
Methohexital
Which barbiturate is the only one with pharmacodynamic effects different enough from thiopental and thiamylal to offer an alternative for IV induction of anesthesia?
Methohexital
At a blood pH of 7.4, which barbiturate has a higher percentage of nonionized form?
Methohexital
What is one advantage of using methohexital over thiopental for IV induction?
Lower seizure threshold
What is the effect of thiopental dose requirements with age?
Dose decreases with age
How does the dose of thiopental needed to produce anesthesia in early pregnancy compare to that for nonpregnant females?
Decreased by 18%
In what situation has methohexital been used to induce anesthesia?
In patients with psychomotor epilepsy
Which barbiturate has the highest potency for IV induction of anesthesia?
Methohexital
Which drug has replaced barbiturates for induction of anesthesia in most cases?
Propofol
What is the principal disadvantage of methohexital?
Excitatory phenomena
Why is recovery after large or repeated doses of thiopental more rapid for infants and children compared to adults?
Higher metabolism in infants and children
What is the main reason for the rapid onset and awakening after a single IV dose of thiopental?
Higher lipid solubility
What happens to the plasma concentration of thiopental after discontinuation of a prolonged infusion?
It decreases
Which class of drugs has replaced barbiturates for preanesthetic medication?
Benzodiazepines
Which drug produces less nausea and faster recovery milestones compared to barbiturates?
Propofol
What is the advantage of using benzodiazepines over barbiturates for treatment of grand mal seizures?
Lower incidence of side effects
Which drug can be administered to decrease refractory increased intracranial pressure (ICP)?
Thiopental
How do barbiturates decrease intracranial pressure (ICP)?
By inducing cerebral vascular vasoconstriction
Which barbiturate is commonly used for induction of anesthesia in patients with increased ICP?
Thiopental
What is the effect of barbiturates on cerebral metabolism?
They decrease cerebral metabolism
What is a potential disadvantage of barbiturate therapy for head trauma patients?
Improved outcome has not been demonstrated
What is the efficacy of barbiturate therapy for brain survival after global cerebral ischemia due to cardiac arrest?
It has not been proven either way
In what situation has barbiturate therapy been used to improve neuropsychiatric complications after cardiopulmonary bypass?
After embolism
In what type of cerebral ischemia do animal studies consistently show improved outcome with barbiturate therapy?
Focal cerebral ischemia
What is the effect of barbiturates on cerebral blood flow and cerebral metabolic rate of oxygen (CMRO2)?
They decrease cerebral blood flow and decrease CMRO2 proportionally
What is the main advantage of using barbiturates for treatment of incomplete (focal) cerebral ischemia?
They provide protection to poorly perfused areas of the brain
Which of the following is a common side effect of barbiturates on the cardiovascular system?
Peripheral vasodilation
What is the compensatory response to the decrease in blood pressure caused by thiopental?
Increased heart rate
Which part of the central nervous system is primarily affected by barbiturates, leading to the decrease in blood pressure?
Medullary vasomotor center
Which part of the central nervous system is primarily affected by barbiturates, leading to the decrease in blood pressure?
Medulla oblongata
What happens to the sensitivity of the medullary ventilatory center to carbon dioxide stimulation in the presence of thiopental?
It decreases
When are laryngeal reflexes and the cough reflex depressed after administration of barbiturates?
After large doses
Which type of evoked responses does thiopental affect?
Somatosensory evoked responses
Is thiopental an acceptable drug to administer when the ability to monitor somatosensory evoked potentials is desirable?
No, because it completely eliminates somatosensory evoked potentials
What is the effect of thiopental on brainstem auditory evoked responses?
It prolongs the latency of brainstem auditory evoked responses
Which substances may have accelerated metabolism due to barbiturate-induced enzyme induction?
Oral anticoagulants
What is the immediate effect of inadvertent intra-arterial injection of thiopental?
Intense vasoconstriction and excruciating pain
What is the most likely cause of allergic reactions associated with IV administration of barbiturates for induction of anesthesia?
Antigen-antibody interaction
Test your knowledge of barbiturates and their impact on the practice of anesthesia. Explore the history, uses, and import/export challenges surrounding thiopental and other sedative-hypnotic drugs.
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