Non–γ-Aminobutyric Acid Sedatives and Hypnotics
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Questions and Answers

Which of the following is a characteristic of dissociative anesthesia produced by ketamine?

  • The patient is amnesic (correct)
  • The patient's eyes remain closed
  • The patient is communicative and responsive
  • The patient experiences intense analgesia

    • What advantage does ketamine have over propofol and etomidate?

  • It is not a drug with abuse potential
  • It does not cause emergence delirium
  • It produces profound analgesia at subanesthetic doses
  • It does not require a lipid emulsion vehicle for dissolution (correct)

    • What limits the clinical usefulness of ketamine as a sole agent?

  • The need for a lipid emulsion vehicle for dissolution
  • The lack of analgesic properties
  • The frequency of emergence delirium (correct)
  • The potential for abuse

    • Which system in the brain shows evidence of dissociation in dissociative anesthesia produced by ketamine?

    <p>The thalamocortical and limbic systems</p> Signup and view all the answers

    What is a characteristic of the patient's eyes during dissociative anesthesia produced by ketamine?

    <p>They remain open with a slow nystagmic gaze</p> Signup and view all the answers

    What is the patient's level of wakefulness during dissociative anesthesia produced by ketamine?

    <p>Wakefulness may appear to be present</p> Signup and view all the answers

    What is a common occurrence during dissociative anesthesia produced by ketamine?

    <p>Varying degrees of hypertonus and purposeful skeletal muscle movements</p> Signup and view all the answers

    What is the patient's level of analgesia during dissociative anesthesia produced by ketamine?

    <p>Intense analgesia</p> Signup and view all the answers

    What advantage does ketamine have over propofol and etomidate?

    <p>Does not require a lipid emulsion vehicle for dissolution</p> Signup and view all the answers

    What limits the clinical usefulness of ketamine as a sole agent?

    <p>Frequency of emergence delirium</p> Signup and view all the answers

    What precaution should be taken with ketamine due to its abuse potential?

    <p>Appropriate precautions against unauthorized nonmedical use</p> Signup and view all the answers

    Which of the following is true about ketamine?

    <p>Ketamine is a water-soluble molecule</p> Signup and view all the answers

    What is the designation for the left-handed optical isomer of ketamine?

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

    Which form of ketamine is clinically available for treatment of therapy-resistant depression?

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

    In Europe, esketamine is widely used for what purposes?

    <p>Both anesthetic and treatment of acute and chronic pain</p> Signup and view all the answers

    When studied separately, which isomer of ketamine produces more intense analgesia?

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

    Which isomer of ketamine has a lower incidence of emergence reactions?

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

    What is the analgesic potency of esketamine compared to racemic ketamine?

    <p>Approximately twice</p> Signup and view all the answers

    Which isomer of ketamine induces less fatigue and cognitive impairment at equianalgesic small doses?

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

    What effect does both isomers of ketamine have on the uptake of catecholamines back into postganglionic sympathetic nerve endings?

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

    What is the preservative used for ketamine?

    <p>Benzethonium chloride</p> Signup and view all the answers

    What is the mechanism of action of ketamine-induced analgesia and dissociative anesthesia?

    <p>Ketamine interacts with multiple CNS receptors.</p> Signup and view all the answers

    What is the effect of ketamine on GABAA receptors?

    <p>Ketamine has weak actions on GABAA receptors.</p> Signup and view all the answers

    What is the role of the innate repair receptor in mediating ketamine's effects on neuropathic pain?

    <p>The innate repair receptor plays a pivotal role in subduing tissue damage and inflammation.</p> Signup and view all the answers

    What is the effect of ketamine on the analgesic relief of acute pain?

    <p>Ketamine-induced relief of acute pain is not affected by the innate repair receptor.</p> Signup and view all the answers

    What is the effect of ketamine on cytokines in blood?

    <p>Ketamine directly inhibits cytokines in blood.</p> Signup and view all the answers

    What is the effect of ketamine on neutrophil production of inflammatory mediators?

    <p>Ketamine suppresses neutrophil production of inflammatory mediators.</p> Signup and view all the answers

    Which receptors does ketamine bind noncompetitively to?

    <p>Ketamine binds noncompetitively to the phencyclidine recognition site on NMDA receptors.</p> Signup and view all the answers

    Which receptors does ketamine exert effects at?

    <p>Ketamine exerts effects at opioid receptors, monoaminergic receptors, muscarinic receptors, and voltage-sensitive sodium and L-type calcium channels and neuronal nicotinic acetylcholine receptors.</p> Signup and view all the answers

    What is the designation for the left-handed optical isomer of ketamine?

    <p>The left-handed optical isomer of ketamine is known as esketamine.</p> Signup and view all the answers

    What is the effect of ketamine on wakefulness during dissociative anesthesia?

    <p>The patient's level of wakefulness is increased during dissociative anesthesia produced by ketamine.</p> Signup and view all the answers

    Which receptors does ketamine primarily interact with to inhibit the activation of NMDA receptors?

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

    What effect does ketamine have on sodium channels?

    <p>It blocks voltage-gated sodium channels</p> Signup and view all the answers

    Which type of nicotinic acetylcholine receptors does ketamine interact with?

    <p>Homomeric α7 nicotinic acetylcholine receptors</p> Signup and view all the answers

    Which of the following is true about the pharmacokinetics of ketamine?

    <p>Ketamine has a pK of 7.5 at physiologic pH.</p> Signup and view all the answers

    Where does ketamine initially distribute after administration?

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

    What is the elimination half-life of ketamine?

    <p>2 to 3 hours</p> Signup and view all the answers

    Which enzyme is responsible for the demethylation of ketamine to form norketamine and hydroxynorketamine?

    <p>Cytochrome P450 enzymes</p> Signup and view all the answers

    What is the percentage of a dose of ketamine that can be recovered from urine as unchanged drug after intravenous administration?

    <p>Less than 4%</p> Signup and view all the answers

    What effect does chronic administration of ketamine have on the metabolism of the drug?

    <p>Stimulates the activity of enzymes responsible for its metabolism</p> Signup and view all the answers

    Which drug is often recommended to decrease the likelihood of coughing and laryngospasm due to ketamine-induced salivary secretions?

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

    At what doses does ketamine produce prompt induction of anesthesia when administered intravenously?

    <p>High doses</p> Signup and view all the answers

    What is the primary clinical effect of ketamine at subanesthetic doses?

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

    Which system is responsible for the interpretation of painful signals?

    <p>Thalamic and limbic systems</p> Signup and view all the answers

    What is the role of NMDA receptors in pain processing?

    <p>Activation of NMDA receptors leads to spinal cord sensitization</p> Signup and view all the answers

    What is the effect of ketamine on neonatal neurobehavioral scores?

    <p>Ketamine analgesia during labor is associated with higher neonatal neurobehavioral scores compared to thiopental-nitrous oxide anesthesia</p> Signup and view all the answers

    Which of the following is a potential advantage of using ketamine as an analgesic adjuvant in patients with preexisting chronic pain syndromes who require surgery?

    <p>Ketamine has a lower potential for abuse or addiction</p> Signup and view all the answers

    What is the most likely reason for the limited value of neuraxial ketamine in producing analgesia?

    <p>Ketamine has a weak affinity for spinal opioid receptors</p> Signup and view all the answers

    What is the most likely reason for the additive or synergistic effect of ketamine when combined with other epidural analgesics?

    <p>Ketamine enhances the binding of local anesthetics to voltage-gated sodium ion channels</p> Signup and view all the answers

    Which receptors are responsible for the analgesic effects of ketamine?

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

    What is the primary mechanism of action of ketamine as an analgesic?

    <p>Inhibition of NMDA receptors</p> Signup and view all the answers

    What is the role of NMDA receptors in pain processing?

    <p>They modulate pain</p> Signup and view all the answers

    What is the effect of ketamine on sodium channels?

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

    What is the most likely reason for the limited value of neuraxial ketamine in producing analgesia?

    <p>Poor distribution to the spinal cord</p> Signup and view all the answers

    What is the effect of chronic administration of ketamine on the metabolism of the drug?

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

    What is the most likely reason for the additive or synergistic effect of ketamine when combined with other epidural analgesics?

    <p>Inhibition of NMDA receptors</p> Signup and view all the answers

    Which of the following is true about the analgesic effects of ketamine?

    <p>Ketamine produces long-lasting pain relief in rodent pain models.</p> Signup and view all the answers

    What is the most likely reason for the lower potential for abuse or addiction associated with hydroxynorketamine?

    <p>Hydroxynorketamine has a higher affinity for opioid receptors compared to ketamine.</p> Signup and view all the answers

    What is the most likely reason for the limited value of neuraxial ketamine for producing analgesia?

    <p>Ketamine has a weaker affinity for spinal opioid receptors compared to morphine.</p> Signup and view all the answers

    What is the most likely reason for the additive or synergistic effect of ketamine when combined with other epidural analgesics?

    <p>Ketamine has a stronger interaction with local anesthetic binding sites on voltage-gated sodium ion channels compared to other analgesics.</p> Signup and view all the answers

    What is a characteristic of dissociative anesthesia produced by ketamine?

    <p>Increased cerebral blood flow and intracranial pressure</p> Signup and view all the answers

    What is the effect of ketamine on GABAA receptors?

    <p>Ketamine inhibits the binding of GABA to GABAA receptors.</p> Signup and view all the answers

    What is the effect of ketamine on wakefulness during dissociative anesthesia?

    <p>Ketamine increases wakefulness.</p> Signup and view all the answers

    What is the elimination half-life of ketamine?

    <p>1-2 hours</p> Signup and view all the answers

    Which route of administration of ketamine does not produce pain or venous irritation?

    <p>Intravenous (IV)</p> Signup and view all the answers

    How long does it take for consciousness to be lost after intravenous administration of ketamine?

    <p>30 to 60 seconds</p> Signup and view all the answers

    What is the usual duration of unconsciousness after an injected induction dose of ketamine?

    <p>10 to 20 minutes</p> Signup and view all the answers

    What is the typical duration of amnesia after recovery of consciousness from ketamine?

    <p>60 to 90 minutes</p> Signup and view all the answers

    What is a potential advantage of using ketamine in burn patients undergoing dressing changes and skin grafting procedures?

    <p>Intense analgesic activity</p> Signup and view all the answers

    What is the primary clinical effect of ketamine at subanesthetic doses?

    <p>Dissociative anesthesia</p> Signup and view all the answers

    What is the cardiovascular effect of ketamine in acutely hypovolemic patients?

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

    What is the typical emergence time after repeated intravenous injections or continuous infusion of ketamine?

    <p>Even longer</p> Signup and view all the answers

    What is the effect of chronic administration of ketamine on tolerance?

    <p>May develop</p> Signup and view all the answers

    In which patient population has ketamine been used as an intramuscular induction drug?

    <p>Children and difficult-to-manage mentally challenged patients</p> Signup and view all the answers

    Which of the following is a consideration when administering ketamine to patients with coronary artery disease?

    <p>Increased myocardial oxygen requirements</p> Signup and view all the answers

    What is the recommended induction of anesthesia in patients with coronary artery disease?

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

    What is the potential benefit of combining subanesthetic doses of ketamine with propofol for total IV anesthesia?

    <p>More stable hemodynamics</p> Signup and view all the answers

    Why is ketamine considered a potentially useful drug for rapid IV induction of anesthesia in patients with asthma?

    <p>It has beneficial effects on airway resistance</p> Signup and view all the answers

    What precaution should be taken with ketamine in patients with systemic or pulmonary hypertension or increased ICP?

    <p>Use cautiously or avoid</p> Signup and view all the answers

    What is a potential undesirable effect of ketamine administration during eye operations or examinations?

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

    Is ketamine safe to administer to patients with malignant hyperthermia?

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

    What is a potential use of ketamine in pediatric cardiac catheterization?

    <p>Useful for anesthesia</p> Signup and view all the answers

    Should ketamine be used cautiously or avoided in patients with systemic or pulmonary hypertension?

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

    What effect does ketamine have on the interpretation of catheterization data in patients with coronary artery disease?

    <p>Possible cardiac-stimulating effects</p> Signup and view all the answers

    Which receptor is believed to be involved in the mechanism of opioid-induced tolerance?

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

    What is the effect of subanesthetic doses of ketamine on opioid tolerance?

    <p>Reduces the likelihood of tolerance</p> Signup and view all the answers

    In which psychiatric disorder has ketamine been shown to improve the postoperative depressive state?

    <p>Mental depression</p> Signup and view all the answers

    What is the FDA-approved use of intranasal esketamine?

    <p>Treatment of therapy-resistant depression</p> Signup and view all the answers

    What is the possible mechanism by which ketamine improves restless leg syndrome?

    <p>Inhibits neuroinflammation in the spinal cord</p> Signup and view all the answers

    What are the NMDA receptors thought to be involved in the pathophysiology of?

    <p>Mental depression</p> Signup and view all the answers

    What is the effect of intermittent treatment with low-dose ketamine in patients with obsessive compulsive disorder?

    <p>Improves obsessions and compulsions</p> Signup and view all the answers

    What is the effect of ketamine on the analgesic relief of acute pain?

    <p>Enhances analgesic relief</p> Signup and view all the answers

    Which system in the body does ketamine potentially inhibit to improve restless leg syndrome?

    <p>Inflammatory system</p> Signup and view all the answers

    What is the FDA-approved use of intranasal esketamine in conjunction with?

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

    Which of the following is a unique characteristic of ketamine among injected anesthetics?

    <p>It produces emergence delirium</p> Signup and view all the answers

    What is the effect of ketamine on intracranial pressure in mechanically ventilated animals with increased ICP?

    <p>It has no effect on ICP</p> Signup and view all the answers

    In patients requiring craniotomy for brain tumor or cerebral aneurysm resection, what effect does administration of ketamine have on middle cerebral artery blood flow velocity?

    <p>It has no effect on blood flow velocity</p> Signup and view all the answers

    What effect does ketamine have on intracranial pressure in patients with traumatic brain injury?

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

    What is the primary reason why ketamine is considered contraindicated in patients with increased intracranial pressure (ICP)?

    <p>It increases cerebral blood flow</p> Signup and view all the answers

    What effect does ketamine have on anterior fontanelle pressure in mechanically ventilated preterm neonates?

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

    What effect does ketamine have on cerebral metabolic rate of oxygen (CMRO2)?

    <p>It has no effect on CMRO2</p> Signup and view all the answers

    What is the effect of ketamine on cerebral blood flow in the presence of normocapnia?

    <p>It significantly increases cerebral blood flow</p> Signup and view all the answers

    What is the primary reason why patients with intracranial pathology are considered vulnerable to sustained increases in ICP after administration of ketamine?

    <p>It increases cerebral blood flow</p> Signup and view all the answers

    What is the primary effect of ketamine at subanesthetic doses?

    <p>Production of emergence delirium</p> Signup and view all the answers

    Which of the following is true about ketamine's effect on the EEG?

    <p>Ketamine produces a burst suppression pattern at high doses.</p> Signup and view all the answers

    What is the effect of ketamine on somatosensory evoked potentials?

    <p>Ketamine increases the cortical amplitude of somatosensory evoked potentials.</p> Signup and view all the answers

    What is the effect of ketamine on auditory and visual evoked responses?

    <p>Ketamine decreases auditory and visual evoked responses.</p> Signup and view all the answers

    Which of the following is a cardiovascular effect of ketamine?

    <p>Increased cardiac output</p> Signup and view all the answers

    What is the typical pattern of systemic blood pressure after IV injection of ketamine?

    <p>Initial increase followed by decrease</p> Signup and view all the answers

    Which of the following can prevent or blunt the cardiovascular-stimulating effects of ketamine?

    <p>Concomitant administration of inhaled anesthetics</p> Signup and view all the answers

    Which anesthetic is associated with a higher survival rate in shocked animals compared to halothane?

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

    What is the effect of ketamine administration on arterial lactate concentrations in animals with lower systemic blood pressures?

    <p>Greater increase</p> Signup and view all the answers

    What is the potential consequence of ketamine-induced vasoconstriction on tissue perfusion?

    <p>Decreased tissue perfusion</p> Signup and view all the answers

    Which of the following is the most important mechanism for the cardiovascular stimulation caused by ketamine?

    <p>Direct stimulation of the CNS</p> Signup and view all the answers

    What effect does ketamine have on epinephrine-induced cardiac dysrhythmias?

    <p>Abolishes them</p> Signup and view all the answers

    What is the effect of inhaled anesthetics, ganglionic blockade, β-blockade, cervical epidural anesthesia, and spinal cord transection on ketamine-induced increases in systemic blood pressure and heart rate?

    <p>They prevent the increases</p> Signup and view all the answers

    Which of the following mechanisms has been suggested as a possible explanation for how ketamine produces airway relaxation?

    <p>Increased circulating catecholamine concentrations</p> Signup and view all the answers

    What is a potential adverse effect associated with repeated use of ketamine in high doses?

    <p>Hemorrhagic cystitis</p> Signup and view all the answers

    Which of the following is a possible effect of ketamine on the liver?

    <p>Allergic hepatitis</p> Signup and view all the answers

    Which of the following statements about ketamine's effect on ventilation is most accurate?

    <p>Ketamine can cause apnea if administered rapidly IV or with an opioid</p> Signup and view all the answers

    What effect does ketamine have on upper airway reflexes and muscle tone?

    <p>Ketamine maintains upper airway reflexes and muscle tone</p> Signup and view all the answers

    What is the recommended precaution when using ketamine to prevent aspiration?

    <p>Placement of a cuffed tube in the patient's trachea is necessary</p> Signup and view all the answers

    Which receptors does ketamine primarily interact with to inhibit the activation of NMDA receptors?

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

    What is the most likely reason for the limited value of neuraxial ketamine in producing analgesia?

    <p>Poor penetration into the central nervous system</p> Signup and view all the answers

    What is the effect of ketamine on upper airway reflexes and muscle tone?

    <p>Decreases upper airway reflexes and muscle tone</p> Signup and view all the answers

    Which of the following factors is NOT associated with an increased incidence of emergence delirium after administration of ketamine?

    <p>A history of personality problems or frequent dreaming</p> Signup and view all the answers

    What is the most effective drug in preventing emergence delirium after administration of ketamine?

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

    What is the effect of including atropine in the preoperative medication before administration of ketamine?

    <p>Increases the incidence of emergence delirium</p> Signup and view all the answers

    Which of the following is a potential drug interaction with ketamine that may result in hypotension?

    <p>Administration of verapamil</p> Signup and view all the answers

    What is the potential effect of ketamine on the duration of apnea after administration of succinylcholine?

    <p>Prolonged duration</p> Signup and view all the answers

    Which of the following is a potential effect of ketamine on the cardiovascular system?

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

    Which type of ketamine blocks the cardioprotective effects of ischemic preconditioning in an animal model?

    <p>R(−) isomer</p> Signup and view all the answers

    Which type of ketamine does not block the cardioprotective effects of preconditioning or alter myocardial infarct size in an animal model?

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

    Which drugs should be used with caution in patients at risk for myocardial infarction during the perioperative period?

    <p>Drugs known to block preconditioning</p> Signup and view all the answers

    Which of the following is a common ingredient in over-the-counter cough suppressants?

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

    What is the potency of dextromethorphan as an antitussive compared to codeine?

    <p>Equally potent as codeine</p> Signup and view all the answers

    Which of the following is a symptom of intentional excessive intake of dextromethorphan?

    <p>Muscle rigidity and seizures</p> Signup and view all the answers

    Which drug has a longer elimination half-time, dexmedetomidine or clonidine?

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

    What is the primary route of excretion for the metabolites of dexmedetomidine?

    <p>Renal excretion</p> Signup and view all the answers

    What effect might dexmedetomidine have on plasma concentrations of opioids administered during anesthesia?

    <p>Increased plasma concentrations</p> Signup and view all the answers

    Which receptor does dexmedetomidine primarily act on?

    <p>α2 receptor</p> Signup and view all the answers

    What is the pharmacologically active component of medetomidine?

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

    What is the role of atipamezole in relation to dexmedetomidine?

    <p>It reverses the sedative and cardiovascular effects of dexmedetomidine</p> Signup and view all the answers

    Which receptor does dexmedetomidine primarily act on?

    <p>α2</p> Signup and view all the answers

    What is the main effect of dexmedetomidine on the sympathetic nervous system?

    <p>Decrease sympathetic activity</p> Signup and view all the answers

    Which drug is a specific and selective α2-receptor antagonist that reverses the sedative effects of dexmedetomidine?

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

    Which of the following statements about the elimination half-time of dexmedetomidine is true?

    <p>The elimination half-time of dexmedetomidine is shorter than that of clonidine.</p> Signup and view all the answers

    What is the primary route of excretion for the metabolites of dexmedetomidine?

    <p>Renal excretion</p> Signup and view all the answers

    What effect does dexmedetomidine have on cytochrome P450 enzyme systems?

    <p>Dexmedetomidine inhibits cytochrome P450 enzyme systems.</p> Signup and view all the answers

    Which of the following is a clinical use of dexmedetomidine?

    <p>Causing total IV anesthesia without depression of ventilation</p> Signup and view all the answers

    What effect does dexmedetomidine have on MAC for volatile anesthetics in animals?

    <p>Decreases MAC by 90%</p> Signup and view all the answers

    What effect does dexmedetomidine have on the range of temperatures triggering thermoregulatory defenses?

    <p>Increases the range</p> Signup and view all the answers

    Which of the following is a clinical use of dexmedetomidine?

    <p>Decreasing plasma catecholamine concentrations during anesthesia</p> Signup and view all the answers

    What effect does dexmedetomidine have on MAC for volatile anesthetics in animals?

    <p>Decreases MAC by greater than 90%</p> Signup and view all the answers

    What is a potential anesthetic technique for patients with a difficult upper airway?

    <p>High dose dexmedetomidine</p> Signup and view all the answers

    Which of the following is a clinical use of dexmedetomidine?

    <p>Decreasing plasma catecholamine concentrations during anesthesia</p> Signup and view all the answers

    What effect does dexmedetomidine have on MAC for volatile anesthetics in animals?

    <p>Decreases MAC by greater than 90%</p> Signup and view all the answers

    What is the effect of adding dexmedetomidine to lidocaine for IV regional anesthesia?

    <p>Improves the quality of anesthesia and postoperative analgesia without causing side effects</p> Signup and view all the answers

    Which of the following statements about dexmedetomidine is true?

    <p>Dexmedetomidine sedation is similar to natural sleep.</p> Signup and view all the answers

    What effect does dexmedetomidine have on the control of breathing?

    <p>Dexmedetomidine reduces the ventilatory response to hypoxia.</p> Signup and view all the answers

    What is a potential life-threatening effect of dexmedetomidine?

    <p>Upper airway collapse.</p> Signup and view all the answers

    Which of the following is a potential side effect of dexmedetomidine?

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

    What effect does dexmedetomidine have on the control of breathing?

    <p>Reduces resting ventilation</p> Signup and view all the answers

    What is a potential use of clonidine and dexmedetomidine in the ICU?

    <p>Preventing drug withdrawal symptoms</p> Signup and view all the answers

    Study Notes

    Ketamine Characteristics and Anesthesia

    • Dissociative anesthesia causes a trance-like state where the patient is awake but unaware, leading to detachment from the environment.
    • Ketamine provides advantages over propofol and etomidate, such as analgesic properties and minimal respiratory depression.
    • Limited clinical usefulness as a sole agent primarily due to potential emergence reactions and possible dissociative effects.

    Brain Systems and Eye Characteristics

    • The limbic system shows evidence of dissociation during ketamine-induced anesthesia.
    • Patient's eyes are often open during dissociative anesthesia, with a characteristic gaze.
    • Patients exhibit variable levels of wakefulness, potentially remaining responsive to commands despite not fully alert.
    • Common occurrences include hallucinations or vivid dreams during recovery.

    Analgesia and Inefficacy

    • Patients experience significant analgesia, although ketamine is not always sufficient on its own for complete pain management.
    • Potential for ketamine abuse necessitates careful monitoring and control in clinical settings.

    Isomers and Clinical Applications

    • Esketamine is the left-handed optical isomer of ketamine.
    • Esketamine is clinically available for treating therapy-resistant depression, showing effectiveness for acute, severe depression.
    • The R-ketamine isomer may produce more intense analgesia with fewer emergence reactions.

    Pharmacological Effects and Mechanisms

    • Ketamine binds noncompetitively to NMDA receptors, inhibiting their activation, and also interacts with nicotinic acetylcholine receptors.
    • It affects sodium channels, potentially contributing to its analgesic effect.
    • Mechanism includes modulation of GABAA receptors, enhancing inhibitory neurotransmission.

    Metabolism and Administration

    • Ketamine distributes rapidly post-administration, primarily in the brain and liver.
    • Elimination half-life typically ranges from 2 to 3 hours; metabolites include norketamine and hydroxynorketamine.
    • Up to 30% of a ketamine dose can be excreted unchanged in urine after intravenous administration.

    Clinical Uses and Considerations

    • Ketamine can be beneficial in patients with chronic pain syndromes, enhancing analgesia when combined with other medications.
    • It is useful in emergency settings, especially for quick induction due to rapid onset and minimal respiratory effects.
    • Considerations for use include caution in patients with coronary artery disease, hypertension, or increased intracranial pressure.

    Observations and Side Effects

    • Administration can lead to altered neurobehavioral scores in neonates and possible psychological effects.
    • In pediatric cardiac catheterization, ketamine offers sedation with improved tolerance and minimal cardiovascular instability.
    • Chronic use may lead to tolerance, necessitating adjustments in dosage.

    Unique Properties and Emergency Management

    • Ketamine's unique quality lies in its ability to provide analgesia and dissociative effects without significant respiratory depression.
    • It may increase intracranial pressure, posing risks in patients with existing elevated levels.
    • Recommended as a safe option for rapid induction in asthmatic patients due to bronchodilator effects.

    FDA Approvals and Recent Studies

    • Intranasal esketamine is approved for adjunctive treatment in major depressive disorder.
    • Low-dose intermittent ketamine treatments show promise in managing obsessive-compulsive disorder.

    Effects on Inflammation and Pain Processing

    • Ketamine may inhibit the release of inflammatory mediators from neutrophils and modulate cytokine levels during acute pain management.
    • NMDA receptors are critically involved in pain processing, with ketamine reducing their activation aiding in pain relief.

    Overall Implications

    • Ketamine is an important anesthetic with unique properties, useful in various clinical settings, including emergency medicine, pain management, and psychiatric treatment, while requiring careful consideration of dosing and patient status.

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    Test your knowledge on non-γ-Aminobutyric Acid sedatives and hypnotics with this quiz. Learn about the pharmacological properties and effects of ketamine, a phencyclidine derivative that produces dissociative anesthesia.

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