Clinical Applications of Ketamine and Anesthesia Flow

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Questions and Answers

What is the result of complete paralysis of the thoracic muscles with only the diaphragm functioning?

  • Jerky diaphragmatic movement (correct)
  • Muscle spasms and increased respiratory rate
  • Wide papillary dilatation
  • Slight relaxation of all muscles

Which drug is associated with mental blocking and loss of awareness?

  • Barbiturate
  • Ketamine (correct)
  • Atropine
  • Chloral hydrate

Which stage of anesthesia is often recognized with slower acting drugs?

  • Stage I
  • Stage III (correct)
  • Stage IV
  • Stage II

Which of the following drugs is linked to causing ataraxia?

<p>Phenothiazine derivatives (D)</p> Signup and view all the answers

What effect does atropine produce in the context of anesthesia?

<p>Minimizes autonomic response to noxious stimuli (B)</p> Signup and view all the answers

What is the primary mechanism of action for tranquilizers such as acepromazine and promazine?

<p>Enhancement of GABA-mediated inhibition (A)</p> Signup and view all the answers

Which of the following anesthetics is classified under the barbituric acid group?

<p>Thiopental (C)</p> Signup and view all the answers

What type of medication is atropine categorized as?

<p>Anticholinergic (D)</p> Signup and view all the answers

Which adverse effect is associated with deeper levels of anesthesia?

<p>Pupil constriction (A)</p> Signup and view all the answers

Which of the following symptoms can result from respiratory depression caused by anesthetics?

<p>Hypoxia (B)</p> Signup and view all the answers

What is a common cardiovascular effect of general anesthetics?

<p>Transient fall in cardiac output (B)</p> Signup and view all the answers

Which injectable anesthetic is known for causing local irritation upon perivascular injection?

<p>Thiopental (D)</p> Signup and view all the answers

Which of the following medications is considered an analgesic?

<p>Morphine (A)</p> Signup and view all the answers

What is the primary mechanism of action for etomidate?

<p>Activation of GABA receptors (B)</p> Signup and view all the answers

What is a potential consequence of an inadequate dose of pentobarbital during anesthesia?

<p>Hyperesthesia (C)</p> Signup and view all the answers

Which statement about the clinical application of etomidate is true?

<p>It provides poor fetal transfer. (C), It serves as an induction agent prior to gaseous anesthesia. (D)</p> Signup and view all the answers

What is the effect of GABA receptor binding in the context of respiratory function?

<p>Transient dose-dependent respiratory depression (C)</p> Signup and view all the answers

What does the solubility coefficient refer to in the context of anesthetics?

<p>The amount of anesthetic in a liquid compared to its pressure in gas (A)</p> Signup and view all the answers

Which of the following is a risk associated with the use of pentobarbital as a sole agent?

<p>Struggling during the early stages of anesthesia (A)</p> Signup and view all the answers

What effect does the concentration of anesthetic in the alveoli have on the brain tension?

<p>A decrease in concentration leads to decreased tension. (B)</p> Signup and view all the answers

What effect does thiopental have on chloride channels?

<p>It opens chloride channels through GABA receptor binding. (C)</p> Signup and view all the answers

What is one of the clinical applications of ketamine?

<p>For induction before gaseous anesthesia. (D)</p> Signup and view all the answers

What is a direct cardiovascular effect of analgesia?

<p>Reduction of blood pressure (A)</p> Signup and view all the answers

How does the solubility of anesthetics affect their application in clinical settings?

<p>It varies the quantities of anesthetics in a solvent. (C)</p> Signup and view all the answers

Which effect does analgesia have on the respiratory system?

<p>Results in less respiratory depression (D)</p> Signup and view all the answers

What is the primary action of ketamine as an NMDA receptor antagonist?

<p>It induces a dissociative state and analgesia. (C)</p> Signup and view all the answers

What is a potential renal effect of analgesia?

<p>No effect on renal function (A)</p> Signup and view all the answers

What is a notable adverse effect of ketamine when administered alone?

<p>Hallucinatory behavior and delirium. (A)</p> Signup and view all the answers

Which phenomenon is triggered by skeletal muscle stimulation from analgesia?

<p>Malignant hyperthermia (A)</p> Signup and view all the answers

How is halothane primarily utilized in anesthesia?

<p>For maintaining anesthesia after induction with an injectable anesthetic. (A)</p> Signup and view all the answers

Which of the following is true about the metabolism of halothane?

<p>It is metabolized by cytochrome P450 in the hepatocytes. (A)</p> Signup and view all the answers

Which of the following statements is true about isoflurane?

<p>It is the inhalation agent of choice in critically ill patients (A)</p> Signup and view all the answers

What is the sequence of how anesthetics flow from inhalation to body distribution?

<p>Gas is distributed from the lungs to peripheral tissues. (B)</p> Signup and view all the answers

What is the primary mechanism by which ketamine causes increased intracranial pressure?

<p>Alone it raises intracranial pressure, but not when combined with benzodiazepine. (D)</p> Signup and view all the answers

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Study Notes

Ketamine

  • Clinical applications include induction before gaseous anesthesia, rarely used as a sole agent, usually given with xylazine or diazepam
  • Ketamine does not produce a true anesthetic state, but induces dissociation from the environment, amnesia, and peripheral analgesia.
  • Increases muscle tone
  • Provides greater analgesia for somatic or peripheral pain
  • Mechanism of action: Acts as an NMDA (N-methyl-D-aspartate) receptor antagonist and sigma agonist. NMDA is an excitatory amino acid mimicking the action of glutamate in the CNS.
  • Adverse effects: CNS: raises intracranial pressure alone, but not when combined with benzodiazepine; can cause hallucinatory behavior, delirium, excitement, and purposeless muscle activity.

Sequence of Flow of Anesthetics

  • Gas is inhaled and diluted with residual air in the lungs
  • Gas is distributed into the alveoli where alveolar gas equilibrates almost immediately with pulmonary blood
  • Gas dissolved in the blood is distributed throughout the body: into the interstitial fluid and into the brain

Halothane

  • Primarily used to maintain anesthesia following induction with an injectable anesthetic.
  • 75% to 80% of inspired halothane is exhaled unchanged, metabolized by cytochrome P450 in the hepatocytes
  • Adverse effects:
    • CNS: dose-dependent depression of CNS without significant relaxation, complete paralysis of the thoracic muscles, only the diaphragm functions.
    • Respiratory: jerky diaphragmatic movement, respiration gasping in nature, wide papillary dilatation.
    • Mental blocking: loss of awareness (unconsciousness) and no recall of events at the conscious level (amnesia).
    • Ataraxia: Phenothiazine derivatives; Ketamine
    • Light sleep: Fentanyl-droperidol
    • Delirium: all that produces deep sleep
    • Reflex blocking: minimize autonomic nervous system response to noxious stimuli
    • Blocking undesirable reflexes: Atropine
    • Respiratory, circulatory, and digestive reflexes: Persistent pharyngeal reflex which becomes progressively depressed.

Stages of Anesthesia

  • Best recognized when anesthesia is induced by relatively slow-acting drugs such as diethyl ether.
  • Ketamine, nitrous oxide, and enflurane do not induce stage III.
  • Either they induce stage II only or advance to an increased level of CNS excitation, rather than depression, resulting in myoclonic jerking followed by convulsive seizures.
  • Irregular respiration; sometimes breath holding.

Pre-Anesthetic Agents

  • Tranquilizers: acepromazine, promazine
  • Analgesics: morphine, meperidine
  • Anesthetics: Xylazine, ketamine
  • Anticholinergic: atropine

Injectable Anesthetics

  • Examples: thiopental, alphaxolone, propofol, etomidate, ketamine, tiletamine-zolazepam, methohexital, pentobarbital.
  • Thiopental, methohexital, and pentobarbital belong to the barbituric acid group, classified according to either duration of action or chemical substitution on the parent molecule.

Pentobarbital

  • Infrequently used for induction.
  • Used as a sole agent for procedures.
  • Struggling may be seen in the early stages of anesthesia.
  • Inadequate dose may cause hyperesthesia.
  • Respiratory: transient dose-dependent respiratory depression.

Etomidate

  • Clincial applications: sole agent for non-painful procedures, induction prior to gaseous anesthesia, poor fetal transfer.
  • Mechanism of action: Produces dose-dependent cortical depression, activates GABA receptors to open chloride channels, analgesia.
  • Adverse effects:
    • Cardiovascular: direct depressant effect and indirect stimulatory effect.
    • Respiratory: respiratory depression.
    • Liver: no effect on hepatic function.
    • Renal: no effect on renal function.
    • Skeletal muscle: extreme muscle tone and spontaneous movements.
    • Other: hypersalivation, increased bronchial secretion, increased intraocular pressure.
  • Potentiates the action of non-depolarizing neuromuscular drugs.

Tiletamine-Zolazepam

  • Clincial applications: administered as the sole agent for short to moderate duration sedation or for induction before gaseous anesthesia.
  • Separately, they do not have ideal sedative or anesthetic properties.
  • Together, they produce dissociative anesthesia, muscle relaxation, and some analgesia.

Isoflurane

  • Clincial applications: most prevalent inhalation anesthetics, agent of choice in critically ill patients.
  • It enhances GABA-mediated inhibition of synaptic transmission by opening membrane chloride channels, causing cellular hyperpolarization.
  • Adverse effects:
    • CNS: dose-dependent CNS depression.
    • Cardiovascular: increased heart rate, decrease stroke volume, transient fall in cardiac output and arterial blood pressure.
    • Respiratory: respiratory depression.
    • Other: As anesthesia deepens, the pupil constricts rather than dilates.

Tension of Anesthetic Agent

  • The tension of an agent dissolved in a liquid refers to the pressure of the agent in gas.
  • At any given temperature the mass of gas dissolved in a solution varies directly with its tension.
  • The ratio of gas dissolved in solution to its tension is called its solubility coefficient.
  • The solubility of anesthetics varies widely, and the quantities of different anesthetics in the solvent are not equal.
  • The tension of the anesthetic agent in the brain is maintained when its concentration in the alveoli is kept constant.
  • When concentration in the alveoli decreases, the tension in the brain also decreases.
  • Minimum alveolar concentration (MAC) of the anesthetic must be maintained.

Drug Interactions

  • Potentiates the action of non-depolarizing neuromuscular drugs.

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