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?

Phenothiazine derivatives Signup and view all the answers

What effect does atropine produce in the context of anesthesia?

Minimizes autonomic response to noxious stimuli Signup and view all the answers

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

Enhancement of GABA-mediated inhibition Signup and view all the answers

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

Thiopental Signup and view all the answers

What type of medication is atropine categorized as?

Anticholinergic Signup and view all the answers

Which adverse effect is associated with deeper levels of anesthesia?

Pupil constriction Signup and view all the answers

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

Hypoxia Signup and view all the answers

What is a common cardiovascular effect of general anesthetics?

Transient fall in cardiac output Signup and view all the answers

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

Thiopental Signup and view all the answers

Which of the following medications is considered an analgesic?

Morphine Signup and view all the answers

What is the primary mechanism of action for etomidate?

Activation of GABA receptors Signup and view all the answers

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

Hyperesthesia Signup and view all the answers

Which statement about the clinical application of etomidate is true?

It provides poor fetal transfer. Signup and view all the answers

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

Transient dose-dependent respiratory depression Signup and view all the answers

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

The amount of anesthetic in a liquid compared to its pressure in gas Signup and view all the answers

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

Struggling during the early stages of anesthesia Signup and view all the answers

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

A decrease in concentration leads to decreased tension. Signup and view all the answers

What effect does thiopental have on chloride channels?

It opens chloride channels through GABA receptor binding. Signup and view all the answers

What is one of the clinical applications of ketamine?

For induction before gaseous anesthesia. Signup and view all the answers

What is a direct cardiovascular effect of analgesia?

Reduction of blood pressure Signup and view all the answers

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

It varies the quantities of anesthetics in a solvent. Signup and view all the answers

Which effect does analgesia have on the respiratory system?

Results in less respiratory depression Signup and view all the answers

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

It induces a dissociative state and analgesia. Signup and view all the answers

What is a potential renal effect of analgesia?

No effect on renal function Signup and view all the answers

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

Hallucinatory behavior and delirium. Signup and view all the answers

Which phenomenon is triggered by skeletal muscle stimulation from analgesia?

Malignant hyperthermia Signup and view all the answers

How is halothane primarily utilized in anesthesia?

For maintaining anesthesia after induction with an injectable anesthetic. Signup and view all the answers

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

It is metabolized by cytochrome P450 in the hepatocytes. Signup and view all the answers

Which of the following statements is true about isoflurane?

It is the inhalation agent of choice in critically ill patients Signup and view all the answers

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

Gas is distributed from the lungs to peripheral tissues. Signup and view all the answers

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

Alone it raises intracranial pressure, but not when combined with benzodiazepine. Signup and view all the answers

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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Description

This quiz explores the clinical applications of ketamine, including its use in anesthesia and its unique mechanism of action. Additionally, it covers the sequence of anesthetic gas flow during induction. Understand the importance of ketamine in pain management and its potential adverse effects.