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Questions and Answers
Which of the following is a characteristic of thiopentone sodium?
Which of the following is a characteristic of thiopentone sodium?
What is a common adverse effect of ketamine during recovery?
What is a common adverse effect of ketamine during recovery?
What advantage does propofol have as an intravenous anesthetic?
What advantage does propofol have as an intravenous anesthetic?
Which of the following preanesthetic medications is used specifically to relieve anxiety?
Which of the following preanesthetic medications is used specifically to relieve anxiety?
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Which patient condition makes the use of ketamine potentially dangerous?
Which patient condition makes the use of ketamine potentially dangerous?
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Which anaesthetic is primarily known for its analgesic properties rather than its potency?
Which anaesthetic is primarily known for its analgesic properties rather than its potency?
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What is a significant adverse effect of nitrous oxide?
What is a significant adverse effect of nitrous oxide?
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Which of the following general anaesthetics is contraindicated in patients with jaundice?
Which of the following general anaesthetics is contraindicated in patients with jaundice?
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What is the primary action of Halothane in terms of respiratory effects?
What is the primary action of Halothane in terms of respiratory effects?
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Which group of anaesthetics is known for being administered via inhalation?
Which group of anaesthetics is known for being administered via inhalation?
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Which anaesthetic is noted for being safe and non-irritating while also being non-explosive?
Which anaesthetic is noted for being safe and non-irritating while also being non-explosive?
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Which anaesthetic is known to inhibit NMDA receptors?
Which anaesthetic is known to inhibit NMDA receptors?
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Which of the following is a characteristic of intravenous anaesthetics?
Which of the following is a characteristic of intravenous anaesthetics?
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What is the primary characteristic of general anaesthetics?
What is the primary characteristic of general anaesthetics?
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Which of the following is classified as an inhalational anaesthetic?
Which of the following is classified as an inhalational anaesthetic?
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What occurs during Stage II of anaesthesia?
What occurs during Stage II of anaesthesia?
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Which intravenous agent is known for inducing dissociative anaesthesia?
Which intravenous agent is known for inducing dissociative anaesthesia?
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In which stage of anaesthesia does severe respiratory depression occur?
In which stage of anaesthesia does severe respiratory depression occur?
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What is the role of GABA in the mechanism of action of general anaesthetics?
What is the role of GABA in the mechanism of action of general anaesthetics?
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Which of the following is NOT a characteristic of Stage III of anaesthesia?
Which of the following is NOT a characteristic of Stage III of anaesthesia?
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What is the main function of halothane in the context of anaesthesia?
What is the main function of halothane in the context of anaesthesia?
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Study Notes
General Anesthesia
- General anesthetics are drugs that induce a reversible loss of all sensation and consciousness.
Classification of General Anesthetics
-
Inhalational:
- Gases: Nitrous oxide (N₂O), Xenon
- Liquids: Ether, Halothane, Enflurane, Isoflurane, Desflurane, Sevoflurane
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Intravenous:
- Inducing agents: Thiopentone sodium, Propofol, Methohexitone, Etomidate
- Slow-acting: Ketamine
- Benzodiazepines: Diazepam, Lorazepam, Midazolam
- Opioid analgesics: Fentanyl
Stages of General Anesthesia
- Stage I (Analgesia): Loss of pain sensation. Sensory transmission interference. Progresses from conscious state to analgesia. Amnesia and reduced awareness occurs as Stage II approaches.
- Stage II (Excitement): Delirium and combative behavior may occur. Rapid-acting agent (e.g., Propofol) often administered intravenously to proceed to Stage III.
- Stage III (Surgical Anesthesia): Progressive loss of muscle tone and reflexes. Skeletal muscle relaxation. The ideal stage for surgery. Continuous careful monitoring is required.
- Stage IV (Medullary Paralysis): Severe respiratory and vasomotor depression. Death can quickly ensue if circulation and respiration are not maintained.
Mechanism of Action of General Anesthetics
- Inhalational Anesthetics: Enhance GABA's (inhibitory neurotransmitter) action, enabling chloride channels to open. They also augment the actions of glycine (another inhibitory neurotransmitter) in the spinal cord and medulla.
- Barbiturates, Benzodiazepines, and Propofol: Potentiate GABA's action, opening chloride channels.
- Ketamine: Inhibits the excitatory NMDA type glutamate receptor.
- Certain Fluorinated Anesthetics and Barbiturates: Inhibit neuronal cation channel gated by nicotinic cholinergic receptors
Nitrous Oxide (N₂O)
- Cheap and commonly used anesthetic.
- Low potency, but effective analgesic.
- Fast onset and recovery.
- Typically used in combination with other anesthetics (70% N₂O + 25-30% O₂ + 0.2-2% other potent anesthetic).
- Minimal impact on respiration, heart rate, and blood pressure.
- Uses: Surgical procedures, obstetric procedures, emergency medical situations.
- Adverse effects: Interacts and degrades vitamin B12, potential for pneumothorax, air embolus, obstructive issues.
Halothane
- Volatile liquid with a sweet odor and is non-irritating and non-explosive.
- Potent anesthetic, but poor analgesic.
- Dilates bronchial tubes, often preferred for asthmatic patients.
- Uses: Induction (2-4%) and maintenance (0.5-1%) of anesthesia.
- Adverse effects: Hepatitis, hyperthermia, hangover, shivering, jaundice, raised intracranial pressure.
- Contraindications include pre-existing conditions like raised cerebrospinal fluid pressure, or jaundice.
Thiopentone Sodium
- Ultrashort-acting barbiturate administered intravenously (IV).
- Rapidly induces hypnosis and anesthesia.
- Suppresses CNS activity, reducing muscle tone and reflexes, within minutes.
- Uses: Induction of anesthesia, control of convulsions, protection against cerebral ischemia (lack of blood flow to brain).
- Adverse effects include laryngospasm, shivering, and delirium during recovery.
Ketamine
- Dissociative anesthetic.
- Produces profound analgesia, immobility, and amnesia with light sleep.
- Heart rate and blood pressure increase due to sympathetic stimulation.
- Respiration not significantly suppressed; reflexes remain active.
- Emergence delirium, hallucinations, and involuntary movements can occur.
- Dangerous for patients with hypertension or ischemic heart disease (IHD).
Propofol
- Most commonly used IV anesthetic.
- Rapid onset (unconsciousness within 45 seconds).
- Duration of action approximately 15 minutes.
- Anti-emetic properties.
- Non-irritating to airways, suits day care surgery well.
- Adverse effects: Pain during injection, blood pressure fluctuations.
Preanesthetic Medication
- Drugs administered prior to general anesthesia to enhance safety and patient comfort.
- Relieves anxiety (benzodiazepines)
- Prevents allergies and nausea (antihistamines, antiemetics).
- Provides analgesia (opioids).
- Prevents acidity (proton pump inhibitor)
- Prevents bradycardia (atropine).
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Description
Explore the fascinating world of general anesthesia, including classifications of anesthetic agents such as inhalational and intravenous types. Learn about the stages of anesthesia, from loss of sensation to the surgical state. This quiz provides insights into both the pharmacology and application of general anesthetics in medical practice.
