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Questions and Answers
Which receptor types are potentiated by Halothane?
Which receptor types are potentiated by Halothane?
What is the primary disadvantage of Nitrous oxide as an anesthetic?
What is the primary disadvantage of Nitrous oxide as an anesthetic?
What adverse effect is associated with prolonged use of Nitrous oxide?
What adverse effect is associated with prolonged use of Nitrous oxide?
Which of the following is a contraindication for the use of Nitrous oxide?
Which of the following is a contraindication for the use of Nitrous oxide?
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Which statement about Halothane is correct?
Which statement about Halothane is correct?
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What is the delivery range of Halothane for induction of anesthesia?
What is the delivery range of Halothane for induction of anesthesia?
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Which intravenous agent produces anesthesia within 20 seconds?
Which intravenous agent produces anesthesia within 20 seconds?
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Which of the following does NOT interact with GABAA receptors?
Which of the following does NOT interact with GABAA receptors?
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Which stage of anaesthesia is characterized by loss of pain sensation and reduced awareness?
Which stage of anaesthesia is characterized by loss of pain sensation and reduced awareness?
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What is a common characteristic of Stage II—Excitement in general anaesthesia?
What is a common characteristic of Stage II—Excitement in general anaesthesia?
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Which of the following is not a classified stage of general anaesthesia?
Which of the following is not a classified stage of general anaesthesia?
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Which intravenous agent is used for inducing general anaesthesia?
Which intravenous agent is used for inducing general anaesthesia?
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How do inhalational anaesthetics primarily exert their effect on the central nervous system?
How do inhalational anaesthetics primarily exert their effect on the central nervous system?
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What characterizes Stage IV—Medullary paralysis during anaesthesia?
What characterizes Stage IV—Medullary paralysis during anaesthesia?
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What is a significant characteristic of thiopentone sodium when administered intravenously?
What is a significant characteristic of thiopentone sodium when administered intravenously?
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Which drug is a known dissociative anaesthetic?
Which drug is a known dissociative anaesthetic?
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Which agent is primarily used for skeletal muscle relaxation during general anaesthesia?
Which agent is primarily used for skeletal muscle relaxation during general anaesthesia?
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Which of the following adverse effects is associated with ketamine?
Which of the following adverse effects is associated with ketamine?
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What is an important clinical consideration when using propofol?
What is an important clinical consideration when using propofol?
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What role do benzodiazepines play in preanesthetic medication?
What role do benzodiazepines play in preanesthetic medication?
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Which of the following is a contraindication for administering ketamine?
Which of the following is a contraindication for administering ketamine?
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Study Notes
General Anesthesia
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General anesthetics are drugs that induce a reversible loss of sensation and consciousness.
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Classification: Anesthetics are classified into inhalational and intravenous types.
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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
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Stage I (Analgesia): Loss of pain sensation, amnesia, and decreased awareness of pain.
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Stage II (Excitement): Delirium, possible combative behavior; rapid acting agents like propofol used before inhalation.
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Stage III (Surgical Anesthesia): Gradual loss of muscle tone and reflexes, ideal stage for surgery, continuous monitoring is crucial.
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Stage IV (Medullary Paralysis): Severe depression of respiratory and vasomotor centers; death is imminent without intervention.
Mechanism of Action
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Inhalational: Potentiate the action of GABA to open chloride channels. Enhance glycine's inhibitory action in the spinal cord and medulla. Some also inhibit excitatory NMDA glutamate receptors. Certain fluorinated anesthetics and barbiturates also inhibit nicotinic cholinergic receptors.
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Intravenous: Different mechanisms exist but several enhance GABA's action to increase chloride channel opening.
Nitrous Oxide (N₂O)
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Characteristics: Cheap, low potency anesthetic, but good analgesic, fast onset and recovery, 70% N₂O + 25-30% O₂ + 0.2-2% other potent anesthetic (eg halothane).
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Uses: Surgical procedures, obstetrics, and emergency situations.
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Adverse Effects: Interacts and degrades vitamin B12. Contraindicated in pneumothorax, air embolus and obstructive conditions.
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Additional Notes: It has little effect on respiration, heart, or blood pressure. It is non-flammable, non-irritating, and considered the safest inhalational anesthetic. Adverse effects include diffusional hypoxia and megaloblastic anemia.
Halothane
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Characteristics: Volatile liquid with a sweet odor, potent anesthetic but poor analgesic. Dilates bronchi so preferred for asthmatics. Used at 2-4% induction and 0.5-1% maintenance.
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Adverse Effects: Hepatitis, hyperthermia, hangover, shivering, and jaundice. Contraindicated in raised cerebrospinal fluid pressure.
Thiopentone Sodium
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Characteristics: Ultrashort-acting barbiturate given intravenously causes unconsciousness within 20 seconds. Supplemented with analgesics and muscle relaxants.
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Uses: Induction of anesthesia, control of convulsions, protection from cerebral ischemia.
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Adverse Effects: Laryngospasm, shivering, and delirium during recovery.
Ketamine
- Characteristics: Dissociative anesthetic; produces profound analgesia, immobility, and amnesia with light sleep. Heart rate and blood pressure are elevated due to sympathetic stimulation. Respiration is not depressed and reflexes are not abolished.
Propofol
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Characteristics: Most commonly used intravenous anesthetic. Consciousness occurs within 45 seconds and lasts 15minutes. Anti-emetic, non-irritant to airways. Suitable for day care and short procedures.
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Adverse Effects: Pain during injection and drop in blood pressure.
Preanesthetic Medication
- Purpose: To enhance the safety and ease of anesthesia procedures by relieving anxiety, preventing allergic reactions and nausea, and providing analgesia.
- Examples: Benzodiazepines (anxiety), antihistamines (allergy), antiemetics (nausea), opioids (analgesia), proton pump inhibitors (acidity), and atropine (bradycardia and secretion).
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Description
This quiz covers the classification and stages of general anesthesia. Dive deep into the types of anesthetic agents and their effects on patients during surgical procedures. Test your knowledge on inhalational and intravenous anesthetics, and understand the key stages of anesthesia.
