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Questions and Answers
What is the primary mechanism of action of intravenous anesthetics, including propofol?
Which of the following induction agents is known to have a stimulatory effect on the cardiovascular system?
Which of the following side effects is specific to intraarterial injection of thiopentone?
How do barbiturates, benzodiazepines, and propofol affect the cardiovascular system?
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What is a common effect of most intravenous induction agents on the respiratory system?
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What is the benefit of slowing down the injection of an induction agent?
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What is the primary mechanism of termination of thiopental sodium's effect?
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What is a common side effect of propofol?
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How does ketamine typically affect the circulatory system?
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Which of the following induction agents is NOT a GABAA receptor agonist?
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Which induction agent is known for its rapid onset and short duration of action?
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What is the mechanism of action of halogenated anesthetics?
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What determines the rate at which an inhaled anesthetic reaches the brain?
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What effect do inhaled anesthetics have on the respiratory system?
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What is the effect of inhaled anesthetics on skeletal muscle?
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What is the effect of inhaled anesthetics on blood pressure and peripheral vascular resistance?
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Study Notes
Inhalation Anesthetics
- Nitrous oxide and halogenated anesthetics (Halothane, Isoflurane, Sevoflurane, Enflurane) are types of inhalation anesthetics.
- They interact with protein receptors to produce anesthetic effects.
Mechanism of Action
- Volatile anesthetics increase the activity of inhibitory neurotransmitters GABA and Glycine.
Pharmacokinetics of Inhaled Anesthetics
- The amount of anesthetic that reaches the brain is indicated by the oil:gas ratio (lipid solubility).
- The lower the blood:gas ratio, the more anesthetic will reach the brain.
General Actions of Inhaled Anesthetics
- Respiratory system: Depressed respiration and response to CO2.
- Kidney: Depression of renal blood flow and urine output.
- Muscle: High enough concentrations will relax skeletal muscle.
- Cardiovascular system: Generalized reduction in arterial pressure and peripheral vascular resistance.
Complications of Inhaled Anesthetics
- Regurgitation: Patient should be placed in the Trendelenburg position and material aspirated with suction apparatus.
- Intraarterial injection of thiopentone: Causes pain and blanching in hand and fingers due to crystal formation in capillaries.
- Prevenous injection: Causes blanching and pain, and may result in a small degree of tissue necrosis.
- Cardiovascular depression: More likely to occur in elderly, hypovolemic, or untreated hypertensive patients.
- Respiratory depression: Slow injection of an induction agent may reduce the extent of respiratory depression.
- Histamine release: Thiopentone may cause release of histamine with subsequent formation of typical weal.
Intravenous Induction Agents
- Commonly used IV induction agents: Propofol, Thiopental sodium, Ketamine.
Intravenous Anesthetics
- Most exert their actions by potentiating GABAA receptor.
- GABAergic actions may be similar to those of volatile anesthetics, but act at different sites on the receptor.
Organ Effects of IV Anesthetics
- Most decrease cerebral metabolism and intracranial pressure.
- Most cause respiratory depression.
- May cause apnea after induction of anesthesia.
- Cardiovascular effects: Barbiturates, benzodiazepines, and propofol cause cardiovascular depression.
Thiopental Sodium
- Rapid onset (20 seconds) and short-acting.
- Effect is terminated not by metabolism but by redistribution.
- Repeated administration or prolonged infusion approaches equilibrium at redistribution sites.
- Build-up in adipose tissue leads to very long emergence from anesthesia.
- Side effects: Hypotension, apnea, airway obstruction.
Propofol
- Short-acting agent used for induction and maintenance of general anesthesia and sedation.
- Onset within one minute of injection.
- Highly protein-bound in vivo and metabolized by conjugation in the liver.
- Side effects: Pain on injection, hypotension, transient apnea following induction.
Ketamine
- NMDA receptor antagonist.
- Usually stimulates rather than depresses the circulatory system.
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Description
Test your knowledge of inhalation anesthetics, including nitrous oxide and halogenated anesthetics, their mechanism of action, and pharmacokinetics. Learn about the pathways and general actions of general anesthetics and how they interact with the body.
