Questions and Answers
What is the principal objective of inhalation anesthesia?
Higher cardiac output decreases the FA/FI ratio.
True
What does FRC stand for in the context of inhalation anesthetics?
Functional Residual Capacity
Nitrous oxide is commonly known as __________.
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Which of the following inhalation anesthetics is known for rapid induction and recovery?
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What are the side effects of Nitrous oxide?
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Which inhalation anesthetic has a MAC of 1.2%?
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Halothane is a flammable gas.
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The MAC of Ether is __________.
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What is a disadvantage of Halothane?
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Isoflurane is a nonflammable liquid at room temperature.
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Study Notes
Inhalation Anesthetics Overview
- Inhalation anesthetics are primarily used for maintenance of anesthesia, allowing rapid alteration of depth by adjusting inhaled concentration.
- The goal is to achieve a constant partial pressure of anesthetic in the brain (Pbr) by maintaining equilibrium with alveolar pressure (Palv).
Uptake and Distribution Factors
- Inspired concentration (Fi): Higher inspired concentrations lead to increased alveolar concentrations and faster induction of anesthesia.
- Alveolar ventilation: The rate and depth of ventilation impact the volume of fresh gases entering the alveoli and subsequently increase alveolar concentration (FA).
- Time constant: Reflects the time required for gas flow to equal lung capacity; defined as FRC/V alveolar.
- Functional Residual Capacity (FRC): Higher FRC results in slower gas wash-in due to pre-existing air volume.
- FA/FI Ratio: A significant determinant of induction speed. Factors influencing this ratio include:
- Decreased blood anesthetic solubility increases FA/FI.
- Reduced cardiac output increases FA/FI.
- Increased minute ventilation elevates FA/FI.
Classification of Inhalation Anesthetics
- Gases: Nitrous oxide (N2O)
- Volatile liquids:
- Ether
- Halothane
- Isoflurane
- Enflurane
- Sevoflurane
- Desflurane
Nitrous Oxide (N2O)
- Commonly known as laughing gas, a non-flammable, colorless gas with a sweet odor.
- Poorly soluble in blood, facilitating rapid induction and recovery.
- Typically combined with oxygen at concentrations of 30% to 70% for general anesthesia.
- Safety profile: Minimal depression of respiratory function and cardiovascular system.
- Side effects may include hallucinations, nausea, vomiting, and potential megaloblastic anemia with prolonged exposure.
Ether
- A colorless, highly volatile liquid with a pungent odor; flammable and explosive.
- MAC (Minimum Alveolar Concentration) is 2-3%.
- Advantages: Significant CNS depression and excellent muscle relaxation.
- Disadvantages: Flammable, can irritate mucous membranes, lead to breath-holding, and cause nausea and vomiting.
Halothane (Fluothane)
- Colorless, non-flammable volatile liquid with a pleasant odor, but light-sensitive.
- Produces rapid induction and quick recovery with low water solubility.
- Affect cardiovascular system: Relaxes myocardium, decreases oxygen demand, induces vasodilation, and may cause hypotension with overdose.
- Respiratory system: Non-irritating, dilates bronchioles, decreases secretions but can depress reflexes.
- Risks: Potential for liver damage (Halothane Hepatitis) with repeated use.
- MAC is 0.75, used for induction and maintenance in general anesthesia.
Isoflurane (Forane)
- Halogenated ether, colorless and non-flammable at room temperature.
- Highly pungent, can cause hypertension and tachycardia due to vasodilation.
- Quicker induction and recovery, but may irritate the respiratory tract.
- MAC is 1.2%.
Summary of Effects on Systems
- Cardiovascular: Myocardial relaxation, decreased cardiac output and heart rate, potential for severe hypotension with overdose.
- Respiratory: Non-irritating, bronchodilation, reduced secretions, potential depression of airway reflexes.
- Liver: Risk of hepatotoxicity with repeated halothane administration.
Modern Anesthetic Considerations
- Modern inhalation agents aim for rapid induction, effective muscle relaxation, and minimal respiratory stimulation, balancing efficacy with safety profiles to mitigate post-operative nausea, vomiting, and other side effects.
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Description
This quiz covers the key concepts of inhalation anesthetics, focusing on their maintenance and the factors that influence induction speed. You will explore how inspired concentration, alveolar ventilation, time constant, and functional residual capacity affect anesthetic delivery and efficacy.
