Podcast
Questions and Answers
Which anesthetic was first used successfully in a surgical procedure?
Which anesthetic was first used successfully in a surgical procedure?
Which anesthetic was deemed a failure in its initial demonstration because the patient cried out?
Which anesthetic was deemed a failure in its initial demonstration because the patient cried out?
Which anesthetic was initially considered a success due to its sweet smell and non-flammable nature, but was later found to cause hepatotoxicity and cardiovascular depression?
Which anesthetic was initially considered a success due to its sweet smell and non-flammable nature, but was later found to cause hepatotoxicity and cardiovascular depression?
Which anesthetic was used for 30 years but was eventually replaced due to flammability concerns related to the increased use of electrical equipment and electrocautery in surgery?
Which anesthetic was used for 30 years but was eventually replaced due to flammability concerns related to the increased use of electrical equipment and electrocautery in surgery?
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Which theory initially proposed that the potency of anesthetics was directly related to their lipid solubility?
Which theory initially proposed that the potency of anesthetics was directly related to their lipid solubility?
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Which of the following statements about the Meyer-Overton Theory is NOT correct?
Which of the following statements about the Meyer-Overton Theory is NOT correct?
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Which of the following findings challenged the Meyer-Overton Theory's explanation for anesthetic potency?
Which of the following findings challenged the Meyer-Overton Theory's explanation for anesthetic potency?
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Which of the following anesthetics is chemically unstable to soda lime?
Which of the following anesthetics is chemically unstable to soda lime?
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Which anesthetic has the lowest blood/gas partition coefficient, making it ideal for rapid induction and recovery?
Which anesthetic has the lowest blood/gas partition coefficient, making it ideal for rapid induction and recovery?
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Which anesthetic is known for its pungent odor and is often used for maintaining anesthesia rather than induction?
Which anesthetic is known for its pungent odor and is often used for maintaining anesthesia rather than induction?
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Which anesthetic agent is known to relax the uterus and is therefore not recommended for use during labor?
Which anesthetic agent is known to relax the uterus and is therefore not recommended for use during labor?
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Which of the following is NOT a characteristic of Desflurane?
Which of the following is NOT a characteristic of Desflurane?
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Which of these anesthetics has the highest MAC value, indicating its weaker potency and requiring a higher concentration for anesthesia?
Which of these anesthetics has the highest MAC value, indicating its weaker potency and requiring a higher concentration for anesthesia?
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Which anesthetic is most likely to cause arrhythmias?
Which anesthetic is most likely to cause arrhythmias?
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Which anesthetic is often used for induction of anesthesia but has a faster recovery time compared to other volatile agents?
Which anesthetic is often used for induction of anesthesia but has a faster recovery time compared to other volatile agents?
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Which anesthetic is generally used for maintaining anesthesia instead of induction, due to its pungent odor?
Which anesthetic is generally used for maintaining anesthesia instead of induction, due to its pungent odor?
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What is the primary reason cocaine should not be used with epinephrine?
What is the primary reason cocaine should not be used with epinephrine?
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Which local anesthetic is primarily used by injection and is ineffective topically due to high polarity?
Which local anesthetic is primarily used by injection and is ineffective topically due to high polarity?
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Which property of Chloroprocaine allows for its rapid action and systemic safety?
Which property of Chloroprocaine allows for its rapid action and systemic safety?
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What is a significant drawback of Benzocaine as a local anesthetic?
What is a significant drawback of Benzocaine as a local anesthetic?
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Which of the following local anesthetics has a longer duration of action than Procaine?
Which of the following local anesthetics has a longer duration of action than Procaine?
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What is a characteristic of exothermic reactions in anesthesia?
What is a characteristic of exothermic reactions in anesthesia?
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Which of the following barbiturates is NOT mentioned as a general anesthesia option?
Which of the following barbiturates is NOT mentioned as a general anesthesia option?
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What is the primary mechanism of barbiturates in inducing anesthesia?
What is the primary mechanism of barbiturates in inducing anesthesia?
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Which of the following statements about Propofol is FALSE?
Which of the following statements about Propofol is FALSE?
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What is a significant drawback of using Etomidate?
What is a significant drawback of using Etomidate?
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What is a common side effect associated with the use of barbiturates during general anesthesia?
What is a common side effect associated with the use of barbiturates during general anesthesia?
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What characterizes the induction and recovery process of both barbiturates and Propofol?
What characterizes the induction and recovery process of both barbiturates and Propofol?
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Why can bacterial contamination be a concern with Propofol?
Why can bacterial contamination be a concern with Propofol?
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Which agent is typically used in patients at risk for hypotension due to its effects on blood pressure?
Which agent is typically used in patients at risk for hypotension due to its effects on blood pressure?
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What effect does Propofol have on blood pressure?
What effect does Propofol have on blood pressure?
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Which characteristic is primarily associated with ketamine's dissociative anesthesia?
Which characteristic is primarily associated with ketamine's dissociative anesthesia?
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What is the primary mechanism by which local anesthetics achieve their effect?
What is the primary mechanism by which local anesthetics achieve their effect?
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What is a significant advantage of ketamine over other anesthetic agents?
What is a significant advantage of ketamine over other anesthetic agents?
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What physiological effect does ketamine have following emergence from anesthesia?
What physiological effect does ketamine have following emergence from anesthesia?
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Which statement accurately describes a potential side effect associated with ketamine?
Which statement accurately describes a potential side effect associated with ketamine?
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Which of the following is a potential benefit of using ketamine in certain patients?
Which of the following is a potential benefit of using ketamine in certain patients?
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What defines local anesthesia as stated in the provided content?
What defines local anesthesia as stated in the provided content?
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What is a common clinical application for topical local anesthetics?
What is a common clinical application for topical local anesthetics?
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Which aspect of ketamine's pharmacological action is most relevant to its use in pediatric patients?
Which aspect of ketamine's pharmacological action is most relevant to its use in pediatric patients?
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What symptom is characteristic of a cataleptic state produced by ketamine?
What symptom is characteristic of a cataleptic state produced by ketamine?
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Study Notes
General Anesthesia
-
History:
- Early anesthetic practices relied on alcohol and opium, and strong men to hold patients down while surgeons worked quickly.
- Amputations were the most common surgeries.
- Crawford Long used ether for surgery in 1842 on James Venable.
- William Morton performed a public demonstration of ether at Mass. General Hospital in 1846.
- Horace Wells demonstrated nitrous oxide in Boston in 1845; deemed a failure at the time.
- James Simpson utilized chloroform for childbirth in Scotland in 1847. Chloroform offered advantages over ether (less irritating, non-flammable, sweet-smelling).
- Gardner Colton reintroduced nitrous oxide to dental and surgical procedures in 1863.
- Nitrous oxide and oxygen were used together in 1868.
- Cyclopropane (derived as a contaminant in propylene) was introduced in 1929. Used for 30 years but less desirable as electrical equipment in surgery became more common.
- Halothane was synthesized in 1956, a fluorinated hydrocarbon.
Mechanism of Action for Volatile Anesthetics
- Meyer-Overton theory (1900s): potent anesthetics have high lipid solubility.
- Compounds with higher lipid solubility require lower concentrations to produce anesthesia.
- Anesthetics dissolve in the lipid portions of cell membranes, causing swelling and altering ion channel function, which reduces nerve firing.
- Not all lipid-soluble compounds produce anesthesia.
- Volatile anesthetic mechanism is more complex than simply lipid solubility.
- Volatile anesthetics interact with protein receptors, including ion channels like chloride, potassium, and sodium channels.
General Anesthesia: Important Compounds
| Compound | MAC | MAC Awake | Blood/gas PC | Blood/Brain PC | Properties |
|---|---|---|---|---|---|
| Halothane | 0.75 | 0.41 | 2.3 | 2.9 | BP 50.2, Not stable to Soda Lime, Sweet odor, About 20% metabolized, Increased hepatotoxicity, Arrhythmias |
| Isoflurane | 1.2 | 0.4 | 1.4 | 2.6 | BP 48.5, Stable to Soda Lime, Less cardiovascular problems, More pungent odor |
| Enflurane | 1.6 | 0.4 | 1.8 | 1.4 | BP 56.5, Stable to Soda Lime, Mild sweet odor, Less Nausea, Arrhythmias, and shivering |
| Sevoflurane | 2 | 0.66 | 0.65 | 1.7 | BP 58.5, Unstable to Soda Lime, Exothermic reaction, Sweet odor, Rapid induction |
| Desflurane | 6 | 2.4 | 0.45 | 1.3 | BP 23.5, Stable to Soda Lime, Pungent odor, Rapid induction, Good for outpatient surgery |
Barbiturates
- Thiopental, Thiamyl, Methohexital are compounds in this category
- Barbiturates' pKa is at or above blood pH, resulting in rapid entry into the brain.
- Recovery from anesthesia due to redistribution, not metabolism.
- Side effects include decreased cerebral oxygen consumption, decreased blood pressure, and depressed respiratory response to CO2 levels, potentially causing apnea, especially if used with opiates.
- Mechanism of action involves modulating GABA receptors, enhancing GABA's effects at beta subunits.
Propofol
- Commonly used intravenous anesthetic.
- Emulsion form (very low water solubility).
- Bacterial contamination is a concern, use or discard within 6 hours of opening.
- Mechanism involves interacting with GABA receptors, increasing sensitivity to GABA.
- Fast induction (40 seconds to reach the brain).
- Recovery is primarily via redistribution, different from barbiturates' slower elimination.
- Dose-dependent decrease in blood pressure, slightly elevated risk of respiratory depression compared to barbiturates.
Etomidate
- Commonly used IV anesthetic (D isomer)
- Major drawbacks include nausea, vomiting, inhibition of adrenal enzymes needed for cortisol production (adrenal corticoid stress response).
- This isn't typically problematic for short-term use.
- Poorly water-soluble, formulated as a solution in 35% propylene glycol.
- Typically used in patients likely to have hypotension issues.
Ketamine
- Structurally similar to phencyclidine (PCP).
- Inhibits NMDA receptors by binding to the PCP binding site, the S-isomer being more potent.
- Useful in patients at risk for hypotension, bronchospasms
- Commonly used for pediatric or emergency use.
- Recovery is dependent on redistribution.
- Increases cerebral blood flow, intracranial and intraocular pressure; increases blood pressure and heart rate by inhibiting catecholamine reuptake.
- Characterized by a cataleptic state, accompanied by nystagmus (rapid eye movement), dilation of pupils, salivation, lacrimation and spontaneous limb movements with increased overall muscle tone.
- Post-operative state characterized by delirium, hallucinations, vivid dreams, and illusions. This is more common in initial hours of post-anesthesia and less prevalent in younger patients.
Local Anesthetics
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General properties:
- Produce loss of sensation or motor function in a defined area.
- Used for temporary relief of pain in dental and minor procedures and spinal anesthesia.
- Topical local anesthetics are used to treat minor burns, bites, and allergic reactions, including hemmorhoids and procedures like sigmoidoscopy and intubation.
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Mechanism of Action:
- Block sodium channel activity, preventing action potential propagation.
- Affect the inside surface of cell membranes.
- Lipophilicity (ability to cross membranes) is key to potency and duration of action.
-
Ester-type (e.g., cocaine):
- Cocaine has vasoconstriction which prolongs its duration.
- Cocaine interacts with α₂ adrenergic receptors, increasing nerve excitability and blood pressure.
- Other topical anesthetic agents may be used in conjunction with epinephrine to simulate vasoconstrictive effects; however, cocaine use with epinephrine shouldn’t take place to prevent serious consequences.
- Cocaine use can increase cardiovascular and CNS response.
- Examples include Hexylcaine, Benzocaine, Procaine, Chloroprocaine, Tetracaine, and Proparacaine
- Amide-type (e.g., lidocaine): - Lidocaine, Xylocaine, Mepivacaine, Carbocaine, Bupivacaine, Prilocaine - Similar to ester types, but amide types are more resistant to hydrolysis. Thus have longer effects.
- Other miscellaneous types: - Examples include, Pramoxine, and Dyclonine
Toxic Side Effects of Local Anesthetics
- CNS and cardiovascular reactions are often seen
- Possible side effects include: excitatory and/or depressive effects such as nervousness, dizziness, blurred vision, tremors, and drowsiness.
- Severe cases may merge into unconsciousness with concomitant respiratory depression.
- Cardiovascular reactions are characterized by hypotension, myocardial depression, bradycardia, and possibly cardiac arrest.
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Description
Explore the fascinating journey of general anesthesia from its early roots with alcohol and opium to the introduction of modern anesthetics like halothane. This quiz covers significant milestones and key figures in the evolution of anesthesia practices throughout history. Test your knowledge of the pivotal moments that have shaped surgical procedures today.
