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Questions and Answers
Which drug has the highest potency based on MAC value?
Which of the following anesthetics is noted for its rapid induction and recovery?
Which anesthetic is associated with hepatotoxicity?
What is a common cardiovascular effect of Halothane?
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Which anesthetic is characterized by a pungent odor?
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All of the following anesthetics are respiratory depressants, EXCEPT:
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Which of the following effects is attributed to Isoflurane?
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Which anesthetic is least likely to provide skeletal muscle relaxation during labor?
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Which anesthetic drug is contraindicated in patients with seizure disorders?
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What is a common side effect of Methoxyfluran?
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Which anesthetic drug requires special equipment due to its low boiling point?
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What major effect does nitrous oxide have when used as an anesthetic?
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Which intravenous anesthetic is known for its rapid induction and recovery?
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Which of the following anesthetics has a pungent odor that can lead to airway irritation?
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What is a significant disadvantage of using Halothane as an anesthetic?
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Which anesthetic causes diffusion hypoxia as a side effect?
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What is a potential effect of ketamine that patients may experience postoperatively?
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Which drug combination is referred to as neuroleptanalgesia?
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Which side effect is associated with the use of Propofol?
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What is one of the contraindications for the use of Fentanyl?
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How does Propofol affect systemic blood pressure and heart rate?
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Which side effect could occur with the use of Sufentanil?
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Which drug is known to have a risk of causing cerebral hemorrhage?
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What is a notable effect of Etomidate during induction?
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Which stage of anesthesia is characterized by regular respiration and relaxation of skeletal muscles?
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What is the primary purpose of pre-anesthetic medications?
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Which of the following drugs is considered an opiate used to induce analgesia?
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What adverse effect may occur during Stage II (Excitement) of anesthesia?
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What is the primary action of neuromuscular blocking agents such as succinylcholine?
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Which type of receptors do inhibitory neurotransmitters like GABA and glycine act upon to decrease neuronal excitability?
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Which substance is NOT classified as a pre-anesthetic medication?
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What is a common effect of inhaled anesthetics combined with other medications in balanced anesthesia?
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Which anesthetic agent is known for its rapid induction and recovery, with low solubility and little effect on heart rate?
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What is a significant disadvantage of using nitrous oxide as an anesthetic?
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Which anesthetic agent has the potential for causing malignant hyperthermia?
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What adverse effect is common to both nitrous oxide and enflurane?
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Which of the following inhalational anesthetics is contraindicated for patients with seizure disorders?
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What is a characteristic of isoflurane when compared to halothane?
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Which of these anesthetics has the least liver toxicity?
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Which inhalational anesthetic is less potent than halothane and known for its pungent odor?
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Study Notes
General Anesthesia
- General anesthesia is the loss of consciousness and pain sensation.
- Used for surgeries and procedures.
Stages of Anesthesia
- Stage I (Analgesia): Loss of pain sensation, patient is conscious.
- Stage II (Excitement): Increased respiratory rate, irregular blood pressure, possible delirium and violent behavior.
- Stage III (Surgical Anesthesia): Regular respiration and skeletal muscle relaxation: eye reflexes decrease.
- Stage IV (Coma and Death): Medullary paralysis, severe depression of vasomotor and respiratory centers.
Desired Characteristics of General Anesthetics
- Smooth and rapid induction.
- Rapid recovery.
- Wide safety margin.
- Minimal side effects.
Balanced Anesthesia
- Using more than one drug in combination to fulfill patient needs.
Benefits of Balanced Anesthesia
- Pre-anesthetic medications calm the patient, relieve pain, protect against undesirable effects of administered anesthetics or surgical procedures, facilitate smooth induction of anesthesia, and lower the dose of anesthetic required.
- Intravenous (IV) anesthetics create smooth induction of anesthesia.
- Inhaled anesthetics reduce muscle tone.
Types of Pre-Anesthetic Medications
- Opiates: induce analgesia (e.g., morphine).
- Anticholinergics: prevent secretion of fluids into the respiratory tract (e.g., hyoscine).
- Sedatives and anxiolytics: relieve anxiety (e.g., diazepam).
- Antihistaminics: prevent allergic reactions (e.g., diphenhydramine).
- Antiemetics: prevent post-surgical nausea and vomiting (e.g., metoclopramide, prochlorperazine).
- H2-receptor blockers: reduce gastric acidity (e.g., ranitidine).
IV Anesthetics
- Thiopental: smooth induction.
Neuromuscular Blocking Agents
- Facilitate intubation and suppress muscle tone.
Examples of Neuromuscular Blocking Agents
- Succinylcholine, vecuronium, atracurium.
Mechanisms of Action of Anesthetics
- Disruption of ionic channels.
- Disruption of lipids associated with ionic channels.
- Receptor interaction:
- Inhibitory: GABA, Glycine.
- Excitatory: nAch, NMDA.
Inhaled Anesthetics:
- Enhance the action of GABA and glycine receptors leading to greater chloride ion entrance and hyperpolarization, decreasing neuronal excitability.
Potency and Induction:
- Minimum Alveolar Concentration (MAC): Concentration of inhaled anesthetic required to prevent movement in 50% of patients.
- Low MAC = High Potency
- Methoxyflurane: 0.16 MAC, Most potent, slow induction and recovery.
- Halothane: 0.75 MAC, Potent, slow induction and recovery.
- Isoflurane: 1.4 MAC, Less potent, moderate induction and recovery.
- Enflurane: 1.7 MAC, Less potent, moderate induction and recovery.
- Sevoflurane: 2 MAC, Less potent, rapid induction and recovery.
- Desflurane: 6-7 MAC, Less potent, very rapid induction and recovery.
- Nitrous oxide: >100 MAC, Least potent, rapid induction and recovery.
Inhaled Anesthetic Properties:
- Methoxyflurane: The most potent, low MAC value, slow induction and recovery.
- Halothane: Potent, slow induction and recovery, pleasant odor.
- Enflurane: Less potent, medium induction and recovery, pungent odor.
- Isoflurane: Less potent, medium induction and recovery.
- Sevoflurane: Less potent, rapid induction and recovery, better smell.
- Desflurane: Rapid induction and rapid recovery, pungent odor.
- Nitrous oxide: The least potent, high MAC value, rapid induction and recovery.
Central Nervous System (CNS) Effects
- All inhaled anesthetics decrease metabolic rate and increase intracranial pressure (ICP) (due to cerebral vasodilatation) - important consideration in head injuries.
- Dose-dependent EEG changes (Enflurane).
Cardiovascular System Effects
- Hypotension is common with all inhaled anesthetics.
- Bradycardia, except with Isoflurane and Desflurane.
- Myocardial depression (Halothane and Enflurane).
- Sensitize heart to catecholamines (Halothane).
Respiratory System Effects
- All inhaled anesthetics are respiratory depressants.
- Airway irritation (Desflurane and Enflurane).
Liver Effects
- Decrease hepatic flow (important consideration in patients with liver disease).
- Hepatotoxicity (Halothane only).
Uterus and Skeletal Muscle Effects
- Uterine relaxation (important consideration for pregnant patients).
- Nitrous oxide has minimal relaxant effects (can be used during labor).
- All inhaled anesthetics are skeletal muscle relaxants.
Halothane
- Potent anesthetic, slow induction and recovery.
- Weak analgesic; weak skeletal muscle relaxant.
- Metabolized to toxic metabolites (trifluroethanol) which are hepatotoxic.
- Causes cardiovascular depression: Hypotension, bradycardia (vagomimetic action), decreased myocardial contractility, decreased cardiac output.
- Adverse Effects:
- Hepatotoxicity with repeated use.
- Malignant hyperthermia.
- Cardiac arrhythmias.
- Sensitization of the heart to actions of catecholamines which may lead to arrhythmias.
Enflurane
- Less potent than halothane.
- Better muscle relaxation, better analgesic properties.
- Metabolized to fluoride (8%), excreted in the kidney.
- More rapid induction and recovery than halothane.
- Disadvantages:
- Pungent odor (makes induction unpleasant, not suitable for pediatrics), CNS stimulation (epilepsy-like seizure, abnormal EEG).
- Contraindications:
- Patients with seizure disorders.
- Patients with renal failure.
Isoflurane (Forane)
- More rapid induction and recovery than halothane.
- Stable compound (2%).
- Low biotransformation (less fluoride).
- No nephrotoxicity, no hepatotoxicity.
- Good analgesic action
- No sensitization of the heart, no cardiac arrhythmias.
- Disadvantages:
- Pungent odor (not suitable for pediatrics).
Desflurane
- Less potent than halothane.
- Pungent odor (causes irritation and coughing), rapid induction, and fast recovery (low solubility), less metabolized (0.05%), low boiling point (requires special equipment).
Sevoflurane
- Better smell (than other anesthetics).
- Less potent than halothane.
- Rapid onset and recovery (low solubility), less metabolized (3-5% fluoride), little effect on heart rate, no airway irritation (preferable for children).
Nitrous Oxide (N2O)
- Weak anesthetic (low potency, often used in combination with other agents).
- Rapid induction and recovery (the lowest blood: gas partition coefficient).
- Potent analgesic.
- No muscle relaxation, no respiratory depression, not hepatotoxic, minimal CVS adverse effects.
- Adverse Effects:
- Diffusion Hypoxia: (may occur in patients with respiratory diseases), Nausea and vomiting.
- Inactivation of B12 which may lead to megaloblastic anemia.
- Bone marrow depression, leukopenia (chronic use).
- Abortion – congenital anomalies.
Therapeutic Uses of Nitrous Oxide
- Outpatient anesthesia (dental procedures).
- Balanced anesthesia.
- Neuroleptanalgesia.
- Delivery.
Contraindications for Nitrous Oxide
- Pregnancy.
- Pernicious anemia.
- Immunosuppression.
Intravenous Anesthetics
- Ultra short acting barbiturates (Thiopental, methohexital).
- Benzodiazepines (diazepam, lorazepam, midazolam).
- Opioids (fentanyl).
- Ketamine.
- Propofol.
- Etomidate
Intravenous Anesthetic Structures
- Thiopental.
- Ketamine.
- Propofol.
- Etomidate.
Characteristics of Intravenous Anesthetics
- No special equipment needed.
- Rapid induction and recovery, except for benzodiazepines.
- Injected intravenously slowly (rapid induction).
- Recovery is due to redistribution from CNS.
- Analgesic activity: Opioids and ketamine.
- Amnesic action: benzodiazepines and ketamine.
- Can be used alone in short operations or in outpatient anesthesia.
- Increase in plasma catecholamine levels, increase in intracranial pressure (ICP).
- Potent bronchodilator (useful for asthmatics).
- Used in hypovolemic states, shock, and elderly patients.
- Post-operative hallucination, vivid dreams, disorientation, illusions.
- Risk of hypertension, cerebral hemorrhage, and ICP.
Opioids
- Fentanyl, Alfentanil, Sufentanil, and Remifentanil.
- Rapid onset, short duration of action, potent analgesia.
Opioid Uses:
- Neuroleptanalgesia (Fentanyl + Droperidol).
- Neuroleptanesthesia (Fentanyl + Droperidol + Nitrous oxide).
Opioid Side Effects:
- Respiratory depression.
- Bronchospasm (wooden rigidity).
- Hypotension.
- Nausea and vomiting.
Opioid Contraindications
- Head injuries.
- Pregnancy.
- Bronchial asthma.
- Chronic obstructive lung disease.
- Hypovolemic shock (only with large doses).
Neuroleptanalgesia
- A state of analgesia, sedation, and muscle relaxation without loss of consciousness.
- Useful for diagnostic procedures that require patient cooperation.
- Innovar (Fentanyl + Droperidol).
- Contraindications: Parkinsonism.
Neuroleptanesthesia
- A combination of Fentanyl + Droperidol + Nitrous Oxide.
Intravenous Anesthetic Effects on the Cardiovascular System
- Drug: Systemic Blood Pressure: Heart Rate.
- Propofol: ↓ : ↓
- Thiopental: ↓ : ↓
- Etomidate: No change (or slight ↓): No change.
- Ketamine: ↑ : ↑
Main Side Effects of Intravenous Anesthetics
- Thiopental: CVS collapse and respiratory depression (laryngospasm, bronchospasm), porphyria.
- Etomidate: Adrenocortical suppression, excitatory effects during induction, pain on injection site, post-operative nausea and vomiting.
- Propofol: CVS and respiratory depression, excitation (involuntary movements) during induction, pain at injection site, expensive.
- Ketamine: Psychotomimetic effects following recovery (vivid dreams, hallucinations), post-operative nausea and vomiting, salivation, risk of hypertension and cerebral hemorrhage.
- Midazolam: Slow induction and recovery, minimal CVS and respiratory depression.
- Opioids: Respiratory depression, bronchospasm (wooden rigidity), hypotension, nausea and vomiting, increase in ICP, urinary retention.
- Fentanyl: Prolongation of labor and fetal distress.
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Description
This quiz explores the key concepts of general anesthesia, including its stages and desired characteristics. Understand the benefits of balanced anesthesia and the importance of safety and recovery in surgical procedures. Test your knowledge on the vital aspects of anesthetic practices.
