General Anesthetics Flashcards
What are the four stages of general anesthesia?
- Stage I – Decreased awareness of pain, amnesia, impaired consciousness
- Stage II – Disinhibition (delirium, excitation, irregular respiration, increased reflexes)
- Stage III – Surgical anesthesia (unconscious, no pain perception, maintained blood pressure)
- Stage IV – Medullary depression (severe respiratory and cardiovascular depression, requires support)
What are the goals of general anesthesia?
Unconsciousness, analgesia, immobility (skeletal muscle relaxation), inhibition of autonomic reflexes, and amnesia.
Define Minimum Alveolar Concentration (MAC) and its significance.
MAC is the alveolar concentration of an anesthetic at which 50% of patients do not respond to a surgical stimulus. It is an index of inhaled anesthetic potency—lower MAC values indicate higher potency.
How does the blood:gas partition coefficient affect anesthetic induction?
A lower blood:gas partition coefficient results in faster induction and recovery (e.g., nitrous oxide), whereas a higher coefficient results in slower induction and recovery (e.g., halothane).
What is the second gas effect?
When two inhalation anesthetics are given together (one at high concentration, like nitrous oxide), the second gas is absorbed more rapidly than if given alone.
Name the five inhaled anesthetics still in use today.
Nitrous oxide, Sevoflurane, Desflurane, Isoflurane, Halothane (in low-income countries).
Which inhaled anesthetic is most commonly used for rapid induction and recovery?
Sevoflurane – Popular for same-day surgery, non-pungent, good for mask induction in children.
What are the major side effects of Halothane?
Malignant hyperthermia, hepatotoxicity (hepatic necrosis), and arrhythmias.
Which drug is used to treat malignant hyperthermia?
Dantrolene – It decreases calcium release from the sarcoplasmic reticulum, relaxing muscles.
What are the advantages and disadvantages of Nitrous Oxide (N₂O)?
Advantages: Good analgesic, rapid onset/recovery, non-irritating (safe for asthmatics & pregnant people).
Disadvantages: Low potency, no muscle relaxation, hypoxia risk when removed.
Which inhaled anesthetic has the fastest recovery time but cannot be used for mask induction?
Desflurane – Rapid recovery, but pungent and can cause airway irritation.
What are the four commonly used intravenous general anesthetics?
Propofol, Ketamine, Etomidate, Methohexital.
What is the primary advantage of Propofol?
Rapid onset and recovery, commonly used for both induction and maintenance of anesthesia.
What is the main disadvantage of Propofol?
Hypotension, respiratory depression, pain at injection site (often administered with lidocaine).
What makes Ketamine unique as an anesthetic?
It produces dissociative anesthesia (patient appears awake but unaware), excites the heart (increases BP & HR), and causes bronchodilation.
What are the major side effects of Ketamine?
Hallucinations, increased cerebral blood flow, and potential for abuse (related to PCP, “angel dust”).
Which intravenous anesthetic is best for patients at risk of hypotension and bronchospasm?
Ketamine – It maintains cardiovascular stability and bronchodilates.
What is the primary clinical use of Etomidate?
Induction of anesthesia, especially in hemodynamically unstable patients, due to minimal cardiovascular effects.
Why is Etomidate not used for anesthesia maintenance?
It suppresses adrenocorticosteroid production, leading to increased mortality risk with prolonged use.
What are the most commonly used opioid anesthetic adjuncts?
Fentanyl, Sufentanil, Alfentanil, Remifentanil, Morphine – Used for analgesia during and after surgery.
