questions 3

Intravenous Anesthetics

Topic updated on 06/12/17 7:44pm

Snapshot
  • A 36-year-old man presents to the hospital for an elective bariatric procedure. The patient followed instructions not to eat for a given amount of hours prior to the surgery. While on the surgical table, the anesthesiologist induces anesthesia with an intravenous bolus of propofol, along with a number of other agents used.
Introduction
  • General anesthesia
    • is a central nervous system (CNS) depressive state that is reversible and provides
      • analgesia
      • sedation and decreased anxiety
      • amnesia and impaired consciousness
      • relaxation of skeletal muscle
      • prevention of reflexes 
    • can be divided into
      • intravenous anesthesia
      • inhaled anesthesia
  • Intravenous (IV) anesthesia
    • causes a rapid induction of anesthesia
      • when the anesthetic enters the blood, a portion of it binds to plasma proteins (bound) while the rest are unbound
        • the binding ability of the IV anesthetic is dependent on numerous factors, such as
          • drug ionization
          • lipid solubility
      • after entering the venous blood and goes to the heart and into the cerebral circulation
        • the anesthetic enters the brain at a rate that depends on
          • arterial concentration of unbound drug
          • lipid solubility
          • degree of ionization
        • the higher the arterial concentration of the unbound drug, lipid solubility, and nonionized molecules
          • the faster the anesthetic enters the brain
      • eventually, the anesthetic leaves the CNS (redistribution), resulting in
        • recovery from the IV anesthetic
Intravenous Anesthetic
 
Intravenous Anesthetic
Drugs
Clinical Use
Comments
Thiopental
  • Induction of anesthesia
  • Short surgical procedures
  • A short acting barbiturate that
    • has a high lipid solubility
    • is a potent anesthetic
    • is a weak analgesic
    • has a rapid redistribution; thus,
      • it rapidly diffuses out of the brain
  • May cause
    • apnea
    • laryngospasm
    • bronchospasm
Midazolam
  • Induction of anesthesia
  • Endoscopy
  • Can result in
    • temporary forms of anterograde amnesia
    • post-operative respiratory depression
  • Treat overdose with flumazenil
Opioids
  • To induce analgesia
  • Fentanyl is commonly used
  • Can result in
    • hypotension
    • respiratory depression
    • muscle rigidity
Etomidate
  • Induction of anesthesia
  • Can reduce
    • adrenal steroid production
      • which can result in
        • acute adrenal crisis
Ketamine
  • Induction of a dissociative anesthetic state
  • Ketamine
    • is a NMDA receptor antagonist
    • increases central sympathetic outflow, which in turn increases
      • blood pressure
      • cardiac output
      • bronchodilation
    • increases cerebral blood flow
    • may result in hallucinations
    • prevents opioid-induced acute tolerance
Propofol
  • Induction and/or maintenance of anesthesia
  • Decreases blood pressure
  • Reduced intracranial pressure
  • Low incidence of post-operative nausea and vomiting
  • Potentiates GABAA
 


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(M1.NE.4671) A 65-year-old man with metastatic lung cancer has been experiencing severe, unremitting pain. He has required escalating doses of oral morphine, but is now having dose limiting side-effects. His pain management team recommends using a medication that can reduce his opioid need through interaction with the NMDA-receptor. Which of the following was the most likely recommended agent?
Topic Review Topic

1. Propofol
2. Ketamine
3. Fentanyl
4. Ketorolac
5. Midazolam

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