Intravenous Anesthetics

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