Chapter 11: Anesthetic Agents and Therapeutic Gases
Current evidence supports the view that most intravenous general anesthetics act predominantly through
b. D2 dopamine receptors.
d. α2-adrenergic receptors.
e. β1-adrenergic receptors.
Answer is c. Current evidence supports the view that most intravenous general anesthetics act predominantly through GABAA receptors and perhaps through some interactions with other ligand-gated ion channels such as NMDA receptors and two-pore K+ channels.
Termination of anesthesia after a single bolus of a parenteral anesthetic primarily reflects
a. redistribution out of the CNS.
b. metabolism by the liver.
c. excretion by the kidney.
d. enhanced protein plasma protein binding.
e. hydrolysis by plasma esterases.
Answer is a. Termination of anesthesia after a single bolus of a parenteral anesthetic primarily reflects redistribution out of the CNS rather than metabolism (see Figure 11-1).
Figure 11-1. Thiopental serum levels after a single intravenous induction dose. Thiopental serum levels after a bolus can be described by 2 time constants, t1/2 α and t1/2 β. The initial fall is rapid (t1/2α<10 minutes) and is due to redistribution of drug from the plasma and the highly perfused brain and spinal cord into less well-perfused tissues such as muscle and fat. During this redistribution phase, serum thiopental concentration falls to levels at which patients awaken (AL, awakening level; see inset—the average thiopental serum concentration in 12 patients after a 6 mg/kg intravenous bolus of thiopental). Subsequent metabolism and elimination is much slower and is characterized by a half-life (t1/2 β) of more than 10 hours. (Adapted with permission from Burch PG, and Stanski DR, The role of metabolism and protein binding in thiopental anesthesia. Anesthesiology, 1983;58:146-152. Copyright Lippincott Williams & Wilkins. http://lww.com.)
A 23-year-old man is having outpatient surgery for a torn anterior cruciate ligament as the result of a skiing injury. He is most likely to receive which of the following drugs as a parenteral anesthetic?