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Chapter 11: Anesthetic Agents and Therapeutic Gases

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Current evidence supports the view that most intravenous general anesthetics act predominantly through

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a. 5-HT receptors.

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b. D2 dopamine receptors.

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c. GABAA receptors.

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d. α2-adrenergic receptors.

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e. β1-adrenergic receptors.

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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.

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Termination of anesthesia after a single bolus of a parenteral anesthetic primarily reflects

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a. redistribution out of the CNS.

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b. metabolism by the liver.

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c. excretion by the kidney.

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d. enhanced protein plasma protein binding.

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e. hydrolysis by plasma esterases.

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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).

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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.)

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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?

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a. Phenobarbital

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b. Diazepam

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c. Propranolol

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d. Lidocaine

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e. Propofol

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Answer is e. Propofol is the most commonly used parenteral anesthetic in the United States. Propofol is advantageous for procedures where rapid return to a preoperative mental status is desirable.

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A 35-year-old woman is anesthetized with desflurane for outpatient surgery. The induction with desflurane is rapid because desflurane is not very soluble in fat and because desflurane

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a. has a high blood:gas ...

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