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Chapter 26: General Anesthesia, Monitored Anesthetic Care, and Sedation

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Guedel classically described four stages of anesthesia for inhalation anesthetics. Which of the following findings occurs only in the stage of “surgical anesthesia”?

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(A) unconsciousness and amnesia

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(B) apnea

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(C) no movement except respiration

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(D) increased muscular movement

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(E) hypertension and tachycardia

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The answer is C. Although Guedel's four stages and signs of anesthesia are mostly of historic interest, it is still frequently referenced:

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  • Stage 1: awake to unconscious, analgesia increases

  • Stage 2: “excitement” stage to onset of automatic breathing, sympathetic activity (hypertension, tachycardia), purposeless movements, irregular respiration

  • Stage 3: “surgical anesthesia,” regular breathing, stable heart rate and blood pressure, no movement except respiration

  • Stage 4: anesthetic overdose, from cessation of respiration and collapse of circulation to death

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Refs: Hewer CL. The stages and signs of general anaesthesia. Br Med J.1937;2(3996):274–276.

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Urban BW, Bleckwenn M. Concepts and correlations relevant to general anaesthesia. Br J Anaesth. 2002;89(1):3–16.

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During a preoperative consultation, a patient expresses concern about anesthetic awareness for their upcoming surgery. A discussion of risk factors for anesthetic awareness ensues. Which of the following situations has the lowest likelihood of anesthetic awareness?

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(A) trauma surgery

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(B) caesarean section

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(C) maintenance of anesthesia with a BIS number of 60

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(D) maintenance of anesthesia with end-tidal anesthetic gas concentration >0.5 MAC

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(E) maintenance of anesthesia with nitrous oxide (N2O)

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The answer is C. Evidence suggests a maintenance anesthetic using a BIS-guided technique with the BIS titrated to 40 to 60 is effective at preventing awareness (as is an end-tidal anesthetic gas concentration >0.7 MAC). Anesthetic awareness can occur with:

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  • low anesthetic delivery: error or interruption of delivery; use of only N2O for maintenance anesthesia

  • patients with low cardiovascular reserve: pregnancy, hypovolemia, or cardiac failure (caesarean section, cardiac surgery, emergency surgery, trauma surgery)

  • patients with high anesthetic requirement: tolerance to sedative medications (chronic alcohol, benzodiazepine, or opioid use)

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Ref: Miller RD. Miller's Anesthesia, 8th ed. Philadelphia, PA: Elsevier; 2015.

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Sevoflurane is used to perform an inhalation induction on a pediatric patient. Which of the following side effects is most likely?

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(A) laryngospasm

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(B) breath-holding

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