A 55-year-old woman who is scheduled to undergo carotid endarterectomy has a history of essential hypertension and chronic obstructive pulmonary disease. Over a 30-minute period beginning one hour after induction of general anesthesia, Sp02 decreases from 99% to 95%. During that time, she has received fentanyl 100 mcg, isoflurane 1%, nitrous oxide 49.5%, oxygen 49.5%, and a nitroglycerin infusion to maintain blood pressure at approximately 160/95 mmHg. Which of the following is the most likely cause for the decline in oxygen saturation?
(A) Decreased cardiac output
(B) Increased dead space ventilation
(C) Inhibition of hypoxic pulmonary vasoconstriction
During acute normovolemic hemodilution in an adult, which of the following compensatory mechanisms is most important in maintaining tissue oxygenation?
When using apneic oxygenation during endoscopy in a normothermic patient, PaC02
(A) increases at a rate inversely proportional to oxygen flow rate
(B) increases at a rate of 8 + 0.5 mmHg per minute
(C) increases at the same rate that Pa02 decreases
(D) equals mixed venous PC02 after one minute
(E) is increased by airway obstruction
D
A 35-year-old patient, who is ASA physical status 1, is scheduled for open cholecystectomy under general anesthesia. Which of the following end-tidal concentrations would most likely block the adrenergic response to skin incision?
(A) Enflurane 1.7%, oxygen
(B) Isoflurane 1.2%, oxygen
(C) Enflurane 0.6%, nitrous oxide 70%, oxygen
(D) Halothane 0.4%, nitrous oxide 70%, oxygen
(E) Isoflurane 1.0%, nitrous oxide 70%, oxygen
E
Which of the following is most responsible for the duration of action of local anesthetics?
During laser excision of vocal cord polyps in a 5-year-old boy, dark smoke suddenly appears in the surgical field. The trachea is intubated and anesthesia is being maintained with halothane, nitrous oxide, and oxygen. The most appropriate initial step is to