An 87-kg 64-year-old woman in good general health is undergoing a right knee arthroplasty while in the supine position with general anesthesia consisting of enflurane 2% and nitrous oxide 50% in oxygen. She is breathing spontaneously through a 7-mm endotracheal tube. During the first 30 minutes of the procedure, the arterial oxygen saturation measured by pulse oximetry decreases from 98% to 92%. The most likely cause of the desaturation is
(A) decreased functional residual capacity
(B) diffusion hypoxia
(C) hypercarbia
(D) increased airway resistance produced by the endotracheal tube
(E) inhibition of hypoxic pulmonary vasoconstriction
A
To detect the delivery of hypoxic gas mixture, the optimal location for an oxygen analyzer in this circle is
During cardiopulmonary bypass at a nasopharyngeal temperature of 28°C and a hematocrit of 20%, temperature-corrected PaCO2 is 50 mmHg and uncorrected PaCO2 is 60 mmHg. The most appropriate management is to
(A) administer additional opioid
(B) administer packed red blood cells to increase hematocrit to 25%
A 24-year-old man is undergoing induction of general anesthesia prior to appendectomy. During laryngoscopy, he regurgitates a large amount of bilious material. An endotracheal tube is inserted; aspiration shows bile-stained fluid. Which of the following is the most appropriate next step in management?
(A) Infusion of a loading dose of aminophylline
(B) Intravenous administration of broad-spectrum antibiotics
(C) Lavage of the tracheobronchial tree with saline solution
(D) Radiograph of the chest
(E) Proceeding with the operation
E
The second gas effect refers to
(A) acceleration of rise in alveolar concentration of a gas caused by concomitantly administered nitrous oxide
(B) change in volatile anesthetic vaporizer output with the addition of nitrous oxide to the carrier gas mixture
(C) decrease in MAC of a volatile anesthetic by addition of nitrous oxide
(D) expansion of gas-containing spaces by addition of nitrous oxide
(E) rapid diffusion of nitrous oxide from pulmonary capillary blood into alveolar gas at the termination of anesthesia
During active labor, 10 ml of bupivacaine 0.5% with epinephrine 1:200,000 is administered epidurally. Fifteen minutes later, maternal blood pressure is 70/50 mmHg and heart rate is 70 bpm; fetal heart rate is 90 bpm for 45 seconds, with loss of beat-to-beat variability. The most likely explanation for the fetal vital signs is
Which of the following is more likely to occur with use of trimethaphan to induce hypotension than with use of nitroprusside?
(A) A predictable decrease in mean arterial pressure
(B) Increased mixed venous P02
(C) Increased serum lactate concentration
(D) Mydriasis
(E) Reflex tachycardia
D
A 2500-g, 12-hour-old infant is tracheally intubated and mechanically ventilated at a rate of 20/min with an FiO2 of 0.4 and peak inspiratory pressure of 25 cmH2O. At birth, amniotic fluid was meconium stained and Apgar scores were 2 and 7. The most recent arterial blood gas levels are PaO2, 50 mmHg, PaCO2, 55 mmHg, and pH 7.20. The most appropriate management is to
(A) administer sodium bicarbonate
(B) begin intravenous infusion of prostaglandin E,