A 64-year-old, 87-kg 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 54-year-old woman who is scheduled to undergo emergency exploratory laparotomy takes warfarin sodium for anticoagulation. Prothrombin time is 19 sec (control 12 sec). Which of the following agents is most appropriate to reverse the effects of warfarin?
After termination of cardiopulmonary bypass, a patient who is chronically digitalized receives digoxin 0.5 mg in error. An ECG shows sinus bradycardia with intermittent sinus arrest; blood pressure is 90/60 mmHg. Which of the following drugs is contraiindicated in this patient?
A 26-year-old woman is hospitalized in early labor at 38 weeks' gestation. Vaginal bleeding occurred prior to admission. Systemic blood pressure remains 140/80 mmHg during intravenous infusion of fluids. Which of the following factors would contraindicate epidural anesthesia for labor at this time?
(A) Early fetal heart rate decelerations
(B) Hematocrit of 29%
(C) Blood pressure of 110/75 mmHg when sitting
(D) Platelet count of 100,000/mm3
(E) Increased respiratory rate
C
A healthy, but obese, 110-kg woman is scheduled for gastric stapling. Compared with that required at her ideal weight, the dose of thiopental required for anesthetic induction would likely be increased because of changes in