A patient undergoes differential spinal block for evaluation of persistent foot pain. If the pain returns coincident with a decrease in skin temperature, which of the following is the most appropriate conclusion?
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 patient with a fasting blood glucose concentration of 100 mg/dL undergoes a four-hour operation under general anesthesia without intraoperative administration of glucose. On emergence the most likely finding will be
A 40-year-old patient has pain following injection of 8 ml of thiopental 2.5% through a right radial artery catheter. His hand remains pink. Which of the following is the most appropriate next step?
(A) Injection of lidocaine through the catheter
(B) Injection of nitroglycerin through the catheter