An otherwise healthy 16-year-old girl is undergoing posterior spinal fusion for thoracolumbar scoliosis. During the procedure, the most likely cause of a marked decrease in the amplitude of the somatosensory evoked potentials after stimulation of the posterior tibial nerve is
(A) administration of fentanyl 30 jag /kg for induction
(B) administration of isoflurane 1.3 MAC for maintenance
(C) administration of vecuronium 0.15 mg/kg
(D) a decrease in body temperature from 37 to 35°C
A newly developed inhalational anesthetic has a blood-gas partition coefficient of 0.2. Which of the following statements best describes this drug compared with isoflurane?
(A) MAC is lower
(B) The difference between Fa and Fl during maintenance of anesthesia is greater
(C) Time to emergence is shorter
(D) Rapid induction requires greater overpressure
(E) Equilibrium in a circle system with the same flow of fresh gas is slower
(D) Inhibiting sodium ion influx across the neuronal cell membrane
(E) Opening sodium channels at the nodes of Ranvier
D
A 62-year-old man is scheduled for coronary artery bypass grafting. During induction of anesthesia with fentanyl, high peak inspiratory pressures occur with manual ventilation, and peripheral oxygen saturation decreases from 100% to 94%. The most appropriate management is administration of
A radial artery catheter is to be used for blood pressure measurement during a sitting craniotomy. When zeroing the transducer, which of the following describes the best levels for placement of the transducer and opening of the system to air? (Transducer, Opening to Air)
A 50-year-old woman with subarachnoid hemorrhage and left hemiparesis undergoes clipping of a right cerebral aneurysm. On the second postoperative day, mental status deteriorates. Blood pressure is 110/70 mmHg. A cerebral angiogram shows vasospasm. The most appropriate management is to
(A) administer dexamethasone
(B) administer mannitol
(C) administer phentolamine
(D) expand intravascular volume
(E) intubate and hyperventilate to a PaC02 of 28 mmHg
D
Meperidine has a more rapid onset of action than morphine following intravenous injection because of its