Figure 38-19 Effects of etomidate on somatosensory evoked potentials. A, The tracings were obtained from a mildly mentally impaired patient with severe kyphoscoliosis during the early maintenance phase of anesthesia using isoflurane and fentanyl. B, The tracings were obtained after discontinuing isoflurane and institution of an etomidate infusion at 20 µg/kg/min. Notice the dramatically increased amplitude and clarity of the signal in the cortical channels (arrows), which are both recorded with the same amplification scale.