Fig. 4. Cortical somatosensory evoked potential responses at various minimum alveolar concentration (MAC) levels of halothane (a ), enflurane (b ), and isoflurane (c ). (Redrawn with permission from Peterson DO, Drummond JC, Todd MM: Effects of halothane, enflurane, isoflurane, and nitrous oxide on somatosensory evoked potentials in humans. Anesthesiology 1986; 65:35–40.)