This document discusses various methods for monitoring the depth of anesthesia. It begins by introducing the importance of ensuring adequate depth of anesthesia while avoiding overdose. It then describes some clinical signs of light anesthesia and various EEG-based monitors including BIS, entropy, PSI, and Narcotrend. These monitors analyze EEG patterns to provide a numerical index of the patient's level of consciousness during anesthesia. The document notes that EEG monitors are not suitable for agents like ketamine that do not depress the EEG. It concludes by mentioning some other potential indicators of anesthetic depth like monitoring nociception and auditory-evoked responses.