Abstract: Evaluating Electroencephalogram (EEG) data includes receiving initial EEG signals for a patient being subjected to an anesthetic agent associated with a first probability for responding to surgical stimulation; identifying at least one expected pathway of EEG signals, wherein the at least one expected pathway of EEG signals comprises a time-ordered series of expected EEG signals for the patient based on the anesthetic agent; receiving a subsequent EEG signal for the patient after a change to a level of the anesthetic agent has occurred; based on the change to the level of the anesthetic agent, determining a change from the first probability to a second probability for responding to surgical stimulation; and calculating an amount of increase to an analgesic agent to administer to the patient to return substantially to the first probability for responding to surgical stimulation.