0933 Dreaming Under Anesthesia Occurs During Pre-emergence State

Abstract Introduction Dreaming during anesthesia is defined as any recalled experience that occurs between induction and the first moment of consciousness upon awakening. It is a commonly reported phenomenon in the perioperative period, just like dreaming during natural sleep. It has also been reported that general anesthesia with propofol often results in dreams with positive content, which influences emotions after awakening. However, the details of when and under what conditions the brain undergoes dreaming experiences during anesthesia remain poorly understood. In addition, the homology between dreaming under anesthesia and spontaneous sleep is yet to be uncovered. Herein, we aimed to investigate the relationship between EEG and dreaming experiences under general anesthesia. Methods All participants underwent surgery under general anesthesia with propofol at Stanford University Hospital between 2021 and 2022. Standard ASA monitors and Sedline EEG electrodes at the frontal area were recorded during surgery, and the presence and content of dreaming experiences were interviewed immediately after awakening from anesthesia. The data from thirty-four patients (52.5±15.9 yrs.) who reported dreaming and twenty-eight patients (48.8±13.4 yrs.) who did not report dreaming after emergence from anesthesia were analyzed. Time-frequency analysis was performed on EEGs, and parameters between dreamers and non-dreamers were compared. Results The pre-emergence state from the steady state of anesthesia to extubation was significantly longer in the Dreamer group (17.1±9.3 min vs. 9.1±8.6 min, d=0.8, p=0.01). During the pre-emergence state, a sharp decrease in frontal alpha-power and a sharp increase in Beta/Gamma power were observed. Conclusion The results suggest that dreaming occurs in the pre-emergence state between deep anesthesia and awakening. The finding that this state is characterized by a reduction in frontal alpha oscillation, which is considered to reflect the activity of the thalamocortical loop, provides insight into the neural basis of dreaming, nightmares, and consciousness. Support (if any)