Group-level power spectrogram, generated by concatenating the nine clinically relevant epochs and averaging median power values (decibels, dB) across all available patients. For each patient, the power spectrogram was averaged over prefrontal (Fp1, Fp2), frontal (F5, F6, Fz), and parietal (P5, P6, Pz) channels. LOC, loss of consciousness; PACU, postanesthesia care unit; pre-oxy, preoxygenation; pre-extub, preextubation; post-extub, postextubation.