Relationship Between Bispectral Index, EEG Features, and Propofol Effect-site Concentration in Young and Elderly Patients.

Propofol will be started at a rate of 15-20 mg/kg/hr in patients \>65 years and 20-25 mg/kg/hr in younger patients (\<65 years) until a suppression rate (SR) is achieved. If not, can be increased by 5 mg/kg/hr every 5 minutes up to 25 mg/kg/hr in the elderly group and 30 mg/kg/hr in the younger group or after 15 minutes have passed. When the SR appears, propofol infusion will be stopped. Then restarted at half of the initial rate. Maintenance of anesthesia will be guided by Sedline Monitor to maintain an alpha band present in the spectrogram and SEF95 between 8-12 Hz. BIS monitor will be covered. Both EEG signals (Sedline and BIS) will be registered simultaneously until the patient's extubation.