This is a prospective, observational study, aimed to establish changes of bispectral bilateral system in both cerebral hemispheres during a total intravenous anaesthesia during breast surgery in the woman. By placing two Bispectral bilateral sensors (BIS), one on both frontal lobes, and another on both parietal lobes, we wanted to evaluate differences between frontal and parietal areas, when the patient is awake and during the anaesthetic procedure.

Inclusion Criteria:

• Aged more than 18 years old.
• Scheduled for general anaesthesia.
• Agree to participate(signed inform consent).

Exclusion Criteria:

• Neurological disease.
• Cognitive impairment.
• Egg allergy.
• Severe disease or condition that could potentially interfere with interpretation of tests.

Patients with alopecia scheduled for general anaesthesia.