The goal of this observational study is to find out how changes in body position during surgery might affect brain monitoring results in patients who are under general anesthesia.The main question it aims to answer is:
\- Does patient positioning have an impact on Bispectral Index (BIS) and Nociception Level (NOL) index monitoring (which are values of awareness in anesthesized patients).
Participants will undergo their surgery as planned, except for these extra features:
* Extra monitors placed to check brain activity, pain response, and brain oxygen levels. * Before the surgery, while the patient is asleep, the patient's table will be moved into two different positions for 2 minutes each to see if the values on the monitor change.
Participants will then have to answer a short questionnaire after surgery about their memories before and after the anesthesia.
Fully consented, adult patients above 18 years old;
Supine positioning during the surgery;
Surgery requiring patient positioning with Vacuform mats.
Patient with Body Mass Index (BMI) ≥ 35;
Patients over 80 years old.