Study of the: Effect of Head Rotation in Prone Position on Regional Cerebral Oxygen Saturation.

Observation Study of the: Effect of Head Rotation in Prone Position on Regional Cerebral Oxygen Saturation (rSO2) in Anesthetized Patients.

The purpose of this study is to determine whether head rotation in prone positon affects regional cerebral oxygenation (rSO2)in anesthetized patients undergoing lower back surgery.

Inclusion Criteria:

• Lower back surgery
• Age [18-80]
• ASA group I-III
• free and painless movement of the neck (including flexion, extension and rotation)

Exclusion Criteria:

• Pain during neck movement as mentioned under inclusion criteria.
• known history of cervical spine pathology or pathology of central nervous system including cerebrovascular disease
• any stenosis of the carotid vessels or known symptoms associated with such
• BMI > 35