Permanent and temporary cognitive impairment in the perioperative period is of great importance to patients. Hypoperfusion due to the intraoperative hypotension is often mentioned as a possible cause of postoperative cognitive dysfunction.

All patients aged above 60 years undergoing planned spinal surgery in the prone position in the duration of 1-3 hours under general anesthesia will be included in the study. In group L (liberal), the value of blood pressure will be corrected with the change of mean arterial pressure (MAP) ± 25% patient's mean arterial pressure, and group R (restrictive) with the change of MAP ± 10%. Cognitive dysfunction tests will be executed on the day before the surgery, two hours after the surgery and on the third postoperative day. Anesthesia will be managed according to the standardised protocol. Concentration of desflurane will be adjusted according to entropy values (target 40-50). Analgetics will be applied according to surgical pleth index (SPI) values. Sufentanil will not be applied in the last 15 minutes. Extubation will be performed at the operating theatre when meeting all extubation criteria including train of four ratio (TOFR) above 92%. Neither syntophyllin, nor pharmacological decurarization (syntostigmin) will be applied to the patients.

Inclusion Criteria:

• GCS 15
• ASA risk I - III
• planned spinal surgery in the prone position
• duration of the procedure of 1-3 hours

Exclusion Criteria:

• hypertension above 180/100 torr preoperatively
• blood pressure below 130/80 torr preoperatively