Alteration of Blood-Brain-Barrier Permeability at Loss of Consciousness in Delirious Patients Recorded With Direct-Current Electroencephalography (ACDC)

With this trial we aim to characterize the intraoperative signatures of the Direct-Current-Electroencephalogram (DC-EEG) of elderly patients developing a PostOperative Delirium (POD) compared to patients who do not develop a POD. We hereby intend to gain a better understanding of the electrical potential at the blood-brain-barrier (measured with DC-EEG) during general anaesthesia. Second, we want to study the effect of age on the DC-EEG by comparing a younger (18-30y) to an elderly cohort (\>70). Third, we aim to couple the DC-EEG signatures to blood sample analysis in order to understand the relationship between metabolic, inflammatory and vascular reaction with the intraoperative DC-EEG.

In order to study the intraoperative DC-EEG signatures of elderly patients coupled with lab data to evaluate the role of the age-dependent blood-brain barrier (BBB) dysfunction in general anesthesia and its meaning in POD pathophysiology following protocol will be followed:

1. On the day of the surgery the 21 DC-EEG sintered Ag/AgCl (silver chloride) electrodes will be placed before the start of anesthesia following the 10-20-system.
2. The first blood sample will be collected via the routinely placed intravenous catheter.
3. During the induction of anesthesia special care will be given to the exact time of loss of consciousness (LOC), defined with the suppression of the lid closure reflex.
4. Markers will be set at important time points of the anesthetic care (Baseline, start of analgesia/anesthesia, LOC, intubation, beginning of surgical procedure, end of anesthesia, regain of consciousness, extubation, admission recovery room).
5. Shortly after consciousness has vanished (5-10 minutes), a second blood sample will be drawn.
6. The DC-EEG recording will last until one hour after arrival at the recovery room, during which NuDesc score will be assessed every 15 minutes.
7. A third blood sample is to be collected in the recovery room. In the five days following surgery patients will be visited in the morning and in the evening to screen delirious symptoms with the help of standardized scores (NuDesc, DSM V, DDS). If patients are staying on the intensive care unit the CAM-ICU will be used.

Blood sample analysis will include blood cells count, electrolytes, inflammatory markers, cholesterols, proteins, structural BBB markers and markers of neuronal damage.

Eligibility Criteria:
Inclusion Criteria:

* Patients aged \>70 years OR between 18 and 30
* Planned operation time \>1 hour
* Expected hospital treatment period of 5 days,
* Anesthesia induction, anesthesia maintenance with either Propofol or an inhalative anesthetic agent as Sevoflurane or Desflurane,
* The ability to give informed consent

Exclusion Criteria:

* Age under 18 or between 31 and 69
* Patients with a history of neurological or psychiatric disorders
* Planned neurosurgery
* Current medication of tranquilizers / antidepressants
* Isolation of patients with multi-resistant Bacteria
* Inability of the patients to speak and/or read German
* Intraoperative use of ketamine, N²O, Etomidate or Dexmedetomidine
* Participation in a prospective interventional trial