The intravenous administration of anesthetic agents by a controller automatically-guided by an index of cerebral activity (i.e. the bispectral index) decreases the incidence of postoperative delirium, compared with an inhalational anesthesia.

Scientific background Postoperative delirium (POD) is a common complication occurring in 5 to 50 % of elderly patients following an operation. Delirium is a serious complication leading to many medical as well as social and economical consequences. Several studies suggest that, both, the choice of anesthetic agents and the conduction of anesthesia might decrease the incidence of POD.

Objectives Study goal and primary aim: the intravenous administration of anesthetic agents by a controller automatically-guided by an index of cerebral activity (i.e. the bispectral index) decreases the incidence of POD, compared with an inhalational anesthesia.

The primary aim of the present study (i.e. incidence of POD) will be assessed by the Nursing Delirium Screening Scale (NDSS).

Secondary aims:

Secondary aim 1: Assessment of a potential difference on the incidence of PONV between the 2 groups of patients (i.e. intravenous vs. inhaled) by comparison of the number of episodes of nausea and vomiting and the need to treat this complications, between both groups.

Secondary aim 2: study if the difference of in the impairment of cognitive function might be correlated either with the type of drugs used to conduct anesthesia or with the control the index of cerebral activity (i.e. the BIS). The respective influences of the control of the index of cerebral activity (i.e. the BIS) and of the anesthetic drugs on the occurrence of postoperative cognitive dysfunctions (POCD) will be assessed by comparing cognitive function tests on matched groups on the percentage of time spent in different ranges of values of the cortical index Population of patients Patients of 60 years old or more, having given their written informed consent and who should undergo a surgical procedure of at least one hour.

Inclusion criterion

Patients will be included in the study if:

• They are 60 years old or older,
• They have given their written informed consent,
• They have to undergo a surgical procedure of one hour or longer. Non-inclusion criterion

Following patients will non be eligible for the current study:

• Pregnant women,
• Patients presenting a contra-indication to the monitoring of cerebral activity (i.e. intracranial surgery, neuroleptic or anti epileptic medications, pace maker),
• Patients presenting any allergy to propofol and or remifentanil,
• Patients under guardianship. Experimental protocol Information and inclusion of patients during the preoperative anesthetic assessment consultation First assessment of the NDSS at patient arrival in the operating room Randomization prior to the induction on the anesthesia Second NDSS just before patient leaving of PACU Recording of all PONV event as well as any administration of anti emetic drug

Number of subjects: 1000 Number of center: 4 Duration of the research: 36 months

Statistical Analysis: Sequential group analysis. The preoperative and postoperative NDSS test will be analyzed with an ANOVA for repeated-measure and multiple-comparison.

The main criterion will be analyzed with a Kaplan-Meier survival analysis on the global data and with a Cox regression that will take into account the qualitative factors represented by the type of anesthesia

Description of the Nursing Delirium Screening Scale (NDSS) that is a validated scale to assess POD at the bedside.

Five areas are assessed: disorientation, inappropriate behavior, inappropriate communication, illusions or hallucinations, and psychomotor retardation Description A screening tool designed for nurses to use at the end of their shift to identify patients with delirium, derived from the Confusion Rating Scale (CRS). Raters reference behaviors that they have witnessed in the patient or that the patient'snurse has witnessed during their shift to score the NDSS.

The NDSS can be rated one or more times daily.

Scoring information Each feature is scored on 0-2 based on severity, with 0=absent, 1=mild, and 2=severe.

Positive NDSS is score ≥ 2, maximum total score is 10.

Inclusion Criteria:

• age > 59 year
• Informed written consent before enrolment;
• Procedure duration > 60 min.
• Speaking French
• Possible contact one-month following surgery

Exclusion Criteria:

• Contraindication of brain monitoring (intracranial surgery), pace-maker.
• Propofol or remifentanil allergy.
• Patients under guardianship