A correlation between deep anesthesia (defined as time with Bispectral Index (BIS) lower than 45) and death within 1 yr after surgery has previously been reported. In order to confirm or refute these findings, the investigators have designed a study which compares two methods of administration for total intravenous anesthesia (propofol and remifentanil):

• manual administration: the anesthesiologists are instructed to maintain the BIS value between 40 and 60.
• closed loop administration: an algorithm is used to maintain the BIS value between 40 and 60.

Based on previous studies, the amount of time that BIS is maintained above 40 is greater when anesthetics agents are administered using closed loop compared with manual administration.

Inclusion Criteria:

• American Society of Anesthesiology patient classification status I, II and III
• patients aged between 50 and 85 years old
• born in France
• surgical procedures lasting more than one hour

Exclusion Criteria:

• American Society of Anesthesiology patient classification status IV
• patients born out of France
• pace-maker
• surgical procedure on the skull or avoiding an adequate positioning of the bispectral index electrode dementia, history of central nervous system disease (tumor, vascular event, Parkinson disease, ...)
• psychiatric illness (severe depression or psychosis), patients receiving a psychotropic treatment
• anesthesia performed during the year before inclusion in this study except for diagnostic procedures
• allergy to propofol, soja, peanuts, or to sufentanil, remifentanil, or morphine, to a myorelaxant or to an excipient,
• hypersensibility to sufentanil, to remifentanil, or to other derivate of fentanyl