The association of general anesthesia and of thoracic epidural anesthesia is used in thoracic surgery with a demonstrated benefit on the risk of postoperative respiratory complications.

The objective of the study is to analyze the influence of thoracic epidural administration of chirocaine (5 mg/ml) on the administration of anesthetic agents (propofol and remifentanil), these drugs being administrated using a closed-loop system with the Bispectral Index as the controller.

Two groups of patients are compared:

• one group will receive general anesthesia and thoracic epidural administration of saline. Chirocaine will be administered before patient's awakening,
• one group will receive general anesthesia and thoracic epidural administration of chirocaine (5 mg/ml).

In both groups, the closed-loop system ensures that le depth of anesthesia is similar in both groups.

Inclusion Criteria:

• patients undergoing a thoracotomy under general anesthesia and epidural anesthesia

Exclusion Criteria:

• age lower than 18 years,
• pregnant woman,
• psychotropic treatment,
• central neurological disorder or lesion cerebral,
• allergy to propofol or to a muscle relaxant,
• refusal or contra-indication of epidural anesthesia,
• severe emphysema,
• coronary disease,
• treatment with a beta-blocker or a vasoactive drug.