Ketamine and Postoperative Cognitive Dysfunction

The design consists in a prospective multicenter randomized blinded placebo-controlled trial in elderly patients undergoing elective orthopaedic surgery. Patients will be informed at the pre-anaesthetic consultation, 7 to 30 days before surgery. They will be randomized the day before surgery. Cognitive and depressive status at baseline will be assessed precisely the day pior to surgery with cognitive tests. Self-administered scores will be recorded to evaluate depression, anxiety, and quality of life. At the day of surgery, patients in the experimental group will receive a bolus of low intravenous dose (sub-anaesthetic) 0.5 mg/kg ketamine following induction of anaesthesia. Patients in the control group will receive a bolus of an intravenous normal saline solution following induction of anaesthesia. From D0 (2 hours after surgery end) to D7 or discharge from the hospital if earlier, delirium, pain, adverse clinical and psychiatric events will be measured and recorded. Cognitive functions, neuropathic pain, depression, anxiety and quality of life will be assessed at D7 or discharge from the hospital if earlier and D90. Inflammatory markers will be measured before surgery, at D1, D7 or discharge from the hospital if earlier and D90.