Available evidence suggests that there is no significant difference in the incidence of postoperative cognitive dysfunction POCD when general anaesthesia and regional anaesthesia are compared[13, 14]. To the knowledge of the investigators , no studies are examining the effects of ketamine on cognitive outcomes in the setting of spinal anesthesia.

Thus, the purpose of this study was to compare the cognitive status, as assessed by the SPMSQ, of elderly patients undergoing orthopaedic surgery under spinal anaesthesia before and after ketamine administration. The authors hypothesized that patients receiving ketamine would exhibit better cognitive performance.

Inclusion Criteria:

• patients scheduled for orthopaedic surgery under spinal anaesthesia.
• ASA physical status I to II.

Exclusion Criteria:

• Patients with a history of psychosis, schizophrenia, nephropathy, uncontrolled blood pressure, uncontrolled hepatic disorders, or allergy to ketamine.
• Patients With moderate to severe depression according to Yesavage abbreviated Geriatric Depression Scale,
• Patients presented with postoperative delirium or required medications other than study drugs.
• Ketamine administration is contraindicated.