This clinical trial aims to establish whether reversing remimazolam sedation with flumazenil can prevent postoperative neurocognitive disorders in patients undergoing total hip replacement surgery. The main questions it aims to answer are:

• Does administering flumazenil after surgery lead to an improvement in cognitive function (measured by the MoCA scale) at 24 hours post-operation compared to a placebo?
• Does this intervention reduce the incidence of postoperative delirium within the first 48 hours? Researchers will compare flumazenil to a placebo (0.9% saline solution) to see if actively reversing sedation leads to better cognitive outcomes and a lower incidence of delirium.

Participants will:

• Undergo a planned total hip replacement surgery under spinal anesthesia.
• Receive sedation with remimazolam during the operation.
• At the end of the surgery, receive an intravenous injection of the study drug (flumazenil) or a placebo.
• Undergo assessments for cognitive function (using the MoCA scale) and delirium (using the 4AT scale) before and at multiple time points after the surgery.
• Complete a questionnaire about their quality of recovery (QoR-15).

Inclusion Criteria:

• Patient qualified for elective, primary, unilateral, total hip replacement.
• Patient assessed on the ASA I-III scale.
• MoCA score obtained during screening ≥ 23 points (to exclude patients with significant pre-existing cognitive impairment).
• Ability to understand information about the study and express informed, written consent to participate.

Exclusion Criteria:

• Known hypersensitivity or allergy to benzodiazepines, flumazenil, local anesthetics
• Contraindications to spinal anesthesia or patient refusal of this anesthesia technique.
• Severe liver dysfunction.
• History of epilepsy or seizures
• Chronic (daily use for > 2 weeks in the last 3 months) use of benzodiazepines or non-benzodiazepine hypnotics (so-called "Z" drugs: zolpidem, zopiclone, zaleplon).
• Alcohol abuse defined as regular consumption of more than: in men: 40 g of pure ethanol at a time; in women: 20 g of pure ethanol at a time, or a history of psychoactive substance dependence.
• Planned revision hip arthroplasty or bilateral surgery.
• Significant neurological or psychiatric diseases that may affect the assessment of cognitive function.
• The need for sedative premedication.