dexmedetomidine infusion or lidocaine infusion starting before induction of intravenous general anesthesia and continue as infusion intraoperative can reduce postoperative cognitive dysfunction incidence (primary outcome), postoperative cognitive dilirium, postoperative pain, opioid consumption, postoperative inflammatory response and postoperative adverse events (secondary outcomes) in elderly patients undergoing ERCP.

Randomization will be achieved using a computer-generated random sequence, and group allocation will be concealed using opaque, sealed envelopes. Both patients and study staff, including those administering the interventions and assessing outcomes will be blinded to the group assignments. The tested syringes will be prepared by the responsible nurse in equal volumes of 50 ml. All data of the patients will be confidential with secret codes and private file for each patient, all given data will be used for the current medical research only.

The prefilled 50 mL syringes will contain either dexmedetomidine 4 µg/mL or lidocaine 10 mg/mL or NaCl 0.9%. Ten minutes before anesthesia induction all patients will receive an IV infusion at a rate of 0.9mL/kg/h for 10 minutes. This rate corresponds to 0.6 µg/kg dexmedetomidine or 1.5 mg/kg lidocaine. Afterwards, all patients will receive an infusion at a rate of 0.15mL/kg/h until the end of procedure; this rate corresponds to 1.5 mg/kg/h of lidocaine or 0.6 µg/kg/h of dexmedetomidine.

Inclusion Criteria: The study will include all patients aged 65 years or older of both sex with an ASA I -II - III (as controlled HTN, controlled DM), (MMSE>24) who scheduled for elective ERCP under total intravenous general anesthesia.

Exclusion Criteria :will involve patients lacking informed consents, with severe cardiovascular, respiratory, central nervous system, or kidney dysfunction, communication or assessment impairments, and suspected severe neurocognitive impairment (MMSE score <24). patients with anticipated airway difficulties, alcohol or drug dependence, current sedative, antidepressant, or corticosteroid use, allergy to dexmedetomidine, lidocaine or other used anesthetics, baseline heart rate less than 50 beats per minute due to bradycardia, sick sinus syndrome, or second-degree or higher atrioventricular block without a pacemaker.

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Randomization will be achieved using a computer-generated random sequence, and group allocation will be concealed using opaque, sealed envelopes. Both patients and study staff, including those administering the interventions and assessing outcomes will be blinded to the group assignments. The tested syringes will be prepared by the responsible nurse in equal volumes of 50 ml. All data of the patients will be confidential with secret codes and private file for each patient, all given data will be used for the current medical research only.