Effect of Lidocaine Infusion Versus Dexmedemidine Infusion on the Neurocognitive Function of Elderly Patients Undergoing Endoscopic Retrograde Cholangiopancreatography(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.