Endoscopic retrograde cholangiopancreatography (ERCP) is an invasive longer endoscopic procedure. It is performed in remote locations under a continuum of anesthetic depth, ranging from conscious to deep sedation leading to general anesthesia.

Propofol sedation for (ERCP) procedures is the most popular current technique that has generated controversy in the medical field. Propofol can be safely administered because of its shorter half-life which results in a shorter recovery time than conventional sedation (opioid and/or benzodiazepine) that makes it widely used for sedation in many gastrointestinal procedures including ERCP. However, because of its narrow therapeutic window, the level of conscious sedation can easily go deeper from moderately deep sedation to near general anesthesia. Therefore, propofol as a sole agent can cause oversedation and apnea. Depth of sedation could be estimated better when target effect concentration of propofol is titrated by using bispectral index monitoring device(BIS).Targeting BIS within a specific range ensures additional safety during the procedure. Scores between 60-80 have been recommended for sedation. Propofol requirement can be reduced with addition of adjuvants (eg. Ketamine, Magnesium sulfate and Dexmedetomidine). Most adjuncts have analgesic properties with opioid and anesthetic sparing effects, without clinically significant respiratory depression.

Dexmedetomidine, is a selective alpha 2 agonist; it has sedative, amnestic, and analgesic properties. It is a useful addition to a propofol/remifentanil anesthetic combination as it reduced their requirements intraoperatively and can help supplement analgesia postoperatively. Its combination with propofol was proved to provide satisfactory anesthesia for upper gastrointestinal (GI)) endoscopy in obstructive sleep apnea patients .

Magnesium can also act as an adjuvant in analgesia due to its properties as calcium channel blocker and N-methyl-D-aspartate antagonists .It was suggested to be a near ideal intravenous (IV) adjunct to propofol/ remifentanil based total anesthesia in gynaecology patients .

Hypothesis of this study is that Magnesium sulfate can have a propofol sparing effect during ERCP procedures guided by BIS monitoring as efficient as dexmedetomidine but with less cost and complications together with more patient and doctor satisfaction in addition to better patient outcome.

After Theodor Bilharz Research Institute (TBRI) Ethics Committee approval, sixty patients scheduled for ERCP procedures will be informed about the study and written consents will be obtained.

Patients will be allocated into two groups, thirty patients each, Magnesium (M) and Dexmedetomidine (D). Group (M) will receive 40 mg.kg-1 of magnesium sulphate bolus followed by IV infusion of 10 mg.kg-1.h-1. Group (D) will receive dexmedetomidine bolus (1μg.kg-1) followed by infusion of 0.5μg.kg-1h-1 all through the procedure.

Randomization of the patients will be established by computer generated random number table utilizing sealed envelope technique.

On arrival to the ERCP suit, two IV cannulae will be inserted in both hands of each patient in both groups. One for isotonic saline infusion and propofol administration and the other will be preserved for the study drug administration. IV fluid will be started at a rate of 8-12 ml.kg-1.h-1 continued throughout the procedure. All patients will be premedicated with intravenous pantoprazole 40mg and ondansetron 8mg.

Routine monitoring of ECG, pulse oximetry, non-invasive blood pressure will be established before induction of sedation. BIS three electrodes sensor will be applied over the patient's forehead using fronto-temporal montage for the monitoring of level of sedation . The baseline variables will be recorded and documented as well as continuous monitoring and documentation every 5 min for the first 30 min and every 10 min till the end of procedure. Supplemental oxygen will be administered with nasal prongs at 3 l.min-1. The total duration of the procedure, defined as the time taken from insertion of the endoscope to its removal, will also be documented.

Each study drug will be loaded in 50 ml syringes (for both bolus and infusion) & labeled as "study drug bolus" and "study drug infusion". The identity of the constituted drug in the syringe is not revealed to the anesthetist handling the patients and the observer recording the post procedure variables. Depending upon the body weight, each patient will receive a bolus of the study drug, diluted up to 50 ml with saline (direct IV)followed by infusion of the same drug in another 50 ml using a syringe pump. Each bolus will be given and the rate of drug infusion will be adjusted by the anesthesia resident not involved in the study.

The study drugs IV infusions will be administered using injector pumps with unidentified screen to assure that the observer remains blinded.

For each patient, bolus dose of the each study drug will be administered slowly over 10 min, after mouth gag insertion and patient positioning (either lateral or prone position) followed by induction with propofol in a dose of 0.5-1.5 mgkg-1, targeting BIS between 60-70.Once the target BIS is attained, the infusion of the study drug is started with the pre-adjusted rate (discussed before) along with the propofol maintenance infusion starting at a rate of 3 mg/kg/hr to be adjusted to maintain a BIS value between 60-70.At the end of the procedure, propofol and study drug infusions will be stopped. BIS values will be allowed equilibrating above 80. Patients oropharynx will be thoroughly suctioned and patients will be turned supine with head up tilt (15 degrees), to allow for complete recovery with eye opening on command, ability to handle secretions, follow simple commands, hemodynamic stability, maintaining O2 saturation at room air >95% and attainment of BIS value >90 as end points

Inclusion Criteria:

• American Society of Anesthesiologists (ASA) I, II or III.
• Body mass index (BMI) ˂30
• Patients scheduled for ERCP procedures

Exclusion Criteria:

1. Obesity (BMI >30)
2. Evidence of hepatic encephalopathy, ascites.
3. Sever renal, endocrine and respiratory dysfunction.
4. Atrioventricular conductance disturbance.
5. Symptomatic bradycardia <35 bpm
6. Hemodynamically unstable patients on inotropic support.
7. Neurological disorders
8. Myasthenia gravis.
9. Hypo/Hyperkalemia (Potassium <3meq/l or>5.5meq/l) (risk of dysrhythmias).
10. Chronic treatment with calcium channel blockers or magnesium
11. Opioid or analgesic abuse
12. Allergy to Propofol/ egg or any other study drugs.
13. Pregnancy and lactation