Although colonoscopy is a mildly painful procedure, the pain and the procedure itself are distressful for most patients. This raises the attention for using different sedation regimens aiming at maintaining optimal sedation level with maintained airway and stable haemodynamics all through the procedure. The present study was scheduled to investigate the sedative efficacy of dexmedetomedine versus propofol-remifentanil for outpatient colonoscopy.

Eighty patients undergoing outpatient colonoscopy will be randomized into two equal groups. In Dexmedetomidine (DEX) group the patients will be administered a loading dose of i.v. dexmedetomidine 1 μg/kg over 10 min, followed by a continuous infusion of 0.2-1 μg/kg/h, titrated according to the sedation score, till the end of the procedure. In the PR group, propofol will be started by a loading dose of 0.5 mg/kg over 3-5 minutes then a maintenance infusion of 25-75 μg kg/min. Remifentanil infusion will be started at 1 μg kg over one minute then and 0.01-0.1 μg kg/min. If the patient complained of pain or discomfort, the infusion rates of dexmedetomidine (DEX group) or propofol-remifentanil (P-R group) will be increased. If the higher limit of the dose range of the study drugs reached, additional fentanyl 0.5 μg/kg i.v. boluses will be administered. Rescue medication consisting of propofol boluses of 0.5 mg/kg i.v. will be given if the previous protocol failed. Sedation score,haemodynamics, end-tidal carbon dioxide, oxygen saturation, total fentanyl, propofol bolus doses, patient and colonoscopist satisfaction and side effects will be recorded.

Inclusion Criteria:

• ASA I or II physical status
• 18-65 years
• Scheduled for elective colonoscopy

Exclusion Criteria:

• History of allergy to any of the study drugs
• Alcohol or drug abuse.
• Second and third-degree heart block.
• Morbid obesity.
• Pregnant and lactating women.
• Psychiatric disorders.
• Severe cardiac, respiratory, renal, and liver diseases

A blinded investigator that was not involved in the anaesthetic management of the patients, collected the intra-operative and postoperative data. The patients and colonoscopist were blinded to group allocation. For blinding purposes, two drug infusion pumps were used in every patient where the infusion pumps and i.v. connection lines were concealed to avoid identification.