 Total complications as recorded from the beginning of colonoscopy to hospital discharge Colonoscopy-related complications defined as any vasovagal, hypoxemic, bleeding or perforation event Total mortality defined as any lethal outcome from the beginning of colonoscopy to hospital discharge Patients will be followed until hospital discharge, an average of 10 days. Sample size calculation To be able to detect a 2-point difference in mean pain index with standard deviation of 3, with alpha0.05 and power0.80, the investigators calculated the required total sample size of 72 patients. 